clipper/backend/server/server.go

package server

import (
	"context"
	"fmt"
	"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/google/uuid"
	"github.com/improbable-eng/grpc-web/go/grpcweb"
	"google.golang.org/grpc"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/grpclog"
	"google.golang.org/protobuf/types/known/durationpb"
)

type ResponseError struct {
	error

	ResponseCode codes.Code
}

func (r *ResponseError) Error() string {
	return fmt.Sprintf("An unexpected error occurred: %v (error code = %d).", r.error.Error(), r.ResponseCode)
}

func (r *ResponseError) Unwrap() error {
	return r.error
}

func newResponseError(err error, code codes.Code) *ResponseError {
	return &ResponseError{error: err, ResponseCode: code}
}

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

const (
	getAudioTimeout = time.Minute * 5
)

// mediaSetServiceController implements gRPC controller for MediaSetService
type mediaSetServiceController struct {
	pbMediaSet.UnimplementedMediaSetServiceServer

	mediaSetService *media.MediaSetService
}

// Get returns a pbMediaSet.MediaSet
func (c *mediaSetServiceController) Get(ctx context.Context, request *pbMediaSet.GetRequest) (*pbMediaSet.MediaSet, error) {
	mediaSet, err := c.mediaSetService.Get(ctx, request.GetYoutubeId())
	if err != nil {
		return nil, newResponseError(err, codes.Unknown)
	}

	result := pbMediaSet.MediaSet{
		Id: mediaSet.YoutubeID,
		Audio: &pbMediaSet.MediaSet_Audio{
			Channels:     int32(mediaSet.Audio.Channels),
			Frames:       mediaSet.Audio.Frames,
			ApproxFrames: mediaSet.Audio.ApproxFrames,
			SampleRate:   int32(mediaSet.Audio.SampleRate),
			YoutubeItag:  int32(mediaSet.Audio.YoutubeItag),
			MimeType:     mediaSet.Audio.MimeType,
		},
		Video: &pbMediaSet.MediaSet_Video{
			Duration:    durationpb.New(mediaSet.Video.Duration),
			YoutubeItag: int32(mediaSet.Video.YoutubeItag),
			MimeType:    mediaSet.Video.MimeType,
		},
	}

	return &result, nil
}

// GetAudio streams the progress report of GetAudio.
func (c *mediaSetServiceController) GetAudio(request *pbMediaSet.GetAudioRequest, stream pbMediaSet.MediaSetService_GetAudioServer) error {
	ctx, cancel := context.WithTimeout(context.Background(), getAudioTimeout)
	defer cancel()

	id, err := uuid.Parse(request.GetId())
	if err != nil {
		return newResponseError(err, codes.Unknown)
	}

	reader, err := c.mediaSetService.GetAudio(ctx, id, int(request.GetNumBins()))
	if err != nil {
		return newResponseError(err, codes.Unknown)
	}

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

		// 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.GetAudioProgress{
			PercentCompleted: progress.PercentComplete,
			Peaks:            peaks,
		}

		stream.Send(&progressPb)
	}

	return nil
}

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

	fetchMediaSetService := media.NewMediaSetService(options.Store, options.YoutubeClient, options.S3Client)

	pbMediaSet.RegisterMediaSetServiceServer(grpcServer, &mediaSetServiceController{mediaSetService: 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()
}