Cast a malloc returned type to silence a warning

[Project_algorithmic_C.git] / lib / othello.c

/*
 * =====================================================================================
 *
 *       Filename:  othello.c
 *
 *    Description:  Handle the othello board content
 *
 *        Version:  1.0
 *        Created:  25/04/2017 15:16:08
 *       Revision:  none
 *       Compiler:  gcc
 *
 *         Author:  Jerome Benoit (fraggle), jerome.benoit@piment-noir.org
 *   Organization:  Piment Noir
 *
 * =====================================================================================
 */

#include <stdlib.h>
#include <stdbool.h>
#include <string.h>

#include "othello.h"
#include "debug.h"

unsigned int current_player(unsigned int round_count) {

    if (round_count % 2 != 0) {
        return player_two;
    } else {
        return player_one;
    }
}

unsigned int current_opponent(unsigned int current_player) {

    if (current_player == player_one) {
        return player_two;
    } else {
        return player_one;
    }
}

/* for consistency with ncurses, the board coordinates are in the following order:
 * O--x-->
 * |
 * y
 * |
 * v
 * The origin O has (1, 1) coordinates */

unsigned int get_box_value(int y, int x, unsigned int pawn_array[board_size][board_size]) {

    return pawn_array[y-1][x-1];
}

bool is_box_type(int y, int x, unsigned int pawn_array[board_size][board_size], unsigned int type) {

    if (type > 2) {
        return NULL;
    }
    if (get_box_value(y, x, pawn_array) == type) {
        return true;
    } else {
        return false;
    }
}

static bool is_valid_coordinates(int y, int x) {

    if ((y > 0 && y < board_size + 1) && \
            (x > 0 && x < board_size + 1)) {
        return true;
    } else {
        return false;
    }
}

/* helper function to set a correct value at the (y, x) coordinates in the pawns array */
void set_pawn(int y, int x, unsigned int type, unsigned int pawn_array[board_size][board_size]) {

    if (type > 0 && type < 3 && \
            is_valid_coordinates(y, x)) {
        pawn_array[y-1][x-1] = type;
    } //FIXME: else case should set invalid values to permit to catch errors
}

/* reverse the pawn at (y, x) coordinates if it exists */
static void reverse_pawn(int y, int x, unsigned int pawn_array[board_size][board_size]) {

    if (is_box_type(y, x, pawn_array, black)) {
        set_pawn(y, x, white, pawn_array);
    } else if (is_box_type(y, x, pawn_array, white)) {
        set_pawn(y, x, black, pawn_array);
    }
}

void zero_pawns(unsigned int pawn_array[board_size][board_size]) {

    for (int i = 1; i <= board_size; i++) {
        for (int j = 1; j <= board_size; j++) {
            set_pawn(i, j, empty, pawn_array);
         }
    }
}

/* set the pawns in the start position */
void init_pawns(unsigned int pawn_array[board_size][board_size]) {

    /* the 2D array zeroing is not necessary if it is properly initialized to zero */
    zero_pawns(pawn_array);
    set_pawn(5, 4, black, pawn_array);
    set_pawn(4, 5, black, pawn_array);
    set_pawn(4, 4, white, pawn_array);
    set_pawn(5, 5, white, pawn_array);
}

unsigned int count_pawns_type(unsigned int pawn_array[board_size][board_size], unsigned int type) {
    unsigned int count = 0;

    if (type > 2) {
        return 0;
    }
    for (int i = 1; i <= board_size; i++) {
        for (int j = 1; j <= board_size; j++) {
            if (is_box_type(i, j, pawn_array, type)) {
                count++;
            }
        }
    }
    return count;
}

static void direction_to_coordinates(unsigned int direction, int* start_y, int* start_x) {

    if (direction == north) {
        *start_y = *start_y - 1;
    } else if (direction == north_east) {
        *start_y = *start_y - 1;
        *start_x = *start_x + 1;
    } else if (direction == east) {
        *start_x = *start_x + 1;
    } else if (direction == south_east) {
        *start_y = *start_y + 1;
        *start_x = *start_x + 1;
    } else if (direction == south) {
        *start_y = *start_y + 1;
    } else if (direction == south_west) {
        *start_y = *start_y + 1;
        *start_x = *start_x - 1;
    } else if (direction == west) {
        *start_x = *start_x - 1;
    } else if (direction == north_west) {
        *start_y = *start_y - 1;
        *start_x = *start_x - 1;
    }
}

bool is_board_full(unsigned int pawn_array[board_size][board_size]) {

    /* an alternate method is to test the round count vs. 60 */
    for (int i = 1; i <= board_size; i++) {
        for (int j = 1; j <= board_size; j++) {
            if (is_box_type(i, j, pawn_array , empty)) {
                return false;
            }
        }
    }
    return true;
}

unsigned int eval_winner(unsigned int nb_white, unsigned int nb_black) {

    if (nb_white > nb_black) {
        return player_two;
    } else if (nb_white < nb_black) {
        return player_one;
    } else {
        return 0;
    }
}

static unsigned int count_pawn_to_reverse_one_direction(int y, int x, int direction, unsigned int current_player, unsigned int pawn_array[board_size][board_size]) {
    unsigned int nb_pawns_reversed = 0;
    int moving_y = y, moving_x = x;

    /* count the pawns to reverse in the chosen direction */
    direction_to_coordinates(direction, &moving_y, &moving_x);
    while (true) {
        if (!is_valid_coordinates(moving_y, moving_x) || is_box_type(moving_y, moving_x, pawn_array, empty)) {
            return 0;
        }
        if (is_box_type(moving_y, moving_x, pawn_array, current_player)) {
            break;
        }
        nb_pawns_reversed++;
        direction_to_coordinates(direction, &moving_y, &moving_x);
    }
    return nb_pawns_reversed;
}

/* revert the pawns if needed in one direction */
static unsigned int reverse_one_direction(int y, int x, int direction, unsigned int current_player, unsigned int pawn_array[board_size][board_size], bool dry_run) {
    unsigned int nb_pawns_reversed = 0;
    int moving_y = y, moving_x = x;

    nb_pawns_reversed = count_pawn_to_reverse_one_direction(moving_y, moving_x, direction, current_player, pawn_array);

    /* now reverse the needed pawns */
    if (nb_pawns_reversed > 0 && !dry_run) {
        moving_y = y, moving_x = x;
        direction_to_coordinates(direction, &moving_y, &moving_x);
        while (!is_box_type(moving_y, moving_x, pawn_array, current_player)) {
            reverse_pawn(moving_y, moving_x, pawn_array);
            direction_to_coordinates(direction, &moving_y, &moving_x);
        }
    }
    return nb_pawns_reversed;
}

/* loop optimized version of valid_shot function changing nothing to the pawns 2D array */
bool is_legal_shot(int y, int x, unsigned int current_player, unsigned int pawn_array[board_size][board_size]) {
    unsigned int nb_pawns_reversed = 0;

    if (!is_valid_coordinates(y, x) || !is_box_type(y, x, pawn_array, empty)) {
        return false;
    }

    for (unsigned int direction = north; direction <= north_west; direction++) {
        nb_pawns_reversed += reverse_one_direction(y, x, direction, current_player, pawn_array, true);
        if (nb_pawns_reversed > 0) {
            return true;
        }
    }
    return false;
}

/* play the shot if legal and flip or reverse the necessary pawns */
unsigned int valid_shot(int y, int x, unsigned int current_player, unsigned int pawn_array[board_size][board_size]) {
    unsigned int nb_pawns_reversed = 0;

    if (!is_valid_coordinates(y, x) || !is_box_type(y, x, pawn_array, empty)) {
        return 0;
    }

    for (unsigned int direction = north; direction <= north_west; direction++) {
        nb_pawns_reversed += reverse_one_direction(y, x, direction, current_player, pawn_array, false);
    }

    if (nb_pawns_reversed == 0) {
        return nb_pawns_reversed;
    }

    set_pawn(y, x, current_player, pawn_array);
    return nb_pawns_reversed;
}

static void add_shots_list_cell(int y, int x, unsigned int type, struct shots_list_s* shots_list) {
    struct shots_list_s* list_cell = (struct shots_list_s*)malloc(sizeof(struct shots_list_s));
    if (!list_cell) {
        exit(EXIT_FAILURE);
    }

    if (type > 0 && type < 5 && is_valid_coordinates(y, x)) {
        list_cell->y = y;
        list_cell->x = x;
        list_cell->type = type;
        list_add_tail(&(list_cell->list), &(shots_list->list));
    }
}

void free_shots_list(struct shots_list_s* shots_list) {
    struct shots_list_s* list_counter;

    while (!list_empty(&shots_list->list)) {
        list_counter = list_entry(shots_list->list.next, struct shots_list_s, list);
        list_del(&(list_counter->list));
        free(list_counter);
    }

}

void build_playable_shots_list(unsigned int current_player, struct shots_list_s* shots_list, unsigned int pawn_array[board_size][board_size]) {

    for (unsigned int i = 0; i <= board_size; i++) {
        for (unsigned int j = 0; j <= board_size; j++) {
            if (is_legal_shot(i, j, current_player, pawn_array)) {
                add_shots_list_cell(i, j, hint_allowed, shots_list);
            /* FIXME: a neighbourhood detection is needed
            } else if (is_box_type(i, j, pawn_array, empty)){
                add_shots_list_cell(i, j, hint_forbidden, shots_list);
            */
            }
        }
    }
}