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

typedef struct{
    unsigned char *buffer;
    size_t size;
    size_t offset;
}Arena;

Arena arena_create(size_t);
void* arena_alloc(Arena *, size_t);
void arena_destroy(Arena *);

int main(void){
    Arena  arena =  arena_create(13);
    int *ptrInt1 = (int*)arena_alloc(&arena, sizeof(int));
    int *ptrInt2 = (int*)arena_alloc(&arena, sizeof(int));
    float *ptrFloat1 = (float*)arena_alloc(&arena, sizeof(float));
    char *ptrChar1 = (char*)arena_alloc(&arena, sizeof(char));

    int need = sizeof(int)*2 + sizeof(float) + sizeof(char);

    printf("sizeof int: %d\n", (int)sizeof(int));
    printf("sizeof float: %d\n", (int)sizeof(float));
    printf("sizeof char: %d\n", (int)sizeof(char));

    printf("Necesitamos: %d\n", need);

    if(ptrInt1 != NULL){
        *ptrInt1 = 18;
        printf("Primer entero: %d\n", *ptrInt1);
    }
    if(ptrInt2 != NULL){
        *ptrInt2 = 27;
        printf("Segundo entero: %d\n", *ptrInt2);
    }
    if(ptrFloat1 != NULL){
        *ptrFloat1 = 3.1415f;
        printf("Primer flotante: %f\n", *ptrFloat1);
    }
    if(ptrChar1 != NULL){
        *ptrChar1 = 'L';
        printf("Primer char: %c\n", *ptrChar1);
    }

    arena_destroy(&arena);

    return 0;
}

Arena arena_create( size_t bytes){
    Arena new_arena = {
        .buffer = NULL,
        .size = bytes,
        .offset = 0
    };

    new_arena.buffer = (unsigned char *)malloc(bytes);

    if(new_arena.buffer == NULL){
        perror("Error asignando memoria");
        exit(1);
    }

    return new_arena;

}
void* arena_alloc(Arena *ref_arena, size_t bytes){

    if(ref_arena->buffer == NULL){
        return NULL;
    }

    if(ref_arena->offset + bytes > ref_arena->size){
        perror("Memoria llena\n");
        return NULL;
    }
    void* ptr_ref = ref_arena->buffer + ref_arena->offset;
    ref_arena->offset += bytes;
    return ptr_ref;
}

void arena_destroy(Arena *ref_arena){
    if(ref_arena->buffer != NULL){
        free(ref_arena->buffer);
        ref_arena->buffer = NULL;
    }
}