callbag-concat

/**

• callbag-concat
• Callbag factory that concatenates the data from multiple (2 or more)
• callbag sources. It starts each source at a time: waits for the previous
• source to end before starting the next source. Works with both pullable
• and listenable sources.
• npm install callbag-concat
• Example:

• const fromIter = require('callbag-from-iter');
  

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

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

• const source = concat(fromIter([10,20,30]), fromIter(['a','b']));
  

• iterate(x => console.log(x))(source); // 10
  

•                                       // 20
  

•                                       // 30
  

•                                       // a
  

•                                       // b
  

*/

const UNIQUE = {};

const concat = (...sources) => (start, sink) => { if (start !== 0) return; const n = sources.length; if (n === 0) { sink(0, () => {}); sink(2); return; } let i = 0; let sourceTalkback; let lastPull = UNIQUE; const talkback = (t, d) => { if (t === 1) lastPull = d; sourceTalkback(t, d); }; (function next() { if (i === n) { sink(2); return; } sources[i](0, (t, d) => { if (t === 0) { sourceTalkback = d; if (i === 0) sink(0, talkback); else if (lastPull !== UNIQUE) sourceTalkback(1, lastPull); } else if (t === 2 && d) { sink(2, d); } else if (t === 2) { i++; next(); } else { sink(t, d); } }); })(); };

export default concat;