#pragma once

#include <stdint.h>

#define GDT_ADDRESS 0x00000800
#define GDT_SIZE 7

// https://wiki.osdev.org/Global_Descriptor_Table#Segment_Descriptor
struct gdt_entry
{
   uint16_t limit_low;
   uint16_t base_low;
   uint8_t base_middle;
   uint8_t  access;
   uint8_t  limit_high_and_flags;
   uint8_t  base_high;
} __attribute__((packed)) ;

// https://wiki.osdev.org/Global_Descriptor_Table#GDTR
struct gdt_descriptor {
    uint16_t size;
    uint32_t base;
} __attribute__((packed));

void initGdt();

#define GDT_FLAG_64BIT_MODE 0b0010
#define GDT_FLAG_32BIT_MODE 0b0100
#define GDT_FLAG_PAGE_MODE 0b1000
#define GDT_FLAG_BYTE_MODE 0b1000

#define GDT_ACCESS_P_VALID 0b10000000
#define GDT_ACCESS_DPL_KERNEL_MODE 0b00000000
#define GDT_ACCESS_DPL_USER_MODE   0b01100000
#define GDT_ACCESS_S_CODE_OR_DATA 0b00010000
#define GDT_ACCESS_S_SYSTEM_SEGMENT 0b00010000
#define GDT_ACCESS_E_EXECUTABLE 0b00001000
#define GDT_ACCESS_E_NOT_EXECUTABLE 0b00000000
#define GDT_ACCESS_DC_CONFORM 0b00000100 		// TODO UNDERSTAND THIS BIT
#define GDT_ACCESS_DC_NOT_CONFORM 0b00000000
#define GDT_ACCESS_RW_READABLE_FOR_CODE_WRITABLE_FOR_DATA 0b00000010
#define GDT_ACCESS_A_ACCESSED 0b00000001
#define GDT_ACCESS_A_NOT_ACCESSED 0b00000000