#pragma once
// mm_virt.h - virtual memory manager (VMM)
// Manages the single shared PML4, kernel pool, and user heap.
#include <stdint.h>
#include <stddef.h>
#include <mm_phys.h>
#include <ke_status.h>

// ---------------------------------------------------------------------------
// Page flags (x86-64 PTE bits)
// ---------------------------------------------------------------------------
#define PAGE_PRESENT   (1ULL << 0)
#define PAGE_WRITE     (1ULL << 1)
#define PAGE_USER      (1ULL << 2)
#define PAGE_NOCACHE   (1ULL << 4)
#define PAGE_NX        (1ULL << 63)

// ---------------------------------------------------------------------------
// Virtual address space constants
// ---------------------------------------------------------------------------
#define USER_BASE          0x0000000000001000ULL
#define USER_LIMIT         0x00007FFFFFFFF000ULL

#define KERNEL_BASE        0xFFFF800000000000ULL
#define PHYS_MAP_BASE      0xFFFF880000000000ULL
#define POOL_BASE          0xFFFFC00000000000ULL
#define POOL_LIMIT         0xFFFFE00000000000ULL

// ---------------------------------------------------------------------------
// Initialisation
// ---------------------------------------------------------------------------
// Called by KernelMain after MmInitializePhysical.
// bootPml4Phys: the PML4 set up by the bootloader.
// poolSize: initial reservation for kernel pool (bytes, page-aligned).
void    MmInitializeVirtual(PHYSICAL_ADDRESS bootPml4Phys, size_t poolSize);

// Install the shared PML4 into CR3. Called once at the end of KernelMain init.
void    MmActivate(void);

// ---------------------------------------------------------------------------
// Page mapping
// ---------------------------------------------------------------------------
KSTATUS MmMapPage(uintptr_t virt, PHYSICAL_ADDRESS phys, uint64_t flags);
KSTATUS MmUnmapPage(uintptr_t virt);

// Modify protection flags on an already-mapped virtual range.
// 'flags' is the complete new set of PAGE_* bits - it replaces the old flags
// entirely (except the physical address, which is preserved).
// Returns STATUS_NOT_FOUND if any page in the range is not mapped.
KSTATUS MmSetPageProtect(uintptr_t virt, size_t size, uint64_t flags);

// Walk the page tables to translate a virtual address to physical.
// Returns 0 if the address is not mapped.
PHYSICAL_ADDRESS MmGetPhysicalAddress(uintptr_t virt);

// ---------------------------------------------------------------------------
// Kernel pool - ring 0 only, never PAGE_USER.
// Best-fit free-list allocator, thread-safe via spinlock.
// ---------------------------------------------------------------------------
void* MmAllocatePool(size_t size);
void  MmFreePool(void* ptr);
void* MmReallocatePool(void* ptr, size_t newSize);

// ---------------------------------------------------------------------------
// User heap - shared flat space, ring 3 accessible.
// All allocations are PAGE_PRESENT | PAGE_WRITE | PAGE_USER.
// ---------------------------------------------------------------------------
void* MmAllocateUserMemory(size_t size);
void  MmFreeUserMemory(void* ptr, size_t size);
void* MmReallocateUserMemory(void* ptr, size_t newSize);

size_t MmGetKernelPoolUsage(void);
size_t MmGetUserHeapUsage(void);