package service

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

	"go.uber.org/zap"

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

// existingVersionPaths returns existing destination files that represent the
// same media, combining two strategies and de-duplicating by path:
//
//  1. DB identity: media rows already scanned into the destination root whose
//     title (case-insensitive) + year [or + season/episode] match the source.
//     This is robust to directory case/layout differences.
//  2. Filesystem: video files inside the computed destination folder (matching
//     the SxxExx tag for episodes). Covers destinations that were not scanned.
func (o *OrganizerService) existingVersionPaths(ctx context.Context, destRoot, destDir, title, episodeTag string, year, season, episode int) []string {
	return mergeExistingVersionPaths(
		o.existingByIdentity(ctx, destRoot, title, year, season, episode),
		o.existingByFolder(destDir, episodeTag),
	)
}

func mergeExistingVersionPaths(groups ...[]string) []string {
	seen := map[string]struct{}{}
	var out []string
	add := func(p string) {
		if p == "" {
			return
		}
		c := filepath.Clean(p)
		if _, ok := seen[c]; ok {
			return
		}
		if _, err := os.Stat(c); err != nil {
			return
		}
		seen[c] = struct{}{}
		out = append(out, c)
	}
	for _, group := range groups {
		for _, p := range group {
			add(p)
		}
	}
	return out
}

func (o *OrganizerService) allExistingPathsInDB(ctx context.Context, paths []string) bool {
	if o == nil || o.repo == nil || o.repo.DB == nil || len(paths) == 0 {
		return false
	}
	cleaned := make([]string, 0, len(paths))
	seen := map[string]struct{}{}
	for _, path := range paths {
		path = filepath.Clean(strings.TrimSpace(path))
		if path == "" || path == "." {
			continue
		}
		if _, ok := seen[path]; ok {
			continue
		}
		seen[path] = struct{}{}
		cleaned = append(cleaned, path)
	}
	if len(cleaned) == 0 {
		return false
	}
	var count int64
	if err := o.repo.DB.WithContext(ctx).
		Model(&model.Media{}).
		Where("path IN ?", cleaned).
		Count(&count).Error; err != nil {
		return false
	}
	return count == int64(len(cleaned))
}

// existingByIdentity finds scanned destination media matching the parsed
// identity (case-insensitive title + year for movies; title + season/episode
// for episodes), located under destRoot.
func (o *OrganizerService) existingByIdentity(ctx context.Context, destRoot, title string, year, season, episode int) []string {
	if o.repo == nil || o.repo.DB == nil {
		return nil
	}
	title = strings.TrimSpace(title)
	if title == "" {
		return nil
	}
	q := o.repo.DB.WithContext(ctx).Model(&model.Media{}).
		Where("deleted_at IS NULL").
		Where("LOWER(title) = ?", strings.ToLower(title))
	if season > 0 || episode > 0 {
		q = q.Where("season_num = ? AND episode_num = ?", season, episode)
	} else if year > 0 {
		q = q.Where("year = ?", year)
	}
	var rows []model.Media
	if err := q.Find(&rows).Error; err != nil {
		return nil
	}
	var out []string
	for _, r := range rows {
		if r.Path != "" && pathWithin(r.Path, destRoot) {
			out = append(out, r.Path)
		}
	}
	return out
}

func (o *OrganizerService) existingByExternalIdentity(ctx context.Context, destRoot string, match *Match, season, episode int) []string {
	if o.repo == nil || o.repo.DB == nil || match == nil {
		return nil
	}
	var conds []string
	var args []any
	if match.TMDbID > 0 {
		conds = append(conds, "tm_db_id = ?")
		args = append(args, match.TMDbID)
	}
	if match.BangumiID > 0 {
		conds = append(conds, "bangumi_id = ?")
		args = append(args, match.BangumiID)
	}
	if strings.TrimSpace(match.DoubanID) != "" {
		conds = append(conds, "douban_id = ?")
		args = append(args, strings.TrimSpace(match.DoubanID))
	}
	if strings.TrimSpace(match.TheTVDBID) != "" {
		conds = append(conds, "thetvdb_id = ?")
		args = append(args, strings.TrimSpace(match.TheTVDBID))
	}
	if len(conds) == 0 {
		return nil
	}
	q := o.repo.DB.WithContext(ctx).Model(&model.Media{}).
		Where("deleted_at IS NULL").
		Where("("+strings.Join(conds, " OR ")+")", args...)
	if season > 0 || episode > 0 {
		q = q.Where("season_num = ? AND episode_num = ?", season, episode)
	}
	var rows []model.Media
	if err := q.Find(&rows).Error; err != nil {
		return nil
	}
	var out []string
	for _, row := range rows {
		if row.Path != "" && pathWithin(row.Path, destRoot) {
			out = append(out, row.Path)
		}
	}
	return out
}

// existingByFolder returns video files already present in destDir that
// represent the same media. For an episode (episodeTag != "") it matches files
// carrying the same SxxExx tag; for a movie it matches every video file in the
// movie folder.
func (o *OrganizerService) existingByFolder(destDir, episodeTag string) []string {
	entries, err := os.ReadDir(destDir)
	if err != nil {
		return nil
	}
	tag := strings.ToLower(episodeTag)
	var out []string
	for _, e := range entries {
		if e.IsDir() {
			continue
		}
		name := e.Name()
		if _, ok := videoExtensions[strings.ToLower(filepath.Ext(name))]; !ok {
			continue
		}
		if tag != "" && !strings.Contains(strings.ToLower(name), tag) {
			continue
		}
		out = append(out, filepath.Join(destDir, name))
	}
	return out
}

// replaceVersions removes the existing lower-resolution files (and their NFO
// sidecars + DB rows) and transfers src into dst.
func (o *OrganizerService) replaceVersions(ctx context.Context, src string, existing []string, dst string, mode TransferMode) error {
	for _, e := range existing {
		if err := os.Remove(e); err != nil && !os.IsNotExist(err) {
			return fmt.Errorf("remove existing %s: %w", e, err)
		}
		if nfo := nfoPath(e); nfo != "" {
			_ = os.Remove(nfo)
		}
		if o.repo != nil && o.repo.DB != nil {
			_ = o.repo.DB.WithContext(ctx).Where("path = ?", e).Delete(&model.Media{}).Error
		}
	}
	if err := os.MkdirAll(filepath.Dir(dst), 0o755); err != nil { // #nosec G301 -- organized media directories must remain readable by NAS/player users.
		return err
	}
	if err := transferFile(src, dst, mode); err != nil {
		return err
	}
	if err := transferSidecarNFO(src, dst, mode); err != nil {
		o.log.Warn("organize sidecar nfo failed",
			zap.String("from", src), zap.String("to", dst), zap.Error(err))
	}
	return nil
}

// resolutionArea returns the pixel area (width*height) of a video file for 洗版
// comparison. It prefers ffprobe; when unavailable it falls back to a
// resolution token in the filename (2160p/1080p/720p). Returns 0 when the
// resolution cannot be determined, in which case the caller treats the file as
// "unknown" and never performs a destructive replace.
func (o *OrganizerService) resolutionArea(ctx context.Context, path string) int {
	// Prefer a scanned media row's stored dimensions. The destination library
	// is normally scanned with ffprobe, so its files have accurate Width/Height
	// even after organize stripped the resolution token from the filename.
	if o.repo != nil && o.repo.DB != nil {
		var m model.Media
		if err := o.repo.DB.WithContext(ctx).
			Select("width", "height").
			Where("path = ?", path).
			Limit(1).Take(&m).Error; err == nil && m.Width > 0 && m.Height > 0 {
			return m.Width * m.Height
		}
	}
	if o.probe != nil {
		if pr, err := o.probe.Probe(ctx, path); err == nil && pr != nil && pr.Width > 0 && pr.Height > 0 {
			return pr.Width * pr.Height
		}
	}
	switch detectResolutionScore(strings.ToLower(filepath.Base(path))) {
	case 4:
		return 3840 * 2160
	case 3:
		return 1920 * 1080
	case 2:
		return 1280 * 720
	default:
		return 0
	}
}