/*
 * 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
 *
 *      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.apache.log4j.util;

import junit.framework.TestCase;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;


/**
 * Utiities for serialization tests.
 *
 * @author Curt Arnold
 */
public class SerializationTestHelper {
  /**
   * Private constructor.
   */
  private SerializationTestHelper() {
  }

  /**
   * Creates a clone by serializing object and
   * deserializing byte stream.
   * @param obj object to serialize and deserialize.
   * @return clone
   * @throws IOException on IO error.
   * @throws ClassNotFoundException if class not found.
   */
  public static Object serializeClone(final Object obj)
    throws IOException, ClassNotFoundException {
    ByteArrayOutputStream memOut = new ByteArrayOutputStream();
    ObjectOutputStream objOut = new ObjectOutputStream(memOut);
    objOut.writeObject(obj);
    objOut.close();

    ByteArrayInputStream src = new ByteArrayInputStream(memOut.toByteArray());
    ObjectInputStream objIs = new ObjectInputStream(src);

    return objIs.readObject();
  }

  /**
   * Deserializes a specified file.
   * @param witness serialization file, may not be null.
   * @return deserialized object.
   * @throws Exception thrown on IO or deserialization exception.
   */
  public static Object deserializeStream(final String witness)
    throws Exception {
    FileInputStream fileIs = new FileInputStream(witness);
    ObjectInputStream objIs = new ObjectInputStream(fileIs);

    return objIs.readObject();
  }

  /**
   * Checks the serialization of an object against an file
   * containing the expected serialization.
   *
   * @param witness name of file containing expected serialization.
   * @param obj object to be serialized.
   * @param skip positions in serialized stream that should not be compared.
   * @param endCompare position to stop comparison.
   * @throws Exception thrown on IO or serialization exception.
   */
  public static void assertSerializationEquals(
    final String witness, final Object obj, final int[] skip,
    final int endCompare) throws Exception {
    ByteArrayOutputStream memOut = new ByteArrayOutputStream();
    ObjectOutputStream objOut = new ObjectOutputStream(memOut);
    objOut.writeObject(obj);
    objOut.close();

    assertStreamEquals(witness, memOut.toByteArray(), skip, endCompare);
  }

  /**
   * Asserts the serialized form of an object.
   * @param witness file name of expected serialization.
   * @param actual byte array of actual serialization.
   * @param skip positions to skip comparison.
   * @param endCompare position to stop comparison.
   * @throws IOException thrown on IO or serialization exception.
   */
  public static void assertStreamEquals(
    final String witness, final byte[] actual, final int[] skip,
    final int endCompare) throws IOException {
    File witnessFile = new File(witness);

    if (witnessFile.exists()) {
      int skipIndex = 0;
      byte[] expected = new byte[actual.length];
      FileInputStream is = new FileInputStream(witnessFile);
      int bytesRead = is.read(expected);
      is.close();

      if(bytesRead < endCompare) {
          TestCase.assertEquals(bytesRead, actual.length);
      }

      int endScan = actual.length;

      if (endScan > endCompare) {
        endScan = endCompare;
      }

      for (int i = 0; i < endScan; i++) {
        if ((skipIndex < skip.length) && (skip[skipIndex] == i)) {
          skipIndex++;
        } else {
          if (expected[i] != actual[i]) {
            TestCase.assertEquals(
              "Difference at offset " + i, expected[i], actual[i]);
          }
        }
      }
    } else {
      //
      //  if the file doesn't exist then
      //      assume that we are setting up and need to write it
      FileOutputStream os = new FileOutputStream(witnessFile);
      os.write(actual);
      os.close();
      TestCase.fail("Writing witness file " + witness);
    }
  }
}