/* 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_board.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) {
      if (strlen(input) > 0) {
        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 non-zero number if the move was valid.
// Returns the number of flipped tiles.
int 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 0;
  }

  // The move must be below the upper bounds of the board.
  if (move.row > 8 || move.col > 8) {
    return 0;
  }

  // The move must be an empty spot.
  if (board[move.row][move.col] != EMPTY) {
    return 0;
  }

  int num_flipped_up = 0, num_flipped_down = 0, num_flipped_left = 0,
      num_flipped_right = 0, num_flipped_up_left = 0, num_flipped_up_right = 0,
      num_flipped_down_left = 0, num_flipped_down_right = 0;

  bool done_flipping_up = false, done_flipping_down = false,
       done_flipping_left = false, done_flipping_right = false,
       done_flipping_up_left = false, done_flipping_up_right = false,
       done_flipping_down_left = false, done_flipping_down_right = false;

  for (int i = 1; i < 8; i++) {
    if (!done_flipping_up && (move.row - i >= 0) &&
        board[move.row - i][move.col] == current_player) {

      if (i > 1) {
        bool flippable = true;
        for (int j = 1; flippable && j < i; j++) {
          if (board[move.row - j][move.col] == EMPTY) {
            flippable = false;
          }
        }

        if (flippable) {
          for (int j = 0; j < i; j++) {
            board[move.row - j][move.col] = current_player;
            num_flipped_up++;
          }
        }
      }

      done_flipping_up = true;
    }
    if (!done_flipping_down && (move.row + i < 8) &&
        board[move.row + i][move.col] == current_player) {

      if (i > 1) {
        bool flippable = true;
        for (int j = 1; flippable && j < i; j++) {
          if (board[move.row + j][move.col] == EMPTY) {
            flippable = false;
          }
        }

        if (flippable) {
          for (int j = 0; j < i; j++) {
            board[move.row + j][move.col] = current_player;
            num_flipped_down++;
          }
        }
      }

      done_flipping_down = true;
    }
    if (!done_flipping_left && (move.col - i >= 0) &&
        board[move.row][move.col - i] == current_player) {

      if (i > 1) {
        bool flippable = true;
        for (int j = 1; flippable && j < i; j++) {
          if (board[move.row][move.col - j] == EMPTY) {
            flippable = false;
          }
        }

        if (flippable) {
          for (int j = 0; j < i; j++) {
            board[move.row][move.col - j] = current_player;
            num_flipped_left++;
          }
        }
      }

      done_flipping_left = true;
    }
    if (!done_flipping_right && (move.col + i < 8) &&
        board[move.row][move.col + i] == current_player) {

      if (i > 1) {
        bool flippable = true;
        for (int j = 1; flippable && j < i; j++) {
          if (board[move.row][move.col + j] == EMPTY) {
            flippable = false;
          }
        }

        if (flippable) {
          for (int j = 0; j < i; j++) {
            board[move.row][move.col + j] = current_player;
            num_flipped_right++;
          }
        }
      }

      done_flipping_right = true;
    }
    /*if (!done_flipping_up_left &&) {*/
    /*done_flipping_up_left = true;*/
    /*}*/
    /*if (!done_flipping_up_right &&) {*/
    /*done_flipping_up_right = true;*/
    /*}*/
    /*if (!done_flipping_down_left &&) {*/
    /*done_flipping_down_left = true;*/
    /*}*/
    /*if (!done_flipping_down_right &&) {*/
    /*done_flipping_down_right = true;*/
    /*}*/
  }

  return num_flipped_up + num_flipped_down + num_flipped_left +
         num_flipped_right + num_flipped_up_left + num_flipped_up_right +
         num_flipped_down_left + num_flipped_down_right;
}

SCM scm_apply_move(SCM scm_move, SCM scm_board, SCM scm_player) {
  struct move move = scm_move_to_c_move(scm_move);

  enum player_color **board = SCM_UNBNDP(scm_board)
                                  ? copy_board(get_board())
                                  : scm_board_to_c_board(scm_board);

  enum player_color player = SCM_UNBNDP(scm_player)
                                 ? get_current_player()
                                 : scm_player_to_c_player(scm_player);

  SCM res_board;

  if (apply_move(board, player, move)) {
    res_board = scm_board_from_c_board(board);
  } else {
    res_board = SCM_EOL;
  }

  free_board(board);
  return res_board;
}

SCM scm_get_num_flipped_by_move(SCM scm_move, SCM scm_board, SCM scm_player) {
  struct move move = scm_move_to_c_move(scm_move);

  enum player_color **board = SCM_UNBNDP(scm_board)
                                  ? copy_board(get_board())
                                  : scm_board_to_c_board(scm_board);

  enum player_color player = SCM_UNBNDP(scm_player)
                                 ? get_current_player()
                                 : scm_player_to_c_player(scm_player);
  SCM res_num = scm_from_int(apply_move(board, player, move));
  free_board(board);

  return res_num;
}

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;
}

SCM scm_move_from_c_move(struct move move) {
  return scm_cons(scm_from_int(move.row), scm_from_int(move.col));
}

SCM scm_is_valid_move(SCM scm_move, SCM scm_board, SCM scm_player) {
  enum player_color **board =
      SCM_UNBNDP(scm_board) ? get_board() : scm_board_to_c_board(scm_board);

  enum player_color current_player = SCM_UNBNDP(scm_player)
                                         ? get_current_player()
                                         : scm_player_to_c_player(scm_player);

  struct move move = scm_move_to_c_move(scm_move);
  SCM is_valid = scm_from_bool(is_valid_move(board, current_player, move));

  if (!SCM_UNBNDP(scm_board)) {
    free_board(board);
  }

  return is_valid;
}

// Return the list of valid moves on a board for a player
SCM scm_valid_moves(SCM scm_board, SCM player) {
  enum player_color **board =
      SCM_UNBNDP(scm_board) ? get_board() : scm_board_to_c_board(scm_board);

  enum player_color current_player = SCM_UNBNDP(player)
                                         ? get_current_player()
                                         : scm_player_to_c_player(player);

  SCM result = SCM_EOL;
  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_move_from_c_move(move), result);
      }
    }
  }

  if (!SCM_UNBNDP(scm_board)) {
    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_get_current_player);
  scm_c_define_gsubr("other-player", 0, 0, 0, scm_get_other_player);
  scm_c_define_gsubr("valid-move?", 1, 2, 0, scm_is_valid_move);
  scm_c_define_gsubr("valid-moves", 0, 2, 0, scm_valid_moves);
  scm_c_define_gsubr("apply-move", 1, 2, 0, scm_apply_move);
  scm_c_define_gsubr("get-winner", 2, 0, 0, scm_get_winner);
  scm_c_define_gsubr("flipped-by-move", 1, 2, 0, scm_get_num_flipped_by_move);
  scm_c_define_gsubr("print-board", 0, 1, 0, scm_print_board);

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

  return scm_move_to_c_move(scm_move);
}

bool is_valid_move(enum player_color **board,
                   const enum player_color current_player,
                   const struct move move) {
  if (current_player == EMPTY) {
    return false;
  }

  // Make a copy of the input board. This is done because we lean on the logic
  // that exists in apply_move to check if a move is valid. We don't want to
  // necessarily mutate the board yet though.
  enum player_color **b = copy_board(board);
  // Apply the move to the copy of the board.
  bool res = apply_move(b, current_player, move);

  free_board(b);

  return res;
}

bool has_valid_moves(enum player_color **board,
                     const enum player_color current_player) {
  bool result = false;
  struct move move;
  for (move.row = 0; move.row < 8 && !result; move.row++) {
    for (move.col = 0; move.col < 8 && !result; move.col++) {
      result = is_valid_move(board, current_player, move);
    }
  }

  return result;
}