chessc/src/chess.h

#ifndef CHESS_H
#define CHESS_H

/* the "board" is the playable area on which
 * pieces move. pieces are represented by numbers:
 * 0 - no piece
 * 1 - pawn
 * 2 - rook
 * 3 - knight
 * 4 - bishop
 * 5 - queen
 * 6 - king
*/

#include <stdbool.h>

// board size constraints
#define BOARD_HORIZONTAL 8
#define BOARD_VERTICAL 8

// type abstractions
typedef enum { WHITE, BLACK } player_e;

typedef int board_t[BOARD_VERTICAL][BOARD_HORIZONTAL];

#define PIECE_COUNT 13 // how many unique pieces are there
#define MAX_PIECE_MOVE_COUNT 27 // the max possible num of options where to move in one moment
typedef enum {
    NONE,

    WPAWN,
    WROOK,
    WKNIGHT,
    WBISHOP,
    WQUEEN,
    WKING,

    BPAWN,
    BROOK,
    BKNIGHT,
    BBISHOP,
    BQUEEN,
    BKING
} piece_e;

typedef struct {
    int x;
    int y;
} pos_t;

typedef struct {
    // what
    // where from
    // where to
    piece_e piece;
    pos_t from;
    pos_t to;
} move_t;

// the default arrangment of pieces on the board
// negative numbers are black, positive ones white
#define BOARD_DEFAULT_CONFIG \
(board_t){\
    { BROOK, BKNIGHT, BBISHOP, BQUEEN, BKING, BBISHOP, BKNIGHT, BROOK },\
    { BPAWN, BPAWN,   BPAWN,   BPAWN,  BPAWN, BPAWN,   BPAWN,   BPAWN },\
    { NONE,  NONE,    NONE,    NONE,   NONE,  NONE,    NONE,    NONE  },\
    { NONE,  NONE,    NONE,    NONE,   NONE,  NONE,    NONE,    NONE  },\
    { NONE,  NONE,    NONE,    NONE,   NONE,  NONE,    NONE,    NONE  },\
    { NONE,  NONE,    NONE,    NONE,   NONE,  NONE,    NONE,    NONE  },\
    { WPAWN, WPAWN,   WPAWN,   WPAWN,  WPAWN, WPAWN,   WPAWN,   WPAWN },\
    { WROOK, WKNIGHT, WBISHOP, WQUEEN, WKING, WBISHOP, WKNIGHT, WROOK }\
}

typedef struct {
    piece_e piece;
    pos_t options[MAX_PIECE_MOVE_COUNT];
    unsigned int piece_move_count;
} valid_move_t;

/** FIXED: ALSO DEPENDS ON THE STATE OF THE GAME - 
 *  e.g. a pawn cannot move two places in the middle 
 *  of the game but can in the first round 
 *  => ASSUME NO OTHER PIECES - then ALWAYS CHECK 
 *  FOR PIECE COLLISIONS and FOR ROUND COUNT 
 *  (pawn 1 || 2 move)
 */

 /** MAYBE: consider the POV from both sides???!!! */
 /**
  * the NONE, PAWN, KNIGHT and KING pieces' relative_moves are
  * treated like specific coordinates relative to their
  * position, 
  * whereas the BISHOP, ROOK and QUEEN pieces' 'moves'
  * are treated as *directions* in which they can move rather than
  * absolute x,y values -> e.g. the rook can move 
  * up, down, left, right * n -> and then bounds & edge cases are checked
  */
#define DEFAULT_VALID_MOVES (valid_move_t[PIECE_COUNT]){\
    {NONE, {}, 0},\
    \
    {WPAWN, {\
        { 0, -1}, {-1, -1}, {+1, -1}, { 0, -2}\
    }, 4},\
    {WROOK, {\
        { 0, -1}, { 0, +1}, {-1,  0}, {+1,  0}\
    }, 4},\
    {WKNIGHT, {\
        {-1, -2}, {+1, -2}, {-2, -1}, {-2, +1},\
        {+2, -1}, {+2, +1}, {-1, -2}, {-1, +2}\
    }, 8},\
    {WBISHOP, {\
        {-1, -1}, {-1, +1}, {+1, -1}, {+1, +1}\
    }, 4},\
    {WQUEEN, {\
        {0,  -1}, {0,  +1}, {-1,  0}, {+1,  0},\
        {-1, -1}, {-1, +1}, {+1, -1}, {+1, +1}\
    }, 8},\
    {WKING, {\
        { 0, -1}, { 0, +1}, {-1,  0}, {+1,  0},\
        {-1, -1}, {-1, +1}, {+1, -1}, {+1, +1}\
    }, 8},\
    \
    {BPAWN, {\
        { 0, -1}, {-1, -1}, {+1, -1}, { 0, -2}\
    }, 4},\
    {BROOK, {\
        { 0, -1}, { 0, +1}, {-1,  0}, {+1,  0}\
    }, 4},\
    {BKNIGHT, {\
        {-1, -2}, {+1, -2}, {-2, -1}, {-2, +1},\
        {+2, -1}, {+2, +1}, {-1, -2}, {-1, +2}\
    }, 8},\
    {BBISHOP, {\
        {-1, -1}, {-1, +1}, {+1, -1}, {+1, +1}\
    }, 4},\
    {BQUEEN, {\
        {0,  -1}, {0,  +1}, {-1,  0}, {+1,  0},\
        {-1, -1}, {-1, +1}, {+1, -1}, {+1, +1}\
    }, 8},\
    {BKING, {\
        { 0, -1}, { 0, +1}, {-1,  0}, {+1,  0},\
        {-1, -1}, {-1, +1}, {+1, -1}, {+1, +1}\
    }, 8}\
}

/**
 * states in which the game can end
 * CONTINUE => the game does not end, it continues
 * CHECKMATE => one side wins
 * STALEMATE => it's a draw
*/
typedef enum {
    CONTINUE,
    CHECKMATE,
    STALEMATE
} end_condition_e;

/**
 * a tracker for which pieces have been captured by who
 * white contains opponent pieces WHITE have been captured by them
 * black contains opponent pieces BLACK have been captured by them
*/
#define PIECE_COUNT_CAPTURABLE_PER_PLAYER 15 // 2*8 - 1
typedef struct {
    piece_e white[PIECE_COUNT_CAPTURABLE_PER_PLAYER];
    unsigned int white_n;
    piece_e black[PIECE_COUNT_CAPTURABLE_PER_PLAYER];
    unsigned int black_n;
} captured_t;

// initializes the board with the default configuration of pieces
void init_board(board_t *board);

// selects the player to currently play
// if it is the first round, it selects white
void select_player(player_e *player, unsigned int round_count);
        
// listens for a command to make a move by the currently playing player
bool get_move(move_t *move);

// performs the move if is it possible
end_condition_e perform_move(board_t *board, player_e player, captured_t *captured, move_t move);

// if there is one of the mates, end the game and show who has won
void announce_results(end_condition_e end_condition, player_e player);

// shows a guide to help players understand the move prompt system
void show_help();

#endif // CHESS_H