CollectionFilter.java

/*
 * Copyright 2011 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.gradle.api.internal.collections;

import org.gradle.api.specs.Spec;
import org.gradle.api.specs.Specs;

/**
 * @param T filtered type
 */
public class CollectionFilter<T> implements Spec<T> {

    private Class<? extends T> type;
    private Spec<? super T> spec;

    public CollectionFilter(Class<T> type) {
        this(type, Specs.<T>satisfyAll());
    }

    public CollectionFilter(Class<? extends T> type, Spec<? super T> spec) {
        this.type = type;
        this.spec = spec;
    }

    public Class<? extends T> getType() {
        return type;
    }

    public T filter(Object object) {
        if (!type.isInstance(object)) {
            return null;
        }

        T t = type.cast(object);
        if (spec.isSatisfiedBy(t)) {
            return t;
        } else {
            return null;
        }
    }

    public boolean isSatisfiedBy(T element) {
        return filter(element) != null;
    }

    @SuppressWarnings("unchecked")
    public <S extends T> CollectionFilter<S> and(CollectionFilter<S> other) {
        return new CollectionFilter<S>(other.type, Specs.intersect(spec, other.spec));
    }
}