Add shortcut to toggle the left sidebar

Map sidebar toggle to `\m`.

Initialise the code after a timeout to account for Gmail's initial
loading screen.

Needed to use an `as HTMLElement` cast in order to get the code to
compile:
https://github.com/Microsoft/TypeScript/issues/16920

    src/sidebar.ts:10:5 - error TS2740: Type 'Element' is missing the
    following properties from type 'HTMLElement': accessKey,
    accessKeyLabel, autocapitalize, dir, and 110 more.

2 files changed, 40 insertions, 1 deletions

diff --git a/src/index.ts b/src/index.ts
index 538d0c4..8ab0071 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -6,4 +6,8 @@
 // ==/UserScript==
 
 import './style';
-import './sidebar';
+import sidebar from './sidebar';
+
+window.setTimeout(function() {
+	sidebar();
+}, 3000);
diff --git a/src/sidebar.ts b/src/sidebar.ts
index 4e106e1..05e5d22 100644
--- a/src/sidebar.ts
+++ b/src/sidebar.ts
@@ -1 +1,36 @@
 import { SIDEBAR } from './gmail_css_class';
+
+export default function() {
+	var key_codes: { [index: string]: number } = {
+		SLASH: 220,
+		M: 77
+	}
+
+	var key_buffer: number[] = [];
+
+	var sidebar: HTMLElement = document.getElementsByClassName(SIDEBAR)[0] as HTMLElement;
+
+	document.addEventListener('keydown', function(e) {
+		if (e.keyCode === key_codes.SLASH) {
+			key_buffer.push(e.keyCode);
+		}
+		if (e.keyCode === key_codes.M) {
+			key_buffer.push(e.keyCode);
+		}
+	});
+
+	document.addEventListener('keyup', function(e) {
+		if (key_buffer.length >= 2) {
+			if (key_buffer[0] === key_codes.SLASH
+				&& key_buffer[1] === key_codes.M) {
+				if (sidebar.offsetParent === null) {
+					sidebar.style.display = 'block';
+				}
+				else {
+					sidebar.style.display = 'none';
+				}
+			}
+			key_buffer = [];
+		}
+	});
+})