REFACTOR: Migrate markdown functionality in ES6

app/assets/javascripts/pretty-text/engines/discourse-markdown/code.js.es6

@@ -0,0 +1,81 @@
+import { escape } from 'pretty-text/sanitizer';
+import { registerOption } from 'pretty-text/pretty-text';
+
+// Support for various code blocks
+const TEXT_CODE_CLASSES = ["text", "pre", "plain"];
+
+function codeFlattenBlocks(blocks) {
+  let result = "";
+  blocks.forEach(function(b) {
+    result += b;
+    if (b.trailing) { result += b.trailing; }
+  });
+  return result;
+}
+
+registerOption((siteSettings, opts) => {
+  opts.features.code = true;
+  opts.defaultCodeLang = siteSettings.default_code_lang;
+  opts.acceptableCodeClasses = (siteSettings.highlighted_languages || "").split("|").concat(['auto', 'nohighlight']);
+});
+
+export function setup(helper) {
+
+  helper.whiteList({
+    custom(tag, name, value) {
+      if (tag === 'code' && name === 'class') {
+        const m = /^lang\-(.+)$/.exec(value);
+        if (m) {
+          return helper.getOptions().acceptableCodeClasses.indexOf(m[1]) !== -1;
+        }
+      }
+    }
+  });
+
+  helper.replaceBlock({
+    start: /^`{3}([^\n\[\]]+)?\n?([\s\S]*)?/gm,
+    stop: /^```$/gm,
+    withoutLeading: /\[quote/gm, //if leading text contains a quote this should not match
+    emitter(blockContents, matches) {
+      const opts = helper.getOptions();
+
+      let codeLang = opts.defaultCodeLang;
+      const acceptableCodeClasses = opts.acceptableCodeClasses;
+      if (acceptableCodeClasses && matches[1] && acceptableCodeClasses.indexOf(matches[1]) !== -1) {
+        codeLang = matches[1];
+      }
+
+      if (TEXT_CODE_CLASSES.indexOf(matches[1]) !== -1) {
+        return ['p', ['pre', ['code', {'class': 'lang-nohighlight'}, codeFlattenBlocks(blockContents) ]]];
+      } else  {
+        return ['p', ['pre', ['code', {'class': 'lang-' + codeLang}, codeFlattenBlocks(blockContents) ]]];
+      }
+    }
+  });
+
+  helper.replaceBlock({
+    start: /(<pre[^\>]*\>)([\s\S]*)/igm,
+    stop: /<\/pre>/igm,
+    rawContents: true,
+    skipIfTradtionalLinebreaks: true,
+
+    emitter(blockContents) {
+      return ['p', ['pre', codeFlattenBlocks(blockContents)]];
+    }
+  });
+
+  // Ensure that content in a code block is fully escaped. This way it's not white listed
+  // and we can use HTML and Javascript examples.
+  helper.onParseNode(function(event) {
+    const node = event.node,
+    path = event.path;
+
+    if (node[0] === 'code') {
+      const regexp = (path && path[path.length-1] && path[path.length-1][0] && path[path.length-1][0] === "pre") ?
+                     / +$/g : /^ +| +$/g;
+
+      const contents = node[node.length-1];
+      node[node.length-1] = escape(contents.replace(regexp,''));
+    }
+  });
+}