#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <termios.h>
#include <time.h>
#include <unistd.h>

#define D_INVALID -1
#define D_UP       1
#define D_DOWN     2
#define D_RIGHT    3
#define D_LEFT     4

const long values[] = {
    0, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048
};

const char *colors[] = {
    "39", "31", "32", "33", "34", "35", "36", "37", "91", "92", "93", "94"
};

struct gamestate_struct__ {
    int grid[4][4];
    int have_moved;
    long total_score;
    long score_last_move;
    int blocks_in_play;
} game;

struct termios oldt, newt;

void do_draw(void)
{
    printf("\033[2J\033[HScore: %ld", game.total_score);
    if (game.score_last_move)
        printf(" (+%ld)", game.score_last_move);
    printf("\n");

    for (int i = 0; i < 25; ++i)
        printf("-");
    printf("\n");

    for (int y = 0; y < 4; ++y) {
        printf("|");
        for (int x = 0; x < 4; ++x) {
            if (game.grid[x][y])
                printf("\033[7m\033[%sm%*zd \033[0m|", colors[game.grid[x][y]],
                        4, values[game.grid[x][y]]);
            else
                printf("%*s |", 4, "");
        }
        printf("\n");
    }

    for (int i = 0; i < 25; ++i) {
        printf("-");
    }
    printf("\n");
}

void do_merge(int d)
{
/* These macros look pretty scary, but mainly demonstrate some space saving */
#define MERGE_DIRECTION(_v1, _v2, _xs, _xc, _xi, _ys, _yc, _yi, _x, _y)     \
    do {                                                                    \
        for (int _v1 = _xs; _v1 _xc; _v1 += _xi) {                          \
            for (int _v2 = _ys; _v2 _yc; _v2 += _yi) {                      \
                if (game.grid[x][y] && (game.grid[x][y] ==                  \
                                    game.grid[x + _x][y + _y])) {           \
                    game.grid[x][y] += (game.have_moved = 1);               \
                    game.grid[x + _x][y + _y] = (0 * game.blocks_in_play--);\
                    game.score_last_move += values[game.grid[x][y]];        \
                    game.total_score += values[game.grid[x][y]];            \
                }                                                           \
            }                                                               \
        }                                                                   \
    } while (0)

    game.score_last_move = 0;

    switch (d) {
        case D_LEFT:
            MERGE_DIRECTION(x, y, 0, < 3, 1, 0, < 4, 1, 1, 0);
            break;
        case D_RIGHT:
            MERGE_DIRECTION(x, y, 3, > 0, -1, 0, < 4, 1, -1, 0);
            break;
        case D_DOWN:
            MERGE_DIRECTION(y, x, 3, > 0, -1, 0, < 4, 1, 0, -1);
            break;
        case D_UP:
            MERGE_DIRECTION(y, x, 0, < 3, 1, 0, < 4, 1, 0, 1);
            break;
    }

#undef MERGE_DIRECTION
}

void do_gravity(int d)
{
#define GRAVITATE_DIRECTION(_v1, _v2, _xs, _xc, _xi, _ys, _yc, _yi, _x, _y) \
    do {                                                                    \
        int break_cond = 0;                                                 \
        while (!break_cond) {                                               \
            break_cond = 1;                                                 \
            for (int _v1 = _xs; _v1 _xc; _v1 += _xi) {                      \
                for (int _v2 = _ys; _v2 _yc; _v2 += _yi) {                  \
                    if (!game.grid[x][y] && game.grid[x + _x][y + _y]) {    \
                        game.grid[x][y] = game.grid[x + _x][y + _y];        \
                        game.grid[x + _x][y + _y] = break_cond = 0;         \
                        game.have_moved = 1;                                \
                    }                                                       \
                }                                                           \
            }                                                               \
            do_draw(); usleep(40000);                                       \
        }                                                                   \
    } while (0)

    switch (d) {
        case D_LEFT:
            GRAVITATE_DIRECTION(x, y, 0, < 3, 1, 0, < 4, 1, 1, 0);
            break;
        case D_RIGHT:
            GRAVITATE_DIRECTION(x, y, 3, > 0, -1, 0, < 4, 1, -1, 0);
            break;
        case D_DOWN:
            GRAVITATE_DIRECTION(y, x, 3, > 0, -1, 0, < 4, 1, 0, -1);
            break;
        case D_UP:
            GRAVITATE_DIRECTION(y, x, 0, < 3, 1, 0, < 4, 1, 0, 1);
            break;
    }

#undef GRAVITATE_DIRECTION
}

int do_check_end_condition(void)
{
    int ret = -1;
    for (int x = 0; x < 4; ++x) {
        for (int y = 0; y < 4; ++y) {
            if (values[game.grid[x][y]] == 2048)
                return 1;
            if (!game.grid[x][y] ||
                  ((x + 1 < 4) && (game.grid[x][y] == game.grid[x + 1][y])) ||
                  ((y + 1 < 4) && (game.grid[x][y] == game.grid[x][y + 1])))
                ret = 0;
        }
    }
    return ret;
}

int do_tick(int d)
{
    game.have_moved = 0;
    do_gravity(d);
    do_merge(d);
    do_gravity(d);
    return game.have_moved;
}

void do_newblock(void) {
    if (game.blocks_in_play >= 16) return;

    int bn = rand() % (16 - game.blocks_in_play);
    int pn = 0;

    for (int x = 0; x < 4; ++x) {
        for (int y = 0; y < 4; ++y) {
            if (game.grid[x][y])
                continue;

            if (pn == bn){
                game.grid[x][y] = rand() % 10 ? 1 : 2;
                game.blocks_in_play += 1;
                return;
            }
            else {
                ++pn;
            }
        }
    }
}

int main(void)
{
    /* Initialize terminal settings */
    tcgetattr(STDIN_FILENO, &oldt);
    newt = oldt;
    newt.c_lflag &= ~(ICANON | ECHO);
    tcsetattr(STDIN_FILENO, TCSANOW, &newt);

    srand(time(NULL));
    memset(&game, 0, sizeof(game));
    do_newblock();
    do_newblock();
    do_draw();

    while (1) {
        int found_valid_key, direction, value;
        do {
            found_valid_key = 1;
            direction       = D_INVALID;
            value           = getchar();
            switch (value) {
                case 'h': case 'a':
                    direction = D_LEFT;
                    break;
                case 'l': case 'd':
                    direction = D_RIGHT;
                    break;
                case 'j': case 's':
                    direction = D_DOWN;
                    break;
                case 'k': case 'w':
                    direction = D_UP;
                    break;
                case 'q':
                    goto game_quit;
                    break;
                case 27:
                    if (getchar() == 91) {
                        value = getchar();
                        switch (value) {
                            case 65:
                                direction = D_UP;
                                break;
                            case 66:
                                direction = D_DOWN;
                                break;
                            case 67:
                                direction = D_RIGHT;
                                break;
                            case 68:
                                direction = D_LEFT;
                                break;
                            default:
                                found_valid_key = 0;
                                break;
                        }
                    }
                    break;
                default:
                    found_valid_key = 0;
                    break;
            }
        }  while (!found_valid_key);

        do_tick(direction);
        if (game.have_moved != 0){
                do_newblock();
        }
        do_draw();

        switch (do_check_end_condition()) {
            case -1:
                goto game_lose;
            case 1:
                goto game_win;
            case 0:
                break;
        }
    }

    if (0)
game_lose:
    printf("You lose!\n");
    goto game_quit;
    if (0)
game_win:
    printf("You win!\n");
    goto game_quit;
    if (0)
game_quit:

    /* Restore terminal settings */
    tcsetattr(STDIN_FILENO, TCSANOW, &oldt);
    return 0;
}