/*
 * Copyright 2015 Red Hat, Inc. and/or its affiliates.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * 
 *      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.
*/

package org.eclipse.webdav.http.client;

import java.io.*;
import org.eclipse.webdav.IContext;
import org.eclipse.webdav.client.Policy;
import org.eclipse.webdav.client.WebDAVFactory;
import org.eclipse.webdav.internal.kernel.utils.Assert;

/**
 * A common superclass for HTTP messages.  There are two kinds of HTTP
 * message; requests and responses.  They both have in common a context
 * and an input stream.  This class factors out these similarities.
 * <p>
 * <b>Note:</b> This class/interface is part of an interim API that is still under 
 * development and expected to change significantly before reaching stability. 
 * It is being made available at this early stage to solicit feedback from pioneering 
 * adopters on the understanding that any code that uses this API will almost 
 * certainly be broken (repeatedly) as the API evolves.
 * </p>
 */
public abstract class Message {
    protected static BufferPool bufferPool = new BufferPool();
    protected InputStream is;
    protected boolean inputRead = false;
    protected boolean hasInputStream = false;
    protected IContext context;

    /**
     * Creates a message.
     *
     * @param context the message header, or <code>null</code> for an empty
     * header
     * @param is an input stream containing the message's body, or
     * <code>null</code> for an empty body
     */
    public Message(IContext context, InputStream is) {
        this.context = context;
        if (context == null)
            this.context = WebDAVFactory.contextFactory.newContext();
        this.is = is;
        if (is == null)
            this.is = new ByteArrayInputStream(new byte[0]);
    }

    /**
     * Closes this message to free up any system resources.  All messages
     * must be closed before finalization.
     *
     * @exception IOException if there is an I/O error
     */
    public void close() throws IOException {
        is.close();
    }

    /**
     * Returns the content length of this message's body, or -1 if the
     * content length is unknown.
     *
     * @return the content length of this message's body
     */
    public long getContentLength() {
        long contentLength = context.getContentLength();
        if (contentLength != -1)
            return contentLength;
        if (is instanceof ByteArrayInputStream)
            return ((ByteArrayInputStream) is).available();
        return -1;
    }

    /**
     * Returns this message's context.
     *
     * @return this message's context
     */
    public IContext getContext() {
        return context;
    }

    /**
     * Returns this message's input stream.
     *
     * @return this message's input stream
     */
    public InputStream getInputStream() {
        hasInputStream = true;
        return is;
    }

    public String toString() {
        return context.toString();
    }

    /**
     * Writes this messages body to the given output stream. This method may
     * only be called once during the lifetime of this message.
     *
     * @param os an output stream
     * @exception IOException if there is an I/O error
     */
    public void write(OutputStream os) throws IOException {
        Assert.isTrue(!inputRead);
        Assert.isTrue(!hasInputStream);

        int bytesRead = 0;
        int totalBytesRead = 0;
        byte[] buffer = bufferPool.getBuffer();
        long contentLength = getContentLength();

        try {
            while (bytesRead != -1 && (contentLength == -1 || contentLength > totalBytesRead)) {
                if (contentLength == -1) {
                    bytesRead = is.read(buffer);
                } else {
                    bytesRead = is.read(buffer, 0, (int) Math.min(buffer.length, contentLength - totalBytesRead));
                }
                if (bytesRead == -1) {
                    if (contentLength >= 0) {
                        throw new IOException(Policy.bind("exception.unexpectedEndStream")); //$NON-NLS-1$
                    }
                } else {
                    totalBytesRead += bytesRead;
                    os.write(buffer, 0, bytesRead);
                }
            }
        } finally {
            bufferPool.putBuffer(buffer);
            inputRead = true;
        }
    }
}
