Replace hidden flag with post state.

Store post state as text so Go owns the allowed values and future states such as locked remain representable without a database enum migration.

.env.example

@@ -14,6 +14,11 @@ SECURE_COOKIE=0
 # Comma-separated CIDRs of reverse proxies allowed to set X-Forwarded-For
 # (direct peer must match). Leave unset to ignore XFF and use RemoteAddr.
 # TRUSTED_PROXY_CIDRS=10.0.0.0/8,192.168.0.0/16
+# Resend (answer notifications). Leave RESEND_API_KEY unset to disable.
+# RESEND_API_KEY=re_xxxxxxxxx
+# RESEND_FROM=Ask a Plumber <notify@yourdomain.com>
+# Public site origin used in email links (required when Resend is enabled):
+# APP_BASE_URL=https://askaplumber.example
 # DigitalOcean Spaces (profile avatars). Leave unset to disable uploads.
 # SPACES_KEY=
 # SPACES_SECRET=

cmd/server/main.go

@@ -17,6 +17,7 @@ import (
 
 	"plumber"
 	"plumber/internal/blob"
+	"plumber/internal/mail"
 	"plumber/internal/store"
 	"plumber/internal/web"
 )
@@ -29,7 +30,11 @@ func main() {
 	defer sessions.Close()
 
 	uploader := blob.FromEnv()
-	handler := newHandler(db, sessions, uploader)
+	notifier, err := mail.FromEnv()
+	if err != nil {
+		log.Fatalf("mail: %v", err)
+	}
+	handler := newHandler(db, sessions, uploader, notifier)
 	run(&http.Server{
 		Addr:              listenAddr(),
 		Handler:           handler,
@@ -53,12 +58,13 @@ func openDB() (*sql.DB, *store.SessionStore) {
 	return db, sessions
 }
 
-func newHandler(db *sql.DB, sessions *store.SessionStore, uploader blob.Uploader) http.Handler {
+func newHandler(db *sql.DB, sessions *store.SessionStore, uploader blob.Uploader, notifier mail.Notifier) http.Handler {
 	srv, err := web.New(store.NewPostgres(db), sessions.Store(), plumber.TemplateFS, plumber.StaticFS, web.Config{
 		AdminSetupSecret: strings.TrimSpace(os.Getenv("ADMIN_SETUP_SECRET")),
 		SecureCookie:     secureCookieFromEnv(),
 		TrustedProxies:   parseTrustedProxies(os.Getenv("TRUSTED_PROXY_CIDRS")),
 		Blob:             uploader,
+		Mail:             notifier,
 	})
 	if err != nil {
 		log.Fatalf("server: %v", err)

db/queries/posts.sql

@@ -0,0 +1,125 @@
+-- name: CreatePost :exec
+INSERT INTO posts (
+  id, parent_id, author_id, title, body, city, post_date, post_state, created_at, updated_at
+)
+VALUES (
+  sqlc.arg(id),
+  sqlc.arg(parent_id),
+  sqlc.arg(author_id),
+  sqlc.arg(title),
+  sqlc.arg(body),
+  sqlc.arg(city),
+  sqlc.arg(post_date),
+  sqlc.arg(post_state),
+  sqlc.arg(created_at),
+  sqlc.arg(updated_at)
+);
+
+-- name: GetPost :one
+SELECT
+  p.id, p.parent_id, p.author_id, u.name AS author_name, u.role AS author_role,
+  p.title, p.body, p.city, p.post_date, p.post_state, p.created_at, p.updated_at
+FROM posts p
+JOIN users u ON u.id = p.author_id
+WHERE p.id = sqlc.arg(id);
+
+-- name: ListPostThread :many
+WITH RECURSIVE thread AS (
+  SELECT p.*
+  FROM posts p
+  WHERE p.id = sqlc.arg(root_id) AND p.parent_id IS NULL
+
+  UNION ALL
+
+  SELECT child.*
+  FROM posts child
+  JOIN thread parent ON child.parent_id = parent.id
+)
+SELECT
+  thread.id, thread.parent_id, thread.author_id,
+  u.name AS author_name, u.role AS author_role,
+  thread.title, thread.body, thread.city, thread.post_date,
+  thread.post_state, thread.created_at, thread.updated_at
+FROM thread
+JOIN users u ON u.id = thread.author_id
+ORDER BY thread.created_at, thread.id;
+
+-- name: UpdatePost :execrows
+UPDATE posts
+SET
+  body = sqlc.arg(body),
+  updated_at = sqlc.arg(updated_at)
+WHERE id = sqlc.arg(id);
+
+-- name: ListRootPosts :many
+WITH RECURSIVE roots AS (
+  SELECT p.*
+  FROM posts p
+  WHERE p.parent_id IS NULL
+    AND p.post_date = sqlc.arg(post_date)
+    AND p.post_state <> sqlc.arg(hidden_state)
+),
+thread AS (
+  SELECT roots.id AS root_id, child.id AS post_id, child.author_id
+  FROM roots
+  JOIN posts child ON child.parent_id = roots.id
+
+  UNION ALL
+
+  SELECT thread.root_id, child.id, child.author_id
+  FROM thread
+  JOIN posts child ON child.parent_id = thread.post_id
+),
+answered AS (
+  SELECT DISTINCT thread.root_id
+  FROM thread
+  JOIN users u ON u.id = thread.author_id
+  WHERE u.role = 'admin'
+),
+scores AS (
+  SELECT votes.post_id, SUM(votes.value)::bigint AS score
+  FROM roots
+  JOIN post_votes votes ON votes.post_id = roots.id
+  GROUP BY votes.post_id
+)
+SELECT
+  roots.id, roots.parent_id, roots.author_id,
+  u.name AS author_name, u.role AS author_role,
+  roots.title, roots.body, roots.city, roots.post_date,
+  roots.post_state, roots.created_at, roots.updated_at,
+  COALESCE(scores.score, 0)::bigint AS score,
+  (answered.root_id IS NOT NULL)::bool AS answered,
+  COALESCE(viewer_vote.value, 0)::bigint AS user_vote
+FROM roots
+JOIN users u ON u.id = roots.author_id
+LEFT JOIN scores ON scores.post_id = roots.id
+LEFT JOIN answered ON answered.root_id = roots.id
+LEFT JOIN post_votes viewer_vote
+  ON viewer_vote.user_id = sqlc.arg(viewer_id)
+  AND viewer_vote.post_id = roots.id
+ORDER BY score DESC, roots.created_at, roots.id
+LIMIT sqlc.arg(row_limit);
+
+-- name: PostIsVisibleRoot :one
+SELECT EXISTS(
+  SELECT 1
+  FROM posts
+  WHERE id = sqlc.arg(id)
+    AND parent_id IS NULL
+    AND post_state <> sqlc.arg(hidden_state)
+)::bool;
+
+-- name: DeletePostVote :exec
+DELETE FROM post_votes
+WHERE user_id = sqlc.arg(user_id)
+  AND post_id = sqlc.arg(post_id);
+
+-- name: UpsertPostVoteOnVisibleRoot :execrows
+INSERT INTO post_votes (user_id, post_id, value)
+SELECT sqlc.arg(user_id), sqlc.arg(post_id), sqlc.arg(value)
+FROM posts p
+WHERE p.id = sqlc.arg(post_id)
+  AND p.parent_id IS NULL
+  AND p.post_state <> sqlc.arg(hidden_state)
+ON CONFLICT (user_id, post_id) DO UPDATE
+SET value = excluded.value;

db/queries/users.sql

@@ -1,24 +1,25 @@
 -- name: CreateUser :exec
-INSERT INTO users (id, username, name, password_hash, role, avatar_url, state, created_at)
-VALUES ($1, $2, $3, $4, $5, '', '', $6);
+INSERT INTO users (id, username, name, password_hash, role, email, avatar_url, state, created_at)
+VALUES ($1, $2, $3, $4, $5, $6, '', '', $7);
 
 -- name: GetUserByID :one
-SELECT id, username, name, role, avatar_url, state, created_at
+SELECT id, username, name, role, email, avatar_url, state, created_at
 FROM users
 WHERE id = $1;
 
 -- name: GetUserByUsername :one
-SELECT id, username, name, role, avatar_url, state, created_at, password_hash
+SELECT id, username, name, role, email, avatar_url, state, created_at, password_hash
 FROM users
 WHERE username = $1;
 
 -- name: ListUsers :many
-SELECT id, username, name, role, avatar_url, state, created_at
+SELECT id, username, name, role, email, avatar_url, state, created_at
 FROM users
 WHERE (
   sqlc.arg(search) = ''
   OR username ILIKE '%' || sqlc.arg(search) || '%'
   OR name ILIKE '%' || sqlc.arg(search) || '%'
+  OR email ILIKE '%' || sqlc.arg(search) || '%'
 )
 AND (
   sqlc.arg(cursor_created) = ''
@@ -43,12 +44,12 @@ UPDATE users
 SET role = $1
 WHERE id = $2;
 
--- name: UpdateUserState :exec
+-- name: UpdateUserProfile :exec
 UPDATE users
-SET state = $1
-WHERE id = $2;
-
--- name: UpdateUserStateAndAvatar :exec
-UPDATE users
-SET state = $1, avatar_url = $2
+SET state = $1, email = $2
 WHERE id = $3;
+
+-- name: UpdateUserProfileAndAvatar :exec
+UPDATE users
+SET state = $1, email = $2, avatar_url = $3
+WHERE id = $4;

go.mod

@@ -28,6 +28,7 @@ require (
 	github.com/jackc/pgpassfile v1.0.0 // indirect
 	github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 // indirect
 	github.com/jackc/puddle/v2 v2.2.2 // indirect
+	github.com/resend/resend-go/v3 v3.16.0 // indirect
 	golang.org/x/sync v0.22.0 // indirect
 	golang.org/x/text v0.41.0 // indirect
 )

go.sum

@@ -43,6 +43,8 @@ github.com/joho/godotenv v1.5.1 h1:7eLL/+HRGLY0ldzfGMeQkb7vMd0as4CfYvUVzLqw0N0=
 github.com/joho/godotenv v1.5.1/go.mod h1:f4LDr5Voq0i2e/R5DDNOoa2zzDfwtkZa6DnEwAbqwq4=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/resend/resend-go/v3 v3.16.0 h1:t0Z/7k2sxnJGw8SjsCM9O8qkq3YRRHzTxWQNjhF2KhE=
+github.com/resend/resend-go/v3 v3.16.0/go.mod h1:iI7VA0NoGjWvsNii5iNC5Dy0llsI3HncXPejhniYzwE=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=

internal/mail/mail.go

@@ -0,0 +1,189 @@
+package mail
+
+import (
+	"context"
+	_ "embed"
+	"fmt"
+	"html"
+	"os"
+	"strings"
+
+	"github.com/resend/resend-go/v3"
+)
+
+//go:embed mark.png
+var markPNG []byte
+
+// QuestionAnswered is the payload for notifying a question author of a reply.
+type QuestionAnswered struct {
+	ToEmail       string
+	ToName        string
+	QuestionID    string
+	QuestionTitle string
+	AnswerBody    string
+}
+
+// Notifier sends transactional email about answered questions.
+type Notifier interface {
+	NotifyQuestionAnswered(ctx context.Context, msg QuestionAnswered) error
+}
+
+// Nop is a no-op Notifier used when Resend is not configured.
+type Nop struct{}
+
+func (Nop) NotifyQuestionAnswered(context.Context, QuestionAnswered) error { return nil }
+
+// Resend sends via the Resend HTTP API.
+type Resend struct {
+	client  *resend.Client
+	from    string
+	baseURL string
+}
+
+// FromEnv builds a Notifier from RESEND_* and APP_BASE_URL.
+// Returns Nop when RESEND_API_KEY is unset.
+func FromEnv() (Notifier, error) {
+	key := strings.TrimSpace(os.Getenv("RESEND_API_KEY"))
+	if key == "" {
+		return Nop{}, nil
+	}
+	from := strings.TrimSpace(os.Getenv("RESEND_FROM"))
+	base := strings.TrimRight(strings.TrimSpace(os.Getenv("APP_BASE_URL")), "/")
+	if from == "" {
+		return nil, fmt.Errorf("RESEND_FROM is required when RESEND_API_KEY is set")
+	}
+	if base == "" {
+		return nil, fmt.Errorf("APP_BASE_URL is required when RESEND_API_KEY is set")
+	}
+	return &Resend{
+		client:  resend.NewClient(key),
+		from:    from,
+		baseURL: base,
+	}, nil
+}
+
+func (r *Resend) NotifyQuestionAnswered(ctx context.Context, msg QuestionAnswered) error {
+	if r == nil || r.client == nil {
+		return nil
+	}
+	to := strings.TrimSpace(msg.ToEmail)
+	if to == "" {
+		return nil
+	}
+	text, htmlBody := questionAnsweredContent(r.baseURL, msg)
+	params := &resend.SendEmailRequest{
+		From:    r.from,
+		To:      []string{to},
+		Subject: "Your question was answered",
+		Text:    text,
+		Html:    htmlBody,
+		Attachments: []*resend.Attachment{{
+			Content:     markPNG,
+			Filename:    "ask-a-plumber-first.png",
+			ContentType: "image/png",
+			ContentId:   "answer-notification-mark",
+		}},
+	}
+	opts := &resend.SendEmailOptions{
+		IdempotencyKey: "answer-notify:" + msg.QuestionID,
+	}
+	_, err := r.client.Emails.SendWithOptions(ctx, params, opts)
+	return err
+}
+
+func questionAnsweredContent(baseURL string, msg QuestionAnswered) (string, string) {
+	link := strings.TrimRight(baseURL, "/") + "/questions/" + msg.QuestionID
+	title := strings.TrimSpace(msg.QuestionTitle)
+	if title == "" {
+		title = "your question"
+	}
+	text := fmt.Sprintf(
+		"Hi%s,\n\nYour question %q has an answer from a plumber:\n\n%s\n\nView it here:\n%s\n",
+		greetingName(msg.ToName),
+		title,
+		msg.AnswerBody,
+		link,
+	)
+	htmlBody := strings.NewReplacer(
+		"{{PREHEADER}}", html.EscapeString("A plumber answered "+title+"."),
+		"{{GREETING}}", html.EscapeString(greetingName(msg.ToName)),
+		"{{TITLE}}", html.EscapeString(title),
+		"{{ANSWER}}", html.EscapeString(msg.AnswerBody),
+		"{{LINK}}", html.EscapeString(link),
+		"{{MARK}}", "cid:answer-notification-mark",
+	).Replace(questionAnsweredHTML)
+	return text, htmlBody
+}
+
+const questionAnsweredHTML = `<!doctype html>
+<html lang="en">
+<head>
+  <meta charset="utf-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1">
+  <meta name="color-scheme" content="dark">
+  <meta name="supported-color-schemes" content="dark">
+  <title>Your question was answered</title>
+</head>
+<body style="margin:0;padding:0;background:#161719;color:#ecebe7;font-family:Arial,'Helvetica Neue',sans-serif;">
+  <div style="display:none;max-height:0;overflow:hidden;opacity:0;color:transparent;">{{PREHEADER}}</div>
+  <table role="presentation" width="100%" cellspacing="0" cellpadding="0" border="0" style="width:100%;background:#161719;">
+    <tr>
+      <td align="center" style="padding:32px 16px;">
+        <table role="presentation" width="560" cellspacing="0" cellpadding="0" border="0" style="width:100%;max-width:560px;background:#1e2023;border:1px solid #2e3136;border-top:3px solid #e96a26;border-radius:3px;">
+          <tr>
+            <td style="padding:24px 28px 20px;border-bottom:1px solid #2e3136;">
+              <table role="presentation" cellspacing="0" cellpadding="0" border="0">
+                <tr>
+                  <td style="padding-right:12px;vertical-align:middle;">
+                    <img src="{{MARK}}" width="32" height="32" alt="" style="display:block;width:32px;height:32px;border:0;">
+                  </td>
+                  <td style="vertical-align:middle;">
+                    <div style="color:#ecebe7;font-size:14px;font-weight:700;line-height:1.2;letter-spacing:1px;text-transform:uppercase;">Ask a Plumber First</div>
+                    <div style="margin-top:4px;color:#8d9096;font-family:'Courier New',monospace;font-size:10px;line-height:1.2;letter-spacing:1.4px;text-transform:uppercase;">Bay Area · Shop Dispatch</div>
+                  </td>
+                </tr>
+              </table>
+            </td>
+          </tr>
+          <tr>
+            <td style="padding:30px 28px 32px;">
+              <div style="margin:0 0 10px;color:#e96a26;font-family:'Courier New',monospace;font-size:11px;font-weight:700;line-height:1.4;letter-spacing:1.8px;text-transform:uppercase;">Shop response</div>
+              <h1 style="margin:0;color:#ecebe7;font-size:28px;font-weight:600;line-height:1.2;letter-spacing:-0.4px;">Your question has an answer.</h1>
+              <p style="margin:18px 0 0;color:#b8babf;font-size:16px;line-height:1.6;">Hi{{GREETING}}, a plumber replied to:</p>
+              <p style="margin:8px 0 0;color:#ecebe7;font-size:17px;font-weight:600;line-height:1.45;">“{{TITLE}}”</p>
+              <table role="presentation" width="100%" cellspacing="0" cellpadding="0" border="0" style="width:100%;margin-top:24px;background:#161719;border:1px solid #2e3136;border-radius:3px;">
+                <tr>
+                  <td style="padding:20px 18px;">
+                    <div style="margin:0 0 10px;color:#8d9096;font-family:'Courier New',monospace;font-size:10px;font-weight:700;line-height:1.4;letter-spacing:1.5px;text-transform:uppercase;">The answer</div>
+                    <div style="margin:0;color:#ecebe7;font-size:16px;line-height:1.65;white-space:pre-wrap;">{{ANSWER}}</div>
+                  </td>
+                </tr>
+              </table>
+              <table role="presentation" cellspacing="0" cellpadding="0" border="0" style="margin-top:26px;">
+                <tr>
+                  <td bgcolor="#e96a26" style="border-radius:3px;">
+                    <a href="{{LINK}}" style="display:inline-block;padding:13px 18px;color:#161719;font-family:'Courier New',monospace;font-size:12px;font-weight:700;line-height:1;text-decoration:none;letter-spacing:0.8px;text-transform:uppercase;">View the answer&nbsp;&rarr;</a>
+                  </td>
+                </tr>
+              </table>
+            </td>
+          </tr>
+          <tr>
+            <td style="padding:18px 28px;border-top:1px solid #2e3136;color:#8d9096;font-family:'Courier New',monospace;font-size:10px;line-height:1.6;letter-spacing:0.4px;">
+              You received this because you asked a question on Ask a Plumber First.
+            </td>
+          </tr>
+        </table>
+      </td>
+    </tr>
+  </table>
+</body>
+</html>`
+
+func greetingName(name string) string {
+	name = strings.TrimSpace(name)
+	if name == "" {
+		return ""
+	}
+	return " " + name
+}

internal/mail/mail_test.go

@@ -0,0 +1,76 @@
+package mail
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+)
+
+func TestEmbeddedMarkIsPNG(t *testing.T) {
+	t.Parallel()
+
+	if !bytes.HasPrefix(markPNG, []byte("\x89PNG\r\n\x1a\n")) {
+		t.Fatal("embedded mark is not PNG data")
+	}
+}
+
+func TestQuestionAnsweredContent(t *testing.T) {
+	t.Parallel()
+
+	text, htmlBody := questionAnsweredContent("https://plumber.example/", QuestionAnswered{
+		ToName:        `<Sam & Pat>`,
+		QuestionID:    "question-123",
+		QuestionTitle: `<b>Leaky sink</b>`,
+		AnswerBody:    "Replace the cartridge.\nThen test the handle. <script>alert('x')</script>",
+	})
+
+	for _, want := range []string{
+		"Ask a Plumber First",
+		"Shop response",
+		"cid:answer-notification-mark",
+		"https://plumber.example/questions/question-123",
+		"white-space:pre-wrap",
+		"&lt;Sam &amp; Pat&gt;",
+		"&lt;b&gt;Leaky sink&lt;/b&gt;",
+		"&lt;script&gt;alert(&#39;x&#39;)&lt;/script&gt;",
+	} {
+		if !strings.Contains(htmlBody, want) {
+			t.Errorf("HTML missing %q", want)
+		}
+	}
+	for _, unsafe := range []string{
+		"<Sam & Pat>",
+		"<b>Leaky sink</b>",
+		"<script>alert('x')</script>",
+	} {
+		if strings.Contains(htmlBody, unsafe) {
+			t.Errorf("HTML contains unescaped content %q", unsafe)
+		}
+	}
+	if strings.Contains(htmlBody, "{{") {
+		t.Error("HTML contains an unresolved template token")
+	}
+	for _, want := range []string{
+		`Hi <Sam & Pat>,`,
+		`Your question "<b>Leaky sink</b>"`,
+		"Replace the cartridge.\nThen test the handle.",
+		"https://plumber.example/questions/question-123",
+	} {
+		if !strings.Contains(text, want) {
+			t.Errorf("text missing %q", want)
+		}
+	}
+}
+
+func TestQuestionAnsweredContentUsesFallbackTitle(t *testing.T) {
+	t.Parallel()
+
+	text, htmlBody := questionAnsweredContent("https://plumber.example", QuestionAnswered{})
+	if !strings.Contains(text, `"your question"`) {
+		t.Errorf("text missing fallback title")
+	}
+	if !strings.Contains(htmlBody, "a plumber replied to:</p>") ||
+		!strings.Contains(htmlBody, "“your question”") {
+		t.Errorf("HTML missing fallback title")
+	}
+}

internal/mail/recording.go

@@ -0,0 +1,34 @@
+package mail
+
+import (
+	"context"
+	"sync"
+)
+
+// Recording is a test Notifier that records calls.
+type Recording struct {
+	mu   sync.Mutex
+	Msgs []QuestionAnswered
+}
+
+func (r *Recording) NotifyQuestionAnswered(_ context.Context, msg QuestionAnswered) error {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	r.Msgs = append(r.Msgs, msg)
+	return nil
+}
+
+func (r *Recording) Len() int {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	return len(r.Msgs)
+}
+
+// Snapshot returns a copy of recorded messages.
+func (r *Recording) Snapshot() []QuestionAnswered {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	out := make([]QuestionAnswered, len(r.Msgs))
+	copy(out, r.Msgs)
+	return out
+}

internal/store/email.go

@@ -0,0 +1,52 @@
+package store
+
+import (
+	"fmt"
+	"net/mail"
+	"strings"
+	"unicode/utf8"
+)
+
+const (
+	minEmailLen = 3
+	maxEmailLen = 254
+)
+
+// NormalizeEmail trims and lowercases an address for storage/comparison.
+func NormalizeEmail(s string) string {
+	return strings.ToLower(strings.TrimSpace(s))
+}
+
+// ValidateEmail returns a normalized address or an error message suitable for UI.
+func ValidateEmail(raw string) (normalized string, errMsg string) {
+	normalized = NormalizeEmail(raw)
+	if normalized == "" {
+		return "", "Email is required."
+	}
+	n := utf8.RuneCountInString(normalized)
+	if n < minEmailLen || len(normalized) > maxEmailLen {
+		return "", "Enter a valid email address."
+	}
+	addr, err := mail.ParseAddress(normalized)
+	if err != nil || addr.Address != normalized {
+		return "", "Enter a valid email address."
+	}
+	at := strings.LastIndex(normalized, "@")
+	if at < 1 || at == len(normalized)-1 {
+		return "", "Enter a valid email address."
+	}
+	domain := normalized[at+1:]
+	if !strings.Contains(domain, ".") || strings.HasPrefix(domain, ".") || strings.HasSuffix(domain, ".") {
+		return "", "Enter a valid email address."
+	}
+	return normalized, ""
+}
+
+// MustValidateEmail is like ValidateEmail but returns a Go error.
+func MustValidateEmail(raw string) (string, error) {
+	n, msg := ValidateEmail(raw)
+	if msg != "" {
+		return "", fmt.Errorf("%s", msg)
+	}
+	return n, nil
+}

internal/store/email_test.go

@@ -0,0 +1,21 @@
+package store
+
+import "testing"
+
+func TestValidateEmail(t *testing.T) {
+	cases := []struct {
+		in, want, err string
+	}{
+		{"", "", "Email is required."},
+		{"  Alice@Example.COM ", "alice@example.com", ""},
+		{"not-an-email", "", "Enter a valid email address."},
+		{"a@b", "", "Enter a valid email address."},
+		{"ok@example.com", "ok@example.com", ""},
+	}
+	for _, tc := range cases {
+		got, msg := ValidateEmail(tc.in)
+		if got != tc.want || msg != tc.err {
+			t.Fatalf("%q: got (%q, %q) want (%q, %q)", tc.in, got, msg, tc.want, tc.err)
+		}
+	}
+}

internal/store/memory.go

@@ -22,6 +22,8 @@ type Memory struct {
 	questions map[string]*RankedQuestion // id -> question
 	answers   map[string]*Answer         // questionID -> answer
 	votes     map[string]map[string]int  // questionID -> userID -> value
+	posts     map[string]*Post           // id -> post
+	postVotes map[string]map[string]int  // postID -> userID -> value
 }
 
 // NewMemory returns an empty Memory store.
@@ -32,6 +34,8 @@ func NewMemory() *Memory {
 		questions: map[string]*RankedQuestion{},
 		answers:   map[string]*Answer{},
 		votes:     map[string]map[string]int{},
+		posts:     map[string]*Post{},
+		postVotes: map[string]map[string]int{},
 	}
 }
 
@@ -42,9 +46,17 @@ func (m *Memory) CreateUser(_ context.Context, u *User) error {
 		return fmt.Errorf("invalid role")
 	}
 	u.Username = NormalizeUsername(u.Username)
+	u.Email = NormalizeEmail(u.Email)
 	if _, ok := m.byName[u.Username]; ok {
 		return ErrDuplicateUsername
 	}
+	if u.Email != "" {
+		for _, existing := range m.users {
+			if existing.Email == u.Email {
+				return ErrDuplicateEmail
+			}
+		}
+	}
 	if u.ID == "" {
 		u.ID = uuid.NewString()
 	}
@@ -179,11 +191,21 @@ func (m *Memory) SaveUserProfile(_ context.Context, u *User) error {
 	if !ok {
 		return sql.ErrNoRows
 	}
+	email := NormalizeEmail(u.Email)
+	if email != "" {
+		for id, existing := range m.users {
+			if id != u.ID && existing.Email == email {
+				return ErrDuplicateEmail
+			}
+		}
+	}
 	cur.State = strings.TrimSpace(u.State)
+	cur.Email = email
 	if u.AvatarURL != "" {
 		cur.AvatarURL = u.AvatarURL
 	}
 	u.State = cur.State
+	u.Email = cur.Email
 	u.AvatarURL = cur.AvatarURL
 	return nil
 }
@@ -354,6 +376,186 @@ func (m *Memory) UpsertAnswer(_ context.Context, a *Answer) error {
 	return nil
 }
 
+func (m *Memory) CreatePost(_ context.Context, post *Post) error {
+	if post == nil {
+		return fmt.Errorf("%w: post is nil", ErrInvalidPost)
+	}
+	if err := preparePost(post); err != nil {
+		return err
+	}
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	if _, ok := m.users[post.AuthorID]; !ok {
+		return fmt.Errorf("%w: unknown author", ErrInvalidPost)
+	}
+	if _, exists := m.posts[post.ID]; exists {
+		return fmt.Errorf("%w: duplicate id", ErrInvalidPost)
+	}
+	if post.ParentID != nil {
+		if _, ok := m.posts[*post.ParentID]; !ok {
+			return fmt.Errorf("%w: unknown parent", ErrInvalidPost)
+		}
+	}
+	cp := clonePost(post)
+	cp.db = nil
+	m.posts[cp.ID] = cp
+	*post = *clonePost(cp)
+	return nil
+}
+
+func (m *Memory) GetPost(_ context.Context, id string) (*Post, error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	post, ok := m.posts[id]
+	if !ok {
+		return nil, sql.ErrNoRows
+	}
+	return clonePostWithAuthor(post, m.users), nil
+}
+
+func (m *Memory) GetPostThread(_ context.Context, rootID string) (*Post, error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	root, ok := m.posts[rootID]
+	if !ok || root.ParentID != nil {
+		return nil, sql.ErrNoRows
+	}
+	inThread := map[string]bool{rootID: true}
+	for changed := true; changed; {
+		changed = false
+		for id, post := range m.posts {
+			if inThread[id] || post.ParentID == nil || !inThread[*post.ParentID] {
+				continue
+			}
+			inThread[id] = true
+			changed = true
+		}
+	}
+	posts := make([]Post, 0, len(inThread))
+	for id := range inThread {
+		posts = append(posts, *clonePostWithAuthor(m.posts[id], m.users))
+	}
+	return buildPostTree(posts, rootID)
+}
+
+func (m *Memory) UpdatePost(_ context.Context, post *Post) error {
+	if post == nil {
+		return fmt.Errorf("%w: post is nil", ErrInvalidPost)
+	}
+	body := strings.TrimSpace(post.Body)
+	if body == "" {
+		return fmt.Errorf("%w: body is required", ErrInvalidPost)
+	}
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	existing, ok := m.posts[post.ID]
+	if !ok {
+		return sql.ErrNoRows
+	}
+	existing.Body = body
+	existing.UpdatedAt = time.Now().UTC().Format(time.RFC3339Nano)
+	*post = *clonePostWithAuthor(existing, m.users)
+	return nil
+}
+
+func (m *Memory) ListRootPosts(_ context.Context, postDate, viewerID string) ([]Post, error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	posts := make([]Post, 0)
+	for _, post := range m.posts {
+		if post.ParentID != nil || post.PostDate != postDate || post.PostState == PostStateHidden {
+			continue
+		}
+		cp := clonePostWithAuthor(post, m.users)
+		for _, value := range m.postVotes[post.ID] {
+			cp.Score += value
+		}
+		cp.UserVote = m.postVotes[post.ID][viewerID]
+		cp.Answered = m.threadContainsAdminReply(post.ID)
+		posts = append(posts, *cp)
+	}
+	sort.Slice(posts, func(i, j int) bool {
+		if posts[i].Score != posts[j].Score {
+			return posts[i].Score > posts[j].Score
+		}
+		if posts[i].CreatedAt != posts[j].CreatedAt {
+			return posts[i].CreatedAt < posts[j].CreatedAt
+		}
+		return posts[i].ID < posts[j].ID
+	})
+	if len(posts) > HuntListLimit {
+		posts = posts[:HuntListLimit]
+	}
+	return posts, nil
+}
+
+func (m *Memory) VotePost(_ context.Context, userID, postID string, value int) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	if value != 1 && value != -1 && value != 0 {
+		return fmt.Errorf("invalid vote")
+	}
+	post, ok := m.posts[postID]
+	if !ok || post.ParentID != nil || post.PostState == PostStateHidden {
+		return ErrPostNotVotable
+	}
+	if m.postVotes[postID] == nil {
+		m.postVotes[postID] = map[string]int{}
+	}
+	if value == 0 {
+		delete(m.postVotes[postID], userID)
+		return nil
+	}
+	m.postVotes[postID][userID] = value
+	return nil
+}
+
+func (m *Memory) threadContainsAdminReply(rootID string) bool {
+	for id, post := range m.posts {
+		if id == rootID || !m.postIsDescendantOf(post, rootID) {
+			continue
+		}
+		if author := m.users[post.AuthorID]; author != nil && author.Role == RoleAdmin {
+			return true
+		}
+	}
+	return false
+}
+
+func (m *Memory) postIsDescendantOf(post *Post, rootID string) bool {
+	seen := map[string]bool{}
+	for post != nil && post.ParentID != nil {
+		if *post.ParentID == rootID {
+			return true
+		}
+		if seen[*post.ParentID] {
+			return false
+		}
+		seen[*post.ParentID] = true
+		post = m.posts[*post.ParentID]
+	}
+	return false
+}
+
+func clonePost(post *Post) *Post {
+	cp := *post
+	if post.ParentID != nil {
+		parentID := *post.ParentID
+		cp.ParentID = &parentID
+	}
+	cp.Replies = nil
+	return &cp
+}
+
+func clonePostWithAuthor(post *Post, users map[string]*User) *Post {
+	cp := clonePost(post)
+	if author := users[post.AuthorID]; author != nil {
+		cp.AuthorName = author.Name
+		cp.AuthorRole = author.Role
+	}
+	return cp
+}
+
 func (m *Memory) Vote(_ context.Context, userID, questionID string, value int) error {
 	m.mu.Lock()
 	defer m.mu.Unlock()

internal/store/migrate.go

@@ -21,6 +21,241 @@ func migrateUserProfileColumns(ctx context.Context, exec execContext) error {
 	return nil
 }
 
+// migrateUserEmail adds email and a partial unique index on lower(email).
+func migrateUserEmail(ctx context.Context, exec execContext) error {
+	if _, err := exec.ExecContext(ctx, `ALTER TABLE users ADD COLUMN IF NOT EXISTS email TEXT NOT NULL DEFAULT ''`); err != nil {
+		return fmt.Errorf("add column email: %w", err)
+	}
+	if _, err := exec.ExecContext(ctx, `
+CREATE UNIQUE INDEX IF NOT EXISTS users_email_lower_uidx
+  ON users (lower(email))
+  WHERE email <> ''`); err != nil {
+		return fmt.Errorf("users_email_lower_uidx: %w", err)
+	}
+	return nil
+}
+
+// migratePosts creates the unified post model and snapshots legacy content.
+// Legacy tables remain in place until the application cutover is complete.
+func migratePosts(ctx context.Context, exec execContext) error {
+	steps := []struct {
+		name string
+		sql  string
+		args []any
+	}{
+		{name: "create posts", sql: `
+CREATE TABLE IF NOT EXISTS posts (
+  id TEXT PRIMARY KEY,
+  parent_id TEXT REFERENCES posts(id) ON DELETE CASCADE,
+  author_id TEXT NOT NULL REFERENCES users(id),
+  title TEXT NOT NULL DEFAULT '',
+  body TEXT NOT NULL,
+  city TEXT NOT NULL DEFAULT '',
+  post_date TEXT NOT NULL DEFAULT '',
+  post_state TEXT NOT NULL,
+  created_at TEXT NOT NULL,
+  updated_at TEXT NOT NULL,
+  CONSTRAINT posts_shape_check CHECK (
+    (parent_id IS NULL AND title <> '' AND post_date <> '')
+    OR
+    (parent_id IS NOT NULL AND title = '' AND city = '' AND post_date = '')
+  )
+)`},
+		{name: "index post replies", sql: `
+CREATE INDEX IF NOT EXISTS idx_posts_parent_created
+  ON posts(parent_id, created_at, id)`},
+		{name: "index root posts", sql: `
+CREATE INDEX IF NOT EXISTS idx_posts_root_date
+  ON posts(post_date, post_state)
+  WHERE parent_id IS NULL`},
+		{name: "create post votes", sql: `
+CREATE TABLE IF NOT EXISTS post_votes (
+  user_id TEXT NOT NULL REFERENCES users(id),
+  post_id TEXT NOT NULL REFERENCES posts(id) ON DELETE CASCADE,
+  value INTEGER NOT NULL CHECK (value IN (-1, 1)),
+  PRIMARY KEY (user_id, post_id)
+)`},
+		{name: "copy questions", sql: `
+INSERT INTO posts (
+  id, parent_id, author_id, title, body, city, post_date, post_state, created_at, updated_at
+)
+SELECT
+  id, NULL, author_id, title, body, city, hunt_date,
+  CASE WHEN hidden = 0 THEN $1 ELSE $2 END,
+  created_at, created_at
+FROM questions
+ON CONFLICT (id) DO NOTHING`, args: []any{string(PostStateVisible), string(PostStateHidden)}},
+		{name: "copy answers", sql: `
+INSERT INTO posts (
+  id, parent_id, author_id, title, body, city, post_date, post_state, created_at, updated_at
+)
+SELECT
+  'answer:' || question_id, question_id, author_id, '', body, '', '',
+  $1, created_at, updated_at
+FROM answers
+ON CONFLICT (id) DO NOTHING`, args: []any{string(PostStateVisible)}},
+		{name: "copy votes", sql: `
+INSERT INTO post_votes (user_id, post_id, value)
+SELECT user_id, question_id, value
+FROM votes
+ON CONFLICT (user_id, post_id) DO NOTHING`},
+	}
+	for _, step := range steps {
+		if _, err := exec.ExecContext(ctx, step.sql, step.args...); err != nil {
+			return fmt.Errorf("%s: %w", step.name, err)
+		}
+	}
+	return nil
+}
+
+func migratePostVoteIndex(ctx context.Context, exec execContext) error {
+	if _, err := exec.ExecContext(ctx, `
+CREATE INDEX IF NOT EXISTS idx_post_votes_post_id
+  ON post_votes(post_id)`); err != nil {
+		return fmt.Errorf("idx_post_votes_post_id: %w", err)
+	}
+	return nil
+}
+
+func migratePostDate(ctx context.Context, exec execContext) error {
+	steps := []struct {
+		name string
+		sql  string
+	}{
+		{"rename post date", `
+DO $migration$
+BEGIN
+  IF EXISTS (
+    SELECT 1
+    FROM information_schema.columns
+    WHERE table_schema = current_schema()
+      AND table_name = 'posts'
+      AND column_name = 'hunt_date'
+  ) AND NOT EXISTS (
+    SELECT 1
+    FROM information_schema.columns
+    WHERE table_schema = current_schema()
+      AND table_name = 'posts'
+      AND column_name = 'post_date'
+  ) THEN
+    ALTER TABLE posts RENAME COLUMN hunt_date TO post_date;
+  END IF;
+END
+$migration$`},
+		{"drop legacy root date index", `
+DROP INDEX IF EXISTS idx_posts_root_hunt`},
+		{"create root date index", `
+DO $migration$
+BEGIN
+  IF EXISTS (
+    SELECT 1
+    FROM information_schema.columns
+    WHERE table_schema = current_schema()
+      AND table_name = 'posts'
+      AND column_name = 'post_state'
+  ) THEN
+    CREATE INDEX IF NOT EXISTS idx_posts_root_date
+      ON posts(post_date, post_state)
+      WHERE parent_id IS NULL;
+  ELSE
+    CREATE INDEX IF NOT EXISTS idx_posts_root_date
+      ON posts(post_date, hidden)
+      WHERE parent_id IS NULL;
+  END IF;
+END
+$migration$`},
+	}
+	for _, step := range steps {
+		if _, err := exec.ExecContext(ctx, step.sql); err != nil {
+			return fmt.Errorf("%s: %w", step.name, err)
+		}
+	}
+	return nil
+}
+
+func migratePostState(ctx context.Context, exec execContext) error {
+	if _, err := exec.ExecContext(ctx, `
+ALTER TABLE posts
+  ADD COLUMN IF NOT EXISTS post_state TEXT`); err != nil {
+		return fmt.Errorf("add post state: %w", err)
+	}
+	hasHidden, err := migrationColumnExists(ctx, exec, "posts", "hidden")
+	if err != nil {
+		return fmt.Errorf("check hidden column: %w", err)
+	}
+	if hasHidden {
+		if _, err := exec.ExecContext(ctx, `
+UPDATE posts
+SET post_state = CASE
+  WHEN hidden = 0 THEN $1
+  ELSE $2
+END`, string(PostStateVisible), string(PostStateHidden)); err != nil {
+			return fmt.Errorf("copy hidden state: %w", err)
+		}
+	}
+
+	steps := []struct {
+		name string
+		sql  string
+	}{
+		{"drop root date index", `
+DROP INDEX IF EXISTS idx_posts_root_date`},
+		{"drop legacy post shape constraint", `
+ALTER TABLE posts DROP CONSTRAINT IF EXISTS posts_check`},
+		{"drop post shape constraint", `
+ALTER TABLE posts DROP CONSTRAINT IF EXISTS posts_shape_check`},
+		{"drop hidden", `
+ALTER TABLE posts DROP COLUMN IF EXISTS hidden`},
+		{"require post state", `
+ALTER TABLE posts ALTER COLUMN post_state SET NOT NULL`},
+		{"create post shape constraint", `
+ALTER TABLE posts
+  ADD CONSTRAINT posts_shape_check CHECK (
+    (parent_id IS NULL AND title <> '' AND post_date <> '')
+    OR
+    (parent_id IS NOT NULL AND title = '' AND city = '' AND post_date = '')
+  )`},
+		{"create root date index", `
+CREATE INDEX idx_posts_root_date
+  ON posts(post_date, post_state)
+  WHERE parent_id IS NULL`},
+	}
+	for _, step := range steps {
+		if _, err := exec.ExecContext(ctx, step.sql); err != nil {
+			return fmt.Errorf("%s: %w", step.name, err)
+		}
+	}
+	return nil
+}
+
+func migrationColumnExists(
+	ctx context.Context,
+	exec execContext,
+	tableName string,
+	columnName string,
+) (bool, error) {
+	rows, err := exec.QueryContext(ctx, `
+SELECT EXISTS (
+  SELECT 1
+  FROM information_schema.columns
+  WHERE table_schema = current_schema()
+    AND table_name = $1
+    AND column_name = $2
+)`, tableName, columnName)
+	if err != nil {
+		return false, err
+	}
+	defer rows.Close()
+	if !rows.Next() {
+		return false, rows.Err()
+	}
+	var exists bool
+	if err := rows.Scan(&exists); err != nil {
+		return false, err
+	}
+	return exists, rows.Err()
+}
+
 type execContext interface {
 	ExecContext(ctx context.Context, query string, args ...any) (sql.Result, error)
 	QueryContext(ctx context.Context, query string, args ...any) (*sql.Rows, error)
@@ -66,6 +301,11 @@ CREATE TABLE IF NOT EXISTS schema_migrations (
 			return applySchema(ctx, exec, schemaSQL)
 		}},
 		{"002_user_profile_columns", migrateUserProfileColumns},
+		{"003_user_email", migrateUserEmail},
+		{"004_posts", migratePosts},
+		{"005_post_vote_post_id_index", migratePostVoteIndex},
+		{"006_post_date", migratePostDate},
+		{"007_post_state", migratePostState},
 	}
 	for _, m := range migrations {
 		if applied[m.version] {

internal/store/migrate_posts_test.go

@@ -0,0 +1,438 @@
+package store
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+	"os"
+	"strings"
+	"testing"
+
+	"github.com/google/uuid"
+
+	"plumber/internal/store/sqlc"
+)
+
+func TestMigratePostsCopiesLegacyData(t *testing.T) {
+	rawURL := strings.TrimSpace(os.Getenv("TEST_DATABASE_URL"))
+	if rawURL == "" {
+		t.Skip("TEST_DATABASE_URL is not set")
+	}
+	dsn, err := postgresDSN(rawURL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	db, err := sql.Open("pgx", dsn)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	ctx := context.Background()
+	conn, err := db.Conn(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer conn.Close()
+
+	schemaName := "test_posts_" + strings.ReplaceAll(uuid.NewString(), "-", "")
+	if _, err := conn.ExecContext(ctx, "CREATE SCHEMA "+schemaName); err != nil {
+		t.Fatal(err)
+	}
+	defer func() {
+		_, _ = conn.ExecContext(context.Background(), "SET search_path TO public")
+		_, _ = conn.ExecContext(context.Background(), "DROP SCHEMA "+schemaName+" CASCADE")
+	}()
+	if _, err := conn.ExecContext(ctx, "SET search_path TO "+schemaName); err != nil {
+		t.Fatal(err)
+	}
+
+	legacySchema := `
+CREATE TABLE users (
+  id TEXT PRIMARY KEY,
+  name TEXT NOT NULL,
+  role TEXT NOT NULL
+);
+CREATE TABLE questions (
+  id TEXT PRIMARY KEY,
+  author_id TEXT NOT NULL REFERENCES users(id),
+  title TEXT NOT NULL,
+  body TEXT NOT NULL,
+  city TEXT NOT NULL DEFAULT '',
+  hunt_date TEXT NOT NULL,
+  hidden INTEGER NOT NULL DEFAULT 0,
+  created_at TEXT NOT NULL
+);
+CREATE TABLE answers (
+  question_id TEXT PRIMARY KEY REFERENCES questions(id) ON DELETE CASCADE,
+  author_id TEXT NOT NULL REFERENCES users(id),
+  body TEXT NOT NULL,
+  created_at TEXT NOT NULL,
+  updated_at TEXT NOT NULL
+);
+CREATE TABLE votes (
+  user_id TEXT NOT NULL REFERENCES users(id),
+  question_id TEXT NOT NULL REFERENCES questions(id) ON DELETE CASCADE,
+  value INTEGER NOT NULL CHECK (value IN (-1, 1)),
+  PRIMARY KEY (user_id, question_id)
+);`
+	if err := applySchema(ctx, conn, legacySchema); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := conn.ExecContext(ctx, `
+INSERT INTO users (id, name, role)
+VALUES ('homeowner', 'Home Owner', 'user'), ('plumber', 'The Plumber', 'admin');
+INSERT INTO questions (id, author_id, title, body, city, hunt_date, hidden, created_at)
+VALUES ('question-1', 'homeowner', 'Leaky sink', 'It drips.', 'Oakland', '2026-08-26', 0, '2026-08-26T08:00:00Z');
+INSERT INTO answers (question_id, author_id, body, created_at, updated_at)
+VALUES ('question-1', 'plumber', 'Replace the cartridge.', '2026-08-26T09:00:00Z', '2026-08-26T09:05:00Z');
+INSERT INTO votes (user_id, question_id, value)
+VALUES ('homeowner', 'question-1', 1);`); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := migratePosts(ctx, conn); err != nil {
+		t.Fatal(err)
+	}
+	if err := migratePosts(ctx, conn); err != nil {
+		t.Fatalf("migration is not idempotent: %v", err)
+	}
+	if err := migratePostVoteIndex(ctx, conn); err != nil {
+		t.Fatal(err)
+	}
+	if err := migratePostVoteIndex(ctx, conn); err != nil {
+		t.Fatalf("post vote index migration is not idempotent: %v", err)
+	}
+
+	var postCount, voteCount, legacyQuestionCount, legacyAnswerCount int
+	if err := conn.QueryRowContext(ctx, "SELECT count(*) FROM posts").Scan(&postCount); err != nil {
+		t.Fatal(err)
+	}
+	if err := conn.QueryRowContext(ctx, "SELECT count(*) FROM post_votes").Scan(&voteCount); err != nil {
+		t.Fatal(err)
+	}
+	if err := conn.QueryRowContext(ctx, "SELECT count(*) FROM questions").Scan(&legacyQuestionCount); err != nil {
+		t.Fatal(err)
+	}
+	if err := conn.QueryRowContext(ctx, "SELECT count(*) FROM answers").Scan(&legacyAnswerCount); err != nil {
+		t.Fatal(err)
+	}
+	if postCount != 2 || voteCount != 1 || legacyQuestionCount != 1 || legacyAnswerCount != 1 {
+		t.Fatalf(
+			"counts posts=%d votes=%d legacy questions=%d answers=%d",
+			postCount,
+			voteCount,
+			legacyQuestionCount,
+			legacyAnswerCount,
+		)
+	}
+	var postVoteIndexCount int
+	if err := conn.QueryRowContext(ctx, `
+SELECT count(*)
+FROM pg_indexes
+WHERE schemaname = current_schema()
+  AND tablename = 'post_votes'
+  AND indexname = 'idx_post_votes_post_id'`).Scan(&postVoteIndexCount); err != nil {
+		t.Fatal(err)
+	}
+	if postVoteIndexCount != 1 {
+		t.Fatalf("post vote index count = %d, want 1", postVoteIndexCount)
+	}
+	if _, err := conn.ExecContext(ctx, `
+INSERT INTO post_votes (user_id, post_id, value)
+VALUES ('homeowner', 'question-1', -1)`); err == nil {
+		t.Fatal("duplicate user/post vote unexpectedly succeeded")
+	}
+
+	var rootParent sql.NullString
+	var rootAuthor, title, rootBody, city, postDate, rootState, rootCreated, rootUpdated string
+	if err := conn.QueryRowContext(ctx, `
+SELECT parent_id, author_id, title, body, city, post_date, post_state, created_at, updated_at
+FROM posts
+WHERE id = 'question-1'`).Scan(
+		&rootParent,
+		&rootAuthor,
+		&title,
+		&rootBody,
+		&city,
+		&postDate,
+		&rootState,
+		&rootCreated,
+		&rootUpdated,
+	); err != nil {
+		t.Fatal(err)
+	}
+	if rootParent.Valid ||
+		rootAuthor != "homeowner" ||
+		title != "Leaky sink" ||
+		rootBody != "It drips." ||
+		city != "Oakland" ||
+		postDate != "2026-08-26" ||
+		rootState != "visible" ||
+		rootCreated != "2026-08-26T08:00:00Z" ||
+		rootUpdated != rootCreated {
+		t.Fatalf("unexpected root post")
+	}
+
+	var replyParent, replyAuthor, replyBody, replyState, replyCreated, replyUpdated string
+	if err := conn.QueryRowContext(ctx, `
+SELECT parent_id, author_id, body, post_state, created_at, updated_at
+FROM posts
+WHERE id = 'answer:question-1'`).Scan(
+		&replyParent,
+		&replyAuthor,
+		&replyBody,
+		&replyState,
+		&replyCreated,
+		&replyUpdated,
+	); err != nil {
+		t.Fatal(err)
+	}
+	if replyParent != "question-1" ||
+		replyAuthor != "plumber" ||
+		replyBody != "Replace the cartridge." ||
+		replyState != "visible" ||
+		replyCreated != "2026-08-26T09:00:00Z" ||
+		replyUpdated != "2026-08-26T09:05:00Z" {
+		t.Fatalf("unexpected reply post")
+	}
+
+	var voteValue int
+	if err := conn.QueryRowContext(ctx, `
+SELECT value FROM post_votes
+WHERE user_id = 'homeowner' AND post_id = 'question-1'`).Scan(&voteValue); err != nil {
+		t.Fatal(err)
+	}
+	if voteValue != 1 {
+		t.Fatalf("vote value = %d, want 1", voteValue)
+	}
+
+	if _, err := conn.ExecContext(ctx, `
+INSERT INTO posts (
+  id, parent_id, author_id, title, body, city, post_date, post_state, created_at, updated_at
+) VALUES (
+  'invalid-reply', 'question-1', 'homeowner', 'Replies cannot have titles', 'Body', '', '',
+  'visible', 'now', 'now'
+)`); err == nil {
+		t.Fatal("reply with root-only title unexpectedly succeeded")
+	}
+
+	queries := sqlc.New(conn)
+	if err := queries.CreatePost(ctx, sqlc.CreatePostParams{
+		ID:        "follow-up",
+		ParentID:  sql.NullString{String: "answer:question-1", Valid: true},
+		AuthorID:  "homeowner",
+		Body:      "It is still dripping.",
+		PostState: string(PostStateVisible),
+		CreatedAt: "2026-08-26T10:00:00Z",
+		UpdatedAt: "2026-08-26T10:00:00Z",
+	}); err != nil {
+		t.Fatal(err)
+	}
+	thread, err := queries.ListPostThread(ctx, "question-1")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(thread) != 3 ||
+		thread[0].ID != "question-1" ||
+		thread[1].ID != "answer:question-1" ||
+		thread[2].ID != "follow-up" {
+		t.Fatalf("recursive thread = %+v", thread)
+	}
+	nonRootThread, err := queries.ListPostThread(ctx, "answer:question-1")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(nonRootThread) != 0 {
+		t.Fatalf("non-root thread lookup returned %+v", nonRootThread)
+	}
+	if n, err := queries.UpdatePost(ctx, sqlc.UpdatePostParams{
+		ID:        "follow-up",
+		Body:      "The drip continues.",
+		UpdatedAt: "2026-08-26T10:05:00Z",
+	}); err != nil || n != 1 {
+		t.Fatalf("update rows=%d error=%v", n, err)
+	}
+	if n, err := queries.UpsertPostVoteOnVisibleRoot(ctx, sqlc.UpsertPostVoteOnVisibleRootParams{
+		UserID:      "plumber",
+		PostID:      "question-1",
+		Value:       1,
+		HiddenState: string(PostStateHidden),
+	}); err != nil || n != 1 {
+		t.Fatalf("vote rows=%d error=%v", n, err)
+	}
+	roots, err := queries.ListRootPosts(ctx, sqlc.ListRootPostsParams{
+		ViewerID:    "plumber",
+		RowLimit:    100,
+		PostDate:    "2026-08-26",
+		HiddenState: string(PostStateHidden),
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(roots) != 1 ||
+		roots[0].Score != 2 ||
+		!roots[0].Answered ||
+		roots[0].UserVote != 1 {
+		t.Fatalf("root annotations = %+v", roots)
+	}
+
+	if _, err := conn.ExecContext(ctx, `
+DROP INDEX idx_posts_root_date;
+ALTER TABLE posts RENAME COLUMN post_date TO hunt_date;
+CREATE INDEX idx_posts_root_hunt
+  ON posts(hunt_date, post_state)
+  WHERE parent_id IS NULL;`); err != nil {
+		t.Fatal(err)
+	}
+	if err := migratePostDate(ctx, conn); err != nil {
+		t.Fatal(err)
+	}
+	if err := migratePostDate(ctx, conn); err != nil {
+		t.Fatalf("post date migration is not idempotent: %v", err)
+	}
+
+	var postDateColumnCount, huntDateColumnCount, rootDateIndexCount, legacyIndexCount int
+	if err := conn.QueryRowContext(ctx, `
+SELECT
+  count(*) FILTER (WHERE column_name = 'post_date'),
+  count(*) FILTER (WHERE column_name = 'hunt_date')
+FROM information_schema.columns
+WHERE table_schema = current_schema()
+  AND table_name = 'posts'`).Scan(&postDateColumnCount, &huntDateColumnCount); err != nil {
+		t.Fatal(err)
+	}
+	if err := conn.QueryRowContext(ctx, `
+SELECT
+  count(*) FILTER (WHERE indexname = 'idx_posts_root_date'),
+  count(*) FILTER (WHERE indexname = 'idx_posts_root_hunt')
+FROM pg_indexes
+WHERE schemaname = current_schema()
+  AND tablename = 'posts'`).Scan(&rootDateIndexCount, &legacyIndexCount); err != nil {
+		t.Fatal(err)
+	}
+	var migratedPostDate string
+	if err := conn.QueryRowContext(ctx, `
+SELECT post_date FROM posts WHERE id = 'question-1'`).Scan(&migratedPostDate); err != nil {
+		t.Fatal(err)
+	}
+	if postDateColumnCount != 1 ||
+		huntDateColumnCount != 0 ||
+		rootDateIndexCount != 1 ||
+		legacyIndexCount != 0 ||
+		migratedPostDate != "2026-08-26" {
+		t.Fatalf(
+			"post date migration columns=%d legacy_columns=%d indexes=%d legacy_indexes=%d date=%q",
+			postDateColumnCount,
+			huntDateColumnCount,
+			rootDateIndexCount,
+			legacyIndexCount,
+			migratedPostDate,
+		)
+	}
+
+	if _, err := conn.ExecContext(ctx, `
+DROP INDEX idx_posts_root_date;
+ALTER TABLE posts DROP CONSTRAINT posts_shape_check;
+ALTER TABLE posts ADD COLUMN hidden INTEGER NOT NULL DEFAULT 0;
+UPDATE posts SET hidden = CASE WHEN id = 'question-1' THEN 1 ELSE 0 END;
+ALTER TABLE posts DROP COLUMN post_state;
+ALTER TABLE posts ADD CONSTRAINT posts_check CHECK (
+  (parent_id IS NULL AND title <> '' AND post_date <> '')
+  OR
+  (parent_id IS NOT NULL AND title = '' AND city = '' AND post_date = '' AND hidden = 0)
+);
+CREATE INDEX idx_posts_root_date
+  ON posts(post_date, hidden)
+  WHERE parent_id IS NULL;`); err != nil {
+		t.Fatal(err)
+	}
+	if err := migratePostState(ctx, conn); err != nil {
+		t.Fatal(err)
+	}
+	if err := migratePostState(ctx, conn); err != nil {
+		t.Fatalf("post state migration is not idempotent: %v", err)
+	}
+
+	var postStateColumnCount, hiddenColumnCount int
+	if err := conn.QueryRowContext(ctx, `
+SELECT
+  count(*) FILTER (WHERE column_name = 'post_state'),
+  count(*) FILTER (WHERE column_name = 'hidden')
+FROM information_schema.columns
+WHERE table_schema = current_schema()
+  AND table_name = 'posts'`).Scan(&postStateColumnCount, &hiddenColumnCount); err != nil {
+		t.Fatal(err)
+	}
+	var hiddenState, replyStateAfterMigration string
+	if err := conn.QueryRowContext(ctx, `
+SELECT post_state FROM posts WHERE id = 'question-1'`).Scan(&hiddenState); err != nil {
+		t.Fatal(err)
+	}
+	if err := conn.QueryRowContext(ctx, `
+SELECT post_state FROM posts WHERE id = 'answer:question-1'`).Scan(&replyStateAfterMigration); err != nil {
+		t.Fatal(err)
+	}
+	var postStateDataType string
+	if err := conn.QueryRowContext(ctx, `
+SELECT data_type
+FROM information_schema.columns
+WHERE table_schema = current_schema()
+  AND table_name = 'posts'
+  AND column_name = 'post_state'`).Scan(&postStateDataType); err != nil {
+		t.Fatal(err)
+	}
+	var stateIndexCount int
+	if err := conn.QueryRowContext(ctx, `
+SELECT count(*)
+FROM pg_indexes
+WHERE schemaname = current_schema()
+  AND tablename = 'posts'
+  AND indexname = 'idx_posts_root_date'
+  AND indexdef LIKE '%(post_date, post_state)%'`).Scan(&stateIndexCount); err != nil {
+		t.Fatal(err)
+	}
+	if postStateColumnCount != 1 ||
+		hiddenColumnCount != 0 ||
+		hiddenState != "hidden" ||
+		replyStateAfterMigration != "visible" ||
+		postStateDataType != "text" ||
+		stateIndexCount != 1 {
+		t.Fatalf(
+			"post state migration columns=%d hidden_columns=%d root=%q reply=%q type=%q indexes=%d",
+			postStateColumnCount,
+			hiddenColumnCount,
+			hiddenState,
+			replyStateAfterMigration,
+			postStateDataType,
+			stateIndexCount,
+		)
+	}
+}
+
+func TestMigratePostsReportsStep(t *testing.T) {
+	t.Parallel()
+
+	exec := &failingMigrationExec{failAt: 5}
+	err := migratePosts(context.Background(), exec)
+	if err == nil || !strings.Contains(err.Error(), "copy questions") {
+		t.Fatalf("error = %v, want copy questions context", err)
+	}
+}
+
+type failingMigrationExec struct {
+	calls  int
+	failAt int
+}
+
+func (f *failingMigrationExec) ExecContext(context.Context, string, ...any) (sql.Result, error) {
+	f.calls++
+	if f.calls == f.failAt {
+		return nil, fmt.Errorf("boom")
+	}
+	return nil, nil
+}
+
+func (*failingMigrationExec) QueryContext(context.Context, string, ...any) (*sql.Rows, error) {
+	return nil, fmt.Errorf("not implemented")
+}

internal/store/post.go

@@ -0,0 +1,372 @@
+package store
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+	"fmt"
+	"sort"
+	"strings"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5/pgconn"
+
+	"plumber/internal/pacific"
+	"plumber/internal/store/sqlc"
+)
+
+var (
+	ErrInvalidPost    = errors.New("invalid post")
+	ErrPostNotVotable = errors.New("post not votable")
+)
+
+type PostState string
+
+const (
+	PostStateVisible PostState = "visible"
+	PostStateHidden  PostState = "hidden"
+	PostStateLocked  PostState = "locked"
+)
+
+// Post is either a root question (ParentID nil) or a reply to another post.
+type Post struct {
+	ID         string
+	ParentID   *string
+	AuthorID   string
+	AuthorName string
+	AuthorRole Role
+	Title      string
+	Body       string
+	City       string
+	PostDate   string
+	PostState  PostState
+	CreatedAt  string
+	UpdatedAt  string
+	Score      int
+	Answered   bool
+	UserVote   int
+	Replies    []*Post
+	db         *sql.DB
+}
+
+// NewPost returns a post bound to db.
+func NewPost(db *sql.DB) *Post {
+	return &Post{db: db}
+}
+
+// Create inserts a root post or reply according to ParentID.
+func (p *Post) Create(ctx context.Context) error {
+	if p == nil || p.db == nil {
+		return fmt.Errorf("post: no database")
+	}
+	if err := preparePost(p); err != nil {
+		return err
+	}
+	err := sqlc.New(p.db).CreatePost(ctx, sqlc.CreatePostParams{
+		ID:        p.ID,
+		ParentID:  nullableParentID(p.ParentID),
+		AuthorID:  p.AuthorID,
+		Title:     p.Title,
+		Body:      p.Body,
+		City:      p.City,
+		PostDate:  p.PostDate,
+		PostState: string(p.PostState),
+		CreatedAt: p.CreatedAt,
+		UpdatedAt: p.UpdatedAt,
+	})
+	return mapPostCreateError(err)
+}
+
+// Update changes only the post body and update timestamp.
+func (p *Post) Update(ctx context.Context) error {
+	if p == nil || p.db == nil {
+		return fmt.Errorf("post: no database")
+	}
+	p.Body = strings.TrimSpace(p.Body)
+	if p.Body == "" {
+		return fmt.Errorf("%w: body is required", ErrInvalidPost)
+	}
+	p.UpdatedAt = time.Now().UTC().Format(time.RFC3339Nano)
+	n, err := sqlc.New(p.db).UpdatePost(ctx, sqlc.UpdatePostParams{
+		ID:        p.ID,
+		Body:      p.Body,
+		UpdatedAt: p.UpdatedAt,
+	})
+	if err != nil {
+		return err
+	}
+	if n == 0 {
+		return sql.ErrNoRows
+	}
+	return nil
+}
+
+func preparePost(p *Post) error {
+	p.ID = strings.TrimSpace(p.ID)
+	p.AuthorID = strings.TrimSpace(p.AuthorID)
+	p.Title = strings.TrimSpace(p.Title)
+	p.Body = strings.TrimSpace(p.Body)
+	p.City = strings.TrimSpace(p.City)
+	p.PostDate = strings.TrimSpace(p.PostDate)
+	if p.PostState == "" {
+		p.PostState = PostStateVisible
+	}
+	switch p.PostState {
+	case PostStateVisible, PostStateHidden, PostStateLocked:
+	default:
+		return fmt.Errorf("%w: invalid post state", ErrInvalidPost)
+	}
+	if p.AuthorID == "" {
+		return fmt.Errorf("%w: author is required", ErrInvalidPost)
+	}
+	if p.Body == "" {
+		return fmt.Errorf("%w: body is required", ErrInvalidPost)
+	}
+	if p.ParentID == nil {
+		if p.Title == "" {
+			return fmt.Errorf("%w: root title is required", ErrInvalidPost)
+		}
+		if p.PostDate == "" {
+			p.PostDate = pacific.Today()
+		}
+	} else {
+		parentID := strings.TrimSpace(*p.ParentID)
+		if parentID == "" {
+			return fmt.Errorf("%w: parent is required", ErrInvalidPost)
+		}
+		p.ParentID = &parentID
+		if p.Title != "" || p.City != "" || p.PostDate != "" || p.PostState != PostStateVisible {
+			return fmt.Errorf("%w: reply contains root-only fields", ErrInvalidPost)
+		}
+	}
+	if p.ID == "" {
+		p.ID = uuid.NewString()
+	}
+	now := time.Now().UTC().Format(time.RFC3339Nano)
+	if p.CreatedAt == "" {
+		p.CreatedAt = now
+	}
+	if p.UpdatedAt == "" {
+		p.UpdatedAt = p.CreatedAt
+	}
+	return nil
+}
+
+func nullableParentID(parentID *string) sql.NullString {
+	if parentID == nil {
+		return sql.NullString{}
+	}
+	return sql.NullString{String: *parentID, Valid: true}
+}
+
+func parentIDFromNull(parentID sql.NullString) *string {
+	if !parentID.Valid {
+		return nil
+	}
+	id := parentID.String
+	return &id
+}
+
+func mapPostCreateError(err error) error {
+	if err == nil {
+		return nil
+	}
+	var pgErr *pgconn.PgError
+	if errors.As(err, &pgErr) {
+		switch pgErr.Code {
+		case "23503", "23505", "23514":
+			return fmt.Errorf("%w: %v", ErrInvalidPost, err)
+		}
+	}
+	return err
+}
+
+func postFromValues(
+	db *sql.DB,
+	id string,
+	parentID sql.NullString,
+	authorID, authorName, authorRole, title, body, city, postDate string,
+	postState string,
+	createdAt, updatedAt string,
+) Post {
+	return Post{
+		ID:         id,
+		ParentID:   parentIDFromNull(parentID),
+		AuthorID:   authorID,
+		AuthorName: authorName,
+		AuthorRole: Role(authorRole),
+		Title:      title,
+		Body:       body,
+		City:       city,
+		PostDate:   postDate,
+		PostState:  PostState(postState),
+		CreatedAt:  createdAt,
+		UpdatedAt:  updatedAt,
+		db:         db,
+	}
+}
+
+// GetPost returns one post without loading its replies.
+func GetPost(ctx context.Context, db *sql.DB, id string) (*Post, error) {
+	r, err := sqlc.New(db).GetPost(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+	p := postFromValues(
+		db,
+		r.ID,
+		r.ParentID,
+		r.AuthorID,
+		r.AuthorName,
+		r.AuthorRole,
+		r.Title,
+		r.Body,
+		r.City,
+		r.PostDate,
+		r.PostState,
+		r.CreatedAt,
+		r.UpdatedAt,
+	)
+	return &p, nil
+}
+
+// GetPostThread returns a root post with all descendants nested under Replies.
+func GetPostThread(ctx context.Context, db *sql.DB, rootID string) (*Post, error) {
+	rows, err := sqlc.New(db).ListPostThread(ctx, rootID)
+	if err != nil {
+		return nil, err
+	}
+	posts := make([]Post, 0, len(rows))
+	for _, r := range rows {
+		posts = append(posts, postFromValues(
+			db,
+			r.ID,
+			r.ParentID,
+			r.AuthorID,
+			r.AuthorName,
+			r.AuthorRole,
+			r.Title,
+			r.Body,
+			r.City,
+			r.PostDate,
+			r.PostState,
+			r.CreatedAt,
+			r.UpdatedAt,
+		))
+	}
+	return buildPostTree(posts, rootID)
+}
+
+func buildPostTree(posts []Post, rootID string) (*Post, error) {
+	byID := make(map[string]*Post, len(posts))
+	for i := range posts {
+		posts[i].Replies = nil
+		byID[posts[i].ID] = &posts[i]
+	}
+	root, ok := byID[rootID]
+	if !ok || root.ParentID != nil {
+		return nil, sql.ErrNoRows
+	}
+	for i := range posts {
+		post := &posts[i]
+		if post.ID == rootID {
+			continue
+		}
+		if post.ParentID == nil {
+			return nil, fmt.Errorf("post %s is not in thread %s", post.ID, rootID)
+		}
+		parent, ok := byID[*post.ParentID]
+		if !ok {
+			return nil, fmt.Errorf("post %s has missing parent %s", post.ID, *post.ParentID)
+		}
+		parent.Replies = append(parent.Replies, post)
+	}
+	var sortReplies func(*Post)
+	sortReplies = func(post *Post) {
+		sort.Slice(post.Replies, func(i, j int) bool {
+			if post.Replies[i].CreatedAt != post.Replies[j].CreatedAt {
+				return post.Replies[i].CreatedAt < post.Replies[j].CreatedAt
+			}
+			return post.Replies[i].ID < post.Replies[j].ID
+		})
+		for _, reply := range post.Replies {
+			sortReplies(reply)
+		}
+	}
+	sortReplies(root)
+	return root, nil
+}
+
+// ListRootPosts returns visible root posts for a post date.
+func ListRootPosts(ctx context.Context, db *sql.DB, postDate, viewerID string) ([]Post, error) {
+	rows, err := sqlc.New(db).ListRootPosts(ctx, sqlc.ListRootPostsParams{
+		ViewerID:    viewerID,
+		RowLimit:    HuntListLimit,
+		PostDate:    postDate,
+		HiddenState: string(PostStateHidden),
+	})
+	if err != nil {
+		return nil, err
+	}
+	posts := make([]Post, 0, len(rows))
+	for _, r := range rows {
+		post := postFromValues(
+			db,
+			r.ID,
+			r.ParentID,
+			r.AuthorID,
+			r.AuthorName,
+			r.AuthorRole,
+			r.Title,
+			r.Body,
+			r.City,
+			r.PostDate,
+			r.PostState,
+			r.CreatedAt,
+			r.UpdatedAt,
+		)
+		post.Score = int(r.Score)
+		post.Answered = r.Answered
+		post.UserVote = int(r.UserVote)
+		posts = append(posts, post)
+	}
+	return posts, nil
+}
+
+// SetPostVote sets value to 1, -1, or 0 on a visible root post.
+func SetPostVote(ctx context.Context, db *sql.DB, userID, postID string, value int) error {
+	if value != 1 && value != -1 && value != 0 {
+		return fmt.Errorf("invalid vote")
+	}
+	q := sqlc.New(db)
+	if value == 0 {
+		visible, err := q.PostIsVisibleRoot(ctx, sqlc.PostIsVisibleRootParams{
+			ID:          postID,
+			HiddenState: string(PostStateHidden),
+		})
+		if err != nil {
+			return err
+		}
+		if !visible {
+			return ErrPostNotVotable
+		}
+		return q.DeletePostVote(ctx, sqlc.DeletePostVoteParams{
+			UserID: userID,
+			PostID: postID,
+		})
+	}
+	n, err := q.UpsertPostVoteOnVisibleRoot(ctx, sqlc.UpsertPostVoteOnVisibleRootParams{
+		UserID:      userID,
+		PostID:      postID,
+		Value:       int32(value),
+		HiddenState: string(PostStateHidden),
+	})
+	if err != nil {
+		return err
+	}
+	if n == 0 {
+		return ErrPostNotVotable
+	}
+	return nil
+}

internal/store/post_test.go

@@ -0,0 +1,252 @@
+package store
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+	"testing"
+
+	"github.com/jackc/pgx/v5/pgconn"
+)
+
+func TestMapPostCreateError(t *testing.T) {
+	t.Parallel()
+
+	for _, code := range []string{"23503", "23505", "23514"} {
+		err := mapPostCreateError(&pgconn.PgError{Code: code})
+		if !errors.Is(err, ErrInvalidPost) {
+			t.Errorf("code %s error = %v, want ErrInvalidPost", code, err)
+		}
+	}
+	original := &pgconn.PgError{Code: "08006"}
+	if err := mapPostCreateError(original); !errors.Is(err, original) {
+		t.Errorf("unexpected database error was replaced: %v", err)
+	}
+}
+
+func TestMemoryPostLifecycle(t *testing.T) {
+	t.Parallel()
+
+	ctx := context.Background()
+	mem := NewMemory()
+	homeowner := &User{Username: "homeowner", PasswordHash: "hash", Role: RoleUser}
+	plumber := &User{Username: "plumber", PasswordHash: "hash", Role: RoleAdmin}
+	voter := &User{Username: "voter", PasswordHash: "hash", Role: RoleUser}
+	for _, user := range []*User{homeowner, plumber, voter} {
+		if err := mem.CreateUser(ctx, user); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	root := &Post{
+		ID:        "root",
+		AuthorID:  homeowner.ID,
+		Title:     "Leaky sink",
+		Body:      "It drips.",
+		City:      "Oakland",
+		PostDate:  "2026-08-26",
+		CreatedAt: "2026-08-26T08:00:00Z",
+	}
+	if err := mem.CreatePost(ctx, root); err != nil {
+		t.Fatal(err)
+	}
+	if root.PostState != PostStateVisible {
+		t.Fatalf("default post state = %q, want visible", root.PostState)
+	}
+
+	rootID := root.ID
+	later := &Post{
+		ID:        "later",
+		ParentID:  &rootID,
+		AuthorID:  plumber.ID,
+		Body:      "Is it a single-handle faucet?",
+		CreatedAt: "2026-08-26T09:00:00Z",
+	}
+	earlier := &Post{
+		ID:        "earlier",
+		ParentID:  &rootID,
+		AuthorID:  plumber.ID,
+		Body:      "Can you share the model number?",
+		CreatedAt: "2026-08-26T08:30:00Z",
+	}
+	if err := mem.CreatePost(ctx, later); err != nil {
+		t.Fatal(err)
+	}
+	if err := mem.CreatePost(ctx, earlier); err != nil {
+		t.Fatal(err)
+	}
+
+	laterID := later.ID
+	nested := &Post{
+		ID:        "nested",
+		ParentID:  &laterID,
+		AuthorID:  homeowner.ID,
+		Body:      "Yes, it is.",
+		CreatedAt: "2026-08-26T09:30:00Z",
+	}
+	if err := mem.CreatePost(ctx, nested); err != nil {
+		t.Fatal(err)
+	}
+
+	thread, err := mem.GetPostThread(ctx, root.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if thread.AuthorName != homeowner.Name || thread.AuthorRole != RoleUser {
+		t.Fatalf("root author = %q %q", thread.AuthorName, thread.AuthorRole)
+	}
+	if len(thread.Replies) != 2 ||
+		thread.Replies[0].ID != earlier.ID ||
+		thread.Replies[1].ID != later.ID {
+		t.Fatalf("root replies are not oldest-first: %+v", thread.Replies)
+	}
+	if len(thread.Replies[1].Replies) != 1 || thread.Replies[1].Replies[0].ID != nested.ID {
+		t.Fatalf("nested reply missing: %+v", thread.Replies[1].Replies)
+	}
+
+	otherParent := earlier.ID
+	nested.ParentID = &otherParent
+	nested.AuthorID = voter.ID
+	nested.Body = "Yes—one handle."
+	if err := mem.UpdatePost(ctx, nested); err != nil {
+		t.Fatal(err)
+	}
+	saved, err := mem.GetPost(ctx, nested.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if saved.ParentID == nil || *saved.ParentID != later.ID {
+		t.Fatalf("update changed parent to %+v", saved.ParentID)
+	}
+	if saved.AuthorID != homeowner.ID {
+		t.Fatalf("update changed author to %q", saved.AuthorID)
+	}
+	if saved.Body != "Yes—one handle." || saved.UpdatedAt == saved.CreatedAt {
+		t.Fatalf("body update not applied: %+v", saved)
+	}
+
+	if err := mem.VotePost(ctx, voter.ID, root.ID, 1); err != nil {
+		t.Fatal(err)
+	}
+	roots, err := mem.ListRootPosts(ctx, root.PostDate, voter.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(roots) != 1 || roots[0].ID != root.ID {
+		t.Fatalf("root list = %+v", roots)
+	}
+	if roots[0].Score != 1 || roots[0].UserVote != 1 || !roots[0].Answered {
+		t.Fatalf("root annotations = %+v", roots[0])
+	}
+	if err := mem.VotePost(ctx, voter.ID, later.ID, 1); !errors.Is(err, ErrPostNotVotable) {
+		t.Fatalf("reply vote error = %v", err)
+	}
+}
+
+func TestMemoryPostValidation(t *testing.T) {
+	t.Parallel()
+
+	ctx := context.Background()
+	mem := NewMemory()
+	homeowner := &User{Username: "homeowner", PasswordHash: "hash", Role: RoleUser}
+	if err := mem.CreateUser(ctx, homeowner); err != nil {
+		t.Fatal(err)
+	}
+
+	tests := []struct {
+		name string
+		post *Post
+	}{
+		{
+			name: "root without title",
+			post: &Post{AuthorID: homeowner.ID, Body: "Body"},
+		},
+		{
+			name: "empty parent",
+			post: &Post{ParentID: ptr(""), AuthorID: homeowner.ID, Body: "Body"},
+		},
+		{
+			name: "missing parent",
+			post: &Post{ParentID: ptr("missing"), AuthorID: homeowner.ID, Body: "Body"},
+		},
+		{
+			name: "reply with root fields",
+			post: &Post{
+				ParentID: ptr("missing"),
+				AuthorID: homeowner.ID,
+				Title:    "Not allowed",
+				Body:     "Body",
+			},
+		},
+		{
+			name: "invalid post state",
+			post: &Post{
+				AuthorID:  homeowner.ID,
+				Title:     "Invalid state",
+				Body:      "Body",
+				PostState: PostState("archived"),
+			},
+		},
+		{
+			name: "reply with non-visible state",
+			post: &Post{
+				ParentID:  ptr("missing"),
+				AuthorID:  homeowner.ID,
+				Body:      "Body",
+				PostState: PostStateLocked,
+			},
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			if err := mem.CreatePost(ctx, test.post); !errors.Is(err, ErrInvalidPost) {
+				t.Fatalf("error = %v, want ErrInvalidPost", err)
+			}
+		})
+	}
+
+	hidden := &Post{
+		ID:        "hidden",
+		AuthorID:  homeowner.ID,
+		Title:     "Hidden",
+		Body:      "Body",
+		PostDate:  "2026-08-26",
+		PostState: PostStateHidden,
+	}
+	if err := mem.CreatePost(ctx, hidden); err != nil {
+		t.Fatal(err)
+	}
+	if err := mem.VotePost(ctx, homeowner.ID, hidden.ID, 1); !errors.Is(err, ErrPostNotVotable) {
+		t.Fatalf("hidden root vote error = %v", err)
+	}
+
+	locked := &Post{
+		ID:        "locked",
+		AuthorID:  homeowner.ID,
+		Title:     "Locked",
+		Body:      "Body",
+		PostDate:  "2026-08-26",
+		PostState: PostStateLocked,
+	}
+	if err := mem.CreatePost(ctx, locked); err != nil {
+		t.Fatal(err)
+	}
+	if err := mem.VotePost(ctx, homeowner.ID, locked.ID, 1); err != nil {
+		t.Fatalf("locked root should remain votable: %v", err)
+	}
+	roots, err := mem.ListRootPosts(ctx, locked.PostDate, homeowner.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(roots) != 1 || roots[0].ID != locked.ID || roots[0].PostState != PostStateLocked {
+		t.Fatalf("locked root should remain visible: %+v", roots)
+	}
+
+	if _, err := mem.GetPostThread(ctx, "missing"); !errors.Is(err, sql.ErrNoRows) {
+		t.Fatalf("missing thread error = %v", err)
+	}
+}
+
+func ptr(value string) *string {
+	return &value
+}

internal/store/postgres_store.go

@@ -29,6 +29,7 @@ func (p *Postgres) CreateUser(ctx context.Context, u *User) error {
 		return fmt.Errorf("invalid role")
 	}
 	u.Username = NormalizeUsername(u.Username)
+	u.Email = NormalizeEmail(u.Email)
 	if u.ID == "" {
 		u.ID = uuid.NewString()
 	}
@@ -69,6 +70,7 @@ func (p *Postgres) CreateUser(ctx context.Context, u *User) error {
 		Name:         u.Name,
 		PasswordHash: u.PasswordHash,
 		Role:         string(role),
+		Email:        u.Email,
 		CreatedAt:    u.CreatedAt,
 	}); err != nil {
 		return mapUniqueViolation(err)
@@ -142,6 +144,32 @@ func (p *Postgres) UpsertAnswer(ctx context.Context, a *Answer) error {
 	return a.Upsert(ctx)
 }
 
+func (p *Postgres) CreatePost(ctx context.Context, post *Post) error {
+	post.db = p.db
+	return post.Create(ctx)
+}
+
+func (p *Postgres) GetPost(ctx context.Context, id string) (*Post, error) {
+	return GetPost(ctx, p.db, id)
+}
+
+func (p *Postgres) GetPostThread(ctx context.Context, rootID string) (*Post, error) {
+	return GetPostThread(ctx, p.db, rootID)
+}
+
+func (p *Postgres) UpdatePost(ctx context.Context, post *Post) error {
+	post.db = p.db
+	return post.Update(ctx)
+}
+
+func (p *Postgres) ListRootPosts(ctx context.Context, postDate, viewerID string) ([]Post, error) {
+	return ListRootPosts(ctx, p.db, postDate, viewerID)
+}
+
+func (p *Postgres) VotePost(ctx context.Context, userID, postID string, value int) error {
+	return SetPostVote(ctx, p.db, userID, postID, value)
+}
+
 func (p *Postgres) Vote(ctx context.Context, userID, questionID string, value int) error {
 	return Vote(ctx, p.db, userID, questionID, value)
 }

internal/store/sqlc/models.go

@@ -5,6 +5,7 @@
 package sqlc
 
 import (
+	"database/sql"
 	"time"
 )
 
@@ -16,6 +17,25 @@ type Answer struct {
 	UpdatedAt  string
 }
 
+type Post struct {
+	ID        string
+	ParentID  sql.NullString
+	AuthorID  string
+	Title     string
+	Body      string
+	City      string
+	PostDate  string
+	PostState string
+	CreatedAt string
+	UpdatedAt string
+}
+
+type PostVote struct {
+	UserID string
+	PostID string
+	Value  int32
+}
+
 type Question struct {
 	ID        string
 	AuthorID  string
@@ -39,6 +59,7 @@ type User struct {
 	Name         string
 	PasswordHash string
 	Role         string
+	Email        string
 	AvatarUrl    string
 	State        string
 	CreatedAt    string

internal/store/sqlc/posts.sql.go

@@ -0,0 +1,385 @@
+// Code generated by sqlc. DO NOT EDIT.
+// versions:
+//   sqlc v1.31.1
+// source: posts.sql
+
+package sqlc
+
+import (
+	"context"
+	"database/sql"
+)
+
+const createPost = `-- name: CreatePost :exec
+INSERT INTO posts (
+  id, parent_id, author_id, title, body, city, post_date, post_state, created_at, updated_at
+)
+VALUES (
+  $1,
+  $2,
+  $3,
+  $4,
+  $5,
+  $6,
+  $7,
+  $8,
+  $9,
+  $10
+)
+`
+
+type CreatePostParams struct {
+	ID        string
+	ParentID  sql.NullString
+	AuthorID  string
+	Title     string
+	Body      string
+	City      string
+	PostDate  string
+	PostState string
+	CreatedAt string
+	UpdatedAt string
+}
+
+func (q *Queries) CreatePost(ctx context.Context, arg CreatePostParams) error {
+	_, err := q.db.ExecContext(ctx, createPost,
+		arg.ID,
+		arg.ParentID,
+		arg.AuthorID,
+		arg.Title,
+		arg.Body,
+		arg.City,
+		arg.PostDate,
+		arg.PostState,
+		arg.CreatedAt,
+		arg.UpdatedAt,
+	)
+	return err
+}
+
+const deletePostVote = `-- name: DeletePostVote :exec
+DELETE FROM post_votes
+WHERE user_id = $1
+  AND post_id = $2
+`
+
+type DeletePostVoteParams struct {
+	UserID string
+	PostID string
+}
+
+func (q *Queries) DeletePostVote(ctx context.Context, arg DeletePostVoteParams) error {
+	_, err := q.db.ExecContext(ctx, deletePostVote, arg.UserID, arg.PostID)
+	return err
+}
+
+const getPost = `-- name: GetPost :one
+SELECT
+  p.id, p.parent_id, p.author_id, u.name AS author_name, u.role AS author_role,
+  p.title, p.body, p.city, p.post_date, p.post_state, p.created_at, p.updated_at
+FROM posts p
+JOIN users u ON u.id = p.author_id
+WHERE p.id = $1
+`
+
+type GetPostRow struct {
+	ID         string
+	ParentID   sql.NullString
+	AuthorID   string
+	AuthorName string
+	AuthorRole string
+	Title      string
+	Body       string
+	City       string
+	PostDate   string
+	PostState  string
+	CreatedAt  string
+	UpdatedAt  string
+}
+
+func (q *Queries) GetPost(ctx context.Context, id string) (GetPostRow, error) {
+	row := q.db.QueryRowContext(ctx, getPost, id)
+	var i GetPostRow
+	err := row.Scan(
+		&i.ID,
+		&i.ParentID,
+		&i.AuthorID,
+		&i.AuthorName,
+		&i.AuthorRole,
+		&i.Title,
+		&i.Body,
+		&i.City,
+		&i.PostDate,
+		&i.PostState,
+		&i.CreatedAt,
+		&i.UpdatedAt,
+	)
+	return i, err
+}
+
+const listPostThread = `-- name: ListPostThread :many
+WITH RECURSIVE thread AS (
+  SELECT p.id, p.parent_id, p.author_id, p.title, p.body, p.city, p.post_date, p.post_state, p.created_at, p.updated_at
+  FROM posts p
+  WHERE p.id = $1 AND p.parent_id IS NULL
+
+  UNION ALL
+
+  SELECT child.id, child.parent_id, child.author_id, child.title, child.body, child.city, child.post_date, child.post_state, child.created_at, child.updated_at
+  FROM posts child
+  JOIN thread parent ON child.parent_id = parent.id
+)
+SELECT
+  thread.id, thread.parent_id, thread.author_id,
+  u.name AS author_name, u.role AS author_role,
+  thread.title, thread.body, thread.city, thread.post_date,
+  thread.post_state, thread.created_at, thread.updated_at
+FROM thread
+JOIN users u ON u.id = thread.author_id
+ORDER BY thread.created_at, thread.id
+`
+
+type ListPostThreadRow struct {
+	ID         string
+	ParentID   sql.NullString
+	AuthorID   string
+	AuthorName string
+	AuthorRole string
+	Title      string
+	Body       string
+	City       string
+	PostDate   string
+	PostState  string
+	CreatedAt  string
+	UpdatedAt  string
+}
+
+func (q *Queries) ListPostThread(ctx context.Context, rootID string) ([]ListPostThreadRow, error) {
+	rows, err := q.db.QueryContext(ctx, listPostThread, rootID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	items := []ListPostThreadRow{}
+	for rows.Next() {
+		var i ListPostThreadRow
+		if err := rows.Scan(
+			&i.ID,
+			&i.ParentID,
+			&i.AuthorID,
+			&i.AuthorName,
+			&i.AuthorRole,
+			&i.Title,
+			&i.Body,
+			&i.City,
+			&i.PostDate,
+			&i.PostState,
+			&i.CreatedAt,
+			&i.UpdatedAt,
+		); err != nil {
+			return nil, err
+		}
+		items = append(items, i)
+	}
+	if err := rows.Close(); err != nil {
+		return nil, err
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}
+
+const listRootPosts = `-- name: ListRootPosts :many
+WITH RECURSIVE roots AS (
+  SELECT p.id, p.parent_id, p.author_id, p.title, p.body, p.city, p.post_date, p.post_state, p.created_at, p.updated_at
+  FROM posts p
+  WHERE p.parent_id IS NULL
+    AND p.post_date = $3
+    AND p.post_state <> $4
+),
+thread AS (
+  SELECT roots.id AS root_id, child.id AS post_id, child.author_id
+  FROM roots
+  JOIN posts child ON child.parent_id = roots.id
+
+  UNION ALL
+
+  SELECT thread.root_id, child.id, child.author_id
+  FROM thread
+  JOIN posts child ON child.parent_id = thread.post_id
+),
+answered AS (
+  SELECT DISTINCT thread.root_id
+  FROM thread
+  JOIN users u ON u.id = thread.author_id
+  WHERE u.role = 'admin'
+),
+scores AS (
+  SELECT votes.post_id, SUM(votes.value)::bigint AS score
+  FROM roots
+  JOIN post_votes votes ON votes.post_id = roots.id
+  GROUP BY votes.post_id
+)
+SELECT
+  roots.id, roots.parent_id, roots.author_id,
+  u.name AS author_name, u.role AS author_role,
+  roots.title, roots.body, roots.city, roots.post_date,
+  roots.post_state, roots.created_at, roots.updated_at,
+  COALESCE(scores.score, 0)::bigint AS score,
+  (answered.root_id IS NOT NULL)::bool AS answered,
+  COALESCE(viewer_vote.value, 0)::bigint AS user_vote
+FROM roots
+JOIN users u ON u.id = roots.author_id
+LEFT JOIN scores ON scores.post_id = roots.id
+LEFT JOIN answered ON answered.root_id = roots.id
+LEFT JOIN post_votes viewer_vote
+  ON viewer_vote.user_id = $1
+  AND viewer_vote.post_id = roots.id
+ORDER BY score DESC, roots.created_at, roots.id
+LIMIT $2
+`
+
+type ListRootPostsParams struct {
+	ViewerID    string
+	RowLimit    int32
+	PostDate    string
+	HiddenState string
+}
+
+type ListRootPostsRow struct {
+	ID         string
+	ParentID   sql.NullString
+	AuthorID   string
+	AuthorName string
+	AuthorRole string
+	Title      string
+	Body       string
+	City       string
+	PostDate   string
+	PostState  string
+	CreatedAt  string
+	UpdatedAt  string
+	Score      int64
+	Answered   bool
+	UserVote   int64
+}
+
+func (q *Queries) ListRootPosts(ctx context.Context, arg ListRootPostsParams) ([]ListRootPostsRow, error) {
+	rows, err := q.db.QueryContext(ctx, listRootPosts,
+		arg.ViewerID,
+		arg.RowLimit,
+		arg.PostDate,
+		arg.HiddenState,
+	)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	items := []ListRootPostsRow{}
+	for rows.Next() {
+		var i ListRootPostsRow
+		if err := rows.Scan(
+			&i.ID,
+			&i.ParentID,
+			&i.AuthorID,
+			&i.AuthorName,
+			&i.AuthorRole,
+			&i.Title,
+			&i.Body,
+			&i.City,
+			&i.PostDate,
+			&i.PostState,
+			&i.CreatedAt,
+			&i.UpdatedAt,
+			&i.Score,
+			&i.Answered,
+			&i.UserVote,
+		); err != nil {
+			return nil, err
+		}
+		items = append(items, i)
+	}
+	if err := rows.Close(); err != nil {
+		return nil, err
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}
+
+const postIsVisibleRoot = `-- name: PostIsVisibleRoot :one
+SELECT EXISTS(
+  SELECT 1
+  FROM posts
+  WHERE id = $1
+    AND parent_id IS NULL
+    AND post_state <> $2
+)::bool
+`
+
+type PostIsVisibleRootParams struct {
+	ID          string
+	HiddenState string
+}
+
+func (q *Queries) PostIsVisibleRoot(ctx context.Context, arg PostIsVisibleRootParams) (bool, error) {
+	row := q.db.QueryRowContext(ctx, postIsVisibleRoot, arg.ID, arg.HiddenState)
+	var column_1 bool
+	err := row.Scan(&column_1)
+	return column_1, err
+}
+
+const updatePost = `-- name: UpdatePost :execrows
+UPDATE posts
+SET
+  body = $1,
+  updated_at = $2
+WHERE id = $3
+`
+
+type UpdatePostParams struct {
+	Body      string
+	UpdatedAt string
+	ID        string
+}
+
+func (q *Queries) UpdatePost(ctx context.Context, arg UpdatePostParams) (int64, error) {
+	result, err := q.db.ExecContext(ctx, updatePost, arg.Body, arg.UpdatedAt, arg.ID)
+	if err != nil {
+		return 0, err
+	}
+	return result.RowsAffected()
+}
+
+const upsertPostVoteOnVisibleRoot = `-- name: UpsertPostVoteOnVisibleRoot :execrows
+INSERT INTO post_votes (user_id, post_id, value)
+SELECT $1, $2, $3
+FROM posts p
+WHERE p.id = $2
+  AND p.parent_id IS NULL
+  AND p.post_state <> $4
+ON CONFLICT (user_id, post_id) DO UPDATE
+SET value = excluded.value
+`
+
+type UpsertPostVoteOnVisibleRootParams struct {
+	UserID      string
+	PostID      string
+	Value       int32
+	HiddenState string
+}
+
+func (q *Queries) UpsertPostVoteOnVisibleRoot(ctx context.Context, arg UpsertPostVoteOnVisibleRootParams) (int64, error) {
+	result, err := q.db.ExecContext(ctx, upsertPostVoteOnVisibleRoot,
+		arg.UserID,
+		arg.PostID,
+		arg.Value,
+		arg.HiddenState,
+	)
+	if err != nil {
+		return 0, err
+	}
+	return result.RowsAffected()
+}

internal/store/sqlc/users.sql.go

@@ -24,8 +24,8 @@ func (q *Queries) CountAdmins(ctx context.Context, role string) (int64, error) {
 }
 
 const createUser = `-- name: CreateUser :exec
-INSERT INTO users (id, username, name, password_hash, role, avatar_url, state, created_at)
-VALUES ($1, $2, $3, $4, $5, '', '', $6)
+INSERT INTO users (id, username, name, password_hash, role, email, avatar_url, state, created_at)
+VALUES ($1, $2, $3, $4, $5, $6, '', '', $7)
 `
 
 type CreateUserParams struct {
@@ -34,6 +34,7 @@ type CreateUserParams struct {
 	Name         string
 	PasswordHash string
 	Role         string
+	Email        string
 	CreatedAt    string
 }
 
@@ -44,13 +45,14 @@ func (q *Queries) CreateUser(ctx context.Context, arg CreateUserParams) error {
 		arg.Name,
 		arg.PasswordHash,
 		arg.Role,
+		arg.Email,
 		arg.CreatedAt,
 	)
 	return err
 }
 
 const getUserByID = `-- name: GetUserByID :one
-SELECT id, username, name, role, avatar_url, state, created_at
+SELECT id, username, name, role, email, avatar_url, state, created_at
 FROM users
 WHERE id = $1
 `
@@ -60,6 +62,7 @@ type GetUserByIDRow struct {
 	Username  string
 	Name      string
 	Role      string
+	Email     string
 	AvatarUrl string
 	State     string
 	CreatedAt string
@@ -73,6 +76,7 @@ func (q *Queries) GetUserByID(ctx context.Context, id string) (GetUserByIDRow, e
 		&i.Username,
 		&i.Name,
 		&i.Role,
+		&i.Email,
 		&i.AvatarUrl,
 		&i.State,
 		&i.CreatedAt,
@@ -81,7 +85,7 @@ func (q *Queries) GetUserByID(ctx context.Context, id string) (GetUserByIDRow, e
 }
 
 const getUserByUsername = `-- name: GetUserByUsername :one
-SELECT id, username, name, role, avatar_url, state, created_at, password_hash
+SELECT id, username, name, role, email, avatar_url, state, created_at, password_hash
 FROM users
 WHERE username = $1
 `
@@ -91,6 +95,7 @@ type GetUserByUsernameRow struct {
 	Username     string
 	Name         string
 	Role         string
+	Email        string
 	AvatarUrl    string
 	State        string
 	CreatedAt    string
@@ -105,6 +110,7 @@ func (q *Queries) GetUserByUsername(ctx context.Context, username string) (GetUs
 		&i.Username,
 		&i.Name,
 		&i.Role,
+		&i.Email,
 		&i.AvatarUrl,
 		&i.State,
 		&i.CreatedAt,
@@ -127,12 +133,13 @@ func (q *Queries) GetUserRole(ctx context.Context, id string) (string, error) {
 }
 
 const listUsers = `-- name: ListUsers :many
-SELECT id, username, name, role, avatar_url, state, created_at
+SELECT id, username, name, role, email, avatar_url, state, created_at
 FROM users
 WHERE (
   $1 = ''
   OR username ILIKE '%' || $1 || '%'
   OR name ILIKE '%' || $1 || '%'
+  OR email ILIKE '%' || $1 || '%'
 )
 AND (
   $2 = ''
@@ -155,6 +162,7 @@ type ListUsersRow struct {
 	Username  string
 	Name      string
 	Role      string
+	Email     string
 	AvatarUrl string
 	State     string
 	CreatedAt string
@@ -179,6 +187,7 @@ func (q *Queries) ListUsers(ctx context.Context, arg ListUsersParams) ([]ListUse
 			&i.Username,
 			&i.Name,
 			&i.Role,
+			&i.Email,
 			&i.AvatarUrl,
 			&i.State,
 			&i.CreatedAt,
@@ -196,6 +205,46 @@ func (q *Queries) ListUsers(ctx context.Context, arg ListUsersParams) ([]ListUse
 	return items, nil
 }
 
+const updateUserProfile = `-- name: UpdateUserProfile :exec
+UPDATE users
+SET state = $1, email = $2
+WHERE id = $3
+`
+
+type UpdateUserProfileParams struct {
+	State string
+	Email string
+	ID    string
+}
+
+func (q *Queries) UpdateUserProfile(ctx context.Context, arg UpdateUserProfileParams) error {
+	_, err := q.db.ExecContext(ctx, updateUserProfile, arg.State, arg.Email, arg.ID)
+	return err
+}
+
+const updateUserProfileAndAvatar = `-- name: UpdateUserProfileAndAvatar :exec
+UPDATE users
+SET state = $1, email = $2, avatar_url = $3
+WHERE id = $4
+`
+
+type UpdateUserProfileAndAvatarParams struct {
+	State     string
+	Email     string
+	AvatarUrl string
+	ID        string
+}
+
+func (q *Queries) UpdateUserProfileAndAvatar(ctx context.Context, arg UpdateUserProfileAndAvatarParams) error {
+	_, err := q.db.ExecContext(ctx, updateUserProfileAndAvatar,
+		arg.State,
+		arg.Email,
+		arg.AvatarUrl,
+		arg.ID,
+	)
+	return err
+}
+
 const updateUserRole = `-- name: UpdateUserRole :execresult
 UPDATE users
 SET role = $1
@@ -210,36 +259,3 @@ type UpdateUserRoleParams struct {
 func (q *Queries) UpdateUserRole(ctx context.Context, arg UpdateUserRoleParams) (sql.Result, error) {
 	return q.db.ExecContext(ctx, updateUserRole, arg.Role, arg.ID)
 }
-
-const updateUserState = `-- name: UpdateUserState :exec
-UPDATE users
-SET state = $1
-WHERE id = $2
-`
-
-type UpdateUserStateParams struct {
-	State string
-	ID    string
-}
-
-func (q *Queries) UpdateUserState(ctx context.Context, arg UpdateUserStateParams) error {
-	_, err := q.db.ExecContext(ctx, updateUserState, arg.State, arg.ID)
-	return err
-}
-
-const updateUserStateAndAvatar = `-- name: UpdateUserStateAndAvatar :exec
-UPDATE users
-SET state = $1, avatar_url = $2
-WHERE id = $3
-`
-
-type UpdateUserStateAndAvatarParams struct {
-	State     string
-	AvatarUrl string
-	ID        string
-}
-
-func (q *Queries) UpdateUserStateAndAvatar(ctx context.Context, arg UpdateUserStateAndAvatarParams) error {
-	_, err := q.db.ExecContext(ctx, updateUserStateAndAvatar, arg.State, arg.AvatarUrl, arg.ID)
-	return err
-}

internal/store/store.go

@@ -37,6 +37,13 @@ type Store interface {
 	GetAnswer(ctx context.Context, questionID string) (*Answer, error)
 	UpsertAnswer(ctx context.Context, a *Answer) error
 
+	CreatePost(ctx context.Context, post *Post) error
+	GetPost(ctx context.Context, id string) (*Post, error)
+	GetPostThread(ctx context.Context, rootID string) (*Post, error)
+	UpdatePost(ctx context.Context, post *Post) error
+	ListRootPosts(ctx context.Context, postDate, viewerID string) ([]Post, error)
+	VotePost(ctx context.Context, userID, postID string, value int) error
+
 	// Vote sets the vote to 1, -1, or 0 (clear) on a visible question.
 	Vote(ctx context.Context, userID, questionID string, value int) error
 }

internal/store/user.go

@@ -30,6 +30,7 @@ type User struct {
 	Username     string
 	Name         string
 	Role         Role
+	Email        string
 	AvatarURL    string
 	State        string
 	CreatedAt    string
@@ -50,12 +51,13 @@ func NormalizeUsername(s string) string {
 	return strings.ToLower(strings.TrimSpace(s))
 }
 
-func toUser(db *sql.DB, id, username, name, role, avatarURL, state, createdAt, passwordHash string) *User {
+func toUser(db *sql.DB, id, username, name, role, email, avatarURL, state, createdAt, passwordHash string) *User {
 	return &User{
 		ID:           id,
 		Username:     username,
 		Name:         name,
 		Role:         Role(role),
+		Email:        email,
 		AvatarURL:    avatarURL,
 		State:        state,
 		CreatedAt:    createdAt,
@@ -73,6 +75,7 @@ func (u *User) Create(ctx context.Context) error {
 		return fmt.Errorf("invalid role")
 	}
 	u.Username = NormalizeUsername(u.Username)
+	u.Email = NormalizeEmail(u.Email)
 	if u.ID == "" {
 		u.ID = uuid.NewString()
 	}
@@ -88,6 +91,7 @@ func (u *User) Create(ctx context.Context) error {
 		Name:         u.Name,
 		PasswordHash: u.PasswordHash,
 		Role:         string(u.Role),
+		Email:        u.Email,
 		CreatedAt:    u.CreatedAt,
 	}))
 }
@@ -149,21 +153,27 @@ func (u *User) SetRole(ctx context.Context, role Role) error {
 	return nil
 }
 
-// SaveProfile writes State and optionally AvatarURL.
+// SaveProfile writes Email, State, and optionally AvatarURL.
 func (u *User) SaveProfile(ctx context.Context) error {
 	if u == nil || u.db == nil {
 		return fmt.Errorf("user: no database")
 	}
 	u.State = strings.TrimSpace(u.State)
+	u.Email = NormalizeEmail(u.Email)
 	q := sqlc.New(u.db)
 	if u.AvatarURL == "" {
-		return q.UpdateUserState(ctx, sqlc.UpdateUserStateParams{State: u.State, ID: u.ID})
+		return mapUniqueViolation(q.UpdateUserProfile(ctx, sqlc.UpdateUserProfileParams{
+			State: u.State,
+			Email: u.Email,
+			ID:    u.ID,
+		}))
 	}
-	return q.UpdateUserStateAndAvatar(ctx, sqlc.UpdateUserStateAndAvatarParams{
+	return mapUniqueViolation(q.UpdateUserProfileAndAvatar(ctx, sqlc.UpdateUserProfileAndAvatarParams{
 		State:     u.State,
+		Email:     u.Email,
 		AvatarUrl: u.AvatarURL,
 		ID:        u.ID,
-	})
+	}))
 }
 
 func CountAdmins(ctx context.Context, db *sql.DB) (int, error) {
@@ -187,7 +197,7 @@ func ListUsers(ctx context.Context, db *sql.DB, q ListUsersQuery) ([]User, strin
 	}
 	out := make([]User, 0, len(rows))
 	for _, r := range rows {
-		u := toUser(db, r.ID, r.Username, r.Name, r.Role, r.AvatarUrl, r.State, r.CreatedAt, "")
+		u := toUser(db, r.ID, r.Username, r.Name, r.Role, r.Email, r.AvatarUrl, r.State, r.CreatedAt, "")
 		out = append(out, *u)
 	}
 	var nextCreated, nextID string
@@ -204,7 +214,7 @@ func UserByID(ctx context.Context, db *sql.DB, id string) (*User, error) {
 	if err != nil {
 		return nil, err
 	}
-	return toUser(db, r.ID, r.Username, r.Name, r.Role, r.AvatarUrl, r.State, r.CreatedAt, ""), nil
+	return toUser(db, r.ID, r.Username, r.Name, r.Role, r.Email, r.AvatarUrl, r.State, r.CreatedAt, ""), nil
 }
 
 func UserByUsername(ctx context.Context, db *sql.DB, username string) (*User, error) {
@@ -212,5 +222,5 @@ func UserByUsername(ctx context.Context, db *sql.DB, username string) (*User, er
 	if err != nil {
 		return nil, err
 	}
-	return toUser(db, r.ID, r.Username, r.Name, r.Role, r.AvatarUrl, r.State, r.CreatedAt, r.PasswordHash), nil
+	return toUser(db, r.ID, r.Username, r.Name, r.Role, r.Email, r.AvatarUrl, r.State, r.CreatedAt, r.PasswordHash), nil
 }

internal/store/vote.go

@@ -5,6 +5,7 @@ import (
 	"database/sql"
 	"errors"
 	"fmt"
+	"strings"
 
 	"github.com/jackc/pgx/v5/pgconn"
 
@@ -14,6 +15,9 @@ import (
 // ErrDuplicateUsername is returned when inserting a username that already exists.
 var ErrDuplicateUsername = errors.New("username taken")
 
+// ErrDuplicateEmail is returned when inserting/updating an email that already exists.
+var ErrDuplicateEmail = errors.New("email taken")
+
 // ErrHiddenOrMissing is returned when voting on a hidden or unknown question.
 var ErrHiddenOrMissing = errors.New("question not votable")
 
@@ -58,6 +62,9 @@ func Vote(ctx context.Context, db *sql.DB, userID, questionID string, value int)
 func mapUniqueViolation(err error) error {
 	var pgErr *pgconn.PgError
 	if errors.As(err, &pgErr) && pgErr.Code == "23505" {
+		if strings.Contains(strings.ToLower(pgErr.ConstraintName), "email") {
+			return ErrDuplicateEmail
+		}
 		return ErrDuplicateUsername
 	}
 	return err

internal/web/auth.go

@@ -129,14 +129,21 @@ func (s *Server) handleRegister(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	username := strings.TrimSpace(r.PostFormValue("username"))
+	emailRaw := r.PostFormValue("email")
 	password := r.PostFormValue("password")
 	setupSecret := r.PostFormValue("setup_secret")
-	p := authPage{page: s.basePage(r, "Create account"), Username: username}
+	p := authPage{page: s.basePage(r, "Create account"), Username: username, Email: strings.TrimSpace(emailRaw)}
 	if !usernameRe.MatchString(username) {
 		p.Error = "Username must be 3–20 letters, numbers, or underscores."
 		s.exec(w, "register", p)
 		return
 	}
+	email, emailErr := store.ValidateEmail(emailRaw)
+	if emailErr != "" {
+		p.Error = emailErr
+		s.exec(w, "register", p)
+		return
+	}
 	if ok, msg := passwordValid(password); !ok {
 		p.Error = msg
 		s.exec(w, "register", p)
@@ -153,6 +160,7 @@ func (s *Server) handleRegister(w http.ResponseWriter, r *http.Request) {
 	}
 	u := &store.User{
 		Username:     username,
+		Email:        email,
 		PasswordHash: string(hash),
 		Role:         role,
 	}
@@ -162,6 +170,11 @@ func (s *Server) handleRegister(w http.ResponseWriter, r *http.Request) {
 			s.exec(w, "register", p)
 			return
 		}
+		if errors.Is(err, store.ErrDuplicateEmail) {
+			p.Error = "That email is already registered."
+			s.exec(w, "register", p)
+			return
+		}
 		log.Printf("register create: %v", err)
 		http.Error(w, "could not create account", http.StatusInternalServerError)
 		return

internal/web/profile.go

@@ -2,6 +2,7 @@ package web
 
 import (
 	"bytes"
+	"errors"
 	"fmt"
 	"image"
 	"image/jpeg"
@@ -27,6 +28,7 @@ type profilePage struct {
 	UploadsEnabled bool
 	Error          string
 	StateVal       string
+	EmailVal       string
 }
 
 func (s *Server) handleProfileForm(w http.ResponseWriter, r *http.Request) {
@@ -35,7 +37,7 @@ func (s *Server) handleProfileForm(w http.ResponseWriter, r *http.Request) {
 		http.Redirect(w, r, "/login?next=/profile", http.StatusSeeOther)
 		return
 	}
-	s.renderProfile(w, r, u, "", u.State)
+	s.renderProfile(w, r, u, "", u.State, u.Email)
 }
 
 func (s *Server) handleProfile(w http.ResponseWriter, r *http.Request) {
@@ -45,7 +47,7 @@ func (s *Server) handleProfile(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	if err := r.ParseMultipartForm(3 << 20); err != nil {
-		s.renderProfile(w, r, u, "Could not read form (max 2MB for images).", u.State)
+		s.renderProfile(w, r, u, "Could not read form (max 2MB for images).", u.State, u.Email)
 		return
 	}
 	want := s.sessions.GetString(r.Context(), "csrf")
@@ -57,7 +59,12 @@ func (s *Server) handleProfile(w http.ResponseWriter, r *http.Request) {
 
 	state := geo.NormalizeState(r.FormValue("state"))
 	if !geo.ValidState(state) {
-		s.renderProfile(w, r, u, "Choose a valid US state or leave it blank.", state)
+		s.renderProfile(w, r, u, "Choose a valid US state or leave it blank.", state, r.FormValue("email"))
+		return
+	}
+	email, emailErr := store.ValidateEmail(r.FormValue("email"))
+	if emailErr != "" {
+		s.renderProfile(w, r, u, emailErr, state, r.FormValue("email"))
 		return
 	}
 
@@ -67,16 +74,16 @@ func (s *Server) handleProfile(w http.ResponseWriter, r *http.Request) {
 	if err == nil {
 		defer file.Close()
 		if !s.cfg.Blob.Enabled() {
-			s.renderProfile(w, r, u, "Avatar uploads are not configured on this server.", state)
+			s.renderProfile(w, r, u, "Avatar uploads are not configured on this server.", state, email)
 			return
 		}
 		if hdr.Size > 2<<20 {
-			s.renderProfile(w, r, u, "Avatar must be 2MB or smaller.", state)
+			s.renderProfile(w, r, u, "Avatar must be 2MB or smaller.", state, email)
 			return
 		}
 		body, ext, contentType, prepErr := prepareAvatar(file, 2<<20)
 		if prepErr != nil {
-			s.renderProfile(w, r, u, "Avatar must be a JPEG, PNG, or WebP image.", state)
+			s.renderProfile(w, r, u, "Avatar must be a JPEG, PNG, or WebP image.", state, email)
 			return
 		}
 		prevURL := u.AvatarURL
@@ -88,14 +95,19 @@ func (s *Server) handleProfile(w http.ResponseWriter, r *http.Request) {
 			Size:        int64(len(body)),
 		})
 		if upErr != nil {
-			s.renderProfile(w, r, u, "Could not upload avatar. Try again later.", state)
+			s.renderProfile(w, r, u, "Could not upload avatar. Try again later.", state, email)
 			return
 		}
 		avatarURL = url
 		u.State = state
+		u.Email = email
 		u.AvatarURL = avatarURL
 		if err := s.store.SaveUserProfile(r.Context(), u); err != nil {
 			_ = s.cfg.Blob.Delete(r.Context(), avatarKey)
+			if errors.Is(err, store.ErrDuplicateEmail) {
+				s.renderProfile(w, r, u, "That email is already registered.", state, email)
+				return
+			}
 			http.Error(w, "could not save profile", http.StatusInternalServerError)
 			return
 		}
@@ -106,12 +118,17 @@ func (s *Server) handleProfile(w http.ResponseWriter, r *http.Request) {
 		http.Redirect(w, r, "/profile", http.StatusSeeOther)
 		return
 	} else if err != http.ErrMissingFile {
-		s.renderProfile(w, r, u, "Could not read avatar file.", state)
+		s.renderProfile(w, r, u, "Could not read avatar file.", state, email)
 		return
 	}
 
 	u.State = state
+	u.Email = email
 	if err := s.store.SaveUserProfile(r.Context(), u); err != nil {
+		if errors.Is(err, store.ErrDuplicateEmail) {
+			s.renderProfile(w, r, u, "That email is already registered.", state, email)
+			return
+		}
 		http.Error(w, "could not save profile", http.StatusInternalServerError)
 		return
 	}
@@ -236,7 +253,7 @@ func fitAvatar(img image.Image, maxDim int) image.Image {
 	return dst
 }
 
-func (s *Server) renderProfile(w http.ResponseWriter, r *http.Request, u *store.User, errMsg, stateVal string) {
+func (s *Server) renderProfile(w http.ResponseWriter, r *http.Request, u *store.User, errMsg, stateVal, emailVal string) {
 	var (
 		questions []store.RankedQuestion
 		label     string
@@ -263,5 +280,6 @@ func (s *Server) renderProfile(w http.ResponseWriter, r *http.Request, u *store.
 		UploadsEnabled: s.cfg.Blob.Enabled(),
 		Error:          errMsg,
 		StateVal:       stateVal,
+		EmailVal:       emailVal,
 	})
 }

internal/web/server.go

@@ -22,6 +22,7 @@ import (
 
 	"plumber/internal/blob"
 	"plumber/internal/geo"
+	"plumber/internal/mail"
 	"plumber/internal/pacific"
 	"plumber/internal/store"
 )
@@ -34,6 +35,7 @@ type Config struct {
 	// TrustedProxies are CIDRs allowed to set X-Forwarded-For (direct peer).
 	TrustedProxies []*net.IPNet
 	Blob           blob.Uploader
+	Mail           mail.Notifier
 }
 
 type Server struct {
@@ -82,6 +84,7 @@ type submitPage struct {
 type authPage struct {
 	page
 	Username string
+	Email    string
 	Error    string
 	Next     string
 }
@@ -98,6 +101,9 @@ func New(st store.Store, sessionStore scs.Store, templateFS fs.FS, staticFS fs.F
 	if cfg.Blob == nil {
 		cfg.Blob = blob.Disabled{}
 	}
+	if cfg.Mail == nil {
+		cfg.Mail = mail.Nop{}
+	}
 	funcMap := template.FuncMap{
 		"voteCtx": func(user *store.User, csrf, view, date string, q store.RankedQuestion) voteCtx {
 			return voteCtx{User: user, CSRF: csrf, View: view, Date: date, Question: q}
@@ -482,6 +488,17 @@ func (s *Server) handleAnswer(w http.ResponseWriter, r *http.Request) {
 	if len(body) > 12000 {
 		body = truncateRunes(body, 12000)
 	}
+	q, err := s.store.GetQuestion(r.Context(), id, u.ID)
+	if err != nil {
+		http.NotFound(w, r)
+		return
+	}
+	_, priorErr := s.store.GetAnswer(r.Context(), id)
+	wasNew := errors.Is(priorErr, sql.ErrNoRows)
+	if priorErr != nil && !wasNew {
+		http.Error(w, "could not load answer", http.StatusInternalServerError)
+		return
+	}
 	ans := &store.Answer{
 		QuestionID: id,
 		AuthorID:   u.ID,
@@ -491,6 +508,9 @@ func (s *Server) handleAnswer(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "could not save answer", http.StatusInternalServerError)
 		return
 	}
+	if wasNew {
+		s.notifyQuestionAnswered(q, body, u.ID)
+	}
 	saved, err := s.store.GetAnswer(r.Context(), id)
 	if err != nil {
 		http.Error(w, "could not load answer", http.StatusInternalServerError)
@@ -503,6 +523,32 @@ func (s *Server) handleAnswer(w http.ResponseWriter, r *http.Request) {
 	http.Redirect(w, r, "/questions/"+url.PathEscape(id), http.StatusSeeOther)
 }
 
+func (s *Server) notifyQuestionAnswered(q *store.RankedQuestion, answerBody, adminID string) {
+	if q == nil || s.cfg.Mail == nil {
+		return
+	}
+	author, err := s.store.UserByID(context.Background(), q.AuthorID)
+	if err != nil || author == nil || author.Email == "" || author.ID == adminID {
+		return
+	}
+	msg := mail.QuestionAnswered{
+		ToEmail:       author.Email,
+		ToName:        author.Name,
+		QuestionID:    q.ID,
+		QuestionTitle: q.Title,
+		AnswerBody:    answerBody,
+	}
+	go func() {
+		ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+		defer cancel()
+		if err := s.cfg.Mail.NotifyQuestionAnswered(ctx, msg); err != nil {
+			log.Printf("notify answer %s: %v", q.ID, err)
+			return
+		}
+		log.Printf("notify answer %s: accepted", q.ID)
+	}()
+}
+
 func (s *Server) handleHide(w http.ResponseWriter, r *http.Request) {
 	if !s.requireCSRF(w, r) {
 		return

internal/web/server_test.go

@@ -19,6 +19,7 @@ import (
 
 	"plumber"
 	"plumber/internal/blob"
+	"plumber/internal/mail"
 	"plumber/internal/pacific"
 	"plumber/internal/store"
 )
@@ -53,6 +54,7 @@ func seedUser(t *testing.T, st store.Store, username, password string, role stor
 	}
 	u := &store.User{
 		Username:     username,
+		Email:        username + "@example.com",
 		PasswordHash: string(hash),
 		Role:         role,
 	}
@@ -114,7 +116,7 @@ func registerUser(t *testing.T, h http.Handler, username, password string, setup
 	pre := rec.Result().Cookies()
 	preToken := sessionValue(pre)
 	csrf := csrfFrom(rec.Body.String())
-	form := "_csrf=" + csrf + "&username=" + username + "&password=" + password
+	form := "_csrf=" + csrf + "&username=" + username + "&email=" + username + "%40example.com&password=" + password
 	if len(setupSecret) > 0 && setupSecret[0] != "" {
 		form += "&setup_secret=" + setupSecret[0]
 	}
@@ -362,6 +364,7 @@ func TestProfilePageAndState(t *testing.T) {
 	var buf bytes.Buffer
 	w := multipart.NewWriter(&buf)
 	_ = w.WriteField("_csrf", csrf)
+	_ = w.WriteField("email", name+"@example.com")
 	_ = w.WriteField("state", "CA")
 	_ = w.Close()
 	req = httptest.NewRequest(http.MethodPost, "/profile", &buf)
@@ -389,6 +392,7 @@ func TestProfilePageAndState(t *testing.T) {
 	buf.Reset()
 	w = multipart.NewWriter(&buf)
 	_ = w.WriteField("_csrf", csrf)
+	_ = w.WriteField("email", name+"@example.com")
 	_ = w.WriteField("state", "ZZ")
 	_ = w.Close()
 	req = httptest.NewRequest(http.MethodPost, "/profile", &buf)
@@ -449,6 +453,7 @@ func TestProfileAdminAnsweredListAndAvatarUpload(t *testing.T) {
 	var buf bytes.Buffer
 	w := multipart.NewWriter(&buf)
 	_ = w.WriteField("_csrf", csrf)
+	_ = w.WriteField("email", hubName+"@example.com")
 	_ = w.WriteField("state", "OR")
 	part, err := w.CreateFormFile("avatar", "pic.png")
 	if err != nil {
@@ -596,10 +601,32 @@ func TestMutationsVoteAnswerHideAndCSRF(t *testing.T) {
 	if rec.Code != 200 || !strings.Contains(rec.Body.String(), "Tighten the nuts") {
 		t.Fatalf("admin answer: %d %s", rec.Code, rec.Body.String())
 	}
+	if body := rec.Body.String(); !strings.Contains(body, `class="answer-editor"`) ||
+		!strings.Contains(body, "<summary>Edit answer</summary>") ||
+		!strings.Contains(body, ">Tighten the nuts.</textarea>") ||
+		!strings.Contains(body, `type="reset" class="btn btn-ghost"`) ||
+		!strings.Contains(body, `removeAttribute('open')`) ||
+		strings.Contains(body, `<details class="answer-editor" open`) {
+		t.Fatalf("admin answer editor is not collapsed and populated: %s", body)
+	}
 	if _, err := mem.GetAnswer(context.Background(), q.ID); err != nil {
 		t.Fatal(err)
 	}
 
+	// The public answer is visible to its author, but editing remains admin-only.
+	rec = httptest.NewRecorder()
+	req = httptest.NewRequest(http.MethodGet, "/questions/"+q.ID, nil)
+	for _, c := range userCookies {
+		req.AddCookie(c)
+	}
+	h.ServeHTTP(rec, req)
+	if rec.Code != 200 || !strings.Contains(rec.Body.String(), "Tighten the nuts.") {
+		t.Fatalf("question author cannot see answer: %d %s", rec.Code, rec.Body.String())
+	}
+	if strings.Contains(rec.Body.String(), `class="answer-editor"`) {
+		t.Fatalf("question author can see admin answer editor: %s", rec.Body.String())
+	}
+
 	// Hide invalid id
 	rec = httptest.NewRecorder()
 	req = httptest.NewRequest(http.MethodGet, "/questions/"+q.ID, nil)
@@ -666,6 +693,133 @@ func csrfFrom(html string) string {
 	return html[:j]
 }
 
+func TestRegisterRequiresEmail(t *testing.T) {
+	srv, _ := newTestServer(t, Config{})
+	h := srv.Handler()
+	rec := httptest.NewRecorder()
+	h.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, "/register", nil))
+	csrf := csrfFrom(rec.Body.String())
+	cookies := rec.Result().Cookies()
+	form := strings.NewReader("_csrf=" + csrf + "&username=" + uniq("noem") + "&email=bad&password=hunter22")
+	req := httptest.NewRequest(http.MethodPost, "/register", form)
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	for _, c := range cookies {
+		req.AddCookie(c)
+	}
+	rec = httptest.NewRecorder()
+	h.ServeHTTP(rec, req)
+	if rec.Code != 200 || !strings.Contains(rec.Body.String(), "valid email") {
+		t.Fatalf("want email validation error, got %d %s", rec.Code, rec.Body.String())
+	}
+}
+
+func TestAnswerNotifyFirstOnly(t *testing.T) {
+	recMail := &mail.Recording{}
+	srv, mem := newTestServer(t, Config{Mail: recMail})
+	h := srv.Handler()
+	adminName := uniq("adm")
+	askName := uniq("ask")
+	admin := seedUser(t, mem, adminName, "hunter22", store.RoleAdmin)
+	asker := seedUser(t, mem, askName, "hunter22", store.RoleUser)
+	adminCookies := loginUser(t, h, adminName, "hunter22")
+
+	q := &store.RankedQuestion{
+		AuthorID: asker.ID,
+		Title:    "Leaky sink",
+		Body:     "Drip",
+		City:     "Oakland",
+		HuntDate: pacific.Today(),
+	}
+	if err := mem.CreateQuestion(context.Background(), q); err != nil {
+		t.Fatal(err)
+	}
+
+	postAnswer := func(body string) {
+		t.Helper()
+		w := httptest.NewRecorder()
+		req := httptest.NewRequest(http.MethodGet, "/questions/"+q.ID, nil)
+		for _, c := range adminCookies {
+			req.AddCookie(c)
+		}
+		h.ServeHTTP(w, req)
+		csrf := csrfFrom(w.Body.String())
+		form := strings.NewReader("_csrf=" + csrf + "&body=" + body)
+		req = httptest.NewRequest(http.MethodPost, "/questions/"+q.ID+"/answer", form)
+		req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+		req.Header.Set("HX-Request", "true")
+		for _, c := range adminCookies {
+			req.AddCookie(c)
+		}
+		w = httptest.NewRecorder()
+		h.ServeHTTP(w, req)
+		if w.Code != 200 {
+			t.Fatalf("answer %d %s", w.Code, w.Body.String())
+		}
+	}
+
+	postAnswer("First+reply")
+	deadline := time.Now().Add(2 * time.Second)
+	var msgs []mail.QuestionAnswered
+	for time.Now().Before(deadline) {
+		msgs = recMail.Snapshot()
+		if len(msgs) > 0 {
+			break
+		}
+		time.Sleep(10 * time.Millisecond)
+	}
+	if len(msgs) != 1 {
+		t.Fatalf("first answer notifies once, got %d", len(msgs))
+	}
+	if msgs[0].ToEmail != asker.Email || msgs[0].QuestionID != q.ID {
+		t.Fatalf("unexpected notify: %+v", msgs[0])
+	}
+	if msgs[0].AnswerBody != "First reply" {
+		t.Fatalf("answer body %q", msgs[0].AnswerBody)
+	}
+
+	postAnswer("Edited+reply")
+	time.Sleep(50 * time.Millisecond)
+	if recMail.Len() != 1 {
+		t.Fatalf("edit must not notify again, got %d", recMail.Len())
+	}
+
+	// Author without email is skipped
+	recMail2 := &mail.Recording{}
+	srv2, mem2 := newTestServer(t, Config{Mail: recMail2})
+	h2 := srv2.Handler()
+	admin2 := seedUser(t, mem2, uniq("adm2"), "hunter22", store.RoleAdmin)
+	noMail := &store.User{Username: uniq("silent"), PasswordHash: admin.PasswordHash, Role: store.RoleUser, Email: ""}
+	hash, _ := bcrypt.GenerateFromPassword([]byte("hunter22"), bcrypt.MinCost)
+	noMail.PasswordHash = string(hash)
+	if err := mem2.CreateUser(context.Background(), noMail); err != nil {
+		t.Fatal(err)
+	}
+	q2 := &store.RankedQuestion{AuthorID: noMail.ID, Title: "Quiet", Body: "x", HuntDate: pacific.Today()}
+	if err := mem2.CreateQuestion(context.Background(), q2); err != nil {
+		t.Fatal(err)
+	}
+	cookies := loginUser(t, h2, admin2.Username, "hunter22")
+	w := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/questions/"+q2.ID, nil)
+	for _, c := range cookies {
+		req.AddCookie(c)
+	}
+	h2.ServeHTTP(w, req)
+	csrf := csrfFrom(w.Body.String())
+	form := strings.NewReader("_csrf=" + csrf + "&body=Hello")
+	req = httptest.NewRequest(http.MethodPost, "/questions/"+q2.ID+"/answer", form)
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	for _, c := range cookies {
+		req.AddCookie(c)
+	}
+	w = httptest.NewRecorder()
+	h2.ServeHTTP(w, req)
+	time.Sleep(50 * time.Millisecond)
+	if recMail2.Len() != 0 {
+		t.Fatalf("empty email must skip notify, got %d", recMail2.Len())
+	}
+}
+
 // TestRegisterThrottleUsesTCPPeerThroughRouter ensures forged X-Forwarded-For
 // cannot bypass rate limits when the direct peer is outside TrustedProxies.
 // This must go through Handler() so middleware ordering bugs are caught.

schema.sql

@@ -4,11 +4,16 @@ CREATE TABLE IF NOT EXISTS users (
   name TEXT NOT NULL,
   password_hash TEXT NOT NULL,
   role TEXT NOT NULL DEFAULT 'user' CHECK (role IN ('user', 'admin')),
+  email TEXT NOT NULL DEFAULT '',
   avatar_url TEXT NOT NULL DEFAULT '',
   state TEXT NOT NULL DEFAULT '',
   created_at TEXT NOT NULL
 );
 
+CREATE UNIQUE INDEX IF NOT EXISTS users_email_lower_uidx
+  ON users (lower(email))
+  WHERE email <> '';
+
 CREATE TABLE IF NOT EXISTS questions (
   id TEXT PRIMARY KEY,
   author_id TEXT NOT NULL REFERENCES users(id),
@@ -37,6 +42,41 @@ CREATE TABLE IF NOT EXISTS answers (
   updated_at TEXT NOT NULL
 );
 
+CREATE TABLE IF NOT EXISTS posts (
+  id TEXT PRIMARY KEY,
+  parent_id TEXT REFERENCES posts(id) ON DELETE CASCADE,
+  author_id TEXT NOT NULL REFERENCES users(id),
+  title TEXT NOT NULL DEFAULT '',
+  body TEXT NOT NULL,
+  city TEXT NOT NULL DEFAULT '',
+  post_date TEXT NOT NULL DEFAULT '',
+  post_state TEXT NOT NULL,
+  created_at TEXT NOT NULL,
+  updated_at TEXT NOT NULL,
+  CONSTRAINT posts_shape_check CHECK (
+    (parent_id IS NULL AND title <> '' AND post_date <> '')
+    OR
+    (parent_id IS NOT NULL AND title = '' AND city = '' AND post_date = '')
+  )
+);
+
+CREATE INDEX IF NOT EXISTS idx_posts_parent_created
+  ON posts(parent_id, created_at, id);
+
+CREATE INDEX IF NOT EXISTS idx_posts_root_date
+  ON posts(post_date, post_state)
+  WHERE parent_id IS NULL;
+
+CREATE TABLE IF NOT EXISTS post_votes (
+  user_id TEXT NOT NULL REFERENCES users(id),
+  post_id TEXT NOT NULL REFERENCES posts(id) ON DELETE CASCADE,
+  value INTEGER NOT NULL CHECK (value IN (-1, 1)),
+  PRIMARY KEY (user_id, post_id)
+);
+
+CREATE INDEX IF NOT EXISTS idx_post_votes_post_id
+  ON post_votes(post_id);
+
 CREATE TABLE IF NOT EXISTS sessions (
   token TEXT PRIMARY KEY,
   data BYTEA NOT NULL,

static/app.css

@@ -610,6 +610,44 @@ input:focus, textarea:focus, .btn:focus-visible, .chip:focus-visible, .vote-btn:
   font-size: 0.72rem;
 }
 
+.answer-editor {
+  margin-top: 16px;
+  border-top: 1px solid var(--line);
+}
+
+.answer-editor summary {
+  display: flex;
+  width: fit-content;
+  min-height: 44px;
+  align-items: center;
+  color: var(--muted);
+  font-family: var(--mono);
+  font-size: 0.72rem;
+  letter-spacing: 0.06em;
+  text-transform: uppercase;
+  text-decoration: underline;
+  cursor: pointer;
+  list-style: none;
+}
+
+.answer-editor summary::-webkit-details-marker { display: none; }
+.answer-editor summary:hover,
+.answer-editor[open] summary { color: var(--signal); }
+.answer-editor summary:focus-visible {
+  outline: 2px solid var(--signal);
+  outline-offset: 2px;
+}
+
+.answer-editor .answer-form { margin-top: 4px; }
+
+.answer-form-actions {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 8px;
+}
+
+.answer-form-actions .btn { flex: 1 1 10rem; }
+
 .waiting { color: var(--muted); margin: 0; font-family: var(--mono); font-size: 0.8rem; }
 
 .auth-wrap {

templates/partials/_answer.html

@@ -5,6 +5,22 @@
     <h2>Answer</h2>
     <p class="byline">{{.Answer.AuthorName}} · 22 years, Bay Area</p>
     <p class="answer-body">{{.Answer.Body}}</p>
+    {{if isAdmin .User}}
+      <details class="answer-editor">
+        <summary>Edit answer</summary>
+        <form class="answer-form" method="post" action="/questions/{{.Answer.QuestionID}}/answer"
+          hx-post="/questions/{{.Answer.QuestionID}}/answer" hx-target="#answer-block" hx-swap="outerHTML">
+          <input type="hidden" name="_csrf" value="{{.CSRF}}">
+          <label for="answer-body">Edit answer</label>
+          <textarea id="answer-body" name="body" rows="8" required maxlength="12000">{{.Answer.Body}}</textarea>
+          <div class="answer-form-actions">
+            <button type="submit" class="btn btn-primary">Save answer</button>
+            <button type="reset" class="btn btn-ghost"
+              onclick="this.closest('details').removeAttribute('open')">Cancel</button>
+          </div>
+        </form>
+      </details>
+    {{end}}
   {{else}}
     <p class="waiting">No answer yet. Check back after the hunt.</p>
   {{end}}

templates/profile.html

@@ -25,6 +25,10 @@
       </div>
     </div>
 
+    <label for="email">Email</label>
+    <input id="email" name="email" type="email" required maxlength="254" autocomplete="email" value="{{.EmailVal}}">
+    <p class="hint">Required. We’ll email you when a plumber answers your question.</p>
+
     <label for="state">State</label>
     <select id="state" name="state">
       <option value=""{{if eq .StateVal ""}} selected{{end}}>Prefer not to say</option>

templates/question.html

@@ -23,12 +23,12 @@
     </div>
   </article>
   {{template "answer" .}}
-  {{if isAdmin .User}}
+  {{if and (isAdmin .User) (not .Answer)}}
     <form class="answer-form" method="post" action="/questions/{{.Question.ID}}/answer"
       hx-post="/questions/{{.Question.ID}}/answer" hx-target="#answer-block" hx-swap="outerHTML">
       <input type="hidden" name="_csrf" value="{{.CSRF}}">
-      <label for="answer-body">{{if .Answer}}Edit answer{{else}}Write the answer{{end}}</label>
-      <textarea id="answer-body" name="body" rows="8" required maxlength="12000">{{if .Answer}}{{.Answer.Body}}{{end}}</textarea>
+      <label for="answer-body">Write the answer</label>
+      <textarea id="answer-body" name="body" rows="8" required maxlength="12000"></textarea>
       <button type="submit" class="btn btn-primary">Save answer</button>
     </form>
   {{end}}

templates/register.html

@@ -9,6 +9,9 @@
     <label for="username">Username</label>
     <input id="username" name="username" type="text" required minlength="3" maxlength="20" pattern="[A-Za-z0-9_]+" autocomplete="username" autocapitalize="off" spellcheck="false" value="{{.Username}}">
     <p class="hint">3–20 letters, numbers, or underscores.</p>
+    <label for="email">Email</label>
+    <input id="email" name="email" type="email" required maxlength="254" autocomplete="email" value="{{.Email}}">
+    <p class="hint">We’ll email you when a plumber answers your question.</p>
     <label for="password">Password</label>
     <input id="password" name="password" type="password" required minlength="8" maxlength="72" autocomplete="new-password">
     <p class="hint">At least 8 characters (max 72 bytes).</p>