/**
* Copyright 2011 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 org.waveprotocol.wave.client.wave;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Preconditions;
import org.waveprotocol.wave.model.document.operation.DocInitialization;
import org.waveprotocol.wave.model.document.operation.DocOp;
import org.waveprotocol.wave.model.document.operation.algorithm.Composer;
import org.waveprotocol.wave.model.document.operation.algorithm.DocOpCollector;
import org.waveprotocol.wave.model.operation.OperationException;
import org.waveprotocol.wave.model.operation.OperationRuntimeException;
/**
* Represents a diff document as a pair of an initialization (containing all the
* read information) and an op (containing all the unread information).
* <p>
* This object is mutable by operation consumption.
*
* @author hearnden@google.com (David Hearnden)
*/
public final class SimpleDiffDoc implements DiffSink {
/** The base state. Never null. */
private DocInitialization state;
/** The diff. Null means no-op. */
private DocOpCollector diff;
/**
* Creates a diff initialization.
*/
private SimpleDiffDoc(DocInitialization base) {
this.state = base;
}
/**
* Creates a diff initialization.
*/
public static SimpleDiffDoc create(DocInitialization base, DocOp diff) {
Preconditions.checkNotNull(base);
SimpleDiffDoc init = new SimpleDiffDoc(base);
if (diff != null) {
init.consumeAsDiff(diff);
}
return init;
}
@Override
public void consume(DocOp op) {
// Rebase is not supported.
Preconditions.checkState(diff == null, "Can not apply non-diff ops while diffs still exist");
state = compose(state, op);
}
@Override
public void consumeAsDiff(DocOp op) {
if (diff == null) {
diff = new DocOpCollector();
}
diff.add(op);
}
@Override
public void clearDiffs() {
state = asOperation();
diff = null;
}
/**
* Applies this state (base + diff) to another diff-aware target.
*
* @param target target to which this diff state is pushed
*/
void applyTo(DiffSink target) {
target.consume(state);
if (diff != null) {
target.consumeAsDiff(diff.composeAll());
}
}
@Override
public DocInitialization asOperation() {
return compose(state, diff != null ? diff.composeAll() : null);
}
/** @return true iff this is just a diff (there is no base state). */
boolean isCompleteDiff() {
return state.size() == 0;
}
@VisibleForTesting
boolean isCompleteState() {
return state.size() > 0 && (diff == null || diff.isEmpty());
}
/**
* @return this state into a single operation.
*/
private static DocInitialization compose(DocInitialization state, DocOp diff) {
try {
return diff != null ? Composer.compose(state, diff) : state;
} catch (OperationException e) {
throw new OperationRuntimeException("error occurred during diff compaction", e);
}
}
}