clipper/backend/server/server.go

package server

import (
	"context"
	"io"
	"log"
	"net/http"
	"os"
	"time"

	pbMediaSet "git.netflux.io/rob/clipper/generated/pb/media_set"
	"git.netflux.io/rob/clipper/media"
	"git.netflux.io/rob/clipper/youtube"
	"github.com/improbable-eng/grpc-web/go/grpcweb"
	"google.golang.org/grpc"
	"google.golang.org/grpc/grpclog"
	"google.golang.org/protobuf/types/known/durationpb"
)

type Options struct {
	BindAddr      string
	Timeout       time.Duration
	YoutubeClient youtube.YoutubeClient
	S3Client      media.S3Client
}

const (
	fetchAudioTimeout = time.Minute * 5
)

// fetchMediaSetServiceController implements gRPC controller for FetchMediaSetService
type fetchMediaSetServiceController struct {
	pbMediaSet.UnimplementedFetchServiceServer

	fetchMediaSetService *media.FetchMediaSetService
}

// Fetch fetches a pbMediaSet.MediaSet
func (c *fetchMediaSetServiceController) Fetch(ctx context.Context, request *pbMediaSet.FetchRequest) (*pbMediaSet.MediaSet, error) {
	mediaSet, err := c.fetchMediaSetService.Fetch(ctx, request.GetId())
	if err != nil {
		return nil, err
	}

	result := pbMediaSet.MediaSet{
		Id: mediaSet.ID,
		Audio: &pbMediaSet.MediaSet_Audio{
			Bytes:      mediaSet.Audio.Bytes,
			Channels:   int32(mediaSet.Audio.Channels),
			Frames:     mediaSet.Audio.Frames,
			SampleRate: int32(mediaSet.Audio.SampleRate),
		},
		Video: &pbMediaSet.MediaSet_Video{
			Bytes:           mediaSet.Video.Bytes,
			Duration:        durationpb.New(mediaSet.Video.Duration),
			ThumbnailWidth:  int32(mediaSet.Video.ThumbnailWidth),
			ThumbnailHeight: int32(mediaSet.Video.ThumbnailHeight),
		},
	}

	return &result, nil
}

// TODO: wrap errors
func (c *fetchMediaSetServiceController) FetchAudio(request *pbMediaSet.FetchAudioRequest, stream pbMediaSet.FetchService_FetchAudioServer) error {
	ctx, cancel := context.WithTimeout(context.Background(), fetchAudioTimeout)
	defer cancel()

	reader, err := c.fetchMediaSetService.FetchAudio(ctx, request.GetId(), int(request.GetNumBins()))
	if err != nil {
		return err
	}

	for {
		progress, err := reader.Read()
		if err != nil {
			if err == io.EOF {
				break
			}
			return err
		}

		// TODO: consider using int32 throughout the backend flow to avoid this.
		peaks := make([]int32, len(progress.Peaks))
		for i, p := range progress.Peaks {
			peaks[i] = int32(p)
		}

		progressPb := pbMediaSet.FetchAudioProgress{
			PercentCompleted: progress.PercentComplete,
			Peaks:            peaks,
		}

		stream.Send(&progressPb)
	}

	return nil
}

func Start(options Options) error {
	grpcServer := grpc.NewServer()

	fetchMediaSetService := media.NewFetchMediaSetService(options.YoutubeClient, options.S3Client)

	pbMediaSet.RegisterFetchServiceServer(grpcServer, &fetchMediaSetServiceController{fetchMediaSetService: fetchMediaSetService})
	grpclog.SetLogger(log.New(os.Stdout, "server: ", log.LstdFlags))

	// TODO: proper CORS support
	grpcWebServer := grpcweb.WrapServer(grpcServer, grpcweb.WithOriginFunc(func(string) bool { return true }))
	handler := func(w http.ResponseWriter, r *http.Request) {
		grpcWebServer.ServeHTTP(w, r)
	}

	httpServer := http.Server{
		Addr:         options.BindAddr,
		ReadTimeout:  options.Timeout,
		WriteTimeout: options.Timeout,
		Handler:      http.HandlerFunc(handler),
	}

	return httpServer.ListenAndServe()
}