#include "deimos/core/os.h"
#include "deimos/core/api_registry.h"
#include "deimos/core/allocator.h"

#define WIN32_LEAN_AND_MEAN
#include <Windows.h>

namespace deimos
{

gsl::cwzstring Utf8ToUtf16Z(StringView src, Span<wchar_t> buffer)
{
    Expects(!buffer.empty() && buffer.size() > src.size());
    
    const int res = ::MultiByteToWideChar(CP_UTF8, 0, src.data(), (int)src.size_bytes(), buffer.data(), (int)buffer.size() - 1);
    if (res < 0) { return L"< MBTWC ERROR >"; }

    buffer[res] = L'\0';
    return buffer.data();
}

class Win32ConsoleApiImpl : public OsConsoleApi
{
    HANDLE m_stdout;
    HANDLE m_stderr;

    constexpr HANDLE Handle(OsConsoleType type) const
    {
        switch (type)
        {
            using enum OsConsoleType;
            case kStdOut: return m_stdout;
            case kStdErr: return m_stderr;
        }
    }

public:
    Win32ConsoleApiImpl() :
        m_stdout{::GetStdHandle(STD_OUTPUT_HANDLE)},
        m_stderr{::GetStdHandle(STD_ERROR_HANDLE)}
    {}

    void Write(OsConsoleType type, Span<const std::byte> data) override
    {
        ::WriteConsoleA(Handle(type), data.data(), (DWORD)data.size(), nullptr, nullptr);
    }
};

class Win32DllApiImpl : public OsDllApi
{
public:
    OsDll* Open(gsl::czstring name) override
    {
        return std::bit_cast<OsDll*>(::LoadLibraryA(name));
    }

    void* GetSymbol(OsDll* dll, gsl::czstring name) override
    {
        return std::bit_cast<void*>(::GetProcAddress(std::bit_cast<HMODULE>(dll), name));
    }
};

class Win32VirtualMemoryApiImpl : public OsVirtualMemoryApi
{
public:
    gsl::owner<void*> Map(int64_t size) override
    {
        return ::VirtualAlloc(nullptr, (SIZE_T)size, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
    }

    void Unmap(gsl::owner<void*> ptr) override
    {
        ::VirtualFree(ptr, 0, MEM_RELEASE);
    }

    gsl::owner<void*> Reserve(int64_t size) override
    {
        return ::VirtualAlloc(nullptr, (SIZE_T)size, MEM_RESERVE, PAGE_READWRITE);
    }

    void Commit(void* ptr, int64_t size) override
    {
        ::VirtualAlloc(ptr, (SIZE_T)size, MEM_COMMIT, PAGE_READWRITE);
    }
};

struct OsWindow
{
    HWND hwnd{};
    bool destroyed{};
    bool quit_requested{};
};

class Win32WindowApiImpl : public OsWindowApi
{
    static constexpr wchar_t kClassName[] = L"Deimos window class";
    
    HINSTANCE    m_hinstance;
    Allocator*   m_allocator;
    bool         m_class_registered = false;

    static LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
    {
        if (uMsg == WM_CREATE)
        {
            const auto* create = (const CREATESTRUCT*)lParam; // NOLINT
            ::SetWindowLongPtrW(hwnd, GWLP_USERDATA, std::bit_cast<LONG_PTR>(create->lpCreateParams));
            return 0;
        }

        auto* window = std::bit_cast<OsWindow*>(::GetWindowLongPtrW(hwnd, GWLP_USERDATA));

        switch (uMsg)
        {
            case WM_CLOSE:
            {
                window->quit_requested = true;
                ::DestroyWindow(hwnd);
                return 0;
            }
            case WM_DESTROY:
            {
                window->destroyed = true;
                ::PostQuitMessage(0);
                return 0;
            }
            default:
                return ::DefWindowProcW(hwnd, uMsg, wParam, lParam);
        }
    }    

    void RegisterClass()
    {
        Expects(!m_class_registered);

        WNDCLASSW wnd_class{};
        wnd_class.lpfnWndProc   = WindowProc;
        wnd_class.hInstance     = m_hinstance;
        wnd_class.lpszClassName = kClassName;

        ::RegisterClassW(&wnd_class);

        m_class_registered = true;
    }
    
public:
    explicit Win32WindowApiImpl(Allocator* allocator) :
        m_hinstance{::GetModuleHandleW(nullptr)},
        m_allocator{allocator}
    {}
    
    StatusOr<gsl::owner<OsWindow*>> Create(gsl::czstring title, int32_t width, int32_t height) override
    {
        if (!m_class_registered)
        {
            RegisterClass();
        }
        Ensures(m_class_registered);

        wchar_t title_w_buffer[128]{};
        gsl::cwzstring title_w = Utf8ToUtf16Z(title, title_w_buffer);
        
        auto* window = m_allocator->New<OsWindow>();

        HWND hwnd = ::CreateWindowExW(
            0, kClassName, title_w, WS_OVERLAPPEDWINDOW,
            CW_USEDEFAULT, CW_USEDEFAULT, width, height,
            nullptr, nullptr, m_hinstance, window);

        if (hwnd == nullptr)
        {
            return InternalError("Error while creating Win32 window");
        }

        ::ShowWindow(hwnd, SW_SHOW);

        window->hwnd = hwnd;
        return window;
    }
    
    void Update(OsWindow* window) override
    {
        if (window->destroyed) { return; }
        
        MSG msg;
        while (::PeekMessageW(&msg, window->hwnd, 0, 0, PM_REMOVE) != 0)
        {
            TranslateMessage(&msg);
            DispatchMessageW(&msg);
        }
    }

    bool QuitRequested(const OsWindow* window) override
    {
        return window->quit_requested;
    }
    
#if DEIMOS_OS_WIN32
    void* Win32Hwnd(const OsWindow* window) override
    {
        return std::bit_cast<void*>(window->hwnd);
    }
    
    void* Win32Hinstance(const OsWindow*) override
    {
        return std::bit_cast<void*>(m_hinstance);
    }
#endif
};

class Win32OsApiImpl : public OsApi
{
    Win32ConsoleApiImpl        m_console_api;
    Win32DllApiImpl            m_dll_api;
    Win32VirtualMemoryApiImpl  m_virtual_memory_api;
    Win32WindowApiImpl         m_window_api;

public:
    explicit Win32OsApiImpl(Allocator* allocator) :
        m_window_api(allocator)
    {
        console        = &m_console_api;
        dll            = &m_dll_api;
        virtual_memory = &m_virtual_memory_api;
        window         = &m_window_api;
    }
};

void RegisterOsApi(ApiRegistry* api_registry)
{
    auto* allocator_api = api_registry->Get<AllocatorApi>();

    Allocator* allocator = allocator_api->CreateChild(allocator_api->system, "OS");
    auto* os_api = allocator_api->system->New<Win32OsApiImpl>(allocator);
    
    api_registry->Set(os_api);
}

} // namespace deimos