import { Board } from './board.js';
import { makePiece } from './fen.js';
import { SquareSet } from './squareSet.js';
import { Piece, Square } from './types.js';
import { makeSquare, makeUci } from './util.js';
import { Position } from './xiangqi.js';

export const squareSet = (squares: SquareSet): string => {
  const r = [];
  for (let y = 7; y >= 0; y--) {
    for (let x = 0; x < 8; x++) {
      const square = x + y * 8;
      r.push(squares.has(square) ? '1' : '.');
      r.push(x < 7 ? ' ' : '\n');
    }
  }
  return r.join('');
};

export const piece = (piece: Piece): string => makePiece(piece);

export const board = (board: Board): string => {
  const r = [];
  for (let y = 7; y >= 0; y--) {
    for (let x = 0; x < 8; x++) {
      const square = x + y * 8;
      const p = board.get(square);
      const col = p ? piece(p) : '.';
      r.push(col);
      r.push(x < 7 ? (col.length < 2 ? ' ' : '') : '\n');
    }
  }
  return r.join('');
};

export const square = (sq: Square): string => makeSquare(sq);

export const dests = (dests: Map<Square, SquareSet>): string => {
  const lines = [];
  for (const [from, to] of dests) {
    lines.push(`${makeSquare(from)}: ${Array.from(to, square).join(' ')}`);
  }
  return lines.join('\n');
};

export const perft = (pos: Position, depth: number, log = false): number => {
  if (depth < 1) return 1;

  const ctx = pos.ctx();
  if (!log && depth === 1) {
    // Optimization for leaf nodes.
    let nodes = 0;
    for (const [, to] of pos.allDests(ctx)) {
      nodes += to.size();
    }
    return nodes;
  } else {
    let nodes = 0;
    for (const [from, dests] of pos.allDests(ctx)) {
      for (const to of dests) {
        const child = pos.clone();
        const move = { from, to };
        child.play(move);
        const children = perft(child, depth - 1, false);
        if (log) console.log(makeUci(move), children);
        nodes += children;
      }
    }
    return nodes;
  }
};