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Filename : polling.js
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"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.Polling = void 0;
const transport_1 = require("../transport");
const zlib_1 = require("zlib");
const accepts = require("accepts");
const debug_1 = require("debug");
const debug = (0, debug_1.default)("engine:polling");
const compressionMethods = {
    gzip: zlib_1.createGzip,
    deflate: zlib_1.createDeflate,
};
class Polling extends transport_1.Transport {
    /**
     * HTTP polling constructor.
     */
    constructor(req) {
        super(req);
        this.closeTimeout = 30 * 1000;
    }
    /**
     * Transport name
     */
    get name() {
        return "polling";
    }
    /**
     * Overrides onRequest.
     *
     * @param req
     *
     * @private
     */
    onRequest(req) {
        const res = req.res;
        // remove the reference to the ServerResponse object (as the first request of the session is kept in memory by default)
        req.res = null;
        if (req.getMethod() === "get") {
            this.onPollRequest(req, res);
        }
        else if (req.getMethod() === "post") {
            this.onDataRequest(req, res);
        }
        else {
            res.writeStatus("500 Internal Server Error");
            res.end();
        }
    }
    /**
     * The client sends a request awaiting for us to send data.
     *
     * @private
     */
    onPollRequest(req, res) {
        if (this.req) {
            debug("request overlap");
            // assert: this.res, '.req and .res should be (un)set together'
            this.onError("overlap from client");
            res.writeStatus("500 Internal Server Error");
            res.end();
            return;
        }
        debug("setting request");
        this.req = req;
        this.res = res;
        const onClose = () => {
            this.writable = false;
            this.onError("poll connection closed prematurely");
        };
        const cleanup = () => {
            this.req = this.res = null;
        };
        req.cleanup = cleanup;
        res.onAborted(onClose);
        this.writable = true;
        this.emit("ready");
        // if we're still writable but had a pending close, trigger an empty send
        if (this.writable && this.shouldClose) {
            debug("triggering empty send to append close packet");
            this.send([{ type: "noop" }]);
        }
    }
    /**
     * The client sends a request with data.
     *
     * @private
     */
    onDataRequest(req, res) {
        if (this.dataReq) {
            // assert: this.dataRes, '.dataReq and .dataRes should be (un)set together'
            this.onError("data request overlap from client");
            res.writeStatus("500 Internal Server Error");
            res.end();
            return;
        }
        const expectedContentLength = Number(req.headers["content-length"]);
        if (!expectedContentLength) {
            this.onError("content-length header required");
            res.writeStatus("411 Length Required").end();
            return;
        }
        if (expectedContentLength > this.maxHttpBufferSize) {
            this.onError("payload too large");
            res.writeStatus("413 Payload Too Large").end();
            return;
        }
        const isBinary = "application/octet-stream" === req.headers["content-type"];
        if (isBinary && this.protocol === 4) {
            return this.onError("invalid content");
        }
        this.dataReq = req;
        this.dataRes = res;
        let buffer;
        let offset = 0;
        const headers = {
            // text/html is required instead of text/plain to avoid an
            // unwanted download dialog on certain user-agents (GH-43)
            "Content-Type": "text/html",
        };
        this.headers(req, headers);
        for (let key in headers) {
            res.writeHeader(key, String(headers[key]));
        }
        const onEnd = (buffer) => {
            this.onData(buffer.toString());
            this.onDataRequestCleanup();
            res.cork(() => {
                res.end("ok");
            });
        };
        res.onAborted(() => {
            this.onDataRequestCleanup();
            this.onError("data request connection closed prematurely");
        });
        res.onData((arrayBuffer, isLast) => {
            const totalLength = offset + arrayBuffer.byteLength;
            if (totalLength > expectedContentLength) {
                this.onError("content-length mismatch");
                res.close(); // calls onAborted
                return;
            }
            if (!buffer) {
                if (isLast) {
                    onEnd(Buffer.from(arrayBuffer));
                    return;
                }
                buffer = Buffer.allocUnsafe(expectedContentLength);
            }
            Buffer.from(arrayBuffer).copy(buffer, offset);
            if (isLast) {
                if (totalLength != expectedContentLength) {
                    this.onError("content-length mismatch");
                    res.writeStatus("400 Content-Length Mismatch").end();
                    this.onDataRequestCleanup();
                    return;
                }
                onEnd(buffer);
                return;
            }
            offset = totalLength;
        });
    }
    /**
     * Cleanup request.
     *
     * @private
     */
    onDataRequestCleanup() {
        this.dataReq = this.dataRes = null;
    }
    /**
     * Processes the incoming data payload.
     *
     * @param {String} encoded payload
     * @private
     */
    onData(data) {
        debug('received "%s"', data);
        const callback = (packet) => {
            if ("close" === packet.type) {
                debug("got xhr close packet");
                this.onClose();
                return false;
            }
            this.onPacket(packet);
        };
        if (this.protocol === 3) {
            this.parser.decodePayload(data, callback);
        }
        else {
            this.parser.decodePayload(data).forEach(callback);
        }
    }
    /**
     * Overrides onClose.
     *
     * @private
     */
    onClose() {
        if (this.writable) {
            // close pending poll request
            this.send([{ type: "noop" }]);
        }
        super.onClose();
    }
    /**
     * Writes a packet payload.
     *
     * @param {Object} packet
     * @private
     */
    send(packets) {
        this.writable = false;
        if (this.shouldClose) {
            debug("appending close packet to payload");
            packets.push({ type: "close" });
            this.shouldClose();
            this.shouldClose = null;
        }
        const doWrite = (data) => {
            const compress = packets.some((packet) => {
                return packet.options && packet.options.compress;
            });
            this.write(data, { compress });
        };
        if (this.protocol === 3) {
            this.parser.encodePayload(packets, this.supportsBinary, doWrite);
        }
        else {
            this.parser.encodePayload(packets, doWrite);
        }
    }
    /**
     * Writes data as response to poll request.
     *
     * @param {String} data
     * @param {Object} options
     * @private
     */
    write(data, options) {
        debug('writing "%s"', data);
        this.doWrite(data, options, () => {
            this.req.cleanup();
            this.emit("drain");
        });
    }
    /**
     * Performs the write.
     *
     * @private
     */
    doWrite(data, options, callback) {
        // explicit UTF-8 is required for pages not served under utf
        const isString = typeof data === "string";
        const contentType = isString
            ? "text/plain; charset=UTF-8"
            : "application/octet-stream";
        const headers = {
            "Content-Type": contentType,
        };
        const respond = (data) => {
            this.headers(this.req, headers);
            this.res.cork(() => {
                Object.keys(headers).forEach((key) => {
                    this.res.writeHeader(key, String(headers[key]));
                });
                this.res.end(data);
            });
            callback();
        };
        if (!this.httpCompression || !options.compress) {
            respond(data);
            return;
        }
        const len = isString ? Buffer.byteLength(data) : data.length;
        if (len < this.httpCompression.threshold) {
            respond(data);
            return;
        }
        const encoding = accepts(this.req).encodings(["gzip", "deflate"]);
        if (!encoding) {
            respond(data);
            return;
        }
        this.compress(data, encoding, (err, data) => {
            if (err) {
                this.res.writeStatus("500 Internal Server Error");
                this.res.end();
                callback(err);
                return;
            }
            headers["Content-Encoding"] = encoding;
            respond(data);
        });
    }
    /**
     * Compresses data.
     *
     * @private
     */
    compress(data, encoding, callback) {
        debug("compressing");
        const buffers = [];
        let nread = 0;
        compressionMethods[encoding](this.httpCompression)
            .on("error", callback)
            .on("data", function (chunk) {
            buffers.push(chunk);
            nread += chunk.length;
        })
            .on("end", function () {
            callback(null, Buffer.concat(buffers, nread));
        })
            .end(data);
    }
    /**
     * Closes the transport.
     *
     * @private
     */
    doClose(fn) {
        debug("closing");
        let closeTimeoutTimer;
        const onClose = () => {
            clearTimeout(closeTimeoutTimer);
            fn();
            this.onClose();
        };
        if (this.writable) {
            debug("transport writable - closing right away");
            this.send([{ type: "close" }]);
            onClose();
        }
        else if (this.discarded) {
            debug("transport discarded - closing right away");
            onClose();
        }
        else {
            debug("transport not writable - buffering orderly close");
            this.shouldClose = onClose;
            closeTimeoutTimer = setTimeout(onClose, this.closeTimeout);
        }
    }
    /**
     * Returns headers for a response.
     *
     * @param req - request
     * @param {Object} extra headers
     * @private
     */
    headers(req, headers) {
        headers = headers || {};
        // prevent XSS warnings on IE
        // https://github.com/LearnBoost/socket.io/pull/1333
        const ua = req.headers["user-agent"];
        if (ua && (~ua.indexOf(";MSIE") || ~ua.indexOf("Trident/"))) {
            headers["X-XSS-Protection"] = "0";
        }
        headers["cache-control"] = "no-store";
        this.emit("headers", headers, req);
        return headers;
    }
}
exports.Polling = Polling;