package media

import (
	"bytes"
	"context"
	"database/sql"
	"encoding/binary"
	"errors"
	"fmt"
	"io"
	"net/http"
	"strconv"
	"time"

	"git.netflux.io/rob/clipper/config"
	"git.netflux.io/rob/clipper/generated/store"
	"github.com/google/uuid"
	"github.com/jackc/pgx/v4"
	youtubev2 "github.com/kkdai/youtube/v2"
	"go.uber.org/zap"
)

const (
	getVideoExpiresIn = time.Hour
	getAudioExpiresIn = time.Hour
)

const (
	rawAudioCodec      = "pcm_s16le"
	rawAudioFormat     = "s16le"
	rawAudioSampleRate = 48_000
	rawAudioMimeType   = "audio/raw"
)

const (
	thumbnailWidth  = 177 // 16:9
	thumbnailHeight = 100 // "
)

// MediaSetService exposes logical flows handling MediaSets.
type MediaSetService struct {
	store     Store
	youtube   YoutubeClient
	fileStore FileStore
	config    config.Config
	logger    *zap.SugaredLogger
}

func NewMediaSetService(store Store, youtubeClient YoutubeClient, fileStore FileStore, config config.Config, logger *zap.SugaredLogger) *MediaSetService {
	return &MediaSetService{
		store:     store,
		youtube:   youtubeClient,
		fileStore: fileStore,
		config:    config,
		logger:    logger,
	}
}

// Get fetches the metadata for a given MediaSet source. If it does not exist
// in the local DB, it will attempt to create it. After the resource has been
// created, other endpoints (e.g. GetAudio) can be called to fetch media from
// Youtube and store it in a file store.
func (s *MediaSetService) Get(ctx context.Context, youtubeID string) (*MediaSet, error) {
	var (
		mediaSet *MediaSet
		err      error
	)

	mediaSet, err = s.findMediaSet(ctx, youtubeID)
	if err != nil {
		return nil, fmt.Errorf("error finding existing media set: %v", err)
	}

	if mediaSet == nil {
		mediaSet, err = s.createMediaSet(ctx, youtubeID)
		if err != nil {
			return nil, fmt.Errorf("error creating new media set: %v", err)
		}
	}

	return mediaSet, nil
}

func (s *MediaSetService) createMediaSet(ctx context.Context, youtubeID string) (*MediaSet, error) {
	video, err := s.youtube.GetVideoContext(ctx, youtubeID)
	if err != nil {
		return nil, fmt.Errorf("error fetching video: %v", err)
	}

	if len(video.Formats) == 0 {
		return nil, errors.New("no format available")
	}

	audioMetadata, err := s.fetchAudioMetadata(ctx, video)
	if err != nil {
		return nil, fmt.Errorf("error fetching audio metadata: %v", err)
	}
	videoMetadata, err := s.fetchVideoMetadata(ctx, video)
	if err != nil {
		return nil, fmt.Errorf("error fetching video metadata: %v", err)
	}

	storeParams := store.CreateMediaSetParams{
		YoutubeID:            youtubeID,
		AudioYoutubeItag:     int32(audioMetadata.YoutubeItag),
		AudioChannels:        int32(audioMetadata.Channels),
		AudioFramesApprox:    audioMetadata.ApproxFrames,
		AudioSampleRate:      int32(audioMetadata.SampleRate),
		AudioEncodedMimeType: audioMetadata.MimeType,
		AudioContentLength:   audioMetadata.ContentLength,
		VideoYoutubeItag:     int32(videoMetadata.YoutubeItag),
		VideoContentLength:   videoMetadata.ContentLength,
		VideoMimeType:        videoMetadata.MimeType,
		VideoDurationNanos:   videoMetadata.Duration.Nanoseconds(),
	}
	mediaSet, err := s.store.CreateMediaSet(ctx, storeParams)
	if err != nil {
		return nil, fmt.Errorf("error creating media set in store: %v", err)
	}

	return &MediaSet{
		ID:        mediaSet.ID,
		YoutubeID: youtubeID,
		Audio:     audioMetadata,
		Video:     videoMetadata,
	}, nil
}

// findMediaSet fetches a record from the database, returning (nil, nil) if it does not exist.
func (s *MediaSetService) findMediaSet(ctx context.Context, youtubeID string) (*MediaSet, error) {
	mediaSet, err := s.store.GetMediaSetByYoutubeID(ctx, youtubeID)
	if err != nil {
		if err == pgx.ErrNoRows {
			return nil, nil
		}
		return nil, fmt.Errorf("error getting media set: %v", err)
	}

	return &MediaSet{
		ID:        mediaSet.ID,
		YoutubeID: mediaSet.YoutubeID,
		Audio: Audio{
			YoutubeItag:   int(mediaSet.AudioYoutubeItag),
			ContentLength: mediaSet.AudioContentLength,
			Channels:      int(mediaSet.AudioChannels),
			ApproxFrames:  int64(mediaSet.AudioFramesApprox),
			Frames:        mediaSet.AudioFrames.Int64,
			SampleRate:    int(mediaSet.AudioSampleRate),
			MimeType:      mediaSet.AudioEncodedMimeType,
		},
		Video: Video{
			YoutubeItag:     int(mediaSet.VideoYoutubeItag),
			ContentLength:   mediaSet.VideoContentLength,
			Duration:        time.Duration(mediaSet.VideoDurationNanos),
			MimeType:        mediaSet.VideoMimeType,
			ThumbnailWidth:  0, // ??
			ThumbnailHeight: 0, // ??
		},
	}, nil
}

func (s *MediaSetService) fetchVideoMetadata(ctx context.Context, video *youtubev2.Video) (Video, error) {
	formats := FilterYoutubeVideo(video.Formats)
	if len(video.Formats) == 0 {
		return Video{}, errors.New("no format available")
	}
	format := formats[0]

	durationMsecs, err := strconv.Atoi(format.ApproxDurationMs)
	if err != nil {
		return Video{}, fmt.Errorf("could not parse video duration: %s", err)
	}

	return Video{
		YoutubeItag:     format.ItagNo,
		MimeType:        format.MimeType,
		ContentLength:   format.ContentLength,
		ThumbnailWidth:  thumbnailWidth,
		ThumbnailHeight: thumbnailHeight,
		Duration:        time.Duration(durationMsecs) * time.Millisecond,
	}, nil
}

func (s *MediaSetService) fetchAudioMetadata(ctx context.Context, video *youtubev2.Video) (Audio, error) {
	formats := FilterYoutubeAudio(video.Formats)
	if len(video.Formats) == 0 {
		return Audio{}, errors.New("no format available")
	}
	format := formats[0]

	sampleRate, err := strconv.Atoi(format.AudioSampleRate)
	if err != nil {
		return Audio{}, fmt.Errorf("invalid samplerate: %s", format.AudioSampleRate)
	}

	approxDurationMsecs, err := strconv.Atoi(format.ApproxDurationMs)
	if err != nil {
		return Audio{}, fmt.Errorf("could not parse audio duration: %s", err)
	}
	approxDuration := time.Duration(approxDurationMsecs) * time.Millisecond
	approxFrames := int64(approxDuration/time.Second) * int64(sampleRate)

	return Audio{
		ContentLength: format.ContentLength,
		MimeType:      format.MimeType,
		YoutubeItag:   format.ItagNo,
		ApproxFrames:  approxFrames,
		Channels:      format.AudioChannels,
		SampleRate:    sampleRate,
	}, nil
}

// GetVideo fetches the video part of a MediaSet.
func (s *MediaSetService) GetVideo(ctx context.Context, id uuid.UUID) (GetVideoProgressReader, error) {
	mediaSet, err := s.store.GetMediaSet(ctx, id)
	if err != nil {
		return nil, fmt.Errorf("error getting media set: %v", err)
	}

	if mediaSet.VideoS3UploadedAt.Valid {
		url, err := s.fileStore.GetURL(ctx, mediaSet.VideoS3Key.String)
		if err != nil {
			return nil, fmt.Errorf("error generating presigned URL: %v", err)
		}
		videoGetter := videoGetterDownloaded(url)
		return &videoGetter, nil
	}

	video, err := s.youtube.GetVideoContext(ctx, mediaSet.YoutubeID)
	if err != nil {
		return nil, fmt.Errorf("error fetching video: %v", err)
	}

	format := video.Formats.FindByItag(int(mediaSet.VideoYoutubeItag))
	if format == nil {
		return nil, fmt.Errorf("error finding itag: %v", err)
	}

	stream, _, err := s.youtube.GetStreamContext(ctx, video, format)
	if err != nil {
		return nil, fmt.Errorf("error fetching stream: %v", err)
	}

	// TODO: use mediaSet func to fetch videoKey
	videoKey := fmt.Sprintf("media_sets/%s/video.mp4", mediaSet.ID)

	videoGetter := newVideoGetter(s.store, s.fileStore, s.logger)
	return videoGetter.GetVideo(
		ctx,
		stream,
		format.ContentLength,
		mediaSet.ID,
		videoKey,
		format.MimeType,
	)
}

// GetAudio fetches the audio part of a MediaSet.
func (s *MediaSetService) GetAudio(ctx context.Context, id uuid.UUID, numBins int) (GetAudioProgressReader, error) {
	mediaSet, err := s.store.GetMediaSet(ctx, id)
	if err != nil {
		return nil, fmt.Errorf("error getting media set: %v", err)
	}

	// We need both raw and encoded audio to have been uploaded successfully.
	// Otherwise, we cannot return both peaks and a presigned URL for use by the
	// player.
	if mediaSet.AudioRawS3UploadedAt.Valid && mediaSet.AudioEncodedS3UploadedAt.Valid {
		return s.getAudioFromFileStore(ctx, mediaSet, numBins)
	}

	return s.getAudioFromYoutube(ctx, mediaSet, numBins)
}

func (s *MediaSetService) getAudioFromYoutube(ctx context.Context, mediaSet store.MediaSet, numBins int) (GetAudioProgressReader, error) {
	audioGetter := newAudioGetter(s.store, s.youtube, s.fileStore, s.config, s.logger)
	return audioGetter.GetAudio(ctx, mediaSet, numBins)
}

func (s *MediaSetService) getAudioFromFileStore(ctx context.Context, mediaSet store.MediaSet, numBins int) (GetAudioProgressReader, error) {
	object, err := s.fileStore.GetObject(ctx, mediaSet.AudioRawS3Key.String)
	if err != nil {
		return nil, fmt.Errorf("error getting object from file store: %v", err)
	}

	getAudioProgressReader, err := newGetAudioProgressReader(
		int64(mediaSet.AudioFrames.Int64),
		int(mediaSet.AudioChannels),
		numBins,
	)
	if err != nil {
		return nil, fmt.Errorf("error creating audio reader: %v", err)
	}

	state := getAudioFromFileStoreState{
		getAudioProgressReader: getAudioProgressReader,
		reader:                 NewModuloBufReader(object, int(mediaSet.AudioChannels)*SizeOfInt16),
		fileStore:              s.fileStore,
		config:                 s.config,
		logger:                 s.logger,
	}
	go state.run(ctx, mediaSet)

	return &state, nil
}

type getAudioFromFileStoreState struct {
	*getAudioProgressReader

	reader    io.ReadCloser
	fileStore FileStore
	config    config.Config
	logger    *zap.SugaredLogger
}

func (s *getAudioFromFileStoreState) run(ctx context.Context, mediaSet store.MediaSet) {
	done := make(chan error)
	var err error

	go func() {
		_, copyErr := io.Copy(s, s.reader)
		done <- copyErr
	}()

outer:
	for {
		select {
		case <-ctx.Done():
			err = ctx.Err()
			break outer
		case err = <-done:
			break outer
		}
	}

	if readerErr := s.reader.Close(); readerErr != nil {
		if err == nil {
			err = readerErr
		}
	}

	if err != nil {
		s.logger.Errorf("getAudioFromFileStoreState: error closing reader: %v", err)
		s.CloseWithError(err)
		return
	}

	url, err := s.fileStore.GetURL(ctx, mediaSet.AudioEncodedS3Key.String)
	if err != nil {
		s.CloseWithError(fmt.Errorf("error generating object URL: %v", err))
	}

	if iterErr := s.Close(url); iterErr != nil {
		s.logger.Errorf("getAudioFromFileStoreState: error closing progress iterator: %v", iterErr)
	}
}

func (s *MediaSetService) GetAudioSegment(ctx context.Context, id uuid.UUID, startFrame, endFrame int64, numBins int) ([]int16, error) {
	if startFrame < 0 || endFrame < 0 || numBins <= 0 {
		s.logger.With("startFrame", startFrame, "endFrame", endFrame, "numBins", numBins).Error("invalid arguments")
		return nil, errors.New("invalid arguments")
	}

	mediaSet, err := s.store.GetMediaSet(ctx, id)
	if err != nil {
		return nil, fmt.Errorf("error getting media set: %v", err)
	}

	object, err := s.fileStore.GetObjectWithRange(
		ctx,
		mediaSet.AudioRawS3Key.String,
		startFrame*int64(mediaSet.AudioChannels)*SizeOfInt16,
		endFrame*int64(mediaSet.AudioChannels)*SizeOfInt16,
	)
	if err != nil {
		return nil, fmt.Errorf("error getting object from file store: %v", err)
	}
	defer object.Close()

	const readBufSizeBytes = 8_192
	channels := int(mediaSet.AudioChannels)
	modReader := NewModuloBufReader(object, channels*SizeOfInt16)
	readBuf := make([]byte, readBufSizeBytes)
	peaks := make([]int16, channels*numBins)
	totalFrames := endFrame - startFrame
	framesPerBin := totalFrames / int64(numBins)
	sampleBuf := make([]int16, readBufSizeBytes/SizeOfInt16)
	bytesExpected := (endFrame - startFrame) * int64(channels) * SizeOfInt16

	var (
		bytesRead     int64
		closing       bool
		currPeakIndex int
		currFrame     int64
	)

	for {
		n, err := modReader.Read(readBuf)
		if err == io.EOF {
			closing = true
		} else if err != nil {
			return nil, fmt.Errorf("read error: %v", err)
		}

		bytesRead += int64(n)
		samples := sampleBuf[:n/SizeOfInt16]

		if err := binary.Read(bytes.NewReader(readBuf[:n]), binary.LittleEndian, samples); err != nil {
			return nil, fmt.Errorf("error interpreting samples: %v", err)
		}

		for i := 0; i < len(samples); i += channels {
			for j := 0; j < channels; j++ {
				samp := sampleBuf[i+j]
				if samp < 0 {
					samp = -samp
				}
				if samp > peaks[currPeakIndex+j] {
					peaks[currPeakIndex+j] = samp
				}
			}

			if currFrame == framesPerBin {
				currFrame = 0
				currPeakIndex += channels
			} else {
				currFrame++
			}
		}

		if closing {
			break
		}
	}

	if bytesRead < bytesExpected {
		s.logger.With("startFrame", startFrame, "endFrame", endFrame, "got", bytesRead, "want", bytesExpected, "key", mediaSet.AudioRawS3Key.String).Warn("short read from file store")
	}

	return peaks, nil
}

func sqlString(s string) sql.NullString {
	return sql.NullString{String: s, Valid: true}
}

func sqlInt64(i int64) sql.NullInt64 {
	return sql.NullInt64{Int64: i, Valid: true}
}

func sqlInt32(i int32) sql.NullInt32 {
	return sql.NullInt32{Int32: i, Valid: true}
}

// ModuloBufReader reads from a reader in block sizes that are exactly modulo
// modSize, with any remainder buffered until the next read.
type ModuloBufReader struct {
	io.ReadCloser

	buf     bytes.Buffer
	modSize int
}

func NewModuloBufReader(r io.ReadCloser, modSize int) *ModuloBufReader {
	return &ModuloBufReader{ReadCloser: r, modSize: modSize}
}

func (r *ModuloBufReader) Read(p []byte) (int, error) {
	// err is always io.EOF or nil
	nr1, _ := r.buf.Read(p)
	nr2, err := r.ReadCloser.Read(p[nr1:])

	nr := nr1 + nr2
	rem := nr % r.modSize

	// if there was an error, return immediately.
	if err == io.EOF {
		return nr, err
	} else if err != nil {
		return nr - rem, err
	}

	// write any remainder to the buffer
	if rem != 0 {
		// err is always nil
		_, _ = r.buf.Write(p[nr-rem : nr])
	}

	return nr - rem, err
}

type VideoThumbnail struct {
	Data          []byte
	Width, Height int
}

func (s *MediaSetService) GetVideoThumbnail(ctx context.Context, id uuid.UUID) (VideoThumbnail, error) {
	mediaSet, err := s.store.GetMediaSet(ctx, id)
	if err != nil {
		return VideoThumbnail{}, fmt.Errorf("error getting media set: %v", err)
	}

	if mediaSet.VideoThumbnailS3UploadedAt.Valid {
		return s.getThumbnailFromFileStore(ctx, mediaSet)
	}

	return s.getThumbnailFromYoutube(ctx, mediaSet)
}

func (s *MediaSetService) getThumbnailFromFileStore(ctx context.Context, mediaSet store.MediaSet) (VideoThumbnail, error) {
	object, err := s.fileStore.GetObject(ctx, mediaSet.VideoThumbnailS3Key.String)
	if err != nil {
		return VideoThumbnail{}, fmt.Errorf("error fetching thumbnail from file store: %v", err)
	}
	defer object.Close()

	imageData, err := io.ReadAll(object)
	if err != nil {
		return VideoThumbnail{}, fmt.Errorf("error reading thumbnail from file store: %v", err)
	}

	return VideoThumbnail{
		Width:  int(mediaSet.VideoThumbnailWidth.Int32),
		Height: int(mediaSet.VideoThumbnailHeight.Int32),
		Data:   imageData,
	}, nil
}

func (s *MediaSetService) getThumbnailFromYoutube(ctx context.Context, mediaSet store.MediaSet) (VideoThumbnail, error) {
	video, err := s.youtube.GetVideoContext(ctx, mediaSet.YoutubeID)
	if err != nil {
		return VideoThumbnail{}, fmt.Errorf("error fetching video: %v", err)
	}

	if len(video.Formats) == 0 {
		return VideoThumbnail{}, errors.New("no format available")
	}

	thumbnails := video.Thumbnails
	SortYoutubeThumbnails(thumbnails)
	thumbnail := thumbnails[0]

	resp, err := http.Get(thumbnail.URL)
	if err != nil {
		return VideoThumbnail{}, fmt.Errorf("error fetching thumbnail: %v", err)
	}
	defer resp.Body.Close()

	imageData, err := io.ReadAll(resp.Body)
	if err != nil {
		return VideoThumbnail{}, fmt.Errorf("error reading thumbnail: %v", err)
	}

	// TODO: use mediaSet func to fetch key
	thumbnailKey := fmt.Sprintf("media_sets/%s/thumbnail.jpg", mediaSet.ID)

	const mimeType = "application/jpeg"
	_, err = s.fileStore.PutObject(ctx, thumbnailKey, bytes.NewReader(imageData), mimeType)
	if err != nil {
		return VideoThumbnail{}, fmt.Errorf("error uploading thumbnail: %v", err)
	}

	storeParams := store.SetVideoThumbnailUploadedParams{
		ID:                     mediaSet.ID,
		VideoThumbnailMimeType: sqlString(mimeType),
		VideoThumbnailS3Key:    sqlString(thumbnailKey),
		VideoThumbnailWidth:    sqlInt32(int32(thumbnail.Width)),
		VideoThumbnailHeight:   sqlInt32(int32(thumbnail.Height)),
	}
	if _, err := s.store.SetVideoThumbnailUploaded(ctx, storeParams); err != nil {
		return VideoThumbnail{}, fmt.Errorf("error updating media set: %v", err)
	}

	return VideoThumbnail{Width: int(thumbnail.Width), Height: int(thumbnail.Height), Data: imageData}, nil
}

// progressReader is a reader that prints progress logs as it reads.
type progressReader struct {
	io.Reader

	label      string
	total, exp int64
	logger     *zap.SugaredLogger
}

func newProgressReader(reader io.Reader, label string, exp int64, logger *zap.SugaredLogger) *progressReader {
	return &progressReader{
		Reader: reader,
		exp:    exp,
		logger: logger.Named(label),
	}
}

func (r *progressReader) Read(p []byte) (int, error) {
	n, err := r.Reader.Read(p)
	r.total += int64(n)

	r.logger.Debugf("Read %d of %d (%.02f%%) bytes from the provided reader", r.total, r.exp, (float32(r.total)/float32(r.exp))*100.0)

	return n, err
}