/*
 * $HeadURL: http://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk/module-main/src/main/java/org/apache/http/impl/io/AbstractSessionInputBuffer.java $
 * $Revision: 576077 $
 * $Date: 2007-09-16 04:50:22 -0700 (Sun, 16 Sep 2007) $
 *
 * ====================================================================
 * 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.io;

import java.io.IOException;
import java.io.InputStream;

import org.apache.http.io.SessionInputBuffer;
import org.apache.http.io.HttpTransportMetrics;
import org.apache.http.params.CoreConnectionPNames;
import org.apache.http.params.HttpParams;
import org.apache.http.params.HttpProtocolParams;
import org.apache.http.protocol.HTTP;
import org.apache.http.util.ByteArrayBuffer;
import org.apache.http.util.CharArrayBuffer;

/**
 * Abstract base class for session input buffers that stream data 
 * from a {@link InputStream}.
 *
 * @author <a href="mailto:oleg at ural.ru">Oleg Kalnichevski</a>
 *
 */
public abstract class AbstractSessionInputBuffer implements SessionInputBuffer {

    private InputStream instream;
    private byte[] buffer;
    private int bufferpos;
    private int bufferlen;
    
    private ByteArrayBuffer linebuffer = null;
    
    private String charset = HTTP.US_ASCII;
    private boolean ascii = true;
    private int maxLineLen = -1;
    
    private HttpTransportMetricsImpl metrics;
    
    protected void init(final InputStream instream, int buffersize, final HttpParams params) {
        if (instream == null) {
            throw new IllegalArgumentException("Input stream may not be null");
        }
        if (buffersize <= 0) {
            throw new IllegalArgumentException("Buffer size may not be negative or zero");
        }
        if (params == null) {
            throw new IllegalArgumentException("HTTP parameters may not be null");
        }
        this.instream = instream;
        this.buffer = new byte[buffersize];
        this.bufferpos = 0;
        this.bufferlen = 0;
        this.linebuffer = new ByteArrayBuffer(buffersize);
        this.charset = HttpProtocolParams.getHttpElementCharset(params);
        this.ascii = this.charset.equalsIgnoreCase(HTTP.US_ASCII)
                     || this.charset.equalsIgnoreCase(HTTP.ASCII);
        this.maxLineLen = params.getIntParameter(CoreConnectionPNames.MAX_LINE_LENGTH, -1);
        this.metrics = new HttpTransportMetricsImpl();
    }
    
    protected int fillBuffer() throws IOException {
        // compact the buffer if necessary
        if (this.bufferpos > 0) {
            int len = this.bufferlen - this.bufferpos;
            if (len > 0) {
                System.arraycopy(this.buffer, this.bufferpos, this.buffer, 0, len);
            }
            this.bufferpos = 0;
            this.bufferlen = len;
        }
        int l;
        int off = this.bufferlen;
        int len = this.buffer.length - off;
        l = this.instream.read(this.buffer, off, len);
        if (l == -1) {
            return -1;
        } else {
            this.bufferlen = off + l;
            this.metrics.incrementBytesTransferred(l);
            return l;
        }
    }

    protected boolean hasBufferedData() {
        return this.bufferpos < this.bufferlen;
    }
    
    public int read() throws IOException {
        int noRead = 0;
        while (!hasBufferedData()) {
            noRead = fillBuffer();
            if (noRead == -1) {
                return -1;
            }
        }
        return this.buffer[this.bufferpos++] & 0xff;
    }
    
    public int read(final byte[] b, int off, int len) throws IOException {
        if (b == null) {
            return 0;
        }
        int noRead = 0;
        while (!hasBufferedData()) {
            noRead = fillBuffer();
            if (noRead == -1) {
                return -1;
            }
        }
        int chunk = this.bufferlen - this.bufferpos;
        if (chunk > len) {
            chunk = len;
        }
        System.arraycopy(this.buffer, this.bufferpos, b, off, chunk);
        this.bufferpos += chunk;
        return chunk;
    }
    
    public int read(final byte[] b) throws IOException {
        if (b == null) {
            return 0;
        }
        return read(b, 0, b.length);
    }
    
    private int locateLF() {
        for (int i = this.bufferpos; i < this.bufferlen; i++) {
            if (this.buffer[i] == HTTP.LF) {
                return i;
            }
        }
        return -1;
    }
    
    public int readLine(final CharArrayBuffer charbuffer) throws IOException {
        if (charbuffer == null) {
            throw new IllegalArgumentException("Char array buffer may not be null");
        }
        this.linebuffer.clear();
        int noRead = 0;
        boolean retry = true;
        while (retry) {
            // attempt to find end of line (LF)
            int i = locateLF();
            if (i != -1) {
                // end of line found. 
                if (this.linebuffer.isEmpty()) {
                    // the entire line is preset in the read buffer
                    return lineFromReadBuffer(charbuffer, i);
                }
                retry = false;
                int len = i + 1 - this.bufferpos;
                this.linebuffer.append(this.buffer, this.bufferpos, len);
                this.bufferpos = i + 1;
            } else {
                // end of line not found
                if (hasBufferedData()) {
                    int len = this.bufferlen - this.bufferpos;
                    this.linebuffer.append(this.buffer, this.bufferpos, len);
                    this.bufferpos = this.bufferlen;
                }
                noRead = fillBuffer();
                if (noRead == -1) {
                    retry = false;
                }
            }
            if (this.maxLineLen > 0 && this.linebuffer.length() >= this.maxLineLen) {
                throw new IOException("Maximum line length limit exceeded");
            }
        }
        if (noRead == -1 && this.linebuffer.isEmpty()) {
            // indicate the end of stream
            return -1;
        }
        return lineFromLineBuffer(charbuffer);
    }
    
    private int lineFromLineBuffer(final CharArrayBuffer charbuffer) 
            throws IOException {
        // discard LF if found
        int l = this.linebuffer.length(); 
        if (l > 0) {
            if (this.linebuffer.byteAt(l - 1) == HTTP.LF) {
                l--;
                this.linebuffer.setLength(l);
            }
            // discard CR if found
            if (l > 0) {
                if (this.linebuffer.byteAt(l - 1) == HTTP.CR) {
                    l--;
                    this.linebuffer.setLength(l);
                }
            }
        }
        l = this.linebuffer.length(); 
        if (this.ascii) {
            charbuffer.append(this.linebuffer, 0, l);
        } else {
            // This is VERY memory inefficient, BUT since non-ASCII charsets are 
            // NOT meant to be used anyway, there's no point optimizing it
            String s = new String(this.linebuffer.buffer(), 0, l, this.charset);
            charbuffer.append(s);
        }
        return l;
    }
    
    private int lineFromReadBuffer(final CharArrayBuffer charbuffer, int pos) 
            throws IOException {
        int off = this.bufferpos;
        int len;
        this.bufferpos = pos + 1;
        // BEGIN android-changed
        // The first test below was fixed to not try to skip beyond the
        // start of the live part of the buffer.
        if (pos > off && this.buffer[pos - 1] == HTTP.CR) {
            // skip CR if found
            pos--;
        }
        // END android-changed
        len = pos - off;
        if (this.ascii) {
            charbuffer.append(this.buffer, off, len);
        } else {
            // This is VERY memory inefficient, BUT since non-ASCII charsets are 
            // NOT meant to be used anyway, there's no point optimizing it
            String s = new String(this.buffer, off, len, this.charset);
            charbuffer.append(s);
        }
        return len;
    }
    
    public String readLine() throws IOException {
        CharArrayBuffer charbuffer = new CharArrayBuffer(64);
        int l = readLine(charbuffer);
        if (l != -1) {
            return charbuffer.toString();
        } else {
            return null;
        }
    }
    
    public HttpTransportMetrics getMetrics() {
        return this.metrics;
    }
    
}