Added button that copies code to clipboard

Signed-off-by: Oliver Hunt <oliver@hunt.bz>

src/HtmlUtils.js

@@ -345,6 +345,7 @@ export function bodyToHtml(content, highlights, opts) {
         }
         safeBody = sanitizeHtml(body, sanitizeHtmlParams);
         safeBody = unicodeToImage(safeBody);
+        safeBody = addCodeCopyButton(safeBody);
     }
     finally {
         delete sanitizeHtmlParams.textFilter;
@@ -363,6 +364,18 @@ export function bodyToHtml(content, highlights, opts) {
     return <span className={className} dangerouslySetInnerHTML={{ __html: safeBody }} />;
 }
 
+function addCodeCopyButton(safeBody) {
+    var el = document.createElement("div");
+    el.innerHTML = safeBody;
+    var codeBlocks = Array.from(el.getElementsByTagName("pre"));
+    codeBlocks.forEach(p => {
+        var button = document.createElement("span");
+        button.className = "mx_EventTile_copyButton";
+        p.appendChild(button);
+    });
+    return el.innerHTML;
+}
+
 export function emojifyText(text) {
     return {
         __html: unicodeToImage(escape(text)),

src/components/views/messages/TextualBody.js

@@ -62,6 +62,19 @@ module.exports = React.createClass({
         };
     },
 
+    copyToClipboard: function(text) {
+        const textArea = document.createElement("textarea");
+        textArea.value = text;
+        document.body.appendChild(textArea);
+        textArea.select();
+        try {
+            const successful = document.execCommand('copy');
+        } catch (err) {
+            console.log('Unable to copy');
+        }
+        document.body.removeChild(textArea);
+    },
+
     componentDidMount: function() {
         this._unmounted = false;
 
@@ -80,6 +93,20 @@ module.exports = React.createClass({
                     }
                 }, 10);
             }
+            const buttons = ReactDOM.findDOMNode(this).getElementsByClassName("mx_EventTile_copyButton");
+            if (buttons.length > 0) {
+                // Do this asynchronously: parsing code takes time and we don't
+                // need to block the DOM update on it.
+                setTimeout(() => {
+                    if (this._unmounted) return;
+                    for (let i = 0; i < buttons.length; i++) {
+                        buttons[i].onclick = (e) => {
+                            const copyCode = buttons[i].parentNode.getElementsByTagName("code")[0];
+                            this.copyToClipboard(copyCode.textContent);
+                        };
+                    }
+                }, 10);
+            }
         }
     },