package subsonic

import (
	"context"
	"net/http"
	"net/url"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"time"

	"git.noroutes.net/NoRoutes/vibetunes/internal/database"
	"git.noroutes.net/NoRoutes/vibetunes/internal/metadata"
	"git.noroutes.net/NoRoutes/vibetunes/internal/streaming"
	"git.noroutes.net/NoRoutes/vibetunes/internal/transcoding"
)

func init() {
	register("stream", handleStream)
	register("download", handleDownload)
	register("getCoverArt", handleGetCoverArt)
	register("getLyrics", handleGetLyrics)
	register("getAvatar", handleGetAvatar)
	register("hls", handleHLS)
	register("getCaptions", handleGetCaptions)
}

// resolveSongFile loads a song's media file and folder, checking the
// requesting user's folder permission. Every media-retrieval endpoint
// goes through this so the authorization check can never be forgotten
// in one of them.
func resolveSongFile(rc *Context, songID string) (mf *database.MediaFile, folder *database.MusicFolder, aerr *apiError) {
	db := rc.Server.DB
	song, err := database.GetSong(db, songID)
	if err != nil {
		return nil, nil, errNotFound("Song")
	}
	mf, err = database.GetMediaFile(db, song.MediaFileID)
	if err != nil {
		return nil, nil, errNotFound("Song")
	}
	if canSee, cerr := UserCanSeeMediaFile(db, rc.User, mf); cerr != nil {
		return nil, nil, newError(ErrGeneric, cerr.Error())
	} else if !canSee {
		return nil, nil, errUnauthorized("this song")
	}
	folder, err = database.GetMusicFolder(db, mf.MusicFolderID)
	if err != nil {
		return nil, nil, newError(ErrGeneric, err.Error())
	}
	return mf, folder, nil
}

func handleStream(rc *Context) *apiError {
	if !rc.User.Allows(rc.User.Permissions.Stream) {
		return errUnauthorized("streaming")
	}
	id, aerr := rc.Params.Required("id")
	if aerr != nil {
		return aerr
	}
	mf, folder, aerr := resolveSongFile(rc, id)
	if aerr != nil {
		return aerr
	}
	absPath, perr := streaming.ResolvePath(folder.Path, mf.RelativePath)
	if perr != nil {
		return newError(ErrGeneric, perr.Error())
	}

	formatParam := rc.Params.Get("format")
	maxBitRate := rc.Params.Int("maxBitRate", 0)
	timeOffset := rc.Params.Int("timeOffset", 0)

	rc.Handled = true

	// format=raw explicitly forces the original bytes. Otherwise,
	// transcode only if the client actually asked for something the
	// source doesn't already satisfy: a specific format, or a bitrate
	// cap below the source's own bitrate.
	needsTranscode := formatParam != "" && formatParam != "raw"
	if maxBitRate > 0 && (mf.BitrateKbps == 0 || maxBitRate < mf.BitrateKbps) {
		needsTranscode = true
	}
	if !needsTranscode {
		if err := streaming.ServeFile(rc.W, rc.R, absPath, mf.RelativePath); err != nil {
			http.Error(rc.W, "could not read media file", http.StatusInternalServerError)
		}
		return nil
	}

	format := transcoding.ParseFormat(formatParam)
	rc.W.Header().Set("Content-Type", format.MimeType())
	ctx := rc.R.Context()
	if err := rc.Server.Transcoder.Stream(ctx, rc.W, absPath, transcoding.Options{
		Format: format, MaxBitRateKbps: maxBitRate, TimeOffset: float64(timeOffset),
	}); err != nil && ctx.Err() == nil {
		rc.Server.Log.Warn("transcode failed", "err", err, "path", absPath)
	}
	return nil
}

func handleDownload(rc *Context) *apiError {
	if !rc.User.Allows(rc.User.Permissions.Download) {
		return errUnauthorized("downloading")
	}
	id, aerr := rc.Params.Required("id")
	if aerr != nil {
		return aerr
	}
	mf, folder, aerr := resolveSongFile(rc, id)
	if aerr != nil {
		return aerr
	}
	absPath, perr := streaming.ResolvePath(folder.Path, mf.RelativePath)
	if perr != nil {
		return newError(ErrGeneric, perr.Error())
	}

	rc.Handled = true
	filename := filepath.Base(mf.RelativePath)
	rc.W.Header().Set("Content-Disposition", `attachment; filename="`+strings.ReplaceAll(filename, `"`, "")+`"`)
	if err := streaming.ServeFile(rc.W, rc.R, absPath, filename); err != nil {
		http.Error(rc.W, "could not read media file", http.StatusInternalServerError)
	}
	return nil
}

func handleGetCoverArt(rc *Context) *apiError {
	if !rc.User.Allows(rc.User.Permissions.CoverArt) {
		return errUnauthorized("cover art")
	}
	id, aerr := rc.Params.Required("id")
	if aerr != nil {
		return aerr
	}
	size := rc.Params.Int("size", 0)
	db := rc.Server.DB

	art, err := database.GetCoverArt(db, id)
	if err != nil {
		return errNotFound("Cover art")
	}

	var sourcePath, contentHash string
	var isTemp bool
	if art.Source == "folder" {
		sourcePath, contentHash = art.SourcePath, art.ContentHash
	} else {
		mf, merr := database.GetMediaFile(db, art.MediaFileID.String)
		if merr != nil {
			return errNotFound("Cover art")
		}
		folder, ferr := database.GetMusicFolder(db, mf.MusicFolderID)
		if ferr != nil {
			return newError(ErrGeneric, ferr.Error())
		}
		absPath, perr := streaming.ResolvePath(folder.Path, mf.RelativePath)
		if perr != nil {
			return newError(ErrGeneric, perr.Error())
		}
		prober := &metadata.Prober{FFprobePath: rc.Server.Config.FFprobePath}
		ctx, cancel := contextWithTimeout(rc.R.Context())
		defer cancel()
		tags, terr := prober.Probe(ctx, absPath)
		if terr != nil || !tags.HasEmbeddedArt {
			return errNotFound("Cover art")
		}
		extracted, eerr := rc.Server.CoverArt.ExtractEmbedded(ctx, absPath, tags.EmbeddedArtStream)
		if eerr != nil {
			return newError(ErrGeneric, eerr.Error())
		}
		sourcePath, contentHash, isTemp = extracted, art.ContentHash, true
	}
	if isTemp {
		defer os.Remove(sourcePath)
	}

	cachedPath, gerr := rc.Server.CoverArt.GetOrCreate(sourcePath, contentHash, size)
	if gerr != nil {
		return newError(ErrGeneric, gerr.Error())
	}

	rc.Handled = true
	rc.W.Header().Set("Cache-Control", "public, max-age=604800, immutable")
	if err := streaming.ServeFile(rc.W, rc.R, cachedPath, "cover.jpg"); err != nil {
		http.Error(rc.W, "could not read cover art", http.StatusInternalServerError)
	}
	return nil
}

func contextWithTimeout(parent context.Context) (context.Context, context.CancelFunc) {
	return context.WithTimeout(parent, 15*time.Second)
}

func handleGetLyrics(rc *Context) *apiError {
	title := rc.Params.Get("title")
	artist := rc.Params.Get("artist")
	out := &Lyrics{Artist: artist, Title: title}

	if title != "" {
		db := rc.Server.DB
		if song, err := database.FindSongByTitleArtist(db, title, artist); err == nil {
			if text, found, _ := database.SongLyricsPlainText(db, song.ID); found {
				out.Value = text
			}
		}
	}

	rc.Response = newResponse()
	rc.Response.Lyrics = out
	return nil
}

// handleGetAvatar: VibeSonic has no user-avatar feature (Phase 1/2
// scope), so honestly reports "not found" rather than fabricating an
// image.
func handleGetAvatar(rc *Context) *apiError {
	if _, aerr := rc.Params.Required("username"); aerr != nil {
		return aerr
	}
	return errNotFound("Avatar")
}

func handleHLS(rc *Context) *apiError {
	if !rc.User.Allows(rc.User.Permissions.Stream) {
		return errUnauthorized("streaming")
	}
	id, aerr := rc.Params.Required("id")
	if aerr != nil {
		return aerr
	}
	mf, folder, aerr := resolveSongFile(rc, id)
	if aerr != nil {
		return aerr
	}
	absPath, perr := streaming.ResolvePath(folder.Path, mf.RelativePath)
	if perr != nil {
		return newError(ErrGeneric, perr.Error())
	}

	bitRate := rc.Params.Int("bitRate", 0)
	opts := transcoding.Options{Format: transcoding.FormatAAC, MaxBitRateKbps: bitRate}

	if segStr := rc.Params.Get("segment"); segStr != "" {
		segIndex, serr := strconv.Atoi(segStr)
		if serr != nil {
			return newError(ErrGeneric, "invalid segment")
		}
		session, herr := rc.Server.Transcoder.BuildHLS(rc.R.Context(), absPath, rc.Server.hlsCacheDir(), opts)
		if herr != nil {
			return newError(ErrGeneric, herr.Error())
		}
		path := session.SegmentPath(segIndex)
		if path == "" {
			return errNotFound("HLS segment")
		}
		rc.Handled = true
		rc.W.Header().Set("Content-Type", "video/mp2t")
		if err := streaming.ServeFile(rc.W, rc.R, path, "segment.ts"); err != nil {
			http.Error(rc.W, "could not read segment", http.StatusInternalServerError)
		}
		return nil
	}

	session, herr := rc.Server.Transcoder.BuildHLS(rc.R.Context(), absPath, rc.Server.hlsCacheDir(), opts)
	if herr != nil {
		return newError(ErrGeneric, herr.Error())
	}

	authQuery := authQueryString(rc)
	playlist := session.Playlist(func(i int) string {
		return "hls.view?id=" + url.QueryEscape(id) + "&segment=" + strconv.Itoa(i) +
			bitRateQuerySuffix(bitRate) + "&" + authQuery
	})

	rc.Handled = true
	rc.W.Header().Set("Content-Type", "application/vnd.apple.mpegurl")
	_, _ = rc.W.Write([]byte(playlist))
	return nil
}

func bitRateQuerySuffix(bitRate int) string {
	if bitRate <= 0 {
		return ""
	}
	return "&bitRate=" + strconv.Itoa(bitRate)
}

// authQueryString re-embeds the caller's own authentication parameters
// into generated segment URLs, so a bare HLS player (which won't know
// Subsonic's auth scheme) can fetch subsequent segments the same way it
// fetched the playlist.
func authQueryString(rc *Context) string {
	var parts []string
	for _, name := range []string{"u", "p", "t", "s", "v", "c"} {
		if v := rc.Params.Get(name); v != "" {
			parts = append(parts, name+"="+url.QueryEscape(v))
		}
	}
	return strings.Join(parts, "&")
}

func (s *Server) hlsCacheDir() string {
	return filepath.Join(s.Config.DataDir, "cache", "hls")
}

func handleGetCaptions(rc *Context) *apiError {
	id, aerr := rc.Params.Required("id")
	if aerr != nil {
		return aerr
	}
	parts := strings.SplitN(id, ":cap:", 2)
	if len(parts) != 2 {
		return errNotFound("Captions")
	}
	songID, indexStr := parts[0], parts[1]
	index, ierr := strconv.Atoi(indexStr)
	if ierr != nil {
		return errNotFound("Captions")
	}

	mf, folder, aerr := resolveSongFile(rc, songID)
	if aerr != nil {
		return aerr
	}
	absPath, perr := streaming.ResolvePath(folder.Path, mf.RelativePath)
	if perr != nil {
		return newError(ErrGeneric, perr.Error())
	}
	captions := findSidecarCaptions(absPath)
	if index < 0 || index >= len(captions) {
		return errNotFound("Captions")
	}

	rc.Handled = true
	if err := streaming.ServeFile(rc.W, rc.R, captions[index], filepath.Base(captions[index])); err != nil {
		http.Error(rc.W, "could not read captions", http.StatusInternalServerError)
	}
	return nil
}