import groupBy from './index';

// OK
const numbers: readonly number[] = [6.1, 4.2, 6.3]
const test1: { [key: string]: number[] } = groupBy(numbers, Math.floor);
const test2: { [key: string]: string[] } = groupBy(
  ['a', 'b', 'c', 'aa', 'bb', 'cc'],
  str => str.charAt(0)
);
const test3: { [key: string]: number[][] } = groupBy(
  [[1], [2], [1, 2]],
  arr => arr.length
);
const test4: {} = groupBy([], () => 'a');
const test5: { [key: string]: Array<number | string> } = groupBy(
  [1, 2, 3, '1', '2'],
  a => a
);
const test6 = groupBy(['a', 'b', 'c'], str => Symbol(str));
type K = 'a' | 'b';
const test7: Record<K, number[]> = groupBy([1, 2, 3], v =>
  v % 2 === 0 ? 'a' : 'b'
);

// Not OK
// @ts-expect-error
groupBy();

// First argument must be an array.
// @ts-expect-error
groupBy({}, Math.floor);
// @ts-expect-error
groupBy('hello', Math.floor);
// @ts-expect-error
groupBy(/hullo/, Math.floor);
// @ts-expect-error
groupBy(null, Math.floor);
// @ts-expect-error
groupBy(undefined, Math.floor);

// @ts-expect-error
groupBy(['a', 'b', 'c'], () => {});
// @ts-expect-error
groupBy(['a', 'b', 'c'], Math.floor);
// @ts-expect-error
groupBy(['a', 'b', 'c'], () => null);
// @ts-expect-error
groupBy([], {});
// @ts-expect-error
groupBy([], []);
// @ts-expect-error
groupBy([], /hullo/);
// @ts-expect-error
groupBy([], null);
// @ts-expect-error
groupBy([], undefined);
// @ts-expect-error
groupBy([]);
// @ts-expect-error
groupBy<any, 'good key'>([], () => 'bad key');