feat: add CodeMirror 6 wrapper module

src/editor/codemirror-setup.js

@@ -0,0 +1,121 @@
+// CodeMirror 6 wrapper module
+// Provides createEditor() and getLanguageExtension() for the rest of the app.
+
+const {
+  EditorView,
+  keymap,
+  lineNumbers,
+  highlightActiveLine,
+  drawSelection,
+} = require('@codemirror/view');
+const { EditorState } = require('@codemirror/state');
+const { markdown, markdownLanguage } = require('@codemirror/lang-markdown');
+const { javascript } = require('@codemirror/lang-javascript');
+const { html } = require('@codemirror/lang-html');
+const { css } = require('@codemirror/lang-css');
+const { json } = require('@codemirror/lang-json');
+const { python } = require('@codemirror/lang-python');
+const {
+  defaultKeymap,
+  history,
+  historyKeymap,
+  indentWithTab,
+} = require('@codemirror/commands');
+const {
+  searchKeymap,
+  highlightSelectionMatches,
+} = require('@codemirror/search');
+const {
+  autocompletion,
+  completionKeymap,
+} = require('@codemirror/autocomplete');
+const {
+  bracketMatching,
+  foldGutter,
+  indentOnInput,
+} = require('@codemirror/language');
+const { oneDark } = require('@codemirror/theme-one-dark');
+
+/**
+ * Create a CodeMirror 6 editor instance.
+ *
+ * @param {HTMLElement} parentElement - DOM element to mount the editor in
+ * @param {Object}  options
+ * @param {string}  options.content          - initial document content (default '')
+ * @param {Function} options.onChange        - called with new content string on every doc change
+ * @param {boolean} options.isDark           - apply oneDark theme when true (default false)
+ * @param {boolean} options.showLineNumbers  - show line-number gutter (default true)
+ * @returns {EditorView} the created editor view
+ */
+function createEditor(parentElement, options = {}) {
+  const {
+    content = '',
+    onChange = () => {},
+    isDark = false,
+    showLineNumbers = true,
+  } = options;
+
+  const extensions = [
+    markdown({ base: markdownLanguage }),
+    history(),
+    drawSelection(),
+    highlightActiveLine(),
+    bracketMatching(),
+    indentOnInput(),
+    highlightSelectionMatches(),
+    autocompletion(),
+    foldGutter(),
+    keymap.of([
+      ...defaultKeymap,
+      ...historyKeymap,
+      ...searchKeymap,
+      ...completionKeymap,
+      indentWithTab,
+    ]),
+    EditorView.updateListener.of((update) => {
+      if (update.docChanged) {
+        onChange(update.state.doc.toString());
+      }
+    }),
+    EditorView.lineWrapping,
+  ];
+
+  if (showLineNumbers) {
+    extensions.push(lineNumbers());
+  }
+
+  if (isDark) {
+    extensions.push(oneDark);
+  }
+
+  const state = EditorState.create({ doc: content, extensions });
+  const view = new EditorView({ state, parent: parentElement });
+  return view;
+}
+
+/**
+ * Return the appropriate CodeMirror language extension for a given language name.
+ *
+ * Supported values: javascript, js, html, css, json, python, py, markdown.
+ * Falls back to markdown when the language is unrecognised.
+ *
+ * @param {string} lang - language identifier
+ * @returns {Extension} CodeMirror language extension
+ */
+function getLanguageExtension(lang) {
+  const languages = {
+    javascript,
+    js: javascript,
+    html,
+    css,
+    json,
+    python,
+    py: python,
+    markdown: () => markdown({ base: markdownLanguage }),
+  };
+
+  const factory = languages[lang];
+  return factory ? factory() : markdown({ base: markdownLanguage });
+}
+
+module.exports = { createEditor, getLanguageExtension };