stream-flow-control/lib/flows/join.js

Stream Flow Control

const {Readable} = require('stream');
const {Manager} = require('../manager/manager.js');
const uuid = require('uuid');
const {DataWrapper} = require('../wrapper/data_wrapper.js')

/**
 * Join messages from multiple sources into a single messages. If no method is overwitten, then releases a message when there is exactly one message from each source.
 * 
 * @extends Readable
 */
class FlowJoin extends Readable {

    /** 
     * Create a FlowJoin stream
     * @param {object} options Global options.
     * @param {string} [options.name] Name for this stream.
     * @param {Process} [options.join] How messages are joined.
    */
    constructor(options) {
        options = {...options, objectMode: true};
        super(options);
        this.options = options;
        this._sources = {};
        this._payloads = [];
        this._readableState.sync = false;
        this.type = 'FlowJoin';
        if(this.options.name) Manager.set(this.type, this);
        if(this.options.join && typeof this.options.join == 'function') this._join = this.options.join;

        this.on('pipe', (src)=>{
            const id = this.goal || (src.options && src.options.name)?src.options.name:uuid.v4();
            if(src.options && src.options.port) {
                id += '/'+src.options.port;
            }
            this._sources[id] = src;
            src.on('data', (data)=>{
                //console.log('hay data');
                this._join({
                    id,
                    data
                });
            });
            //src.on('end', () => this.end(src));

            this.on('pause', ()=>{
                src.pause();
            });
            this.on('resume', ()=>{
                src.resume();
            });
        });
    }

    // none(dst) {
    //     if(!this._none_reader) {
    //         this._none_reader = new Readable({
    //             objectMode: true,
    //             read() {}
    //         });
    //         this._none_reader._readableState.sync = false;
    //     }

    //     const pipes = Array.isArray(dst)?dst:[dst];
    //     pipes.forEach(dst=>this._none_reader.pipe(dst));
    //     return Array.isArray(dst)?this:dst;
    // }

    _join(data) {
        var found = false;
        var doSend = false;
        
        for(let i = 0; i < this._payloads.length; i++) {
            let payload = this._payloads[i];
            if(payload.hasOwnProperty(data.id)) continue;
            found=true;
            payload[data.id] = data.data;
            doSend = Object.keys(payload).length == Object.keys(this._sources).length;
            break;
        }
        if(doSend) {
            let payload = this._payloads.shift();
            
            if(this.goal) {
                // Is goal player
                payload = new DataWrapper(null, this).setParents(payload);
            } 
            if(!this.push(payload)) this.pause();
            return;
        }
        if(!found) {
            let payload = {};
            payload[data.id] = data.data;
            this._payloads.push(payload);
        }
    }

    _read() {
        this.resume();
    }

    write(payload) {

    }

    end(src) {
        for(let i in this._sources) {
            if(!this._sources[i]._readableState.ended) return;
        }
        this.push(null);
    }

}

module.exports.FlowJoin = FlowJoin;