linearvoid/backend/chat/src/main.go

package main

import (
	"context"
	"crypto/rand"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"sort"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/gorilla/websocket"
	"github.com/redis/go-redis/v9"
	"gorm.io/driver/postgres"
	"gorm.io/driver/sqlite"
	"gorm.io/gorm"
)

// Config from environment (ADR-003 and ADR-007)
var (
	redisClient *redis.Client
	db          *gorm.DB
	upgrader    = websocket.Upgrader{
		CheckOrigin: func(r *http.Request) bool { return true },
	}
	clients = make(map[*websocket.Conn]bool)
	mutex   = sync.Mutex{}
	authSessions   = map[string]time.Time{}
	authSessionsMu = sync.Mutex{}
)

// Message represents a chat message (persisted in SQLite per ADR-006)
type Message struct {
	ID        uint      `gorm:"primarykey" json:"id"`
	Room      string    `json:"room"`
	Username  string    `json:"username"`
	Text      string    `json:"text"`
	Timestamp time.Time `json:"timestamp"`
	Type      string    `json:"type"` // "public", "private", "system", "moderation"
}

// ModerationLog for audit trail (immutable per ADR-005)
type ModerationLog struct {
	ID        uint      `gorm:"primarykey" json:"id"`
	Action    string    `json:"action"` // "mute", "ban", "delete", "timeout"
	Target    string    `json:"target"`
	Moderator string    `json:"moderator"`
	Reason    string    `json:"reason"`
	Timestamp time.Time `json:"timestamp"`
}

// Presence tracks online users per room (using Redis per ADR-007)
type Presence struct {
	Username string `json:"username"`
	Room     string `json:"room"`
	Online   bool   `json:"online"`
}

type AdminOverview struct {
	Viewers           int    `json:"viewers"`
	StoredMessages    int64  `json:"storedMessages"`
	ModerationActions int64  `json:"moderationActions"`
	RedisEnabled      bool   `json:"redisEnabled"`
	RedisClients      int    `json:"redisClients"`
	RedisMemoryUsed   string `json:"redisMemoryUsed"`
	DatabaseDriver    string `json:"databaseDriver"`
	GeneratedAt       string `json:"generatedAt"`
}

type PlaylistPayload struct {
	Content string `json:"content"`
}

type ModerationActionPayload struct {
	Action    string `json:"action"`
	Target    string `json:"target"`
	Moderator string `json:"moderator"`
	Reason    string `json:"reason"`
	Room      string `json:"room"`
}

type ModerationLogsResponse struct {
	Logs []ModerationLog `json:"logs"`
}

type RoomAnalytics struct {
	Room         string `json:"room"`
	MessageCount int64  `json:"messageCount"`
}

type AdminAnalytics struct {
	TotalMessages       int64           `json:"totalMessages"`
	MessagesLast24Hours int64           `json:"messagesLast24Hours"`
	DistinctRooms       int64           `json:"distinctRooms"`
	ModerationActions   int64           `json:"moderationActions"`
	TopRooms            []RoomAnalytics `json:"topRooms"`
	GeneratedAt         string          `json:"generatedAt"`
}

type ServiceHealth struct {
	Name    string `json:"name"`
	Status  string `json:"status"`
	Detail  string `json:"detail"`
	Checked string `json:"checked"`
}

type AdminSystemSummary struct {
	DatabaseDriver  string          `json:"databaseDriver"`
	PlaylistPath    string          `json:"playlistPath"`
	PlaylistExists  bool            `json:"playlistExists"`
	RedisEnabled    bool            `json:"redisEnabled"`
	RedisMemoryUsed string          `json:"redisMemoryUsed"`
	Services        []ServiceHealth `json:"services"`
	GeneratedAt     string          `json:"generatedAt"`
}

type ActiveUser struct {
	Username string `json:"username"`
	Room     string `json:"room"`
	Online   bool   `json:"online"`
}

type AdminUsersResponse struct {
	Users       []ActiveUser `json:"users"`
	RedisEnabled bool       `json:"redisEnabled"`
	GeneratedAt string      `json:"generatedAt"`
}

type ScheduleEntry struct {
	Index int    `json:"index"`
	Path  string `json:"path"`
	Label string `json:"label"`
}

type AdminScheduleResponse struct {
	Entries     []ScheduleEntry `json:"entries"`
	GeneratedAt string          `json:"generatedAt"`
}

type MediaFileEntry struct {
	Name       string `json:"name"`
	Size       int64  `json:"size"`
	ModifiedAt string `json:"modifiedAt"`
}

type AdminMediaResponse struct {
	Files       []MediaFileEntry `json:"files"`
	GeneratedAt string           `json:"generatedAt"`
}

type AdminLoginPayload struct {
	Username string `json:"username"`
	Password string `json:"password"`
}

type AdminSessionResponse struct {
	Authenticated bool   `json:"authenticated"`
	Username      string `json:"username,omitempty"`
}

var databaseDriverName = "sqlite"

const adminSessionCookieName = "linearvoid_admin_session"

// initRedis initializes Redis for presence, rate limiting, and pub/sub (ADR-007)
func initRedis() {
	redisAddress := os.Getenv("REDIS_URL")
	if redisAddress == "" {
		redisAddress = "redis:6379"
	}

	var options *redis.Options
	var err error
	if strings.Contains(redisAddress, "://") {
		options, err = redis.ParseURL(redisAddress)
		if err != nil {
			log.Printf("Redis configuration warning: %v (rate limiting and presence will be disabled)", err)
			redisClient = nil
			return
		}
	} else {
		options = &redis.Options{Addr: redisAddress}
	}

	redisClient = redis.NewClient(options)
	if err := redisClient.Ping(context.Background()).Err(); err != nil {
		log.Printf("Redis connection warning: %v (rate limiting and presence will be disabled)", err)
		redisClient = nil
	} else {
		log.Println("Redis connected successfully (presence, rate limiting, pub/sub enabled)")
	}
}

// initDB initializes SQLite for message history and moderation audit log (ADR-006)
func initDB() {
	var err error
	databaseURL := strings.TrimSpace(os.Getenv("DATABASE_URL"))
	driverName := "sqlite"

	switch {
	case databaseURL == "":
		db, err = gorm.Open(sqlite.Open("chat.db"), &gorm.Config{})
	case strings.HasPrefix(databaseURL, "sqlite://"):
		sqlitePath := strings.TrimPrefix(databaseURL, "sqlite://")
		if sqlitePath == "" {
			sqlitePath = "chat.db"
		}
		db, err = gorm.Open(sqlite.Open(sqlitePath), &gorm.Config{})
	case strings.HasPrefix(databaseURL, "postgres://") || strings.HasPrefix(databaseURL, "postgresql://"):
		driverName = "postgres"
		db, err = gorm.Open(postgres.Open(databaseURL), &gorm.Config{})
	default:
		log.Fatalf("Unsupported DATABASE_URL scheme: %s", databaseURL)
	}

	if err != nil {
		log.Fatalf("Failed to connect to %s database: %v", driverName, err)
	}

	databaseDriverName = driverName
	db.AutoMigrate(&Message{}, &ModerationLog{})
	log.Printf("%s database initialized (chat history and moderation log)", strings.Title(driverName))
}

func parseRedisInfoValue(info, key string) string {
	prefix := key + ":"
	for _, line := range strings.Split(info, "\n") {
		line = strings.TrimSpace(line)
		if strings.HasPrefix(line, prefix) {
			return strings.TrimSpace(strings.TrimPrefix(line, prefix))
		}
	}
	return ""
}

func getAdminOverview() AdminOverview {
	overview := AdminOverview{
		RedisEnabled:    redisClient != nil,
		RedisMemoryUsed: "unavailable",
		DatabaseDriver:  databaseDriverName,
		GeneratedAt:     time.Now().UTC().Format(time.RFC3339),
	}

	mutex.Lock()
	overview.Viewers = len(clients)
	mutex.Unlock()

	if db != nil {
		db.Model(&Message{}).Count(&overview.StoredMessages)
		db.Model(&ModerationLog{}).Count(&overview.ModerationActions)
	}

	if redisClient != nil {
		ctx := context.Background()
		if info, err := redisClient.Info(ctx, "clients", "memory").Result(); err == nil {
			if value := parseRedisInfoValue(info, "connected_clients"); value != "" {
				if count, convErr := strconv.Atoi(value); convErr == nil {
					overview.RedisClients = count
				}
			}
			if value := parseRedisInfoValue(info, "used_memory_human"); value != "" {
				overview.RedisMemoryUsed = value
			}
		}
	}

	return overview
}

func handleAdminLogin(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}

	var payload AdminLoginPayload
	if err := json.NewDecoder(r.Body).Decode(&payload); err != nil {
		http.Error(w, fmt.Sprintf("invalid request body: %v", err), http.StatusBadRequest)
		return
	}

	if payload.Username != getAdminUsername() || payload.Password != getAdminPassword() {
		http.Error(w, "invalid credentials", http.StatusUnauthorized)
		return
	}

	token, err := generateSessionToken()
	if err != nil {
		http.Error(w, fmt.Sprintf("failed to create session: %v", err), http.StatusInternalServerError)
		return
	}

	expiresAt := time.Now().Add(getAdminSessionTTL())
	authSessionsMu.Lock()
	authSessions[token] = expiresAt
	authSessionsMu.Unlock()
	setAdminSessionCookie(w, r, token, expiresAt)

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(AdminSessionResponse{Authenticated: true, Username: getAdminUsername()})
}

func handleAdminLogout(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}

	if cookie, err := r.Cookie(adminSessionCookieName); err == nil {
		authSessionsMu.Lock()
		delete(authSessions, cookie.Value)
		authSessionsMu.Unlock()
	}
	clearAdminSessionCookie(w, r)

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(AdminSessionResponse{Authenticated: false})
}

func handleAdminSession(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}

	if !validateAdminSession(r) {
		http.Error(w, "unauthorized", http.StatusUnauthorized)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(AdminSessionResponse{Authenticated: true, Username: getAdminUsername()})
}

func handleAdminOverview(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(getAdminOverview())
}

func getPlaylistPath() string {
	playlistPath := strings.TrimSpace(os.Getenv("PLAYLIST_PATH"))
	if playlistPath == "" {
		playlistPath = "/app/playlist/playlist.txt"
	}
	return playlistPath
}

func getMediaDir() string {
	mediaDir := strings.TrimSpace(os.Getenv("MEDIA_DIR"))
	if mediaDir == "" {
		mediaDir = "/app/media"
	}
	return mediaDir
}

func getAdminUsername() string {
	username := strings.TrimSpace(os.Getenv("ADMIN_USERNAME"))
	if username == "" {
		username = "admin"
	}
	return username
}

func getAdminPassword() string {
	password := strings.TrimSpace(os.Getenv("ADMIN_PASSWORD"))
	if password == "" {
		password = "admin"
	}
	return password
}

func getAdminSessionTTL() time.Duration {
	if rawHours := strings.TrimSpace(os.Getenv("ADMIN_SESSION_TTL_HOURS")); rawHours != "" {
		if hours, err := strconv.Atoi(rawHours); err == nil && hours > 0 {
			return time.Duration(hours) * time.Hour
		}
	}
	return 12 * time.Hour
}

func generateSessionToken() (string, error) {
	buf := make([]byte, 32)
	if _, err := rand.Read(buf); err != nil {
		return "", err
	}
	return hex.EncodeToString(buf), nil
}

func sessionCookieSecure(r *http.Request) bool {
	if forwardedProto := strings.TrimSpace(r.Header.Get("X-Forwarded-Proto")); forwardedProto != "" {
		return strings.EqualFold(forwardedProto, "https")
	}
	return r.TLS != nil
}

func setAdminSessionCookie(w http.ResponseWriter, r *http.Request, token string, expiresAt time.Time) {
	http.SetCookie(w, &http.Cookie{
		Name:     adminSessionCookieName,
		Value:    token,
		Path:     "/",
		HttpOnly: true,
		SameSite: http.SameSiteStrictMode,
		Secure:   sessionCookieSecure(r),
		Expires:  expiresAt,
		MaxAge:   int(time.Until(expiresAt).Seconds()),
	})
}

func clearAdminSessionCookie(w http.ResponseWriter, r *http.Request) {
	http.SetCookie(w, &http.Cookie{
		Name:     adminSessionCookieName,
		Value:    "",
		Path:     "/",
		HttpOnly: true,
		SameSite: http.SameSiteStrictMode,
		Secure:   sessionCookieSecure(r),
		Expires:  time.Unix(0, 0),
		MaxAge:   -1,
	})
}

func validateAdminSession(r *http.Request) bool {
	cookie, err := r.Cookie(adminSessionCookieName)
	if err != nil || cookie.Value == "" {
		return false
	}

	authSessionsMu.Lock()
	defer authSessionsMu.Unlock()

	expiresAt, ok := authSessions[cookie.Value]
	if !ok {
		return false
	}
	if time.Now().After(expiresAt) {
		delete(authSessions, cookie.Value)
		return false
	}

	return true
}

func requireAdminAuth(next http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if !validateAdminSession(r) {
			http.Error(w, "unauthorized", http.StatusUnauthorized)
			return
		}
		next(w, r)
	}
}

func parsePlaylistEntries(content string) []ScheduleEntry {
	entries := []ScheduleEntry{}
	lines := strings.Split(content, "\n")
	for _, rawLine := range lines {
		line := strings.TrimSpace(rawLine)
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}

		if strings.HasPrefix(line, "file ") {
			line = strings.TrimSpace(strings.TrimPrefix(line, "file "))
			line = strings.Trim(line, "'\"")
		}

		entries = append(entries, ScheduleEntry{
			Index: len(entries) + 1,
			Path:  line,
			Label: filepath.Base(line),
		})
	}

	return entries
}

func handleAdminPlaylist(w http.ResponseWriter, r *http.Request) {
	playlistPath := getPlaylistPath()

	switch r.Method {
	case http.MethodGet:
		content, err := os.ReadFile(playlistPath)
		if err != nil {
			http.Error(w, fmt.Sprintf("failed to read playlist: %v", err), http.StatusInternalServerError)
			return
		}

		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode(PlaylistPayload{Content: string(content)})
	case http.MethodPut:
		var payload PlaylistPayload
		if err := json.NewDecoder(r.Body).Decode(&payload); err != nil {
			http.Error(w, fmt.Sprintf("invalid request body: %v", err), http.StatusBadRequest)
			return
		}

		if err := os.MkdirAll(filepath.Dir(playlistPath), 0o755); err != nil {
			http.Error(w, fmt.Sprintf("failed to ensure playlist directory: %v", err), http.StatusInternalServerError)
			return
		}

		content := payload.Content
		if content != "" && !strings.HasSuffix(content, "\n") {
			content += "\n"
		}

		if err := os.WriteFile(playlistPath, []byte(content), 0o644); err != nil {
			http.Error(w, fmt.Sprintf("failed to save playlist: %v", err), http.StatusInternalServerError)
			return
		}

		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode(PlaylistPayload{Content: content})
	default:
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
	}
}

func handleAdminSchedule(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}

	content, err := os.ReadFile(getPlaylistPath())
	if err != nil {
		http.Error(w, fmt.Sprintf("failed to read schedule playlist: %v", err), http.StatusInternalServerError)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(AdminScheduleResponse{
		Entries:     parsePlaylistEntries(string(content)),
		GeneratedAt: time.Now().UTC().Format(time.RFC3339),
	})
}

func handleAdminModerationLogs(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}

	limit := 50
	if rawLimit := strings.TrimSpace(r.URL.Query().Get("limit")); rawLimit != "" {
		parsedLimit, err := strconv.Atoi(rawLimit)
		if err != nil || parsedLimit <= 0 {
			http.Error(w, "invalid limit", http.StatusBadRequest)
			return
		}
		if parsedLimit > 200 {
			parsedLimit = 200
		}
		limit = parsedLimit
	}

	var logs []ModerationLog
	if err := db.Order("timestamp desc").Limit(limit).Find(&logs).Error; err != nil {
		http.Error(w, fmt.Sprintf("failed to load moderation logs: %v", err), http.StatusInternalServerError)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(ModerationLogsResponse{Logs: logs})
}

func handleAdminModerationAction(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}

	var payload ModerationActionPayload
	if err := json.NewDecoder(r.Body).Decode(&payload); err != nil {
		http.Error(w, fmt.Sprintf("invalid request body: %v", err), http.StatusBadRequest)
		return
	}

	payload.Action = strings.TrimSpace(payload.Action)
	payload.Target = strings.TrimSpace(payload.Target)
	payload.Moderator = strings.TrimSpace(payload.Moderator)
	payload.Reason = strings.TrimSpace(payload.Reason)
	payload.Room = strings.TrimSpace(payload.Room)

	if payload.Action == "" || payload.Target == "" || payload.Reason == "" {
		http.Error(w, "action, target, and reason are required", http.StatusBadRequest)
		return
	}

	if payload.Moderator == "" {
		payload.Moderator = "admin"
	}
	if payload.Room == "" {
		payload.Room = "main"
	}

	logModerationAction(payload.Action, payload.Target, payload.Moderator, payload.Reason)

	broadcast(Message{
		Room:      payload.Room,
		Username:  "system",
		Type:      "system",
		Text:      fmt.Sprintf("Moderator %s %s %s for: %s", payload.Moderator, payload.Action, payload.Target, payload.Reason),
		Timestamp: time.Now(),
	})

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(payload)
}

func getAdminAnalytics() AdminAnalytics {
	analytics := AdminAnalytics{
		TopRooms:    []RoomAnalytics{},
		GeneratedAt: time.Now().UTC().Format(time.RFC3339),
	}

	if db == nil {
		return analytics
	}

	db.Model(&Message{}).Count(&analytics.TotalMessages)
	db.Model(&Message{}).
		Where("timestamp >= ?", time.Now().Add(-24*time.Hour)).
		Count(&analytics.MessagesLast24Hours)
	db.Model(&Message{}).Distinct("room").Count(&analytics.DistinctRooms)
	db.Model(&ModerationLog{}).Count(&analytics.ModerationActions)

	var topRooms []RoomAnalytics
	db.Model(&Message{}).
		Select("room, COUNT(*) as message_count").
		Group("room").
		Order("message_count DESC").
		Limit(5).
		Scan(&topRooms)
	analytics.TopRooms = topRooms

	return analytics
}

func handleAdminAnalytics(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(getAdminAnalytics())
}

func checkServiceHealth(name, url string) ServiceHealth {
	checked := time.Now().UTC().Format(time.RFC3339)
	resp, err := http.Get(url)
	if err != nil {
		return ServiceHealth{Name: name, Status: "down", Detail: err.Error(), Checked: checked}
	}
	defer resp.Body.Close()

	body, _ := io.ReadAll(io.LimitReader(resp.Body, 512))
	status := "healthy"
	if resp.StatusCode >= 400 {
		status = "degraded"
	}

	detail := strings.TrimSpace(string(body))
	if detail == "" {
		detail = resp.Status
	}

	return ServiceHealth{Name: name, Status: status, Detail: detail, Checked: checked}
}

func getAdminSystemSummary() AdminSystemSummary {
	summary := AdminSystemSummary{
		DatabaseDriver:  databaseDriverName,
		PlaylistPath:    getPlaylistPath(),
		RedisEnabled:    redisClient != nil,
		RedisMemoryUsed: "unavailable",
		GeneratedAt:     time.Now().UTC().Format(time.RFC3339),
	}

	if _, err := os.Stat(summary.PlaylistPath); err == nil {
		summary.PlaylistExists = true
	}

	if redisClient != nil {
		if info, err := redisClient.Info(context.Background(), "memory").Result(); err == nil {
			if value := parseRedisInfoValue(info, "used_memory_human"); value != "" {
				summary.RedisMemoryUsed = value
			}
		}
	}

	summary.Services = []ServiceHealth{
		{Name: "chat", Status: "healthy", Detail: "local process", Checked: summary.GeneratedAt},
		checkServiceHealth("playout", "http://playout:8081/health"),
	}

	if redisClient != nil {
		if err := redisClient.Ping(context.Background()).Err(); err != nil {
			summary.Services = append(summary.Services, ServiceHealth{Name: "redis", Status: "down", Detail: err.Error(), Checked: summary.GeneratedAt})
		} else {
			summary.Services = append(summary.Services, ServiceHealth{Name: "redis", Status: "healthy", Detail: "ping ok", Checked: summary.GeneratedAt})
		}
	} else {
		summary.Services = append(summary.Services, ServiceHealth{Name: "redis", Status: "disabled", Detail: "client unavailable", Checked: summary.GeneratedAt})
	}

	if sqlDB, err := db.DB(); err == nil {
		if err := sqlDB.Ping(); err != nil {
			summary.Services = append(summary.Services, ServiceHealth{Name: "database", Status: "down", Detail: err.Error(), Checked: summary.GeneratedAt})
		} else {
			summary.Services = append(summary.Services, ServiceHealth{Name: "database", Status: "healthy", Detail: "ping ok", Checked: summary.GeneratedAt})
		}
	}

	return summary
}

func handleAdminSystemSummary(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(getAdminSystemSummary())
}

func handleAdminUsers(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}

	response := AdminUsersResponse{
		Users:        []ActiveUser{},
		RedisEnabled: redisClient != nil,
		GeneratedAt:  time.Now().UTC().Format(time.RFC3339),
	}

	if redisClient != nil {
		ctx := context.Background()
		keys, _, err := redisClient.Scan(ctx, 0, "presence:*", 200).Result()
		if err != nil {
			http.Error(w, fmt.Sprintf("failed to scan presence keys: %v", err), http.StatusInternalServerError)
			return
		}

		for _, key := range keys {
			parts := strings.SplitN(key, ":", 3)
			if len(parts) != 3 {
				continue
			}
			response.Users = append(response.Users, ActiveUser{
				Room:     parts[1],
				Username: parts[2],
				Online:   true,
			})
		}
	}

	sort.Slice(response.Users, func(i, j int) bool {
		if response.Users[i].Room == response.Users[j].Room {
			return response.Users[i].Username < response.Users[j].Username
		}
		return response.Users[i].Room < response.Users[j].Room
	})

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(response)
}

func listMediaFiles() ([]MediaFileEntry, error) {
	mediaDir := getMediaDir()
	entries, err := os.ReadDir(mediaDir)
	if err != nil {
		return nil, err
	}

	files := make([]MediaFileEntry, 0, len(entries))
	for _, entry := range entries {
		if entry.IsDir() {
			continue
		}

		info, err := entry.Info()
		if err != nil {
			continue
		}

		files = append(files, MediaFileEntry{
			Name:       entry.Name(),
			Size:       info.Size(),
			ModifiedAt: info.ModTime().UTC().Format(time.RFC3339),
		})
	}

	sort.Slice(files, func(i, j int) bool {
		return files[i].Name < files[j].Name
	})

	return files, nil
}

func handleAdminMedia(w http.ResponseWriter, r *http.Request) {
	switch r.Method {
	case http.MethodGet:
		files, err := listMediaFiles()
		if err != nil {
			http.Error(w, fmt.Sprintf("failed to list media files: %v", err), http.StatusInternalServerError)
			return
		}

		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode(AdminMediaResponse{Files: files, GeneratedAt: time.Now().UTC().Format(time.RFC3339)})
	case http.MethodPost:
		if err := r.ParseMultipartForm(256 << 20); err != nil {
			http.Error(w, fmt.Sprintf("failed to parse upload: %v", err), http.StatusBadRequest)
			return
		}

		file, header, err := r.FormFile("file")
		if err != nil {
			http.Error(w, fmt.Sprintf("missing file upload: %v", err), http.StatusBadRequest)
			return
		}
		defer file.Close()

		mediaDir := getMediaDir()
		if err := os.MkdirAll(mediaDir, 0o755); err != nil {
			http.Error(w, fmt.Sprintf("failed to ensure media directory: %v", err), http.StatusInternalServerError)
			return
		}

		targetPath := filepath.Join(mediaDir, filepath.Base(header.Filename))
		targetFile, err := os.Create(targetPath)
		if err != nil {
			http.Error(w, fmt.Sprintf("failed to create media file: %v", err), http.StatusInternalServerError)
			return
		}
		defer targetFile.Close()

		if _, err := io.Copy(targetFile, file); err != nil {
			http.Error(w, fmt.Sprintf("failed to store media file: %v", err), http.StatusInternalServerError)
			return
		}

		files, err := listMediaFiles()
		if err != nil {
			http.Error(w, fmt.Sprintf("failed to list media files: %v", err), http.StatusInternalServerError)
			return
		}

		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode(AdminMediaResponse{Files: files, GeneratedAt: time.Now().UTC().Format(time.RFC3339)})
	default:
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
	}
}

func countConnectedClients() int {
	mutex.Lock()
	defer mutex.Unlock()
	return len(clients)
}

func countActiveAdminSessions() int {
	now := time.Now()

	authSessionsMu.Lock()
	defer authSessionsMu.Unlock()

	active := 0
	for token, expiresAt := range authSessions {
		if now.After(expiresAt) {
			delete(authSessions, token)
			continue
		}
		active++
	}

	return active
}

func writePrometheusMetricLine(w io.Writer, name string, value any) {
	fmt.Fprintf(w, "%s %v\n", name, value)
}

func handleMetrics(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}

	var storedMessages int64
	if err := db.Model(&Message{}).Count(&storedMessages).Error; err != nil {
		http.Error(w, fmt.Sprintf("failed to count messages: %v", err), http.StatusInternalServerError)
		return
	}

	var moderationActions int64
	if err := db.Model(&ModerationLog{}).Count(&moderationActions).Error; err != nil {
		http.Error(w, fmt.Sprintf("failed to count moderation actions: %v", err), http.StatusInternalServerError)
		return
	}

	redisEnabled := 0
	redisUp := 0
	redisClients := 0
	if redisClient != nil {
		redisEnabled = 1
		if err := redisClient.Ping(context.Background()).Err(); err == nil {
			redisUp = 1
			if info, err := redisClient.Info(context.Background(), "clients").Result(); err == nil {
				for _, line := range strings.Split(info, "\n") {
					if strings.HasPrefix(line, "connected_clients:") {
						if value, err := strconv.Atoi(strings.TrimSpace(strings.TrimPrefix(line, "connected_clients:"))); err == nil {
							redisClients = value
						}
						break
					}
				}
			}
		}
	}

	w.Header().Set("Content-Type", "text/plain; version=0.0.4; charset=utf-8")
	fmt.Fprintln(w, "# HELP linearvoid_chat_connected_clients Current connected WebSocket clients.")
	fmt.Fprintln(w, "# TYPE linearvoid_chat_connected_clients gauge")
	writePrometheusMetricLine(w, "linearvoid_chat_connected_clients", countConnectedClients())

	fmt.Fprintln(w, "# HELP linearvoid_chat_messages_total Total stored chat messages.")
	fmt.Fprintln(w, "# TYPE linearvoid_chat_messages_total gauge")
	writePrometheusMetricLine(w, "linearvoid_chat_messages_total", storedMessages)

	fmt.Fprintln(w, "# HELP linearvoid_chat_moderation_actions_total Total moderation log entries.")
	fmt.Fprintln(w, "# TYPE linearvoid_chat_moderation_actions_total gauge")
	writePrometheusMetricLine(w, "linearvoid_chat_moderation_actions_total", moderationActions)

	fmt.Fprintln(w, "# HELP linearvoid_chat_redis_enabled Redis configured for chat service.")
	fmt.Fprintln(w, "# TYPE linearvoid_chat_redis_enabled gauge")
	writePrometheusMetricLine(w, "linearvoid_chat_redis_enabled", redisEnabled)

	fmt.Fprintln(w, "# HELP linearvoid_chat_redis_up Redis reachable from chat service.")
	fmt.Fprintln(w, "# TYPE linearvoid_chat_redis_up gauge")
	writePrometheusMetricLine(w, "linearvoid_chat_redis_up", redisUp)

	fmt.Fprintln(w, "# HELP linearvoid_chat_redis_connected_clients Redis connected client count seen by chat service.")
	fmt.Fprintln(w, "# TYPE linearvoid_chat_redis_connected_clients gauge")
	writePrometheusMetricLine(w, "linearvoid_chat_redis_connected_clients", redisClients)

	fmt.Fprintln(w, "# HELP linearvoid_chat_admin_sessions_active Active unexpired admin sessions.")
	fmt.Fprintln(w, "# TYPE linearvoid_chat_admin_sessions_active gauge")
	writePrometheusMetricLine(w, "linearvoid_chat_admin_sessions_active", countActiveAdminSessions())

	fmt.Fprintln(w, "# HELP linearvoid_chat_build_info Static build info for chat service.")
	fmt.Fprintln(w, "# TYPE linearvoid_chat_build_info gauge")
	fmt.Fprintln(w, "linearvoid_chat_build_info{service=\"chat\",database_driver=\""+databaseDriverName+"\"} 1")
}

// broadcast sends a message to all connected clients in a room and saves to DB
func broadcast(msg Message) {
	mutex.Lock()
	defer mutex.Unlock()

	// Save to SQLite
	db.Create(&msg)

	for client := range clients {
		if err := client.WriteJSON(msg); err != nil {
			client.Close()
			delete(clients, client)
		}
	}
}

// handleConnection handles WebSocket connections for chat (public rooms, private DMs, moderation)
func handleConnection(w http.ResponseWriter, r *http.Request) {
	conn, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		log.Println("Upgrade error:", err)
		return
	}
	mutex.Lock()
	clients[conn] = true
	mutex.Unlock()

	// Announce presence (ADR-007)
	username := r.URL.Query().Get("username")
	room := r.URL.Query().Get("room")
	if redisClient != nil && username != "" && room != "" {
		redisClient.Set(context.Background(), fmt.Sprintf("presence:%s:%s", room, username), "online", 60*time.Second)
		broadcast(Message{Room: room, Username: "system", Text: username + " joined " + room, Type: "system"})
	}

	defer func() {
		mutex.Lock()
		delete(clients, conn)
		mutex.Unlock()
		if redisClient != nil && username != "" && room != "" {
			redisClient.Del(context.Background(), fmt.Sprintf("presence:%s:%s", room, username))
			broadcast(Message{Room: room, Username: "system", Text: username + " left " + room, Type: "system"})
		}
		conn.Close()
	}()

	for {
		var msg Message
		if err := conn.ReadJSON(&msg); err != nil {
			break
		}

		msg.Timestamp = time.Now()
		msg.Username = username // enforce from query param for security

		// Rate limiting check using Redis (ADR-007)
		if redisClient != nil {
			key := fmt.Sprintf("rate:%s", msg.Username)
			count, _ := redisClient.Incr(context.Background(), key).Result()
			if count == 1 {
				redisClient.Expire(context.Background(), key, 10*time.Second)
			}
			if count > 10 {
				conn.WriteJSON(Message{Type: "system", Text: "Rate limit exceeded. Please slow down."})
				continue
			}
		}

		// Handle moderation commands
		if strings.HasPrefix(msg.Text, "/mod ") || strings.HasPrefix(msg.Text, "/mute ") || strings.HasPrefix(msg.Text, "/ban ") {
			handleModerationCommand(msg, conn)
			continue
		}

		// Handle private DMs (room format "dm:user1-user2")
		if strings.HasPrefix(msg.Room, "dm:") {
			handlePrivateDM(msg)
			return
		}

		log.Printf("Chat message in room %s from %s: %s", msg.Room, msg.Username, msg.Text)
		broadcast(msg)

		// Save to SQLite (already done in broadcast, but ensure for private DMs)
		if msg.Type == "private" {
			db.Create(&msg)
		}
	}
}

// handlePrivateDM routes private messages to the specific user pair
func handlePrivateDM(msg Message) {
	// Save to SQLite for history
	db.Create(&msg)

	// Broadcast only to participants (simplified - in production use a map of user connections)
	broadcast(msg)
	log.Printf("Private DM from %s to room %s: %s", msg.Username, msg.Room, msg.Text)
}

// logModerationAction logs an action to the immutable ModerationLog table (ADR-005/ADR-007)
func logModerationAction(action, target, moderator, reason string) {
	logEntry := ModerationLog{
		Action:    action,
		Target:    target,
		Moderator: moderator,
		Reason:    reason,
		Timestamp: time.Now(),
	}
	db.Create(&logEntry)
	log.Printf("Moderation action logged: %s %s by %s - %s", action, target, moderator, reason)
}

// handleModerationCommand processes /mod, /mute, /ban commands and logs to ModerationLog
func handleModerationCommand(msg Message, conn *websocket.Conn) {
	parts := strings.Fields(msg.Text)
	if len(parts) < 3 {
		conn.WriteJSON(Message{Type: "system", Text: "Usage: /mod <action> <target> <reason> or /mute <user> <reason>"})
		return
	}

	action := strings.TrimPrefix(parts[0], "/")
	target := parts[1]
	reason := strings.Join(parts[2:], " ")

	logModerationAction(action, target, msg.Username, reason)

	broadcast(Message{
		Room:  msg.Room,
		Type:  "system",
		Text:  fmt.Sprintf("Moderator %s %s %s for: %s", msg.Username, action, target, reason),
	})
}

func main() {
	initRedis()
	initDB()

	http.HandleFunc("/ws", handleConnection)
	http.HandleFunc("/api/admin/login", handleAdminLogin)
	http.HandleFunc("/api/admin/logout", handleAdminLogout)
	http.HandleFunc("/api/admin/session", handleAdminSession)
	http.HandleFunc("/api/admin/overview", requireAdminAuth(handleAdminOverview))
	http.HandleFunc("/api/admin/playlist", requireAdminAuth(handleAdminPlaylist))
	http.HandleFunc("/api/admin/moderation/logs", requireAdminAuth(handleAdminModerationLogs))
	http.HandleFunc("/api/admin/moderation/actions", requireAdminAuth(handleAdminModerationAction))
	http.HandleFunc("/api/admin/analytics", requireAdminAuth(handleAdminAnalytics))
	http.HandleFunc("/api/admin/system", requireAdminAuth(handleAdminSystemSummary))
	http.HandleFunc("/api/admin/users", requireAdminAuth(handleAdminUsers))
	http.HandleFunc("/api/admin/schedule", requireAdminAuth(handleAdminSchedule))
	http.HandleFunc("/api/admin/media", requireAdminAuth(handleAdminMedia))
	http.HandleFunc("/metrics", handleMetrics)
	http.HandleFunc("/health", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusOK)
		fmt.Fprint(w, `{"status":"healthy","service":"chat","timestamp":"`+time.Now().UTC().Format(time.RFC3339)+`"}`)
	})

	port := os.Getenv("CHAT_PORT")
	if port == "" {
		port = "3000"
	}

	log.Printf("Chat Backend starting on :%s (WebSocket at /ws, health at /health, database persistence enabled)", port)
	log.Fatal(http.ListenAndServe(":"+port, nil))
}