use std::collections::VecDeque;

use cocoa::{
    appkit::{self, NSEvent},
    base::id,
};
use objc2::foundation::NSObject;
use objc2::{declare_class, ClassType};

use super::appkit::{NSApplication, NSResponder};
use super::{app_state::AppState, event::EventWrapper, util, DEVICE_ID};
use crate::event::{DeviceEvent, ElementState, Event};

declare_class!(
    #[derive(Debug, PartialEq, Eq, Hash)]
    pub(super) struct WinitApplication {}

    unsafe impl ClassType for WinitApplication {
        #[inherits(NSResponder, NSObject)]
        type Super = NSApplication;
    }

    unsafe impl WinitApplication {
        // Normally, holding Cmd + any key never sends us a `keyUp` event for that key.
        // Overriding `sendEvent:` like this fixes that. (https://stackoverflow.com/a/15294196)
        // Fun fact: Firefox still has this bug! (https://bugzilla.mozilla.org/show_bug.cgi?id=1299553)
        #[sel(sendEvent:)]
        fn send_event(&self, event: id) {
            unsafe {
                // For posterity, there are some undocumented event types
                // (https://github.com/servo/cocoa-rs/issues/155)
                // but that doesn't really matter here.
                let event_type = event.eventType();
                let modifier_flags = event.modifierFlags();
                if event_type == appkit::NSKeyUp
                    && util::has_flag(
                        modifier_flags,
                        appkit::NSEventModifierFlags::NSCommandKeyMask,
                    )
                {
                    let key_window: id = msg_send![self, keyWindow];
                    let _: () = msg_send![key_window, sendEvent: event];
                } else {
                    maybe_dispatch_device_event(event);
                    let _: () = msg_send![super(self), sendEvent: event];
                }
            }
        }
    }
);

unsafe fn maybe_dispatch_device_event(event: id) {
    let event_type = event.eventType();
    match event_type {
        appkit::NSMouseMoved
        | appkit::NSLeftMouseDragged
        | appkit::NSOtherMouseDragged
        | appkit::NSRightMouseDragged => {
            let mut events = VecDeque::with_capacity(3);

            let delta_x = event.deltaX() as f64;
            let delta_y = event.deltaY() as f64;

            if delta_x != 0.0 {
                events.push_back(EventWrapper::StaticEvent(Event::DeviceEvent {
                    device_id: DEVICE_ID,
                    event: DeviceEvent::Motion {
                        axis: 0,
                        value: delta_x,
                    },
                }));
            }

            if delta_y != 0.0 {
                events.push_back(EventWrapper::StaticEvent(Event::DeviceEvent {
                    device_id: DEVICE_ID,
                    event: DeviceEvent::Motion {
                        axis: 1,
                        value: delta_y,
                    },
                }));
            }

            if delta_x != 0.0 || delta_y != 0.0 {
                events.push_back(EventWrapper::StaticEvent(Event::DeviceEvent {
                    device_id: DEVICE_ID,
                    event: DeviceEvent::MouseMotion {
                        delta: (delta_x, delta_y),
                    },
                }));
            }

            AppState::queue_events(events);
        }
        appkit::NSLeftMouseDown | appkit::NSRightMouseDown | appkit::NSOtherMouseDown => {
            let mut events = VecDeque::with_capacity(1);

            events.push_back(EventWrapper::StaticEvent(Event::DeviceEvent {
                device_id: DEVICE_ID,
                event: DeviceEvent::Button {
                    button: event.buttonNumber() as u32,
                    state: ElementState::Pressed,
                },
            }));

            AppState::queue_events(events);
        }
        appkit::NSLeftMouseUp | appkit::NSRightMouseUp | appkit::NSOtherMouseUp => {
            let mut events = VecDeque::with_capacity(1);

            events.push_back(EventWrapper::StaticEvent(Event::DeviceEvent {
                device_id: DEVICE_ID,
                event: DeviceEvent::Button {
                    button: event.buttonNumber() as u32,
                    state: ElementState::Released,
                },
            }));

            AppState::queue_events(events);
        }
        _ => (),
    }
}