use bevy::prelude::*;
use std::marker::PhantomData;
use tomt_bevycss::prelude::*;

#[derive(Clone, Copy, Debug, Default)]
#[derive(PartialEq, Eq, Hash)]
#[derive(States)]
pub enum GameState
{
    #[default]
    MainMenu,
    InGame,
    PauseMenu,
}

#[derive(Clone, Copy, Debug, Default)]
#[derive(Resource, Reflect)]
enum MainMenuSelection
{
    #[default]
    None,
    NewGame,
    HighScores,
    Options,
    ExitGame,
}

impl std::fmt::Display
for MainMenuSelection
{
    fn fmt(
        &self,
        formatter: &mut std::fmt::Formatter<'_>
    ) -> std::fmt::Result {
        let msg = match *self
        {
            Self::None => "NONE",
            Self::NewGame => "New Game",
            Self::HighScores => "High Scores",
            Self::Options => "Options",
            Self::ExitGame => "Exit Game",
        };
        write!(formatter, "{msg}",)
    }
}

#[derive(Clone, Debug, Default)]
#[derive(PartialEq, Eq)]
#[derive(Component)]
pub struct SpawnedBy<T>(PhantomData<T>);

const CLASS_MAIN_MENU: &str = "main-menu";

fn main(
    // no args
) {
    let mut app = App::new();

    app.add_plugins(DefaultPlugins)
        .add_plugins(BevyCssPlugin::default())
        .register_type::<Class>()
        .register_type::<StyleSheet>();

    app.add_systems(Startup, spawn_camera);

    app.add_state::<GameState>()
        .register_type::<MainMenuSelection>()
        .add_systems(OnEnter(GameState::MainMenu), enter_main_menu)
        .add_systems(OnExit(GameState::MainMenu), exit_main_menu);

    app.run();
}

fn spawn_camera(
    mut commands: Commands
) {
    commands.spawn(Camera2dBundle::default());
}

fn enter_main_menu(
    mut commands: Commands,
    asset_server: Res<AssetServer>
) {
    commands.init_resource::<MainMenuSelection>();

    // UI root entity (CSS attached here)
    commands.spawn(NodeBundle{
            style: Style {
                width: Val::Percent(100.0),
                height: Val::Percent(100.0),
                ..default()
            },
            ..default()
        })
        .insert((
            Name::new("root_ui"),
            SpawnedBy::<MainMenuSelection>::default(),
            StyleSheet::new(asset_server.load("sheets/menu.css")),
            Class::new(CLASS_MAIN_MENU),
        ))
        .with_children(|parent|
        {
            parent.spawn(NodeBundle
                {
                    style: Style {
                        flex_direction: FlexDirection::Column,
                        align_items: AlignItems::Center,
                        ..default()
                    },
                    ..default()
                })
                .with_children(|parent|
                {
                    let mut spawn_btn = |action: MainMenuSelection|
                    {
                        parent.spawn(ButtonBundle::default())
                            .with_children(|parent|
                            {
                                parent.spawn(TextBundle::from_section(
                                    action.to_string(),
                                    TextStyle::default(),
                                ));
                            });
                    };

                    spawn_btn(MainMenuSelection::NewGame);
                    spawn_btn(MainMenuSelection::HighScores);
                    spawn_btn(MainMenuSelection::Options);
                    spawn_btn(MainMenuSelection::ExitGame);
                });
        });
}

fn exit_main_menu(
    mut commands: Commands,
    query: Query<Entity, With<SpawnedBy<MainMenuSelection>>>,
) {
    commands.remove_resource::<MainMenuSelection>();

    for entity in query.iter()
    {
        commands.entity(entity).despawn_recursive();
    }
}