/*
    * ====================================================================
    * 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.io.InputStream;
  import java.io.RandomAccessFile;
  import java.nio.channels.FileChannel;
  
  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.util.Args;
  
  /**
   * 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;
      private final BasicIdGenerator idgen;
  
      public FileResourceFactory(final File cacheDir) {
          super();
          this.cacheDir = cacheDir;
          this.idgen = new BasicIdGenerator();
      }
  
      private File generateUniqueCacheFile(final String requestId) {
          final StringBuilder buffer = new StringBuilder();
          this.idgen.generate(buffer);
          buffer.append('.');
          final int len = Math.min(requestId.length(), 100);
          for (int i = 0; i < len; i++) {
              final char ch = requestId.charAt(i);
              if (Character.isLetterOrDigit(ch) || ch == '.') {
                  buffer.append(ch);
              } else {
                  buffer.append('-');
              }
          }
          return new File(this.cacheDir, buffer.toString());
      }
  
      @Override
      public Resource generate(
              final String requestId,
              final byte[] content, final int off, final int len) throws ResourceIOException {
          Args.notNull(requestId, "Request id");
          final File file = generateUniqueCacheFile(requestId);
          try (FileOutputStream outStream = new FileOutputStream(file)) {
              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) throws ResourceIOException {
          Args.notNull(content, "Content");
          return generate(requestId, content, 0, content.length);
      }
  
      @Override
      public Resource copy(
             final String requestId,
             final Resource resource) throws ResourceIOException {
         final File file = generateUniqueCacheFile(requestId);
         try {
             if (resource instanceof FileResource) {
                 try (final RandomAccessFile srcFile = new RandomAccessFile(((FileResource) resource).getFile(), "r");
                      final RandomAccessFile dstFile = new RandomAccessFile(file, "rw");
                      final FileChannel src = srcFile.getChannel();
                      final FileChannel dst = dstFile.getChannel()) {
                     src.transferTo(0, srcFile.length(), dst);
                 }
             } else {
                 try (final FileOutputStream out = new FileOutputStream(file);
                      final InputStream in = resource.getInputStream()) {
                     final byte[] buf = new byte[2048];
                     int len;
                     while ((len = in.read(buf)) != -1) {
                         out.write(buf, 0, len);
                     }
                 }
             }
         } catch (final IOException ex) {
             throw new ResourceIOException(ex.getMessage(), ex);
         }
         return new FileResource(file);
     }
 
 }