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226import { type ITerminalAddon, Terminal } from '@xterm/xterm'
const MAGIC_START = 0x07
const BUFFER_SIZE = 10240
const MAGIC_STRING_BYTES = new TextEncoder().encode('::SSC:')
const DEFAULT_STUN_SERVER: RTCIceServer = {
urls: [
'stun:stun.cloudflare.com:3478',
'stun:stun.nextcloud.com:3478',
'stun:stun.nextcloud.com:443',
]
}
export class ScreenShareAddon implements ITerminalAddon {
private term!: Terminal
private video: HTMLVideoElement
private buffer: Uint8Array = new Uint8Array(BUFFER_SIZE)
private bufferIndex = 0
private matchState = 0
private pc: RTCPeerConnection | null = null
constructor() {
this.video = document.createElement('video')
this.video.className =
'rounded-[15px] absolute top-1/2 left-1/2 ' +
'-translate-x-1/2 -translate-y-1/2 ' +
'h-[80%] aspect-video bg-black'
this.video.autoplay = true
this.video.muted = true
this.video.playsInline = true
}
activate(terminal: Terminal): void {
this.term = terminal
}
dispose(): void {
this.pc?.close()
this.video.remove()
}
async requestDataChannel(args: string[]): Promise<string> {
if (this.pc) {
this.pc.close()
}
const pc = this.pc = new RTCPeerConnection({
iceServers: [DEFAULT_STUN_SERVER]
})
const dc = pc.createDataChannel('bootstrap')
let mediaPc: RTCPeerConnection | null = null
dc.onopen = () => {
// send video request
this._requestScreenShare().then(pc => {
if (pc === null) {
// TODO add log
this.pc?.close()
}
mediaPc = pc
const sdp = mediaPc.localDescription!
dc.send(JSON.stringify(sdp))
})
}
dc.onmessage = (event) => {
if (mediaPc === null) {
console.error('No media peer connection to accept answer')
return
}
const ans = JSON.parse(event.data)
if (ans?.type !== 'answer') {
console.error('Invalid answer received', ans)
return
}
mediaPc.setRemoteDescription(new RTCSessionDescription(ans))
}
dc.onclose = () => {
mediaPc?.close()
this.dispose()
}
await pc.setLocalDescription(await pc.createOffer())
// wait for ICE gathering to complete
await new Promise((resolve) => {
pc.onicegatheringstatechange = () => {
if (pc.iceGatheringState === 'complete') {
resolve(null)
}
}
// in case icegatheringstatechange doesn't fire
setTimeout(resolve, 1000)
})
const offer = pc.localDescription?.sdp
return `./screen-share-cli ${args.join(' ')} -o ` + btoa(offer || '')
}
async _requestScreenShare() {
const pc = new RTCPeerConnection({
iceServers: [DEFAULT_STUN_SERVER]
})
const term = this.term!
if (!this.video.parentNode) {
term.element?.appendChild(this.video)
}
const stream = this.video.srcObject as MediaStream | null
const video = this.video
if (stream) {
stream.getTracks().forEach(t => t.stop())
this.video.srcObject = null
}
const newStream = new MediaStream()
pc.ontrack = (event) => {
if (!event.track) {
return
}
newStream.addTrack(event.track)
if (!video.srcObject) {
video.srcObject = newStream
}
}
// prepare offer
pc.addTransceiver('video', { direction: 'recvonly' })
pc.addTransceiver('audio', { direction: 'recvonly' })
await pc.setLocalDescription(await pc.createOffer())
// wait for ICE gathering to complete
await new Promise((resolve) => {
pc.onicegatheringstatechange = () => {
if (pc.iceGatheringState === 'complete') {
resolve(null)
}
}
// in case icegatheringstatechange doesn't fire
setTimeout(resolve, 1000)
})
return pc
}
_acceptAnswer(answerB64: string) {
if (!this.pc) {
console.error('No peer connection to accept answer')
return
}
const answerSdp = atob(answerB64)
this.pc.setRemoteDescription(new RTCSessionDescription({
type: 'answer',
sdp: answerSdp
})).catch(err => {
console.error('Failed to set remote description', err)
})
}
_reset() {
this.bufferIndex = 0
this.matchState = 0
}
_filterByByte(byte: number) {
if (this.matchState === 2) {
// Ignore CR (0x0D) and LF (0x0A) bytes
if (byte === 0x0D || byte === 0x0A) {
return
}
if (byte === '.'.charCodeAt(0)) { // End of data marker
const sscMessage = new TextDecoder().decode(this.buffer.slice(0, this.bufferIndex)).trim()
if (sscMessage.startsWith('OFFER:')) {
// handle offer, not supported in this side
// console.log('offer', atob(sscMessage.substring(6)))
} else if (sscMessage.startsWith('ANSWER:')) {
// handle answer
this._acceptAnswer(sscMessage.substring(7))
} else if (sscMessage.startsWith('CLOSE:')) {
// handle close
console.log('close', sscMessage.substring(6))
this.dispose()
}
this._reset()
} else {
if (this.bufferIndex < BUFFER_SIZE) {
this.buffer[this.bufferIndex++] = byte
} else {
// buffer overflow, reset
this._reset()
}
}
return
}
if (this.matchState === 1) {
if (this.bufferIndex < MAGIC_STRING_BYTES.length) {
this.buffer[this.bufferIndex++] = byte
if (this.bufferIndex === MAGIC_STRING_BYTES.length) {
let matched = true
for (let i = 0; i < MAGIC_STRING_BYTES.length; i++) {
if (this.buffer[i] !== MAGIC_STRING_BYTES[i]) {
matched = false
break
}
}
if (matched) {
this.matchState = 2
this.bufferIndex = 0 // Clear buffer for data
} else {
this._reset()
}
}
}
return
}
if (byte === MAGIC_START && this.matchState === 0) {
this.matchState = 1
this.bufferIndex = 0
} else {
this._reset()
}
}
handleTermOutput = (uint8Array: Uint8Array) => {
for (const x of uint8Array) {
this._filterByByte(x)
}
}
}