//
// Created by snapshot112 on 10/15/25.
//

#define _POSIX_C_SOURCE 199309

#include "snake.h"

#include <ncurses.h>
#include <stdlib.h>
#include <time.h>
#include <pthread.h>
#include <unistd.h>

#include "grid_game_engine.h"

#define CELL_EMPTY ' '
#define CELL_FOOD '$'
#define CELL_WALL '#'
#define DIRECTION_COUNT 4
#define OFFSET_X 6
#define OFFSET_Y 3

typedef enum {
    SNAKE_MOVE = 0,
    SNAKE_EAT = 1,
    SNAKE_DIE = 2
} snake_action;

typedef enum {
    DIRECTION_UP = 0,
    DIRECTION_RIGHT = 1,
    DIRECTION_DOWN = 2,
    DIRECTION_LEFT = 3
} direction;

static direction PREVIOUS_DIRECTION = DIRECTION_DOWN;
static direction CURRENT_DIRECTION = DIRECTION_DOWN;
static coordinate SNAKE_HEAD;
static coordinate SNAKE_TAIL;
static coordinate MESSAGE_LOCATION = {0,0};
static int MAP_HEIGHT = 20;
static int MAP_WIDTH = 20;
static rooster *GRID;
static pthread_mutex_t MUTEX;

/*
 * Create a snake body part.
 *
 * Input:
 * dir: the direction the body part should point to.
 *
 * Output:
 * a character representing that bodypart.
 */
static char get_body_part(const direction dir) {
    return (char)dir + '0';
}

/*
 * Gets the direction of a body part.
 *
 * Input:
 * body_part: A part of the snake's body.
 *
 * Output:
 * The direction the next body part is pointing to.
 */
static direction get_body_part_direction(const char body_part) {
    return (direction)(body_part - '0');
}

/*
 * Create a grid for snake with a given height and width.
 *
 * Input:
 * height: The height of the map.
 * width:  The width of the map.
 *
 * Returns:
 * A pointer to the grid.
 */
static void create_grid(void) {
    const int grid_size = (MAP_WIDTH + 1) * MAP_HEIGHT + 1;
    char *map = malloc(grid_size * sizeof(char));
    if (map == NULL) {
        return;
    }

    for (int i = 1; i <= (MAP_WIDTH + 1) * MAP_HEIGHT; i++) {
        // Also subtract the null terminator
        int bottom_line = i > grid_size - (MAP_WIDTH + 2);
        int top_line = i < MAP_WIDTH + 1;

        int line_position = modulo(i, MAP_WIDTH + 1);

        int line_start = line_position == 1;
        int line_end = line_position == MAP_WIDTH;

        int newline = line_position == 0;

        if (newline) {
            map[i - 1] = '\n';
        } else if (top_line || bottom_line || line_start || line_end) {
            map[i - 1] = CELL_WALL;
        } else {
            map[i - 1] = CELL_EMPTY;
        }
    }

    map[grid_size - 1] = '\0';

    GRID = grid_from_string(map);
    free(map);

    rooster_plaats(GRID, rooster_breedte(GRID) / 2, rooster_hoogte(GRID) / 2, get_body_part(CURRENT_DIRECTION));
}

/*
 *
 */
static void generate_food() {
    coordinate empty_spots[MAP_HEIGHT * MAP_WIDTH];

    // Usable as index when initialized like this.
    int available_spots = 0;

    for (int x = 0; x < MAP_WIDTH; x++) {
        for (int y = 0; y < MAP_HEIGHT; y++) {
            if (rooster_kijk(GRID, x, y) == CELL_EMPTY) {
                coordinate new_spot = {x, y};
                empty_spots[available_spots] = new_spot;
                available_spots++;
            }
        }
    }

    // Available spots will now be a counter.

    const coordinate food_location = empty_spots[modulo(rand(), available_spots)];

    rooster_plaats(GRID, food_location.x, food_location.y, CELL_FOOD);
}

/*
 * Setup the game(map)
 *
 * Output:
 * A pointer to the game grid.
 *
 * Side Effects:
 * Seed random with the current time.
 */
static void initialize(void) {
    srand(time(NULL));

    create_grid();

    if (GRID == NULL) {
        return;
    }

    CURRENT_DIRECTION = DIRECTION_DOWN;
    PREVIOUS_DIRECTION = DIRECTION_DOWN;

    // Set snake head and snake tail.
    rooster_zoek(GRID, get_body_part(CURRENT_DIRECTION), &SNAKE_HEAD.x, &SNAKE_HEAD.y);
    SNAKE_TAIL.x = SNAKE_HEAD.x;
    SNAKE_TAIL.y = SNAKE_HEAD.y;

    generate_food();

    if (SNAKE_HEAD.x == -1) {
        free(GRID);
        GRID = NULL;
        return;
    }

    MESSAGE_LOCATION.y = rooster_hoogte(GRID) + OFFSET_Y + 5;
    MESSAGE_LOCATION.x = OFFSET_X - 5 >= 0 ? OFFSET_X - 5 : 0;
}

/*
 * Checks what happens when the snake moves over a given char.
 *
 * Input:
 * c: The char to check.
 *
 * Returns:
 * The snake will move forward: 0
 * The snake will eat an apple: 1
 * The snake will die:          2
 */
static snake_action collision_check(char c) {
    if (c == CELL_EMPTY) {
        return SNAKE_MOVE;
    }

    if (c == CELL_FOOD) {
        return SNAKE_EAT;
    }

    return SNAKE_DIE;
}

static void update_snake(coordinate new_head, snake_action action) {
    if (action == SNAKE_DIE) {
        rooster_zet_toestand(GRID, STATE_VERLOREN);
        return;
    }

    if (action == SNAKE_MOVE) {
        coordinate new_tail = SNAKE_TAIL;

        switch (get_body_part_direction(rooster_kijk(GRID, SNAKE_TAIL.x, SNAKE_TAIL.y))) {
            case DIRECTION_UP:
                new_tail.y--;
                break;
            case DIRECTION_RIGHT:
                new_tail.x++;
                break;
            case DIRECTION_DOWN:
                new_tail.y++;
                break;
            case DIRECTION_LEFT:
                new_tail.x--;
                break;
        }

        rooster_plaats(GRID, SNAKE_TAIL.x, SNAKE_TAIL.y, CELL_EMPTY);
        SNAKE_TAIL = new_tail;
    }

    // New head placed after tail moves. It can occupy the empty space created by the tail moving.
    rooster_plaats(GRID, new_head.x, new_head.y, get_body_part(CURRENT_DIRECTION));
    SNAKE_HEAD = new_head;
    PREVIOUS_DIRECTION = CURRENT_DIRECTION;

    if (action == SNAKE_EAT) {
        generate_food();
    }
}

static void *snake_move(void *arg) {
    struct timespec timer;
    timer.tv_sec = 0;
    timer.tv_nsec = 250000000L;

    while (rooster_vraag_toestand(GRID) == STATE_AAN_HET_SPELEN) {
        nanosleep(&timer, NULL);
        pthread_mutex_lock(&MUTEX);
        coordinate new_head = SNAKE_HEAD;
        switch (CURRENT_DIRECTION) {
            case DIRECTION_UP:
                new_head.y--;
                break;
            case DIRECTION_RIGHT:
                new_head.x++;
                break;
            case DIRECTION_DOWN:
                new_head.y++;
                break;
            case DIRECTION_LEFT:
                new_head.x--;
                break;
        }

        snake_action action = collision_check(rooster_kijk(GRID, new_head.x, new_head.y));

        update_snake(new_head, action);
        show_grid_on_offset(GRID, OFFSET_X, OFFSET_Y);
        pthread_mutex_unlock(&MUTEX);
    }
    return NULL;
}

static void turn_snake(direction dir) {
    if ((direction)modulo(dir + 2, DIRECTION_COUNT) == PREVIOUS_DIRECTION
        && !same_coordinate(SNAKE_HEAD, SNAKE_TAIL)) {
        return;
    }
    rooster_plaats(GRID, SNAKE_HEAD.x, SNAKE_HEAD.y, get_body_part(dir));
    CURRENT_DIRECTION = dir;
    show_grid_on_offset(GRID, OFFSET_X, OFFSET_Y);
}

static void *play_snake(void *arg) {
    while (rooster_vraag_toestand(GRID) == STATE_AAN_HET_SPELEN) {
        timeout(1);
        int c = getch();
        pthread_mutex_lock(&MUTEX);
        switch (c) {
            case KEY_UP: // fallthrough
            case 'w':
            case 'W':
                turn_snake(DIRECTION_UP);
                break;
            case KEY_DOWN: // fallthrough
            case 's':
            case 'S':
                turn_snake(DIRECTION_DOWN);
                break;
            case KEY_LEFT: // fallthrough
            case 'a':
            case 'A':
                turn_snake(DIRECTION_LEFT);
                break;
            case KEY_RIGHT: // fallthrough
            case 'd':
            case 'D':
                turn_snake(DIRECTION_RIGHT);
                break;
            case KEY_BACKSPACE:
                rooster_zet_toestand(GRID, STATE_QUIT);
                break;
        }
        pthread_mutex_unlock(&MUTEX);
    }
    return NULL;
}

//todo: ?? Win condition?
void snake(void) {
    initialize();
    if (GRID == NULL) {
        return;
    }

    // Created necessary threads.
    pthread_mutex_init(&MUTEX, NULL);
    pthread_t user_input;
    pthread_t game_tick;

    // Show game.
    erase();
    show_grid_on_offset(GRID, OFFSET_X, OFFSET_Y);
    mvaddstr(MESSAGE_LOCATION.y, MESSAGE_LOCATION.x, "Press SPACEBAR to start playing.");

    rooster_zet_toestand(GRID, STATE_AAN_HET_SPELEN);

    while (getch() != ' ') {}

    // Cleanup the start playing message.
    mvaddstr(MESSAGE_LOCATION.y, MESSAGE_LOCATION.x, "                                ");

    pthread_create(&user_input, NULL, play_snake, NULL);
    pthread_create(&game_tick, NULL, snake_move, NULL);

    // Wait until the gamestate is no longer STATE_AAN_HET_SPELEN
    pthread_join(game_tick, NULL);
    pthread_join(user_input, NULL);
    pthread_mutex_destroy(&MUTEX);

    rooster_klaar(GRID);
    graceful_exit();
}