org.waveprotocol.wave.examples.fedone.common.DeltaSequence.java Source code

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Here is the source code for org.waveprotocol.wave.examples.fedone.common.DeltaSequence.java

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/**
 * Copyright 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 org.waveprotocol.wave.examples.fedone.common;

import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;

import org.waveprotocol.wave.federation.Proto.ProtocolHashedVersion;
import org.waveprotocol.wave.federation.Proto.ProtocolWaveletDelta;

import java.util.AbstractList;
import java.util.Iterator;
import java.util.List;

/**
 * A sequence of deltas along with the end version (after application of the
 * deltas).
 *
 *
 */
public final class DeltaSequence extends AbstractList<ProtocolWaveletDelta> {
    private final ImmutableList<ProtocolWaveletDelta> deltas;
    private final ProtocolHashedVersion endVersion;

    public static DeltaSequence empty(ProtocolHashedVersion version) {
        return new DeltaSequence(ImmutableList.<ProtocolWaveletDelta>of(), version);
    }

    /**
     * @param deltas to apply to a wavelet
     * @param endVersion the version of the wavelet after all deltas were applied
     */
    public DeltaSequence(Iterable<ProtocolWaveletDelta> deltas, ProtocolHashedVersion endVersion) {
        this.deltas = ImmutableList.copyOf(deltas);
        this.endVersion = endVersion;
        Preconditions.checkArgument(endVersion.getVersion() >= 0, "Expected endVersion >= 0, got %s",
                endVersion.getVersion());
        checkDeltaVersions();
    }

    /**
     * @throws IllegalArgumentException if any of the deltas' end version disagrees
     *         with the next delta's version or (if it's the last delta), endVersion.
     */
    private void checkDeltaVersions() {
        for (int i = 0; i < deltas.size(); i++) {
            ProtocolWaveletDelta delta = deltas.get(i);
            long deltaEndVersion = delta.getHashedVersion().getVersion() + delta.getOperationCount();
            long nextVersion = ((i + 1 < deltas.size()) ? deltas.get(i + 1).getHashedVersion() : endVersion)
                    .getVersion();
            Preconditions.checkArgument(deltaEndVersion == nextVersion,
                    "Delta %s / %s ends at version %s, expected %s", i + 1, deltas.size(), deltaEndVersion,
                    nextVersion);
        }
    }

    @Override
    public DeltaSequence subList(int start, int end) {
        List<ProtocolWaveletDelta> subDeltas = deltas.subList(start, end);
        ProtocolHashedVersion subEndVersion = (end == deltas.size()) ? endVersion
                : deltas.get(end).getHashedVersion();
        return new DeltaSequence(subDeltas, subEndVersion);
    }

    /**
     * Constructs a DeltaSequence which consists of the specified deltas
     * followed by this sequence's deltas.
     */
    public DeltaSequence prepend(Iterable<ProtocolWaveletDelta> prefixDeltas) {
        return new DeltaSequence(Iterables.concat(prefixDeltas, deltas), endVersion);
    }

    public List<ProtocolWaveletDelta> getDeltas() {
        return deltas;
    }

    public ProtocolHashedVersion getStartVersion() {
        return deltas.isEmpty() ? endVersion : deltas.get(0).getHashedVersion();
    }

    public ProtocolHashedVersion getEndVersion() {
        return endVersion;
    }

    @Override
    public boolean isEmpty() {
        return deltas.isEmpty();
    }

    @Override
    public int size() {
        return deltas.size();
    }

    @Override
    public ProtocolWaveletDelta get(int index) {
        return deltas.get(index);
    }

    @Override
    public Iterator<ProtocolWaveletDelta> iterator() {
        return deltas.iterator();
    }

    @Override
    public String toString() {
        return String.format("%d delta%s (version %s .. %s): %s", deltas.size(), (deltas.size() == 1 ? "" : "s"),
                getStartVersion(), getEndVersion(), deltas);
    }
}