package media

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

	"git.netflux.io/rob/clipper/generated/store"
	"github.com/aws/aws-sdk-go-v2/aws"
	"github.com/aws/aws-sdk-go-v2/service/s3"
	"github.com/google/uuid"
	youtubev2 "github.com/kkdai/youtube/v2"
)

const s3Bucket = "clipper-development"

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

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

// progressReader is a reader that prints progress logs as it reads.
type progressReader struct {
	io.Reader
	label      string
	total, exp int
}

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

	log.Printf("[ProgressReader] [%s] Read %d of %d (%.02f%%) bytes from the provided reader", pw.label, pw.total, pw.exp, (float32(pw.total)/float32(pw.exp))*100.0)

	return n, err
}

// Store wraps a database store.
type Store interface {
	GetMediaSet(ctx context.Context, id uuid.UUID) (store.MediaSet, error)
	GetMediaSetByYoutubeID(ctx context.Context, youtubeID string) (store.MediaSet, error)
	CreateMediaSet(ctx context.Context, arg store.CreateMediaSetParams) (store.MediaSet, error)
	SetAudioUploaded(ctx context.Context, arg store.SetAudioUploadedParams) (store.MediaSet, error)
}

// S3Client wraps the AWS S3 service client.
type S3Client interface {
	GetObject(context.Context, *s3.GetObjectInput, ...func(*s3.Options)) (*s3.GetObjectOutput, error)
	CreateMultipartUpload(context.Context, *s3.CreateMultipartUploadInput, ...func(*s3.Options)) (*s3.CreateMultipartUploadOutput, error)
	UploadPart(context.Context, *s3.UploadPartInput, ...func(*s3.Options)) (*s3.UploadPartOutput, error)
	AbortMultipartUpload(ctx context.Context, params *s3.AbortMultipartUploadInput, optFns ...func(*s3.Options)) (*s3.AbortMultipartUploadOutput, error)
	CompleteMultipartUpload(context.Context, *s3.CompleteMultipartUploadInput, ...func(*s3.Options)) (*s3.CompleteMultipartUploadOutput, error)
}

// YoutubeClient wraps the youtube.Client client.
type YoutubeClient interface {
	GetVideoContext(context.Context, string) (*youtubev2.Video, error)
	GetStreamContext(context.Context, *youtubev2.Video, *youtubev2.Format) (io.ReadCloser, int64, error)
}

// MediaSetService exposes logical flows handling MediaSets.
type MediaSetService struct {
	store   Store
	youtube YoutubeClient
	s3      S3Client
}

func NewMediaSetService(store Store, youtubeClient YoutubeClient, s3Client S3Client) *MediaSetService {
	return &MediaSetService{
		store:   store,
		youtube: youtubeClient,
		s3:      s3Client,
	}
}

// Get fetches the metadata for a given MediaSet source.
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 getting existing media set: %v", err)
	}

	if mediaSet == nil {
		mediaSet, err = s.createMediaSet(ctx, youtubeID)
		if err != nil {
			return nil, fmt.Errorf("error getting 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)
	}

	params := store.CreateMediaSetParams{
		YoutubeID:            youtubeID,
		AudioYoutubeItag:     int32(audioMetadata.YoutubeItag),
		AudioChannels:        int32(audioMetadata.Channels),
		AudioFramesApprox:    audioMetadata.ApproxFrames,
		AudioSampleRate:      int32(audioMetadata.SampleRate),
		AudioMimeTypeEncoded: audioMetadata.MimeType,
		VideoYoutubeItag:     int32(videoMetadata.YoutubeItag),
		VideoMimeType:        videoMetadata.MimeType,
		VideoDurationNanos:   videoMetadata.Duration.Nanoseconds(),
	}
	mediaSet, err := s.store.CreateMediaSet(ctx, params)
	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 == sql.ErrNoRows {
			return nil, nil
		}
		return nil, fmt.Errorf("error getting existing media set: %v", err)
	}

	return &MediaSet{
		ID:        mediaSet.ID,
		YoutubeID: mediaSet.YoutubeID,
		Audio: Audio{
			YoutubeItag:  int(mediaSet.AudioYoutubeItag),
			Bytes:        0, // DEPRECATED
			Channels:     int(mediaSet.AudioChannels),
			ApproxFrames: int64(mediaSet.AudioFramesApprox),
			Frames:       mediaSet.AudioFrames.Int64,
			SampleRate:   int(mediaSet.AudioSampleRate),
			MimeType:     mediaSet.AudioMimeTypeEncoded,
		},
		Video: Video{
			YoutubeItag:     int(mediaSet.VideoYoutubeItag),
			Bytes:           0, // DEPRECATED?
			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,
		Bytes:           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{
		MimeType:     format.MimeType,
		YoutubeItag:  format.ItagNo,
		ApproxFrames: approxFrames,
		Channels:     format.AudioChannels,
		SampleRate:   sampleRate,
	}, nil
}

// 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)
	}

	if mediaSet.AudioS3UploadedAt.Valid {
		return s.getAudioFromS3(ctx, mediaSet, numBins)
	}

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

func (s *MediaSetService) getAudioFromS3(ctx context.Context, mediaSet store.MediaSet, numBins int) (GetAudioProgressReader, error) {
	input := s3.GetObjectInput{
		Bucket: aws.String(mediaSet.AudioS3Bucket.String),
		Key:    aws.String(mediaSet.AudioS3Key.String),
	}
	output, err := s.s3.GetObject(ctx, &input)
	if err != nil {
		return nil, fmt.Errorf("error getting object from s3: %v", err)
	}

	fetchAudioProgressReader := newGetAudioProgressReader(
		binary.BigEndian,
		int64(mediaSet.AudioFrames.Int64),
		int(mediaSet.AudioChannels),
		numBins,
	)

	state := getAudioFromS3State{
		fetchAudioProgressReader: fetchAudioProgressReader,
		s3Reader:                 NewModuloBufReader(output.Body, int(mediaSet.AudioChannels)*SizeOfInt16),
	}
	go state.run(ctx)

	return &state, nil
}

type getAudioFromS3State struct {
	*fetchAudioProgressReader

	s3Reader io.ReadCloser
}

func (s *getAudioFromS3State) run(ctx context.Context) {
	done := make(chan error)
	var err error

	go func() {
		_, copyErr := io.Copy(s, s.s3Reader)
		done <- copyErr
	}()

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

	if readerErr := s.s3Reader.Close(); readerErr != nil {
		if err == nil {
			err = readerErr
		}
	}

	if err != nil {
		log.Printf("error closing s3Reader: %v", err)
		s.Abort(err)
		return
	}

	if iterErr := s.Close(); iterErr != nil {
		log.Printf("error closing progress iterator: %v", iterErr)
	}
}

func (s *MediaSetService) getAudioFromYoutube(ctx context.Context, mediaSet store.MediaSet, numBins int) (GetAudioProgressReader, error) {
	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.AudioYoutubeItag))
	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)
	}

	// wrap it in a progress reader
	progressStream := &progressReader{Reader: stream, label: "audio", exp: int(format.ContentLength)}

	ffmpegReader, err := newFfmpegReader(ctx, progressStream, "-i", "-", "-f", rawAudioFormat, "-ar", strconv.Itoa(rawAudioSampleRate), "-acodec", rawAudioCodec, "-")
	if err != nil {
		return nil, fmt.Errorf("error creating ffmpegreader: %v", err)
	}

	s3Key := fmt.Sprintf("media_sets/%s/audio.raw", mediaSet.ID)
	uploader := newMultipartUploader(s.s3)

	fetchAudioProgressReader := newGetAudioProgressReader(
		binary.LittleEndian,
		int64(mediaSet.AudioFramesApprox),
		format.AudioChannels,
		numBins,
	)

	state := getAudioFromYoutubeState{
		fetchAudioProgressReader: fetchAudioProgressReader,
		ffmpegReader:             ffmpegReader,
		uploader:                 uploader,
		s3Bucket:                 s3Bucket,
		s3Key:                    s3Key,
		store:                    s.store,
	}
	go state.run(ctx, mediaSet.ID)

	return &state, nil
}

type getAudioFromYoutubeState struct {
	*fetchAudioProgressReader

	ffmpegReader    *ffmpegReader
	uploader        *multipartUploader
	s3Bucket, s3Key string
	store           Store
}

func (s *getAudioFromYoutubeState) run(ctx context.Context, mediaSetID uuid.UUID) {
	teeReader := io.TeeReader(s.ffmpegReader, s)
	bytesUploaded, err := s.uploader.Upload(ctx, teeReader, s.s3Bucket, s.s3Key, rawAudioMimeType)

	// If there was an error returned, the underlying ffmpegReader process may
	// still be active. Kill it.
	if err != nil {
		if cancelErr := s.ffmpegReader.Cancel(); cancelErr != nil {
			log.Printf("error cancelling ffmpegreader: %v", cancelErr)
		}
	}

	// Either way, we need to wait for the ffmpegReader process to exit,
	// and ensure there is no error.
	if readerErr := s.ffmpegReader.Close(); readerErr != nil {
		if err == nil {
			err = readerErr
		}
	}

	if err == nil {
		_, updateErr := s.store.SetAudioUploaded(ctx, store.SetAudioUploadedParams{
			ID:            mediaSetID,
			AudioS3Bucket: sqlString(s.s3Bucket),
			AudioS3Key:    sqlString(s.s3Key),
			AudioFrames:   sqlInt64(bytesUploaded),
		})

		if updateErr != nil {
			err = updateErr
		}
	}

	if err != nil {
		log.Printf("error uploading asynchronously: %v", err)

		s.Abort(err)
		return
	}

	if iterErr := s.Close(); iterErr != nil {
		log.Printf("error closing progress iterator: %v", iterErr)
	}
}

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}
}

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 rem != 0 {
		// err is always nil
		_, _ = r.buf.Write(p[nr-rem:])
	}

	return nr - rem, err
}