package web

import (
	"bufio"
	"database/sql"
	"fmt"
	"net/http"
	"path/filepath"
	"strings"

	"git.noroutes.net/NoRoutes/vibetunes/internal/auth"
	"git.noroutes.net/NoRoutes/vibetunes/internal/database"
)

// handlePlaylistExport streams a playlist out as a standard M3U8 file:
// an #EXTM3U header, an #EXTINF duration/title line per track, and the
// track's absolute on-disk path (folder root + relative path) so a
// re-import against the same library's folders resolves cleanly.
func (h *Web) handlePlaylistExport(w http.ResponseWriter, r *http.Request) {
	user := auth.UserFromContext(r.Context())
	id := r.PathValue("id")
	playlist, err := database.GetPlaylist(h.DB, id)
	if err != nil {
		http.NotFound(w, r)
		return
	}
	if playlist.OwnerID != user.ID && !playlist.IsPublic {
		http.Error(w, "403 Forbidden", http.StatusForbidden)
		return
	}
	entries, err := database.ListPlaylistEntries(h.DB, id)
	if err != nil {
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}

	folders, err := database.ListMusicFolders(h.DB)
	if err != nil {
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	folderByID := make(map[string]*database.MusicFolder, len(folders))
	for _, f := range folders {
		folderByID[f.ID] = f
	}

	filename := sanitizeFilename(playlist.Name) + ".m3u8"
	w.Header().Set("Content-Type", "audio/x-mpegurl; charset=utf-8")
	w.Header().Set("Content-Disposition", fmt.Sprintf(`attachment; filename="%s"`, filename))

	buf := bufio.NewWriter(w)
	defer buf.Flush()
	buf.WriteString("#EXTM3U\n")
	for _, e := range entries {
		song, err := database.GetSong(h.DB, e.SongID)
		if err != nil {
			continue
		}
		mf, err := database.GetMediaFile(h.DB, song.MediaFileID)
		if err != nil {
			continue
		}
		folder, ok := folderByID[mf.MusicFolderID]
		if !ok {
			continue
		}
		artist := ""
		if a := albumOf(h.DB, song); a != nil && a.PrimaryAlbumArtistID.Valid {
			if art, err := database.GetArtist(h.DB, a.PrimaryAlbumArtistID.String); err == nil {
				artist = art.Name
			}
		}
		title := song.Title
		if artist != "" {
			title = artist + " - " + title
		}
		fmt.Fprintf(buf, "#EXTINF:%d,%s\n", int(mf.DurationSeconds), title)
		buf.WriteString(filepath.Join(folder.Path, mf.RelativePath))
		buf.WriteString("\n")
	}
}

// handlePlaylistImportForm renders the upload form.
func (h *Web) handlePlaylistImportForm(w http.ResponseWriter, r *http.Request) {
	h.page(w, r, "playlist_import", "playlists", "Import Playlist", nil)
}

// playlistImportResult is the summary shown after an import: how many
// M3U entries matched a track in the library versus were skipped.
type playlistImportResult struct {
	Playlist *database.Playlist
	Matched  int
	Skipped  int
}

// handlePlaylistImport accepts an uploaded .m3u/.m3u8 file, resolves each
// entry to a song already known to the library (matching by absolute
// path against a scanned music folder's root, falling back to a
// filename-only match within that folder), and creates a new playlist
// from whatever matched. Unmatched lines are reported, not treated as an
// error — a partial match is still useful to the user.
func (h *Web) handlePlaylistImport(w http.ResponseWriter, r *http.Request) {
	user := auth.UserFromContext(r.Context())
	if err := r.ParseMultipartForm(4 << 20); err != nil {
		http.Error(w, "bad request", http.StatusBadRequest)
		return
	}
	file, header, err := r.FormFile("file")
	if err != nil {
		http.Error(w, "no file uploaded", http.StatusBadRequest)
		return
	}
	defer file.Close()

	folders, err := database.ListMusicFolders(h.DB)
	if err != nil {
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}

	name := strings.TrimSuffix(header.Filename, filepath.Ext(header.Filename))
	if name == "" {
		name = "Imported Playlist"
	}
	playlist, err := database.CreatePlaylist(h.DB, user.ID, name, "", false)
	if err != nil {
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}

	matched, skipped := 0, 0
	scanner := bufio.NewScanner(file)
	for scanner.Scan() {
		line := strings.TrimSpace(scanner.Text())
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}
		song := resolvePlaylistImportLine(h.DB, folders, line)
		if song == nil {
			skipped++
			continue
		}
		if err := database.AppendPlaylistEntry(h.DB, playlist.ID, song.ID); err != nil {
			skipped++
			continue
		}
		matched++
	}

	h.page(w, r, "playlist_import_result", "playlists", "Import Result", playlistImportResult{
		Playlist: playlist,
		Matched:  matched,
		Skipped:  skipped,
	})
}

// resolvePlaylistImportLine matches one M3U entry (an absolute path, or a
// path relative to a music folder root) to a known song.
func resolvePlaylistImportLine(db *sql.DB, folders []*database.MusicFolder, line string) *database.Song {
	for _, folder := range folders {
		rel := line
		if strings.HasPrefix(line, folder.Path) {
			rel = strings.TrimPrefix(line, folder.Path)
			rel = strings.TrimPrefix(rel, string(filepath.Separator))
		} else if filepath.IsAbs(line) {
			continue // absolute path under a different folder root: not a match here
		}
		mf, err := database.FindMediaFileByPath(db, folder.ID, rel)
		if err != nil {
			continue
		}
		song, err := database.GetSongByMediaFileID(db, mf.ID)
		if err != nil {
			continue
		}
		return song
	}
	return nil
}

func sanitizeFilename(name string) string {
	name = strings.Map(func(r rune) rune {
		switch r {
		case '/', '\\', ':', '*', '?', '"', '<', '>', '|':
			return '_'
		}
		return r
	}, name)
	name = strings.TrimSpace(name)
	if name == "" {
		return "playlist"
	}
	return name
}