/* LICENSE BEGIN
    This file is part of the SixtyFPS Project -- https://sixtyfps.io
    Copyright (c) 2020 Olivier Goffart <olivier.goffart@sixtyfps.io>
    Copyright (c) 2020 Simon Hausmann <simon.hausmann@sixtyfps.io>

    SPDX-License-Identifier: GPL-3.0-only
    This file is also available under commercial licensing terms.
    Please contact info@sixtyfps.io for more information.
LICENSE END */
#![warn(missing_docs)]
/*!
    This module contains the event loop implementation using winit, as well as the
    [GenericWindow] trait used by the generated code and the run-time to change
    aspects of windows on the screen.
*/
use sixtyfps_corelib as corelib;

use corelib::graphics::Point;
use corelib::input::{KeyEvent, MouseEventType};
use corelib::window::*;
use std::cell::RefCell;
use std::convert::TryInto;
use std::rc::{Rc, Weak};

#[cfg(not(target_arch = "wasm32"))]
use winit::platform::run_return::EventLoopExtRunReturn;

thread_local! {
    static ALL_WINDOWS: RefCell<std::collections::HashMap<winit::window::WindowId, Weak<dyn GenericWindow>>> = RefCell::new(std::collections::HashMap::new());
}

pub fn register_window(id: winit::window::WindowId, window: Rc<dyn GenericWindow>) {
    ALL_WINDOWS.with(|windows| {
        windows.borrow_mut().insert(id, Rc::downgrade(&window));
    })
}

pub fn unregister_window(id: winit::window::WindowId) {
    ALL_WINDOWS.with(|windows| {
        windows.borrow_mut().remove(&id);
    })
}

/// This enum captures run-time specific events that can be dispatched to the event loop in
/// addition to the winit events.
#[derive(Debug)]
pub enum CustomEvent {
    /// Request for the event loop to wake up and poll. This is used on the web for example to
    /// request an animation frame.
    WakeUpAndPoll,
}

/// This is the main structure to hold the event loop responsible for delegating events from the
/// windowing system to the individual windows managed by the run-time, and then subsequently to
/// the items. These are typically rendering and input events.
pub struct EventLoop {
    winit_loop: winit::event_loop::EventLoop<CustomEvent>,
}

impl EventLoop {
    /// Returns a new instance of the event loop, backed by a winit eventloop.
    pub fn new() -> Self {
        Self { winit_loop: winit::event_loop::EventLoop::with_user_event() }
    }

    /// Runs the event loop and renders the items in the provided `component` in its
    /// own window.
    #[allow(unused_mut)] // mut need changes for wasm
    pub fn run(mut self) {
        use winit::event::Event;
        use winit::event_loop::{ControlFlow, EventLoopWindowTarget};

        // last seen cursor position, (physical coordinate)
        let mut cursor_pos = Point::default();
        let mut pressed = false;
        let mut run_fn = move |event: Event<CustomEvent>,
                               _: &EventLoopWindowTarget<CustomEvent>,
                               control_flow: &mut ControlFlow| {
            *control_flow = ControlFlow::Wait;

            match event {
                winit::event::Event::WindowEvent {
                    event: winit::event::WindowEvent::CloseRequested,
                    ..
                } => *control_flow = winit::event_loop::ControlFlow::Exit,
                winit::event::Event::RedrawRequested(id) => {
                    corelib::animations::update_animations();
                    ALL_WINDOWS.with(|windows| {
                        if let Some(Some(window)) =
                            windows.borrow().get(&id).map(|weakref| weakref.upgrade())
                        {
                            window.draw();
                        }
                    });
                }
                winit::event::Event::WindowEvent {
                    event: winit::event::WindowEvent::Resized(size),
                    window_id,
                } => {
                    ALL_WINDOWS.with(|windows| {
                        if let Some(Some(window)) =
                            windows.borrow().get(&window_id).map(|weakref| weakref.upgrade())
                        {
                            window.refresh_window_scale_factor();
                            window.set_width(size.width as f32);
                            window.set_height(size.height as f32);
                        }
                    });
                }
                winit::event::Event::WindowEvent {
                    event:
                        winit::event::WindowEvent::ScaleFactorChanged {
                            scale_factor,
                            new_inner_size: size,
                        },
                    window_id,
                } => {
                    ALL_WINDOWS.with(|windows| {
                        if let Some(Some(window)) =
                            windows.borrow().get(&window_id).map(|weakref| weakref.upgrade())
                        {
                            window.set_width(size.width as f32);
                            window.set_height(size.height as f32);
                            window.set_scale_factor(scale_factor as f32);
                        }
                    });
                }

                winit::event::Event::WindowEvent {
                    ref window_id,
                    event: winit::event::WindowEvent::MouseInput { state, .. },
                    ..
                } => {
                    corelib::animations::update_animations();
                    ALL_WINDOWS.with(|windows| {
                        if let Some(Some(window)) =
                            windows.borrow().get(&window_id).map(|weakref| weakref.upgrade())
                        {
                            let what = match state {
                                winit::event::ElementState::Pressed => {
                                    pressed = true;
                                    MouseEventType::MousePressed
                                }
                                winit::event::ElementState::Released => {
                                    pressed = false;
                                    MouseEventType::MouseReleased
                                }
                            };
                            window.clone().process_mouse_input(cursor_pos, what);
                            // FIXME: remove this, it should be based on actual changes rather than this
                            window.request_redraw();
                        }
                    });
                }
                winit::event::Event::WindowEvent {
                    ref window_id,
                    event: winit::event::WindowEvent::Touch(touch),
                    ..
                } => {
                    corelib::animations::update_animations();
                    ALL_WINDOWS.with(|windows| {
                        if let Some(Some(window)) =
                            windows.borrow().get(&window_id).map(|weakref| weakref.upgrade())
                        {
                            let cursor_pos =
                                euclid::point2(touch.location.x as _, touch.location.y as _);
                            let what = match touch.phase {
                                winit::event::TouchPhase::Started => {
                                    pressed = true;
                                    MouseEventType::MousePressed
                                }
                                winit::event::TouchPhase::Ended
                                | winit::event::TouchPhase::Cancelled => {
                                    pressed = false;
                                    MouseEventType::MouseReleased
                                }
                                winit::event::TouchPhase::Moved => MouseEventType::MouseMoved,
                            };
                            window.clone().process_mouse_input(cursor_pos, what);
                            // FIXME: remove this, it should be based on actual changes rather than this
                            window.request_redraw();
                        }
                    });
                }
                winit::event::Event::WindowEvent {
                    window_id,
                    event: winit::event::WindowEvent::CursorMoved { position, .. },
                    ..
                } => {
                    cursor_pos = euclid::point2(position.x as _, position.y as _);
                    corelib::animations::update_animations();
                    ALL_WINDOWS.with(|windows| {
                        if let Some(Some(window)) =
                            windows.borrow().get(&window_id).map(|weakref| weakref.upgrade())
                        {
                            window
                                .clone()
                                .process_mouse_input(cursor_pos, MouseEventType::MouseMoved);
                            // FIXME: remove this, it should be based on actual changes rather than this
                            window.request_redraw();
                        }
                    });
                }
                // On the html canvas, we don't get the mouse move or release event when outside the canvas. So we have no choice but canceling the event
                #[cfg(target_arch = "wasm32")]
                winit::event::Event::WindowEvent {
                    ref window_id,
                    event: winit::event::WindowEvent::CursorLeft { .. },
                    ..
                } => {
                    if pressed {
                        corelib::animations::update_animations();
                        ALL_WINDOWS.with(|windows| {
                            if let Some(Some(window)) =
                                windows.borrow().get(&window_id).map(|weakref| weakref.upgrade())
                            {
                                pressed = false;
                                window
                                    .clone()
                                    .process_mouse_input(cursor_pos, MouseEventType::MouseExit);
                                // FIXME: remove this, it should be based on actual changes rather than this
                                window.request_redraw();
                            }
                        });
                    }
                }

                winit::event::Event::WindowEvent {
                    ref window_id,
                    event: winit::event::WindowEvent::KeyboardInput { ref input, .. },
                } => {
                    corelib::animations::update_animations();
                    ALL_WINDOWS.with(|windows| {
                        if let Some(Some(window)) =
                            windows.borrow().get(&window_id).map(|weakref| weakref.upgrade())
                        {
                            if let Some(ref key_event) =
                                (input, window.current_keyboard_modifiers()).try_into().ok()
                            {
                                window.clone().process_key_input(key_event);
                                // FIXME: remove this, it should be based on actual changes rather than this
                                window.request_redraw();
                            }
                        }
                    });
                }
                winit::event::Event::WindowEvent {
                    ref window_id,
                    event: winit::event::WindowEvent::ReceivedCharacter(ch),
                } => {
                    if !ch.is_control() {
                        corelib::animations::update_animations();
                        ALL_WINDOWS.with(|windows| {
                            if let Some(Some(window)) =
                                windows.borrow().get(&window_id).map(|weakref| weakref.upgrade())
                            {
                                let modifiers = window.current_keyboard_modifiers();

                                if !modifiers.control() && !modifiers.alt() && !modifiers.logo() {
                                    let key_event = KeyEvent::CharacterInput {
                                        unicode_scalar: ch.into(),
                                        modifiers,
                                    };
                                    window.clone().process_key_input(&key_event);
                                    // FIXME: remove this, it should be based on actual changes rather than this
                                    window.request_redraw();
                                }
                            }
                        });
                    }
                }
                winit::event::Event::WindowEvent {
                    ref window_id,
                    event: winit::event::WindowEvent::ModifiersChanged(state),
                } => {
                    ALL_WINDOWS.with(|windows| {
                        if let Some(Some(window)) =
                            windows.borrow().get(&window_id).map(|weakref| weakref.upgrade())
                        {
                            window.set_current_keyboard_modifiers(state.into());
                        }
                    });
                }

                winit::event::Event::WindowEvent {
                    ref window_id,
                    event: winit::event::WindowEvent::Focused(have_focus),
                } => {
                    ALL_WINDOWS.with(|windows| {
                        if let Some(Some(window)) =
                            windows.borrow().get(&window_id).map(|weakref| weakref.upgrade())
                        {
                            window.clone().set_focus(have_focus);
                            // FIXME: remove this, it should be based on actual changes rather than this
                            window.request_redraw();
                        }
                    });
                }

                _ => (),
            }

            if *control_flow != winit::event_loop::ControlFlow::Exit {
                corelib::animations::CURRENT_ANIMATION_DRIVER.with(|driver| {
                    if !driver.has_active_animations() {
                        return;
                    }
                    *control_flow = ControlFlow::Poll;
                    ALL_WINDOWS.with(|windows| {
                        windows.borrow().values().for_each(|window| {
                            if let Some(window) = window.upgrade() {
                                window.request_redraw();
                            }
                        })
                    })
                })
            }

            if corelib::timers::TimerList::maybe_activate_timers() {
                ALL_WINDOWS.with(|windows| {
                    windows.borrow().values().for_each(|window| {
                        if let Some(window) = window.upgrade() {
                            window.request_redraw();
                        }
                    })
                })
            }

            if *control_flow == winit::event_loop::ControlFlow::Wait {
                if let Some(next_timer) = corelib::timers::TimerList::next_timeout() {
                    *control_flow = winit::event_loop::ControlFlow::WaitUntil(next_timer);
                }
            }
        };

        #[cfg(not(target_arch = "wasm32"))]
        self.winit_loop.run_return(run_fn);
        #[cfg(target_arch = "wasm32")]
        {
            // Since wasm does not have a run_return function that takes a non-static closure,
            // we use this hack to work that around
            scoped_tls_hkt::scoped_thread_local!(static mut RUN_FN_TLS: for <'a> &'a mut dyn FnMut(
                Event<'_, CustomEvent>,
                &EventLoopWindowTarget<CustomEvent>,
                &mut ControlFlow,
            ));
            RUN_FN_TLS.set(&mut run_fn, move || {
                self.winit_loop.run(|e, t, cf| RUN_FN_TLS.with(|mut run_fn| run_fn(e, t, cf)))
            });
        }
    }

    /// Returns a reference to the backing winit event loop.
    pub fn get_winit_event_loop(&self) -> &winit::event_loop::EventLoop<CustomEvent> {
        &self.winit_loop
    }
}