/**
 * callbag-for-each
 * ----------------
 *
 * Callbag sink that consume both pullable and listenable sources. When called
 * on a pullable source, it will iterate through its data. When called on a
 * listenable source, it will observe its data.
 *
 * `npm install callbag-for-each`
 *
 * Examples
 * --------
 *
 * Consume a pullable source:
 *
 *     const fromIter = require('callbag-from-iter');
 *     const forEach = require('callbag-for-each');
 *
 *     const source = fromIter([10,20,30,40])
 *
 *     forEach(x => console.log(x))(source); // 10
 *                                           // 20
 *                                           // 30
 *                                           // 40
 *
 * Consume a listenable source:
 *
 *     const interval = require('callbag-interval');
 *     const forEach = require('callbag-for-each');
 *
 *     const source = interval(1000);
 *
 *     forEach(x => console.log(x))(source); // 0
 *                                           // 1
 *                                           // 2
 *                                           // 3
 *                                           // ...
 */

const forEach = operation => source => {
  let talkback;
  source(0, (t, d) => {
    if (t === 0) talkback = d;
    if (t === 1) operation(d);
    if (t === 1 || t === 0) talkback(1);
  });
};

module.exports = forEach;