package server

import (
	"context"
	"errors"
	"fmt"
	"net/http"
	"time"

	"music-server/internal/backend"
	"music-server/internal/config"
	"music-server/internal/db"
	"music-server/internal/db/repository"
	"music-server/internal/logging"
	"music-server/internal/metrics"

	"github.com/prometheus/client_golang/prometheus"
	"go.uber.org/zap"
)

// Database is the database connection used by the server.
type Database interface {
	Health(ctx context.Context) map[string]string
	Close()
}

type Server struct {
	cfg        config.Config
	db         Database
	q          repository.Querier
	music      *backend.MusicService
	library    *backend.LibraryService
	sync       *backend.SyncService
	characters *backend.CharacterService
	releases   *backend.ReleaseService
	stats      *backend.StatisticsService
	search     *backend.SearchCache
	// covers is nil when COVERS_PATH is not set.
	covers *backend.CoverService
	// stopCovers ends the background cover search; coversDone is closed when it has ended.
	stopCovers context.CancelFunc
	coversDone chan struct{}
	httpServer *http.Server
	// metrics serves /metrics on its own port; nil when metrics are off.
	metrics *metrics.Server
}

// New creates a Server with all services wired up.
func New(cfg config.Config, q repository.Querier, database Database) (*Server, error) {
	characters, err := backend.NewCharacterService(cfg.CharactersPath)
	if err != nil {
		return nil, fmt.Errorf("characters path: %w", err)
	}

	s := &Server{
		cfg:        cfg,
		db:         database,
		q:          q,
		music:      backend.NewMusicService(q, cfg.SoundCheckPath),
		library:    backend.NewLibraryService(q),
		characters: characters,
		releases:   backend.NewReleaseService(cfg.ReleasesURL),
		stats:      backend.NewStatisticsService(q),
	}
	s.search = backend.NewSearchCache(s.music.SearchSoundtracks)
	s.sync = backend.NewSyncService(q, cfg.MusicPath, s.afterSync)

	if cfg.CoversPath != "" {
		s.covers, err = backend.NewCoverService(q, cfg.CoversPath, backend.CoverOptions{
			SteamGridDBKey: cfg.SteamGridDBAPIKey,
			SteamGridDBURL: cfg.SteamGridDBURL,
			AniListURL:     cfg.AniListURL,
		})
		if err != nil {
			return nil, fmt.Errorf("covers path: %w", err)
		}
	}
	if cfg.MetricsPort > 0 {
		s.metrics = metrics.NewServer(cfg.MetricsPort)
	}
	s.httpServer = &http.Server{
		Addr:         fmt.Sprintf(":%d", cfg.Port),
		Handler:      s.RegisterRoutes(),
		IdleTimeout:  time.Minute,
		ReadTimeout:  10 * time.Second,
		WriteTimeout: 30 * time.Second,
	}
	return s, nil
}

// startCoverSearch runs the background cover search until Shutdown. It does nothing when
// covers are off or there is no SteamGridDB API key.
func (s *Server) startCoverSearch() {
	if s.covers == nil || !s.covers.SearchesAutomatically() {
		logging.GetLogger().Info("Automatic cover search is off",
			zap.Bool("covers_path_set", s.covers != nil))
		return
	}
	ctx, cancel := context.WithCancel(context.Background())
	s.stopCovers, s.coversDone = cancel, make(chan struct{})
	go func() {
		defer close(s.coversDone)
		s.covers.Run(ctx)
	}()
}

// soundtracksChanged reloads the cached soundtrack data after soundtracks were edited, and
// lets the cover search try the new names.
func (s *Server) soundtracksChanged(ctx context.Context) {
	if err := s.music.ReloadSoundtracks(ctx); err != nil {
		logging.GetLogger().Error("Failed to reload soundtracks", zap.Error(err))
	}
	if err := s.search.Reload(ctx); err != nil {
		logging.GetLogger().Error("Failed to reload search cache", zap.Error(err))
	}
	if s.covers != nil {
		s.covers.Trigger()
	}
}

// afterSync refreshes cached data once a sync has finished.
func (s *Server) afterSync(ctx context.Context) {
	if err := s.music.EndAllQueues(ctx); err != nil {
		logging.GetLogger().Error("Failed to end the queues after sync", zap.Error(err))
	}
	if err := s.music.ReloadSoundtracks(ctx); err != nil {
		logging.GetLogger().Error("Failed to reload soundtracks after sync", zap.Error(err))
	}
	if err := s.search.Reload(ctx); err != nil {
		logging.GetLogger().Error("Failed to reload search cache after sync", zap.Error(err))
	}
	if s.covers != nil {
		s.covers.Trigger()
	}
}

// NewServerInstance loads the configuration, connects to and migrates the database and creates the Server.
// It exits the process if any of these steps fail.
func NewServerInstance() *Server {
	cfg, err := config.Load()
	logging.Init(cfg.LogLevel, cfg.LogJSON)
	logger := logging.GetLogger()
	if err != nil {
		logger.Fatal("Invalid settings", zap.Error(err))
	}

	logger.Info("Starting server",
		zap.String("host", cfg.DBHost),
		zap.String("dbPort", cfg.DBPort),
		zap.String("username", cfg.DBUser),
		zap.String("dbName", cfg.DBName),
		zap.String("musicPath", cfg.MusicPath),
		zap.String("charactersPath", cfg.CharactersPath),
	)

	ctx := context.Background()
	database, err := db.NewDatabase(ctx, db.ConnString(cfg.DBHost, cfg.DBPort, cfg.DBUser, cfg.DBPassword, cfg.DBName))
	if err != nil {
		logger.Fatal("Failed to initialize database", zap.Error(err))
	}
	if err := database.RunMigrations(); err != nil {
		logger.Fatal("Migration failed", zap.Error(err))
	}

	s, err := New(cfg, repository.New(database.Pool), database)
	if err != nil {
		logger.Fatal("Failed to create server", zap.Error(err))
	}
	prometheus.MustRegister(metrics.NewPoolCollector(database.Pool))
	if err := s.sync.UpdateLibraryMetrics(ctx); err != nil {
		logger.Error("Failed to count the library", zap.Error(err))
	}
	return s
}

// ListenAndServe starts the HTTP server and the metrics server. It returns nil after a
// graceful shutdown. The server keeps running without metrics if their port cannot be opened.
func (s *Server) ListenAndServe() error {
	if s.metrics != nil {
		if err := s.metrics.Start(); err != nil {
			logging.GetLogger().Error("Failed to start the metrics server", zap.Error(err))
		}
	}
	s.startCoverSearch()
	logging.GetLogger().Info("Server starting", zap.String("address", s.httpServer.Addr))
	if err := s.httpServer.ListenAndServe(); !errors.Is(err, http.ErrServerClosed) {
		return err
	}
	return nil
}

// Shutdown stops accepting requests, waits for running requests and then closes the database.
func (s *Server) Shutdown(ctx context.Context) error {
	err := s.httpServer.Shutdown(ctx)
	if s.metrics != nil {
		err = errors.Join(err, s.metrics.Shutdown(ctx))
	}
	if s.stopCovers != nil {
		s.stopCovers()
		<-s.coversDone
	}
	s.sync.Wait()
	s.characters.Close()
	s.db.Close()
	return err
}

// HTTPServer returns the underlying http.Server.
func (s *Server) HTTPServer() *http.Server {
	return s.httpServer
}