import { describe, expect, it } from '@jest/globals';
import { L, _, toNative, undef } from '../src/core';
import { toBoolean as $b, iif } from '../src/bool';
import { toNumber as $n, Num, Succ, Zero, fromNumber as _n, eq as eqn, even, odd, succ, sum } from '../src/num';
import { toArray as $a, toNumberArray as $na, Cons, List, Nil, fromArray as _a, fromNumberArray as _na, all, any, concat, cons, eq, filter, foldl, foldlz, foldr, foldrz, head, map, tail } from '../src/list';

describe('List', () => {
  const iterate: (n: Num) => List<Num> = n => new L(() => Cons._(n)._(iterate(Succ._(n))).value);
  const infinite: List<Num> = iterate(Zero);

  describe('toArray', () => {
    it('converts []', () => {
      expect($a(Nil)).toEqual([]);
    });

    it('converts [0]', () => {
      expect($a(Cons._(_n(0))._(Nil)).map($n)).toEqual([0]);
    });

    it('converts [0, 1]', () => {
      expect($a(Cons._(_n(0))._(Cons._(_n(1))._(Nil))).map($n)).toEqual([0, 1]);
    });
  });

  describe('fromArray', () => {
    it('converts []', () => {
      expect($a(_a([]))).toEqual([]);
    });

    it('converts [0]', () => {
      expect($a(_a([0].map(_n))).map($n)).toEqual([0]);
    });

    it('converts 2', () => {
      expect($a(_a([0, 1].map(_n))).map($n)).toEqual([0, 1]);
    });
  });

  describe('cons', () => {
    it('0 cons Nil is [0]', () => {
      expect($na(cons._(_n(0))._(Nil))).toEqual([0]);
    });

    it('0 cons [1] is [0, 1]', () => {
      expect($na(cons._(_n(0))._(_na([1])))).toEqual([0, 1]);
    });

    it('0 cons [1, 2] is [0, 1, 2]', () => {
      expect($na(cons._(_n(0))._(_na([1, 2])))).toEqual([0, 1, 2]);
    });

    it('handles infinite lists', () => {
      expect($n(cons._(_n(0))._(infinite)._(undef)._(_(x => _(_xs => x))))).toBe(0);
    });
  });

  describe('concat', () => {
    it('Nil concat Nil is Nil', () => {
      expect($na(concat._(Nil)._(Nil))).toEqual([]);
    });

    it('[0] concat [1] is [0, 1]', () => {
      expect($na(concat._(_na([0]))._(_na([1])))).toEqual([0, 1]);
    });

    it('[0, 1] concat [2, 3] is [0, 1, 2, 3]', () => {
      expect($na(concat._(_na([0, 1]))._(_na([2, 3])))).toEqual([0, 1, 2, 3]);
    });

    it('handles infinite lists', () => {
      expect($n(concat._(infinite)._(infinite)._(undef)._(_(x => _(_xs => x))))).toBe(0);
    });
  });

  describe('head', () => {
    it('returns nothing from Nil', () => {
      expect(() => toNative(head._(Nil))).toThrow();
    });

    it('returns only item', () => {
      expect($n(head._(_na([0])))).toBe(0);
    });

    it('returns first item', () => {
      expect($n(head._(_na([0, 1])))).toBe(0);
    });

    it('handles infinite lists', () => {
      expect($n(head._(infinite))).toBe(0);
    });
  });

  describe('tail', () => {
    it('drops nothing from Nil', () => {
      expect(() => $na(tail._(Nil))).toThrow();
    });

    it('drops only item', () => {
      expect($na(tail._(_na([0])))).toEqual([]);
    });

    it('drops first item', () => {
      expect($na(tail._(_na([0, 1])))).toEqual([1]);
    });

    it('handles infinite lists', () => {
      expect($n(head._(tail._(infinite)))).toBe(1);
    });
  });

  describe('foldl', () => {
    it('folds Nil', () => {
      expect($n(foldl._(sum)._(Zero)._(_na([])))).toBe(0);
    });

    it('folds single item', () => {
      expect($n(foldl._(sum)._(Zero)._(_na([1])))).toBe(1);
    });

    it('folds several items', () => {
      expect($n(foldl._(sum)._(Zero)._(_na([1, 2])))).toBe(3);
    });
  });

  describe('foldlz', () => {
    it('does not fold Nil', () => {
      expect(() => $n(foldlz._(sum)._(Nil))).toThrow();
    });

    it('folds single item', () => {
      expect($n(foldlz._(sum)._(_na([1])))).toBe(1);
    });

    it('folds several items', () => {
      expect($n(foldlz._(sum)._(_na([1, 2])))).toBe(3);
    });
  });

  describe('foldr', () => {
    it('folds Nil', () => {
      expect($n(foldr._(sum)._(Zero)._(_na([])))).toBe(0);
    });

    it('folds single item', () => {
      expect($n(foldr._(sum)._(Zero)._(_na([1])))).toBe(1);
    });

    it('folds several items', () => {
      expect($n(foldr._(sum)._(Zero)._(_na([1, 2])))).toBe(3);
    });

    it('handles infinite lists', () => {
      expect($n(
        foldr
          ._(_(x => _(a => sum._(x)._(iif._(eqn._(_n(5))._(x))._(Zero)._(a)))))
          ._(Zero)
          ._(infinite)))
        .toBe(15);
    });
  });

  describe('foldrz', () => {
    it('does not fold Nil', () => {
      expect(() => $n(foldrz._(sum)._(Nil))).toThrow();
    });

    it.failing('folds single item', () => {
      expect($n(foldrz._(sum)._(_na([1])))).toBe(1);
    });

    it.failing('folds several items', () => {
      expect($n(foldrz._(sum)._(_na([1, 2])))).toBe(3);
    });

    it.failing('handles infinite lists', () => {
      expect($n(
        foldrz
          ._(_(x => _(a => sum._(x)._(iif._(eqn._(_n(5))._(x))._(Zero)._(a)))))
          ._(infinite)))
        .toBe(15);
    });
  });

  describe('eq', () => {
    it('Nil eq Nil is True', () => {
      expect($b(eq._(eqn)._(_na([]))._(_na([])))).toEqual(true);
    });

    it('Nil eq [0, 1, 2] is False', () => {
      expect($b(eq._(eqn)._(_na([]))._(_na([0, 1, 2])))).toEqual(false);
    });

    it('[0, 1, 2] eq Nil is False', () => {
      expect($b(eq._(eqn)._(_na([0, 1, 2]))._(_na([])))).toEqual(false);
    });

    it('[0] eq [0, 1, 2] is False', () => {
      expect($b(eq._(eqn)._(_na([0]))._(_na([0, 1, 2])))).toEqual(false);
    });

    it('[0, 1, 2] eq [0] is False', () => {
      expect($b(eq._(eqn)._(_na([0, 1, 2]))._(_na([0])))).toEqual(false);
    });

    it('[1, 2, 0] eq [0, 1, 2] is False', () => {
      expect($b(eq._(eqn)._(_na([1, 2, 0]))._(_na([0, 1, 2])))).toEqual(false);
    });

    it('[0, 1, 2] eq [1, 2, 0] is False', () => {
      expect($b(eq._(eqn)._(_na([0, 1, 2]))._(_na([1, 2, 0])))).toEqual(false);
    });

    it('[0, 1, 2] eq [0, 1, 2] is True', () => {
      expect($b(eq._(eqn)._(_na([0, 1, 2]))._(_na([0, 1, 2])))).toEqual(true);
    });

    it('handles infinite lists', () => {
      expect($b(eq._(eqn)._(_na([0, 1, 2]))._(infinite))).toEqual(false);
    });
  });

  describe('map', () => {
    it('maps Nil', () => {
      expect($na(map._(succ)._(_na([])))).toEqual([]);
    });

    it('maps only item', () => {
      expect($na(map._(succ)._(_na([0])))).toEqual([1]);
    });

    it('maps several items', () => {
      expect($na(map._(succ)._(_na([0, 1])))).toEqual([1, 2]);
    });

    it('handles infinite lists', () => {
      expect($n(head._(map._(succ)._(infinite)))).toBe(1);
    });
  });

  describe('filter', () => {
    it('filter Nil', () => {
      expect($na(filter._(odd)._(_na([])))).toEqual([]);
    });

    it('filters only item', () => {
      expect($na(filter._(odd)._(_na([])))).toEqual([]);
    });

    it('filters several items', () => {
      expect($na(filter._(odd)._(_na([0, 1])))).toEqual([1]);
    });

    it('handles infinite lists', () => {
      expect($n(head._(filter._(odd)._(infinite)))).toBe(1);
    });
  });

  describe('any', () => {
    it('any Nil is False', () => {
      expect($b(any._(odd)._(_na([])))).toEqual(false);
    });

    it('any for no matching item is False', () => {
      expect($b(any._(odd)._(_na([0, 2])))).toEqual(false);
    });

    it('any for matching item is True', () => {
      expect($b(any._(odd)._(_na([0, 1, 2])))).toEqual(true);
    });

    it('handles infinite lists', () => {
      expect($b(any._(odd)._(infinite))).toEqual(true);
    });
  });

  describe('all', () => {
    it('all Nil is True', () => {
      expect($b(all._(even)._(_na([])))).toEqual(true);
    });

    it('all for non-matching item is False', () => {
      expect($b(all._(even)._(_na([0, 1, 2])))).toEqual(false);
    });

    it('all for no non-matching item is True', () => {
      expect($b(all._(even)._(_na([0, 2])))).toEqual(true);
    });

    it('handles infinite lists', () => {
      expect($b(all._(even)._(infinite))).toEqual(false);
    });
  });
});