package manager

import (
	"context"
	"errors"
	"fmt"
	"io/fs"
	"path/filepath"
	"regexp"
	"runtime/debug"
	"sync"
	"time"

	"github.com/99designs/gqlgen/graphql/handler/lru"
	"github.com/remeh/sizedwaitgroup"
	"github.com/stashapp/stash/internal/manager/config"
	"github.com/stashapp/stash/pkg/file"
	"github.com/stashapp/stash/pkg/file/video"
	"github.com/stashapp/stash/pkg/fsutil"
	"github.com/stashapp/stash/pkg/gallery"
	"github.com/stashapp/stash/pkg/image"
	"github.com/stashapp/stash/pkg/job"
	"github.com/stashapp/stash/pkg/logger"
	"github.com/stashapp/stash/pkg/models"
	"github.com/stashapp/stash/pkg/models/paths"
	"github.com/stashapp/stash/pkg/scene"
	"github.com/stashapp/stash/pkg/scene/generate"
	"github.com/stashapp/stash/pkg/txn"
)

type ScanJob struct {
	scanner       *file.Scanner
	input         ScanMetadataInput
	subscriptions *subscriptionManager

	fileQueue chan file.ScannedFile
	count     int
}

func (j *ScanJob) Execute(ctx context.Context, progress *job.Progress) error {
	cfg := config.GetInstance()
	input := j.input

	if job.IsCancelled(ctx) {
		logger.Info("Stopping due to user request")
		return nil
	}

	sp := getScanPaths(input.Paths)
	paths := make([]string, len(sp))
	for i, p := range sp {
		paths[i] = p.Path
	}

	mgr := GetInstance()
	c := mgr.Config
	repo := mgr.Repository

	start := time.Now()

	nTasks := cfg.GetParallelTasksWithAutoDetection()

	const taskQueueSize = 200000
	taskQueue := job.NewTaskQueue(ctx, progress, taskQueueSize, nTasks)

	var minModTime time.Time
	if j.input.Filter != nil && j.input.Filter.MinModTime != nil {
		minModTime = *j.input.Filter.MinModTime
	}

	// HACK - these should really be set in the scanner initialization
	j.scanner.FileHandlers = getScanHandlers(j.input, taskQueue, progress)
	j.scanner.ScanFilters = []file.PathFilter{newScanFilter(c, repo, minModTime)}
	j.scanner.HandlerRequiredFilters = []file.Filter{newHandlerRequiredFilter(cfg, repo)}

	j.runJob(ctx, paths, nTasks, progress)

	taskQueue.Close()

	if job.IsCancelled(ctx) {
		logger.Info("Stopping due to user request")
		return nil
	}

	elapsed := time.Since(start)
	logger.Info(fmt.Sprintf("Scan finished (%s)", elapsed))

	j.subscriptions.notify()
	return nil
}

func (j *ScanJob) runJob(ctx context.Context, paths []string, nTasks int, progress *job.Progress) {
	var wg sync.WaitGroup
	wg.Add(1)

	j.fileQueue = make(chan file.ScannedFile, scanQueueSize)

	go func() {
		defer func() {
			wg.Done()

			// handle panics in goroutine
			if p := recover(); p != nil {
				logger.Errorf("panic while queuing files for scan: %v", p)
				logger.Errorf(string(debug.Stack()))
			}
		}()

		if err := j.queueFiles(ctx, paths, progress); err != nil {
			if errors.Is(err, context.Canceled) {
				return
			}

			logger.Errorf("error queuing files for scan: %v", err)
			return
		}

		logger.Infof("Finished adding files to queue. %d files queued", j.count)
	}()

	defer wg.Wait()

	j.processQueue(ctx, nTasks, progress)
}

const scanQueueSize = 200000

func (j *ScanJob) queueFiles(ctx context.Context, paths []string, progress *job.Progress) error {
	fs := &file.OsFS{}

	defer func() {
		close(j.fileQueue)

		progress.AddTotal(j.count)
		progress.Definite()
	}()

	var err error
	progress.ExecuteTask("Walking directory tree", func() {
		for _, p := range paths {
			err = file.SymWalk(fs, p, j.queueFileFunc(ctx, fs, nil, progress))
			if err != nil {
				return
			}
		}
	})

	return err
}

func (j *ScanJob) queueFileFunc(ctx context.Context, f models.FS, zipFile *file.ScannedFile, progress *job.Progress) fs.WalkDirFunc {
	return func(path string, d fs.DirEntry, err error) error {
		if err != nil {
			// don't let errors prevent scanning
			logger.Errorf("error scanning %s: %v", path, err)
			return nil
		}

		if err = ctx.Err(); err != nil {
			return err
		}

		info, err := d.Info()
		if err != nil {
			logger.Errorf("reading info for %q: %v", path, err)
			return nil
		}

		if !j.scanner.AcceptEntry(ctx, path, info) {
			if info.IsDir() {
				logger.Debugf("Skipping directory %s", path)
				return fs.SkipDir
			}

			logger.Debugf("Skipping file %s", path)
			return nil
		}

		size, err := file.GetFileSize(f, path, info)
		if err != nil {
			return err
		}

		ff := file.ScannedFile{
			BaseFile: &models.BaseFile{
				DirEntry: models.DirEntry{
					ModTime: file.ModTime(info),
				},
				Path:     path,
				Basename: filepath.Base(path),
				Size:     size,
			},
			FS:   f,
			Info: info,
		}

		if zipFile != nil {
			ff.ZipFileID = &zipFile.ID
			ff.ZipFile = zipFile
		}

		if info.IsDir() {
			// handle folders immediately
			if err := j.handleFolder(ctx, ff, progress); err != nil {
				if !errors.Is(err, context.Canceled) {
					logger.Errorf("error processing %q: %v", path, err)
				}

				// skip the directory since we won't be able to process the files anyway
				return fs.SkipDir
			}

			return nil
		}

		// if zip file is present, we handle immediately
		if zipFile != nil {
			progress.ExecuteTask("Scanning "+path, func() {
				// don't increment progress in zip files
				if err := j.handleFile(ctx, ff, nil); err != nil {
					if !errors.Is(err, context.Canceled) {
						logger.Errorf("error processing %q: %v", path, err)
					}
					// don't return an error, just skip the file
				}
			})

			return nil
		}

		logger.Tracef("Queueing file %s for scanning", path)
		j.fileQueue <- ff

		j.count++

		return nil
	}
}

func (j *ScanJob) processQueue(ctx context.Context, parallelTasks int, progress *job.Progress) {
	if parallelTasks < 1 {
		parallelTasks = 1
	}

	wg := sizedwaitgroup.New(parallelTasks)

	func() {
		defer func() {
			wg.Wait()

			// handle panics in goroutine
			if p := recover(); p != nil {
				logger.Errorf("panic while scanning files: %v", p)
				logger.Errorf(string(debug.Stack()))
			}
		}()

		for f := range j.fileQueue {
			logger.Tracef("Processing queued file %s", f.Path)
			if err := ctx.Err(); err != nil {
				return
			}

			wg.Add()
			ff := f
			go func() {
				defer wg.Done()
				j.processQueueItem(ctx, ff, progress)
			}()
		}
	}()
}

func (j *ScanJob) processQueueItem(ctx context.Context, f file.ScannedFile, progress *job.Progress) {
	progress.ExecuteTask("Scanning "+f.Path, func() {
		var err error
		if f.Info.IsDir() {
			err = j.handleFolder(ctx, f, progress)
		} else {
			err = j.handleFile(ctx, f, progress)
		}

		if err != nil && !errors.Is(err, context.Canceled) {
			logger.Errorf("error processing %q: %v", f.Path, err)
		}
	})
}

func (j *ScanJob) handleFolder(ctx context.Context, f file.ScannedFile, progress *job.Progress) error {
	if progress != nil {
		defer progress.Increment()
	}

	_, err := j.scanner.ScanFolder(ctx, f)
	if err != nil {
		return err
	}

	return nil
}

func (j *ScanJob) handleFile(ctx context.Context, f file.ScannedFile, progress *job.Progress) error {
	if progress != nil {
		defer progress.Increment()
	}

	r, err := j.scanner.ScanFile(ctx, f)
	if err != nil {
		return err
	}

	// handle rename should have already handled the contents of the zip file
	// so shouldn't need to scan it again

	if (r.New || r.Updated) && j.scanner.IsZipFile(f.Info.Name()) {
		ff := r.File
		f.BaseFile = ff.Base()

		// scan zip files with a different context that is not cancellable
		// cancelling while scanning zip file contents results in the scan
		// contents being partially completed
		zipCtx := context.WithoutCancel(ctx)

		if err := j.scanZipFile(zipCtx, f, progress); err != nil {
			logger.Errorf("Error scanning zip file %q: %v", f.Path, err)
		}
	}

	return nil
}

func (j *ScanJob) scanZipFile(ctx context.Context, f file.ScannedFile, progress *job.Progress) error {
	zipFS, err := f.FS.OpenZip(f.Path, f.Size)
	if err != nil {
		if errors.Is(err, file.ErrNotReaderAt) {
			// can't walk the zip file
			// just return
			logger.Debugf("Skipping zip file %q as it cannot be opened for walking", f.Path)
			return nil
		}

		return err
	}

	defer zipFS.Close()

	return file.SymWalk(zipFS, f.Path, j.queueFileFunc(ctx, zipFS, &f, progress))
}

type extensionConfig struct {
	vidExt []string
	imgExt []string
	zipExt []string
}

func newExtensionConfig(c *config.Config) extensionConfig {
	return extensionConfig{
		vidExt: c.GetVideoExtensions(),
		imgExt: c.GetImageExtensions(),
		zipExt: c.GetGalleryExtensions(),
	}
}

type fileCounter interface {
	CountByFileID(ctx context.Context, fileID models.FileID) (int, error)
}

type galleryFinder interface {
	fileCounter
	FindByFolderID(ctx context.Context, folderID models.FolderID) ([]*models.Gallery, error)
}

type sceneFinder interface {
	fileCounter
	FindByPrimaryFileID(ctx context.Context, fileID models.FileID) ([]*models.Scene, error)
}

// handlerRequiredFilter returns true if a File's handler needs to be executed despite the file not being updated.
type handlerRequiredFilter struct {
	extensionConfig
	txnManager     txn.Manager
	SceneFinder    sceneFinder
	ImageFinder    fileCounter
	GalleryFinder  galleryFinder
	CaptionUpdater video.CaptionUpdater

	FolderCache *lru.LRU[bool]

	videoFileNamingAlgorithm models.HashAlgorithm
}

func newHandlerRequiredFilter(c *config.Config, repo models.Repository) *handlerRequiredFilter {
	processes := c.GetParallelTasksWithAutoDetection()

	return &handlerRequiredFilter{
		extensionConfig:          newExtensionConfig(c),
		txnManager:               repo.TxnManager,
		SceneFinder:              repo.Scene,
		ImageFinder:              repo.Image,
		GalleryFinder:            repo.Gallery,
		CaptionUpdater:           repo.File,
		FolderCache:              lru.New[bool](processes * 2),
		videoFileNamingAlgorithm: c.GetVideoFileNamingAlgorithm(),
	}
}

func (f *handlerRequiredFilter) Accept(ctx context.Context, ff models.File) bool {
	path := ff.Base().Path
	isVideoFile := useAsVideo(path)
	isImageFile := useAsImage(path)
	isZipFile := fsutil.MatchExtension(path, f.zipExt)

	var counter fileCounter

	switch {
	case isVideoFile:
		// return true if there are no scenes associated
		counter = f.SceneFinder
	case isImageFile:
		counter = f.ImageFinder
	case isZipFile:
		counter = f.GalleryFinder
	}

	if counter == nil {
		return false
	}

	n, err := counter.CountByFileID(ctx, ff.Base().ID)
	if err != nil {
		// just ignore
		return false
	}

	// execute handler if there are no related objects
	if n == 0 {
		return true
	}

	// if create galleries from folder is enabled and the file is not in a zip
	// file, then check if there is a folder-based gallery for the file's
	// directory
	// #4611 - also check for .forcegallery
	if isImageFile && ff.Base().ZipFileID == nil {
		// only do this for the first time it encounters the folder
		// the first instance should create the gallery
		_, found := f.FolderCache.Get(ctx, ff.Base().ParentFolderID.String())
		if found {
			// should already be handled
			return false
		}

		f.FolderCache.Add(ctx, ff.Base().ParentFolderID.String(), true)

		createGallery := instance.Config.GetCreateGalleriesFromFolders()
		if !createGallery {
			// check for presence of .forcegallery
			forceGalleryPath := filepath.Join(filepath.Dir(path), ".forcegallery")
			if exists, _ := fsutil.FileExists(forceGalleryPath); exists {
				createGallery = true
			}
		}

		if !createGallery {
			return false
		}

		g, _ := f.GalleryFinder.FindByFolderID(ctx, ff.Base().ParentFolderID)

		if len(g) == 0 {
			// no folder gallery. Return true so that it creates one.
			return true
		}
	}

	if isVideoFile {
		// TODO - check if the cover exists
		// hash := scene.GetHash(ff, f.videoFileNamingAlgorithm)
		// ssPath := instance.Paths.Scene.GetScreenshotPath(hash)
		// if exists, _ := fsutil.FileExists(ssPath); !exists {
		// 	// if not, check if the file is a primary file for a scene
		// 	scenes, err := f.SceneFinder.FindByPrimaryFileID(ctx, ff.Base().ID)
		// 	if err != nil {
		// 		// just ignore
		// 		return false
		// 	}

		// 	if len(scenes) > 0 {
		// 		// if it is, then it needs to be re-generated
		// 		return true
		// 	}
		// }

		// clean captions - scene handler handles this as well, but
		// unchanged files aren't processed by the scene handler
		videoFile, _ := ff.(*models.VideoFile)
		if videoFile != nil {
			if err := video.CleanCaptions(ctx, videoFile, f.txnManager, f.CaptionUpdater); err != nil {
				logger.Errorf("Error cleaning captions: %v", err)
			}
		}
	}

	return false
}

type scanFilter struct {
	extensionConfig
	txnManager     txn.Manager
	FileFinder     models.FileFinder
	CaptionUpdater video.CaptionUpdater

	stashPaths        config.StashConfigs
	generatedPath     string
	videoExcludeRegex []*regexp.Regexp
	imageExcludeRegex []*regexp.Regexp
	minModTime        time.Time
}

func newScanFilter(c *config.Config, repo models.Repository, minModTime time.Time) *scanFilter {
	return &scanFilter{
		extensionConfig:   newExtensionConfig(c),
		txnManager:        repo.TxnManager,
		FileFinder:        repo.File,
		CaptionUpdater:    repo.File,
		stashPaths:        c.GetStashPaths(),
		generatedPath:     c.GetGeneratedPath(),
		videoExcludeRegex: generateRegexps(c.GetExcludes()),
		imageExcludeRegex: generateRegexps(c.GetImageExcludes()),
		minModTime:        minModTime,
	}
}

func (f *scanFilter) Accept(ctx context.Context, path string, info fs.FileInfo) bool {
	if fsutil.IsPathInDir(f.generatedPath, path) {
		logger.Warnf("Skipping %q as it overlaps with the generated folder", path)
		return false
	}

	// exit early on cutoff
	if info.Mode().IsRegular() && info.ModTime().Before(f.minModTime) {
		return false
	}

	s := f.stashPaths.GetStashFromDirPath(path)
	if s == nil {
		logger.Debugf("Skipping %s as it is not in the stash library", path)
		return false
	}

	isVideoFile := useAsVideo(path)
	isImageFile := useAsImage(path)
	isZipFile := fsutil.MatchExtension(path, f.zipExt)

	// handle caption files
	if fsutil.MatchExtension(path, video.CaptionExts) {
		// we don't include caption files in the file scan, but we do need
		// to handle them
		video.AssociateCaptions(ctx, path, f.txnManager, f.FileFinder, f.CaptionUpdater)

		return false
	}

	if !info.IsDir() && !isVideoFile && !isImageFile && !isZipFile {
		logger.Debugf("Skipping %s as it does not match any known file extensions", path)
		return false
	}

	// #1756 - skip zero length files
	if !info.IsDir() && info.Size() == 0 {
		logger.Infof("Skipping zero-length file: %s", path)
		return false
	}

	// shortcut: skip the directory entirely if it matches both exclusion patterns
	// add a trailing separator so that it correctly matches against patterns like path/.*
	pathExcludeTest := path + string(filepath.Separator)
	if (matchFileRegex(pathExcludeTest, f.videoExcludeRegex)) && (s.ExcludeImage || matchFileRegex(pathExcludeTest, f.imageExcludeRegex)) {
		logger.Debugf("Skipping directory %s as it matches video and image exclusion patterns", path)
		return false
	}

	if isVideoFile && (s.ExcludeVideo || matchFileRegex(path, f.videoExcludeRegex)) {
		logger.Debugf("Skipping %s as it matches video exclusion patterns", path)
		return false
	} else if (isImageFile || isZipFile) && (s.ExcludeImage || matchFileRegex(path, f.imageExcludeRegex)) {
		logger.Debugf("Skipping %s as it matches image exclusion patterns", path)
		return false
	}

	return true
}

type scanConfig struct {
	isGenerateThumbnails   bool
	isGenerateClipPreviews bool

	createGalleriesFromFolders bool
}

func (c *scanConfig) GetCreateGalleriesFromFolders() bool {
	return c.createGalleriesFromFolders
}

func videoFileFilter(ctx context.Context, f models.File) bool {
	return useAsVideo(f.Base().Path)
}

func imageFileFilter(ctx context.Context, f models.File) bool {
	return useAsImage(f.Base().Path)
}

func galleryFileFilter(ctx context.Context, f models.File) bool {
	return isZip(f.Base().Basename)
}

func getScanHandlers(options ScanMetadataInput, taskQueue *job.TaskQueue, progress *job.Progress) []file.Handler {
	mgr := GetInstance()
	c := mgr.Config
	r := mgr.Repository
	pluginCache := mgr.PluginCache

	return []file.Handler{
		&file.FilteredHandler{
			Filter: file.FilterFunc(imageFileFilter),
			Handler: &image.ScanHandler{
				CreatorUpdater: r.Image,
				GalleryFinder:  r.Gallery,
				ScanGenerator: &imageGenerators{
					input:              options,
					taskQueue:          taskQueue,
					progress:           progress,
					paths:              mgr.Paths,
					sequentialScanning: c.GetSequentialScanning(),
				},
				ScanConfig: &scanConfig{
					isGenerateThumbnails:       options.ScanGenerateThumbnails,
					isGenerateClipPreviews:     options.ScanGenerateClipPreviews,
					createGalleriesFromFolders: c.GetCreateGalleriesFromFolders(),
				},
				PluginCache: pluginCache,
				Paths:       instance.Paths,
			},
		},
		&file.FilteredHandler{
			Filter: file.FilterFunc(galleryFileFilter),
			Handler: &gallery.ScanHandler{
				CreatorUpdater:     r.Gallery,
				SceneFinderUpdater: r.Scene,
				ImageFinderUpdater: r.Image,
				PluginCache:        pluginCache,
			},
		},
		&file.FilteredHandler{
			Filter: file.FilterFunc(videoFileFilter),
			Handler: &scene.ScanHandler{
				CreatorUpdater: r.Scene,
				CaptionUpdater: r.File,
				PluginCache:    pluginCache,
				ScanGenerator: &sceneGenerators{
					input:               options,
					taskQueue:           taskQueue,
					progress:            progress,
					paths:               mgr.Paths,
					fileNamingAlgorithm: c.GetVideoFileNamingAlgorithm(),
					sequentialScanning:  c.GetSequentialScanning(),
				},
				FileNamingAlgorithm: c.GetVideoFileNamingAlgorithm(),
				Paths:               mgr.Paths,
			},
		},
	}
}

type imageGenerators struct {
	input     ScanMetadataInput
	taskQueue *job.TaskQueue
	progress  *job.Progress

	paths              *paths.Paths
	sequentialScanning bool
}

func (g *imageGenerators) Generate(ctx context.Context, i *models.Image, f models.File) error {
	const overwrite = false

	progress := g.progress
	t := g.input
	path := f.Base().Path

	// this is a bit of a hack: the task requires files to be loaded, but
	// we don't really need to since we already have the file
	ii := *i
	ii.Files = models.NewRelatedFiles([]models.File{f})

	if t.ScanGenerateThumbnails {
		// this should be quick, so always generate sequentially
		taskThumbnail := GenerateImageThumbnailTask{
			Image:     ii,
			Overwrite: overwrite,
		}

		taskThumbnail.Start(ctx)
	}

	// avoid adding a task if the file isn't a video file
	_, isVideo := f.(*models.VideoFile)
	if isVideo && t.ScanGenerateClipPreviews {
		progress.AddTotal(1)
		previewsFn := func(ctx context.Context) {
			taskPreview := GenerateClipPreviewTask{
				Image:     ii,
				Overwrite: overwrite,
			}

			taskPreview.Start(ctx)
			progress.Increment()
		}

		if g.sequentialScanning {
			previewsFn(ctx)
		} else {
			g.taskQueue.Add(fmt.Sprintf("Generating preview for %s", path), previewsFn)
		}
	}

	if t.ScanGenerateImagePhashes {
		progress.AddTotal(1)
		phashFn := func(ctx context.Context) {
			mgr := GetInstance()
			// Only generate phash for image files, not video files
			if imageFile, ok := f.(*models.ImageFile); ok {
				taskPhash := GenerateImagePhashTask{
					repository: mgr.Repository,
					File:       imageFile,
					Overwrite:  overwrite,
				}
				taskPhash.Start(ctx)
			}
			progress.Increment()
		}

		if g.sequentialScanning {
			phashFn(ctx)
		} else {
			g.taskQueue.Add(fmt.Sprintf("Generating phash for %s", path), phashFn)
		}
	}

	return nil
}

type sceneGenerators struct {
	input     ScanMetadataInput
	taskQueue *job.TaskQueue
	progress  *job.Progress

	paths               *paths.Paths
	fileNamingAlgorithm models.HashAlgorithm
	sequentialScanning  bool
}

func (g *sceneGenerators) Generate(ctx context.Context, s *models.Scene, f *models.VideoFile) error {
	const overwrite = false

	progress := g.progress
	t := g.input
	path := f.Path

	mgr := GetInstance()

	if t.ScanGenerateSprites {
		progress.AddTotal(1)
		spriteFn := func(ctx context.Context) {
			taskSprite := GenerateSpriteTask{
				Scene:               *s,
				Overwrite:           overwrite,
				fileNamingAlgorithm: g.fileNamingAlgorithm,
			}
			taskSprite.Start(ctx)
			progress.Increment()
		}

		if g.sequentialScanning {
			spriteFn(ctx)
		} else {
			g.taskQueue.Add(fmt.Sprintf("Generating sprites for %s", path), spriteFn)
		}
	}

	if t.ScanGeneratePhashes {
		progress.AddTotal(1)
		phashFn := func(ctx context.Context) {
			taskPhash := GeneratePhashTask{
				repository:          mgr.Repository,
				File:                f,
				Overwrite:           overwrite,
				fileNamingAlgorithm: g.fileNamingAlgorithm,
			}
			taskPhash.Start(ctx)
			progress.Increment()
		}

		if g.sequentialScanning {
			phashFn(ctx)
		} else {
			g.taskQueue.Add(fmt.Sprintf("Generating phash for %s", path), phashFn)
		}
	}

	if t.ScanGeneratePreviews {
		progress.AddTotal(1)
		previewsFn := func(ctx context.Context) {
			options := getGeneratePreviewOptions(GeneratePreviewOptionsInput{})

			generator := &generate.Generator{
				Encoder:      mgr.FFMpeg,
				FFMpegConfig: mgr.Config,
				LockManager:  mgr.ReadLockManager,
				MarkerPaths:  g.paths.SceneMarkers,
				ScenePaths:   g.paths.Scene,
				Overwrite:    overwrite,
			}

			taskPreview := GeneratePreviewTask{
				Scene:               *s,
				ImagePreview:        t.ScanGenerateImagePreviews,
				Options:             options,
				Overwrite:           overwrite,
				fileNamingAlgorithm: g.fileNamingAlgorithm,
				generator:           generator,
			}
			taskPreview.Start(ctx)
			progress.Increment()
		}

		if g.sequentialScanning {
			previewsFn(ctx)
		} else {
			g.taskQueue.Add(fmt.Sprintf("Generating preview for %s", path), previewsFn)
		}
	}

	if t.ScanGenerateCovers {
		progress.AddTotal(1)
		g.taskQueue.Add(fmt.Sprintf("Generating cover for %s", path), func(ctx context.Context) {
			taskCover := GenerateCoverTask{
				repository: mgr.Repository,
				Scene:      *s,
				Overwrite:  overwrite,
			}
			taskCover.Start(ctx)
			progress.Increment()
		})
	}

	return nil
}