/**
 * 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.model.version;

import org.waveprotocol.wave.model.id.IdURIEncoderDecoder;
import org.waveprotocol.wave.model.id.WaveletName;
import org.waveprotocol.wave.model.id.URIEncoderDecoder.EncodingException;

import java.io.UnsupportedEncodingException;

/**
 * Hashed version factory only capable of calculating hashes for version zero. A
 * version-zero hash requires no cryptographic calculations.
 */
public class HashedVersionZeroFactoryImpl implements HashedVersionFactory {

  private final IdURIEncoderDecoder uriCodec;

  public HashedVersionZeroFactoryImpl(IdURIEncoderDecoder uriCodec) {
    this.uriCodec = uriCodec;
  }

  @Override
  public HashedVersion createVersionZero(WaveletName waveletName) {
    try {
      // Same encoding as used protobuf/CodedOutputSteam to serialize a String to byte[].
      // http://code.google.com/p/protobuf/source/browse/trunk/java/src/main/java/com/google/protobuf/CodedOutputStream.java
      byte[] historyHash = uriCodec.waveletNameToURI(waveletName).getBytes("UTF-8");
      return HashedVersion.of(0, historyHash);
    } catch (EncodingException e) {
      throw new IllegalArgumentException("Bad wavelet name " + waveletName, e);
    } catch (UnsupportedEncodingException e) { // From getBytes().
      throw new IllegalStateException("UTF-8 unsupported in creating version zero hash", e);
    }
  }

  /**
   * Versions != zero are not supported by this factory.
   *
   * @throws UnsupportedOperationException always
   */
  @Override
  public HashedVersion create(byte[] appliedDeltaBytes, HashedVersion hashedVersionAppliedAt,
      int operationsApplied) {
    // For lightweight users of this factory there are no deps on crypto code.
    throw new UnsupportedOperationException("This factory can only create hashed version zero.");
  }
}