#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 = 0;
    std::uint64_t numPages = 0;
    MemoryType type = MemoryType::USABLE;

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

struct AllocatePagesOptions
{
    std::size_t numPages = 1;
    bool bigPages = false;
};

struct PageRange
{
    std::uint64_t mBase = 0;
    std::uint64_t numPages = 0;

    explicit operator bool() const noexcept { return numPages > 0; }
    bool operator!() const noexcept { return numPages == 0; }

    [[nodiscard]] std::span<std::uint8_t> getMemory() const noexcept
    {
        std::uint8_t* basePtr = std::bit_cast<std::uint8_t*>(mBase << 12);
        return {basePtr, basePtr + (numPages * 512)};
    }
};

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

[[nodiscard]] PageRange allocatePages(const AllocatePagesOptions& options = {}) noexcept;

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>
[[nodiscard]] inline T* pageToPointer(std::uint64_t page) noexcept
{
    return std::bit_cast<T*>(page << 12);
}

[[nodiscard]] inline std::size_t bytesToPages(std::size_t bytes, bool bigPages = false) noexcept
{
    const std::size_t pageBytes = bigPages ? (2 << 20) : 4096;
    return (bytes + pageBytes - 1) / pageBytes;
}
}

void __ba_initInitialHeap() noexcept;

#endif // !defined(BAD_APPLE_OS_OS_MEMORY_HPP_INCLUDED)