#include "snake.h"
#include <stdlib.h>

struct snake* add_snake(struct snake* snake, int x, int y) {
    struct snake* new_head = (struct snake*)malloc(sizeof(struct snake));
    if (!new_head) {
        // Memory allocation failed
        return NULL;
    }
    new_head->x = x;
    new_head->y = y;
    new_head->next = snake;
    return new_head;
}

struct snake* remove_snake(struct snake* snake) {
    if (!snake) {
        // Snake is empty
        return NULL;
    }
    struct snake* new_head = snake->next;
    free(snake);
    return new_head;
}

int is_snake(struct snake* snake, int x, int y) {
    while (snake) {
        if (snake->x == x && snake->y == y) {
            return 1; // Found snake part at given coordinates
        }
        snake = snake->next;
    }
    return 0; // Snake part not found
}

void free_snake(struct snake* sn) {
    while (sn) {
        struct snake* temp = sn;
        sn = sn->next;
        free(temp);
    }
}

int step_state(struct state* state) {
    // Calculate new position of the snake head
    int new_x = state->snake->x + state->sx;
    int new_y = state->snake->y + state->sy;

    // Check if snake hits a wall
    if (new_x < 0 || new_x >= state->width || new_y < 0 || new_y >= state->height) {
        return END_WALL;
    }

    // Check if snake hits itself
    if (is_snake(state->snake->next, new_x, new_y)) {
        return END_SNAKE;
    }

    // Check if snake eats food
    int i;
    for (i = 0; i < FOOD_COUNT; i++) {
        if (state->foodx[i] == new_x && state->foody[i] == new_y) {
            // Food eaten, mark it as negative
            state->foodx[i] = -1;
            state->foody[i] = -1;
            // Add new snake part at the food position
            state->snake = add_snake(state->snake, new_x, new_y);
            if (state->snake == NULL) {
                // Memory allocation failed
                return END_USER;
            }
            // Check if no food left
            int food_left = 0;
            for (int j = 0; j < FOOD_COUNT; j++) {
                if (state->foodx[j] >= 0 && state->foody[j] >= 0) {
                    food_left = 1;
                    break;
                }
            }
            if (!food_left) {
                return END_FOOD; // No food left
            }
            return END_CONTINUE; // Food eaten, continue the game
        }
    }

    // Add new snake part on the new position and remove the last part of the snake
    state->snake = add_snake(state->snake, new_x, new_y);
    state->snake = remove_snake(state->snake->next);
    return END_CONTINUE;
}