package main

import (
	"context"
	"flag"
	"fmt"
	"log"
	"os"
	"os/signal"
	"syscall"
	"time"

	"naviwatcher/internal/config"
	"naviwatcher/internal/database"
	"naviwatcher/internal/musicbrainz"
	"naviwatcher/internal/navidrome"
	"naviwatcher/internal/notifier"
	"naviwatcher/internal/scanner"
	"naviwatcher/internal/web"
)

// App holds all application dependencies for clean shutdown and testability.
type App struct {
	cfg      *config.Config
	db       *database.DB
	mbClient *musicbrainz.MusicBrainzClient
	ndClient *navidrome.NavidromeClient
	web      *web.Server
	sender   notifier.Sender

	// syncFn, when non-nil, replaces the real syncAndScan call in
	// startPeriodicSync so tests can observe the loop without live clients.
	syncFn func(ctx context.Context) error
}

// navidromeClientFactory constructs the Navidrome client. It is a package-level
// variable (not a direct call to navidrome.NewClient) so tests can inject a stub
// without requiring a live Navidrome server for authentication.
var navidromeClientFactory = navidrome.NewClient

const defaultConfigPath = "config.yaml"

func main() {
	configPath := flag.String("config", defaultConfigPath, "Path to config file")
	flag.Parse()

	log.Println("NaviWatcher starting...")

	cfg, err := config.LoadConfig(*configPath)
	if err != nil {
		log.Fatalf("Failed to load config: %v", err)
	}

	log.Printf("Config loaded from %s (server: %s:%d)", *configPath, cfg.Server.Host, cfg.Server.Port)

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	sigCh := make(chan os.Signal, 1)
	signal.Notify(sigCh, syscall.SIGINT, syscall.SIGTERM)

	go func() {
		sig := <-sigCh
		log.Printf("Received signal %v, shutting down...", sig)
		cancel()
	}()

	app, err := NewApp(ctx, cfg, "naviwatcher.db")
	if err != nil {
		log.Fatalf("Failed to initialize application: %v", err)
	}
	defer app.Close()

	if err := app.run(ctx); err != nil {
		log.Fatalf("Application error: %v", err)
	}

	log.Println("NaviWatcher stopped.")
}

// NewApp initializes all application components: config, database, and MusicBrainz client.
// dbPath is the SQLite database path (use ":memory:" for tests).
func NewApp(ctx context.Context, cfg *config.Config, dbPath string) (*App, error) {
	// Initialize database.
	db, err := database.New(dbPath)
	if err != nil {
		return nil, fmt.Errorf("failed to initialize database: %w", err)
	}

	// Initialize MusicBrainz client with rate limiting.
	mbClient := musicbrainz.NewClient(cfg.MusicBrainz)

	log.Printf("MusicBrainz client initialized (user-agent: %s)", cfg.MusicBrainz.UserAgent)

	// Initialize Navidrome client (authenticates immediately; error if auth fails).
	ndClient, err := navidromeClientFactory(cfg.Navidrome)
	if err != nil {
		return nil, fmt.Errorf("failed to initialize navidrome client: %w", err)
	}

	// Build the Web UI dashboard server (not started until run).
	webServer := web.NewServerWithConfig(cfg, db)

	// Build the notifier sender. A nil sender is fine when Telegram is disabled;
	// the scheduler is no-op-safe and the web UI needs no sender.
	var sender notifier.Sender
	if cfg.Telegram.Enabled {
		sender = notifier.NewTelegramSender(cfg.Telegram)
	}

	return &App{
		cfg:      cfg,
		db:       db,
		mbClient: mbClient,
		ndClient: ndClient,
		web:      webServer,
		sender:   sender,
	}, nil
}

// Close cleans up all application resources in reverse order of initialization.
func (a *App) Close() {
	if a.mbClient != nil {
		a.mbClient.Close()
	}
	if a.db != nil {
		if err := a.db.Close(); err != nil {
			log.Printf("Error closing database: %v", err)
		}
	}
}

func (a *App) run(ctx context.Context) error {
	// Run an immediate sync+scan so the service produces results without
	// waiting a full interval.
	if err := a.doSync(ctx); err != nil {
		if ctx.Err() != nil {
			return nil
		}
		log.Printf("Initial sync+scan failed: %v", err)
	}

	// Start the Web UI dashboard in its own goroutine; it serves until ctx is
	// cancelled, then shuts down gracefully.
	if a.web != nil {
		go func() {
			if err := a.web.Start(ctx); err != nil {
				if ctx.Err() != nil {
					return
				}
				log.Printf("Web UI server stopped with error: %v", err)
			}
		}()
	}

	// Start the Telegram notifier scheduler. It is no-op-safe when Telegram is
	// disabled (sender nil / enabled false), so always calling it is safe.
	a.startNotifier(ctx)

	// Kick off the periodic sync+scan loop goroutine.
	a.startPeriodicSync(ctx)

	<-ctx.Done()
	return nil
}

// doSync runs the sync pipeline, using the injected syncFn when present (tests)
// or the real syncAndScan otherwise.
func (a *App) doSync(ctx context.Context) error {
	if a.syncFn != nil {
		return a.syncFn(ctx)
	}
	return a.syncAndScan(ctx)
}

// syncAndScan runs the full data pipeline once: Navidrome artist sync, the
// MusicBrainz discography pipeline (SyncAll), then the scanner over the
// now-populated DB. It logs results and observes ctx cancellation.
func (a *App) syncAndScan(ctx context.Context) error {
	if err := navidrome.SyncArtists(ctx, a.ndClient, a.db); err != nil {
		return fmt.Errorf("sync artists: %w", err)
	}

	discography := musicbrainz.NewDiscographySyncer(a.mbClient)
	albums := musicbrainz.NewAlbumSyncer(func(ctx context.Context, db *database.DB) error {
		return navidrome.SyncAlbums(ctx, a.ndClient, db)
	})
	if err := musicbrainz.SyncAll(ctx, a.db, a.mbClient, discography, albums, a.cfg.MusicBrainz.CacheTTL); err != nil {
		return fmt.Errorf("sync all: %w", err)
	}

	missing, err := scanner.ScanAll(ctx, a.db, a.cfg.Scanner.FuzzyThreshold)
	if err != nil {
		return fmt.Errorf("scan all: %w", err)
	}

	log.Printf("Scan complete: %d missing release(s) across monitored artists", len(missing))
	for _, m := range missing {
		log.Printf("  missing: artist=%s rgid=%s title=%q", m.ArtistID, m.RGID, m.Title)
	}
	return nil
}

// startNotifier wires the Telegram digest scheduler. The scheduler is
// no-op-safe (returns without starting when disabled or sender is nil), so it
// is always safe to call. The base URL for dashboard links comes from the
// server's configured public_url.
func (a *App) startNotifier(ctx context.Context) {
	if !a.cfg.Telegram.Enabled {
		return
	}
	schedule, err := notifier.NewCronSchedule(a.cfg.Telegram.CronSchedule)
	if err != nil {
		log.Printf("Notifier schedule invalid (%q): %v; notifier disabled", a.cfg.Telegram.CronSchedule, err)
		return
	}
	uiBaseURL := a.cfg.Server.PublicURL
	notifier.StartScheduler(ctx, true, schedule, func(ctx context.Context) error {
		_, err := notifier.NotifyOnce(ctx, a.db, a.sender, a.cfg.Telegram, uiBaseURL)
		return err
	}, nil)
}

// startPeriodicSync runs syncAndScan on a ticker at cfg.Sync.Interval. It
// blocks until ctx is cancelled, then returns cleanly. Each tick spawns a
// goroutine so a slow sync does not block the ticker, but a new sync is
// skipped while the previous one is still running (guarded by a done channel)
// so syncs never overlap and contend for the shared DB and rate-limited
// MusicBrainz client.
func (a *App) startPeriodicSync(ctx context.Context) {
	ticker := time.NewTicker(a.cfg.Sync.Interval)
	defer ticker.Stop()

	// free is a sentinel channel: nil means a sync is currently in flight.
	var free = make(chan struct{}, 1)
	free <- struct{}{}

	for {
		select {
		case <-ctx.Done():
			log.Println("Periodic sync stopped.")
			return
		case <-ticker.C:
			select {
			case <-free:
				// Slot was free; start a sync and release the slot when done.
				go func() {
					defer func() { free <- struct{}{} }()
					if err := a.doSync(ctx); err != nil {
						if ctx.Err() != nil {
							return
						}
						log.Printf("Periodic sync+scan failed: %v", err)
					}
				}()
			default:
				// Previous sync still running; skip this tick.
				log.Println("Skipping periodic sync: previous sync still in progress.")
			}
		}
	}
}