Add fix backtick code block module

lib/modules/fixCodeBlock.js

@@ -0,0 +1,73 @@
+/* @flow */
+
+import { markdown } from 'snudown-js';
+
+import { Module } from '../core/module';
+
+import { watchForThings, regexes } from '../utils';
+
+import { ajax } from '../environment';
+
+export const module: Module<*> = new Module('fixBacktickCodeBlocks');
+
+module.moduleName = 'fixBacktickCodeBlocks'; // add the friendly name to locales/locales/en.js for i18n
+module.category = 'browsingCategory'; // categories from locales/locales/en.js
+module.description = 'Fix Backtick Code Blocks'; // i18n
+
+module.beforeLoad = () => {
+	watchForThings(['post', 'comment', 'message'], rewriteCodeBlocks);
+};
+
+async function rewriteCodeBlocks(thing) {
+	const path = thing.element.getAttribute('data-permalink'); // || thing.element.getAttribute('data-url'); // For main subreddit pages, but those need a listener on the expando div
+	if (!path) {
+		return;
+	}
+	// Find the <div class=md> and prepare to edit it
+	const markdownBody = thing.element.querySelector('.md');
+	if (!markdownBody) {
+		return;
+	}
+	if (!markdownBody.textContent.includes('```') && !markdownBody.innerHTML.includes('<code>')) {
+		return;
+	}
+
+	// Ideally, you would parse something (innerHTML?) and not have to go through the network at all.
+	// Code copied from sourceSnudown module
+	let sourceText;
+
+	const response = await ajax({
+		url: `${path}.json`,
+		query: { raw_json: 1 },
+		type: 'json',
+	});
+
+	if (regexes.commentPermalink.test(path)) {
+		sourceText = response[1].data.children[0].data.body;
+	} else if (regexes.comments.test(path)) {
+		sourceText = response[0].data.children[0].data.selftext;
+	} else {
+		const postId: string = ((/\/(\w*)\/?$/).exec(path): any)[1];
+		const data = response.data.children[0].data;
+		if (data.id === postId) {
+			sourceText = data.body;
+		} else {
+			// The message we want is a reply to a PM/modmail, but reddit returns the whole thread.
+			// So, we have to dig into the replies to find the message we want.
+			sourceText = data.replies.data.children.find(({ data: { id } }) => id === postId).data.body;
+		}
+	}
+
+	// Now that we have the response, we can fix triple backticks
+	// Magic regex magic from magic people on github
+	const reflowedMarkdown = sourceText.replace(
+		/^```([\s\S]+?)^```/gm,
+		(_, code) => `\n${code.split('\n').slice(1).map(l => `    ${l}`).join('\n')}`,
+	);
+
+	// Turn md to html
+	const htmlMarkdown = markdown(reflowedMarkdown);
+
+	// Change the DOM
+	markdownBody.innerHTML = htmlMarkdown;
+}