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#include <system.h>
#include <paging.h>

// the main table
static page_table_t page_table __attribute__ ((aligned (4)));

// the main directory
static page_directory_t page_directory __attribute__ ((aligned (4)));


/**
 * Load the paging
 */
static inline void switch_page_directory(page_directory_t *dir)
{
    //current_directory = dir;
    asm volatile("mov %0, %%cr3":: "r"(dir->physicalAddr));
    uint32 cr0;
    asm volatile("mov %%cr0, %0": "=r"(cr0));
    cr0 |= 0x80000000; // Enable paging!
    asm volatile("mov %0, %%cr0":: "r"(cr0));
}


/**
 * Set up the paging
 */
void paging_install ()
{
    // set up pages for first 4MB
    uint32 address = 0;
    int i;
    for (i = 0; i < 1024; i++)
    {
        page_table.pages[i].frame   = address;
        page_table.pages[i].present = 1;
        page_table.pages[i].rw      = 1;
        page_table.pages[i].user    = 1;
        address += 0x1000;
    }

    // set up directory
    page_directory.physicalAddr = (uint32)page_directory.tablesPhysical;
    page_directory.tablesPhysical[0] = (((uint32)&page_table) << 12) | 0x7;

    for(i=1; i<1024; i++)
    {
         page_directory.tablesPhysical[i] = 0;
    };

    switch_page_directory(&page_directory);
}

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#ifndef PAGING_H_INCLUDED
#define PAGING_H_INCLUDED

#include <common.h>

/* the page */
typedef struct page
{
    uint32 present    : 1;   // Page present in memory
    uint32 rw         : 1;   // Read-only if clear, readwrite if set
    uint32 user       : 1;   // Supervisor level only if clear
    uint32 accessed   : 1;   // Has the page been accessed since last refresh?
    uint32 dirty      : 1;   // Has the page been written to since last refresh?
    uint32 unused     : 7;   // Amalgamation of unused and reserved bits
    uint32 frame      : 20;  // Frame address (shifted right 12 bits)
} page_t;

/* the table (consists of 1024 entries ) */
typedef struct page_table
{
    page_t pages[1024];
} page_table_t;

/* the directory */
typedef struct page_directory
{
    /**
       Array of pointers to pagetables.
    **/
    //page_table_t * tables[1024];

    /**
       Array of pointers to the pagetables above, but gives their *physical*
       location, for loading into the CR3 register.
    **/
    uint32 tablesPhysical[1024];

    /**
       The physical address of tablesPhysical. This comes into play
       when we get our kernel heap allocated and the directory
       may be in a different location in virtual memory.
    **/
    uint32 physicalAddr;
} page_directory_t;



#endif // PAGING_H_INCLUDED

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    gdt_install ();
    idt_install();
    isrs_install();
    irq_install();

    paging_install ();
    init_video();