#include "../libc/stdint.h"
#include "paging.h"
#include "../libc/stdio.h"
#include "system.h"
#include "kheap.h"


uint32_t *frames;
uint32_t nframes;

extern uint32_t placement_address;

#define INDEX_FROM_BIT(a) (a/(8*4))
#define OFFSET_FROM_BIT(a) (a%(8*4))

static void set_frame(uint32_t frame_addr)
{
	uint32_t frame = frame_addr/0x1000;
	uint32_t idx = INDEX_FROM_BIT(frame);
	uint32_t off = OFFSET_FROM_BIT(frame);
	frames[idx] |= (0x1 << off);
}

static void clear_frame(uint32_t frame_addr)
{
	uint32_t frame = frame_addr/0x1000;
	uint32_t idx = INDEX_FROM_BIT(frame);
	uint32_t off = OFFSET_FROM_BIT(frame);
	frames[idx] &= ~(0x1 << off);
}

/*
static uint32_t test_frame(uint32_t frame_addr)
{
   	uint32_t frame = frame_addr/0x1000;
   	uint32_t idx = INDEX_FROM_BIT(frame);
   	uint32_t off = OFFSET_FROM_BIT(frame);
   	return (frames[idx] & (0x1 << off));
}
*/

static uint32_t first_frame()
{
	uint32_t i, j;
	for (i=0; i<INDEX_FROM_BIT(nframes); i++)
	{
		if (frames[i] != 0xFFFFFFFF)
		{
			for (j=0; j<32; j++)
			{
				uint32_t toTest = 0x1 << j;
				if (!(frames[i]&toTest))
				{
					return i*4*8+j;
				}
			}
		}
	}
	return 0;
}

void alloc_frame(page_t *page, int is_kernel, int is_writeable)
{
	if (page->frame != 0)
	{
		return;
	} else {
		uint32_t idx = first_frame();
		if (idx == (uint32_t)-1)
		{
			panic();
		}
		set_frame(idx*0x1000);
		page->present = 1;
		page->rw = (is_writeable)?1:0;
		page->user = (is_kernel)?0:1;
		page->frame = idx;
	}
}

void free_frame(page_t *page)
{
	uint32_t frame;
	if (!(frame=page->frame))
	{
		return;
	} else {
		clear_frame(frame);
		page->frame = 0x0;
	}
}

void init_paging()
{
	uint32_t mem_end_page = 0x10000000;
	nframes = mem_end_page / 0x1000;
	frames = (uint32_t*)kmalloc(INDEX_FROM_BIT(nframes));
	memset(frames, 0, INDEX_FROM_BIT(nframes));

	page_directory_t* kernel_directory = (page_directory_t*)kmalloc_a(sizeof(page_directory_t));
	memset(kernel_directory, 0, sizeof(page_directory_t));
	//page_directory_t* current_directory = kernel_directory;

	unsigned int i = 0;
	while (i < placement_address)
	{
		alloc_frame(get_page(i, 1, kernel_directory), 0, 0);
		i += 0x1000;
	}

	irq_install_handler(14, page_fault);

	switch_page_directory(kernel_directory);	
}

void switch_page_directory(page_directory_t *dir)
{
	//page_directory_t* current_directory = dir;
	asm volatile("mov %0, %%cr3":: "r"(&dir->tablesPhysical));
	uint32_t cr0;
	asm volatile("mov %%cr0, %0": "=r"(cr0));
	cr0 |= 0x80000000;
	asm volatile("mov %0, %%cr0":: "r"(cr0));
}

page_t *get_page(uint32_t address, int make, page_directory_t *dir)
{
	address /= 0x1000;
	uint32_t table_idx = address / 1024;
	if (dir->tables[table_idx])
	{
		return &dir->tables[table_idx]->pages[address%1024];
	} else if (make)
	{
		uint32_t tmp;
		dir->tables[table_idx] = (page_table_t*)kmalloc_ap(sizeof(page_table_t), &tmp);
		memset(dir->tables[table_idx], 0, 0x1000);
		dir->tablesPhysical[table_idx] = tmp | 0x7;
		return &dir->tables[table_idx]->pages[address%1024];
	} else {
		return 0;
	}
	return 0;
}

void page_fault()
{
	puts("Page fault");
	panic();
}