#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <stdalign.h>

#include "wv_mem.h"
#include "wv_err.h"

#define WV_ALIGNMENT  alignof(max_align_t)
#define WV_ALIGN_MASK (WV_ALIGNMENT - 1)

#define WV_ARENA_MIN_SIZE  (256 * 1024)
#define WV_ARENA_RESERVED  WV_ALIGNMENT  /* Reserve 0 as the sentinel "null" ref */

struct wv_arena *wv_arena_create(size_t n)
{
	struct wv_arena *arena;

	if (n < WV_ARENA_MIN_SIZE)
		n = WV_ARENA_MIN_SIZE;

	arena = malloc(sizeof(struct wv_arena));
	if (!arena)
		err(1, "malloc arena struct");

	arena->buf = malloc(n);
	if (!arena->buf)
		err(1, "malloc arena buffer");

	arena->size = n;
	arena->offset = WV_ARENA_RESERVED;

	return arena;
}

wv_ref wv_arena_alloc(struct wv_arena *arena, size_t n)
{
	wv_ref ref;
	unsigned char *new_buf;
	size_t aligned_n, new_size;

	if (n == 0)
		errx(1, "wv_alloc: zero-size allocation");

	if (n > SIZE_MAX - WV_ALIGN_MASK)
		errx(1, "wv_alloc: allocation size overflow");

	aligned_n = (n + WV_ALIGN_MASK) & ~WV_ALIGN_MASK;

	if (aligned_n > SIZE_MAX - arena->offset)
		errx(1, "wv_alloc: arena offset overflow");

	if (arena->offset + aligned_n > arena->size) {
		new_size = arena->size;
		while (new_size < arena->offset + aligned_n) {
			if (new_size > SIZE_MAX / 2)
				errx(1, "wv_alloc: arena growth overflow");
			new_size *= 2;
		}

		new_buf = realloc(arena->buf, new_size);
		if (!new_buf)
			err(1, "realloc arena failed at %zu bytes", new_size);

		arena->buf  = new_buf;
		arena->size = new_size;
	}

	ref = (wv_ref)arena->offset;
	arena->offset += aligned_n;
	return ref;
}

void wv_arena_reset(struct wv_arena *arena)
{
	if (!arena)
		return;

	memset(arena->buf, 0, arena->offset);
	arena->offset = WV_ARENA_RESERVED;
}

void wv_arena_destroy(struct wv_arena *arena)
{
	if (!arena)
		return;

	free(arena->buf);
	free(arena);
}

wv_ref wv_arena_push_string(struct wv_arena *arena, const char *src, 
	size_t len)
{
	wv_ref ref = wv_arena_alloc(arena, len + 1);
	char *dst = (char *)WV_ADDR(arena, ref);
	memcpy(dst, src, len);
	dst[len] = '\0';
	return ref;
}