// http://www.brokenthorn.com/Resources/OSDev18.html

#include "kernel.h"
#include "x86.h"
#include "../lib/logger/log.h"	// logger facilities
#define FOOLOS_MODULE_NAME "vmem"


// TODO : why is the frame not 0xfffff??
enum PAGE_PTE_FLAGS {
 
    I86_PTE_PRESENT		=	1,		//0000000000000000000000000000001
    I86_PTE_WRITABLE		=	2,		//0000000000000000000000000000010
    I86_PTE_USER		=	4,		//0000000000000000000000000000100
    I86_PTE_WRITETHOUGH		=	8,		//0000000000000000000000000001000
    I86_PTE_NOT_CACHEABLE	=	0x10,		//0000000000000000000000000010000
    I86_PTE_ACCESSED		=	0x20,		//0000000000000000000000000100000
    I86_PTE_DIRTY		=	0x40,		//0000000000000000000000001000000
    I86_PTE_PAT			=	0x80,		//0000000000000000000000010000000
    I86_PTE_CPU_GLOBAL		=	0x100,		//0000000000000000000000100000000
    I86_PTE_LV4_GLOBAL		=	0x200,		//0000000000000000000001000000000
    I86_PTE_FRAME		=	0xFFFFF000 	//1111111111111111111000000000000
};

enum PAGE_PDE_FLAGS {
 
    I86_PDE_PRESENT		=	1,		//0000000000000000000000000000001
    I86_PDE_WRITABLE		=	2,		//0000000000000000000000000000010
    I86_PDE_USER		=	4,		//0000000000000000000000000000100
    I86_PDE_PWT			=	8,		//0000000000000000000000000001000
    I86_PDE_PCD			=	0x10,		//0000000000000000000000000010000
    I86_PDE_ACCESSED		=	0x20,		//0000000000000000000000000100000
    I86_PDE_DIRTY		=	0x40,		//0000000000000000000000001000000
    I86_PDE_4MB			=	0x80,		//0000000000000000000000010000000
    I86_PDE_CPU_GLOBAL		=	0x100,		//0000000000000000000000100000000
    I86_PDE_LV4_GLOBAL		=	0x200,		//0000000000000000000001000000000
    I86_PDE_FRAME		=	0xFFFFF000 	//1111111111111111111000000000000
};

//! page table entry
typedef uint32_t pt_entry;

//! a page directery entry
typedef uint32_t pd_entry;

////

//! virtual address
typedef uint32_t virtual_addr;
typedef uint32_t physical_addr;

typedef uint8_t bool;
 
//! i86 architecture defines 1024 entries per table--do not change
#define PAGES_PER_TABLE 1024
#define PAGES_PER_DIR	1024

#define PAGE_DIRECTORY_INDEX(x) (((x) >> 22) & 0x3ff)
#define PAGE_TABLE_INDEX(x) (((x) >> 12) & 0x3ff)
#define PAGE_GET_PHYSICAL_ADDRESS(x) (*x & ~0xfff)

//! page table represents 4mb address space
#define PTABLE_ADDR_SPACE_SIZE 0x400000

//! directory table represents 4gb address space
#define DTABLE_ADDR_SPACE_SIZE 0x100000000

//! page sizes are 4k
#define PAGE_SIZE 4096
 
//! page table
typedef struct ptable_struct {
 
    pt_entry m_entries[PAGES_PER_TABLE];
}ptable ;
 
//! page directory
typedef struct pdirectory_struct {
 
    pd_entry m_entries[PAGES_PER_DIR];
}pdirectory;

void pt_entry_add_attrib (pt_entry* e, uint32_t attrib)
{
    *e|=attrib;
}
void pt_entry_del_attrib (pt_entry* e, uint32_t attrib)
{
    *e&=~attrib;
}
void pt_entry_set_frame (pt_entry* e , physical_addr addr)
{
     //          *e = (*e & ~I86_PTE_FRAME) | addr;                               

    *e|=I86_PTE_FRAME&addr;

}
bool pt_entry_is_present (pt_entry e)
{
    return e&I86_PTE_PRESENT;
}

bool pt_entry_is_writable (pt_entry e)
{
    return e&I86_PTE_WRITABLE;
}

physical_addr pt_entry_pfn (pt_entry e)
{
    return e&I86_PTE_FRAME;
}

void		pd_entry_add_attrib (pd_entry* e, uint32_t attrib)
{
    *e|=attrib;
}

void		pd_entry_del_attrib (pd_entry* e, uint32_t attrib)
{
    *e&=~attrib;
}
void		pd_entry_set_frame (pd_entry* e, physical_addr add)
{
    *e|=I86_PDE_FRAME&add;
}
bool		pd_entry_is_present (pd_entry e)
{
    return e&I86_PDE_PRESENT;
}
/*
bool		pd_entry_is_user (pd_entry e)
{
    return 1;
}

bool		pd_entry_is_4mb (pd_entry e)
{
    return 1;
}
*/

bool		pd_entry_is_writable (pd_entry e)
{
    return e&I86_PDE_WRITABLE;
}

physical_addr	pd_entry_pfn (pd_entry e)
{
    return e&I86_PDE_FRAME;
}

/*
void		pd_entry_enable_global (pd_entry e)
{
}
*/

uint8_t vmmngr_alloc_page (pt_entry* e) 
{
 
	//! allocate a free physical frame
	void* p = pmmngr_alloc_block ();
	if (!p)
		return 0;
 
	//! map it to the page
	pt_entry_set_frame (e, (physical_addr)p);
	pt_entry_add_attrib (e, I86_PTE_PRESENT);

	return 1;
}

void vmmngr_free_page (pt_entry* e) 
{
    void* p = (void*)pt_entry_pfn (*e);
    if (p)
	pmmngr_free_block (p);
 
    pt_entry_del_attrib (e, I86_PTE_PRESENT);
}

pt_entry* vmmngr_ptable_lookup_entry (ptable* p, virtual_addr addr) 
{
 
    if (p)
	return &p->m_entries[ PAGE_TABLE_INDEX (addr) ];

    return 0;
}

// TODO !?  http://www.brokenthorn.com/Resources/OSDev18.html
void vmmngr_map_page (void* phys, void* virt) 
{

}

void vmem_init(uint32_t vesa_physbase)
{
    log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,"init paging (vesa base: 0x%08x)",vesa_physbase);

    ptable* table1 = (ptable*) pmmngr_alloc_block ();

    if (!table1)panic(FOOLOS_MODULE_NAME,"unable to alloc table1");
    log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,"table1: 0x%X",table1);
 
    ptable* table2 = (ptable*) pmmngr_alloc_block ();

    if (!table1)panic(FOOLOS_MODULE_NAME,"unable to alloc table2");
    log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,"table2: 0x%X",table2);

    // TODO: 3blocks? 
    pdirectory*	dir = (pdirectory*) pmmngr_alloc_block ();
    if (!dir)panic(FOOLOS_MODULE_NAME,"unable to alloc pdirectory");
    log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,"pdirectory: 0x%X",dir);

    //! map 1mb to 3gb (where we are at)
    for (int i=0, frame=vesa_physbase, virt=vesa_physbase; i<1024; i++, frame+=4096, virt+=4096) {

	//! create a new page
	pt_entry page=0;
	pt_entry_add_attrib (&page, I86_PTE_PRESENT);
	pt_entry_set_frame (&page, frame);

	//! ...and add it to the page table
	table1->m_entries [PAGE_TABLE_INDEX (virt) ] = page;
    }

    //! 1st 4mb are idenitity mapped
    for (int i=0, frame=0x0, virt=0x00000000; i<1024; i++, frame+=4096, virt+=4096) 
    {

	//! create a new page
	pt_entry page=0;
	pt_entry_add_attrib (&page, I86_PTE_PRESENT);
	pt_entry_set_frame (&page, frame);

	//! ...and add it to the page table
	table2->m_entries [PAGE_TABLE_INDEX (virt) ] = page;
    }

   
    pd_entry* entry = &dir->m_entries [PAGE_DIRECTORY_INDEX (vesa_physbase) ];
    *entry=0;
    pd_entry_add_attrib (entry, I86_PDE_PRESENT);
    pd_entry_add_attrib (entry, I86_PDE_WRITABLE);
    pd_entry_set_frame (entry, (physical_addr)table1);
    

    pd_entry* entry2 = &dir->m_entries [PAGE_DIRECTORY_INDEX (0x00000000) ];
    *entry2=0;
    pd_entry_add_attrib (entry2, I86_PDE_PRESENT);
    pd_entry_add_attrib (entry2, I86_PDE_WRITABLE);
    pd_entry_set_frame (entry2, (physical_addr)table2);


    x86_set_pdbr(dir);

    log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,"enabling paging...");
    x86_paging_enable();


}