codename-sendaround/sendaround_client.go

package sendaround

import (
	"encoding/json"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"net/url"
	"strings"

	"github.com/icedream/sendaround/internal"
	"github.com/pion/webrtc/v2"
)

const sendaroundDataChannelLabel = "sendaround"

var defaultServerUrl = &url.URL{
	Scheme: "http",
	Host:   "localhost:8080",
	Path:   "/",
}

// SendaroundClient is the interface describing all client functionality to send
// or receive file transmissions via the Sendaround service.
type SendaroundClient interface {
	// Offer sets up a WebRTC connection to upload files to another peer.
	// A token is generated by the handshake server along with a URL that can be
	// used in the web browser to transfer files without any dedicated software.
	// Both values will be available in the returned Uploader instance.
	Offer() (conn *Uploader, err error)

	// Receive sets up a WebRTC connection to download files from a peer.
	// The token is communicated to the handshake server so that associated
	// connection data can be exchanged. Afterwards, a peer-to-peer connection
	// is started and data transmission can occur by requesting files through
	// the returned Downloader instance.
	Receive(token string) (conn *Downloader, err error)
}

type sendaroundClient struct {
	serverURL           *url.URL
	httpClient          *http.Client
	webrtcConfiguration webrtc.Configuration
	webrtc              *webrtc.API
}

// SendaroundClientConfiguration is a data struct containing configuration
// parameters for the creation of a SendaroundClient instance.
type SendaroundClientConfiguration struct {
	// ServerUrl is the URL of the Sendaround handshake server. Defaults to the main service URL.
	ServerURL *url.URL

	// WebrtcConfiguration defines specific configuration for WebRTC communication. Defaults to a configuration which uses Google STUN/ICE servers.
	WebRTCConfiguration *webrtc.Configuration

	// HttpClient can be set to a specific HTTP client instance to use for handshake server communication. Defaults to the Golang default HTTP client.
	HTTPClient *http.Client
}

// NewSendaroundClient creates a new instance of the SendaroundClient implementation to send or receive file transmissions via the Sendaround service.
func NewSendaroundClient(cfg *SendaroundClientConfiguration) SendaroundClient {
	serverURL := cfg.ServerURL
	if serverURL == nil {
		serverURL = defaultServerUrl
	}

	httpClient := cfg.HTTPClient
	if httpClient == nil {
		httpClient = http.DefaultClient
	}

	webrtcConfiguration := cfg.WebRTCConfiguration
	if webrtcConfiguration == nil {
		webrtcConfiguration = &webrtc.Configuration{
			ICEServers: []webrtc.ICEServer{
				{
					URLs: []string{"stun:stun.l.google.com:19302"},
				},
			},
		}
	}
	return &sendaroundClient{
		serverURL:           serverURL,
		webrtc:              webrtc.NewAPI(),
		httpClient:          httpClient,
		webrtcConfiguration: *webrtcConfiguration,
	}
}

func (client *sendaroundClient) Offer() (conn *Uploader, err error) {
	// Create a new RTCPeerConnection
	peerConnection, err := client.webrtc.NewPeerConnection(client.webrtcConfiguration)
	/*
		peerConnection.OnICEConnectionStateChange(func(state webrtc.ICEConnectionState) {
			log.Println("ICE connection state changed:", state,
				peerConnection.ConnectionState())
		})
		peerConnection.OnICEGatheringStateChange(func(state webrtc.ICEGathererState) {
			log.Println("ICE gathering state changed:", state)
		})
		peerConnection.OnSignalingStateChange(func(state webrtc.SignalingState) {
			log.Println("Signaling state changed:", state)
		})
	*/

	// Create a datachannel with label 'data'
	ordered := true
	priority := webrtc.PriorityTypeHigh
	protocol := "sendaround"
	dataChannel, err := peerConnection.CreateDataChannel(sendaroundDataChannelLabel, &webrtc.DataChannelInit{
		Ordered:  &ordered,
		Protocol: &protocol,
		Priority: &priority,
	})

	// Create an offer to send to the browser
	offer, err := peerConnection.CreateOffer(nil)
	if err != nil {
		return
	}

	// Sets the LocalDescription, and starts our UDP listeners
	err = peerConnection.SetLocalDescription(offer)
	if err != nil {
		panic(err)
	}

	// Send SDP to server and retrieve new tokens
	req, err := http.NewRequest("POST",
		client.serverURL.ResolveReference(&url.URL{Path: "offer"}).String(),
		strings.NewReader(offer.SDP))
	if err != nil {
		log.Fatal(err)
	}
	req.ContentLength = int64(len([]byte(offer.SDP)))
	req.Header.Set("Accept", "application/json")
	resp, err := client.httpClient.Do(req)
	if err != nil {
		log.Fatal(err)
		return
	}
	if resp.StatusCode != 200 {
		log.Fatalf("Server says: %s", resp.Status)
		return
	}
	defer resp.Body.Close()
	result := new(internal.CreateOfferResponse)
	if err = json.NewDecoder(resp.Body).Decode(result); err != nil {
		return
	}
	u, err := url.Parse(result.Url)
	if err != nil {
		return
	}

	server := &Uploader{
		dataChannel: internal.NewDataChannel(dataChannel),
		url:         u,
		token:       result.Token,
	}

	server.init()

	go func() {
		var err error
		defer func() {
			if err != nil {
				server.changeState(ConnectionState{Type: Failed, Error: err})
			}
		}()

		// Wait for answer SDP from handshake server
		req, err := http.NewRequest("POST",
			client.serverURL.ResolveReference(&url.URL{
				Path: fmt.Sprintf("offer/%s", url.PathEscape(result.AnswerReceivalToken)),
			}).String(),
			strings.NewReader(offer.SDP))
		if err != nil {
			log.Fatal(err)
		}
		req.ContentLength = int64(len([]byte(offer.SDP)))
		req.Header.Set("Accept", "application/sdp")
		resp, err := client.httpClient.Do(req)
		if err != nil {
			log.Fatal(err)
			return
		}
		if resp.StatusCode != 200 {
			log.Fatalf("Server says: %s", resp.Status)
			return
		}
		defer resp.Body.Close()
		answerSdp, err := ioutil.ReadAll(resp.Body)
		if err != nil {
			return
		}

		// Set answer SDP as remote description
		if err = peerConnection.SetRemoteDescription(webrtc.SessionDescription{
			Type: webrtc.SDPTypeAnswer,
			SDP:  string(answerSdp),
		}); err != nil {
			return
		}
	}()

	conn = server
	return
}

func (client *sendaroundClient) Receive(token string) (conn *Downloader, err error) {
	dataChannelChan := make(chan *webrtc.DataChannel, 1)

	// Create a new RTCPeerConnection
	peerConnection, err := client.webrtc.NewPeerConnection(client.webrtcConfiguration)
	/*
		peerConnection.OnICEConnectionStateChange(func(state webrtc.ICEConnectionState) {
			log.Println("ICE connection state changed:", state)
		})
		peerConnection.OnSignalingStateChange(func(state webrtc.SignalingState) {
			log.Println("Signaling state changed:", state)
		})
		peerConnection.OnICEGatheringStateChange(func(state webrtc.ICEGathererState) {
			log.Println("ICE gathering state changed:", state)
		})
	*/

	peerConnection.OnDataChannel(func(dataChannel *webrtc.DataChannel) {
		if dataChannel.Label() != sendaroundDataChannelLabel {
			// We expected a sendaround data channel but got something else => protocol violation
			peerConnection.Close()
		}
		dataChannelChan <- dataChannel
	})

	// Fetch offer SDP
	u := client.serverURL.ResolveReference(&url.URL{
		Path: fmt.Sprintf("offer/%s", url.PathEscape(token)),
	}).String()
	req, err := http.NewRequest("GET", u, nil)
	if err != nil {
		log.Fatal(err)
	}
	req.Header.Set("Accept", "application/sdp")
	resp, err := client.httpClient.Do(req)
	if err != nil {
		log.Fatal(err)
		return
	}
	if resp.StatusCode != 200 {
		log.Fatalf("Server says: %s", resp.Status)
		return
	}
	offerSdp, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		return
	}
	if err = peerConnection.SetRemoteDescription(
		webrtc.SessionDescription{
			SDP:  string(offerSdp),
			Type: webrtc.SDPTypeOffer,
		}); err != nil {
		return
	}

	answer, err := peerConnection.CreateAnswer(nil)
	if err != nil {
		return
	}

	// Sets the LocalDescription, and starts our UDP listeners
	err = peerConnection.SetLocalDescription(answer)
	if err != nil {
		panic(err)
	}

	// Send SDP to server
	req, err = http.NewRequest("POST",
		client.serverURL.ResolveReference(&url.URL{
			Path: fmt.Sprintf("answer/%s", url.PathEscape(token)),
		}).String(),
		strings.NewReader(answer.SDP))
	if err != nil {
		log.Fatal(err)
	}
	req.ContentLength = int64(len([]byte(answer.SDP)))
	req.Header.Set("Accept", "application/json")
	resp, err = client.httpClient.Do(req)
	if err != nil {
		log.Fatal(err)
		return
	}
	if resp.StatusCode != 200 {
		log.Fatalf("Server says: %s", resp.Status)
		return
	}

	// TODO - Implement some way to cancel/timeout this
	dataChannel := <-dataChannelChan
	retval := &Downloader{
		dataChannel: internal.NewDataChannel(dataChannel),
	}
	retval.init()
	conn = retval
	return

}