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/**
 * Copyright 2005-2008 Noelios Technologies.
 * 
 * The contents of this file are subject to the terms of the following open
 * source licenses: LGPL 3.0 or LGPL 2.1 or CDDL 1.0 (the "Licenses"). You can
 * select the license that you prefer but you may not use this file except in
 * compliance with one of these Licenses.
 * 
 * You can obtain a copy of the LGPL 3.0 license at
 * http://www.gnu.org/licenses/lgpl-3.0.html
 * 
 * You can obtain a copy of the LGPL 2.1 license at
 * http://www.gnu.org/licenses/lgpl-2.1.html
 * 
 * You can obtain a copy of the CDDL 1.0 license at
 * http://www.sun.com/cddl/cddl.html
 * 
 * See the Licenses for the specific language governing permissions and
 * limitations under the Licenses.
 * 
 * Alternatively, you can obtain a royaltee free commercial license with less
 * limitations, transferable or non-transferable, directly at
 * http://www.noelios.com/products/restlet-engine
 * 
 * Restlet is a registered trademark of Noelios Technologies.
 */

package com.noelios.restlet.application;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.channels.ReadableByteChannel;
import java.nio.channels.WritableByteChannel;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import java.util.zip.GZIPInputStream;
import java.util.zip.InflaterInputStream;
import java.util.zip.ZipInputStream;

import org.restlet.data.Encoding;
import org.restlet.resource.Representation;
import org.restlet.util.ByteUtils;
import org.restlet.util.WrapperRepresentation;

/**
 * Representation that decodes a wrapped representation if its encoding is
 * supported. If at least one encoding of the wrapped representation is not
 * supported, then the wrapped representation is not decoded.
 * 
 * @author Jerome Louvel
 */
public class DecodeRepresentation extends WrapperRepresentation {
    /**
     * Returns the list of supported encodings.
     * 
     * @return The list of supported encodings.
     */
    public static List getSupportedEncodings() {
        return Arrays. asList(Encoding.GZIP, Encoding.DEFLATE,
                Encoding.ZIP, Encoding.IDENTITY);
    }

    /** Indicates if the decoding can happen. */
    private volatile boolean canDecode;

    /** List of encodings still applied to the decodeRepresentation */
    private volatile List wrappedEncodings;

    /**
     * Constructor.
     * 
     * @param wrappedRepresentation
     *            The wrapped representation.
     */
    public DecodeRepresentation(Representation wrappedRepresentation) {
        super(wrappedRepresentation);
        this.canDecode = getSupportedEncodings().containsAll(
                wrappedRepresentation.getEncodings());
        this.wrappedEncodings = new ArrayList();
        this.wrappedEncodings.addAll(wrappedRepresentation.getEncodings());
    }

    /**
     * Indicates if the decoding can happen.
     * 
     * @return True if the decoding can happen.
     */
    public boolean canDecode() {
        return this.canDecode;
    }

    /**
     * Returns a readable byte channel. If it is supported by a file a read-only
     * instance of FileChannel is returned.
     * 
     * @return A readable byte channel.
     */
    @Override
    public ReadableByteChannel getChannel() throws IOException {
        if (canDecode()) {
            return ByteUtils.getChannel(getStream());
        }

        return getWrappedRepresentation().getChannel();
    }

    /**
     * Returns a decoded stream for a given encoding and coded stream.
     * 
     * @param encoding
     *            The encoding to use.
     * @param encodedStream
     *            The encoded stream.
     * @return The decoded stream.
     * @throws IOException
     */
    private InputStream getDecodedStream(Encoding encoding,
            InputStream encodedStream) throws IOException {
        InputStream result = null;

        if (encodedStream != null) {
            if (encoding.equals(Encoding.GZIP)) {
                result = new GZIPInputStream(encodedStream);
            } else if (encoding.equals(Encoding.DEFLATE)) {
                result = new InflaterInputStream(encodedStream);
            } else if (encoding.equals(Encoding.ZIP)) {
                final ZipInputStream stream = new ZipInputStream(encodedStream);
                if (stream.getNextEntry() != null) {
                    result = stream;
                }
            } else if (encoding.equals(Encoding.IDENTITY)) {
                throw new IOException(
                        "Decoder unecessary for identity decoding");
            }
        }

        return result;
    }

    /**
     * Returns the encodings applied to the entity.
     * 
     * @return The encodings applied to the entity.
     */
    @Override
    public List getEncodings() {
        if (canDecode()) {
            return new ArrayList();
        }

        return this.wrappedEncodings;
    }

    /**
     * Returns the size in bytes of the decoded representation if known,
     * UNKNOWN_SIZE (-1) otherwise.
     * 
     * @return The size in bytes if known, UNKNOWN_SIZE (-1) otherwise.
     */
    @Override
    public long getSize() {
        long result = UNKNOWN_SIZE;

        if (canDecode()) {
            boolean identity = true;
            for (final Iterator iter = getEncodings().iterator(); identity
                    && iter.hasNext();) {
                identity = (iter.next().equals(Encoding.IDENTITY));
            }
            if (identity) {
                result = getWrappedRepresentation().getSize();
            }
        } else {
            result = getWrappedRepresentation().getSize();
        }

        return result;
    }

    /**
     * Returns a stream with the representation's content.
     * 
     * @return A stream with the representation's content.
     */
    @Override
    public InputStream getStream() throws IOException {
        InputStream result = null;

        if (canDecode()) {
            result = getWrappedRepresentation().getStream();
            for (int i = this.wrappedEncodings.size() - 1; i >= 0; i--) {
                if (!this.wrappedEncodings.get(i).equals(Encoding.IDENTITY)) {
                    result = getDecodedStream(this.wrappedEncodings.get(i),
                            result);
                }
            }
        }

        return result;
    }

    /**
     * Converts the representation to a string value. Be careful when using this
     * method as the conversion of large content to a string fully stored in
     * memory can result in OutOfMemoryErrors being thrown.
     * 
     * @return The representation as a string value.
     */
    @Override
    public String getText() throws IOException {
        String result = null;

        if (canDecode()) {
            result = ByteUtils.toString(getStream(), getCharacterSet());
        } else {
            result = getWrappedRepresentation().getText();
        }

        return result;
    }

    /**
     * Writes the representation to a byte stream.
     * 
     * @param outputStream
     *            The output stream.
     */
    @Override
    public void write(OutputStream outputStream) throws IOException {
        if (canDecode()) {
            ByteUtils.write(getStream(), outputStream);
        } else {
            getWrappedRepresentation().write(outputStream);
        }
    }

    /**
     * Writes the representation to a byte channel.
     * 
     * @param writableChannel
     *            A writable byte channel.
     */
    @Override
    public void write(WritableByteChannel writableChannel) throws IOException {
        if (canDecode()) {
            write(ByteUtils.getStream(writableChannel));
        } else {
            getWrappedRepresentation().write(writableChannel);
        }
    }
}