Houses have energy that interact with ghosts (#18)

Reviewed-on: #18
Co-authored-by: Dominic <git@msrd0.de>
Co-committed-by: Dominic <git@msrd0.de>

src/game.rs

@@ -107,12 +107,53 @@ pub fn setup(_state: &mut State, ctx: &mut EngineContext<'_>) {
 	//house::setup(state, ctx);
 }
 
-pub fn update(state: &mut State, engine: &mut EngineContext<'_>) {
-	state.score += engine.delta * 10.0;
+/// The amount of energy a ghost consumes idle.
+pub const GHOST_DISCHARGE_RATE: f32 = 70.0;
+/// The amount of energy additionally consumed by a moving ghost.
+pub const GHOST_DISCHARGE_RATE_MOVEMENT: f32 = 70.0;
+/// The amount of energy a house consumes idle.
+pub const HOUSE_DISCHARGE_RATE: f32 = 30.0;
+/// The amount of energy a ghost can charge when inside a house.
+pub const GHOST_CHARGE_RATE: f32 = 200.0;
+
+pub fn update(state: &mut State, ctx: &mut EngineContext<'_>) {
+	// Update the score. It's based on time.
+	state.score += ctx.delta * 10.0;
+
+	// Update the currently active activity.
 	match state.activity {
-		Activity::House(_) => house::update(state, engine),
-		Activity::Overworld => overworld::update(state, engine)
+		Activity::House(_) => house::update(state, ctx),
+		Activity::Overworld => overworld::update(state, ctx)
 	}
+
+	// We update the charge of houses here - the charge will always decrease, even if the
+	// house is not the current activity.
+	for (house_pos, house) in &mut state.houses {
+		house.charge -= ctx.delta * HOUSE_DISCHARGE_RATE;
+
+		match state.activity {
+			Activity::House(pos) if *house_pos == pos => {
+				// The ghost is currently inside the house. Increase its discarge rate.
+				house.charge -= ctx.delta * GHOST_DISCHARGE_RATE;
+				if house.charge < 0.0 {
+					state.ghost.charge += house.charge;
+					house.charge = 0.0;
+				}
+
+				// And possibly also charge the ghost when inside a house.
+				if state.ghost.charge < state.ghost.max_charge {
+					let charge_transfer = (ctx.delta * GHOST_CHARGE_RATE)
+						.min(state.ghost.max_charge - state.ghost.charge)
+						.min(house.charge);
+					state.ghost.charge += charge_transfer;
+					house.charge -= charge_transfer;
+				}
+			},
+			_ => {}
+		}
+	}
+
+	// Make sure the ghost's charge never drops below 0.
 	state.ghost.charge = state.ghost.charge.max(0.0);
 }