Convert index to TS

Signed-off-by: Šimon Brandner <simon.bra.ag@gmail.com>

src/usercontent/index.ts

@@ -0,0 +1,53 @@
+let hasCalled = false;
+function remoteRender(event: MessageEvent): void {
+    const data = event.data;
+
+    // If we're handling secondary calls, start from scratch
+    if (hasCalled) {
+        document.body.replaceWith(document.createElement("BODY"));
+    }
+    hasCalled = true;
+
+    const img = document.createElement("span"); // we'll mask it as an image
+    img.id = "img";
+
+    const a: HTMLAnchorElement = document.createElement("a");
+    a.id = "a";
+    a.rel = "noreferrer noopener";
+    a.download = data.download;
+    // @ts-ignore
+    a.style = data.style;
+    a.style.fontFamily = "Arial, Helvetica, Sans-Serif";
+    a.href = window.URL.createObjectURL(data.blob);
+    a.appendChild(img);
+    a.appendChild(document.createTextNode(data.textContent));
+
+    // Apply image style after so we can steal the anchor's colour.
+    // Style copied from a rendered version of mx_MFileBody_download_icon
+    // @ts-ignore
+    img.style = data.imgStyle ?? "";
+    img.style.width = "12px";
+    img.style.height = "12px";
+    img.style.webkitMaskSize = "12px";
+    img.style.webkitMaskPosition = "center";
+    img.style.webkitMaskRepeat = "no-repeat";
+    img.style.display = "inline-block";
+    img.style.webkitMaskImage = `url('${data.imgSrc}')`;
+    img.style.backgroundColor = `${a.style.color}`;
+
+    const body = document.body;
+    // Don't display scrollbars if the link takes more than one line to display.
+    body.style .margin = "0px";
+    body.style.overflow = "hidden";
+    body.appendChild(a);
+
+    if (event.data.auto) {
+        a.click(); // try to trigger download automatically
+    }
+}
+
+window.onmessage = function(e: MessageEvent): void {
+    if (e.origin === window.location.origin) {
+        if (e.data.blob) remoteRender(e);
+    }
+};