#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#include <ncurses.h>

enum {
    HEIGHT = 20,
    WIDTH = 10,
};

struct position {
    int x;
    int y;
};

struct rotation {
    struct position tiles[4];
};

struct brick {
    struct rotation *states;
    int rotation;
    struct position position;
};

/************************
 * Templates for bricks *
 ************************/

/* T Brick */
struct rotation t_brick_rotations[4] = {
    { /* first rotation */
        .tiles = {
            {.x = 2, .y = 0},
            {.x = 1, .y = 1},
            {.x = 2, .y = 1},
            {.x = 2, .y = 2}
        }
    },
    { /* second rotation */
        .tiles = {
            {.x = 2, .y = 0},
            {.x = 1, .y = 1},
            {.x = 2, .y = 1},
            {.x = 3, .y = 1}
        }
    },
    { /* third rotation */
        .tiles = {
            {.x = 2, .y = 0},
            {.x = 2, .y = 1},
            {.x = 3, .y = 1},
            {.x = 2, .y = 2}
        }
    },
    { /* fourth rotation */
        .tiles = {
            {.x = 1, .y = 1},
            {.x = 2, .y = 1},
            {.x = 3, .y = 1},
            {.x = 2, .y = 2}
        }
    },

};

enum input {
    I_NONE,
    I_QUIT,
    I_LEFT,
    I_RIGHT,
    I_DROP,
    I_ROTATE,
};

struct game_state {
    char running;
    char grid[WIDTH][HEIGHT];
    struct brick current_brick;
    enum input input;
    unsigned int tick;
};

struct game_state construct_game_state();

struct brick spawn_brick();

int gravitate_brick(struct game_state *game_state);

/* (optional) drop brick */

/* check for full line */

/* remove full line */

int brick_collides_x(struct brick brick);

int brick_collides_y(struct brick brick);

int brick_collides_grid(struct brick brick, struct game_state game_state);

void move_brick(struct brick *brick, int direction);

void rotate_brick(struct brick *brick);

enum input get_input();

void evaluate_input(struct game_state *game_state, enum input input);

/* brick to grid */
void brick_to_grid(struct brick brick, struct game_state *game_state);

/* loose condition */

void draw_game_state(struct game_state game_state);

int brick_on_position(int x, int y, struct brick brick);

int main(void) {
    initscr();
    noecho();
    nodelay(stdscr, TRUE);
    struct game_state game_state = construct_game_state();
    while (game_state.running) {
        game_state.tick++;
        draw_game_state(game_state);
        enum input input = get_input();
        evaluate_input(&game_state, input);
        if (game_state.tick % 10 == 0) {
            int brick_fell = gravitate_brick(&game_state);
            if (!brick_fell) {
                game_state.current_brick = spawn_brick();
            }
        }
        usleep(100000);
    }
    endwin();
}

struct game_state construct_game_state() {
    struct game_state game_state = {
        .running = 1,
        .grid = {0},
        .current_brick = spawn_brick(),
        .tick = 0,
    };
    return game_state;
}

struct brick spawn_brick() {
    struct brick brick = {
        .states = t_brick_rotations,
        .rotation = 0,
        .position = {.x = 3, .y=0}
    };
    return brick;
}

void draw_game_state(struct game_state game_state) {
    clear();
    for (int y = 0; y < HEIGHT; ++y) {
        printw("|");
        for (int x = 0; x < WIDTH; ++x) {
            if (game_state.grid[x][y]
                    || brick_on_position(x, y, game_state.current_brick)) {
                printw("O");
            } else {
                printw(" ");
            }
        }
        printw("|\n");
    }
    printw("|");
    for (int x = 0; x < WIDTH; ++x) {
        printw("-");
    }
    printw("|\n");
}

int brick_on_position(int x, int y, struct brick brick) {
    x -= brick.position.x;
    y -= brick.position.y;
    struct rotation *rotation = &brick.states[brick.rotation];
    for (int i = 0; i < 4; ++i) {
        if (rotation->tiles[i].x == x && rotation->tiles[i].y == y) {
            return 1;
        }
    }
    return 0;
}

enum input get_input() {
    char in = getch();
    switch (in) {
        case 'w':
            return I_ROTATE;
        case 'q':
            return I_QUIT;
        case 'a':
            return I_LEFT;
        case 'd':
            return I_RIGHT;
        case 's':
            return I_DROP;
        default:
            return I_NONE;
    }
}

void evaluate_input(struct game_state *game_state, enum input input) {
    switch (input) {
        case I_ROTATE:
            rotate_brick(&game_state->current_brick);
            break;
        case I_QUIT:
            game_state->running = false;
            break;
        case I_LEFT:
            move_brick(&game_state->current_brick, -1);
            break;
        case I_RIGHT:
            move_brick(&game_state->current_brick, 1);
            break;
        case I_DROP:
            while(gravitate_brick(game_state)) {
                /* void */
            }
            break;
        default:
            break;
    }
}

void rotate_brick(struct brick *brick) {
    brick->rotation++;
    brick->rotation %= 4;
    if (brick_collides_x(*brick)) {
        /* for real module, do +4 and -1 */
        brick->rotation += 3;
        brick->rotation %= 4;
    }
}

void move_brick(struct brick *brick, int direction) {
    brick->position.x += direction;
    if (brick_collides_x(*brick)) {
        brick->position.x -= direction;
    }
}

int brick_collides_x(struct brick brick) {
    for (int i = 0; i < 4; ++i) {
        struct position tile_pos = brick.states[brick.rotation].tiles[i];
        tile_pos.x += brick.position.x;
        if (tile_pos.x > WIDTH - 1 || tile_pos.x < 0) {
            return 1;
        }
    }
    return 0;
}

int brick_collides_y(struct brick brick) {
    for (int i = 0; i < 4; ++i) {
        struct position tile_pos = brick.states[brick.rotation].tiles[i];
        tile_pos.y += brick.position.y;
        if (tile_pos.y > HEIGHT - 1) {
            return 1;
        }
    }
    return 0;
}

int brick_collides_grid(struct brick brick, struct game_state game_state) {
    for (int i = 0; i < 4; ++i) {
        struct position tile_pos = brick.states[brick.rotation].tiles[i];
        tile_pos.x += brick.position.x;
        tile_pos.y += brick.position.y;
        if (game_state.grid[tile_pos.x][tile_pos.y]) {
            return 1;
        }
    }
    return 0;
}

int gravitate_brick(struct game_state *game_state) {
    game_state->current_brick.position.y++;
    if (brick_collides_grid(game_state->current_brick, *game_state)
            || brick_collides_y(game_state->current_brick)) {
        game_state->current_brick.position.y--;
        brick_to_grid(game_state->current_brick, game_state);
        return 0;
    }
    return 1;
}

void brick_to_grid(struct brick brick, struct game_state *game_state) {
    for (int i = 0; i < 4; ++i) {
        struct position tile_pos = brick.states[brick.rotation].tiles[i];
        tile_pos.x += brick.position.x;
        tile_pos.y += brick.position.y;
        game_state->grid[tile_pos.x][tile_pos.y] = 1;
    }
}