import 'dotenv/config';
import Prando from 'prando';
import {Gen, listOf, property, shrinklist, someInt} from './property.js';

function arrayEquals<A>(a: A[], b: A[]): boolean {
  return (
    Array.isArray(a) &&
    Array.isArray(b) &&
    a.length === b.length &&
    a.every((val, index) => val === b[index])
  );
}

function reverse<A>(arr: A[]): A[] {
  const result = [];
  for (let i = arr.length - 1; i >= 0; i--) {
    result.push(arr[i]);
  }
  return result;
}

function reverse_is_self_inverse(arr: number[]): Promise<boolean> {
  return Promise.resolve(arrayEquals(reverse(reverse(arr)), arr));
}

function gen2lists<A>(gen: Gen<A>): Gen<[A[], A[]]> {
  return (rng: Prando) => {
    const gl = listOf(gen)(rng);
    return (size: number) => {
      return [gl(size), gl(size)];
    };
  };
}

function reverse_with_two_lists<A>(arrs: [A[], A[]]): Promise<boolean> {
  return Promise.resolve(
    arrayEquals(
      reverse(arrs[0].concat(arrs[1])),
      reverse(arrs[1]).concat(reverse(arrs[0])),
    ),
  );
}

function shrink2lists<A>([l1, l2]: [A[], A[]]): [A[], A[]][] {
  const result: [A[], A[]][] = [];
  const s1 = shrinklist(l1);
  const s2 = shrinklist(l2);
  for (let i = 0; i < s1.length; i++) {
    const j = s2.length - i - 1;
    const news2 = j >= 0 ? s2[j] : [];
    result.push([s1[i], news2]);
  }
  return result;
}

export const prop_reverse_with_two_lists = property<[number[], number[]]>(
  gen2lists(someInt),
  reverse_with_two_lists,
  shrink2lists,
);

export const prop_reverse_is_self_inverse = property(
  listOf(someInt),
  reverse_is_self_inverse,
  shrinklist,
  l => {
    const tens = Math.floor(l.length / 10);
    return '< ' + 10 * (tens + 1);
  },
);