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::msg::*;
use crate::prelude::*;
use crate::user::guard::*;

struct Obj { // actual fields of RawMain
	raw_base: RawBase,
	opts: WindowMainOpts,
	hchild_prev_focus: UnsafeCell<HWND>, // WM_ACTIVATE woes
	_pin: PhantomPinned,
}

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

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

impl RawMain {
	#[must_use]
	pub(in crate::gui) fn new(opts: WindowMainOpts) -> Self {
		let new_self = Self(
			Arc::pin(
				Obj {
					raw_base: RawBase::new(None::<&WindowMain>),
					opts,
					hchild_prev_focus: 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 run_main(&self,
		cmd_show: Option<co::SW>,
	) -> AnyResult<i32>
	{
		let opts = &self.0.opts;

		let hinst = HINSTANCE::GetModuleHandle(None)?;
		let mut wcx = WNDCLASSEX::default();
		let mut class_name_buf = WString::new();
		RawBase::fill_wndclassex(
			&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)?;

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

		let screen_sz = SIZE::new(
			GetSystemMetrics(co::SM::CXSCREEN),
			GetSystemMetrics(co::SM::CYSCREEN),
		);

		let wnd_pos = POINT::new(
			screen_sz.cx / 2 - wnd_sz.cx / 2, // center on screen
			screen_sz.cy / 2 - wnd_sz.cy / 2,
		);

		let mut wnd_rc = RECT { // client area, will be adjusted to size with title bar and borders
			left: wnd_pos.x,
			top: wnd_pos.y,
			right: wnd_pos.x + wnd_sz.cx,
			bottom: wnd_pos.y + wnd_sz.cy,
		};
		wnd_rc = AdjustWindowRectEx(wnd_rc, opts.style,
			opts.menu != HMENU::NULL, opts.ex_style)?;
		wnd_sz.cx = wnd_rc.right - wnd_rc.left;
		wnd_sz.cy = wnd_rc.bottom - wnd_rc.top;

		self.0.raw_base.create_window(
			None,
			atom,
			Some(&opts.title),
			if opts.menu == HMENU::NULL {
				IdMenu::None
			} else {
				IdMenu::Menu(&opts.menu)
			},
			POINT::new(wnd_rc.left, wnd_rc.top), wnd_sz,
			opts.ex_style, opts.style,
		)?;

		self.base().hwnd().ShowWindow(cmd_show.unwrap_or(co::SW::SHOW));
		self.base().hwnd().UpdateWindow()?;

		Base::run_main_loop(opts.accel_table.as_deref()) // blocks until window is closed
	}

	fn default_message_handlers(&self) {
		let self2 = self.clone();
		self.base().before_user_on().wm(co::WM::ACTIVATE, move |hwnd, p| {
			let p = wm::Activate::from_generic_wm(p);
			if !p.is_minimized {
				let hchild_prev_focus = unsafe { &mut *self2.0.hchild_prev_focus.get() };
				if p.event == co::WA::INACTIVE {
					if let Some(hwnd_cur_focus) = HWND::GetFocus() {
						if hwnd.IsChild(&hwnd_cur_focus) {
							*hchild_prev_focus = hwnd_cur_focus; // save previously focused control
						}
					}
				} else if *hchild_prev_focus != HWND::NULL {
					hchild_prev_focus.SetFocus(); // put focus back
				}
			}
			Ok(WmRet::HandledOk)
		});

		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)
		});

		self.base().on().wm_nc_destroy(move || {
			PostQuitMessage(0);
			Ok(())
		});
	}
}

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

/// Options to create a [`WindowMain`](crate::gui::WindowMain) programmatically
/// with [`WindowMain::new`](crate::gui::WindowMain::new).
pub struct WindowMainOpts {
	/// 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 `(600, 500)`.
	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::MINIMIZEBOX` to have a minimize button;
	/// * `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`.
	pub ex_style: co::WS_EX,
	/// Main menu of the window to be
	/// [created](https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-createwindowexw).
	///
	/// This menu is **not** shared: the window will own it, and destroy it when
	/// the window is destroyed.
	///
	/// Defaults to none.
	pub menu: HMENU,
	/// Main accelerator table of the window to be
	/// [created](https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-createwindowexw).
	/// Use
	/// [`HACCEL::CreateAcceleratorTable`](crate::prelude::user_Haccel::CreateAcceleratorTable)
	/// to create one.
	///
	/// Defaults to `None`.
	pub accel_table: Option<DestroyAcceleratorTableGuard>,
}

impl Default for WindowMainOpts {
	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: (600, 500),
			style: co::WS::CAPTION | co::WS::SYSMENU | co::WS::CLIPCHILDREN | co::WS::BORDER | co::WS::VISIBLE,
			ex_style: co::WS_EX::LEFT,
			menu: HMENU::NULL,
			accel_table: None,
		}
	}
}