package test;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;

public class ConnectFour {

	private class Move {
		final int row, col, score;

		Move(int row, int col, int score) {
			this.row = row;
			this.col = col;
			this.score = score;
		}

		Move(int score) {
			this(-1, -1, score);
		}

		@Override
		public String toString() {
			return String.format("%d %d %d", row, col, score);
		}
	}

	private static final char HUMAN = 'X';
	private static final char COMPUTER = 'O';
	private static final char EMPTY = '.';

	private static final char CONTINUE = '+';
	private static final char DRAW = '-';

	private static final int MAX_DEPTH = 9;

	private static final int ROWS = 6;
	private static final int COLS = 7;

	private final char[][] board = new char[ROWS][COLS];

	public ConnectFour() {
		for (int i = 0; i < board.length; i++) {
			Arrays.fill(board[i], EMPTY);
		}
	}

	public int humanMove(final int col) {
		for (int row = ROWS - 1; row >= 0; row--) {
			if (board[row][col] == EMPTY) {
				board[row][col] = HUMAN;
				return eval(HUMAN);
			}
		}
		throw new IllegalArgumentException("column full: " + col);
	}

	public int computerMove() {
		int depth = 0;
		for (int row = 0; row < ROWS; row++) {
			for (int col = 0; col < COLS; col++) {
				if (board[row][col] == EMPTY) {
					depth++;
				}
			}
		}
		Move move = maximum(Math.min(MAX_DEPTH, depth));
		board[move.row][move.col] = COMPUTER;
		return eval(COMPUTER);
	}

	private Move maximum(int depth) {
		if (depth == 0) {
			return new Move(0);
		}

		Move best = new Move(Integer.MIN_VALUE);

		for (Move move : getMoves()) {
			board[move.row][move.col] = COMPUTER;

			char result = eval(COMPUTER);
			int value = result == COMPUTER ? depth : minimum(depth-1).score;

			if (value > best.score) {
				best = new Move(move.row, move.col, value);
			}

			board[move.row][move.col] = EMPTY;
		}

		return best;
	}

	private Move minimum(int depth) {
		if (depth == 0) {
			return new Move(0);
		}

		Move worst = new Move(Integer.MAX_VALUE);

		for (Move move : getMoves()) {
			board[move.row][move.col] = HUMAN;

			char result = eval(HUMAN);
			int value = result == HUMAN ? -depth : maximum(depth-1).score;

			if (value < worst.score) {
				worst = new Move(move.row, move.col, value);
			}

			board[move.row][move.col] = EMPTY;
		}

		return worst;

	}

	private List<Move> getMoves() {
		List<Move> moves = new ArrayList<>();

		for (int col = 0; col < COLS; col++) {
			for (int row = ROWS - 1; row >= 0; row--) {
				if (board[row][col] == EMPTY) {
					moves.add(new Move(row, col, 0));
					break;
				}
			}
		}

		return moves;
	}

	private char eval(char player) {
		// Rows
		for (int row = 0; row < ROWS; row++) {
			for (int col = 0; col < COLS - 3; col++) {
				if (board[row][col+0] == player &&
					board[row][col+1] == player &&
					board[row][col+2] == player &&
					board[row][col+3] == player) {

					return player;
				}
			}
		}
		// Columns
		for (int col = 0; col < COLS; col++) {
			for (int row = 0; row < ROWS - 3; row++) {
				if (board[row+0][col] == player &&
					board[row+1][col] == player &&
					board[row+2][col] == player &&
					board[row+3][col] == player) {

					return player;
				}
			}
		}

		// Diagonals
		for (int row = 0; row < ROWS - 3; row++) {
			for (int col = 0; col < COLS - 3; col++) {
				if (board[row+0][col+0] == player &&
					board[row+1][col+1] == player &&
					board[row+2][col+2] == player &&
					board[row+3][col+3] == player) {

					return player;
				}
			}
		}

		for (int row = 0; row < ROWS - 3; row++) {
			for (int col = 3; col < COLS; col++) {
				if (board[row+0][col-0] == player &&
					board[row+1][col-1] == player &&
					board[row+2][col-2] == player &&
					board[row+3][col-3] == player) {

					return player;
				}
			}
		}

		for (int row = 0; row < ROWS; row++) {
			for (int col = 0; col < COLS; col++) {
				if (board[row][col] == EMPTY) return CONTINUE;
			}
		}

		return DRAW;
	}

	@Override
	public String toString() {
		String s = "";
		for (int row = 0; row < ROWS; row++) {
			for (int col = 0; col < COLS; col++) {
				s += board[row][col];
			}
			s += "\n";
		}
		return s;
	}

	public static void main(String[] args) {

		Scanner s = new Scanner(System.in);
		ConnectFour game = new ConnectFour();

		int result = CONTINUE;

		while (result == CONTINUE) {

//			result = game.computerMove();
			System.out.println(game);

			if (result != CONTINUE) break;

			System.out.print("Human move: ");
			String input = s.nextLine();
			if (input.equals("q")) System.exit(1);

			int x = Integer.parseInt(input);

			result = game.humanMove(x-1);
			if (result != CONTINUE) break;

			result = game.computerMove();
			System.out.println(game);
		}

		System.out.println(game);

		if (result == HUMAN) System.out.println("human won");
		if (result == COMPUTER) System.out.println("computer won");
		if (result == DRAW) System.out.println("draw");

		s.close();
	}
}