package importmedia

import (
	"fmt"
	"os"
	"path/filepath"
	"regexp"
	"sort"
	"strings"
)

var (
	seriesSxxExx = regexp.MustCompile(`(?i)(?:^|[^a-z0-9])S(\d{1,2})E(\d{1,3})(?:[^a-z0-9]|$)`)
	seriesNxNN   = regexp.MustCompile(`(?i)(?:^|[^a-z0-9])(\d{1,2})x(\d{1,3})(?:[^a-z0-9]|$)`)
)

type SeriesEpisodeSpec struct {
	EpisodeNumber int
	EpisodeTitle  string
}

type SeriesEpisodeResult struct {
	EpisodeNumber int
	ImportedPath  string
	SubtitlePath  string
}

type SeriesResult struct {
	// Season directory path
	ImportedPath string
	Episodes     []SeriesEpisodeResult
	SubtitlePath string // single-episode subtitle, if any
}

type SeriesOptions struct {
	SourcePath    string
	ShowDir       string // …/Show Name (Year)
	ShowTitle     string
	Year          *int
	SeasonNumber  int
	Episodes      []SeriesEpisodeSpec
	ReleaseTags   string
	QualityHint   string
	Subtitle      *SubtitleFile // only applied when exactly one episode imported
}

// ImportSeries moves episode videos into Show/Season XX/ with scanner-friendly names.
func ImportSeries(opts SeriesOptions) (*SeriesResult, error) {
	sourcePath := filepath.Clean(strings.TrimSpace(opts.SourcePath))
	showDir := filepath.Clean(strings.TrimSpace(opts.ShowDir))
	if sourcePath == "" || showDir == "" {
		return nil, fmt.Errorf("source/show pad ontbreekt")
	}
	if opts.SeasonNumber <= 0 {
		return nil, fmt.Errorf("ongeldig seizoen")
	}
	if len(opts.Episodes) == 0 {
		return nil, fmt.Errorf("geen afleveringen opgegeven")
	}

	wanted := map[int]SeriesEpisodeSpec{}
	for _, ep := range opts.Episodes {
		if ep.EpisodeNumber > 0 {
			wanted[ep.EpisodeNumber] = ep
		}
	}
	if len(wanted) == 0 {
		return nil, fmt.Errorf("geen geldige afleveringnummers")
	}

	videos, err := listVideos(sourcePath)
	if err != nil {
		return nil, err
	}
	if len(videos) == 0 {
		return nil, fmt.Errorf("geen videobestanden in download")
	}

	seasonDir := filepath.Join(showDir, fmt.Sprintf("Season %02d", opts.SeasonNumber))
	if err := os.MkdirAll(seasonDir, 0o755); err != nil {
		return nil, fmt.Errorf("seizoensmap aanmaken: %w", err)
	}

	// Map episode number → source video path
	matched := map[int]string{}
	unparsed := []string{}

	for _, video := range videos {
		base := filepath.Base(video)
		epNum := parseEpisodeNumber(base)
		if epNum <= 0 {
			unparsed = append(unparsed, video)
			continue
		}
		if _, ok := wanted[epNum]; !ok {
			continue
		}
		// Prefer larger file if duplicate episode numbers
		if prev, ok := matched[epNum]; ok {
			if fileSize(video) <= fileSize(prev) {
				continue
			}
		}
		matched[epNum] = video
	}

	// Single-episode job with one video and no SxxExx in name → accept that file
	if len(wanted) == 1 && len(matched) == 0 && len(videos) == 1 {
		for num := range wanted {
			matched[num] = videos[0]
		}
	} else if len(wanted) == 1 && len(matched) == 0 && len(unparsed) == 1 && len(videos) == 1 {
		for num := range wanted {
			matched[num] = unparsed[0]
		}
	}

	if len(matched) == 0 {
		return nil, fmt.Errorf("geen afleveringen herkend in download (verwacht S%02dExx in bestandsnaam)", opts.SeasonNumber)
	}

	showBase := sanitizeName(opts.ShowTitle)
	tags := strings.TrimSpace(opts.ReleaseTags)
	if tags == "" {
		tags = strings.TrimSpace(opts.QualityHint)
	}
	tags = sanitizeName(tags)

	results := make([]SeriesEpisodeResult, 0, len(matched))
	moved := make([]string, 0, len(matched))

	nums := make([]int, 0, len(matched))
	for n := range matched {
		nums = append(nums, n)
	}
	sort.Ints(nums)

	for _, epNum := range nums {
		src := matched[epNum]
		spec := wanted[epNum]
		ext := strings.ToLower(filepath.Ext(src))
		epCode := fmt.Sprintf("S%02dE%02d", opts.SeasonNumber, epNum)
		name := showBase + " - " + epCode
		if t := sanitizeName(spec.EpisodeTitle); t != "" {
			name += " - " + t
		}
		if tags != "" {
			name += " - " + tags
		}
		destPath := filepath.Join(seasonDir, name+ext)
		if err := moveFile(src, destPath); err != nil {
			return nil, fmt.Errorf("verplaatsen E%02d: %w", epNum, err)
		}
		moved = append(moved, src)
		results = append(results, SeriesEpisodeResult{
			EpisodeNumber: epNum,
			ImportedPath:  destPath,
		})
	}

	out := &SeriesResult{
		ImportedPath: seasonDir,
		Episodes:     results,
	}

	// Single episode + subtitle sidecar
	if opts.Subtitle != nil && len(opts.Subtitle.Content) > 0 && len(results) == 1 {
		subPath, err := WriteSidecar(results[0].ImportedPath, opts.Subtitle)
		if err != nil {
			return nil, err
		}
		results[0].SubtitlePath = subPath
		out.SubtitlePath = subPath
		out.Episodes = results
	}

	cleanupMovedSources(sourcePath, moved)
	return out, nil
}

func parseEpisodeNumber(name string) int {
	if m := seriesSxxExx.FindStringSubmatch(name); len(m) >= 3 {
		return atoi(m[2])
	}
	if m := seriesNxNN.FindStringSubmatch(name); len(m) >= 3 {
		return atoi(m[2])
	}
	return 0
}

func listVideos(sourcePath string) ([]string, error) {
	info, err := os.Stat(sourcePath)
	if err != nil {
		return nil, fmt.Errorf("bron niet gevonden: %w", err)
	}
	var out []string
	consider := func(path string) {
		if !videoExt[strings.ToLower(filepath.Ext(path))] {
			return
		}
		if sampleRe.MatchString(filepath.Base(path)) {
			return
		}
		out = append(out, path)
	}
	if !info.IsDir() {
		consider(sourcePath)
		return out, nil
	}
	err = filepath.Walk(sourcePath, func(path string, fi os.FileInfo, walkErr error) error {
		if walkErr != nil || fi == nil || fi.IsDir() {
			return nil
		}
		consider(path)
		return nil
	})
	return out, err
}

func fileSize(path string) int64 {
	fi, err := os.Stat(path)
	if err != nil {
		return 0
	}
	return fi.Size()
}

func atoi(s string) int {
	n := 0
	for _, c := range s {
		if c < '0' || c > '9' {
			break
		}
		n = n*10 + int(c-'0')
	}
	return n
}

// Remove moved sources and empty dirs; leave unmatched videos alone if still present.
func cleanupMovedSources(sourcePath string, moved []string) {
	movedSet := map[string]bool{}
	for _, m := range moved {
		movedSet[m] = true
	}
	info, err := os.Stat(sourcePath)
	if err != nil {
		return
	}
	if !info.IsDir() {
		if movedSet[sourcePath] {
			_ = os.Remove(sourcePath)
		}
		_ = removeEmptyDirs(filepath.Dir(sourcePath))
		return
	}
	// Remove leftover nfo/txt/samples next to moved content, but keep unmatched videos
	_ = filepath.Walk(sourcePath, func(path string, fi os.FileInfo, walkErr error) error {
		if walkErr != nil || fi == nil || fi.IsDir() {
			return nil
		}
		if movedSet[path] {
			return nil // already moved away
		}
		base := filepath.Base(path)
		ext := strings.ToLower(filepath.Ext(base))
		if sampleRe.MatchString(base) || ext == ".nfo" || ext == ".txt" || ext == ".jpg" || ext == ".png" {
			_ = os.Remove(path)
		}
		return nil
	})
	_ = removeEmptyDirs(sourcePath)
}