sqmicro-connection/test/fake-driver.js

Connection abstraction for SQ Micro.

const EventEmitter = require('events');
const util = require('util');
const { Writable } = require('stream');

const wait = util.promisify(setTimeout);

const { promisifyEventEmitter } = require('sqmicro-commons');

const Private = Symbol('Private');

const CONNECTION_STABLE_TIME = 35000; // ms
const NETWORK_LATENCY = 500; // ms

class Sink extends Writable {
    _write(chunk, encoding, cb) {
        console.log(`Wrote[${encoding}] ${chunk}`);
        cb();
    }
}

module.exports = class FakeDriver extends EventEmitter {
    get driverName() { return 'FakeDriver'; }
    get isConnected() { return this[Private].isConnected; }

    constructor(config) {
        super();
        
        const pvt = this[Private] = {
            config,
            isConnected: false,
        };

        this._simulateNetworkProblems();
    }
    
    async connect() {
        const pvt = this[Private];
        
        pvt.isConnected = false;
        
        await wait(NETWORK_LATENCY);

        if (pvt.tries > 0) {
            pvt.tries--;
            throw Error(`EConnectionError ;-(`);
        }
     
        pvt.isConnected = true;
        
        this.emit('connected');
        
        return this;
    }

    async getCopyStream(dest, options) {
        return new Sink();
    }

    async disconnect() {
        const pvt = this[Private];
        await wait(NETWORK_LATENCY);
        pvt.isConnected = false;
        return this;
    }
    
    async query() {
        await wait(NETWORK_LATENCY);
        return { a: 'result' };
    }

    _simulateNetworkProblems() {
        const pvt = this[Private];
        if (pvt.config.stableNetwork) {
            pvt.tries = 0;
            return;
        }
        
        pvt.tries = Math.floor(1 + 3 * Math.random());
        console.log(`\n============[ Disconnected back end simulation for the following ${pvt.tries} attempts]===============\n`);

        wait(CONNECTION_STABLE_TIME).then(() => {
            this._simulateNetworkProblems();
            this.emit('error', Error(`Connection was closed ;-(`));
            this.emit('disconnected');
        });

    }
};