QObjectReaction.java

package org.andork.q2.react;

import java.util.HashMap;
import java.util.Map;

import org.andork.q2.QObject;
import org.andork.q2.QObjectListener;
import org.andork.q2.QSpec;
import org.andork.q2.QSpec.Property;
import org.andork.react.FunctionReaction;
import org.andork.react.Reactable;
import org.andork.react.Reaction;

public class QObjectReaction<S extends QSpec> extends Reaction<QObject<? extends S>> implements QObjectListener {
	private final S spec;

	private final Reactable<QObject<? extends S>> input;
	private final Map<Property<?>, Reaction<?>> reactions = new HashMap<>();

	public QObjectReaction(S spec, Reactable<QObject<? extends S>> input) {
		this.spec = spec;
		this.input = input;
		input.bind(this);
	}

	@Override
	protected QObject<? extends S> calculate() {
		return input.get();
	}

	@Override
	public void objectChanged(QObject<?> source, Property<?> property, Object oldValue, Object newValue) {
		if (isValid() && source == get()) {
			Reaction<?> reaction = reactions.get(property);
			if (reaction != null) {
				reaction.invalidate();
			}
		}
	}

	@Override
	protected void onValueChanged(QObject<? extends S> oldValue, QObject<? extends S> newValue) {
		if (oldValue != null) {
			oldValue.removeListener(this);
		}

		if (newValue != null) {
			newValue.addListener(this);
		}
	}

	@SuppressWarnings("unchecked")
	public <T> Reaction<T> react(final Property<T> property) {
		property.requirePropertyOf(spec);
		Reaction<T> reaction = (Reaction<T>) reactions.get(property);
		if (reaction == null) {
			reaction = new FunctionReaction<>(this, q -> q == null ? null : q.get(property));
			reactions.put(property, reaction);
		}
		return reaction;
	}
}