/** 오셀로 computer player: corners first, no X-squares next to an empty corner, no corner handed over. */
import { describe, expect, test } from 'bun:test';
import { SeededRng } from '@bg/engine';
import { decideBotAction } from '../bots/index';
import { othello, type OthelloAction, type OthelloState } from './index';
import type { Cell } from './rules';

const at = (l: string) => ({ x: 'abcdefgh'.indexOf(l[0]!), y: Number(l.slice(1)) - 1 });

/** A = black (the bot here). 8 rows of '.', 'B', 'W' (row 1 first). */
function fromRows(rows: string[]): OthelloState {
  const options = othello.optionsSchema.parse({ colorAssignment: 'hostBlack' });
  const s = othello.setup({ players: ['A', 'B'], options, rng: SeededRng.fromSeed([1, 2, 3, 4]), now: 0 });
  s.board = rows.join('').split('').map((c) => (c === 'B' ? 1 : c === 'W' ? 2 : 0)) as Cell[];
  s.turn = 'black';
  return s;
}
const decide = (s: OthelloState, seed = 1) => {
  const r = SeededRng.fromSeed([seed, 4, 4, 4]);
  return decideBotAction(othello, s, 'A', { now: 1000, random: () => r.next() }) as OthelloAction;
};
const legalLabels = (s: OthelloState) => othello.view(s, 'A').legalMoves!.map((m) => 'abcdefgh'[m.x]! + (m.y + 1)).sort();

describe('othello bot', () => {
  test('takes a corner when available', () => {
    // a1 (corner, flips b2) and f4 (flips e4 + more) are both legal.
    const s = fromRows(['........', '.W......', '..B.....', '...WWB..', '...BW...', '........', '........', '........']);
    expect(legalLabels(s)).toContain('a1');
    for (let seed = 1; seed <= 4; seed++) expect(decide(s, seed)).toEqual({ type: 'place', ...at('a1') });
  });

  test('avoids the X-square next to an empty corner even when it flips more', () => {
    // b2 flips two discs (c3, d4); g5 flips one.
    const s = fromRows(['........', '........', '..W.....', '...W....', '....BW..', '........', '........', '........']);
    const legal = legalLabels(s);
    expect(legal).toContain('b2');
    for (let seed = 1; seed <= 4; seed++) expect(decide(s, seed)).not.toEqual({ type: 'place', ...at('b2') });
  });

  test("accepts the opponent's undo request", () => {
    let s = othello.setup({ players: ['A', 'B'], options: othello.optionsSchema.parse({ colorAssignment: 'hostBlack' }), rng: SeededRng.fromSeed([1, 2, 3, 4]), now: 0 });
    const step = (who: string, a: OthelloAction) => (s = othello.apply(s, who, a, { rng: SeededRng.fromSeed([1, 1, 1, 1]), now: 1000 }).state);
    step('A', { type: 'place', ...at('d3') });
    step('B', { type: 'place', ...at('c3') });
    step('B', { type: 'requestUndo' });
    expect(decide(s)).toEqual({ type: 'respondUndo', accept: true });
  });
});