/**

• tallbag-filter

• ---

• Tallbag operator that conditionally lets data pass through. Works on either
• pullable or listenable sources.
• npm install tallbag-filter
• Example:

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

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

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

• const source = filter(x => x % 2)(fromIter([1,2,3,4,5]));

• iterate(x => console.log(x))(source); // 1

•                                       // 3

•                                       // 5

*/

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

const filter = condition => source => (start, sink) => { if (start !== 0) return; let talkback; let shadow; source(0, (t, d, s) => { if (t === 0) { shadow = makeShadow('filter', s); talkback = d; sink(0, talkback, shadow); } else if (t === 1) { if (condition(d)) { shadow(t, d); sink(t, d); } else talkback(1); } else sink(t, d); }); };

module.exports = filter;