import assert from 'assert';
import lodashStable from 'lodash';
import { slice, _ } from './utils.js';

describe('rest', function() {
  function fn(a, b, c) {
    return slice.call(arguments);
  }

  it('should apply a rest parameter to `func`', function() {
    var rest = _.rest(fn);
    assert.deepStrictEqual(rest(1, 2, 3, 4), [1, 2, [3, 4]]);
  });

  it('should work with `start`', function() {
    var rest = _.rest(fn, 1);
    assert.deepStrictEqual(rest(1, 2, 3, 4), [1, [2, 3, 4]]);
  });

  it('should treat `start` as `0` for `NaN` or negative values', function() {
    var values = [-1, NaN, 'a'],
        expected = lodashStable.map(values, lodashStable.constant([[1, 2, 3, 4]]));

    var actual = lodashStable.map(values, function(value) {
      var rest = _.rest(fn, value);
      return rest(1, 2, 3, 4);
    });

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

  it('should coerce `start` to an integer', function() {
    var rest = _.rest(fn, 1.6);
    assert.deepStrictEqual(rest(1, 2, 3), [1, [2, 3]]);
  });

  it('should use an empty array when `start` is not reached', function() {
    var rest = _.rest(fn);
    assert.deepStrictEqual(rest(1), [1, undefined, []]);
  });

  it('should work on functions with more than three parameters', function() {
    var rest = _.rest(function(a, b, c, d) {
      return slice.call(arguments);
    });

    assert.deepStrictEqual(rest(1, 2, 3, 4, 5), [1, 2, 3, [4, 5]]);
  });
});