package service

import (
	"context"
	"fmt"
	"path/filepath"
	"strings"
	"sync"

	"go.uber.org/zap"

	"github.com/ShukeBta/MediaStationGo/internal/model"
)

func (s *ScannerService) scanCloudLibrary(ctx context.Context, lib *model.Library, mount CloudMountInfo, autoScrape bool) (*ScanResult, error) {
	res := &ScanResult{LibraryID: lib.ID}
	if s.storage == nil {
		return res, fmt.Errorf("cloud storage service unavailable")
	}

	cfg, err := s.repo.StorageConfig.Get(ctx, mount.Provider)
	if err != nil || cfg == nil {
		return res, fmt.Errorf("storage config not found: %s", mount.Provider)
	}
	if !cfg.Enabled {
		return res, fmt.Errorf("storage %s is disabled", mount.Provider)
	}
	typ := mount.Provider
	rootDir := mount.ScanDir
	rootDisplayDir := mount.DisplayDir
	autoCategoryRoot := cloudRootMountNeedsAutoCategory(mount)
	scopeIDs := s.cloudScanLibraryScopeIDs(ctx, lib, mount)
	seen := make(map[string]struct{})
	seenRefs := make(map[string]struct{})
	candidates := make([]cloudCandidate, 0, 256)
	candidateByKey := make(map[string]int)
	visitedDirs := map[string]struct{}{}
	progress := newCloudScanProgressState()
	var stateMu sync.Mutex
	progress.publish(s, lib.ID, res, "listing", true)
	var walkWG sync.WaitGroup
	var walkErr error
	var walkErrOnce sync.Once
	setWalkErr := func(err error) {
		if err != nil {
			walkErrOnce.Do(func() {
				walkErr = err
			})
		}
	}
	listSlots := make(chan struct{}, s.cloudScanWorkerCount())
	var walkCloud func(dirID, displayDir string, inheritedMeta *LocalMetadata) error
	walkCloud = func(dirID, displayDir string, inheritedMeta *LocalMetadata) error {
		defer walkWG.Done()
		if err := ctx.Err(); err != nil {
			setWalkErr(err)
			return err
		}
		stateMu.Lock()
		if _, ok := visitedDirs[dirID]; ok {
			stateMu.Unlock()
			return nil
		}
		visitedDirs[dirID] = struct{}{}
		stateMu.Unlock()

		select {
		case listSlots <- struct{}{}:
			defer func() { <-listSlots }()
		case <-ctx.Done():
			setWalkErr(ctx.Err())
			return ctx.Err()
		}
		entries, err := s.storage.CloudList(ctx, typ, dirID)
		if err != nil {
			if dirID != rootDir {
				progress.addSkipped(res)
				s.log.Warn("skip inaccessible cloud directory",
					zap.String("library_id", lib.ID),
					zap.String("provider", typ),
					zap.String("dir", dirID),
					zap.Error(err))
				return nil
			}
			setWalkErr(err)
			return err
		}
		progress.publish(s, lib.ID, res, "listing", progress.markDirVisited())
		sidecars := newCloudSidecarSet(typ, entries)
		dirMeta := s.cloudDirectoryMetadata(ctx, typ, displayDir, sidecars, inheritedMeta)
		s.cacheCloudMetadataArtworkNow(ctx, dirMeta)
		for _, entry := range entries {
			select {
			case <-ctx.Done():
				setWalkErr(ctx.Err())
				return ctx.Err()
			default:
			}
			if entry.IsDir {
				if strings.TrimSpace(entry.ID) != "" {
					walkWG.Add(1)
					go func(childID, childDisplay string, childMeta *LocalMetadata) {
						_ = walkCloud(childID, childDisplay, childMeta)
					}(entry.ID, joinCloudDisplayPath(displayDir, entry.Name), dirMeta)
				}
				continue
			}
			ext := strings.ToLower(filepath.Ext(entry.Name))
			if _, ok := videoExtensions[ext]; !ok {
				continue
			}
			ref := cloudEntryRef(typ, entry.ID, entry.PickCode)
			if ref == "" {
				progress.addSkipped(res)
				continue
			}
			stateMu.Lock()
			if _, ok := seenRefs[ref]; ok {
				stateMu.Unlock()
				progress.addSkipped(res)
				continue
			}
			seenRefs[ref] = struct{}{}
			stateMu.Unlock()
			progress.publish(s, lib.ID, res, "listing", progress.markFileDiscovered())
			displayPath := joinCloudDisplayPath(displayDir, entry.Name)
			path := cloudMediaPath(typ, displayPath)
			localMeta := s.cloudFileMetadata(ctx, typ, displayPath, entry.Name, sidecars, dirMeta, librarySupportsSeasons(lib))
			localMeta = s.enrichCloudMetadataFromExternalIDs(ctx, lib, path, localMeta)
			if localMeta != nil {
				s.cacheCloudMetadataArtworkNow(ctx, localMeta)
			}
			candidate := cloudCandidate{
				ref:       ref,
				name:      entry.Name,
				size:      entry.Size,
				path:      path,
				localMeta: localMeta,
			}
			if autoCategoryRoot {
				candidate.categoryDisplayDir = cloudAutoCategoryDisplayDirForMediaPath(path)
			}
			key := cloudMediaDedupeKey(lib, displayDir, entry.Name, entry.Size)
			stateMu.Lock()
			if key != "" {
				if prevIndex, ok := candidateByKey[key]; ok {
					if candidate.size > candidates[prevIndex].size {
						candidates[prevIndex] = candidate
					}
					stateMu.Unlock()
					progress.addSkipped(res)
					continue
				}
				candidateByKey[key] = len(candidates)
			}
			candidates = append(candidates, candidate)
			stateMu.Unlock()
		}
		return nil
	}
	walkWG.Add(1)
	go func() {
		_ = walkCloud(rootDir, rootDisplayDir, nil)
	}()
	walkWG.Wait()
	if walkErr != nil {
		return res, walkErr
	}
	if err := ctx.Err(); err != nil {
		return res, err
	}
	existingMedia, err := s.existingCloudMediaSnapshotForLibraries(ctx, scopeIDs)
	if err != nil {
		s.log.Warn("load existing cloud media snapshot failed", zap.String("library_id", lib.ID), zap.Error(err))
		existingMedia = nil
	}
	sortCloudCandidatesByRefreshPriority(candidates, existingMedia)
	writeBatch := newLocalMediaWriteBatch(s, ctx, res, 100)
	probeBudget := maxCloudMediaProbeQueuePerScan
	targetLibs := map[string]*model.Library{"": lib}
	touchedLibraryIDs := []string{}
	for _, candidate := range candidates {
		select {
		case <-ctx.Done():
			return res, ctx.Err()
		default:
		}
		targetLib := lib
		if candidate.categoryDisplayDir != "" {
			if cached, ok := targetLibs[candidate.categoryDisplayDir]; ok {
				targetLib = cached
			} else if categoryLib, err := s.ensureCloudAutoCategoryLibrary(ctx, lib, typ, candidate.categoryDisplayDir); err == nil && categoryLib != nil {
				targetLib = categoryLib
				targetLibs[candidate.categoryDisplayDir] = categoryLib
				scopeIDs = appendUniqueLibraryIDs(scopeIDs, categoryLib.ID)
			} else if err != nil {
				s.log.Warn("ensure cloud auto category library failed",
					zap.String("library_id", lib.ID),
					zap.String("provider", typ),
					zap.String("category", candidate.categoryDisplayDir),
					zap.Error(err))
			}
		}
		touchedLibraryIDs = appendUniqueLibraryIDs(touchedLibraryIDs, targetLib.ID)
		seen[candidate.path] = struct{}{}
		s.ingestCloudFile(ctx, targetLib, typ, candidate.ref, candidate.path, candidate.name, candidate.size, candidate.localMeta, existingMedia, writeBatch, &probeBudget, res)
		progress.publish(s, lib.ID, res, "importing", res.Visited == 1 || res.Visited%100 == 0)
	}
	writeBatch.Flush()
	removed, err := s.pruneMissingCloudMediaForLibraries(ctx, scopeIDs, seen)
	if err != nil {
		s.log.Warn("prune missing cloud media failed", zap.String("library_id", lib.ID), zap.Error(err))
	} else {
		res.Removed = removed
	}
	publishCloudScanFinished(s, lib.ID, res, progress)
	s.invalidateMediaCache(ctx)
	for _, targetID := range appendUniqueLibraryIDs(touchedLibraryIDs, lib.ID) {
		s.maybeGenerateSTRMAfterScan(targetID)
	}
	if scanHasImportChanges(res) && autoScrape && s.scraper != nil && s.scraper.AnyEnabled() && s.autoScrapeEnabled(ctx) {
		for _, targetID := range appendUniqueLibraryIDs(touchedLibraryIDs, lib.ID) {
			s.startAutoScrape(ctx, targetID)
		}
	}
	return res, nil
}

func scanHasImportChanges(res *ScanResult) bool {
	return res != nil && (res.Added > 0 || res.Updated > 0 || res.Removed > 0)
}