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Scheduled operations on entities and components.

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package net.mostlyoriginal.api.operation.temporal;

import com.artemis.Component;
import com.artemis.Entity;
import com.artemis.utils.reflect.ClassReflection;
import com.artemis.utils.reflect.ReflectionException;
import com.badlogic.gdx.math.Interpolation;
import com.badlogic.gdx.math.MathUtils;
import net.mostlyoriginal.api.component.common.Tweenable;
import net.mostlyoriginal.api.operation.common.TemporalOperation;
import net.mostlyoriginal.api.plugin.extendedcomponentmapper.M;
import net.mostlyoriginal.api.utils.Preconditions;

/**
 * Tween between two managed component states.
 * 
 * From/to states are owned by this class, safe from garbage collection.
 *
 * @author Daan van Yperen
 */
public abstract class TweenOperation extends TemporalOperation {

	protected final Component a;
	protected final Component b;
	protected M m;

	public TweenOperation(Class type) {
		try {
			a = ClassReflection.newInstance(type);
			b = ClassReflection.newInstance(type);
		} catch (ReflectionException e) {
			String error = "Couldn't instantiate object of type " + type.getName();
			throw new RuntimeException(error, e);
		}
	}

	@Override
	public void act(float percentage, Entity e) {
		applyTween(e, percentage);
	}

	@SuppressWarnings("unchecked")
	protected final void applyTween(Entity e, float a) {

		if (m == null) {
			// resolve component mapper if not set yet.
			// gets cleared every reset for non managed tweens.
			m = M.getFor(this.a.getClass(), e.getWorld());
		}

		// apply tween to component, create if missing.
		((Tweenable) m.create(e))
				.tween(this.a, b, MathUtils.clamp(a, 0, 1));
	}

	public TweenOperation setup(Interpolation interpolation, float duration) {
		Preconditions.checkArgument(duration != 0, "Duration cannot be zero.");
		this.interpolation = Preconditions.checkNotNull(interpolation);
		this.duration = duration;
		return this;
	}

	@Override
	public void reset() {
		super.reset();
		m = null; // might be after world reset.
	}

	@SuppressWarnings("unchecked")
	public final T getFrom() {
		return (T) a;
	}

	@SuppressWarnings("unchecked")
	public final T getTo() {
		return (T) b;
	}
}