#include "editor.h"

// The Win32 API requires you to hardcode identifiers for tiemrs
constexpr size_t idle_timer_id = 1337;

constexpr char xembed_proeprty[] = "_XEMBED";
constexpr char xembed_info_proeprty[] = "_XEMBED_INFO";

// Constants from the XEmbed spec
constexpr uint32_t xembed_protocol_version = 0;

constexpr uint32_t xembed_embedded_notify_msg = 0;
constexpr uint32_t xembed_window_activate_msg = 1;
constexpr uint32_t xembed_focus_in_msg = 4;

constexpr uint32_t xembed_focus_first = 1;

ATOM register_window_class(std::string window_class_name);

Editor::Editor(std::string window_class_name)
    : window_class(register_window_class(window_class_name)),
      x11_connection(xcb_connect(nullptr, nullptr), &xcb_disconnect) {
    // We need a bunch of property atoms for the XEmbed protocol
    xcb_generic_error_t* err;

    const auto xembed_cookie = xcb_intern_atom(
        x11_connection.get(), 0, strlen(xembed_proeprty), xembed_proeprty);
    const auto xembed_info_cookie =
        xcb_intern_atom(x11_connection.get(), 0, strlen(xembed_info_proeprty),
                        xembed_info_proeprty);

    xcb_xembed =
        xcb_intern_atom_reply(x11_connection.get(), xembed_cookie, &err)->atom;
    xcb_xembed_info =
        xcb_intern_atom_reply(x11_connection.get(), xembed_info_cookie, &err)
            ->atom;
}

HWND Editor::open(AEffect* effect, xcb_window_t parent_window_handle) {
    // Create a window without any decoratiosn for easy embedding. The
    // combination of `WS_EX_TOOLWINDOW` and `WS_POPUP` causes the window to be
    // drawn without any decorations (making resizes behave as you'd expect) and
    // also causes mouse coordinates to be relative to the window itself.
    win32_handle =
        std::unique_ptr<std::remove_pointer_t<HWND>, decltype(&DestroyWindow)>(
            CreateWindowEx(WS_EX_TOOLWINDOW | WS_EX_ACCEPTFILES,
                           reinterpret_cast<LPCSTR>(window_class),
                           "yabridge plugin", WS_POPUP, CW_USEDEFAULT,
                           CW_USEDEFAULT, 2048, 2048, nullptr, nullptr,
                           GetModuleHandle(nullptr), this),
            &DestroyWindow);

    // Needed to send update messages on a timer
    plugin = effect;
    parent_window = parent_window_handle;

    // The Win32 API will block the `DispatchMessage` call when opening e.g. a
    // dropdown, but it will still allow timers to be run so the GUI can still
    // update in the background. Because of this we send `effEditIdle` to the
    // plugin on a timer. The refresh rate is purposely fairly low since we
    // we'll also trigger this manually in `Editor::handle_events()` whenever
    // the plugin is not busy.
    SetTimer(win32_handle->get(), idle_timer_id, 100, nullptr);

    // We'll only start the xembed procedure after the host has givne the window
    // the correct size, otherwise Wine can't draw correctly
    const uint32_t event_mask = XCB_EVENT_MASK_STRUCTURE_NOTIFY;
    xcb_change_window_attributes(x11_connection.get(), parent_window,
                                 XCB_CW_EVENT_MASK, &event_mask);
    xcb_flush(x11_connection.get());

    return win32_handle->get();
}

void Editor::close() {
    // RAII will destroy the window and tiemrs for us
    win32_handle = std::nullopt;

    // TODO: Do we need to do something on the X11 side or does the host do
    //       everything for us?
}

// TODO: I feel like this shouldn't necessary with xembed
bool Editor::resize(const VstRect& new_size) {
    if (!win32_handle.has_value()) {
        return false;
    }

    SetWindowPos(win32_handle->get(), HWND_TOP, new_size.left, new_size.top,
                 new_size.right - new_size.left, new_size.bottom - new_size.top,
                 0);

    return true;
}

bool Editor::xembed() {
    if (!win32_handle.has_value()) {
        return false;
    }

    // This follows the embedding procedure specified in the XEmbed sped:
    // https://specifications.freedesktop.org/xembed-spec/xembed-spec-latest.html
    // under 'Embedding life cycle
    // Sadly there's doesn't seem to be any implementation of this available as
    // a library
    const size_t child_window = get_x11_handle().value();

    xcb_reparent_window(x11_connection.get(), child_window, parent_window, 0,
                        0);

    // Tell the window from Wine it's embedded into the window provided by the
    // host
    send_xembed_event(child_window, xembed_embedded_notify_msg, 0,
                      parent_window, xembed_protocol_version);

    send_xembed_event(child_window, xembed_focus_in_msg, xembed_focus_first, 0,
                      0);
    send_xembed_event(child_window, xembed_window_activate_msg, 0, 0, 0);

    xcb_map_window(x11_connection.get(), child_window);
    xcb_flush(x11_connection.get());

    ShowWindow(win32_handle->get(), SW_SHOWNORMAL);

    return true;
}

void Editor::handle_events() {
    // Process any remaining events, otherwise we won't be able to interact with
    // the window
    if (win32_handle.has_value()) {
        bool gui_was_updated = false;
        MSG msg;

        // The second argument has to be null since we not only want to handle
        // events for this window but also for all child windows (i.e.
        // dropdowns). I spent way longer debugging this than I want to admit.
        while (PeekMessage(&msg, nullptr, 0, 0, PM_REMOVE)) {
            TranslateMessage(&msg);
            DispatchMessage(&msg);

            if (msg.message == WM_TIMER && msg.wParam == idle_timer_id) {
                gui_was_updated = true;
            }
        }

        // Make sure that the GUI always gets updated at least once for every
        // `effEditIdle` call the host has sent to improve responsiveness when
        // the GUI isn't being blocked.
        if (!gui_was_updated) {
            SendMessage(win32_handle->get(), WM_TIMER, idle_timer_id, 0);
        }

        // Handle X11 events
        xcb_generic_event_t* event;
        while ((event = xcb_poll_for_event(x11_connection.get())) != nullptr) {
            if ((event->response_type & ~0x80) == XCB_CONFIGURE_NOTIFY) {
                xcb_configure_notify_event_t configuration =
                    *reinterpret_cast<xcb_configure_notify_event_t*>(event);

                // TODO: Only has to be done once, and the problems mentioned in
                //       the readme are still here.
                xembed();
            }

            free(event);
        }
    }
}

std::optional<size_t> Editor::get_x11_handle() {
    if (!win32_handle.has_value()) {
        return std::nullopt;
    }

    return reinterpret_cast<size_t>(
        GetProp(win32_handle.value().get(), "__wine_x11_whole_window"));
}

void Editor::send_xembed_event(const xcb_window_t& window,
                               const uint32_t message,
                               const uint32_t detail,
                               const uint32_t data1,
                               const uint32_t data2) {
    xcb_client_message_event_t event;
    event.response_type = XCB_CLIENT_MESSAGE;
    event.type = xcb_xembed;
    event.window = window;
    event.format = 32;
    event.data.data32[0] = XCB_CURRENT_TIME;
    event.data.data32[1] = message;
    event.data.data32[2] = detail;
    event.data.data32[3] = data1;
    event.data.data32[4] = data2;

    xcb_send_event(x11_connection.get(), false, window, XCB_EVENT_MASK_NO_EVENT,
                   reinterpret_cast<char*>(&event));
}

LRESULT CALLBACK window_proc(HWND handle,
                             UINT message,
                             WPARAM wParam,
                             LPARAM lParam) {
    switch (message) {
        case WM_CREATE: {
            const auto window_parameters =
                reinterpret_cast<CREATESTRUCT*>(lParam);
            const auto editor =
                static_cast<Editor*>(window_parameters->lpCreateParams);
            if (editor == nullptr) {
                break;
            }

            // Sent when the window is first being created. `lParam` here
            // contains the last argument of `CreateWindowEx`, which was a
            // pointer to the `Editor` object. We need to attach this to the
            // window handle so we can access our VST plugin instance later.
            SetWindowLongPtr(handle, GWLP_USERDATA,
                             reinterpret_cast<size_t>(editor));
        } break;
        case WM_TIMER: {
            auto editor = reinterpret_cast<Editor*>(
                GetWindowLongPtr(handle, GWLP_USERDATA));
            if (editor == nullptr || wParam != idle_timer_id) {
                break;
            }

            // We'll send idle messages on a timer. This way the plugin will get
            // these either when the host sends `effEditIdle` themself, or
            // periodically when the GUI is being blocked by a dropdown or a
            // message box.
            editor->plugin->dispatcher(editor->plugin, effEditIdle, 0, 0,
                                       nullptr, 0);
            return 0;
        } break;
    }

    return DefWindowProc(handle, message, wParam, lParam);
}

ATOM register_window_class(std::string window_class_name) {
    WNDCLASSEX window_class{};

    window_class.cbSize = sizeof(WNDCLASSEX);
    window_class.style = CS_DBLCLKS | CS_HREDRAW | CS_VREDRAW;
    window_class.lpfnWndProc = window_proc;
    window_class.hInstance = GetModuleHandle(nullptr);
    window_class.hCursor = LoadCursor(nullptr, IDC_ARROW);
    window_class.hbrBackground = CreateHatchBrush(HS_CROSS, RGB(255, 0, 255));
    window_class.lpszClassName = window_class_name.c_str();

    return RegisterClassEx(&window_class);
}