#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>

#include "kprintf.h"
#include "memory.h"
#include "utils.h"

#define PT_SIZE         0x300
#define MAX_TLB_ENTRIES 32

extern uint32_t page_table_entries[PT_SIZE] __attribute__((aligned(4096)));

static int16_t find_next_block(size_t nb_pages)
{
	for (uint16_t i = 0; i < PT_SIZE; i++) {
		uint16_t j;
		for (j = 0;
		     page_table_entries[i + j] >> 12 == i + j && j < nb_pages;
		     j++)
			;
		if (j == nb_pages)
			return i;
		i += j;
	}
	return -1;
}

void *alloc_pages(size_t size)
{
	const uint32_t nb_pages = CEIL(size, PAGE_SIZE);
	const int16_t index = find_next_block(nb_pages);

	if (index < 0) {
		kprintf(KERN_CRIT "Not enough pages (max: %d)\n", PT_SIZE);
		return NULL;
	}
	for (size_t i = index; i - (size_t)index < nb_pages; i++) {
		void *frame = alloc_frames(PAGE_SIZE);
		if (!frame) {
			for (size_t j = index; j < i; j++)
				free_frames(
				    (void *)(page_table_entries[j] >> 12),
				    PAGE_SIZE);
			return NULL;
		}
		page_table_entries[i] = (uint32_t)frame << 12 | INIT_FLAGS;
	}
	return (void *)(page_table_entries[index] >> 12);
}

int free_pages(void *page_ptr, size_t size)
{
	const uint32_t nb_pages = CEIL(size, PAGE_SIZE);
	const uint32_t page_index = (uint32_t)page_ptr / PAGE_SIZE;

	if ((uint32_t)page_ptr > PT_SIZE * PAGE_SIZE) {
		kprintf(KERN_WARNING "Address out of range\n");
		return -1;
	} else if ((uint32_t)page_ptr % PAGE_SIZE) {
		kprintf(KERN_WARNING "Invalid address\n");
		return -1;
	} else if (page_index + nb_pages > PT_SIZE) {
		kprintf(KERN_WARNING "Invalid number of frames\n");
		return -1;
	}
	for (size_t i = page_index; i < page_index + nb_pages; i++) {
		free_frames((void *)(page_table_entries[i] >> 12), PAGE_SIZE);
		page_table_entries[i] = (i >> 12) | INIT_FLAGS;
	}
	return 0;
}