#include "arch/x86_64/tables.h"
#include "arch/x86_64/processor.h"
#include "string.h"

static segment_descriptor_t s_gdt[] = {
    { 0 }, //Kernel NULL
    {      //Kernel Code
        .limit_0_15 = 0xFFFF,
        .base_0_15 = 0x0,
        .type = CD_SEGMENT_TYPE_CODE | CD_SEGMENT_TYPE_WRITEABLE,
        .s = 1,
        .dpl = 0,
        .p = 1,
        .limit_16_19 = 0xF,
        .avl = 0,
        .l = 1,
        .d_b = 0,
        .g = 1,
        .base_24_31 = 0x0
    },
    {      //Kernel Data
        .limit_0_15 = 0xFFFF,
        .base_0_15 = 0x0,
        .type = CD_SEGMENT_TYPE_WRITEABLE,
        .s = 1,
        .dpl = 0,
        .p = 1,
        .limit_16_19 = 0xF,
        .avl = 0,
        .l = 0,
        .d_b = 1,
        .g = 1,
        .base_24_31 = 0x0
    },
    { 0 }, //User NULL
    {      //User Data
        .limit_0_15 = 0xFFFF,
        .base_0_15 = 0x0,
        .type = CD_SEGMENT_TYPE_WRITEABLE,
        .s = 1,
        .dpl = 3,
        .p = 1,
        .limit_16_19 = 0xF,
        .avl = 0,
        .l = 0,
        .d_b = 1,
        .g = 1,
        .base_24_31 = 0x0
    },
    {      //User Code
        .limit_0_15 = 0xFFFF,
        .base_0_15 = 0x0,
        .type = CD_SEGMENT_TYPE_CODE | CD_SEGMENT_TYPE_WRITEABLE,
        .s = 1,
        .dpl = 3,
        .p = 1,
        .limit_16_19 = 0xF,
        .avl = 0,
        .l = 1,
        .d_b = 0,
        .g = 1,
        .base_24_31 = 0x0
    },
    {       //TSS Low
        .limit_0_15 = 0,
        .base_0_15 = 0,
        .base_16_23 = 0,
        .type = S_SEGMENT_TYPE_TSS_AVAIL,
        .avl = 0,
        .s = 0,
        .dpl = 0,
        .p = 1,
        .limit_16_19 = 0,
        .l = 0,
        .d_b = 0,
        .g = 0,
        .base_24_31 = 0
    },
    { 0 }   //TSS High
};

void
gdt_setup(processor_t *processor)
{
    memcpy(processor->gdt, s_gdt, sizeof(s_gdt));

    processor->gdtr.base = (uintptr_t)&s_gdt;
    processor->gdtr.length = sizeof(s_gdt) - 1;

    segment_descriptor_t *tss_lo = &processor->gdt[GDT_ENTRY_TSS_LOW];
    segment_descriptor_t *tss_hi = &processor->gdt[GDT_ENTRY_TSS_HIGH];

    uintptr_t tssb = (uintptr_t)&processor->tss;
    tss_lo->base_0_15 = tssb & 0xFFFF;
    tss_lo->base_16_23 = (tssb >> 16) & 0xFF;
    tss_lo->base_24_31 = (tssb >> 24) & 0xFF;
    tss_hi->limit_0_15 = (tssb >> 32) & 0xFFFF;
    tss_hi->base_0_15 = (tssb >> 48) & 0xFFFF;

    size_t tssl = sizeof(tss_t);
    tss_lo->limit_0_15 = tssl & 0xFFFF;
    tss_lo->limit_16_19 = (tssl >> 16) & 0xF;

    processor->tss.iopb = tssl;
    
    extern void gdt_load(void*);
    gdt_load(&processor->gdtr);

    extern void tss_flush(uint16_t);
    tss_flush(GDT_ENTRY_TSS_LOW * sizeof(segment_descriptor_t));
}