#include <kernel/arch/generic.h>
#include <kernel/malloc.h>
#include <kernel/panic.h>
#include <kernel/util.h>
#include <shared/mem.h>
#include <stdbool.h>
#include <stdint.h>

#define MALLOC_MAGIC 0x616c6c6f63686472 /* "allochdr" */
#define DESCLEN 8

typedef struct Allocation Allocation;
struct Allocation {
	uint64_t magic;
	uint64_t len;
	Allocation *next, *prev;
	void *stacktrace[4];
	char desc[DESCLEN];
};

static Allocation *malloc_last = NULL;

static size_t
page_amt(size_t bytes)
{
	return (bytes + PAGE_SIZE - 1) / PAGE_SIZE;
}

void
mem_debugprint(void)
{
	size_t count = 0, bytes = 0, pages = 0;
	kprintf("[kern] current allocations:\n");
	for (Allocation *iter = malloc_last; iter; iter = iter->prev) {
		kprintf(
			"%08p %6dB %.8s ",
			((void*)iter) + sizeof(Allocation),
			iter->len - sizeof(Allocation),
			iter->desc
		);
		for (size_t i = 0; i < 4; i++) {
			kprintf(" k/%08x", iter->stacktrace[i]);
		}
		kprintf("\n");

		count++;
		bytes += iter->len;
		pages += page_amt(iter->len);
	}
	kprintf(
		"%d in total, %d bytes, %d pages = %dB used\n",
		count, bytes, pages, pages*PAGE_SIZE
	);
}

static void
kmalloc_sanity(const void *addr)
{
	assert(addr);
	const Allocation *hdr = addr - sizeof(Allocation);
	assert(hdr->magic == MALLOC_MAGIC);
	if (hdr->next) assert(hdr->next->prev == hdr);
	if (hdr->prev) assert(hdr->prev->next == hdr);
}

void *
kmalloc(size_t len, const char *desc)
{
	Allocation *hdr;
	void *addr;

	if (KMALLOC_MAX < len) {
		panic_invalid_state();
	}
	len += sizeof(Allocation);
	assert(len <= PAGE_SIZE);
	hdr = page_alloc(page_amt(len));
	hdr->magic = MALLOC_MAGIC;
	hdr->len = len;

	memset(hdr->desc, ' ', DESCLEN);
	if (desc) {
		for (int i = 0; i < DESCLEN; i++) {
			if (desc[i] == '\0') break;
			hdr->desc[i] = desc[i];
		}
	}

	hdr->next = NULL;
	hdr->prev = malloc_last;
	if (hdr->prev) {
		assert(!hdr->prev->next);
		hdr->prev->next = hdr;
	}

	for (size_t i = 0; i < 4; i++)
		hdr->stacktrace[i] = debug_caller(i);

	malloc_last = hdr;

	addr = (void*)hdr + sizeof(Allocation);
#ifndef NDEBUG
	memset(addr, 0xCC, len);
#endif
	kmalloc_sanity(addr);
	return addr;
}

void
kfree(void *ptr)
{
	Allocation *hdr;
	size_t len;
	if (ptr == NULL) return;

	kmalloc_sanity(ptr);
	hdr = ptr - sizeof(Allocation);
	len = hdr->len;

	if (hdr->next)
		hdr->next->prev = hdr->prev;
	if (hdr->prev)
		hdr->prev->next = hdr->next;
	if (malloc_last == hdr)
		malloc_last = hdr->prev;
#ifndef NDEBUG
	memset(hdr, 0xC0, len);
#else
	hdr->magic = ~MALLOC_MAGIC; /* (hopefully) detect double frees */
#endif
	page_free(hdr, page_amt(len));
}