Add an in-process post event bus.

cmd/server/main.go

@@ -17,6 +17,7 @@ import (
 
 	"plumber"
 	"plumber/internal/blob"
+	"plumber/internal/events"
 	"plumber/internal/mail"
 	"plumber/internal/store"
 	"plumber/internal/web"
@@ -34,7 +35,7 @@ func main() {
 	if err != nil {
 		log.Fatalf("mail: %v", err)
 	}
-	handler := newHandler(db, sessions, uploader, notifier)
+	handler := newHandler(db, sessions, uploader, notifier, events.New())
 	run(&http.Server{
 		Addr:              listenAddr(),
 		Handler:           handler,
@@ -58,13 +59,15 @@ func openDB() (*sql.DB, *store.SessionStore) {
 	return db, sessions
 }
 
-func newHandler(db *sql.DB, sessions *store.SessionStore, uploader blob.Uploader, notifier mail.Notifier) http.Handler {
+func newHandler(db *sql.DB, sessions *store.SessionStore, uploader blob.Uploader, notifier mail.Notifier, bus events.Publisher) 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,
+		Events:           bus,
+		BaseURL:          strings.TrimRight(strings.TrimSpace(os.Getenv("APP_BASE_URL")), "/"),
 	})
 	if err != nil {
 		log.Fatalf("server: %v", err)

internal/events/bus.go

@@ -0,0 +1,79 @@
+package events
+
+import (
+	"context"
+	"log"
+	"sync"
+)
+
+const defaultBuffer = 64
+
+// Publisher is the site-facing write side of the bus.
+type Publisher interface {
+	Publish(ctx context.Context, ev any)
+}
+
+// Bus is an in-process pub/sub with one worker and a bounded queue.
+type Bus struct {
+	ch     chan any
+	mu     sync.Mutex
+	subs   []func(context.Context, any)
+	closed sync.Once
+}
+
+// New starts a worker that delivers events to subscribers in publish order.
+func New() *Bus {
+	return newBus(defaultBuffer, true)
+}
+
+func newBus(buffer int, start bool) *Bus {
+	if buffer < 1 {
+		buffer = 1
+	}
+	b := &Bus{ch: make(chan any, buffer)}
+	if start {
+		go b.loop()
+	}
+	return b
+}
+
+// Publish enqueues ev. It never blocks the caller; a full buffer is dropped.
+func (b *Bus) Publish(_ context.Context, ev any) {
+	if b == nil {
+		return
+	}
+	select {
+	case b.ch <- ev:
+	default:
+		log.Printf("events: dropped %T", ev)
+	}
+}
+
+// Subscribe adds a handler. Handlers run serially on the worker.
+func (b *Bus) Subscribe(fn func(context.Context, any)) {
+	if b == nil || fn == nil {
+		return
+	}
+	b.mu.Lock()
+	b.subs = append(b.subs, fn)
+	b.mu.Unlock()
+}
+
+func (b *Bus) loop() {
+	for ev := range b.ch {
+		b.mu.Lock()
+		subs := append([]func(context.Context, any){}, b.subs...)
+		b.mu.Unlock()
+		for _, fn := range subs {
+			fn(context.Background(), ev)
+		}
+	}
+}
+
+// Close stops the worker. Safe to call more than once.
+func (b *Bus) Close() {
+	if b == nil {
+		return
+	}
+	b.closed.Do(func() { close(b.ch) })
+}

internal/events/bus_test.go

@@ -0,0 +1,104 @@
+package events
+
+import (
+	"context"
+	"sync"
+	"testing"
+	"time"
+)
+
+func TestPermalink(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		base, root, post, want string
+	}{
+		{"", "root-1", "post-2", "/questions/root-1#post-post-2"},
+		{"https://www.askaplumberfirst.com/", "root-1", "post-2", "https://www.askaplumberfirst.com/questions/root-1#post-post-2"},
+		{"https://www.askaplumberfirst.com", "a b", "c/d", "https://www.askaplumberfirst.com/questions/a%20b#post-c%2Fd"},
+	}
+	for _, tc := range tests {
+		if got := Permalink(tc.base, tc.root, tc.post); got != tc.want {
+			t.Fatalf("Permalink(%q, %q, %q) = %q, want %q", tc.base, tc.root, tc.post, got, tc.want)
+		}
+	}
+}
+
+func TestNopAndRecording(t *testing.T) {
+	t.Parallel()
+
+	Nop{}.Publish(context.Background(), PostCreated{})
+
+	rec := &Recording{}
+	rec.Publish(context.Background(), PostCreated{PostEvent: PostEvent{PostID: "a"}})
+	rec.Publish(context.Background(), PostUpdated{PostEvent: PostEvent{PostID: "b"}})
+	if rec.Len() != 2 {
+		t.Fatalf("len = %d", rec.Len())
+	}
+	got := rec.Snapshot()
+	created, ok := got[0].(PostCreated)
+	if !ok || created.PostID != "a" {
+		t.Fatalf("first = %#v", got[0])
+	}
+	updated, ok := got[1].(PostUpdated)
+	if !ok || updated.PostID != "b" {
+		t.Fatalf("second = %#v", got[1])
+	}
+}
+
+func TestBusDeliversInOrder(t *testing.T) {
+	t.Parallel()
+
+	bus := New()
+	defer bus.Close()
+
+	var mu sync.Mutex
+	var got []string
+	done := make(chan struct{})
+	bus.Subscribe(func(_ context.Context, ev any) {
+		mu.Lock()
+		got = append(got, ev.(string))
+		if len(got) == 3 {
+			close(done)
+		}
+		mu.Unlock()
+	})
+
+	ctx := context.Background()
+	bus.Publish(ctx, "one")
+	bus.Publish(ctx, "two")
+	bus.Publish(ctx, "three")
+
+	select {
+	case <-done:
+	case <-time.After(time.Second):
+		t.Fatal("timed out waiting for events")
+	}
+	mu.Lock()
+	defer mu.Unlock()
+	if len(got) != 3 || got[0] != "one" || got[1] != "two" || got[2] != "three" {
+		t.Fatalf("got %v", got)
+	}
+}
+
+func TestBusDropsWhenFull(t *testing.T) {
+	t.Parallel()
+
+	bus := newBus(1, false)
+	bus.Publish(context.Background(), "kept")
+	bus.Publish(context.Background(), "dropped")
+
+	select {
+	case ev := <-bus.ch:
+		if ev != "kept" {
+			t.Fatalf("got %v", ev)
+		}
+	default:
+		t.Fatal("expected buffered event")
+	}
+	select {
+	case ev := <-bus.ch:
+		t.Fatalf("unexpected extra event %v", ev)
+	default:
+	}
+}

internal/events/event.go

@@ -0,0 +1,47 @@
+package events
+
+import (
+	"net/url"
+	"strings"
+)
+
+// Image is a public photo already attached to a site post.
+type Image struct {
+	URL         string
+	Description string
+}
+
+// PostEvent is a Discord-free snapshot of a site post after a successful write.
+type PostEvent struct {
+	PostID     string
+	RootID     string
+	ParentID   string
+	Title      string
+	Body       string
+	City       string
+	AuthorID   string
+	AuthorName string
+	AuthorRole string
+	Images     []Image
+	Permalink  string
+}
+
+// PostCreated is emitted after a successful site create.
+type PostCreated struct {
+	PostEvent
+}
+
+// PostUpdated is emitted after a successful site edit.
+type PostUpdated struct {
+	PostEvent
+}
+
+// Permalink builds /questions/{root}#post-{id}, prefixed by baseURL when set.
+func Permalink(baseURL, rootID, postID string) string {
+	path := "/questions/" + url.PathEscape(rootID) + "#post-" + url.PathEscape(postID)
+	base := strings.TrimRight(strings.TrimSpace(baseURL), "/")
+	if base == "" {
+		return path
+	}
+	return base + path
+}

internal/events/nop.go

@@ -0,0 +1,9 @@
+package events
+
+import "context"
+
+// Nop is a Publisher used when nothing is subscribed.
+type Nop struct{}
+
+// Publish discards ev.
+func (Nop) Publish(context.Context, any) {}

internal/events/recording.go

@@ -0,0 +1,44 @@
+package events
+
+import (
+	"context"
+	"sync"
+)
+
+// Recording is a test Publisher that records events synchronously.
+type Recording struct {
+	mu  sync.Mutex
+	evs []any
+}
+
+// Publish appends ev.
+func (r *Recording) Publish(_ context.Context, ev any) {
+	if r == nil {
+		return
+	}
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	r.evs = append(r.evs, ev)
+}
+
+// Len returns the number of recorded events.
+func (r *Recording) Len() int {
+	if r == nil {
+		return 0
+	}
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	return len(r.evs)
+}
+
+// Snapshot returns a copy of recorded events.
+func (r *Recording) Snapshot() []any {
+	if r == nil {
+		return nil
+	}
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	out := make([]any, len(r.evs))
+	copy(out, r.evs)
+	return out
+}

internal/web/events.go

@@ -0,0 +1,65 @@
+package web
+
+import (
+	"context"
+
+	"plumber/internal/events"
+	"plumber/internal/store"
+)
+
+func (s *Server) publishPostCreated(post, root *store.Post, author *store.User) {
+	s.publishPost(events.PostCreated{PostEvent: s.postEvent(post, root, author)}, root)
+}
+
+func (s *Server) publishPostUpdated(post, root *store.Post, author *store.User) {
+	s.publishPost(events.PostUpdated{PostEvent: s.postEvent(post, root, author)}, root)
+}
+
+func (s *Server) publishPost(ev any, root *store.Post) {
+	if root != nil && root.PostState == store.PostStateHidden {
+		return
+	}
+	s.cfg.Events.Publish(context.Background(), ev)
+}
+
+func (s *Server) postEvent(post, root *store.Post, author *store.User) events.PostEvent {
+	if post == nil {
+		return events.PostEvent{}
+	}
+	rootID := post.ID
+	if root != nil {
+		rootID = root.ID
+	}
+	ev := events.PostEvent{
+		PostID:     post.ID,
+		RootID:     rootID,
+		Title:      post.Title,
+		Body:       post.Body,
+		City:       post.City,
+		AuthorID:   post.AuthorID,
+		AuthorName: post.AuthorName,
+		AuthorRole: string(post.AuthorRole),
+		Permalink:  events.Permalink(s.cfg.BaseURL, rootID, post.ID),
+	}
+	if post.ParentID != nil {
+		ev.ParentID = *post.ParentID
+	}
+	if author != nil {
+		if ev.AuthorName == "" {
+			ev.AuthorName = author.Name
+		}
+		if ev.AuthorRole == "" {
+			ev.AuthorRole = string(author.Role)
+		}
+	}
+	if n := len(post.Images); n > 0 {
+		ev.Images = make([]events.Image, 0, n)
+		for _, img := range post.Images {
+			ev.Images = append(ev.Images, events.Image{
+				URL:         img.PublicURL,
+				Description: img.Description,
+			})
+		}
+	}
+	return ev
+}

internal/web/events_test.go

@@ -0,0 +1,238 @@
+package web
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/url"
+	"strings"
+	"testing"
+
+	"plumber/internal/events"
+	"plumber/internal/pacific"
+	"plumber/internal/store"
+)
+
+func TestPostHandlersPublishEvents(t *testing.T) {
+	t.Parallel()
+
+	rec := &events.Recording{}
+	srv, mem := newTestServer(t, Config{
+		Events:  rec,
+		BaseURL: "https://www.askaplumberfirst.com",
+	})
+	handler := srv.Handler()
+	homeowner := seedUser(t, mem, uniq("homeowner"), "hunter22", store.RoleUser)
+	admin := seedUser(t, mem, uniq("admin"), "hunter22", store.RoleAdmin)
+	homeownerCookies := loginUser(t, handler, homeowner.Username, "hunter22")
+	adminCookies := loginUser(t, handler, admin.Username, "hunter22")
+	homeownerCSRF := csrfForCookies(t, handler, homeownerCookies)
+	adminCSRF := csrfForCookies(t, handler, adminCookies)
+
+	submit := postForm(handler, "/submit", url.Values{
+		"_csrf": {homeownerCSRF},
+		"title": {"Leaky sink"},
+		"body":  {"Water under the cabinet."},
+		"city":  {"Oakland"},
+	}, homeownerCookies)
+	if submit.Code != http.StatusSeeOther {
+		t.Fatalf("submit status = %d: %s", submit.Code, submit.Body.String())
+	}
+
+	create := postForm(handler, "/posts", url.Values{
+		"_csrf": {homeownerCSRF},
+		"title": {"Second question"},
+		"body":  {"Another leak."},
+		"city":  {"Berkeley"},
+	}, homeownerCookies)
+	if create.Code != http.StatusSeeOther {
+		t.Fatalf("create status = %d: %s", create.Code, create.Body.String())
+	}
+
+	roots, err := mem.ListRootPosts(context.Background(), pacific.Today(), homeowner.ID)
+	if err != nil || len(roots) != 2 {
+		t.Fatalf("roots = %+v, %v", roots, err)
+	}
+	var submitRoot, createRoot store.Post
+	for _, root := range roots {
+		switch root.Title {
+		case "Leaky sink":
+			submitRoot = root
+		case "Second question":
+			createRoot = root
+		}
+	}
+	if submitRoot.ID == "" || createRoot.ID == "" {
+		t.Fatalf("missing created roots: %+v", roots)
+	}
+
+	reply := postForm(handler, "/posts", url.Values{
+		"_csrf":     {adminCSRF},
+		"parent_id": {createRoot.ID},
+		"body":      {"Replace the cartridge."},
+	}, adminCookies)
+	if reply.Code != http.StatusSeeOther {
+		t.Fatalf("reply status = %d: %s", reply.Code, reply.Body.String())
+	}
+	thread, err := mem.GetPostThread(context.Background(), createRoot.ID)
+	if err != nil || len(thread.Replies) != 1 {
+		t.Fatalf("thread = %+v, %v", thread, err)
+	}
+	adminReply := thread.Replies[0]
+
+	edit := postForm(handler, "/posts/"+createRoot.ID+"/edit", url.Values{
+		"_csrf": {homeownerCSRF},
+		"body":  {"Updated leak description."},
+	}, homeownerCookies)
+	if edit.Code != http.StatusSeeOther {
+		t.Fatalf("edit status = %d: %s", edit.Code, edit.Body.String())
+	}
+
+	empty := postForm(handler, "/posts", url.Values{
+		"_csrf": {homeownerCSRF},
+		"title": {"Missing body"},
+	}, homeownerCookies)
+	if empty.Code != http.StatusBadRequest {
+		t.Fatalf("empty body status = %d, want 400", empty.Code)
+	}
+
+	hidden := &store.Post{
+		AuthorID:  homeowner.ID,
+		Title:     "Hidden thread",
+		Body:      "Not public.",
+		PostDate:  pacific.Today(),
+		PostState: store.PostStateHidden,
+	}
+	if err := mem.CreatePost(context.Background(), hidden); err != nil {
+		t.Fatal(err)
+	}
+	hiddenReply := postForm(handler, "/posts", url.Values{
+		"_csrf":     {homeownerCSRF},
+		"parent_id": {hidden.ID},
+		"body":      {"Should not publish."},
+	}, homeownerCookies)
+	if hiddenReply.Code != http.StatusNotFound {
+		t.Fatalf("hidden reply status = %d, want 404", hiddenReply.Code)
+	}
+	hiddenEdit := postForm(handler, "/posts/"+hidden.ID+"/edit", url.Values{
+		"_csrf": {homeownerCSRF},
+		"body":  {"Still hidden."},
+	}, homeownerCookies)
+	if hiddenEdit.Code != http.StatusSeeOther {
+		t.Fatalf("hidden edit status = %d: %s", hiddenEdit.Code, hiddenEdit.Body.String())
+	}
+
+	got := rec.Snapshot()
+	if len(got) != 4 {
+		t.Fatalf("published %d events, want 4: %#v", len(got), got)
+	}
+
+	submitEv, ok := got[0].(events.PostCreated)
+	if !ok {
+		t.Fatalf("first event %T, want PostCreated", got[0])
+	}
+	assertPostEvent(t, submitEv.PostEvent, events.PostEvent{
+		PostID:     submitRoot.ID,
+		RootID:     submitRoot.ID,
+		Title:      "Leaky sink",
+		Body:       "Water under the cabinet.",
+		City:       "Oakland",
+		AuthorID:   homeowner.ID,
+		AuthorName: homeowner.Name,
+		AuthorRole: string(store.RoleUser),
+		Permalink:  "https://www.askaplumberfirst.com/questions/" + submitRoot.ID + "#post-" + submitRoot.ID,
+	})
+
+	createEv, ok := got[1].(events.PostCreated)
+	if !ok {
+		t.Fatalf("second event %T, want PostCreated", got[1])
+	}
+	assertPostEvent(t, createEv.PostEvent, events.PostEvent{
+		PostID:     createRoot.ID,
+		RootID:     createRoot.ID,
+		Title:      "Second question",
+		Body:       "Another leak.",
+		City:       "Berkeley",
+		AuthorID:   homeowner.ID,
+		AuthorName: homeowner.Name,
+		AuthorRole: string(store.RoleUser),
+		Permalink:  "https://www.askaplumberfirst.com/questions/" + createRoot.ID + "#post-" + createRoot.ID,
+	})
+
+	replyEv, ok := got[2].(events.PostCreated)
+	if !ok {
+		t.Fatalf("third event %T, want PostCreated", got[2])
+	}
+	assertPostEvent(t, replyEv.PostEvent, events.PostEvent{
+		PostID:     adminReply.ID,
+		RootID:     createRoot.ID,
+		ParentID:   createRoot.ID,
+		Body:       "Replace the cartridge.",
+		AuthorID:   admin.ID,
+		AuthorName: admin.Name,
+		AuthorRole: string(store.RoleAdmin),
+		Permalink:  "https://www.askaplumberfirst.com/questions/" + createRoot.ID + "#post-" + adminReply.ID,
+	})
+
+	editEv, ok := got[3].(events.PostUpdated)
+	if !ok {
+		t.Fatalf("fourth event %T, want PostUpdated", got[3])
+	}
+	assertPostEvent(t, editEv.PostEvent, events.PostEvent{
+		PostID:     createRoot.ID,
+		RootID:     createRoot.ID,
+		Title:      "Second question",
+		Body:       "Updated leak description.",
+		City:       "Berkeley",
+		AuthorID:   homeowner.ID,
+		AuthorName: homeowner.Name,
+		AuthorRole: string(store.RoleUser),
+		Permalink:  "https://www.askaplumberfirst.com/questions/" + createRoot.ID + "#post-" + createRoot.ID,
+	})
+
+	for i, ev := range got {
+		raw, err := json.Marshal(ev)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if strings.Contains(strings.ToLower(string(raw)), "discord") {
+			t.Fatalf("event %d contains discord fields: %s", i, raw)
+		}
+	}
+}
+
+func TestStoreCreateDoesNotPublish(t *testing.T) {
+	t.Parallel()
+
+	rec := &events.Recording{}
+	_, mem := newTestServer(t, Config{Events: rec})
+	homeowner := seedUser(t, mem, uniq("homeowner"), "hunter22", store.RoleUser)
+	if err := mem.CreatePost(context.Background(), &store.Post{
+		AuthorID: homeowner.ID,
+		Title:    "Direct write",
+		Body:     "No handler.",
+		PostDate: pacific.Today(),
+	}); err != nil {
+		t.Fatal(err)
+	}
+	if rec.Len() != 0 {
+		t.Fatalf("store.CreatePost published %d events", rec.Len())
+	}
+}
+
+func assertPostEvent(t *testing.T, got, want events.PostEvent) {
+	t.Helper()
+	if got.PostID != want.PostID ||
+		got.RootID != want.RootID ||
+		got.ParentID != want.ParentID ||
+		got.Title != want.Title ||
+		got.Body != want.Body ||
+		got.City != want.City ||
+		got.AuthorID != want.AuthorID ||
+		got.AuthorName != want.AuthorName ||
+		got.AuthorRole != want.AuthorRole ||
+		got.Permalink != want.Permalink ||
+		len(got.Images) != 0 {
+		t.Fatalf("event = %+v, want %+v", got, want)
+	}
+}

internal/web/posts.go

@@ -85,6 +85,7 @@ func (s *Server) handleCreatePost(w http.ResponseWriter, r *http.Request) {
 	if parent != nil {
 		s.notifyPostReply(parent, root, post, user)
 	}
+	s.publishPostCreated(post, root, user)
 	http.Redirect(
 		w,
 		r,
@@ -190,6 +191,7 @@ func (s *Server) handleEditPost(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "could not save post", http.StatusInternalServerError)
 		return
 	}
+	s.publishPostUpdated(post, root, nil)
 	http.Redirect(
 		w,
 		r,

internal/web/server.go

@@ -20,6 +20,7 @@ import (
 	"github.com/go-chi/chi/v5/middleware"
 
 	"plumber/internal/blob"
+	"plumber/internal/events"
 	"plumber/internal/geo"
 	"plumber/internal/mail"
 	"plumber/internal/pacific"
@@ -35,6 +36,8 @@ type Config struct {
 	TrustedProxies []*net.IPNet
 	Blob           blob.Uploader
 	Mail           mail.Notifier
+	Events         events.Publisher
+	BaseURL        string
 }
 
 type Server struct {
@@ -110,6 +113,9 @@ func New(st store.Store, sessionStore scs.Store, templateFS fs.FS, staticFS fs.F
 	if cfg.Mail == nil {
 		cfg.Mail = mail.Nop{}
 	}
+	if cfg.Events == nil {
+		cfg.Events = events.Nop{}
+	}
 	funcMap := template.FuncMap{
 		"voteCtx": func(user *store.User, csrf, view, date string, post *store.Post) voteCtx {
 			return voteCtx{User: user, CSRF: csrf, View: view, Date: date, Post: post}
@@ -371,6 +377,7 @@ func (s *Server) handleSubmit(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "could not save question", http.StatusInternalServerError)
 		return
 	}
+	s.publishPostCreated(post, post, u)
 	http.Redirect(w, r, "/questions/"+url.PathEscape(post.ID), http.StatusSeeOther)
 }