/*
    * 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
    *
   *   https://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.commons.compress.archivers.zip;
  
  import java.util.zip.ZipException;
  
  /**
   * An extra field who's sole purpose is to align and pad the local file header so that the entry's data starts at a certain position.
   *
   * <p>
   * The padding content of the padding is ignored and not retained when reading a padding field.
   * </p>
   *
   * <p>
   * This enables Commons Compress to create "aligned" archives similar to Android's {@code zipalign} command line tool.
   * </p>
   *
   * @since 1.14
   * @see "https://developer.android.com/studio/command-line/zipalign.html"
   * @see ZipArchiveEntry#setAlignment
   */
  public class ResourceAlignmentExtraField implements ZipExtraField {
  
      private static final int MAX_ALIGNMENT = Short.MAX_VALUE;
  
      /**
       * Extra field id used for storing alignment and padding.
       */
      public static final ZipShort ID = new ZipShort(0xa11e);
  
      /**
       * Base field size.
       */
      public static final int BASE_SIZE = 2;
  
      private static final int ALLOW_METHOD_MESSAGE_CHANGE_FLAG = 0x8000;
  
      private short alignment;
  
      private boolean allowMethodChange;
  
      private int padding;
  
      /**
       * Constructs a new instance.
       */
      public ResourceAlignmentExtraField() {
      }
  
      /**
       * Constructs a new instance.
       *
       * @param alignment A positive alignment less than {@link Short#MAX_VALUE}.
       */
      public ResourceAlignmentExtraField(final int alignment) {
          this(alignment, false);
      }
  
      /**
       * Constructs a new instance.
       *
       * @param alignment A positive alignment less than {@link Short#MAX_VALUE}.
       * @param allowMethodChange whether a method change is allowed when re-compressing the ZIP file.
       */
      public ResourceAlignmentExtraField(final int alignment, final boolean allowMethodChange) {
          this(alignment, allowMethodChange, 0);
      }
  
      /**
       * Constructs a new instance.
       *
       * @param alignment A positive alignment less than {@link Short#MAX_VALUE}.
       * @param allowMethodChange whether a method change is allowed when re-compressing the ZIP file.
       * @param padding padding.
       */
      public ResourceAlignmentExtraField(final int alignment, final boolean allowMethodChange, final int padding) {
          if (alignment < 0 || alignment > MAX_ALIGNMENT) {
              throw new IllegalArgumentException("Alignment must be between 0 and 0x7fff, was: " + alignment);
          }
          if (padding < 0) {
              throw new IllegalArgumentException("Padding must not be negative, was: " + padding);
          }
          this.alignment = (short) alignment;
         this.allowMethodChange = allowMethodChange;
         this.padding = padding;
     }
 
     /**
      * Indicates whether a method change is allowed when re-compressing the ZIP file.
      *
      * @return true if a method change is allowed, false otherwise.
      */
     public boolean allowMethodChange() {
         return allowMethodChange;
     }
 
     /**
      * Gets requested alignment.
      *
      * @return requested alignment.
      */
     public short getAlignment() {
         return alignment;
     }
 
     @Override
     public byte[] getCentralDirectoryData() {
         return ZipShort.getBytes(alignment | (allowMethodChange ? ALLOW_METHOD_MESSAGE_CHANGE_FLAG : 0));
     }
 
     @Override
     public ZipShort getCentralDirectoryLength() {
         return new ZipShort(BASE_SIZE);
     }
 
     @Override
     public ZipShort getHeaderId() {
         return ID;
     }
 
     @Override
     public byte[] getLocalFileDataData() {
         final byte[] content = new byte[BASE_SIZE + padding];
         ZipShort.putShort(alignment | (allowMethodChange ? ALLOW_METHOD_MESSAGE_CHANGE_FLAG : 0), content, 0);
         return content;
     }
 
     @Override
     public ZipShort getLocalFileDataLength() {
         return new ZipShort(BASE_SIZE + padding);
     }
 
     @Override
     public void parseFromCentralDirectoryData(final byte[] buffer, final int offset, final int length) throws ZipException {
         if (length < BASE_SIZE) {
             throw new ZipException("Too short content for ResourceAlignmentExtraField (0xa11e): " + length);
         }
         final int alignmentValue = ZipShort.getValue(buffer, offset);
         this.alignment = (short) (alignmentValue & ALLOW_METHOD_MESSAGE_CHANGE_FLAG - 1);
         this.allowMethodChange = (alignmentValue & ALLOW_METHOD_MESSAGE_CHANGE_FLAG) != 0;
     }
 
     @Override
     public void parseFromLocalFileData(final byte[] buffer, final int offset, final int length) throws ZipException {
         parseFromCentralDirectoryData(buffer, offset, length);
         this.padding = length - BASE_SIZE;
     }
 }