#include <arch/gdt.h>
#include <arch/tss.h>
#include <kernel/libc/string.h>
#include <kernel/types.h>
#include <stddef.h>

static void init_entry(struct gdt_entry *entry, int access, int flags)
{
	entry->ge_limit_low = 0xFFFF;
	entry->ge_base_low = 0x00;
	entry->ge_base_mid = 0x00;
	entry->ge_access = access;
	entry->ge_gran = flags;
	entry->ge_base_hi = 0x00;
}

int gdt_init(struct gdt *gdt, struct gdt_ptr *gdtp)
{
	memset(&gdt->g_entries[0], 0x0, sizeof gdt->g_entries[0]);

	init_entry(
		&gdt->g_entries[1],
		GDT_A_PRESENT | GDT_A_CODEREAD | GDT_A_CODE,
		GDT_F_64BIT);
	init_entry(
		&gdt->g_entries[2],
		GDT_A_PRESENT | GDT_A_DATAWRITE | GDT_A_DATA,
		GDT_F_64BIT);
	init_entry(
		&gdt->g_entries[3],
		GDT_A_PRESENT | GDT_A_USER | GDT_A_DATAWRITE | GDT_A_DATA,
		GDT_F_64BIT);
	init_entry(
		&gdt->g_entries[4],
		GDT_A_PRESENT | GDT_A_USER | GDT_A_CODEREAD | GDT_A_CODE,
		GDT_F_64BIT);

	gdtp->g_ptr = (uint64_t)gdt;
	gdtp->g_limit = sizeof(*gdt) - 1;

	return 0;
}

void gdt_write_tss(struct gdt *gdt, struct tss *tss)
{
	struct tss_gdt_entry *tss_entry = &gdt->g_tss;

	virt_addr_t base = (virt_addr_t)tss;
	size_t limit = sizeof *tss;

	tss_entry->ge_base_low = (base & 0xFFFF);
	tss_entry->ge_base_mid = (base >> 16) & 0xFF;
	tss_entry->ge_base_hi = (base >> 24) & 0xFF;
	tss_entry->ge_base_ext = (base >> 32) & 0xFFFFFFFF;
	tss_entry->ge_limit_low = (limit & 0xFFFF);
	tss_entry->ge_gran = (limit >> 16) & 0xF;
	tss_entry->ge_access = 0xE9;
	tss_entry->ge_reserved = 0;
}