/*
 *  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.Iterator;
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 a ResourceCollection that wraps a single nested
ResourceCollection.
Since:
Ant 1.8.2/**
 * Base class for a ResourceCollection that wraps a single nested
 * ResourceCollection.
 * @since Ant 1.8.2
 */
public abstract class AbstractResourceCollectionWrapper
    extends DataType implements ResourceCollection, Cloneable {
    private static final String ONE_NESTED_MESSAGE
        = " expects exactly one nested resource collection.";

    private ResourceCollection rc;
    private boolean cache = true;

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

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

    
Fulfill the ResourceCollection contract.
Returns:
an Iterator of Resources./**
     * Fulfill the ResourceCollection contract.
     * @return an Iterator of Resources.
     */
    @Override
    public final synchronized Iterator<Resource> iterator() {
        if (isReference()) {
            return getRef().iterator();
        }
        dieOnCircularReference();
        return new FailFast(this, createIterator());
    }

    
Do create an iterator on the resource collection. The creation
of the iterator is allowed to not be thread safe whereas the iterator
itself should. The returned iterator will be wrapped into the FailFast
one.
Returns:
the iterator on the resource collection/**
     * Do create an iterator on the resource collection. The creation
     * of the iterator is allowed to not be thread safe whereas the iterator
     * itself should. The returned iterator will be wrapped into the FailFast
     * one.
     *
     * @return the iterator on the resource collection
     */
    protected abstract Iterator<Resource> createIterator();

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

    
Do compute the size of the resource collection. The implementation of
this function is allowed to be not thread safe.
Returns:
size of resource collection./**
     * Do compute the size of the resource collection. The implementation of
     * this function is allowed to be not thread safe.
     *
     * @return size of resource collection.
     */
    protected abstract int getSize();

    
Fulfill the ResourceCollection contract.
Returns:
whether this is a filesystem-only resource collection./**
     * Fulfill the ResourceCollection contract.
     * @return whether this is a filesystem-only resource collection.
     */
    public synchronized boolean isFilesystemOnly() {
        if (isReference()) {
            return getRef().isFilesystemOnly();
        }
        dieOnCircularReference();

        if (rc == null || rc.isFilesystemOnly()) {
            return true;
        }
        /* now check each Resource in case the child only
           lets through files from any children IT may have: */
        for (Resource r : this) {
            if (r.as(FileProvider.class) == null) {
                return false;
            }
        }
        return true;
    }

    
Overrides the version of DataType to recurse on all DataType
child elements that may have been added.
Params:
stk – the stack of data types to use (recursively).
p –   the project to use to dereference the references.
Throws:
BuildException – on error./**
     * 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 {
            if (rc instanceof DataType) {
                pushAndInvokeCircularReferenceCheck((DataType) rc, stk, p);
            }
            setChecked(true);
        }
    }

    
Get the nested ResourceCollection.
Throws:
BuildException – if no nested ResourceCollection has been provided.
Returns:
a ResourceCollection./**
     * Get the nested ResourceCollection.
     * @return a ResourceCollection.
     * @throws BuildException if no nested ResourceCollection has been provided.
     */
    protected final synchronized ResourceCollection getResourceCollection() {
        dieOnCircularReference();
        if (rc == null) {
            throw oneNested();
        }
        return rc;
    }

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

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

    private BuildException oneNested() {
        return new BuildException(super.toString() + ONE_NESTED_MESSAGE);
    }

}