/**

• callbag-callback

• ---

• Callbag operator that returns data passing through it via a callback.
• Basicall the same idea as map, but via a callback
• Works on either pullable or listenable sources.
• npm install callbag-callback
• Example:

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

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

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

• const source = callback((x,cb) => cb(null, x * 0.1))(fromIter([10,20,30,40]));

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

•                                       // 2

•                                       // 3

•                                       // 4

*/

const callback = f => source => (start, sink) => { if (start !== 0) return; source(0, (t, d) => { t === 1 ? f(d, (err, result) => err ? sink(2, err) : sink(t, err || result)) : sink(t, d) }) }

module.exports = callback;