import assert from 'assert';
import { slice } from './utils.js';
import reduce from '../reduce.js';
import head from '../head.js';
import keys from '../keys.js';

describe('reduce', function() {
  var array = [1, 2, 3];

  it('should use the first element of a collection as the default `accumulator`', function() {
    assert.strictEqual(reduce(array), 1);
  });

  it('should provide correct `iteratee` arguments when iterating an array', function() {
    var args;

    reduce(array, function() {
      args || (args = slice.call(arguments));
    }, 0);

    assert.deepStrictEqual(args, [0, 1, 0, array]);

    args = undefined;
    reduce(array, function() {
      args || (args = slice.call(arguments));
    });

    assert.deepStrictEqual(args, [1, 2, 1, array]);
  });

  it('should provide correct `iteratee` arguments when iterating an object', function() {
    var args,
        object = { 'a': 1, 'b': 2 },
        firstKey = head(keys(object));

    var expected = firstKey == 'a'
      ? [0, 1, 'a', object]
      : [0, 2, 'b', object];

    reduce(object, function() {
      args || (args = slice.call(arguments));
    }, 0);

    assert.deepStrictEqual(args, expected);

    args = undefined;
    expected = firstKey == 'a'
      ? [1, 2, 'b', object]
      : [2, 1, 'a', object];

    reduce(object, function() {
      args || (args = slice.call(arguments));
    });

    assert.deepStrictEqual(args, expected);
  });
});