path: root/src/move.c

/* This file is a part of othello-ai-guile-c
 *
 * Copyright (C) 2021  Robby Zambito
 *
 * othello-ai-guile-c is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * othello-ai-guile-c is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

#define _GNU_SOURCE

#include <stdio.h>

#include <libguile.h>
#include <readline/history.h>
#include <readline/readline.h>

#include "othello.h"
#include "othello_move.h"

#define STREQ(a, b) (strcmp(a, b) == 0)

static void print_help() {
  puts("To enter a move, enter the two row and column seperated by spaces.\n"
       "For example `0 0` will select the top left corner.\n\n"
       "p - Print the board again\n"
       "g - Drop into a guile repl\n"
       "\n"
       "In the guile repl you can define an AI to use for the current"
       "player.\n"
       "After you define an AI for that player, it will be used for the rest "
       "of the game instead of prompting for input for that user.\n");
}

static char *prompt_player(enum player_color current_player) {
  switch (current_player) {
  case WHITE:
    return "Player 1 [h for help] > ";
  case BLACK:
    return "Player 2 [h for help] > ";
  default:
    perror("There is no current player");
    exit(EXIT_FAILURE);
  }
}

struct move prompt_get_move(enum player_color current_player) {
  // Initialize move to an invalid move.
  struct move move = {-1, -1};

  char *prompt = prompt_player(current_player);
  do {
    char *input = readline(prompt);

    if (input != NULL) {
      add_history(input);
      if (STREQ(input, "h")) {
        print_help();
      } else if (STREQ(input, "p")) {
        print_board(get_board());
        /*} else if (STREQ(input, "g")) {*/
        /*int argc = 1;*/
        /*char **argv = calloc(1, sizeof(char *));*/
        /*argv[0] = "othello";*/
        /*[>scm_with_guile(void *(*func)(void *), void *data)<]*/
        /*scm_boot_guile(argc, argv, inner_main, NULL);*/
        /*free(argv);*/
      } else {
        sscanf(input, "%d %d", &move.row, &move.col);
      }
    } else {
      // If input was NULL, we have reached an EOF and would like to exit.
      free(input);
      exit(0);
    }

    free(input);
  } while (!is_valid_move(get_board(), current_player, move));

  return move;
}

/* Returns true if the move was valid */
bool apply_move(enum player_color **board, enum player_color current_player,
                struct move move) {

  // The move must be a positive position.
  if (move.row < 0 || move.col < 0) {
    return false;
  }

  // The move must be below the upper bounds of teh board.
  if (move.row > 8 || move.col > 8) {
    return false;
  }

  // The move must be an empty spot.
  if (board[move.row][move.col] != EMPTY) {
    return false;
  }

  // Flip in up direction
  bool flipped_up = false;
  for (int i = move.row - 1;
       i > 0 && board[i][move.col] != EMPTY && !flipped_up; i--) {
    if (board[i][move.col] == current_player) {
      if (i < move.row - 1) {
        for (int j = move.row; j > i; j--) {
          board[j][move.col] = current_player;
        }
        flipped_up = true;
      } else {
        break;
      }
    }
  }

  // Flip in down direction
  bool flipped_down = false;
  for (int i = move.row + 1;
       i < 8 && board[i][move.col] != EMPTY && !flipped_down; i++) {
    if (board[i][move.col] == current_player) {
      if (i > move.row + 1) {
        for (int j = move.row; j < i; j++) {
          board[j][move.col] = current_player;
        }
        flipped_down = true;
      } else {
        break;
      }
    }
  }

  // Flip in left direction
  bool flipped_left = false;
  for (int i = move.col - 1;
       i > 0 && board[move.row][i] != EMPTY && !flipped_left; i--) {
    if (board[move.row][i] == current_player) {
      if (i < move.col - 1) {
        for (int j = move.col; j > i; j--) {
          board[move.row][j] = current_player;
        }
        flipped_left = true;
      } else {
        break;
      }
    }
  }

  // Flip in right direction
  bool flipped_right = false;
  for (int i = move.col + 1;
       i < 8 && board[move.row][i] != EMPTY && !flipped_right; i++) {
    if (board[move.row][i] == current_player) {
      if (i > move.col + 1) {
        for (int j = move.col; j < i; j++) {
          board[move.row][j] = current_player;
        }
        flipped_right = true;
      } else {
        break;
      }
    }
  }

  return flipped_up || flipped_down || flipped_left || flipped_right;
}

// Return the current board as a list of lists
static SCM scm_get_board(void) {
  enum player_color **board = get_board();
  // 2D list of empty spaces
  SCM scm_board =
      scm_make_list(scm_from_int(8), scm_make_list(scm_from_int(0), NULL));
  for (int i = 0; i < 8; i++) {
    for (int j = 7; j >= 0; j--) {
      if (board[i][j] == WHITE) {
        scm_list_set_x(scm_board, scm_from_int(i),
                       scm_cons(scm_from_utf8_symbol("white"),
                                scm_list_ref(scm_board, scm_from_int(i))));
      } else if (board[i][j] == BLACK) {
        scm_list_set_x(scm_board, scm_from_int(i),
                       scm_cons(scm_from_utf8_symbol("black"),
                                scm_list_ref(scm_board, scm_from_int(i))));
      } else {
        scm_list_set_x(scm_board, scm_from_int(i),
                       scm_cons(scm_from_utf8_symbol("empty"),
                                scm_list_ref(scm_board, scm_from_int(i))));
      }
    }
  }
  return scm_board;
}

static struct move scm_move_to_c_move(SCM scm_move) {
  struct move move = {-1, -1};
  move.row = scm_to_int(scm_car(scm_move));
  move.col = scm_to_int(scm_cdr(scm_move));
  return move;
}

static SCM scm_current_player(void) {
  switch (get_current_player()) {
  case WHITE:
    return scm_from_utf8_symbol("white");
  case BLACK:
    return scm_from_utf8_symbol("black");
  default:
    return scm_from_utf8_symbol("empty");
  }
}

static SCM scm_is_valid_move(SCM scm_board, SCM scm_player, SCM scm_move) {
  enum player_color **board = calloc(8, sizeof(enum player_color *));
  for (int i = 0; i < 8; i++) {
    board[i] = calloc(8, sizeof(enum player_color));
    for (int j = 0; j < 8; j++) {
      if (scm_is_true(
              scm_eq_p(scm_list_ref(scm_list_ref(scm_board, scm_from_int(i)),
                                    scm_from_int(j)),
                       scm_from_utf8_symbol("white")))) {
        board[i][j] = WHITE;
      } else if (scm_is_true(scm_eq_p(
                     scm_list_ref(scm_list_ref(scm_board, scm_from_int(i)),
                                  scm_from_int(j)),
                     scm_from_utf8_symbol("black")))) {
        board[i][j] = BLACK;
      } else {
        board[i][j] = EMPTY;
      }
    }
  }

  enum player_color current_player = BLACK;

  struct move move = scm_move_to_c_move(scm_move);
  return scm_from_bool(is_valid_move(board, current_player, move));
}

// Return the list of valid moves on a board for a player
static SCM scm_valid_moves(SCM scm_board, SCM player) {
  enum player_color **board = calloc(8, sizeof(enum player_color *));
  for (int i = 0; i < 8; i++) {
    board[i] = calloc(8, sizeof(enum player_color));
  }

  enum player_color current_player = EMPTY;

  if (scm_is_true(scm_eq_p(player, scm_from_utf8_symbol("white")))) {
    current_player = WHITE;
  } else if (scm_is_true(scm_eq_p(player, scm_from_utf8_symbol("black")))) {
    current_player = BLACK;
  }
  current_player = BLACK;

  SCM result = scm_make_list(scm_from_int(0), NULL);
  for (int i = 0; i < 8; i++) {
    for (int j = 0; j < 8; j++) {
      struct move move = {i, j};
      if (is_valid_move(board, current_player, move)) {
        result = scm_cons(scm_cons(scm_from_int(i), scm_from_int(j)), result);
      }
    }
  }

  free_board(board);
  return result;
}

struct move get_scm_move(char *strategy_path) {
  // Initialize move to an invalid move.
  struct move move = {-1, -1};
  scm_init_guile();

  // Initialize primitives
  scm_c_define_gsubr("get-board", 0, 0, 0, scm_get_board);
  scm_c_define_gsubr("current-player", 0, 0, 0, scm_current_player);
  scm_c_define_gsubr("valid-move?", 3, 0, 0, scm_is_valid_move);
  scm_c_define_gsubr("valid-moves", 2, 0, 0, scm_valid_moves);

  // Read the move from scheme
  SCM scm_move = scm_c_primitive_load(strategy_path);

  return scm_move_to_c_move(scm_move);
}