#include <climits>
#include "ai_mc.h"


static const int mc_ngames = 500;


static int playout(Board &bd, int player) {
	Move poss[N * N * N];

	while (true) {
		int nposs = 0;
		int winidx = -1;
		bd.forEachMove(player, [&bd, &poss, &nposs, &winidx, player](Move mv) {
			Board bd2 = bd;
			int win = bd2.applyCW(mv);
			if (win * player >= 0) {
				poss[nposs++] = mv;
				if (win != 0) {
					winidx = nposs - 1;
					return true;
				}
			}
			return false;
		});

		if (nposs == 0) return -player;

		int index = winidx == -1 ? rand() % nposs : winidx;

		int win = bd.applyCW(poss[index]);
		if (win != 0) return win;

		player = -player;
	}
}

Move AI::MC::findMove(const Board &bd, int player) {
	// 'maxscore' and 'score' below have high values for 'player'.
	int maxscore = INT_MIN;
	Move maxmove = Move(-1, -1);

	cerr << '[';

	bd.forEachMove(player, [&bd, &maxscore, &maxmove, player](Move mv) {
		int score = 0;

		Board bd2 = bd;
		int win = bd2.applyCW(mv);
		if (win == player) {
			maxscore = INT_MAX;
			maxmove = mv;
			cerr << "Found winning move!";
			return true;
		} else if (win == -player) {
			return false;
		}

		for (int i = 0; i < mc_ngames; i++) {
			Board bd3 = bd;
			bd3.apply(mv);
			score += playout(bd3, -player);
		}

		score *= player;  // fix sign

		cerr << score << ',';

		if (score > maxscore) {
			maxscore = score;
			maxmove = mv;
		}

		return false;
	});

	cerr << ']' << endl;

	cerr << "Chose move with score " << maxscore << endl;

	return maxmove;
}