/*
    * ====================================================================
    * 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.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  package org.apache.hc.client5.http.impl.cache;
  
  import java.io.File;
  import java.io.FileOutputStream;
  import java.io.IOException;
  import java.security.MessageDigest;
  import java.security.NoSuchAlgorithmException;
  
  import org.apache.hc.client5.http.cache.Resource;
  import org.apache.hc.client5.http.cache.ResourceFactory;
  import org.apache.hc.client5.http.cache.ResourceIOException;
  import org.apache.hc.core5.annotation.Contract;
  import org.apache.hc.core5.annotation.ThreadingBehavior;
  import org.apache.hc.core5.net.PercentCodec;
  import org.apache.hc.core5.util.Args;
  import org.apache.hc.core5.util.TextUtils;
  
  /**
   * Generates {@link Resource} instances whose body is stored in a temporary file.
   *
   * @since 4.1
   */
  @Contract(threading = ThreadingBehavior.STATELESS)
  public class FileResourceFactory implements ResourceFactory {
  
      private final File cacheDir;
  
      public FileResourceFactory(final File cacheDir) {
          super();
          this.cacheDir = cacheDir;
      }
  
      static String generateUniqueCacheFileName(final String requestId, final String eTag, final byte[] content, final int off, final int len) {
          final StringBuilder buf = new StringBuilder();
          if (eTag != null) {
              PercentCodec.RFC3986.encode(buf, eTag);
              buf.append('@');
          } else if (content != null) {
              final MessageDigest sha256;
              try {
                  sha256 = MessageDigest.getInstance("SHA-256");
              } catch (final NoSuchAlgorithmException ex) {
                  throw new IllegalStateException(ex);
              }
              sha256.update(content, off, len);
              buf.append(TextUtils.toHexString(sha256.digest()));
              buf.append('@');
          }
          PercentCodec.RFC3986.encode(buf, requestId);
          return buf.toString();
      }
  
      /**
       * @since 5.4
       */
      @Override
      public Resource generate(
              final String requestId,
              final String eTag,
              final byte[] content, final int off, final int len) throws ResourceIOException {
          Args.notNull(requestId, "Request id");
          final String filename = generateUniqueCacheFileName(requestId, eTag, content, off, len);
          final File file = new File(cacheDir, filename);
          try (FileOutputStream outStream = new FileOutputStream(file, false)) {
              if (content != null) {
                  outStream.write(content, off, len);
              }
          } catch (final IOException ex) {
              throw new ResourceIOException(ex.getMessage(), ex);
          }
          return new FileResource(file);
      }
  
     @Override
     public Resource generate(final String requestId, final byte[] content, final int off, final int len) throws ResourceIOException {
         if (content != null) {
             return generate(requestId, null, content, off, len);
         }
         return generate(requestId, null, null, 0, 0);
     }
 
     @Override
     public Resource generate(final String requestId, final byte[] content) throws ResourceIOException {
         if (content != null) {
             return generate(requestId, null, content, 0, content.length);
         }
         return generate(requestId, null, null, 0, 0);
     }
 
     /**
      * @deprecated Do not use.
      */
     @Deprecated
     @Override
     public Resource copy(
             final String requestId,
             final Resource resource) throws ResourceIOException {
         return resource;
     }
 
 }