use bevy::prelude::*;
use bevy::window::{CursorGrabMode, PrimaryWindow, WindowResolution};
use bevy::input::{ButtonState, keyboard::KeyboardInput};

pub struct WindowPlugin;

impl Plugin for WindowPlugin
{
    fn build(&self, app: &mut App)
    {
        app.add_systems(PreStartup, setup_window);

        app.add_event::<CursorGrabEvent>();
        app.add_systems(PreUpdate, on_cursor_grab_toggled.run_if(on_event::<KeyboardInput>));
    }
}

#[derive(Event)]
pub struct CursorGrabEvent(pub bool);

fn setup_window(
    mut window: Query<&mut Window, With<PrimaryWindow>>,
) {
    let mut window = window.single_mut();
    window.title = "Bevy FPS Game".to_string();
    window.resolution = WindowResolution::new(1920.0, 1080.0);
    window.position = WindowPosition::Centered(MonitorSelection::Primary);
}

fn on_cursor_grab_toggled(
    mut window: Query<&mut Window, With<PrimaryWindow>>,
    mut events: EventReader<KeyboardInput>,
    mut cursor_events: EventWriter<CursorGrabEvent>,
) {
    let mut window = window.single_mut();

    for _ in events.read()
        .filter(|event| event.key_code == KeyCode::Escape)
        .filter(|event| event.state == ButtonState::Pressed)
    {
        match window.cursor_options.grab_mode
        {
            CursorGrabMode::None => {
                window.cursor_options.visible = false;
                window.cursor_options.grab_mode = CursorGrabMode::Locked;
                cursor_events.send(CursorGrabEvent(true));
            }
            CursorGrabMode::Locked => {
                window.cursor_options.visible = true;
                window.cursor_options.grab_mode = CursorGrabMode::None;
                cursor_events.send(CursorGrabEvent(false));
            }
            _ => panic!("Invalid cursor grab mode"),
        }
    }
}