1 files changed, 159 insertions, 0 deletions
diff --git a/app/assets/javascripts/editor/extensions/source_editor_markdown_ext.js b/app/assets/javascripts/editor/extensions/source_editor_markdown_ext.js
index 997503a12f5..76e009164f7 100644
--- a/app/assets/javascripts/editor/extensions/source_editor_markdown_ext.js
+++ b/app/assets/javascripts/editor/extensions/source_editor_markdown_ext.js
@@ -1,6 +1,165 @@
+import { debounce } from 'lodash';
+import { BLOB_PREVIEW_ERROR } from '~/blob_edit/constants';
+import createFlash from '~/flash';
+import { sanitize } from '~/lib/dompurify';
+import axios from '~/lib/utils/axios_utils';
+import { __ } from '~/locale';
+import syntaxHighlight from '~/syntax_highlight';
+import {
+  EXTENSION_MARKDOWN_PREVIEW_PANEL_CLASS,
+  EXTENSION_MARKDOWN_PREVIEW_ACTION_ID,
+  EXTENSION_MARKDOWN_PREVIEW_PANEL_WIDTH,
+  EXTENSION_MARKDOWN_PREVIEW_PANEL_PARENT_CLASS,
+  EXTENSION_MARKDOWN_PREVIEW_UPDATE_DELAY,
+} from '../constants';
 import { SourceEditorExtension } from './source_editor_extension_base';
 
+const getPreview = (text, projectPath = '') => {
+  let url;
+
+  if (projectPath) {
+    url = `/${projectPath}/preview_markdown`;
+  } else {
+    const { group, project } = document.body.dataset;
+    url = `/${group}/${project}/preview_markdown`;
+  }
+  return axios
+    .post(url, {
+      text,
+    })
+    .then(({ data }) => {
+      return data.body;
+    });
+};
+
+const setupDomElement = ({ injectToEl = null } = {}) => {
+  const previewEl = document.createElement('div');
+  previewEl.classList.add(EXTENSION_MARKDOWN_PREVIEW_PANEL_CLASS);
+  previewEl.style.display = 'none';
+  if (injectToEl) {
+    injectToEl.appendChild(previewEl);
+  }
+  return previewEl;
+};
+
 export class EditorMarkdownExtension extends SourceEditorExtension {
+  constructor({ instance, projectPath, ...args } = {}) {
+    super({ instance, ...args });
+    Object.assign(instance, {
+      projectPath,
+      preview: {
+        el: undefined,
+        action: undefined,
+        shown: false,
+        modelChangeListener: undefined,
+      },
+    });
+    this.setupPreviewAction.call(instance);
+
+    instance.getModel().onDidChangeLanguage(({ newLanguage, oldLanguage } = {}) => {
+      if (newLanguage === 'markdown' && oldLanguage !== newLanguage) {
+        instance.setupPreviewAction();
+      } else {
+        instance.cleanup();
+      }
+    });
+
+    instance.onDidChangeModel(() => {
+      const model = instance.getModel();
+      if (model) {
+        const { language } = model.getLanguageIdentifier();
+        instance.cleanup();
+        if (language === 'markdown') {
+          instance.setupPreviewAction();
+        }
+      }
+    });
+  }
+
+  static togglePreviewLayout() {
+    const { width, height } = this.getLayoutInfo();
+    const newWidth = this.preview.shown
+      ? width / EXTENSION_MARKDOWN_PREVIEW_PANEL_WIDTH
+      : width * EXTENSION_MARKDOWN_PREVIEW_PANEL_WIDTH;
+    this.layout({ width: newWidth, height });
+  }
+
+  static togglePreviewPanel() {
+    const parentEl = this.getDomNode().parentElement;
+    const { el: previewEl } = this.preview;
+    parentEl.classList.toggle(EXTENSION_MARKDOWN_PREVIEW_PANEL_PARENT_CLASS);
+
+    if (previewEl.style.display === 'none') {
+      // Show the preview panel
+      this.fetchPreview();
+    } else {
+      // Hide the preview panel
+      previewEl.style.display = 'none';
+    }
+  }
+
+  cleanup() {
+    if (this.preview.modelChangeListener) {
+      this.preview.modelChangeListener.dispose();
+    }
+    this.preview.action.dispose();
+    if (this.preview.shown) {
+      EditorMarkdownExtension.togglePreviewPanel.call(this);
+      EditorMarkdownExtension.togglePreviewLayout.call(this);
+    }
+    this.preview.shown = false;
+  }
+
+  fetchPreview() {
+    const { el: previewEl } = this.preview;
+    getPreview(this.getValue(), this.projectPath)
+      .then((data) => {
+        previewEl.innerHTML = sanitize(data);
+        syntaxHighlight(previewEl.querySelectorAll('.js-syntax-highlight'));
+        previewEl.style.display = 'block';
+      })
+      .catch(() => createFlash(BLOB_PREVIEW_ERROR));
+  }
+
+  setupPreviewAction() {
+    if (this.getAction(EXTENSION_MARKDOWN_PREVIEW_ACTION_ID)) return;
+
+    this.preview.action = this.addAction({
+      id: EXTENSION_MARKDOWN_PREVIEW_ACTION_ID,
+      label: __('Preview Markdown'),
+      keybindings: [
+        // eslint-disable-next-line no-bitwise,no-undef
+        monaco.KeyMod.chord(monaco.KeyMod.CtrlCmd | monaco.KeyMod.Shift | monaco.KeyCode.KEY_P),
+      ],
+      contextMenuGroupId: 'navigation',
+      contextMenuOrder: 1.5,
+
+      // Method that will be executed when the action is triggered.
+      // @param ed The editor instance is passed in as a convenience
+      run(instance) {
+        instance.togglePreview();
+      },
+    });
+  }
+
+  togglePreview() {
+    if (!this.preview?.el) {
+      this.preview.el = setupDomElement({ injectToEl: this.getDomNode().parentElement });
+    }
+    EditorMarkdownExtension.togglePreviewLayout.call(this);
+    EditorMarkdownExtension.togglePreviewPanel.call(this);
+
+    if (!this.preview?.shown) {
+      this.preview.modelChangeListener = this.onDidChangeModelContent(
+        debounce(this.fetchPreview.bind(this), EXTENSION_MARKDOWN_PREVIEW_UPDATE_DELAY),
+      );
+    } else {
+      this.preview.modelChangeListener.dispose();
+    }
+
+    this.preview.shown = !this.preview?.shown;
+  }
+
   getSelectedText(selection = this.getSelection()) {
     const { startLineNumber, endLineNumber, startColumn, endColumn } = selection;
     const valArray = this.getValue().split('\n');