Data Sync using Sync Gateway

const replicatorConfig = {
    database: database,
    url: 'wss://sync-gateway.example.com:4984/myapp', (1)
    collections: {
        tasks: { pull: {}, push: {} }
    }
};

// Configure bi-directional continuous replication
const bidirectionalConfig = {
    database: database,
    url: 'wss://sync-gateway.example.com:4984/myapp',
    collections: {
        tasks: {
            pull: {}, // Pull changes from server
            push: {}  // Push changes to server
        }
    }
};

// Configure pull-only replication
const pullOnlyConfig = {
    database: database,
    url: 'wss://sync-gateway.example.com:4984/myapp',
    collections: {
        tasks: {
            pull: {} // Only pull, no push
        }
    }
};

// Configure push-only replication
const pushOnlyConfig = {
    database: database,
    url: 'wss://sync-gateway.example.com:4984/myapp',
    collections: {
        tasks: {
            push: {} // Only push, no pull
        }
    }
};

{
  "name": "alice",
  "password": "secret123"
}

const replicator = new Replicator({
  database: database,
  url: 'wss://sync-gateway.example.com:4984/myapp',
  collections: {
    tasks: { pull: {}, push: {} }
  },
  credentials: {
    username: 'alice',
    password: 'secret123'
  },
  continuous: true
});

await replicator.start();

// Create replicator
const replicator = new Replicator(replicatorConfig); (1)

// Start replication
await replicator.run(); (2)
console.log('Replication started');

// Monitor replication status
replicator.onStatusChange = (status) => {
    console.log('Replication status:', status.status);

    // Check progress
    if (status.pulledRevisions !== undefined) {
        console.log('Documents pulled:', status.pulledRevisions);
    }

    if (status.pushedRevisions !== undefined) {
        console.log('Documents pushed:', status.pushedRevisions);
    }

    // Handle errors
    if (status.error) {
        console.error('Replication error:', status.error);

        // Check if it's a recoverable error
        if (status.status === 'offline') {
            console.log('Replicator is offline, will retry...');
        } else if (status.status === 'stopped') {
            console.log('Replicator stopped due to error');
        }
    }

    // Handle different states
    switch (status.status) {
        case 'connecting':
            console.log('Connecting to server...');
            break;
        case 'busy':
            console.log('Actively transferring data');
            break;
        case 'idle':
            console.log('Caught up with server');
            break;
        case 'stopped':
            console.log('Replication stopped');
            break;
    }
};

// Monitor individual document replication
replicator.onDocuments = (collection, direction, documents) => {
    console.log(`${direction} - ${documents.length} documents in ${collection.name}`);

    for (const doc of documents) {
        if (doc.error) {
            console.error(`Error ${direction}ing ${doc.id}:`, doc.error);
        } else if (doc.flags?.deleted) {
            console.log(`Document ${doc.id} was deleted`);
        } else {
            console.log(`Document ${doc.id} ${direction}ed successfully`);
        }
    }
};

// Check if there are documents waiting to be pushed
const tasksCollection = await database.collection('tasks');

// Get pending document IDs for the collection
const pendingDocs = await replicator.getPendingDocumentIDs(tasksCollection);

if (pendingDocs.length > 0) {
    console.log(`${pendingDocs.length} documents pending push`);
    console.log('Pending document IDs:', pendingDocs);
} else {
    console.log('No documents pending push');
}

// Check if a specific document is pending
const docId = 'task-123';
const isPending = await replicator.isDocumentPending(tasksCollection, docId);
console.log(`Document ${docId} is ${isPending ? 'pending' : 'not pending'}`);