/*-
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.sling.query.impl.function;

import java.util.Iterator;
import java.util.function.Predicate;

import org.apache.sling.query.api.SearchStrategy;
import org.apache.sling.query.api.internal.ElementToIteratorFunction;
import org.apache.sling.query.api.internal.IteratorToIteratorFunction;
import org.apache.sling.query.api.internal.Option;
import org.apache.sling.query.api.internal.TreeProvider;
import org.apache.sling.query.impl.iterator.EmptyElementFilter;
import org.apache.sling.query.impl.selector.SelectorFunction;
import org.apache.sling.query.impl.util.IteratorUtils;

public class HasFunction<T> implements ElementToIteratorFunction<T> {

    private final IteratorToIteratorFunction<T> findFunction;

    private final IteratorToIteratorFunction<T> filter;

    private HasFunction(FindFunction<T> findFunction, IteratorToIteratorFunction<T> filter) {
        this.findFunction = new IteratorToIteratorFunctionWrapper<T>(findFunction);
        this.filter = filter;
    }

    public HasFunction(String selectorString, SearchStrategy searchStrategy, TreeProvider<T> provider) {
        this(new FindFunction<T>(searchStrategy, provider, selectorString),
                new SelectorFunction<T>(selectorString, provider, searchStrategy));
    }

    public HasFunction(Predicate<T> predicate, SearchStrategy searchStrategy, TreeProvider<T> provider) {
        this(new FindFunction<>(searchStrategy, provider, ""), new FilterFunction<T>(predicate));
    }

    public HasFunction(Iterable<T> iterable, TreeProvider<T> provider) {
        this.findFunction = new DescendantFunction<>(iterable, provider);
        this.filter = new IdentityFunction<>();
    }

    @Override
    public Iterator<T> apply(T input) {
        Iterator<Option<T>> iterator = IteratorUtils.singleElementIterator(Option.of(input, 0));
        iterator = findFunction.apply(iterator);
        iterator = filter.apply(iterator);
        if (new EmptyElementFilter<>(iterator).hasNext()) {
            return IteratorUtils.singleElementIterator(input);
        } else {
            return IteratorUtils.emptyIterator();
        }
    }
}