#include "idt.h"
#include <stdint.h>

struct __attribute__((packed)) Pointer {
  uint16_t limit;
  uint32_t base;
};

enum Type {
  Null = 0,
  Intr = 0x8e /* 1000 1110  32-bit interrupt */
};

struct __attribute__((packed)) Gate_t {
  uint16_t offset_15_0;  /* segment offset low */
  uint16_t selector;     /* code segment selector */
  uint8_t __unused;      /* unused in protected mode */
  uint8_t type;          /* interrupt type */
  uint16_t offset_31_16; /* segment offset high */
};
/* _Static_assert(sizeof(struct Gate_t) == 8, "interrupt gate size"); */

void
Gate(struct Gate_t *entry, void (*f)(struct interrupt_frame *), uint16_t selector)
{
  uint32_t f_addr = (uint32_t)f;
  entry->offset_15_0 = f_addr & 0xffff;
  entry->offset_31_16 = (uint16_t)(f_addr >> 16) & 0xffff;
  entry->selector = selector;
  entry->__unused = 0;
  entry->type = Intr;
}

static struct Gate_t interrupt_table[256] __attribute((aligned(4096)));

void
idt_install()
{
  int i;
  const struct Pointer ptr = {sizeof(interrupt_table) - 1, (unsigned)&interrupt_table};

  /* exceptions 0x00~0x13 */
  for (i = 0; i <= 0x13; ++i) Gate(&interrupt_table[i], &abort_handler, 0x10);

  /* irq 0x20~0x2f */
  for (i = 0x22; i <= 0x2f; ++i) Gate(&interrupt_table[i], &abort_handler, 0x10);
  Gate(&interrupt_table[0x20], &irq0x00, 0x10);
  Gate(&interrupt_table[0x21], &irq0x01, 0x10);
  Gate(&interrupt_table[0x2c], &irq0x0c, 0x10);

  /* syscall 0x80 */
  Gate(&interrupt_table[0x80], &syscall_handler, 0x10);

  __asm__("lidt (%0)" : : "a"(&ptr));
}