//    PhoeniX OS Pagetable subsystem
//    Copyright © 2017 Yury Popov a.k.a. PhoeniX

#pragma once
#include "kernlib.hpp"

class Pagetable {
 public:
  struct Entry {
    union {
      struct {
        bool present :1;
        bool readwrite :1;
        bool user :1;
        bool writethrough :1;
        bool disablecache :1;
        bool accessed :1;
        bool dirty :1;
        bool size :1;
      } PACKED;
      uint8_t flags;
    } PACKED;
    bool rsvd:1;
    uint8_t avl :3;
    uintptr_t _ptr :51;
    uint8_t nx :1;

    uintptr_t getUintPtr() { return _ptr << 12; }
    void *getPtr() { return reinterpret_cast<void*>(getUintPtr()); }
    Entry *getPTE() { return static_cast<Entry*>(getPtr()); }

    Entry(): flags(0), rsvd(0), avl(0), _ptr(0), nx(0) {}
    Entry(uintptr_t ptr, uint8_t avl, uint8_t flags):
      flags(flags), rsvd(0), avl(avl), _ptr(ptr >> 12), nx(0) {}
    Entry(uintptr_t ptr, uint8_t flags):
      flags(flags), rsvd(0), avl(0), _ptr(ptr >> 12), nx(0) {}
    Entry(const void *ptr, uint8_t avl, uint8_t flags):
      flags(flags), rsvd(0), avl(avl), _ptr(uintptr_t(ptr) >> 12), nx(0) {}
    Entry(const void *ptr, uint8_t flags):
      flags(flags), rsvd(0), avl(0), _ptr(uintptr_t(ptr) >> 12), nx(0) {}

    static Entry* find(uintptr_t ptr, Entry *pagetable) {
      uint16_t ptx = (ptr >> (12 + 9 + 9 + 9)) & 0x1FF;
      uint16_t pdx = (ptr >> (12 + 9 + 9)) & 0x1FF;
      uint16_t pdpx = (ptr >> (12 + 9)) & 0x1FF;
      uint16_t pml4x = (ptr >> (12)) & 0x1FF;

      Entry *pde = pagetable[ptx].present ? pagetable[ptx].getPTE() : nullptr;
      if (pde == nullptr) return nullptr;
      Entry *pdpe = pde[pdx].present ? pde[pdx].getPTE() : nullptr;
      if (pdpe == nullptr) return nullptr;
      Entry *page = pdpe[pdpx].present ? pdpe[pdpx].getPTE() : nullptr;
      if (page == nullptr) return nullptr;

      return &page[pml4x];
    }
    static Entry* find(const void *addr, Entry *pagetable) {
      return find(uintptr_t(addr), pagetable);
    }
  } PACKED;

 private:
  static const size_t rsvd_num = 16;
  static void* rsvd_pages[rsvd_num];
  static Mutex page_mutex;
  static uint64_t last_page;
  static void* _alloc(bool low, size_t count);
  static void* _map(const void* addr);
  static void* _getRsvd();
  static void _renewRsvd();
  static void init();

 public:
  static void* map(const void* mem);
  static void* alloc(size_t count = 1);
  static void* lowalloc(size_t count = 1);
  static void free(void* page);
};

inline static void MmioWrite32(void *p, uint32_t data) {
  Pagetable::map(p);
  *reinterpret_cast<volatile uint32_t *>(p) = data;
}
inline static uint32_t MmioRead32(const void *p) {
  Pagetable::map(p);
  return *reinterpret_cast<const volatile uint32_t *>(p);
}