// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
// SPDX-License-Identifier: GPL-3.0-or-later

// SPDX-FileCopyrightText: Copyright 2019 yuzu Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later

#pragma once

#include <memory>
#include <optional>

#ifndef _WIN32
#include <unistd.h>
#endif

#include "common/common_funcs.h"
#include "common/common_types.h"

namespace Common {

#if !defined(ARCHITECTURE_x86_64) && !defined(__WIN32)
const u64 HostPageSize = sysconf(_SC_PAGESIZE);
const u64 HostPageBits = std::countr_zero(HostPageSize);
const u64 HostPageMask = ~(HostPageSize - 1);
const u64 GuestHostAlignment = HostPageSize / 0x1000;
#else
constexpr u64 HostPageSize = 0x1000;
constexpr u64 HostPageBits = 12;
constexpr u64 HostPageMask = ~(HostPageSize - 1);
constexpr u64 GuestHostAlignment = 1;
#endif

constexpr u64 HugePageSize = 0x200000;

enum class MemoryPermission : u32 {
    Read = 1 << 0,
    Write = 1 << 1,
    ReadWrite = Read | Write,
    Execute = 1 << 2,
};
DECLARE_ENUM_FLAG_OPERATORS(MemoryPermission)

/**
 * A low level linear memory buffer, which supports multiple mappings
 * Its purpose is to rebuild a given sparse memory layout, including mirrors.
 */
class HostMemory {
public:
    explicit HostMemory(size_t backing_size_, size_t virtual_size_);
    ~HostMemory();

    /**
     * Copy constructors. They shall return a copy of the buffer without the mappings.
     * TODO: Implement them with COW if needed.
     */
    HostMemory(const HostMemory& other) = delete;
    HostMemory& operator=(const HostMemory& other) = delete;

    /**
     * Move constructors. They will move the buffer and the mappings to the new object.
     */
    HostMemory(HostMemory&& other) noexcept;
    HostMemory& operator=(HostMemory&& other) noexcept;

    void Map(size_t virtual_offset, size_t host_offset, size_t length, MemoryPermission perms,
             bool separate_heap);

    void Unmap(size_t virtual_offset, size_t length, bool separate_heap);

    void Protect(size_t virtual_offset, size_t length, MemoryPermission perms);

    void EnableDirectMappedAddress();

    void ClearBackingRegion(size_t physical_offset, size_t length, u32 fill_value);

    [[nodiscard]] u8* BackingBasePointer() noexcept {
        return backing_base;
    }
    [[nodiscard]] const u8* BackingBasePointer() const noexcept {
        return backing_base;
    }

    [[nodiscard]] u8* VirtualBasePointer() noexcept {
        return virtual_base;
    }
    [[nodiscard]] const u8* VirtualBasePointer() const noexcept {
        return virtual_base;
    }

    bool IsInVirtualRange(const void* address) const noexcept {
        return address >= virtual_base && address < virtual_base + virtual_size;
    }

    static void AdjustMap(u8* virtual_map_base, size_t virtual_size, size_t* virtual_offset, size_t* length) {
        // If we are direct mapped, we want to make sure we are operating on a region
        // that is in range of our virtual mapping.
        size_t intended_start = *virtual_offset;
        size_t intended_end = intended_start + *length;
        size_t address_space_start = reinterpret_cast<size_t>(virtual_map_base);
        size_t address_space_end = address_space_start + virtual_size;

        if (address_space_start > intended_end || intended_start > address_space_end) {
            *virtual_offset = 0;
            *length = 0;
        } else {
            *virtual_offset = (std::max)(intended_start, address_space_start);
            *length = (std::min)(intended_end, address_space_end) - *virtual_offset;
        }
    }

private:
    size_t backing_size{};
    size_t virtual_size{};

#if !(defined(__OPENORBIS__) || defined(__managarm__))
    // Low level handler for the platform dependent memory routines
    class Impl;
    std::unique_ptr<Impl> impl;
#endif
    u8* backing_base{};
    u8* virtual_base{};
    size_t virtual_base_offset{};
    // Windows requires it for kernels whom lack proper support for some functions!
    bool fallback_buffer{false};
};

} // namespace Common