#include <stddef.h>
#include <stdint.h>
#include "vmm.h"
#include "hal/hal.h"
#include "bootinfo/bootinfo.h"
#include "pmm/pmm.h"

PgTable *KERNEL_CR3 = NULL;

PgTable *hal_vmm_current_cr3(void) {
  PgTable *cr3;
  asm volatile("mov %%cr3, %0" : "=r"(cr3));
  return cr3;
}

PgIndex hal_vmm_pageindex(uint64_t vaddr) {
  PgIndex ret;

  ret.pml4 = (vaddr >> 39) & 0x1ff;
  ret.pml3 = (vaddr >> 30) & 0x1ff;
  ret.pml2 = (vaddr >> 21) & 0x1ff;
  ret.pml1 = (vaddr >> 12) & 0x1ff;

  return ret;
}

uint64_t *hal_vmm_nexttable(uint64_t *table, uint64_t ent) {
  uint8_t *addr;

  if (table[ent] & HAL_PG_PRESENT) {
    addr = (uint8_t *)(table[ent] & ~((uint64_t)0xfff));
  } else {
    addr = pmm_alloc(1);
    hal_memset(BOOT_INFO.hhdm_off + addr, 0, HAL_PAGE_SIZE);
    table[ent] = (uint64_t)addr | HAL_PG_USER | HAL_PG_RW | HAL_PG_PRESENT;
  }

  return (uint64_t *)(BOOT_INFO.hhdm_off + addr);
}

void hal_vmm_map_page(PgTable *pml4, uint64_t virtaddr, uint64_t physaddr, uint32_t flags) {
  PgIndex pi = hal_vmm_pageindex(virtaddr);

  uint64_t *pml3 = hal_vmm_nexttable((uint64_t *)pml4, pi.pml4);
  uint64_t *pml2 = hal_vmm_nexttable((uint64_t *)pml3, pi.pml3);
  uint64_t *pml1 = hal_vmm_nexttable((uint64_t *)pml2, pi.pml2);
  uint64_t *pte = &pml1[pi.pml1];

  *pte = (physaddr & ~0xFFF) | (flags & 0x7);
}

void hal_vmm_unmap_page(PgTable *pml4, uint64_t virtaddr, uint64_t physaddr) {
  PgIndex pi = hal_vmm_pageindex(virtaddr);

  uint64_t *pml3 = hal_vmm_nexttable((uint64_t *)pml4, pi.pml4);
  uint64_t *pml2 = hal_vmm_nexttable((uint64_t *)pml3, pi.pml3);
  uint64_t *pml1 = hal_vmm_nexttable((uint64_t *)pml2, pi.pml2);
  uint64_t *pte = &pml1[pi.pml1];

  *pte &= ~HAL_PG_PRESENT;
}

void hal_vmm_init(void) {
  KERNEL_CR3 = hal_vmm_current_cr3();
}