Building a Collaborative Editor

Overview

This advanced example demonstrates building a production-ready collaborative editor with:

Real-time typing sync across all peers
Remote cursor positions and selections
Markdown/HTML split preview with draggable splitter
Version history with restore functionality
File sharing via P2P
Integrated video room for face-to-face collaboration
RBAC + WebAuthn for secure authentication
Rich text toolbar with formatting options

View the live demo to see all features in action.

Architecture Overview

The collaborative editor combines multiple GenosDB features:

Core Concepts

1. Document Synchronization

The editor uses a single document node that all peers subscribe to:

const DOCUMENT_ID = 'doc:main'

// Subscribe to document changes
await db.get(
  DOCUMENT_ID,
  (doc) => {
    if (doc && doc.value.content !== editor.value) {
      // Update local editor if remote change
      editor.value = doc.value.content
    }
  }
)

// Save changes on input (debounced)
let saveTimeout
editor.addEventListener('input', () => {
  clearTimeout(saveTimeout)
  saveTimeout = setTimeout(async () => {
    await db.put({
      content: editor.value,
      updatedAt: Date.now(),
      updatedBy: currentUser
    }, DOCUMENT_ID)
  }, 300)  // 300ms debounce
})

Conflict Resolution: GenosDB uses Last-Write-Wins (LWW). For high-frequency concurrent edits, consider operational transformation (OT) or CRDTs for character-level merging.

2. Remote Cursor Positions

Cursors use data channels for ephemeral updates:

const cursorChannel = db.room.channel('cursors')
const remoteCursors = new Map()

// Send cursor position
editor.addEventListener('selectionchange', () => {
  const { selectionStart, selectionEnd } = editor
  cursorChannel.send({
    username: currentUser,
    start: selectionStart,
    end: selectionEnd
  })
})

// Receive remote cursors
cursorChannel.on('message', ({ username, start, end }, peerId) => {
  updateCursorDisplay(peerId, username, start, end)
})

3. Version History

Save snapshots with timestamps:

const versions = []

async function saveVersion() {
  const versionId = await db.put({
    type: 'version',
    content: editor.value,
    timestamp: Date.now(),
    author: currentUser
  })
  
  versions.unshift({
    id: versionId,
    timestamp: Date.now(),
    preview: editor.value.slice(0, 100)
  })
  
  updateVersionList()
}

async function restoreVersion(versionId) {
  const { result: version } = await db.get(versionId)
  if (!version) return
  
  editor.value = version.value.content
  await db.put({
    content: version.value.content,
    updatedAt: Date.now(),
    updatedBy: currentUser
  }, DOCUMENT_ID)
}

4. Video Integration

Add video chat alongside the editor:

const videoContainer = document.getElementById('videos')
const peerVideos = new Map()

// Start local video
async function startVideo() {
  const stream = await navigator.mediaDevices.getUserMedia({
    video: true,
    audio: true
  })
  
  // Display local video
  const localVideo = document.createElement('video')
  localVideo.srcObject = stream
  localVideo.autoplay = true
  localVideo.muted = true  // Mute own audio
  videoContainer.appendChild(localVideo)
  
  // Broadcast to peers
  db.room.addStream(stream)
}

// Receive remote videos
db.room.on('stream:add', (stream, peerId) => {
  const video = document.createElement('video')
  video.srcObject = stream
  video.autoplay = true
  video.playsInline = true
  video.dataset.peer = peerId
  videoContainer.appendChild(video)
  peerVideos.set(peerId, video)
})

db.room.on('peer:leave', (peerId) => {
  const video = peerVideos.get(peerId)
  if (video) {
    video.remove()
    peerVideos.delete(peerId)
  }
})

Complete Implementation

Here’s a simplified but complete collaborative editor:

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Collaborative Editor</title>
  <style>
    * {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
    }
    
    body {
      font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
      display: flex;
      flex-direction: column;
      height: 100vh;
      background: #0b1220;
      color: #e5e7eb;
    }
    
    header {
      background: #1a1a1a;
      padding: 1rem;
      border-bottom: 1px solid #333;
    }
    
    #toolbar {
      background: #1a1a1a;
      padding: 0.5rem;
      display: flex;
      gap: 0.5rem;
      border-bottom: 1px solid #333;
    }
    
    button {
      padding: 0.5rem 1rem;
      background: #0ea5e9;
      border: none;
      color: white;
      border-radius: 4px;
      cursor: pointer;
    }
    
    button:hover {
      background: #0284c7;
    }
    
    #editor-container {
      flex: 1;
      display: flex;
      overflow: hidden;
    }
    
    #editor {
      flex: 1;
      padding: 1rem;
      background: #1e293b;
      color: #e5e7eb;
      border: none;
      font-family: 'Monaco', 'Courier New', monospace;
      font-size: 14px;
      line-height: 1.6;
      resize: none;
    }
    
    #editor:focus {
      outline: none;
    }
    
    #preview {
      flex: 1;
      padding: 1rem;
      background: #0f172a;
      overflow-y: auto;
      border-left: 1px solid #333;
    }
    
    #videos {
      position: fixed;
      bottom: 20px;
      right: 20px;
      display: flex;
      gap: 10px;
      z-index: 1000;
    }
    
    #videos video {
      width: 200px;
      height: 150px;
      border-radius: 8px;
      border: 2px solid #0ea5e9;
    }
    
    .cursor-overlay {
      position: absolute;
      width: 2px;
      background: var(--cursor-color);
      pointer-events: none;
      z-index: 10;
    }
    
    .cursor-label {
      position: absolute;
      background: var(--cursor-color);
      color: white;
      padding: 2px 6px;
      border-radius: 3px;
      font-size: 12px;
      white-space: nowrap;
    }
  </style>
</head>
<body>
  <header>
    <h1>Collaborative Editor</h1>
  </header>
  
  <div id="toolbar">
    <button onclick="saveVersion()">Save Version</button>
    <button onclick="togglePreview()">Toggle Preview</button>
    <button onclick="startVideo()">Start Video</button>
    <button onclick="shareFile()">Share File</button>
  </div>
  
  <div id="editor-container">
    <textarea id="editor" placeholder="Start typing..."></textarea>
    <div id="preview" style="display: none;"></div>
  </div>
  
  <div id="videos"></div>
  
  <script type="module">
    import { gdb } from 'https://cdn.jsdelivr.net/npm/genosdb@latest/dist/index.min.js'
    import { marked } from 'https://cdn.jsdelivr.net/npm/marked@latest/lib/marked.esm.js'
    
    const DOCUMENT_ID = 'doc:main'
    const editor = document.getElementById('editor')
    const preview = document.getElementById('preview')
    const videoContainer = document.getElementById('videos')
    
    let currentUser = localStorage.getItem('username') || prompt('Enter your name:')
    localStorage.setItem('username', currentUser)
    
    // Initialize GenosDB
    const db = await gdb('collab-editor', { rtc: true })
    
    // === Document Synchronization ===
    
    let isRemoteUpdate = false
    
    await db.get(DOCUMENT_ID, (doc) => {
      if (doc && doc.value.content !== editor.value) {
        isRemoteUpdate = true
        editor.value = doc.value.content
        updatePreview()
      }
    })
    
    let saveTimeout
    editor.addEventListener('input', () => {
      updatePreview()
      
      if (isRemoteUpdate) {
        isRemoteUpdate = false
        return
      }
      
      clearTimeout(saveTimeout)
      saveTimeout = setTimeout(async () => {
        await db.put({
          content: editor.value,
          updatedAt: Date.now(),
          updatedBy: currentUser
        }, DOCUMENT_ID)
      }, 300)
    })
    
    // === Preview ===
    
    function updatePreview() {
      preview.innerHTML = marked(editor.value)
    }
    
    window.togglePreview = function() {
      const isVisible = preview.style.display !== 'none'
      preview.style.display = isVisible ? 'none' : 'block'
    }
    
    // === Remote Cursors ===
    
    const cursorChannel = db.room.channel('cursors')
    const remoteCursors = new Map()
    const colors = ['#ef4444', '#3b82f6', '#10b981', '#f59e0b', '#8b5cf6']
    let colorIndex = 0
    
    editor.addEventListener('click', sendCursorPosition)
    editor.addEventListener('keyup', sendCursorPosition)
    
    function sendCursorPosition() {
      cursorChannel.send({
        username: currentUser,
        position: editor.selectionStart
      })
    }
    
    cursorChannel.on('message', ({ username, position }, peerId) => {
      if (!remoteCursors.has(peerId)) {
        remoteCursors.set(peerId, {
          username,
          color: colors[colorIndex++ % colors.length]
        })
      }
      // In production, calculate pixel position and display cursor
    })
    
    // === Video Chat ===
    
    const peerVideos = new Map()
    
    window.startVideo = async function() {
      try {
        const stream = await navigator.mediaDevices.getUserMedia({
          video: true,
          audio: true
        })
        
        const localVideo = document.createElement('video')
        localVideo.srcObject = stream
        localVideo.autoplay = true
        localVideo.muted = true
        localVideo.playsInline = true
        videoContainer.appendChild(localVideo)
        
        db.room.addStream(stream)
      } catch (err) {
        alert('Camera access denied: ' + err.message)
      }
    }
    
    db.room.on('stream:add', (stream, peerId) => {
      const video = document.createElement('video')
      video.srcObject = stream
      video.autoplay = true
      video.playsInline = true
      video.dataset.peer = peerId
      videoContainer.appendChild(video)
      peerVideos.set(peerId, video)
    })
    
    db.room.on('peer:leave', (peerId) => {
      const video = peerVideos.get(peerId)
      if (video) {
        video.remove()
        peerVideos.delete(peerId)
      }
    })
    
    // === Version History ===
    
    window.saveVersion = async function() {
      const versionId = await db.put({
        type: 'version',
        content: editor.value,
        timestamp: Date.now(),
        author: currentUser
      })
      alert('Version saved!')
    }
    
    // === File Sharing ===
    
    const fileChannel = db.room.channel('files')
    
    window.shareFile = async function() {
      const input = document.createElement('input')
      input.type = 'file'
      input.onchange = async (e) => {
        const file = e.target.files[0]
        if (!file) return
        
        const buffer = await file.arrayBuffer()
        fileChannel.send({
          name: file.name,
          type: file.type,
          data: buffer
        })
        alert('File shared!')
      }
      input.click()
    }
    
    fileChannel.on('message', ({ name, type, data }) => {
      const blob = new Blob([data], { type })
      const url = URL.createObjectURL(blob)
      const a = document.createElement('a')
      a.href = url
      a.download = name
      a.click()
      URL.revokeObjectURL(url)
      alert(`Received file: ${name}`)
    })
  </script>
</body>
</html>

Advanced Features

Security with WebAuthn

const db = await gdb('secure-editor', {
  rtc: true,
  sm: {
    superAdmins: ['0x1234...'],
    customRoles: {
      editor: { can: ['write'], inherits: ['guest'] },
      viewer: { can: ['read'], inherits: ['guest'] }
    }
  }
})

// Require login
await db.sm.loginCurrentUserWithWebAuthn()

// Only editors can save
if (await db.sm.executeWithPermission('write')) {
  await db.put({ content: editor.value }, DOCUMENT_ID)
}

Presence Indicators

const presenceChannel = db.room.channel('presence')
const onlineUsers = new Set()

// Broadcast presence
setInterval(() => {
  presenceChannel.send({ username: currentUser, active: true })
}, 3000)

// Track users
presenceChannel.on('message', ({ username }, peerId) => {
  onlineUsers.add(username)
  updateUserList()
})

db.room.on('peer:leave', (peerId) => {
  // Remove user from list
})

Conflict Indicators

Show when multiple users edit simultaneously:

let lastRemoteUpdate = 0

await db.get(DOCUMENT_ID, (doc) => {
  if (doc) {
    const timeSinceEdit = Date.now() - lastRemoteUpdate
    if (timeSinceEdit < 2000 && doc.value.updatedBy !== currentUser) {
      showConflictWarning(doc.value.updatedBy)
    }
    lastRemoteUpdate = Date.now()
  }
})

Key Learnings

Debounce Saves

Use setTimeout to batch rapid keystrokes into single database writes.

Data Channels for Ephemeral

Cursor positions don’t need persistence. Use channels instead of put().

Version Snapshots

Periodic snapshots enable time travel and conflict recovery.

LWW Limitations

Last-Write-Wins can lose concurrent edits. Consider OT/CRDTs for character-level sync.

Performance Optimization

Chunked Documents

For large documents, split into chunks:

// Split into paragraphs
const paragraphs = editor.value.split('\n\n')

for (let i = 0; i < paragraphs.length; i++) {
  await db.put({
    type: 'paragraph',
    docId: DOCUMENT_ID,
    index: i,
    content: paragraphs[i]
  }, `${DOCUMENT_ID}:p${i}`)
}

Lazy Loading

Load version history on demand:

async function loadVersionHistory() {
  const { results } = await db.map({
    query: { type: 'version' },
    field: 'timestamp',
    order: 'desc',
    $limit: 20  // Last 20 versions
  })
  displayVersions(results)
}

Next Steps

Security Model

Add RBAC and WebAuthn authentication

P2P Setup

Configure for production with TURN servers

Real-Time Subscriptions

Master reactive patterns

Examples Overview

Explore more GenosDB examples

Get Started

Core Concepts

Guides

Examples

Building a Collaborative Editor

Overview

Architecture Overview

Core Concepts

1. Document Synchronization

2. Remote Cursor Positions

3. Version History

4. Video Integration

Complete Implementation

Advanced Features

Security with WebAuthn

Presence Indicators

Conflict Indicators

Key Learnings

Debounce Saves

Data Channels for Ephemeral

Version Snapshots

LWW Limitations

Performance Optimization

Chunked Documents

Lazy Loading

Next Steps

Security Model

P2P Setup

Real-Time Subscriptions

Examples Overview

Build docs developers (and LLMs) love

Get Started

Core Concepts

Guides

Examples

​Overview

​Architecture Overview

​Core Concepts

​1. Document Synchronization

​2. Remote Cursor Positions

​3. Version History

​4. Video Integration

​Complete Implementation

​Advanced Features

​Security with WebAuthn

​Presence Indicators

​Conflict Indicators

​Key Learnings

Debounce Saves

Data Channels for Ephemeral

Version Snapshots

LWW Limitations

​Performance Optimization

​Chunked Documents

​Lazy Loading

​Next Steps

Security Model

P2P Setup

Real-Time Subscriptions

Examples Overview

Build docs developers (and LLMs) love

Overview

Architecture Overview

Core Concepts

1. Document Synchronization

2. Remote Cursor Positions

3. Version History

4. Video Integration

Complete Implementation

Advanced Features

Security with WebAuthn

Presence Indicators

Conflict Indicators

Key Learnings

Performance Optimization

Chunked Documents

Lazy Loading

Next Steps