/**
    * Copyright (c) 2012-2017, s3auth.com
    * All rights reserved.
    *
    * Redistribution and use in source and binary forms, with or without
    * modification, are permitted provided that the following conditions
    * are met: 1) Redistributions of source code must retain the above
    * copyright notice, this list of conditions and the following
    * disclaimer. 2) Redistributions in binary form must reproduce the above
   * copyright notice, this list of conditions and the following
   * disclaimer in the documentation and/or other materials provided
   * with the distribution. 3) Neither the name of the s3auth.com nor
   * the names of its contributors may be used to endorse or promote
   * products derived from this software without specific prior written
   * permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT
   * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
   * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
   * THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
   * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
   * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
   * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
   * OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  package com.s3auth.hosts;
  
  import com.amazonaws.services.s3.AmazonS3;
  import com.amazonaws.services.s3.model.ListObjectsRequest;
  import com.amazonaws.services.s3.model.ObjectListing;
  import com.amazonaws.services.s3.model.S3ObjectSummary;
  import com.google.common.collect.ImmutableSet;
  import com.jcabi.aspects.Immutable;
  import com.jcabi.aspects.Loggable;
  import com.jcabi.xml.XMLDocument;
  import com.jcabi.xml.XSL;
  import com.jcabi.xml.XSLDocument;
  import java.io.IOException;
  import java.io.OutputStream;
  import java.net.HttpURLConnection;
  import java.util.Collection;
  import java.util.Date;
  import java.util.LinkedList;
  import java.util.zip.CRC32;
  import javax.validation.constraints.NotNull;
  import javax.ws.rs.core.HttpHeaders;
  import lombok.EqualsAndHashCode;
  import lombok.ToString;
  import org.apache.commons.io.Charsets;
  import org.xembly.Directives;
  import org.xembly.ImpossibleModificationException;
  import org.xembly.Xembler;
  
  /**
   * XML Directory Listing.
   * @author Carlos Miranda (miranda.cma@gmail.com)
   * @version $Id: f34411d24d8092c2c941571028c1c7c1acde27ad $
   * @checkstyle ClassDataAbstraction (200 lines)
   */
  @Immutable
  @ToString
  @EqualsAndHashCode(of = "content")
  @Loggable(Loggable.DEBUG)
  final class DirectoryListing implements Resource {
  
      /**
       * The STYLESHEET used for transforming the output.
       */
      private static final XSL STYLESHEET = XSLDocument.make(
          DirectoryListing.class.getResourceAsStream("directory.xsl")
      );
  
      /**
       * Byte representation of transformed data.
       */
      @Immutable.Array
      private final transient byte[] content;
  
      /**
       * Public constructor.
       * @param client Amazon S3 client
       * @param bucket Bucket name
       * @param key The S3 object key
       */
      DirectoryListing(@NotNull final AmazonS3 client,
          @NotNull final String bucket, @NotNull final String key) {
          ObjectListing listing = client.listObjects(
              new ListObjectsRequest().withDelimiter("/").withPrefix(key)
                  .withBucketName(bucket)
          );
          final Collection<S3ObjectSummary> objects =
              new LinkedList<S3ObjectSummary>();
          objects.addAll(listing.getObjectSummaries());
          while (listing.isTruncated()) {
              listing = client.listNextBatchOfObjects(listing);
             objects.addAll(listing.getObjectSummaries());
         }
         // @checkstyle LineLength (2 lines)
         final Directives dirs = new Directives()
             .add("directory").attr("prefix", key);
         for (final String prefix : listing.getCommonPrefixes()) {
             dirs.add("commonPrefix").set(prefix).up();
         }
         for (final S3ObjectSummary object : objects) {
             dirs.add("object")
                 .add("path")
                 .set(object.getKey()).up()
                 .add("size")
                 .set(Long.toString(object.getSize())).up()
                 .up();
         }
         try {
             this.content = DirectoryListing.STYLESHEET.transform(
                 new XMLDocument(new Xembler(dirs).xml())
             ).toString().getBytes(Charsets.UTF_8);
         } catch (final ImpossibleModificationException ex) {
             throw new IllegalStateException(
                 "Unable to generate directory listing", ex
             );
         }
     }
 
     @Override
     public int status() {
         return HttpURLConnection.HTTP_OK;
     }
 
     @Override
     public long writeTo(final OutputStream stream) throws IOException {
         stream.write(this.content);
         return (long) this.content.length;
     }
 
     @Override
     public Collection<String> headers() {
         final ImmutableSet.Builder<String> headers = ImmutableSet.builder();
         headers.add(
             DirectoryListing.header(
                 HttpHeaders.CONTENT_TYPE,
                 this.contentType()
             )
         );
         headers.add(
             DirectoryListing.header(
                 HttpHeaders.CONTENT_LENGTH,
                 String.valueOf(this.content.length)
             )
         );
         return headers.build();
     }
 
     @Override
     public String etag() {
         final CRC32 crc = new CRC32();
         crc.update(this.content);
         return Long.toHexString(crc.getValue());
     }
     @Override
     public Date lastModified() {
         return new Date();
     }
 
     @Override
     public String contentType() {
         return "text/html";
     }
 
     @Override
     public void close() {
         // nothing to do
     }
 
     /**
      * Create a HTTP header from name and value.
      * @param name Name of the header
      * @param value The value
      * @return Full HTTP header string
      */
     @NotNull
     private static String header(@NotNull final String name,
         @NotNull final String value) {
         return String.format("%s: %s", name, value);
     }
 }