#include <stddef.h>
#include <stdint.h>
#include "vmm.h"
#include "hal/hal.h"
#include "bootinfo/bootinfo.h"
#include "pmm/pmm.h"
#include "paging.h"
#include "proc/proc.h"
#include "kprintf.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_map_range(PgTable *cr3, void *virtstart, void *physstart, size_t size, uint32_t flags) {
  if (size % HAL_PAGE_SIZE != 0 || (uint64_t)virtstart % HAL_PAGE_SIZE != 0 || (uint64_t)physstart % HAL_PG_PRESENT != 0) {
    return;
  }

  uint8_t *vaddr = virtstart, *paddr = physstart;

  for (; vaddr <= ((uint8_t *)virtstart + size); vaddr += HAL_PAGE_SIZE, paddr += HAL_PAGE_SIZE) {
    hal_vmm_map_page(cr3, (uint64_t)vaddr, (uint64_t)paddr, flags);
  }
}

void hal_vmm_unmap_range(PgTable *cr3, void *virtstart, void *physstart, size_t size) {
  if (size % HAL_PAGE_SIZE != 0 || (uint64_t)virtstart % HAL_PAGE_SIZE != 0 || (uint64_t)physstart % HAL_PG_PRESENT != 0) {
    return;
  }

  uint8_t *vaddr = virtstart, *paddr = physstart;

  for (; vaddr <= ((uint8_t *)virtstart + size); vaddr += HAL_PAGE_SIZE, paddr += HAL_PAGE_SIZE) {
    hal_vmm_unmap_page(cr3, (uint64_t)vaddr, (uint64_t)paddr);
  }
}

void hal_vmm_map_kern(PgTable *cr3) {
  PgTable *kcr3 = BOOT_INFO.hhdm_off + KERNEL_CR3;
  for (size_t i = 256; i < 512; i++) {
    cr3->ents[i] = kcr3->ents[i];
  }
}

void hal_vmm_switch_pd(PgTable *cr3) {
  hal_loadpd(cr3);
}

PgTable *hal_vmm_userproc_pml4(Proc *proc) {
  uint8_t *cr3 = pmm_alloc(1);
  PgTable *pml4 = (PgTable *)VIRT(cr3);
  hal_memset(pml4, 0, HAL_PAGE_SIZE);
  
  PgTable *kcr3 = VIRT(KERNEL_CR3);

  for (size_t i = 256; i < 512; i++) {
    pml4->ents[i] = kcr3->ents[i];
  }

  return (PgTable *)cr3;
}

void hal_vmm_init(void) {
  KERNEL_CR3 = hal_vmm_current_cr3();
  kprintf("KERNEL_CR3 = %p\n", KERNEL_CR3);
}