OPC UA Client Proxy for Node.js

import { OPCUAClient, MessageSecurityMode, SecurityPolicy, ClientSession, TimestampsToReturn, AttributeIds } from 'node-opcua';
import { ClientProxy } from 'node-opcua-client-proxy';

const endpointUrl = process.env.OPCUA_ENDPOINT_URL ?? 'opc.tcp://localhost:4840';
const userIdentity = {
    userName: process.env.OPCUA_USERNAME ?? 'user',
    password: process.env.OPCUA_PASSWORD ?? 'password'
};

async function connectAndRead() {
    const client = OPCUAClient.create({
        endpointUrl: endpointUrl,
        securityMode: MessageSecurityMode.None, // For demo purposes, consider stronger security in production
        securityPolicy: SecurityPolicy.None,
        // clientCertificateManager: provide a proper cert manager in production
        connectionStrategy: { maxRetry: 5, initialDelay: 500, maxDelay: 3000 }
    });

    client.on('backoff', (retry, delay) => {
        console.log(`Connection attempt failed. Retrying in ${delay / 1000}s (attempt ${retry})`);
    });

    let session: ClientSession | null = null;

    try {
        console.log(`Connecting to ${endpointUrl}...`);
        await client.connect(endpointUrl);
        console.log('Connected to OPC UA server.');

        session = await client.createSession(userIdentity);
        console.log(`Session created with id: ${session.sessionId.toString()}`);

        // Instantiate the ClientProxy with the established session
        const proxy = new ClientProxy(session); 

        // Example: Reading a specific node's value via the proxy (assuming proxy has a 'read' method)
        const nodeIdToRead = 'ns=2;s=MyDevice/Temperature'; // Replace with a valid NodeId from your server
        console.log(`Attempting to read NodeId: ${nodeIdToRead}`);

        // Using session.read directly for now as proxy API is inferred
        const dataValue = await session.read({
            nodeId: nodeIdToRead,
            attributeId: AttributeIds.Value,
            timestampsToReturn: TimestampsToReturn.Both
        });

        if (dataValue.statusCode.isGood()) {
            console.log(`Value of ${nodeIdToRead}: ${dataValue.value?.value} (Source Timestamp: ${dataValue.sourceTimestamp?.toISOString()})`);
        } else {
            console.error(`Failed to read ${nodeIdToRead}: ${dataValue.statusCode.toString()}`);
        }

    } catch (err) {
        console.error('An error occurred during OPC UA communication:', err);
    } finally {
        if (session) {
            await session.close();
            console.log('Session closed.');
        }
        if (client) {
            await client.disconnect();
            console.log('Disconnected from OPC UA server.');
        }
    }
}

connectAndRead();