/*
    * Licensed to The Apereo Foundation under one or more contributor license
    * agreements. See the NOTICE file distributed with this work for additional
    * information regarding copyright ownership.
    *
    *
    * The Apereo Foundation licenses this file to you under the Educational
    * Community 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://opensource.org/licenses/ecl2.txt
   *
   * 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.opencastproject.util;
  
  import java.io.BufferedInputStream;
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.Serializable;
  import java.security.MessageDigest;
  import java.security.NoSuchAlgorithmException;
  
  import javax.xml.bind.annotation.XmlAccessType;
  import javax.xml.bind.annotation.XmlAccessorType;
  import javax.xml.bind.annotation.XmlAttribute;
  import javax.xml.bind.annotation.XmlType;
  import javax.xml.bind.annotation.XmlValue;
  
  /**
   * This class stores value and type of a generated checksum.
   */
  @XmlAccessorType(XmlAccessType.NONE)
  @XmlType(name = "checksum", namespace = "http://mediapackage.opencastproject.org")
  public final class Checksum implements Serializable {
  
    /** Serial version uid */
    private static final long serialVersionUID = 1L;
  
    /** The checksum value */
    @XmlValue
    protected String value = null;
  
    /** The checksum type */
    @XmlAttribute(name = "type")
    protected ChecksumType type = null;
  
    /** Needed by JAXB */
    public Checksum() {
    }
  
    /**
     * Creates a new checksum object of the specified value and checksum type.
     *
     * @param value
     *          the value
     * @param type
     *          the type
     */
    private Checksum(String value, ChecksumType type) {
      if (value == null)
        throw new IllegalArgumentException("Checksum value is null");
      if (type == null)
        throw new IllegalArgumentException("Checksum type is null");
      this.value = value;
      this.type = type;
    }
  
    /**
     * Returns the checksum type.
     *
     * @return the type
     */
    public ChecksumType getType() {
      return type;
    }
  
    /**
     * Returns the checksum value.
     *
     * @return the value
     */
    public String getValue() {
      return value;
    }
  
    /**
     * Converts the checksum to a hex string.
     *
    * @param data
    *          the digest
    * @return the digest hex representation
    */
   public static String convertToHex(byte[] data) {
     final StringBuffer buf = new StringBuffer();
     for (int i = 0; i < data.length; i++) {
       int halfbyte = (data[i] >>> 4) & 0x0F;
       int twoHalfs = 0;
       do {
         if ((0 <= halfbyte) && (halfbyte <= 9))
           buf.append((char) ('0' + halfbyte));
         else
           buf.append((char) ('a' + (halfbyte - 10)));
         halfbyte = data[i] & 0x0F;
       } while (twoHalfs++ < 1);
     }
     return buf.toString();
   }
 
   @Override
   public boolean equals(Object obj) {
     if (obj instanceof Checksum) {
       Checksum c = (Checksum) obj;
       return type.equals(c.type) && value.equals(c.value);
     }
     return false;
   }
 
   @Override
   public int hashCode() {
     return value.hashCode();
   }
 
   @Override
   public String toString() {
     return value + " (" + type + ")";
   }
 
   /**
    * Creates a checksum from a string in the form "value (type)".
    *
    * @param checksum
    *         the checksum in string form
    * @return the checksum
    * @throws NoSuchAlgorithmException
    *           if the checksum of the specified type cannot be created
    */
   public static Checksum fromString(String checksum) throws NoSuchAlgorithmException {
     String[] checksumParts = checksum.split(" ");
 
     if (checksumParts.length != 2) {
       throw new IllegalArgumentException("Invalid string for checksum!");
     }
 
     String value = checksumParts[0];
     String type = checksumParts[1].replace("(","").replace(")", "");
 
     return create(type, value);
   }
 
   /**
    * Creates a checksum of type <code>type</code> and value <code>value</code>.
    *
    * @param type
    *          the checksum type name
    * @param value
    *          the checksum value
    * @return the checksum
    * @throws NoSuchAlgorithmException
    *           if the checksum of the specified type cannot be created
    */
   public static Checksum create(String type, String value) throws NoSuchAlgorithmException {
     ChecksumType t = ChecksumType.fromString(type);
     return new Checksum(value, t);
   }
 
   /**
    * Creates a checksum of type <code>type</code> and value <code>value</code>.
    *
    * @param type
    *          the checksum type
    * @param value
    *          the checksum value
    * @return the checksum
    */
   public static Checksum create(ChecksumType type, String value) {
     return new Checksum(value, type);
   }
 
   /**
    * Creates a checksum of type <code>type</code> from the given file.
    *
    * @param type
    *          the checksum type
    * @param file
    *          the file
    * @return the checksum
    * @throws IOException
    *           if the file cannot be accessed
    */
   public static Checksum create(ChecksumType type, File file) throws IOException {
     return create(type, new BufferedInputStream(new FileInputStream(file)));
   }
 
   /**
    * Creates a checksum of type <code>type</code> from the given input stream.
    * The stream gets closed afterwards.
    */
   public static Checksum create(ChecksumType type, InputStream is) throws IOException {
     MessageDigest checksum;
     try {
       checksum = MessageDigest.getInstance(type.getName());
     } catch (NoSuchAlgorithmException e) {
       throw new IllegalStateException("This system does not support checksums of type " + type.getName());
     }
     try {
       byte[] bytes = new byte[1024];
       int len = 0;
       while ((len = is.read(bytes)) >= 0) {
         checksum.update(bytes, 0, len);
       }
     } finally {
       IoSupport.closeQuietly(is);
     }
     return new Checksum(convertToHex(checksum.digest()), type);
   }
 
 }