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import { field, logger, Logger } from "@coder/logger"

import { Emitter } from "../common/emitter"

import { generateUuid } from "../common/util"

const decoder = new TextDecoder("utf8")

export const decode = (buffer: string | ArrayBuffer): string => {

return typeof buffer !== "string" ? decoder.decode(buffer) : buffer

}

/**

* A web socket that reconnects itself when it closes. Sending messages while

* disconnected will throw an error.

export class ReconnectingSocket {

protected readonly _onMessage = new Emitter<string | ArrayBuffer>()

public readonly onMessage = this._onMessage.event

protected readonly _onDisconnect = new Emitter<number | undefined>()

public readonly onDisconnect = this._onDisconnect.event

protected readonly _onClose = new Emitter<number | undefined>()

public readonly onClose = this._onClose.event

protected readonly _onConnect = new Emitter<void>()

public readonly onConnect = this._onConnect.event

// This helps distinguish messages between sockets.

private readonly logger: Logger

private socket?: WebSocket

private connecting?: Promise<void>

private closed = false

private readonly openTimeout = 10000

// Every time the socket fails to connect, the retry will be increasingly

// delayed up to a maximum.

private readonly retryBaseDelay = 1000

private readonly retryMaxDelay = 10000

private retryDelay?: number

private readonly retryDelayFactor = 1.5

// The socket must be connected for this amount of time before resetting the

// retry delay. This prevents rapid retries when the socket does connect but

// is closed shortly after.

private resetRetryTimeout?: NodeJS.Timeout

private readonly resetRetryDelay = 10000

private _binaryType: typeof WebSocket.prototype.binaryType = "arraybuffer"

public constructor(private customPath?: string, public readonly id: string = generateUuid(4)) {

// On Firefox the socket seems to somehow persist a page reload so the close

// event runs and we see "attempting to reconnect".

if (typeof window !== "undefined") {

window.addEventListener("beforeunload", () => this.close())

}

this.logger = logger.named(this.id)

}

public set binaryType(b: typeof WebSocket.prototype.binaryType) {

this._binaryType = b

if (this.socket) {

this.socket.binaryType = b

}

/**

* Permanently close the connection. Will not attempt to reconnect. Will

* remove event listeners.

public close(code?: number): void {

if (this.closed) {

return

}

if (code) {

this.logger.info(`closing with code ${code}`)

}

if (this.resetRetryTimeout) {

clearTimeout(this.resetRetryTimeout)

}

this.closed = true

if (this.socket) {

this.socket.close()

} else {

this._onClose.emit(code)

}

public dispose(): void {

this._onMessage.dispose()

this._onDisconnect.dispose()

this._onClose.dispose()

this._onConnect.dispose()

this.logger.debug("disposed handlers")

}

/**

* Send a message on the socket. Logs an error if currently disconnected.

public send(message: string | ArrayBuffer): void {

this.logger.trace(() => ["sending message", field("message", decode(message))])

if (!this.socket) {

return logger.error("tried to send message on closed socket")

}

this.socket.send(message)

}

/**

* Connect to the socket. Can also be called to wait until the connection is

* established in the case of disconnections. Multiple calls will be handled

* correctly.

public async connect(): Promise<void> {

if (!this.connecting) {

this.connecting = new Promise((resolve, reject) => {

const tryConnect = (): void => {

if (this.closed) {

return reject(new Error("disconnected")) // Don't keep trying if we've closed permanently.

}

if (typeof this.retryDelay === "undefined") {

this.retryDelay = 0

} else {

this.retryDelay = this.retryDelay * this.retryDelayFactor || this.retryBaseDelay

if (this.retryDelay > this.retryMaxDelay) {

this.retryDelay = this.retryMaxDelay

}

this._connect()

.then((socket) => {

this.logger.info("connected")

this.socket = socket

this.socket.binaryType = this._binaryType

if (this.resetRetryTimeout) {

clearTimeout(this.resetRetryTimeout)

}

this.resetRetryTimeout = setTimeout(() => (this.retryDelay = undefined), this.resetRetryDelay)

this.connecting = undefined

this._onConnect.emit()

resolve()

})

.catch((error) => {

this.logger.error(`failed to connect: ${error.message}`)

tryConnect()

})

}

tryConnect()

})

}

return this.connecting

}

private async _connect(): Promise<WebSocket> {

const socket = await new Promise<WebSocket>((resolve, _reject) => {

if (this.retryDelay) {

this.logger.info(`retrying in ${this.retryDelay}ms...`)

}

setTimeout(() => {

this.logger.info("connecting...")

const socket = new WebSocket(

`${location.protocol === "https:" ? "wss" : "ws"}://${location.host}${this.customPath || location.pathname}${

location.search ? `?${location.search}` : ""

)

const reject = (): void => {

_reject(new Error("socket closed"))

}

const timeout = setTimeout(() => {

// eslint-disable-next-line @typescript-eslint/no-use-before-define

socket.removeEventListener("open", open)

socket.removeEventListener("close", reject)

_reject(new Error("timeout"))

}, this.openTimeout)

const open = (): void => {

clearTimeout(timeout)

socket.removeEventListener("close", reject)

resolve(socket)

}

socket.addEventListener("open", open)

socket.addEventListener("close", reject)

}, this.retryDelay)

})

socket.addEventListener("message", (event) => {

this.logger.trace(() => ["got message", field("message", decode(event.data))])

this._onMessage.emit(event.data)

})

socket.addEventListener("close", (event) => {

this.socket = undefined

if (!this.closed) {

this._onDisconnect.emit(event.code)

// It might be closed in the event handler.

if (!this.closed) {

this.logger.info("connection closed; attempting to reconnect")

this.connect()

}

} else {

this._onClose.emit(event.code)

this.logger.info("connection closed permanently")

}

})

return socket

}

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