#include "peg_solitaire.h"

const std::vector<std::pair<int, int>> lab4::peg_solitaire::moves = { {0,2}, {0,-2}, {2,0}, {-2,0} };

bool lab4::peg_solitaire::is_move_possible(int x_from, int y_from, int x_to, int y_to) const
{
	if (x_from < 0 || x_from >= width || x_to < 0 || x_to >= width)
		return false;
	if (y_from < 0 || y_from >= height || y_to < 0 || y_to >= height)
		return false;
	if (!((abs(x_from - x_to) == 2 && y_from == y_to) || (abs(y_from - y_to) == 2 && x_from == x_to)))
		return false;
	if (board[y_from*width + x_from] == 0 || board[y_to*width + x_to] != 0 || board[(y_from + y_to)/2*width + (x_from + x_to)/2] == 0)
		return false;
	return true;
}

int lab4::peg_solitaire::make_move(int x_from, int y_from, int x_to, int y_to)
{
	int& from = board[y_from*width + x_from];
	int& over = board[(y_from + y_to) / 2 * width + (x_from + x_to) / 2];
	int score = from * over;
	board[y_to*width + x_to] = from;
	from = 0;
	over = 0;
	--stone_count;
	return score;
}

void lab4::peg_solitaire::undo_move(int x_from, int y_from, int x_to, int y_to, int score)
{
	int& to = board[y_to*width + x_to];
	board[(y_from + y_to) / 2 * width + (x_from + x_to) / 2] = score / to;
	board[y_from*width + x_from] = to;
	to = 0;
	++stone_count;
}

bool lab4::can_win(peg_solitaire game)
{
	if (game.stone_count == 1)
		return true;
	bool canwin = false;
	int score = 0;
	for (int y = 0; y < game.height; ++y)
	{
		for (int x = 0; x < game.width; ++x)
		{
			for (const std::pair<int, int>& pair : game.moves)
			{
				if (game.is_move_possible(x, y, x + pair.first, y + pair.second))
				{
					score = game.make_move(x, y, x + pair.first, y + pair.second);
					canwin = canwin || can_win(game);
					if (canwin) return canwin;
					game.undo_move(x, y, x + pair.first, y + pair.second, score);
				}
			}
		}
	}
	return canwin;
}

int lab4::best_win_score(peg_solitaire game)
{
	if (game.stone_count == 1)
		return 0;
	int best_score = -1;
	int score;
	int this_best_score;
	for (int y = 0; y < game.height; ++y)
	{
		for (int x = 0; x < game.width; ++x)
		{
			for (const std::pair<int, int>& pair : game.moves)
			{
				if (game.is_move_possible(x, y, x + pair.first, y + pair.second))
				{

					score = game.make_move(x, y, x + pair.first, y + pair.second);
					this_best_score = best_win_score(game);
					if (this_best_score != -1)
						best_score = std::max(this_best_score + score, best_score);
					game.undo_move(x, y, x + pair.first, y + pair.second, score);
				}
			}
		}
	}
	return best_score;
}