/*
 * ====================================================================
 * 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 ch.boye.httpclientandroidlib.impl.io;

import java.io.IOException;
import java.io.OutputStream;

import ch.boye.httpclientandroidlib.annotation.NotThreadSafe;
import ch.boye.httpclientandroidlib.io.SessionOutputBuffer;

/**
 * Output stream that cuts off after a defined number of bytes. This class
 * is used to send content of HTTP messages where the end of the content entity
 * is determined by the value of the <code>Content-Length header</code>.
 * Entities transferred using this stream can be maximum {@link Long#MAX_VALUE}
 * long.
 * <p>
 * Note that this class NEVER closes the underlying stream, even when close
 * gets called.  Instead, the stream will be marked as closed and no further
 * output will be permitted.
 *
 * @since 4.0
 */
@NotThreadSafe
public class ContentLengthOutputStream extends OutputStream {

    /**
     * Wrapped session output buffer.
     */
    private final SessionOutputBuffer out;

    /**
     * The maximum number of bytes that can be written the stream. Subsequent
     * write operations will be ignored.
     */
    private final long contentLength;

    /** Total bytes written */
    private long total = 0;

    /** True if the stream is closed. */
    private boolean closed = false;

    /**
     * Wraps a session output buffer and cuts off output after a defined number
     * of bytes.
     *
     * @param out The session output buffer
     * @param contentLength The maximum number of bytes that can be written to
     * the stream. Subsequent write operations will be ignored.
     *
     * @since 4.0
     */
    public ContentLengthOutputStream(final SessionOutputBuffer out, long contentLength) {
        super();
        if (out == null) {
            throw new IllegalArgumentException("Session output buffer may not be null");
        }
        if (contentLength < 0) {
            throw new IllegalArgumentException("Content length may not be negative");
        }
        this.out = out;
        this.contentLength = contentLength;
    }

    /**
     * <p>Does not close the underlying socket output.</p>
     *
     * @throws IOException If an I/O problem occurs.
     */
    @Override
    public void close() throws IOException {
        if (!this.closed) {
            this.closed = true;
            this.out.flush();
        }
    }

    @Override
    public void flush() throws IOException {
        this.out.flush();
    }

    @Override
    public void write(byte[] b, int off, int len) throws IOException {
        if (this.closed) {
            throw new IOException("Attempted write to closed stream.");
        }
        if (this.total < this.contentLength) {
            long max = this.contentLength - this.total;
            if (len > max) {
                len = (int) max;
            }
            this.out.write(b, off, len);
            this.total += len;
        }
    }

    @Override
    public void write(byte[] b) throws IOException {
        write(b, 0, b.length);
    }

    @Override
    public void write(int b) throws IOException {
        if (this.closed) {
            throw new IOException("Attempted write to closed stream.");
        }
        if (this.total < this.contentLength) {
            this.out.write(b);
            this.total++;
        }
    }

}
