use std::cell::UnsafeCell;
use std::marker::PhantomPinned;
use std::pin::Pin;
use std::sync::Arc;

use crate::co;
use crate::decl::*;
use crate::gui::{*, privs::*};
use crate::prelude::*;

struct Obj { // actual fields of RawModal
	raw_base: RawBase,
	opts: WindowModalOpts,
	hchild_prev_focus_parent: UnsafeCell<HWND>,
	_pin: PhantomPinned,
}

//------------------------------------------------------------------------------

/// An ordinary modal window.
#[derive(Clone)]
pub(in crate::gui) struct RawModal(Pin<Arc<Obj>>);

impl RawModal {
	#[must_use]
	pub(in crate::gui) fn new(
		parent: &impl AsRef<Base>,
		opts: WindowModalOpts,
	) -> Self
	{
		let new_self = Self(
			Arc::pin(
				Obj {
					raw_base: RawBase::new(Some(parent)),
					opts,
					hchild_prev_focus_parent: UnsafeCell::new(HWND::NULL),
					_pin: PhantomPinned,
				},
			),
		);
		new_self.default_message_handlers();
		new_self
	}

	#[must_use]
	pub(in crate::gui) fn base(&self) -> &Base {
		self.0.raw_base.base()
	}

	pub(in crate::gui) fn show_modal(&self) -> AnyResult<i32> {
		let hparent = self.base().parent().unwrap().hwnd();
		let opts = &self.0.opts;

		let parent_hinst = self.base().parent_hinstance()?;
		let mut wcx = WNDCLASSEX::default();
		let mut class_name_buf = WString::new();
		RawBase::fill_wndclassex(
			&parent_hinst,
			opts.class_style, &opts.class_icon, &opts.class_icon,
			&opts.class_bg_brush, &opts.class_cursor, &mut wcx,
			&mut class_name_buf)?;
		let atom = self.0.raw_base.register_class(&mut wcx)?;

		*unsafe { &mut *self.0.hchild_prev_focus_parent.get() } =
			HWND::GetFocus().unwrap_or(HWND::NULL);
		hparent.EnableWindow(false); // https://devblogs.microsoft.com/oldnewthing/20040227-00/?p=40463

		let mut wnd_sz = SIZE::new(opts.size.0 as _, opts.size.1 as _);
		multiply_dpi(None, Some(&mut wnd_sz))?;

		let mut wnd_rc = RECT { // client area, will be adjusted to size with title bar and borders
			left: 0,
			top: 0,
			right: wnd_sz.cx,
			bottom: wnd_sz.cy,
		};
		wnd_rc = AdjustWindowRectEx(wnd_rc, opts.style, false, opts.ex_style)?;
		wnd_sz.cx = wnd_rc.right - wnd_rc.left;
		wnd_sz.cy = wnd_rc.bottom - wnd_rc.top;

		let rc_parent = hparent.GetWindowRect()?; // relative to screen
		let wnd_pos = POINT {
			x: rc_parent.left + (rc_parent.right - rc_parent.left) / 2 - wnd_sz.cx / 2, // center on parent
			y: rc_parent.top + (rc_parent.bottom - rc_parent.top) / 2 - wnd_sz.cy / 2
		};

		self.0.raw_base.create_window(
			Some(hparent),
			atom,
			Some(&opts.title),
			IdMenu::None,
			wnd_pos, wnd_sz,
			opts.ex_style, opts.style,
		)?;

		self.run_modal_loop()
	}

	fn run_modal_loop(&self) -> AnyResult<i32> {
		loop {
			let mut msg = MSG::default();

			if !GetMessage(&mut msg, None, 0, 0)? {
				// WM_QUIT was sent, exit modal loop now and signal parent.
				// wParam has the program exit code.
				// https://devblogs.microsoft.com/oldnewthing/20050222-00/?p=36393
				// https://stackoverflow.com/a/29359913/6923555
				PostQuitMessage(msg.wParam as _);
				return Ok(0); // raw modals will always return 0
			}

			if *self.base().hwnd() == HWND::NULL || !self.base().hwnd().IsWindow() {
				return Ok(0); // our modal was destroyed, terminate loop
			}

			// If a child window, will retrieve its top-level parent.
			// If a top-level, use itself.
			let hwnd_top_level = msg.hwnd.GetAncestor(co::GA::ROOT)
				.unwrap_or(unsafe { msg.hwnd.raw_copy() });

			// Try to process keyboard actions for child controls.
			if hwnd_top_level.IsDialogMessage(&mut msg) {
				// Processed all keyboard actions for child controls.
				if *self.base().hwnd() == HWND::NULL {
					return Ok(0); // our modal was destroyed, terminate loop
				} else {
					continue;
				}
			}

			TranslateMessage(&msg);
			unsafe { DispatchMessage(&msg); }

			if *self.base().hwnd() == HWND::NULL || !self.base().hwnd().IsWindow() {
				return Ok(0); // our modal was destroyed, terminate loop
			}
		}
	}

	fn default_message_handlers(&self) {
		let self2 = self.clone();
		self.base().before_user_on().wm(co::WM::SETFOCUS, move |_, _| {
			self2.0.raw_base.delegate_focus_to_first_child();
			Ok(WmRet::HandledOk)
		});

		let self2 = self.clone();
		self.base().on().wm_close(move || {
			if let Ok(hparent) = self2.base().hwnd().GetWindow(co::GW::OWNER) {
				hparent.EnableWindow(true); // re-enable parent
				self2.base().hwnd().DestroyWindow()?; // then destroy modal
				let hchild_prev_focus_parent = unsafe { &mut *self2.0.hchild_prev_focus_parent.get() };
				if *hchild_prev_focus_parent != HWND::NULL {
					hchild_prev_focus_parent.SetFocus(); // this focus could be set on WM_DESTROY as well
				}
			}
			Ok(())
		});
	}
}

//------------------------------------------------------------------------------

/// Options to create a [`WindowModal`](crate::gui::WindowModal)
/// programmatically with [`WindowModal::new`](crate::gui::WindowModal::new).
pub struct WindowModalOpts {
	/// Window class name to be
	/// [registered](https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-registerclassexw).
	///
	/// Defaults to an auto-generated string.
	pub class_name: String,
	/// Window class styles to be
	/// [registered](https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-registerclassexw).
	///
	/// Defaults to `co::CS::DBLCLKS`.
	pub class_style: co::CS,
	/// Window main icon to be
	/// [registered](https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-registerclassexw).
	///
	/// Defaults to `gui::Icon::None`.
	pub class_icon: Icon,
	/// Window cursor to be
	/// [registered](https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-registerclassexw).
	///
	/// Defaults to `gui::Cursor::Idc(co::IDC::ARROW)`.
	pub class_cursor: Cursor,
	/// Window background brush to be
	/// [registered](https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-registerclassexw).
	///
	/// Defaults to `gui::Brush::Color(co::COLOR::BTNFACE)`.
	pub class_bg_brush: Brush,

	/// Window title to be
	/// [created](https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-createwindowexw).
	///
	/// Defaults to empty string.
	pub title: String,
	/// Width and height of window client area, in pixels, to be
	/// [created](https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-createwindowexw).
	/// Does not include title bar or borders.
	///
	/// Will be adjusted to match current system DPI.
	///
	/// Defaults to `(500, 400)`.
	pub size: (u32, u32),
	/// Window styles to be
	/// [created](https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-createwindowexw).
	///
	/// Defaults to `WS::CAPTION | WS::SYSMENU | WS::CLIPCHILDREN | WS::BORDER | WS::VISIBLE`.
	///
	/// Suggestions:
	/// * `WS::SIZEBOX` to make the window resizable;
	/// * `WS::MAXIMIZEBOX` to have a maximize button.
	pub style: co::WS,
	/// Extended window styles to be
	/// [created](https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-createwindowexw).
	///
	/// Defaults to `WS_EX::LEFT | WS_EX::DLGMODALFRAME`.
	pub ex_style: co::WS_EX,
}

impl Default for WindowModalOpts {
	fn default() -> Self {
		Self {
			class_name: "".to_owned(),
			class_style: co::CS::DBLCLKS,
			class_icon: Icon::None,
			class_cursor: Cursor::Idc(co::IDC::ARROW),
			class_bg_brush: Brush::Color(co::COLOR::BTNFACE),
			title: "".to_owned(),
			size: (500, 400),
			style: co::WS::CAPTION | co::WS::SYSMENU | co::WS::CLIPCHILDREN | co::WS::BORDER | co::WS::VISIBLE,
			ex_style: co::WS_EX::LEFT | co::WS_EX::DLGMODALFRAME,
		}
	}
}