package web

import (
	"context"
	"database/sql"
	"fmt"
	"sort"
	"strings"
	"sync"
	"time"

	"github.com/google/uuid"

	"plumber/internal/pacific"
	"plumber/internal/store"
)

// memDB is an in-memory store.DB for tests.
type memDB struct {
	mu        sync.Mutex
	users     map[string]*store.User            // id -> user
	byName    map[string]string                 // username -> id
	questions map[string]*store.RankedQuestion  // id -> question
	votes     map[string]int                    // userID|questionID -> value
	answers   map[string]*store.Answer          // questionID -> answer
}

func newMemDB() *memDB {
	return &memDB{
		users:     map[string]*store.User{},
		byName:    map[string]string{},
		questions: map[string]*store.RankedQuestion{},
		votes:     map[string]int{},
		answers:   map[string]*store.Answer{},
	}
}

func voteKey(userID, questionID string) string {
	return userID + "|" + questionID
}

func (m *memDB) CreateUser(_ context.Context, username, passwordHash string, asAdmin bool) (*store.User, error) {
	m.mu.Lock()
	defer m.mu.Unlock()
	username = store.NormalizeUsername(username)
	if _, ok := m.byName[username]; ok {
		return nil, fmt.Errorf("username taken")
	}
	role := "user"
	if asAdmin {
		role = "admin"
	}
	u := &store.User{
		ID:           uuid.NewString(),
		Username:     username,
		Name:         username,
		Role:         role,
		PasswordHash: passwordHash,
		CreatedAt:    time.Now().UTC().Format(time.RFC3339),
	}
	m.users[u.ID] = u
	m.byName[username] = u.ID
	cp := *u
	return &cp, nil
}

func (m *memDB) UserByID(_ context.Context, id string) (*store.User, error) {
	m.mu.Lock()
	defer m.mu.Unlock()
	u, ok := m.users[id]
	if !ok {
		return nil, sql.ErrNoRows
	}
	cp := *u
	cp.PasswordHash = ""
	return &cp, nil
}

func (m *memDB) UserByUsername(_ context.Context, username string) (*store.User, error) {
	m.mu.Lock()
	defer m.mu.Unlock()
	id, ok := m.byName[store.NormalizeUsername(username)]
	if !ok {
		return nil, sql.ErrNoRows
	}
	cp := *m.users[id]
	return &cp, nil
}

func (m *memDB) CountAdmins(_ context.Context) (int, error) {
	m.mu.Lock()
	defer m.mu.Unlock()
	n := 0
	for _, u := range m.users {
		if u.Role == "admin" {
			n++
		}
	}
	return n, nil
}

func (m *memDB) ListUsers(_ context.Context) ([]store.User, error) {
	m.mu.Lock()
	defer m.mu.Unlock()
	out := make([]store.User, 0, len(m.users))
	for _, u := range m.users {
		cp := *u
		cp.PasswordHash = ""
		out = append(out, cp)
	}
	sort.Slice(out, func(i, j int) bool {
		return out[i].CreatedAt < out[j].CreatedAt
	})
	return out, nil
}

func (m *memDB) SetRole(_ context.Context, userID, role string) error {
	if role != "user" && role != "admin" {
		return fmt.Errorf("invalid role")
	}
	m.mu.Lock()
	defer m.mu.Unlock()
	u, ok := m.users[userID]
	if !ok {
		return sql.ErrNoRows
	}
	if u.Role == "admin" && role == "user" {
		n := 0
		for _, x := range m.users {
			if x.Role == "admin" {
				n++
			}
		}
		if n <= 1 {
			return store.ErrLastAdmin
		}
	}
	u.Role = role
	return nil
}

func (m *memDB) CreateQuestion(_ context.Context, authorID, title, body, city string) (*store.RankedQuestion, error) {
	m.mu.Lock()
	defer m.mu.Unlock()
	author, ok := m.users[authorID]
	if !ok {
		return nil, fmt.Errorf("unknown author")
	}
	q := &store.RankedQuestion{
		ID:         uuid.NewString(),
		AuthorID:   authorID,
		AuthorName: author.Name,
		Title:      strings.TrimSpace(title),
		Body:       strings.TrimSpace(body),
		City:       strings.TrimSpace(city),
		HuntDate:   pacific.Today(),
		CreatedAt:  time.Now().UTC().Format(time.RFC3339),
	}
	m.questions[q.ID] = q
	cp := *q
	return &cp, nil
}

func (m *memDB) rankedLocked(q *store.RankedQuestion, viewerID string) store.RankedQuestion {
	out := *q
	score := 0
	for k, v := range m.votes {
		_, qid, ok := strings.Cut(k, "|")
		if ok && qid == q.ID {
			score += v
		}
	}
	out.Score = score
	out.Answered = m.answers[q.ID] != nil
	if viewerID != "" {
		out.UserVote = m.votes[voteKey(viewerID, q.ID)]
	}
	if u, ok := m.users[q.AuthorID]; ok {
		out.AuthorName = u.Name
	}
	return out
}

func (m *memDB) ListHunt(_ context.Context, huntDate, viewerID string) ([]store.RankedQuestion, error) {
	m.mu.Lock()
	defer m.mu.Unlock()
	var out []store.RankedQuestion
	for _, q := range m.questions {
		if q.HuntDate != huntDate || q.Hidden {
			continue
		}
		out = append(out, m.rankedLocked(q, viewerID))
	}
	sort.Slice(out, func(i, j int) bool {
		if out[i].Score != out[j].Score {
			return out[i].Score > out[j].Score
		}
		return out[i].CreatedAt < out[j].CreatedAt
	})
	return out, nil
}

func (m *memDB) GetQuestion(_ context.Context, id, viewerID string) (*store.RankedQuestion, error) {
	m.mu.Lock()
	defer m.mu.Unlock()
	q, ok := m.questions[id]
	if !ok {
		return nil, sql.ErrNoRows
	}
	out := m.rankedLocked(q, viewerID)
	return &out, nil
}

func (m *memDB) Vote(_ context.Context, userID, questionID string, value int) error {
	if value != 1 && value != -1 {
		return fmt.Errorf("invalid vote")
	}
	m.mu.Lock()
	defer m.mu.Unlock()
	if _, ok := m.questions[questionID]; !ok {
		return fmt.Errorf("unknown question")
	}
	k := voteKey(userID, questionID)
	if cur, ok := m.votes[k]; ok && cur == value {
		delete(m.votes, k)
		return nil
	}
	m.votes[k] = value
	return nil
}

func (m *memDB) GetAnswer(_ context.Context, questionID string) (*store.Answer, error) {
	m.mu.Lock()
	defer m.mu.Unlock()
	a, ok := m.answers[questionID]
	if !ok {
		return nil, sql.ErrNoRows
	}
	cp := *a
	if u, ok := m.users[a.AuthorID]; ok {
		cp.AuthorName = u.Name
	}
	return &cp, nil
}

func (m *memDB) UpsertAnswer(_ context.Context, questionID, authorID, body string) error {
	m.mu.Lock()
	defer m.mu.Unlock()
	body = strings.TrimSpace(body)
	now := time.Now().UTC().Format(time.RFC3339)
	if existing, ok := m.answers[questionID]; ok {
		existing.Body = body
		existing.AuthorID = authorID
		existing.UpdatedAt = now
		return nil
	}
	m.answers[questionID] = &store.Answer{
		QuestionID: questionID,
		AuthorID:   authorID,
		Body:       body,
		CreatedAt:  now,
		UpdatedAt:  now,
	}
	return nil
}

func (m *memDB) HideQuestion(_ context.Context, id string) error {
	m.mu.Lock()
	defer m.mu.Unlock()
	q, ok := m.questions[id]
	if !ok {
		return sql.ErrNoRows
	}
	q.Hidden = true
	return nil
}

func (m *memDB) UpdateProfile(_ context.Context, userID, state, avatarURL string) error {
	m.mu.Lock()
	defer m.mu.Unlock()
	u, ok := m.users[userID]
	if !ok {
		return sql.ErrNoRows
	}
	u.State = state
	if avatarURL != "" {
		u.AvatarURL = avatarURL
	}
	return nil
}

func (m *memDB) ListQuestionsByAuthor(_ context.Context, authorID string) ([]store.RankedQuestion, error) {
	m.mu.Lock()
	defer m.mu.Unlock()
	var out []store.RankedQuestion
	for _, q := range m.questions {
		if q.AuthorID != authorID || q.Hidden {
			continue
		}
		out = append(out, m.rankedLocked(q, ""))
	}
	sort.Slice(out, func(i, j int) bool {
		return out[i].CreatedAt > out[j].CreatedAt
	})
	return out, nil
}

func (m *memDB) ListQuestionsAnsweredBy(_ context.Context, adminID string) ([]store.RankedQuestion, error) {
	m.mu.Lock()
	defer m.mu.Unlock()
	var out []store.RankedQuestion
	for qid, a := range m.answers {
		if a.AuthorID != adminID {
			continue
		}
		q, ok := m.questions[qid]
		if !ok || q.Hidden {
			continue
		}
		rq := m.rankedLocked(q, "")
		rq.Answered = true
		out = append(out, rq)
	}
	sort.Slice(out, func(i, j int) bool {
		return out[i].CreatedAt > out[j].CreatedAt
	})
	return out, nil
}

var _ store.DB = (*memDB)(nil)