package autoscanner

import (
	"context"
	"errors"
	"seanime/internal/api/metadata"
	"seanime/internal/database/db"
	"seanime/internal/database/db_bridge"
	"seanime/internal/database/models"
	"seanime/internal/events"
	"seanime/internal/library/autodownloader"
	"seanime/internal/library/scanner"
	"seanime/internal/library/summary"
	"seanime/internal/notifier"
	"seanime/internal/platforms/platform"
	"seanime/internal/util"
	"sync"
	"time"

	"github.com/rs/zerolog"
)

type (
	AutoScanner struct {
		fileActionCh     chan struct{} // Used to notify the scanner that a file action has occurred.
		waiting          bool          // Used to prevent multiple scans from occurring at the same time.
		missedAction     bool          // Used to indicate that a file action was missed while scanning.
		mu               sync.Mutex
		scannedCh        chan struct{}
		waitTime         time.Duration // Wait time to listen to additional changes before triggering a scan.
		enabled          bool
		settings         models.LibrarySettings
		platform         platform.Platform
		logger           *zerolog.Logger
		wsEventManager   events.WSEventManagerInterface
		db               *db.Database                   // Database instance is required to update the local files.
		autoDownloader   *autodownloader.AutoDownloader // AutoDownloader instance is required to refresh queue.
		metadataProvider metadata.Provider
		logsDir          string
	}
	NewAutoScannerOptions struct {
		Database         *db.Database
		Platform         platform.Platform
		Logger           *zerolog.Logger
		WSEventManager   events.WSEventManagerInterface
		Enabled          bool
		AutoDownloader   *autodownloader.AutoDownloader
		WaitTime         time.Duration
		MetadataProvider metadata.Provider
		LogsDir          string
	}
)

func New(opts *NewAutoScannerOptions) *AutoScanner {
	wt := time.Second * 15 // Default wait time is 15 seconds.
	if opts.WaitTime > 0 {
		wt = opts.WaitTime
	}

	return &AutoScanner{
		fileActionCh:     make(chan struct{}, 1),
		waiting:          false,
		missedAction:     false,
		mu:               sync.Mutex{},
		scannedCh:        make(chan struct{}, 1),
		waitTime:         wt,
		enabled:          opts.Enabled,
		platform:         opts.Platform,
		logger:           opts.Logger,
		wsEventManager:   opts.WSEventManager,
		db:               opts.Database,
		autoDownloader:   opts.AutoDownloader,
		metadataProvider: opts.MetadataProvider,
		logsDir:          opts.LogsDir,
	}
}

// Notify is used to notify the AutoScanner that a file action has occurred.
func (as *AutoScanner) Notify() {
	if as == nil {
		return
	}

	defer util.HandlePanicInModuleThen("scanner/autoscanner/Notify", func() {
		as.logger.Error().Msg("autoscanner: recovered from panic")
	})

	as.mu.Lock()
	defer as.mu.Unlock()

	// If we are currently scanning, we will set the missedAction flag to true.
	if as.waiting {
		as.missedAction = true
		return
	}

	if as.enabled {
		go func() {
			// Otherwise, we will send a signal to the fileActionCh.
			as.fileActionCh <- struct{}{}
		}()
	}
}

// Start starts the AutoScanner in a goroutine.
func (as *AutoScanner) Start() {
	go func() {
		if as.enabled {
			as.logger.Info().Msg("autoscanner: Module started")
		}

		as.watch()
	}()
}

// SetSettings should be called after the settings are fetched and updated from the database.
func (as *AutoScanner) SetSettings(settings models.LibrarySettings) {
	as.mu.Lock()
	defer as.mu.Unlock()

	as.enabled = settings.AutoScan
	as.settings = settings
}

// watch is used to watch for file actions and trigger a scan.
// When a file action occurs, it will wait 30 seconds before triggering a scan.
// If another file action occurs within that 30 seconds, it will reset the timer.
// After the 30 seconds have passed, it will trigger a scan.
// When a scan is complete, it will check the missedAction flag and trigger another scan if necessary.
func (as *AutoScanner) watch() {
	defer util.HandlePanicInModuleThen("scanner/autoscanner/watch", func() {
		as.logger.Error().Msg("autoscanner: recovered from panic")
	})

	for {
		// Block until the file action channel is ready to receive a signal.
		<-as.fileActionCh
		as.waitAndScan()
	}

}

// waitAndScan is used to wait for additional file actions before triggering a scan.
func (as *AutoScanner) waitAndScan() {
	as.logger.Trace().Msgf("autoscanner: File action occurred, waiting %v seconds before triggering a scan.", as.waitTime.Seconds())
	as.mu.Lock()
	as.waiting = true       // Set the scanning flag to true.
	as.missedAction = false // Reset the missedAction flag.
	as.mu.Unlock()

	// Wait 30 seconds before triggering a scan.
	// During this time, if another file action occurs, it will reset the timer after it has expired.
	<-time.After(as.waitTime)

	as.mu.Lock()
	// If a file action occurred while we were waiting, we will trigger another scan.
	if as.missedAction {
		as.logger.Trace().Msg("autoscanner: Missed file action")
		as.mu.Unlock()
		as.waitAndScan()
		return
	}

	as.waiting = false
	as.mu.Unlock()

	// Trigger a scan.
	as.scan()
}

// RunNow bypasses checks and triggers a scan immediately, even if the autoscanner is disabled.
func (as *AutoScanner) RunNow() {
	as.scan()
}

// scan is used to trigger a scan.
func (as *AutoScanner) scan() {
	defer util.HandlePanicInModuleThen("scanner/autoscanner/scan", func() {
		as.logger.Error().Msg("autoscanner: Recovered from panic")
	})

	// Create scan summary logger
	scanSummaryLogger := summary.NewScanSummaryLogger()

	as.logger.Trace().Msg("autoscanner: Starting scanner")
	as.wsEventManager.SendEvent(events.AutoScanStarted, nil)
	defer as.wsEventManager.SendEvent(events.AutoScanCompleted, nil)

	settings, err := as.db.GetSettings()
	if err != nil || settings == nil {
		as.logger.Error().Err(err).Msg("autoscanner: Failed to get settings")
		return
	}

	if settings.Library.LibraryPath == "" {
		as.logger.Error().Msg("autoscanner: Library path is not set")
		return
	}

	// Get existing local files
	existingLfs, _, err := db_bridge.GetLocalFiles(as.db)
	if err != nil {
		as.logger.Error().Err(err).Msg("autoscanner: Failed to get existing local files")
		return
	}

	// Create a new scan logger
	var scanLogger *scanner.ScanLogger
	if as.logsDir != "" {
		scanLogger, err = scanner.NewScanLogger(as.logsDir)
		if err != nil {
			as.logger.Error().Err(err).Msg("autoscanner: Failed to create scan logger")
			return
		}
		defer scanLogger.Done()
	}

	// Create a new scanner
	sc := scanner.Scanner{
		DirPath:            settings.Library.LibraryPath,
		OtherDirPaths:      settings.Library.LibraryPaths,
		Enhanced:           false, // Do not use enhanced mode for auto scanner.
		Platform:           as.platform,
		Logger:             as.logger,
		WSEventManager:     as.wsEventManager,
		ExistingLocalFiles: existingLfs,
		SkipLockedFiles:    true, // Skip locked files by default.
		SkipIgnoredFiles:   true,
		ScanSummaryLogger:  scanSummaryLogger,
		ScanLogger:         scanLogger,
		MetadataProvider:   as.metadataProvider,
		MatchingThreshold:  as.settings.ScannerMatchingThreshold,
		MatchingAlgorithm:  as.settings.ScannerMatchingAlgorithm,
	}

	allLfs, err := sc.Scan(context.Background())
	if err != nil {
		if errors.Is(err, scanner.ErrNoLocalFiles) {
			return
		} else {
			as.logger.Error().Err(err).Msg("autoscanner: Failed to scan library")
			return
		}
	}

	if as.db != nil && len(allLfs) > 0 {
		as.logger.Trace().Msg("autoscanner: Updating local files")

		// Insert the local files
		_, err = db_bridge.InsertLocalFiles(as.db, allLfs)
		if err != nil {
			as.logger.Error().Err(err).Msg("failed to insert local files")
			return
		}

	}

	// Save the scan summary
	err = db_bridge.InsertScanSummary(as.db, scanSummaryLogger.GenerateSummary())
	if err != nil {
		as.logger.Error().Err(err).Msg("failed to insert scan summary")
	}

	// Refresh the queue
	go as.autoDownloader.CleanUpDownloadedItems()

	notifier.GlobalNotifier.Notify(notifier.AutoScanner, "Your library has been scanned.")

	return
}