/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  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.  For additional information regarding
 * copyright in this work, please see the NOTICE file in the top level
 * directory of this distribution.
 */
package org.apache.abdera2.common.protocol;

import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.zip.DeflaterOutputStream;

import org.apache.abdera2.common.http.QualityHelper;
import org.apache.abdera2.common.http.QualityHelper.QToken;
import org.apache.abdera2.common.io.Compression;
import org.apache.abdera2.common.io.Compression.CompressionCodec;
import org.apache.abdera2.common.misc.Chain;
import org.apache.abdera2.common.misc.Task;

/**
 * Abdera Filter implementation that selectively applies compression to the response payload
 */
public class CompressionFilter implements Task<RequestContext,ResponseContext> {

    public ResponseContext apply(
      RequestContext request, 
      Chain<RequestContext,ResponseContext> chain) {
        QToken[] encodings = 
          request.getHeader(
            "Accept-Encoding", 
            QualityHelper.parser);
        for (QToken enc : encodings) {
          try {
              CompressionCodec codec = 
                CompressionCodec.valueOf(
                  enc.token().toUpperCase());
              return new CompressingResponseContextWrapper(
                chain.next(request), codec);
          } catch (Exception e) {}
        }
        return chain.next(request);
    }

    /**
     * A HttpServletResponseWrapper implementation that applies GZip or Deflate compression to response output.
     */
    public static class CompressingResponseContextWrapper 
      extends BaseResponseContextWrapper {
        private final CompressionCodec codec;
        public CompressingResponseContextWrapper(
          ResponseContext response, 
          CompressionCodec codec) {
            super(response);
            this.codec = codec;
        }
        private OutputStream wrap(OutputStream out) {
          return new CompressingOutputStream(codec, out);
        }
        public void writeTo(OutputStream out) throws IOException {
          super.writeTo(wrap(out));
          out.flush();
        }
    }

    public static class CompressingOutputStream 
      extends FilterOutputStream {
        public CompressingOutputStream(
          CompressionCodec codec, 
          OutputStream out) {
            super(initStream(codec, out));
        }
        public CompressingOutputStream(
          DeflaterOutputStream dout) {
            super(dout);
        }
        private static OutputStream initStream(
          CompressionCodec codec, 
          OutputStream out) {
            try {
                return Compression.wrap(out, new CompressionCodec[] {codec});
            } catch (Exception e) {
                return out;
            }
        }

    }

}