#include "paging.h"
#include "lib/bitset.h"
#include "lib/stdlib.h"
#include "monitor.h"
#include "mem.h"
#include "sys.h"

static struct bitset frames;

struct page_directory *kernel_pagedir, *current_pagedir;

/* ACCESSOR FUNCTIONS FOR STATIC BITSET */
uint32_t frame_alloc() {
	uint32_t free = bitset_firstFree(&frames);
	bitset_set(&frames, free);
	return free;
}

void frame_free(uint32_t id) {
	bitset_clear(&frames, id);
}


void paging_init(size_t totalRam) {
	uint32_t i;

	frames.size = totalRam / 0x1000;
	frames.bits = kmalloc(INDEX_FROM_BIT(frames.size));

	kernel_pagedir = kmalloc(sizeof(struct page_directory));
	kernel_pagedir->tablesPhysical = kmalloc_page(&kernel_pagedir->physicalAddr);
	for (i = 0; i < 1024; i++) {
		kernel_pagedir->tables[i] = 0;
		kernel_pagedir->tablesPhysical[i] = 0;
	}

	for (i = 0xE0000000; i < mem_placementAddr; i += 0x1000) {
		page_map(pagedir_getPage(kernel_pagedir, i, 1), frame_alloc(), 0, 0);
	}
	for (i = 0; i < (mem_placementAddr - 0xE0000000) / 0x100000; i++) {
		kernel_pagedir->tablesPhysical[i] = kernel_pagedir->tablesPhysical[i + 896];
		kernel_pagedir->tables[i] = kernel_pagedir->tables[i + 896];
	}

	monitor_write("Page dir is at: ");
	monitor_writeHex(kernel_pagedir->physicalAddr);
	pagedir_switch(kernel_pagedir);
	monitor_write("\nPaging started\n");
}

void paging_cleanup() {
	uint32_t i;
	for (i = 0; i < (mem_placementAddr - 0xE0000000) / 0x100000; i++) {
		kernel_pagedir->tablesPhysical[i] = 9;
		kernel_pagedir->tables[i] = 0;
	}
	monitor_write("Pages cleaned up\n");
}

void pagedir_switch(struct page_directory *pd) {
	current_pagedir = pd;
	asm volatile("mov %0, %%cr3" : : "r"(pd->physicalAddr));
	uint32_t cr0;
	asm volatile("mov %%cr0, %0" : "=r"(cr0));
	cr0 |= 0x80000000;
	asm volatile("mov %0, %%cr0" : : "r"(cr0));
}

uint32_t paging_fault(struct registers *regs) {
	size_t addr;
	asm volatile("mov %%cr2, %0" : "=r"(addr));
	monitor_write("PageFault ");
	if (regs->err_code & 0x1) monitor_write("present ");
	if (regs->err_code & 0x2) monitor_write("write ");
	if (regs->err_code & 0x4) monitor_write("user ");
	if (regs->err_code & 0x8) monitor_write("rsvd ");
	if (regs->err_code & 0x10) monitor_write("instructionfetch ");
	monitor_write("@"); monitor_writeHex(addr); monitor_write("\n");
	PANIC("Page fault");
	return 0;
}

struct page *pagedir_getPage(struct page_directory *pd, uint32_t address, int make) {
	address /= 0x1000;
	uint32_t table_idx = address / 1024;

	if (pd->tables[table_idx]) {
		return &pd->tables[table_idx]->pages[address %  1024];
	} else if (make) {
		pd->tables[table_idx] = kmalloc_page(pd->tablesPhysical + table_idx);
		memset((uint8_t*)pd->tables[table_idx], 0, 0x1000);
		pd->tablesPhysical[table_idx] |= 0x07;
		return &pd->tables[table_idx]->pages[address %  1024];
	} else {
		return 0;
	}
}

void page_map(struct page *page, uint32_t frame, uint32_t user, uint32_t rw) {
	if (page != 0 && page->frame == 0 && page->present == 0) {
		page->present = 1;
		page->rw = (rw ? 1 : 0);
		page->user = (user ? 1 : 0);
		page->frame = frame;
	}
}

void page_unmap(struct page *page) {
	if (page != 0) {
		page->frame = 0;
		page->present = 0;
	}
}

void page_unmapFree(struct page *page) {
	if (page != 0) {
		if (page->frame != 0) frame_free(page->frame);
		page->frame = 0;
		page->present = 0;
	}
}