package main

import (
	"context"
	"errors"
	"flag"
	"fmt"
	"log/slog"
	"net/http"
	"os"
	"os/signal"
	"syscall"
	"time"

	"github.com/jackc/pgx/v5/pgxpool"

	"git.fabledsword.com/bvandeusen/minstrel/internal/config"
	"git.fabledsword.com/bvandeusen/minstrel/internal/coverart"
	"git.fabledsword.com/bvandeusen/minstrel/internal/db"
	"git.fabledsword.com/bvandeusen/minstrel/internal/eventbus"
	"git.fabledsword.com/bvandeusen/minstrel/internal/gc"
	"git.fabledsword.com/bvandeusen/minstrel/internal/library"
	"git.fabledsword.com/bvandeusen/minstrel/internal/lidarr"
	"git.fabledsword.com/bvandeusen/minstrel/internal/lidarrconfig"
	"git.fabledsword.com/bvandeusen/minstrel/internal/lidarrrequests"
	"git.fabledsword.com/bvandeusen/minstrel/internal/logging"
	"git.fabledsword.com/bvandeusen/minstrel/internal/playlists"
	"git.fabledsword.com/bvandeusen/minstrel/internal/scrobble"
	"git.fabledsword.com/bvandeusen/minstrel/internal/scrobble/listenbrainz"
	"git.fabledsword.com/bvandeusen/minstrel/internal/server"
	"git.fabledsword.com/bvandeusen/minstrel/internal/similarity"
	"git.fabledsword.com/bvandeusen/minstrel/internal/subsonic"
	syncpkg "git.fabledsword.com/bvandeusen/minstrel/internal/sync"
)

func main() {
	if len(os.Args) > 1 {
		switch os.Args[1] {
		case "admin":
			if err := runAdmin(os.Args[2:]); err != nil {
				fmt.Fprintf(os.Stderr, "minstrel admin: %v\n", err)
				os.Exit(1)
			}
			return
		case "migrate":
			if err := runMigrate(os.Args[2:]); err != nil {
				fmt.Fprintf(os.Stderr, "minstrel migrate: %v\n", err)
				os.Exit(1)
			}
			return
		}
	}
	if err := run(); err != nil {
		fmt.Fprintf(os.Stderr, "minstrel: %v\n", err)
		os.Exit(1)
	}
}

// safetyNetScanInterval backstops the fsnotify watcher with a low-frequency
// full delta walk, catching anything the watcher missed (inotify watch-limit
// exhaustion, dropped events). Fixed — there is no operator configuration.
const safetyNetScanInterval = 12 * time.Hour

// runSafetyNetScans ticks a delta RunScan at safetyNetScanInterval until ctx
// is cancelled, deferring to TryStartScan's in-flight guard so it never
// collides with a manual, startup, or watcher-driven scan.
func runSafetyNetScans(ctx context.Context, pool *pgxpool.Pool, scanner *library.Scanner,
	enricher *coverart.Enricher, logger *slog.Logger, scanCfg library.RunScanConfig,
) {
	ticker := time.NewTicker(safetyNetScanInterval)
	defer ticker.Stop()
	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			started, existing, err := library.TryStartScan(ctx, pool, scanner, enricher, logger, scanCfg)
			if err != nil {
				logger.Error("safety-net scan: try start failed", "err", err)
			} else if !started && existing != nil {
				logger.Info("safety-net scan skipped — prior still in flight",
					"in_flight_id", existing.ID)
			}
		}
	}
}

func run() error {
	configPath := flag.String("config", os.Getenv("MINSTREL_CONFIG"), "path to YAML config file")
	flag.Parse()

	cfg, err := config.Load(*configPath)
	if err != nil {
		return fmt.Errorf("load config: %w", err)
	}

	logger, err := logging.New(os.Stdout, cfg.Log.Level, cfg.Log.Format)
	if err != nil {
		return fmt.Errorf("init logger: %w", err)
	}

	logger.Info("minstrel starting",
		"address", cfg.Server.Address,
		"log_level", cfg.Log.Level,
		"log_format", cfg.Log.Format,
	)

	ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
	defer stop()

	if err := db.Migrate(cfg.Database.URL, logger); err != nil {
		return fmt.Errorf("migrate: %w", err)
	}

	pool, err := db.Open(ctx, cfg.Database.URL)
	if err != nil {
		return fmt.Errorf("open db: %w", err)
	}
	defer pool.Close()

	scanner := library.New(pool, logger, cfg.Library.ScanPaths)

	contact := cfg.Library.ContactEmail
	if contact == "" {
		contact = "https://git.fabledsword.com/bvandeusen/minstrel"
	}
	// Swap in the production User-Agent + MinPeriod on the registered
	// MBCAA provider. init() registered it with default config; this
	// updates the running instance.
	coverart.NewMBCAAProviderFromConfig(coverart.FetcherConfig{
		UserAgent: fmt.Sprintf("Minstrel/dev (%s)", contact),
		MinPeriod: time.Second,
	})

	coverSettings, err := coverart.NewSettingsService(ctx, pool, logger.With("component", "coverart"))
	if err != nil {
		logger.Error("coverart settings service init failed", "err", err)
		os.Exit(1)
	}
	if newVer, bumped, berr := coverSettings.BumpVersionIfProvidersChanged(ctx); berr != nil {
		logger.Warn("coverart: provider-hash boot check failed", "err", berr)
	} else if bumped {
		logger.Info("coverart: registered provider set changed; version bumped",
			"new_version", newVer)
	}
	coverEnricher := coverart.NewEnricher(pool, logger.With("component", "coverart"), coverSettings)
	coverEnricher.DataDir = cfg.Storage.DataDir

	// One unified scan chain: library walk → MBID backfill → cover enrich.
	// Boot-time scan and manual-trigger scans share this path; results land
	// in scan_runs for the admin overview.
	if cfg.Library.ScanOnStartup && len(cfg.Library.ScanPaths) > 0 {
		go func() {
			if _, err := library.RunScan(ctx, pool, scanner, coverEnricher,
				logger.With("component", "scan_run"),
				library.RunScanConfig{
					BackfillCap:     5000,
					EnrichCap:       -1, // #388: no global cap; per-provider rate limits
					ArtistEnrichCap: -1,
					DataDir:         cfg.Storage.DataDir,
				},
			); err != nil {
				logger.Warn("startup scan run failed", "err", err)
			}
		}()
	} else {
		// No startup file walk, but still run backfill + enrich so cover
		// progress doesn't stall just because the operator disabled
		// scan-on-startup.
		go func() {
			if _, err := library.RunScan(ctx, pool, nil, coverEnricher,
				logger.With("component", "scan_run"),
				library.RunScanConfig{
					BackfillCap:     5000,
					EnrichCap:       -1, // #388: no global cap; per-provider rate limits
					ArtistEnrichCap: -1,
					DataDir:         cfg.Storage.DataDir,
				},
			); err != nil {
				logger.Warn("boot-only scan run failed", "err", err)
			}
		}()
	}

	// Start the ListenBrainz scrobble worker. Per spec §M4a, runs every 30s
	// and drains up to 50 pending rows per tick. Per-user gating happens
	// inside the worker (rows from disabled users are skipped).
	scrobbleWorker := scrobble.NewWorker(pool, listenbrainz.NewClient(), logger.With("component", "scrobble"))
	go scrobbleWorker.Run(ctx)

	// Start the similarity ingest worker. Per spec §M4b, runs every 1h, drains
	// up to 5 played tracks + 5 played artists per tick, weekly re-fetch cap
	// per row. Public LB endpoints — no token required.
	similarityWorker := similarity.NewWorker(pool, listenbrainz.NewClient(), logger.With("component", "similarity"))
	go similarityWorker.Run(ctx)

	// Start the GC worker. Runs every 1h and sweeps lifecycle tables
	// that have no writer-side close path or retention policy:
	// orphan play_events, stale play_sessions, expired
	// scrobble_queue failures, stuck system_playlist_runs, expired
	// password_resets. Each sweep is idempotent — a row that's
	// already clean is a no-op. Addresses drift audit findings
	// #565 #566 #567 #574 #575 (Scribe parent #552).
	gcWorker := gc.NewWorker(pool, logger.With("component", "gc"))
	go gcWorker.Run(ctx)

	// Start the Lidarr reconciler worker. Per spec §M5a, polls pending Lidarr
	// import requests and reconciles them against the library. Short-circuits
	// to no-op when lidarr_config.enabled = false.
	lidarrCfg := lidarrconfig.New(pool)
	// Live-event bus shared between SSE subscribers (api.Mount) and
	// background workers that publish (reconciler today; scanner later).
	// Constructed before any service that publishes so they all share the
	// same instance.
	bus := eventbus.New()
	// Scan-run lifecycle events use a package-level setter rather than
	// threading the bus through RunScan + TryStartScan + the Scheduler
	// + every test caller. Per-process singleton, set once at startup.
	library.SetEventBus(bus)
	// Per-tick Lidarr client factory: re-reads config so an admin save
	// takes effect without a restart, returning nil while Lidarr is
	// disabled/unconfigured. Mirrors server.go's lidarrClientFn; the
	// reconciler uses it to (re)send unconfirmed adds.
	lidarrClientFn := func() *lidarr.Client {
		c, cerr := lidarrCfg.Get(ctx)
		if cerr != nil || !c.Enabled || c.BaseURL == "" || c.APIKey == "" {
			return nil
		}
		return lidarr.NewClient(c.BaseURL, c.APIKey)
	}
	lidarrReconciler := lidarrrequests.NewReconciler(pool, lidarrCfg, lidarrClientFn, logger.With("component", "lidarr"), bus)
	go lidarrReconciler.Run(ctx)

	// library_changes compactor (#357 follow-up). Daily tick; deletes
	// rows older than the configured retention so the change-log table
	// doesn't grow unbounded. Clients that drop offline longer than
	// retention hit the /api/library/sync 410 fallback and resync.
	libraryChangesCompactor := syncpkg.NewCompactor(pool, logger.With("component", "library_changes_compactor"))
	go libraryChangesCompactor.Run(ctx)

	// Per-user system-playlist scheduler (#392 Half B). Fires each
	// active user's daily build at 03:00 in their stored timezone.
	// Replaces the 24h-anchored cron loop (removed in the next commit
	// of this arc).
	playlistScheduler, err := playlists.NewScheduler(
		pool,
		logger.With("component", "playlist_scheduler"),
		cfg.Storage.DataDir,
		bus,
	)
	if err != nil {
		return fmt.Errorf("init playlist scheduler: %w", err)
	}
	if err := playlistScheduler.Start(ctx); err != nil {
		return fmt.Errorf("start playlist scheduler: %w", err)
	}
	defer playlistScheduler.Stop()

	// Ensure DataDir exists before any service tries to write into it.
	// Fatal on failure: a non-writable data_dir silently breaks every
	// downstream cache (playlist covers, artist art, album-cover fallback)
	// and produces "0 successes" symptoms that are hard to diagnose.
	if cfg.Storage.DataDir != "" {
		if err := os.MkdirAll(cfg.Storage.DataDir, 0o755); err != nil {
			logger.Error("data_dir create failed; refusing to start",
				"path", cfg.Storage.DataDir, "err", err)
			os.Exit(1)
		}
	}

	scanCfg := library.RunScanConfig{
		BackfillCap:     5000,
		EnrichCap:       -1, // #388: no global cap; per-provider rate limits
		ArtistEnrichCap: -1,
		DataDir:         cfg.Storage.DataDir,
	}
	// Filesystem watcher: near-instant pickup of new/changed files via
	// fsnotify, scanning just the affected paths + enriching their albums
	// inline. Replaces the removed configurable scan scheduler.
	watcher := library.NewWatcher(scanner, coverEnricher,
		logger.With("component", "watcher"), cfg.Library.ScanPaths)
	go func() {
		if werr := watcher.Run(ctx); werr != nil {
			logger.Warn("library watcher exited", "err", werr)
		}
	}()
	// Safety-net delta walk backstops the watcher (inotify limits / dropped
	// events) at a fixed low frequency. No operator config.
	go runSafetyNetScans(ctx, pool, scanner, coverEnricher,
		logger.With("component", "scan_safetynet"), scanCfg)

	srv := server.New(logger, pool, scanner, subsonic.Config{
		AllowPlaintextPassword: cfg.Subsonic.AllowPlaintextPassword,
	}, cfg.Events, cfg.Recommendation, cfg.Storage.DataDir, cfg.Branding, coverEnricher, coverSettings, scanner, scanCfg)
	srv.Bus = bus
	srv.PlaylistScheduler = playlistScheduler
	srv.StreamSecret = cfg.StreamSecret
	httpServer := &http.Server{
		Addr:              cfg.Server.Address,
		Handler:           srv.Router(),
		ReadHeaderTimeout: 10 * time.Second,
	}

	errCh := make(chan error, 1)
	go func() {
		logger.Info("listening", "address", cfg.Server.Address)
		if err := httpServer.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
			errCh <- err
		}
		close(errCh)
	}()

	select {
	case <-ctx.Done():
		logger.Info("shutdown signal received")
	case err := <-errCh:
		if err != nil {
			return fmt.Errorf("server: %w", err)
		}
	}

	shutdownCtx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()
	if err := httpServer.Shutdown(shutdownCtx); err != nil {
		return fmt.Errorf("shutdown: %w", err)
	}
	logger.Info("minstrel stopped")
	return nil
}