/**

• tallbag-combine

• ---

• Tallbag factory that combines the latest data points from multiple (2 or
• more) tallbag sources. It delivers those latest values as an array. Works
• with both pullable and listenable sources.
• npm install tallbag-combine
• Example:

• const interval = require('callbag-interval');

• const observe = require('callbag-observe');

• const combine = require('tallbag-combine');

• const source = combine(interval(100), interval(350));

• observe(x => console.log(x))(source); // [2,0]

•                                       // [3,0]

•                                       // [4,0]

•                                       // [5,0]

•                                       // [6,0]

•                                       // [6,1]

•                                       // [7,1]

•                                       // [8,1]

•                                       // ...

*/

const makeShadow = require('shadow-callbag').default;

const EMPTY = {};

const combine = (...sources) => (start, sink) => { if (start !== 0) return; const n = sources.length; if (n === 0) { sink(0, () => {}, makeShadow('combine')); sink(1, []); sink(2); return; } let Ns = n; // start counter let Nd = n; // data counter let Ne = n; // end counter let shadow; const sourceTalkbacks = new Array(n); const sourceShadows = new Array(n); const vals = new Array(n); const talkback = (t, d) => { if (t === 0) return; for (let i = 0; i < n; i++) { sourceTalkbacks[i](t, d); t === 2 && sourceShadows[i] && sourceShadowsi; } }; sources.forEach((source, i) => { vals[i] = EMPTY; source(0, (t, d, s) => { if (t === 0) { sourceTalkbacks[i] = d; sourceShadows[i] = s; if (--Ns === 0) { shadow = makeShadow('combine', sourceShadows); sink(0, talkback, shadow); } } else if (t === 1) { const _Nd = !Nd ? 0 : vals[i] === EMPTY ? --Nd : Nd; vals[i] = d; if (_Nd === 0) { const arr = new Array(n); for (let j = 0; j < n; ++j) arr[j] = vals[j]; shadow(1, arr); sink(1, arr); } } else if (t === 2) { if (--Ne === 0) sink(2); } else { sink(t, d); } }); }); };

module.exports = combine;