//! Create interactive, native cross-platform applications.
use crate::{mouse, Error, Executor, Runtime};

pub use iced_winit::Application;

use iced_graphics::window;
use iced_winit::application;
use iced_winit::conversion;
use iced_winit::futures;
use iced_winit::futures::channel::mpsc;
use iced_winit::{Cache, Clipboard, Debug, Proxy, Settings};

use glutin::window::Window;
use std::mem::ManuallyDrop;

/// Runs an [`Application`] with an executor, compositor, and the provided
/// settings.
pub fn run<A, E, C>(
    settings: Settings<A::Flags>,
    compositor_settings: C::Settings,
) -> Result<(), Error>
where
    A: Application + 'static,
    E: Executor + 'static,
    C: window::GLCompositor<Renderer = A::Renderer> + 'static,
{
    use futures::task;
    use futures::Future;
    use glutin::event_loop::EventLoop;
    use glutin::ContextBuilder;

    let mut debug = Debug::new();
    debug.startup_started();

    let event_loop = EventLoop::with_user_event();
    let mut runtime = {
        let executor = E::new().map_err(Error::ExecutorCreationFailed)?;
        let proxy = Proxy::new(event_loop.create_proxy());

        Runtime::new(executor, proxy)
    };

    let (application, init_command) = {
        let flags = settings.flags;

        runtime.enter(|| A::new(flags))
    };

    let subscription = application.subscription();

    runtime.spawn(init_command);
    runtime.track(subscription);

    let context = {
        let builder = settings.window.into_builder(
            &application.title(),
            application.mode(),
            event_loop.primary_monitor(),
        );

        let context = ContextBuilder::new()
            .with_vsync(true)
            .with_multisampling(C::sample_count(&compositor_settings) as u16)
            .build_windowed(builder, &event_loop)
            .map_err(|error| {
                use glutin::CreationError;

                match error {
                    CreationError::Window(error) => {
                        Error::WindowCreationFailed(error)
                    }
                    _ => Error::GraphicsAdapterNotFound,
                }
            })?;

        #[allow(unsafe_code)]
        unsafe {
            context.make_current().expect("Make OpenGL context current")
        }
    };

    #[allow(unsafe_code)]
    let (compositor, renderer) = unsafe {
        C::new(compositor_settings, |address| {
            context.get_proc_address(address)
        })?
    };

    let (mut sender, receiver) = mpsc::unbounded();

    let mut instance = Box::pin(run_instance::<A, E, C>(
        application,
        compositor,
        renderer,
        context,
        runtime,
        debug,
        receiver,
    ));

    let mut context = task::Context::from_waker(task::noop_waker_ref());

    event_loop.run(move |event, _, control_flow| {
        use glutin::event_loop::ControlFlow;

        if let ControlFlow::Exit = control_flow {
            return;
        }

        if let Some(event) = event.to_static() {
            sender.start_send(event).expect("Send event");

            let poll = instance.as_mut().poll(&mut context);

            *control_flow = match poll {
                task::Poll::Pending => ControlFlow::Wait,
                task::Poll::Ready(_) => ControlFlow::Exit,
            };
        }
    });
}

async fn run_instance<A, E, C>(
    mut application: A,
    mut compositor: C,
    mut renderer: A::Renderer,
    context: glutin::ContextWrapper<glutin::PossiblyCurrent, Window>,
    mut runtime: Runtime<E, Proxy<A::Message>, A::Message>,
    mut debug: Debug,
    mut receiver: mpsc::UnboundedReceiver<glutin::event::Event<'_, A::Message>>,
) where
    A: Application + 'static,
    E: Executor + 'static,
    C: window::GLCompositor<Renderer = A::Renderer> + 'static,
{
    use glutin::event;
    use iced_winit::futures::stream::StreamExt;

    let clipboard = Clipboard::new(context.window());

    let mut state = application::State::new(&application, context.window());
    let mut viewport_version = state.viewport_version();
    let mut user_interface =
        ManuallyDrop::new(application::build_user_interface(
            &mut application,
            Cache::default(),
            &mut renderer,
            state.logical_size(),
            &mut debug,
        ));

    let mut primitive =
        user_interface.draw(&mut renderer, state.cursor_position());
    let mut mouse_interaction = mouse::Interaction::default();

    let mut events = Vec::new();
    let mut messages = Vec::new();

    debug.startup_finished();

    while let Some(event) = receiver.next().await {
        match event {
            event::Event::MainEventsCleared => {
                if events.is_empty() && messages.is_empty() {
                    continue;
                }

                debug.event_processing_started();

                let statuses = user_interface.update(
                    &events,
                    state.cursor_position(),
                    clipboard.as_ref().map(|c| c as _),
                    &mut renderer,
                    &mut messages,
                );

                debug.event_processing_finished();

                for event in events.drain(..).zip(statuses.into_iter()) {
                    runtime.broadcast(event);
                }

                if !messages.is_empty() {
                    let cache =
                        ManuallyDrop::into_inner(user_interface).into_cache();

                    // Update application
                    application::update(
                        &mut application,
                        &mut runtime,
                        &mut debug,
                        &mut messages,
                    );

                    // Update window
                    state.synchronize(&application, context.window());

                    user_interface =
                        ManuallyDrop::new(application::build_user_interface(
                            &mut application,
                            cache,
                            &mut renderer,
                            state.logical_size(),
                            &mut debug,
                        ));
                }

                debug.draw_started();
                primitive =
                    user_interface.draw(&mut renderer, state.cursor_position());
                debug.draw_finished();

                context.window().request_redraw();
            }
            event::Event::UserEvent(message) => {
                messages.push(message);
            }
            event::Event::RedrawRequested(_) => {
                debug.render_started();
                let current_viewport_version = state.viewport_version();

                if viewport_version != current_viewport_version {
                    let physical_size = state.physical_size();
                    let logical_size = state.logical_size();

                    debug.layout_started();
                    user_interface = ManuallyDrop::new(
                        ManuallyDrop::into_inner(user_interface)
                            .relayout(logical_size, &mut renderer),
                    );
                    debug.layout_finished();

                    debug.draw_started();
                    primitive = user_interface
                        .draw(&mut renderer, state.cursor_position());
                    debug.draw_finished();

                    context.resize(glutin::dpi::PhysicalSize::new(
                        physical_size.width,
                        physical_size.height,
                    ));

                    compositor.resize_viewport(physical_size);

                    viewport_version = current_viewport_version;
                }

                let new_mouse_interaction = compositor.draw(
                    &mut renderer,
                    state.viewport(),
                    state.background_color(),
                    &primitive,
                    &debug.overlay(),
                );

                context.swap_buffers().expect("Swap buffers");

                debug.render_finished();

                if new_mouse_interaction != mouse_interaction {
                    context.window().set_cursor_icon(
                        conversion::mouse_interaction(new_mouse_interaction),
                    );

                    mouse_interaction = new_mouse_interaction;
                }

                // TODO: Handle animations!
                // Maybe we can use `ControlFlow::WaitUntil` for this.
            }
            event::Event::WindowEvent {
                event: window_event,
                ..
            } => {
                if application::requests_exit(&window_event, state.modifiers())
                {
                    break;
                }

                state.update(context.window(), &window_event, &mut debug);

                if let Some(event) = conversion::window_event(
                    &window_event,
                    state.scale_factor(),
                    state.modifiers(),
                ) {
                    events.push(event);
                }
            }
            _ => {}
        }
    }

    // Manually drop the user interface
    drop(ManuallyDrop::into_inner(user_interface));
}