use bevy::{
  color::palettes::css::*,
  ecs::{component::HookContext, world::DeferredWorld},
  prelude::*,
  ui::Val::*,
};

use crate::game::consumables::{Fuel, FuelChanged};

#[derive(Component)]
#[require(Label)]
#[component(on_add = FuelGauge::refresh_label)]
pub struct FuelGauge(Entity);

impl FuelGauge {
  /// Default bundle for a machine's fuel gauge widget. Give it the ID of the
  /// machine whose info it is displaying.
  pub fn bundle(target: Entity) -> impl Bundle {
    (
      FuelGauge(target),
      Node {
        min_width: Px(20.0),
        min_height: Px(10.0),
        ..default()
      },
      BackgroundColor(GREEN.into()),
      Text::new("Fuel: "),
    )
  }

  /// Observer system to update the [`FuelGauge`] widget when a machine emits a
  /// [`FuelChanged`] event.
  pub fn detect_fuel_change(
    event: Trigger<FuelChanged>,
    fuel_levels: Query<&Fuel>,
    mut gauges: Query<(&FuelGauge, &mut Text)>,
  ) {
    // Find the FuelGauge that references the same Entity as the event target.
    // That gauge's `Text` is the one to update.
    let (_, mut label) = gauges
      .iter_mut()
      .find(|(gauge, _label)| gauge.0 == event.target())
      .expect("Couldn't find any fuel gauges");

    let fuel = fuel_levels.get(event.target()).expect(
      "Logic error: a `FuelChanged` event was targetted at an entity with no `Fuel` component.",
    );
    label.0 = format!("Fuel: {}", fuel.0);
  }

  fn refresh_label(mut world: DeferredWorld, ctx: HookContext) {
    // Get the machine ID from the FuelGauge component.
    let Some(machine_id) = world.get::<FuelGauge>(ctx.entity).map(|fg| fg.0) else {
      panic!("Couldn't get a FuelGauge during it's on-add hook run!");
    };
    // and fuel level
    let Some(fuel) = world.get::<Fuel>(machine_id).map(|lvl| lvl.0) else {
      // TODO: Maybe don't panic and just emit a warning.
      panic!("Couldn't get a Fuel for a machine during a FuelGauge on-add hook.");
    };

    // Get an excl ref to the Text component so we can redraw its text
    let Some(mut label) = world.get_mut::<Text>(ctx.entity) else {
      panic!()
    };

    label.0 = format!("Fuel: {}", fuel);
  }
}