#ifndef ARENA_H
#define ARENA_H

typedef enum {
    ARENA_ZERO     = 1 << 0,
    ARENA_SOFTFAIL = 1 << 1,
} arena_flags_t;

// More or less taken from https://nullprogram.com/blog/2023/09/27/
typedef struct {
    uint8_t *begin;
    uint8_t *end;
} arena_t;

arena_t arena_create(ptrdiff_t capacity)
{
    arena_t a = {0};
    a.begin = malloc(capacity);
    a.end = a.begin ? a.begin + capacity : 0;
    return a;
}


void *arena_alloc(arena_t *a, ptrdiff_t size, ptrdiff_t align, ptrdiff_t count, arena_flags_t flags)
{
    ptrdiff_t padding = -(uintptr_t)a->begin & (align - 1);
    ptrdiff_t available = a->end - a->begin - padding;
    if (available < 0 || count > available/size)
    {
        // TODO: Decide what to do on oom
        if (flags & ARENA_SOFTFAIL)
            return 0;
        else
            abort();
    }
    void *p = a->begin + padding;
    a->begin += padding + count*size;
    return flags & ARENA_ZERO ? p : memset(p, 0, count*size);
}

#define arena_reserve(arena, type, count, flags) (type *)arena_alloc(arena, sizeof(type), _Alignof(type), count, flags)

#define KB 1024
#define MB 1024*KB
#define GB 1024*MB

#endif