de.schlegel11.lambdadecor.DefaultBehaviour Maven / Gradle / Ivy

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package de.schlegel11.lambdadecor;

import java.util.Objects;
import java.util.function.Function;

/**
 * @author Marcel Schlegel (schlegel11)
 * @since 1.0
 */
public class DefaultBehaviour implements Behaviour {

    private final Function, DecorPair> behaviour;

    private DefaultBehaviour() {
        this(Function.identity());
    }

    private DefaultBehaviour(Function, DecorPair> behaviour) {
        this.behaviour = Objects.requireNonNull(behaviour, "Behaviour is null.");
    }

    /**
     * Creates a new instance.
     *
     * @param function the {@link Function} that provides an new {@link DefaultBehaviour} instance and returns one.
     * @param       type for this behaviour
     * @return the new instance
     * @throws NullPointerException if the {@code function} is null
     */
    public static  Behaviour newBehaviour(final Function, Behaviour>
                                                        function) {
        Objects.requireNonNull(function, "Function is null.");
        return function.apply(newBehaviour());
    }

    /**
     * Creates a new instance.
     *
     * @param  type for this behaviour
     * @return the new instance
     */
    public static  Behaviour newBehaviour() {
        return new DefaultBehaviour<>();
    }

    public final Behaviour withUnapply(final Function function) {
        Objects.requireNonNull(function, "Function is null.");
        return new DefaultBehaviour<>(
                behaviour.andThen(t -> t.updateUnapply(u -> u.andThen(function.apply(t._Behaviour)))));
    }

    public final Behaviour with(final Function function) {
        Objects.requireNonNull(function, "Function is null.");
        return new DefaultBehaviour<>(behaviour.andThen(t -> t.updateBehaviour(function.apply(t._Behaviour))));
    }

    public final Behaviour merge(final Behaviour other) {
        Objects.requireNonNull(other, "Behaviour is null.");
        return new DefaultBehaviour<>(behaviour.andThen(p -> {
            DecorPair pair = other.apply(p._Behaviour);
            return p.updateBehaviour(pair._Behaviour)
                    .updateUnapply(u -> u.andThen(pair._Unapply));
        }));
    }

    public final DecorPair apply(final T type) {
        return behaviour.apply(DecorPair.create(type, Unappliable.EMPTY));
    }
}