/*
 * ====================================================================
 * 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.http.impl.nio.codecs;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.WritableByteChannel;

import org.apache.http.impl.io.HttpTransportMetricsImpl;
import org.apache.http.nio.FileContentEncoder;
import org.apache.http.nio.reactor.SessionOutputBuffer;

Content encoder that writes data without any transformation. The end of
the content entity is demarcated by closing the underlying connection
(EOF condition). Entities transferred using this input stream can be of
unlimited length.
 This decoder is optimized to transfer data directly from a FileChannel to the underlying I/O session's channel whenever possible avoiding intermediate buffering in the session buffer. 
Since:
4.0/**
 * Content encoder that writes data without any transformation. The end of
 * the content entity is demarcated by closing the underlying connection
 * (EOF condition). Entities transferred using this input stream can be of
 * unlimited length.
 * <p>
 * This decoder is optimized to transfer data directly from
 * a {@link FileChannel} to the underlying I/O session's channel whenever
 * possible avoiding intermediate buffering in the session buffer.
 *
 * @since 4.0
 */
public class IdentityEncoder extends AbstractContentEncoder
        implements FileContentEncoder {

    private final int fragHint;

    
Params:
channel – underlying channel.
buffer –  session buffer.
metrics – transport metrics.
fragementSizeHint – fragment size hint defining an minimal size of a fragment that should be written out directly to the channel bypassing the session buffer. Value 0 disables fragment buffering.
Since:
4.3/**
     * @since 4.3
     *
     * @param channel underlying channel.
     * @param buffer  session buffer.
     * @param metrics transport metrics.
     * @param fragementSizeHint fragment size hint defining an minimal size of a fragment
     *   that should be written out directly to the channel bypassing the session buffer.
     *   Value {@code 0} disables fragment buffering.
     */
    public IdentityEncoder(
            final WritableByteChannel channel,
            final SessionOutputBuffer buffer,
            final HttpTransportMetricsImpl metrics,
            final int fragementSizeHint) {
        super(channel, buffer, metrics);
        this.fragHint = fragementSizeHint > 0 ? fragementSizeHint : 0;
    }

    public IdentityEncoder(
            final WritableByteChannel channel,
            final SessionOutputBuffer buffer,
            final HttpTransportMetricsImpl metrics) {
        this(channel, buffer, metrics, 0);
    }

    @Override
    public int write(final ByteBuffer src) throws IOException {
        if (src == null) {
            return 0;
        }
        assertNotCompleted();

        int total = 0;
        while (src.hasRemaining()) {
            if (this.buffer.hasData() || this.fragHint > 0) {
                if (src.remaining() <= this.fragHint) {
                    final int capacity = this.fragHint - this.buffer.length();
                    if (capacity > 0) {
                        final int limit = Math.min(capacity, src.remaining());
                        final int bytesWritten = writeToBuffer(src, limit);
                        total += bytesWritten;
                    }
                }
            }
            if (this.buffer.hasData()) {
                if (this.buffer.length() >= this.fragHint || src.hasRemaining()) {
                    final int bytesWritten = flushToChannel();
                    if (bytesWritten == 0) {
                        break;
                    }
                }
            }
            if (!this.buffer.hasData() && src.remaining() > this.fragHint) {
                final int bytesWritten = writeToChannel(src);
                total += bytesWritten;
                if (bytesWritten == 0) {
                    break;
                }
            }
        }
        return total;
    }

    @Override
    public long transfer(
            final FileChannel src,
            final long position,
            final long count) throws IOException {

        if (src == null) {
            return 0;
        }
        assertNotCompleted();

        flushToChannel();
        if (this.buffer.hasData()) {
            return 0;
        }

        final long bytesWritten = src.transferTo(position, count, this.channel);
        if (bytesWritten > 0) {
            this.metrics.incrementBytesTransferred(bytesWritten);
        }
        return bytesWritten;
    }

    @Override
    public String toString() {
        final StringBuilder sb = new StringBuilder();
        sb.append("[identity; completed: ");
        sb.append(isCompleted());
        sb.append("]");
        return sb.toString();
    }

}