package media

import (
	"context"
	"fmt"
	"io"

	"git.netflux.io/rob/clipper/generated/store"
	"github.com/google/uuid"
	"go.uber.org/zap"
)

type GetVideoProgress struct {
	PercentComplete float32
	URL             string
}

type GetVideoProgressReader interface {
	// Next returns the next video progress status. When the stream has finished,
	// a valid GetVideoProgress value will be returned with io.EOF.
	Next() (GetVideoProgress, error)
}

type videoGetter struct {
	store     Store
	fileStore FileStore
	logger    *zap.SugaredLogger
}

type videoGetterState struct {
	*videoGetter

	r                io.Reader
	count, exp       int64
	mediaSetID       uuid.UUID
	key, contentType string
	url              string
	progressChan     chan GetVideoProgress
	errorChan        chan error
}

func newVideoGetter(store Store, fileStore FileStore, logger *zap.SugaredLogger) *videoGetter {
	return &videoGetter{store: store, fileStore: fileStore, logger: logger}
}

// GetVideo gets video from Youtube and uploads it to a filestore using the
// specified key and content type. The returned reader must have its Next()
// method called until error = io.EOF, otherwise a deadlock or other resource
// leakage is likely.
func (g *videoGetter) GetVideo(ctx context.Context, r io.Reader, exp int64, mediaSetID uuid.UUID, key, contentType string) (GetVideoProgressReader, error) {
	s := &videoGetterState{
		videoGetter:  g,
		r:            newProgressReader(r, "video", exp, g.logger),
		exp:          exp,
		mediaSetID:   mediaSetID,
		key:          key,
		contentType:  contentType,
		progressChan: make(chan GetVideoProgress),
		errorChan:    make(chan error, 1),
	}

	go s.getVideo(ctx)

	// return s, exposing only the limited interface to the caller.
	return s, nil
}

// Write implements io.Writer. It is copied that same data that is written to
// the file store, to implement progress tracking.
func (s *videoGetterState) Write(p []byte) (int, error) {
	s.count += int64(len(p))
	pc := (float32(s.count) / float32(s.exp)) * 100
	s.progressChan <- GetVideoProgress{PercentComplete: pc}
	return len(p), nil
}

func (s *videoGetterState) getVideo(ctx context.Context) {
	teeReader := io.TeeReader(s.r, s)

	_, err := s.fileStore.PutObject(ctx, s.key, teeReader, s.contentType)
	if err != nil {
		s.errorChan <- fmt.Errorf("error uploading to file store: %v", err)
		return
	}

	s.url, err = s.fileStore.GetURL(ctx, s.key)
	if err != nil {
		s.errorChan <- fmt.Errorf("error getting object URL: %v", err)
	}

	storeParams := store.SetVideoUploadedParams{
		ID:         s.mediaSetID,
		VideoS3Key: sqlString(s.key),
	}
	_, err = s.store.SetVideoUploaded(ctx, storeParams)
	if err != nil {
		s.errorChan <- fmt.Errorf("error saving to store: %v", err)
	}

	close(s.progressChan)
}

// Next implements GetVideoProgressReader.
func (s *videoGetterState) Next() (GetVideoProgress, error) {
	for {
		select {
		case progress, ok := <-s.progressChan:
			if !ok {
				return GetVideoProgress{PercentComplete: 100, URL: s.url}, io.EOF
			}
			return progress, nil
		case err := <-s.errorChan:
			return GetVideoProgress{}, fmt.Errorf("error waiting for progress: %v", err)
		}
	}
}

type videoGetterDownloaded string

// Next() implements GetVideoProgressReader.
func (s *videoGetterDownloaded) Next() (GetVideoProgress, error) {
	return GetVideoProgress{
		PercentComplete: 100,
		URL:             string(*s),
	}, io.EOF
}