'use strict';

/**

• callbag-merge

• ---

• Callbag factory that merges data from multiple callbag sources. Works well
• with listenable sources, and while it may work for some pullable sources,
• it is only designed for listenable sources.
• npm install callbag-merge
• Example:

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

• const forEach = require('callbag-for-each');

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

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

• forEach(x => console.log(x))(source); // 0

•                                       // 1

•                                       // 2

•                                       // 0

•                                       // 3

•                                       // 4

•                                       // 5

•                                       // ...

*/

function merge(...sources) { return (start, sink) => { if (start !== 0) return; const n = sources.length; const sourceTalkbacks = new Array(n); let startCount = 0; let endCount = 0; let ended = false; const talkback = (t, d) => { if (t === 2) ended = true; for (let i = 0; i < n; i++) sourceTalkbacks[i] && sourceTalkbacks[i](t, d); }; for (let i = 0; i < n; i++) { if (ended) return; sources[i](0, (t, d) => { if (t === 0) { sourceTalkbacks[i] = d; if (++startCount === 1) sink(0, talkback); } else if (t === 2 && d) { ended = true; for (let j = 0; j < n; j++) { if (j !== i) sourceTalkbacks[j] && sourceTalkbacksj; } sink(2, d); } else if (t === 2) { sourceTalkbacks[i] = void 0; if (++endCount === n) sink(2); } else sink(t, d); }); } }; }

module.exports = merge;