sqmicro-connection/test/streams.test.js

Connection abstraction for SQ Micro.

const { Transform, Writable } = require('stream');
const toJSON = require('./to-json');

const events = 'close data drain end error finish readable pipe unpipe'.split(' ');

const MAX_LEN = 128;
class S extends Transform {
    get name() { return this._A; }
    constructor(name) {
        super({ objectMode: true });
        this._A = name || 'S';
        
        bindEvents(this, events, this.name);
    }
    
    _transform(chunk, encoding, done) {
        console.log(`${this.name}: ${JSON.stringify(chunk)}`);
        this.push(chunk);
        done();
    }
}

class W extends Writable {
    get name() { return this._A; }
    constructor(name) {
        super({ objectMode: true });
        this._A = name || 'W';
        
        bindEvents(this, events, this.name);
    }
    
    _write(chunk, encoding, done) {
        console.log(`${this.name}: ${JSON.stringify(chunk)}`);
        done();
    }
}

const a = new S('a');
const b = new S('b');
const w = new S('w');

a.pipe(b).pipe(w);

a.write({an: 'object', n: 1});
a.write({an: 'object', n: 2});
a.write({an: 'object', n: 3});
a.end();

function bindEvents(target, events, name) {
    events.forEach(e => {
        target.on(e, a => console.log(`${name}: ♮ ${e}(${stringify(a)})`));
    });
}

function stringify(o) {
    if (o === undefined) return;
    if (o.name) return o.name;
    let s = toJSON(o, 0);
    if (s.length > MAX_LEN) {
        s = s.substr(0, MAX_LEN - 1) + '…';
    }
    return s;
}