/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project 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.
 */
package io.netty.handler.stream;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufAllocator;
import io.netty.channel.ChannelHandlerContext;

import java.io.InputStream;
import java.io.PushbackInputStream;

A ChunkedInput that fetches data from an InputStream chunk by chunk. 
 Please note that the InputStream instance that feeds data into ChunkedStream must implement InputStream.available() as accurately as possible, rather than using the default implementation. Otherwise, ChunkedStream will generate many too small chunks or block unnecessarily often. /**
 * A {@link ChunkedInput} that fetches data from an {@link InputStream} chunk by
 * chunk.
 * <p>
 * Please note that the {@link InputStream} instance that feeds data into
 * {@link ChunkedStream} must implement {@link InputStream#available()} as
 * accurately as possible, rather than using the default implementation.
 * Otherwise, {@link ChunkedStream} will generate many too small chunks or
 * block unnecessarily often.
 */
public class ChunkedStream implements ChunkedInput<ByteBuf> {

    static final int DEFAULT_CHUNK_SIZE = 8192;

    private final PushbackInputStream in;
    private final int chunkSize;
    private long offset;
    private boolean closed;

    
Creates a new instance that fetches data from the specified stream.
/**
     * Creates a new instance that fetches data from the specified stream.
     */
    public ChunkedStream(InputStream in) {
        this(in, DEFAULT_CHUNK_SIZE);
    }

    
Creates a new instance that fetches data from the specified stream.
Params:
chunkSize – the number of bytes to fetch on each readChunk(ChannelHandlerContext) call/**
     * Creates a new instance that fetches data from the specified stream.
     *
     * @param chunkSize the number of bytes to fetch on each
     *                  {@link #readChunk(ChannelHandlerContext)} call
     */
    public ChunkedStream(InputStream in, int chunkSize) {
        if (in == null) {
            throw new NullPointerException("in");
        }
        if (chunkSize <= 0) {
            throw new IllegalArgumentException(
                    "chunkSize: " + chunkSize +
                    " (expected: a positive integer)");
        }

        if (in instanceof PushbackInputStream) {
            this.in = (PushbackInputStream) in;
        } else {
            this.in = new PushbackInputStream(in);
        }
        this.chunkSize = chunkSize;
    }

    
Returns the number of transferred bytes.
/**
     * Returns the number of transferred bytes.
     */
    public long transferredBytes() {
        return offset;
    }

    @Override
    public boolean isEndOfInput() throws Exception {
        if (closed) {
            return true;
        }

        int b = in.read();
        if (b < 0) {
            return true;
        } else {
            in.unread(b);
            return false;
        }
    }

    @Override
    public void close() throws Exception {
        closed = true;
        in.close();
    }

    @Deprecated
    @Override
    public ByteBuf readChunk(ChannelHandlerContext ctx) throws Exception {
        return readChunk(ctx.alloc());
    }

    @Override
    public ByteBuf readChunk(ByteBufAllocator allocator) throws Exception {
        if (isEndOfInput()) {
            return null;
        }

        final int availableBytes = in.available();
        final int chunkSize;
        if (availableBytes <= 0) {
            chunkSize = this.chunkSize;
        } else {
            chunkSize = Math.min(this.chunkSize, in.available());
        }

        boolean release = true;
        ByteBuf buffer = allocator.buffer(chunkSize);
        try {
            // transfer to buffer
            offset += buffer.writeBytes(in, chunkSize);
            release = false;
            return buffer;
        } finally {
            if (release) {
                buffer.release();
            }
        }
    }

    @Override
    public long length() {
        return -1;
    }

    @Override
    public long progress() {
        return offset;
    }
}