#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.size() > 0 && buffer.size() > src.size());
    
    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);
    }
};

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

    void RegisterClass()
    {
        Expects(!m_class_registered);

        WNDCLASSW wnd_class{};
        wnd_class.lpfnWndProc   = ::DefWindowProcW;
        wnd_class.hInstance     = ::GetModuleHandleW(nullptr);
        wnd_class.lpszClassName = kClassName;

        ::RegisterClassW(&wnd_class);

        m_class_registered = true;
    }
    
public:
    StatusOr<gsl::owner<OsWindowHandle*>> 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);

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

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

        ::ShowWindow(hwnd, SW_SHOW);

        return nullptr;
    }
};

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

public:
    Win32OsApiImpl()
    {
        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>();
    auto* os_api = allocator_api->system->New<Win32OsApiImpl>();
    api_registry->Set(os_api);
}

} // namespace deimos