// Copyright 2021 Signal Messenger, LLC
// SPDX-License-Identifier: AGPL-3.0-only

import { assert } from 'chai';
import * as sinon from 'sinon';

import { map, take } from '../../util/iterables';

describe('iterable utilities', () => {
  describe('map', () => {
    it('returns an empty iterable when passed an empty iterable', () => {
      const fn = sinon.fake();

      assert.deepEqual([...map([], fn)], []);
      assert.deepEqual([...map(new Set(), fn)], []);
      assert.deepEqual([...map(new Map(), fn)], []);

      sinon.assert.notCalled(fn);
    });

    it('returns a new iterator with values mapped', () => {
      const fn = sinon.fake((n: number) => n * n);
      const result = map([1, 2, 3], fn);

      sinon.assert.notCalled(fn);

      assert.deepEqual([...result], [1, 4, 9]);
      assert.notInstanceOf(result, Array);

      sinon.assert.calledThrice(fn);
    });

    it('iterating doesn\'t "spend" the iterable', () => {
      const result = map([1, 2, 3], n => n * n);

      assert.deepEqual([...result], [1, 4, 9]);
      assert.deepEqual([...result], [1, 4, 9]);
      assert.deepEqual([...result], [1, 4, 9]);
    });

    it('can map over an infinite iterable', () => {
      const everyNumber = {
        *[Symbol.iterator]() {
          for (let i = 0; true; i += 1) {
            yield i;
          }
        },
      };

      const fn = sinon.fake((n: number) => n * n);
      const result = map(everyNumber, fn);
      const iterator = result[Symbol.iterator]();

      assert.deepEqual(iterator.next(), { value: 0, done: false });
      assert.deepEqual(iterator.next(), { value: 1, done: false });
      assert.deepEqual(iterator.next(), { value: 4, done: false });
      assert.deepEqual(iterator.next(), { value: 9, done: false });
    });
  });

  describe('take', () => {
    it('returns the first n elements from an iterable', () => {
      const everyNumber = {
        *[Symbol.iterator]() {
          for (let i = 0; true; i += 1) {
            yield i;
          }
        },
      };

      assert.deepEqual([...take(everyNumber, 0)], []);
      assert.deepEqual([...take(everyNumber, 1)], [0]);
      assert.deepEqual([...take(everyNumber, 7)], [0, 1, 2, 3, 4, 5, 6]);
    });

    it('stops after the iterable has been exhausted', () => {
      const set = new Set([1, 2, 3]);

      assert.deepEqual([...take(set, 3)], [1, 2, 3]);
      assert.deepEqual([...take(set, 4)], [1, 2, 3]);
      assert.deepEqual([...take(set, 10000)], [1, 2, 3]);
    });
  });
});