From 5ddc02ebc854c9dca3a92f0c5940e69c75faf1e5 Mon Sep 17 00:00:00 2001
From: Bruno Windels <brunow@element.io>
Date: Wed, 5 Aug 2020 15:37:37 +0000
Subject: [PATCH] XHR request support for legacy browsers

---
 src/matrix/net/request/xhr.js | 81 +++++++++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)
 create mode 100644 src/matrix/net/request/xhr.js

diff --git a/src/matrix/net/request/xhr.js b/src/matrix/net/request/xhr.js
new file mode 100644
index 00000000..ee35311b
--- /dev/null
+++ b/src/matrix/net/request/xhr.js
@@ -0,0 +1,81 @@
+import {
+    AbortError,
+    ConnectionError
+} from "../../error.js";
+
+class RequestResult {
+    constructor(promise, xhr) {
+        this._promise = promise;
+        this._xhr = xhr;
+    }
+
+    abort() {
+        this._xhr.abort();
+    }
+
+    response() {
+        return this._promise;
+    }
+}
+
+function send(url, options) {
+    const xhr = new XMLHttpRequest();
+    xhr.open(options.method, url);
+    if (options.headers) {
+        for(const [name, value] of options.headers.entries()) {
+            xhr.setRequestHeader(name, value);
+        }
+    }
+    if (options.timeout) {
+        xhr.timeout = options.timeout;
+    }
+
+    xhr.send(options.body || null);
+
+    return xhr;
+}
+
+function xhrAsPromise(xhr, method, url) {
+    return new Promise((resolve, reject) => {
+        xhr.addEventListener("load", () => resolve(xhr));
+        xhr.addEventListener("abort", () => reject(new AbortError()));
+        xhr.addEventListener("error", () => reject(new ConnectionError(`Error ${method} ${url}`)));
+        xhr.addEventListener("timeout", () => reject(new ConnectionError(`Timeout ${method} ${url}`, true)));
+    });
+}
+
+function addCacheBuster(urlStr, random = Math.random) {
+    // XHR doesn't have a good way to disable cache,
+    // so add a random query param
+    // see https://davidtranscend.com/blog/prevent-ie11-cache-ajax-requests/
+    if (urlStr.includes("?")) {
+        urlStr = urlStr + "&";
+    } else {
+        urlStr = urlStr + "?";
+    }
+    return urlStr + `_cacheBuster=${Math.ceil(random() * Number.MAX_SAFE_INTEGER)}`;
+}
+
+export function xhrRequest(url, options) {
+    url = addCacheBuster(url);
+    const xhr = send(url, options);
+    const promise = xhrAsPromise(xhr, options.method, url).then(xhr => {
+        const {status} = xhr;
+        let body = xhr.responseText;
+        if (xhr.getResponseHeader("Content-Type") === "application/json") {
+            body = JSON.parse(body);
+        }
+        return {status, body};
+    });
+    return new RequestResult(promise, xhr);
+}
+
+export function tests() {
+    return {
+        "add cache buster": assert => {
+            const random = () => 0.5;
+            assert.equals(addCacheBuster("http://foo", random), "http://foo?_cacheBuster=5");
+            assert.equals(addCacheBuster("http://foo?bar=baz", random), "http://foo?bar=baz&_cacheBuster=5");
+        }
+    }
+}
\ No newline at end of file