irondash_run_loop 0.1.1

use once_cell::sync::OnceCell;

use super::sys::windows::*;

static WINDOW_CLASS: OnceCell<WindowClass> = OnceCell::new();

struct WindowClass {
    pub class_name: String,
}

pub fn to_utf16(s: &str) -> Vec<u16> {
    let mut string: Vec<u16> = s.encode_utf16().collect();
    string.push(0);
    string
}

impl WindowClass {
    pub fn get() -> &'static Self {
        WINDOW_CLASS.get_or_init(Self::new)
    }

    fn new() -> Self {
        let res = WindowClass {
            class_name: "IrondashCoreMessageWindow".into(),
        };
        res.register();
        res
    }

    fn register(&self) {
        unsafe {
            let mut class_name = to_utf16(&self.class_name);
            let class = WNDCLASSW {
                style: 0,
                lpfnWndProc: wnd_proc,
                cbClsExtra: 0,
                cbWndExtra: 0,
                hInstance: GetModuleHandleW(std::ptr::null_mut()),
                hIcon: 0,
                hCursor: LoadCursorW(0, IDC_ARROW),
                hbrBackground: 0,
                lpszMenuName: std::ptr::null_mut(),
                lpszClassName: class_name.as_mut_ptr(),
            };
            RegisterClassW(&class as *const _);
        }
    }

    fn unregister(&mut self) {
        unsafe {
            UnregisterClassW(to_utf16(&self.class_name).as_mut_ptr(), 0);
        }
    }
}

unsafe extern "system" fn wnd_proc(
    h_wnd: HWND,
    msg: u32,
    w_param: WPARAM,
    l_param: LPARAM,
) -> LRESULT {
    if msg == WM_NCCREATE {
        let create_struct = &*(l_param as *const CREATESTRUCTW);
        SetWindowLongPtrW(h_wnd, GWLP_USERDATA, create_struct.lpCreateParams as isize);
    }

    let ptr = GetWindowLongPtrW(h_wnd, GWLP_USERDATA);
    if ptr != 0 {
        let bridge = &*(ptr as *const EventBridge);
        let handler = &*(bridge.handler);
        let res = handler.wnd_proc(h_wnd, msg, w_param, l_param);
        if msg == WM_NCDESTROY {
            // make sure bridge is dropped
            let _ = Box::<EventBridge>::from_raw(ptr as *mut EventBridge);
        }
        return res;
    }

    DefWindowProcW(h_wnd, msg, w_param, l_param)
}

impl Drop for WindowClass {
    fn drop(&mut self) {
        self.unregister();
    }
}

struct EventBridge {
    handler: *const dyn WindowAdapter,
    _class: &'static WindowClass, // keep class alive
}

pub trait WindowAdapter {
    fn wnd_proc(&self, h_wnd: HWND, msg: u32, w_param: WPARAM, l_param: LPARAM) -> LRESULT;

    fn create_window(&self, title: &str, style: WINDOW_STYLE, ex_style: WINDOW_STYLE) -> HWND
    where
        Self: Sized,
    {
        unsafe {
            let s = self as &dyn WindowAdapter;
            let class = WindowClass::get();
            let ptr = std::mem::transmute(s);
            let bridge = Box::new(EventBridge {
                handler: ptr,
                _class: class,
            });

            let mut class_name = to_utf16(&class.class_name);
            let mut title = to_utf16(title);
            CreateWindowExW(
                ex_style,
                class_name.as_mut_ptr(),
                title.as_mut_ptr(),
                style,
                0,
                0,
                0,
                0,
                HWND_MESSAGE,
                0,
                GetModuleHandleW(std::ptr::null_mut()),
                Box::into_raw(bridge) as *mut _,
            )
        }
    }
}