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import { EventEmitter } from "node:events";
import http from "node:http";
import { isNil } from "@cern/nodash";
import VarBuffer from "./VarBuffer.js";
import Agent from "agentkeepalive";
const httpAgent = new Agent({ timeout: 10000 });
const httpsAgent = new Agent.HttpsAgent({ timeout: 10000 });
/**
* @typedef {import('http').ClientRequest} Request
* @typedef {import('http').IncomingMessage} Response
*
* @typedef {{ user: string, password: string }} Authentication
* @typedef {{ src: string, auth?: Authentication, throttle?: number }} HTTPConsumerOptions
*/
/**
* @implements {CamExpress.Consumer}
* @extends {EventEmitter}
* @emits :
* - 'frame' when a new jpeg frame is received from source
* - 'error' when an error occurs
* - 'close' once the connection with source is closed
*/
class HTTPConsumer extends EventEmitter {
/**
* @param {HTTPConsumerOptions} options
*/
constructor(options) {
super();
this.src = options?.src ?? "";
this.user = options?.auth?.user;
this.pass = options?.auth?.password;
this._initialThrottle = options?.throttle;
this.updateThrottle(options?.throttle);
this._connected = false;
this._buffer = new VarBuffer();
/** @type {Request|null} */
this._req = null;
/** @type {NodeJS.Timeout|undefined} */
this._pollingTimer = undefined;
this.emitError = (err) => {
if (this._connected) {
this.emit("error", err);
}
};
this.emitFrame = this.emit.bind(this, "frame");
}
updateThrottle(throttle) {
throttle = throttle ?? HTTPConsumer.DEFAULT_FRAME_THROTTLE; // Assert non null value
if (throttle < HTTPConsumer.MIN_THROTTLE_VALUE) {
throttle = HTTPConsumer.MIN_THROTTLE_VALUE; // Assert throttle min value
console.warn(
`The throttle ${throttle} is too low and` +
` was replaced with ${HTTPConsumer.MIN_THROTTLE_VALUE} ms`
);
}
this.throttle = throttle;
}
connect() {
if (this._connected) { return; }
this._connected = true;
const opts = {
agent: this.src.includes("https") ? httpsAgent : httpAgent,
auth: (this.user && this.pass) ? `${this.user}:${this.pass}` : undefined
};
const httpPolling = () => {
if (!this._connected) {
return; // Avoid keeping recalling itself if the connexion was closed
}
const startTime = Date.now(); // time at the request queuing
this._buffer.reset();
const req = this._req = http.get(this.src, opts);
req
.on("error", this.emitError)
.once("close", () => {
req.removeAllListeners();
// disconnect if http polling has been stopped due to some errors
if (req === this._req && isNil(this._pollingTimer)) {
this.disconnect();
}
})
.on("response", (res) => {
res
.on("error", this.emitError)
.once("close", () => res.removeAllListeners());
if ((res.headers["content-type"] ?? "").includes("image/jpeg")) {
res
.on("data", (chunk) => this._buffer.add(chunk))
.on("end", () => {
if (req !== this._req || !this._connected) { return; }
const endTime = Date.now(); // time at the request end
const elapsedTime = endTime - startTime;
const diffThrottle = this.throttle - elapsedTime;
const toWait = diffThrottle > HTTPConsumer.MIN_FRAME_THROTTLE ?
diffThrottle :
HTTPConsumer.MIN_FRAME_THROTTLE;
if (diffThrottle < 0) {
console.warn(
`The throttle ${this.throttle} is too low and was not applied`
);
}
this.emitFrame(this._buffer.buffer());
// stop polling if disconnection occurs on 'frame' event
if (!this._connected) { return; }
// When the previous frame received, we fetch the next one
// if still connected
this._pollingTimer = setTimeout(() => {
this._pollingTimer = undefined;
httpPolling(); // Recursive call
}, toWait);
});
}
else {
this.emitError(new Error("No JPEG image detected"));
this.disconnect();
}
})
.end();
};
httpPolling(); // Begin polling loop
}
disconnect() {
if (!this._connected) { return; }
this._connected = false;
clearTimeout(this._pollingTimer);
this._pollingTimer = undefined;
this.emit("close");
this._req = null;
}
}
// default interval between a frame receival and the next frame request
HTTPConsumer.DEFAULT_FRAME_THROTTLE = 1000; // ms
// minimum throttle that will be applied between two frames
HTTPConsumer.MIN_FRAME_THROTTLE = 0; // ms
// minimum input value for the throttle property
HTTPConsumer.MIN_THROTTLE_VALUE = 200; // ms (~ 5 fps)
export default HTTPConsumer;
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