src/main/org/apache/tools/ant/types/resources/BaseResourceCollectionContainer.java

/*
 *  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
 *
 *      https://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.tools.ant.types.resources;

import java.io.File;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Stack;
import java.util.stream.Collectors;

import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.Project;
import org.apache.tools.ant.types.DataType;
import org.apache.tools.ant.types.Resource;
import org.apache.tools.ant.types.ResourceCollection;

/**
 * Base class for ResourceCollections that nest multiple ResourceCollections.
 * @since Ant 1.7
 */
public abstract class BaseResourceCollectionContainer
        extends DataType implements AppendableResourceCollection, Cloneable {
    private List<ResourceCollection> rc = new ArrayList<>();
    private Collection<Resource> coll = null;
    private boolean cache = true;

    /**
     * Create a new BaseResourceCollectionContainer.
     */
    public BaseResourceCollectionContainer() {
    }

    /**
     * Create a new BaseResourceCollectionContainer.
     * @param project Project
     * @since Ant 1.8
     */
    public BaseResourceCollectionContainer(Project project) {
        setProject(project);
    }

    /**
     * Set whether to cache collections.
     * @param b boolean cache flag.
     */
    public synchronized void setCache(boolean b) {
        cache = b;
    }

    /**
     * Learn whether to cache collections. Default is <code>true</code>.
     * @return boolean cache flag.
     */
    public synchronized boolean isCache() {
        return cache;
    }

    /**
     * Clear the container.
     * @throws BuildException on error.
     */
    public synchronized void clear() throws BuildException {
        if (isReference()) {
            throw noChildrenAllowed();
        }
        rc.clear();
        FailFast.invalidate(this);
        coll = null;
        setChecked(false);
    }

    /**
     * Add a ResourceCollection to the container.
     * @param c the ResourceCollection to add.
     * @throws BuildException on error.
     */
    @Override
    public synchronized void add(ResourceCollection c) throws BuildException {
        if (isReference()) {
            throw noChildrenAllowed();
        }
        if (c == null) {
            return;
        }
        if (Project.getProject(c) == null) {
            Project p = getProject();
            if (p != null) {
                p.setProjectReference(c);
            }
        }
        rc.add(c);
        FailFast.invalidate(this);
        coll = null;
        setChecked(false);
    }

    /**
     * Add the Collection of ResourceCollections to the container.
     * @param c the Collection whose elements to add.
     * @throws BuildException on error.
     */
    public synchronized void addAll(Collection<? extends ResourceCollection> c) throws BuildException {
        if (isReference()) {
            throw noChildrenAllowed();
        }
        try {
            c.forEach(this::add);
        } catch (ClassCastException e) {
            throw new BuildException(e);
        }
    }

    /**
     * Fulfill the ResourceCollection contract. The Iterator returned
     * will throw ConcurrentModificationExceptions if ResourceCollections
     * are added to this container while the Iterator is in use.
     * @return a "fail-fast" Iterator.
     */
    @Override
    public final synchronized Iterator<Resource> iterator() {
        if (isReference()) {
            return getRef().iterator();
        }
        dieOnCircularReference();
        return new FailFast(this, cacheCollection().iterator());
    }

    /**
     * Fulfill the ResourceCollection contract.
     * @return number of elements as int.
     */
    @Override
    public synchronized int size() {
        if (isReference()) {
            return getRef().size();
        }
        dieOnCircularReference();
        return cacheCollection().size();
    }

    /**
     * Fulfill the ResourceCollection contract.
     * @return whether this is a filesystem-only resource collection.
     */
    @Override
    public synchronized boolean isFilesystemOnly() {
        if (isReference()) {
            return getRef().isFilesystemOnly();
        }
        dieOnCircularReference();
        //first the easy way, if all children are filesystem-only, return true:
        if (rc.stream().allMatch(ResourceCollection::isFilesystemOnly)) {
            return true;
        }
        /* now check each Resource in case the child only
           lets through files from any children IT may have: */
        return cacheCollection().stream()
            .allMatch(r -> r.asOptional(FileProvider.class).isPresent());
    }

    /**
     * Overrides the version of DataType to recurse on all DataType
     * child elements that may have been added.
     * @param stk the stack of data types to use (recursively).
     * @param p   the project to use to dereference the references.
     * @throws BuildException on error.
     */
    protected synchronized void dieOnCircularReference(Stack<Object> stk, Project p)
        throws BuildException {
        if (isChecked()) {
            return;
        }
        if (isReference()) {
            super.dieOnCircularReference(stk, p);
        } else {
            for (ResourceCollection resourceCollection : rc) {
                if (resourceCollection instanceof DataType) {
                    pushAndInvokeCircularReferenceCheck((DataType) resourceCollection, stk, p);
                }
            }
            setChecked(true);
        }
    }

    /**
     * Get the nested ResourceCollections.
     * @return List.
     */
    public final synchronized List<ResourceCollection> getResourceCollections() {
        dieOnCircularReference();
        return Collections.unmodifiableList(rc);
    }

    /**
     * Template method for subclasses to return a Collection object of Resources.
     * @return Collection.
     */
    protected abstract Collection<Resource> getCollection();

    /**
     * Implement clone.  The set of nested resource
     * collections is shallowly cloned.
     * @return a cloned instance.
     */
    @Override
    public Object clone() {
        try {
            BaseResourceCollectionContainer c
                = (BaseResourceCollectionContainer) super.clone();
            c.rc = new ArrayList<>(rc);
            c.coll = null;
            return c;
        } catch (CloneNotSupportedException e) {
            throw new BuildException(e);
        }
    }

    /**
     * Format this BaseResourceCollectionContainer as a String.
     * @return a descriptive <code>String</code>.
     */
    @Override
    public synchronized String toString() {
        if (isReference()) {
            return getRef().toString();
        }
        if (cacheCollection().isEmpty()) {
            return "";
        }
        return coll.stream().map(Object::toString)
            .collect(Collectors.joining(File.pathSeparator));
    }

     private BaseResourceCollectionContainer getRef() {
        return getCheckedRef(BaseResourceCollectionContainer.class);
    }

    private synchronized Collection<Resource> cacheCollection() {
        if (coll == null || !isCache()) {
            coll = getCollection();
        }
        return coll;
    }

}