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

struct snake* add_snake (struct snake* snake, int x, int y) {
    struct snake* head = NULL;

    head = malloc(sizeof(struct snake));

    if (!head) {
        return snake;
    }    
        head->x = x;
        head->y = y;

        head->next = NULL;

        if (snake !=NULL) {
            head->next = snake;
        }
        return head;
}

struct snake* remove_snake(struct snake* snake) {
    if (snake == NULL) {
        return NULL;
    }

    if (snake->next == NULL) {
        free(snake);
        return NULL;
    }

    struct snake* temp = snake;
    while (temp->next->next != NULL) {
        temp = temp->next;
    }

    free(temp->next);
    temp->next = NULL;

    return snake;
}

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

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* state) {
    int x = state->snake->x + state->sx;
    int y = state->snake->y + state->sy;

    if (x < 0) return END_WALL;
    if (x >= state->width) return END_WALL;
    if (y < 0) return END_WALL;
    if (y >= state->height) return END_WALL;

    if (is_snake(state->snake, x, y)) {
        return END_SNAKE;
    }

    int food_found = -1;
    for (int idx = 0; idx < FOOD_COUNT; idx++) {
        if (state->foodx[idx] == x && state->foody[idx] == y) {
            food_found = idx;
            break;
        }
    }

    if (food_found != -1) {
        state->foodx[food_found] = -1;
        state->foody[food_found] = -1;
        state->snake = add_snake(state->snake, x, y);

        int remaining = 0;
        for (int k = 0; k < FOOD_COUNT; ++k) {
            remaining += (state->foodx[k] >= 0 && state->foody[k] >= 0);
        }

        if (remaining == 0) {
            return END_FOOD;
        }
        return END_CONTINUE;
    }

    state->snake = add_snake(state->snake, x, y);
    state->snake = remove_snake(state->snake);

    return END_CONTINUE;
}