#include "idt.h"
#include <stdint.h>
#include <stddef.h> /* for memset */

idt_entry_t idt_entries[256];
idt_ptr_t   idt_ptr;

extern void idt_load();

static void idt_set_gate(uint8_t num, uint32_t base, uint16_t sel, uint8_t flags)
{
    idt_entries[num].base_lo = base & 0xFFFF;
    idt_entries[num].base_hi = (base >> 16) & 0xFFFF;

    idt_entries[num].sel     = sel;
    idt_entries[num].always0 = 0;
    // We must uncomment the OR below when we get to using user-mode.
    // It sets the interrupt gate's privilege level to 3.
    idt_entries[num].flags   = flags /* | 0x60 */;
}

/* Note: memset implementation because we don't link with libc */
static void *memset(void *s, int c, size_t n)
{
    unsigned char *p = s;
    while(n--)
        *p++ = (unsigned char)c;
    return s;
}

void init_idt()
{
    idt_ptr.limit = sizeof(idt_entry_t) * 256 - 1;
    idt_ptr.base  = (uint32_t)&idt_entries;

    memset(&idt_entries, 0, sizeof(idt_entry_t) * 256);

    /* Determine valid flags:
     * 0x8E = 1000 1110
     * P=1, DPL=00, S=0 (System), Type=1110 (32-bit Interrupt Gate) */

    /* For now, just load the IDT without any entries to verify loading works without crashing.
       Later we will set up ISRs. */

    idt_load((uint32_t)&idt_ptr);
}