ObsiGate/frontend/js/excalidraw-viewer.js

/**
 * Excalidraw Viewer — iframe-based diagram editor integration for ObsiGate.
 *
 * Renders .excalidraw files in an iframe that loads the standalone
 * excalidraw-editor.html. Communication between parent and iframe
 * via postMessage:
 *
 *   Parent → Iframe:  init {data, theme}  |  theme {theme}  |  requestSave
 *   Iframe → Parent:  ready  |  save {data}  |  modified {dirty}
 */

import { api } from './auth.js';
import { showToast } from './ui.js';

// Track active Excalidraw iframes by a unique id
const _activeEditors = new Map();
let _editorIdCounter = 0;

/**
 * Render an Excalidraw editor inside the given container element.
 *
 * @param {HTMLElement} container - DOM element to host the iframe (usually content-area)
 * @param {object} data - File data from /api/file/{vault} (must have is_excalidraw: true)
 * @param {string} vaultName
 * @param {string} filePath
 * @param {object} [opts]
 * @param {boolean} [opts.readOnly=false] - If true, hide save button in iframe
 */
export function renderExcalidraw(container, data, vaultName, filePath, opts = {}) {
  const editorId = `excalidraw-${++_editorIdCounter}`;

  // Build the iframe
  const iframe = document.createElement('iframe');
  iframe.id = editorId;
  iframe.src = '/static/excalidraw-editor.html?v=' + Date.now();
  iframe.sandbox.add('allow-scripts');
  iframe.sandbox.add('allow-same-origin');
  iframe.style.cssText = 'width:100%;height:100%;border:none;';

  // Clean container and insert iframe
  container.innerHTML = '';
  container.appendChild(iframe);

  // Track this editor instance
  const editorState = {
    id: editorId,
    iframe,
    vault: vaultName,
    path: filePath,
    isDirty: false,
    ready: false,
    saveTimer: null,
  };
  _activeEditors.set(editorId, editorState);

  // Get current theme
  const theme = document.documentElement.getAttribute('data-theme') || 'dark';

  // Wait for iframe to load, then send init
  iframe.addEventListener('load', () => {
    // Send init message when iframe sends 'ready'
    // (iframe may load before React mounts, so we wait for the ready signal)
    // We set up the message listener before sending anything
  });

  // Handle messages from iframe
  window.addEventListener('message', (event) => {
    // Verify source is our iframe
    if (event.source !== iframe.contentWindow) return;

    const msg = event.data;
    if (!msg || typeof msg.type !== 'string') return;

    switch (msg.type) {
      case 'ready':
        // Iframe is mounted — send initial data
        editorState.ready = true;
        // Support both pure .excalidraw and compressed .excalidraw.md
        const initData = data.excalidraw_data || {};
        if (data.excalidraw_data_compressed) {
          initData.compressed = data.excalidraw_data_compressed;
        }
        iframe.contentWindow.postMessage({
          type: 'init',
          data: initData,
          theme: theme,
        }, '*');
        break;

      case 'save':
        if (msg.data) {
          _saveExcalidrawFile(editorState, msg.data);
        }
        break;

      case 'modified':
        editorState.isDirty = msg.dirty === true;
        // If dirty, start auto-save timer (2s debounce)
        if (editorState.isDirty) {
          if (editorState.saveTimer) clearTimeout(editorState.saveTimer);
          editorState.saveTimer = setTimeout(() => {
            if (editorState.isDirty && editorState.ready) {
              iframe.contentWindow.postMessage({ type: 'requestSave' }, '*');
            }
          }, 2000);
        }
        break;
    }
  });
}

/**
 * Save Excalidraw data back to the server.
 */
async function _saveExcalidrawFile(state, excalidrawData) {
  try {
    const isMd = (state.path || '').toLowerCase().endsWith('.excalidraw.md');
    let content;
    if (isMd && excalidrawData && excalidrawData.compressed) {
      // Preserve the Obsidian Excalidraw plugin format: frontmatter +
      // compressed-json block. Writing raw JSON here would destroy the
      // .excalidraw.md file (the plugin would no longer recognize it).
      content = `---\nexcalidraw-plugin: parsed\n---\n\n\`\`\`compressed-json\n${excalidrawData.compressed}\n\`\`\`\n`;
    } else {
      // Transport-only field must not leak into the pure JSON format.
      const { compressed, ...scene } = excalidrawData || {};
      content = JSON.stringify(scene, null, 2);
    }
    await api(`/api/file/${encodeURIComponent(state.vault)}/save?path=${encodeURIComponent(state.path)}&backup=false`, {
      method: 'PUT',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ content }),
    });
    // Toast is handled by the caller or we show a quick one
    showToast('Excalidraw saved', 'success');
  } catch (err) {
    console.error('[Excalidraw] Save failed:', err);
    showToast('Failed to save Excalidraw: ' + (err.message || 'unknown error'), 'error');
  }
}

/**
 * Notify all active Excalidraw editors of a theme change.
 */
export function notifyExcalidrawThemeChange(theme) {
  _activeEditors.forEach((state) => {
    if (state.ready && state.iframe.contentWindow) {
      state.iframe.contentWindow.postMessage({ type: 'theme', theme }, '*');
    }
  });
}

/**
 * Clean up an editor instance (e.g., when tab is closed).
 */
export function destroyExcalidrawEditor(editorId) {
  const state = _activeEditors.get(editorId);
  if (state) {
    if (state.saveTimer) clearTimeout(state.saveTimer);
    _activeEditors.delete(editorId);
  }
}

export default { renderExcalidraw, notifyExcalidrawThemeChange, destroyExcalidrawEditor };