New "browse" UI

Also, separated out browse, ?meta, and ?module request handlers.

Fixes #82

modules/utils/getHighlights.js

@@ -0,0 +1,82 @@
+import path from 'path';
+import hljs from 'highlight.js';
+
+import getContentType from './getContentType.js';
+
+function escapeHTML(code) {
+  return code
+    .replace(/&/g, '&')
+    .replace(/</g, '&lt;')
+    .replace(/>/g, '&gt;')
+    .replace(/"/g, '&quot;')
+    .replace(/'/g, '&#039;');
+}
+
+// These should probably be added to highlight.js auto-detection.
+const extLanguages = {
+  map: 'json',
+  mjs: 'javascript',
+  tsbuildinfo: 'json',
+  tsx: 'typescript',
+  vue: 'html'
+};
+
+function getLanguage(file) {
+  // Try to guess the language based on the file extension.
+  const ext = path.extname(file).substr(1);
+
+  if (ext) {
+    return extLanguages[ext] || ext;
+  }
+
+  const contentType = getContentType(file);
+
+  if (contentType === 'text/plain') {
+    return 'text';
+  }
+
+  return null;
+}
+
+function getLines(code) {
+  return code
+    .split('\n')
+    .map((line, index, array) =>
+      index === array.length - 1 ? line : line + '\n'
+    );
+}
+
+/**
+ * Returns an array of HTML strings that highlight the given source code.
+ */
+export default function getHighlights(code, file) {
+  const language = getLanguage(file);
+
+  if (!language) {
+    return null;
+  }
+
+  if (language === 'text') {
+    return getLines(code).map(escapeHTML);
+  }
+
+  try {
+    let continuation = false;
+    const hi = getLines(code).map(line => {
+      const result = hljs.highlight(language, line, false, continuation);
+      continuation = result.top;
+      return result;
+    });
+
+    return hi.map(result =>
+      result.value.replace(
+        /<span class="hljs-(\w+)">/g,
+        '<span class="code-$1">'
+      )
+    );
+  } catch (error) {
+    // Probably an "unknown language" error.
+    // console.error(error);
+    return null;
+  }
+}