#pragma once

#if !defined(BAD_APPLE_OS_OS_MEMORY_HPP_INCLUDED)
#define BAD_APPLE_OS_OS_MEMORY_HPP_INCLUDED

#include <bit>
#include <cstdint>
#include <span>

extern "C" int gKernelStart;
extern "C" int gKernelEnd;

namespace baos
{
struct PageTableEntry
{
    bool present : 1;
    bool writable : 1;
    bool user : 1;
    bool writeThrough : 1;
    bool cacheDisabled : 1;
    bool accessed : 1;
    bool dirty : 1;
    bool pageSize : 1;
    bool global : 1;
    std::uint8_t avl : 3;
    std::uint64_t address : 40;
    std::uint16_t avl2 : 11;
    bool executeDisable : 1;
};

enum class MemoryType
{
    USABLE,
    UNUSABLE,
    MMIO,
    RESERVED
};

struct MemoryRange
{
    std::uint64_t pageBase;
    std::uint64_t numPages;
    MemoryType type = MemoryType::USABLE;

    MemoryRange& operator=(const MemoryRange&) noexcept = default;
    bool operator<(const MemoryRange& other) const noexcept
    {
        return pageBase < other.pageBase;
    }
};

[[nodiscard]] bool setupPaging(std::span<const MemoryRange> memoryRanges) noexcept;
[[nodiscard]] const char* memoryTypeName(MemoryType type) noexcept;

[[nodiscard]] void* allocatePages(unsigned numConsecutive) noexcept;
[[nodiscard]] inline void* allocatePage() noexcept { return allocatePages(1); }

void setupIdentityPaging(std::uint64_t page) noexcept;
void setupIdentityPaging2M(std::uint64_t page) noexcept;
void setupIdentityPaging(std::uint64_t firstPage, std::uint64_t lastPage) noexcept;

inline void identityMapRegion(void* start, std::size_t bytes) noexcept
{
    std::uint64_t firstPage = std::bit_cast<std::uint64_t>(start) / 4096;
    std::uint64_t lastPage = std::bit_cast<std::uint64_t>(static_cast<std::uint8_t*>(start) + bytes) / 4096 + 1;
    setupIdentityPaging(firstPage, lastPage);
}

template<typename T = void>
inline T* pageToPointer(std::uint64_t page) noexcept
{
    return std::bit_cast<T*>(page << 12);
}
}

void __ba_initInitialHeap() noexcept;

#endif // !defined(BAD_APPLE_OS_OS_MEMORY_HPP_INCLUDED)