import assert from 'node:assert/strict';
import { readFileSync } from 'node:fs';
import { test } from 'node:test';
import { Board } from '../src/board';
import { loadPack, parsePack } from '../src/levels';
import { hint, solve, uniqueSolution } from '../src/solver';
import type { CellDef } from '../src/types';

const c = (id: string, x: number, y: number, w = 1, h = 1, clue?: number): CellDef => ({ id, x, y, w, h, clue });

test('关卡包每一关恰好一个解', () => {
  for (const file of ['pack-1-tutorial.json', 'pack-2-advanced.json', 'pack-3-parity.json']) {
    const pack = parsePack(JSON.parse(readFileSync(new URL(`../levels/${file}`, import.meta.url), 'utf8')));
    const levels = loadPack(pack);
    assert.equal(levels.length, file === 'pack-3-parity.json' ? 6 : 10, `${file} 关数不符`);
    for (const lv of levels) {
      const paths = solve(lv.board, { limit: 3 });
      assert.equal(paths.length, 1, `${lv.def.id} 应唯一解，实际 ${paths.length}`);
      assert.equal(paths[0].length, lv.board.n);
    }
  }
});

test('GDD §7.3 样例盘：15 格、两块 2×2、线索落在大格上，唯一解且 B 是第 6 步', () => {
  // A A a b c / A A . d e / f g h B B / . i j B B / 1 l m . .
  const b = Board.fromCells([
    c('A', 0, 0, 2, 2),
    c('a', 2, 0),
    c('b', 3, 0),
    c('c', 4, 0),
    c('d', 3, 1),
    c('e', 4, 1),
    c('f', 0, 2),
    c('g', 1, 2),
    c('h', 2, 2),
    c('B', 3, 2, 2, 2, 6),
    c('i', 1, 3),
    c('j', 2, 3),
    c('one', 0, 4, 1, 1, 1),
    c('l', 1, 4),
    c('m', 2, 4),
  ]);
  assert.equal(b.n, 15);
  const paths = solve(b);
  assert.equal(paths.length, 1, '样例盘恰好唯一解');
  const p = paths[0];
  assert.deepEqual(
    p.map((i) => b.cells[i].id),
    ['one', 'l', 'm', 'j', 'h', 'B', 'd', 'e', 'c', 'b', 'a', 'A', 'f', 'g', 'i'],
  );
  // 从 j 往左绕 i 会让 B 最早第 8 步才到（红 8），所以第 5 步必须是 h、第 6 步进 B
  assert.equal(b.cells[p[4]].id, 'h');
  assert.equal(b.cells[p[5]].id, 'B');
});

test('无线索 1 的盘：任意起点都会被枚举', () => {
  const b = Board.fromCells([c('a', 0, 0), c('b', 1, 0), c('d', 1, 1, 1, 1, 3)]);
  const paths = solve(b);
  assert.equal(paths.length, 1);
  assert.equal(b.cells[paths[0][0]].id, 'a');
});

test('多解与无解', () => {
  assert.equal(solve(Board.fromCells([c('a', 0, 0), c('b', 1, 0), c('c', 2, 0)])).length, 2);
  assert.equal(uniqueSolution(Board.fromCells([c('a', 0, 0), c('b', 1, 0), c('c', 2, 0)])), null);
  assert.equal(solve(Board.fromCells([c('a', 0, 0, 1, 1, 1), c('b', 1, 0), c('c', 2, 0, 1, 1, 2)])).length, 0);
});

test('提示：起点 / 下一步 / 退回分叉 / 起手错', () => {
  const sol = [0, 1, 2, 3, 4];
  assert.deepEqual(hint(sol, []), { kind: 'start', cell: 0 });
  assert.deepEqual(hint(sol, [0, 1]), { kind: 'next', cell: 2 });
  assert.deepEqual(hint(sol, [0, 1, 7, 8]), { kind: 'backtrack', cell: 1, undoCount: 2 });
  assert.deepEqual(hint(sol, [3, 2]), { kind: 'restart', cell: 0 });
  assert.deepEqual(hint(sol, sol), { kind: 'none' });
});