#define DEFAULT_ARENA_SIZE kilobytes(4)

arena_t	alloc_arena(u64 capacity)
{
	void *sys_alloc(u64 length);

	/* TODO(pryazha): Find reasonable maximum capacity through testing */
	assert(capacity <= (u64)gigabytes(16));

	if (!capacity)
		capacity = DEFAULT_ARENA_SIZE;

	/* TODO(pryazha): Use OS specific memory allocator
	 * (like VirtualAlloc on Windows or mmap on Linux)
	 */
	void *memory = sys_alloc(capacity);
	assert(memory);

	arena_t arena = {memory, capacity, 0};

	return arena;
}

void release_arena(arena_t *arena)
{
	void sys_free(void *memory, u64 length);

	assert(arena);
	sys_free(arena->memory, arena->capacity);
	arena->memory = 0;
	arena->capacity = 0;
	arena->used = 0;
}

void *push_arena(arena_t *arena, u64 size)
{
	assert(arena);
	assert(arena->used + size <= arena->capacity);
	void *memory = arena->memory + arena->used;
	arena->used += size;
	return memory;
}

void pop_arena(arena_t *arena, u64 size)
{
	assert(arena);
	arena->used -= min(size, arena->used);
}