#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));
        
        new_head->x = x;
        new_head->y = y;
        new_head->next = snake;
        return new_head;
}

struct snake* remove_snake(struct snake* snake){
   if (snake == NULL) {
        return NULL;
    }
    
    struct snake* current = snake;
    struct snake* p = NULL;
    
    while (current->next != NULL) {
        p = current;
        current = current->next;
    }
    
    free(current);
    
    if (p == NULL) {
        return NULL;
    }
    
    p->next = NULL;
    return snake;
}


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


int is_snake(struct snake* snake,int x,int y){
   struct snake* current = snake;
    while (current != NULL) {
        if (current->x == x && current->y == y) {
            return 1;
        }
        
        current = current->next;
    }
    return 0;
}


int step_state(struct state* st){
	int nx = (st->snake->x + st->sx);
    int ny = (st->snake->y + st->sy);
    if (new_head_x < 0 || new_head_x >= state->width || new_head_y < 0 || new_head_y >= state->height) {
        return END_WALL;
    }

    // Check if snake hit itself
    if (is_snake(state->snake, new_head_x, new_head_y)) {
        return END_SNAKE;
    }

    // Check if snake ate food
    int food_eaten = 0;
    for (int i = 0; i < FOOD_COUNT; i++) {
        if (state->foodx[i] >= 0 && state->foodx[i] == new_head_x && state->foody[i] == new_head_y) {
            state->foodx[i] = -1;
            state->foody[i] = -1;
            state->snake = add_snake(state->snake, new_head_x, new_head_y);
            food_eaten = 1;
            break;
        }
    }

    // Check if game ended
    if (!food_eaten) {
        int food_left = 0;
        for (int i = 0; i < FOOD_COUNT; i++) {
            if (state->foodx[i] >= 0) {
                food_left = 1;
                break;
            }
        }
        if (!food_left) {
            return END_FOOD;
        }
        // Remove the last snake part
        state->snake = remove_snake(state->snake);
        // Add new snake part
        state->snake = add_snake(state->snake, new_head_x, new_head_y);
    }

    return END_CONTINUE;
}