/* Copyright (c) 2009 Google Inc.
*
* 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 com.google.wave.api;
import java.io.Serializable;
import java.util.Collection;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.Set;
/**
* A class that represents wavelet's tags. This class supports various
* tag related operations, such as, adding or removing tag from a wavelet.
*/
public class Tags implements Iterable<String>, Serializable {
/** A set of string that represents wavelet tags. */
private final Set<String> tags;
/** The wavelet that this tag list represents. */
private final Wavelet wavelet;
/** The operation queue to queue operation to the robot proxy. */
private final OperationQueue operationQueue;
/**
* Constructor.
*
* @param tags a collection of initial tags of the wavelet.
* @param wavelet the wavelet that this tag list represents.
* @param operationQueue the operation queue to queue operation to the robot
* proxy.
*/
public Tags(Collection<String> tags, Wavelet wavelet, OperationQueue operationQueue) {
this.tags = new LinkedHashSet<String>(tags);
this.wavelet = wavelet;
this.operationQueue = operationQueue;
}
/**
* Adds the given tag id if it doesn't exist.
*
* @param tag the tag that will be added.
* @return {@code true} if the given tag does not exist yet
* in the owning wavelet, which means that a new
* {@code wavelet.modifyTag()} has been queued. Otherwise, returns
* {@code false}.
*/
public boolean add(String tag) {
if (tags.contains(tag)) {
return false;
}
operationQueue.modifyTagOfWavelet(wavelet, tag, "add");
tags.add(tag);
return true;
}
/**
* Removes the given tag id if it exists.
*
* @param tag the tag that will be removed.
* @return {@code true} if the given tag exists in the owning wavelet, which
* means that a new {@code wavelet.modifyTag()} has been queued.
* Otherwise, returns {@code false}.
*/
public boolean remove(String tag) {
if (!tags.contains(tag)) {
return false;
}
operationQueue.modifyTagOfWavelet(wavelet, tag, "remove");
tags.remove(tag);
return true;
}
/**
* Checks whether the owning wavelet has the given tag or not.
*
* @param tag the name of the tag to check.
* @return {@code true} if the wavelet has the given tag.
* Otherwise, returns {@code false}.
*/
public boolean contains(String tag) {
return tags.contains(tag);
}
/**
* Returns the number of tags in the owning wavelet.
*
* @return the number of tags.
*/
public int size() {
return tags.size();
}
/**
* Checks whether the owning wavelet has any tag or not.
*
* @return {@code true} if the owning wavelet has at least one tag. Otherwise,
* returns {@code false}.
*/
public boolean isEmpty() {
return tags.isEmpty();
}
@Override
public Iterator<String> iterator() {
return new TagsIterator();
}
/**
* An iterator for {@link Tags}.
*/
private class TagsIterator implements Iterator<String> {
/** The iterator of the underlying tag store. */
private final Iterator<String> storeIterator;
/** The pointer to the current tag. */
private String currentTag;
/** A flag that denotes whether {@link #remove} has been called or not. */
private boolean removeCalled;
/**
* Constructor.
*/
private TagsIterator() {
this.storeIterator = tags.iterator();
}
@Override
public boolean hasNext() {
return storeIterator.hasNext();
}
@Override
public String next() {
removeCalled = false;
currentTag = storeIterator.next();
return currentTag;
}
@Override
public void remove() {
if (removeCalled) {
throw new IllegalStateException("remove() has been called after the last call to next().");
}
if (currentTag == null) {
throw new IllegalStateException("Please call next() first before calling remove().");
}
removeCalled = true;
operationQueue.modifyTagOfWavelet(wavelet, currentTag, "remove");
storeIterator.remove();
}
}
}