/*
 * Hunt - A refined core library for D programming language.
 *
 * Copyright (C) 2018-2019 HuntLabs
 *
 * Website: https://www.huntlabs.net/
 *
 * Licensed under the Apache-2.0 License.
 *
 */

module hunt.io.FilterInputStream;

import hunt.io.Common;
import hunt.Exceptions;

version(HUNT_DEBUG) {
    import hunt.logging;
}

/**
 * A <code>FilterInputStream</code> contains
 * some other input stream, which it uses as
 * its  basic source of data, possibly transforming
 * the data along the way or providing  additional
 * functionality. The class <code>FilterInputStream</code>
 * itself simply overrides all  methods of
 * <code>InputStream</code> with versions that
 * pass all requests to the contained  input
 * stream. Subclasses of <code>FilterInputStream</code>
 * may further override some of  these methods
 * and may also provide additional methods
 * and fields.
 *
 * @author  Jonathan Payne
 * @since   1.0
 */
class FilterInputStream : InputStream {
    /**
     * The input stream to be filtered.
     */
    protected InputStream inputStream;

    /**
     * Creates a <code>FilterInputStream</code>
     * by assigning the  argument <code>inputStream</code>
     * to the field <code>this.inputStream</code> so as
     * to remember it for later use.
     *
     * @param   inputStream   the underlying input stream, or <code>null</code> if
     *          this instance is to be created without an underlying stream.
     */
    protected this(InputStream inputStream) {
        this.inputStream = inputStream;
    }

    /**
     * Reads the next byte of data from this input stream. The value
     * byte is returned as an <code>int</code> in the range
     * <code>0</code> to <code>255</code>. If no byte is available
     * because the end of the stream has been reached, the value
     * <code>-1</code> is returned. This method blocks until input data
     * is available, the end of the stream is detected, or an exception
     * is thrown.
     * <p>
     * This method
     * simply performs <code>inputStream.read()</code> and returns the result.
     *
     * @return     the next byte of data, or <code>-1</code> if the end of the
     *             stream is reached.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterInputStream#inputStream
     */
    override int read() {
        return inputStream.read();
    }

    /**
     * Reads up to <code>b.length</code> bytes of data from this
     * input stream into an array of bytes. This method blocks until some
     * input is available.
     * <p>
     * This method simply performs the call
     * <code>read(b, 0, b.length)</code> and returns
     * the  result. It is important that it does
     * <i>not</i> do <code>inputStream.read(b)</code> instead;
     * certain subclasses of  <code>FilterInputStream</code>
     * depend on the implementation strategy actually
     * used.
     *
     * @param      b   the buffer into which the data is read.
     * @return     the total number of bytes read into the buffer, or
     *             <code>-1</code> if there is no more data because the end of
     *             the stream has been reached.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterInputStream#read(byte[], int, int)
     */
    override int read(byte[] b) {
        return read(b, 0, cast(int)b.length);
    }

    /**
     * Reads up to <code>len</code> bytes of data from this input stream
     * into an array of bytes. If <code>len</code> is not zero, the method
     * blocks until some input is available; otherwise, no
     * bytes are read and <code>0</code> is returned.
     * <p>
     * This method simply performs <code>inputStream.read(b, off, len)</code>
     * and returns the result.
     *
     * @param      b     the buffer into which the data is read.
     * @param      off   the start offset inputStream the destination array <code>b</code>
     * @param      len   the maximum number of bytes read.
     * @return     the total number of bytes read into the buffer, or
     *             <code>-1</code> if there is no more data because the end of
     *             the stream has been reached.
     * @exception  NullPointerException If <code>b</code> is <code>null</code>.
     * @exception  IndexOutOfBoundsException If <code>off</code> is negative,
     * <code>len</code> is negative, or <code>len</code> is greater than
     * <code>b.length - off</code>
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterInputStream#inputStream
     */
    override int read(byte[] b, int off, int len) {
        return inputStream.read(b, off, len);
    }

    /**
     * Skips over and discards <code>n</code> bytes of data from the
     * input stream. The <code>skip</code> method may, for a variety of
     * reasons, end up skipping over some smaller number of bytes,
     * possibly <code>0</code>. The actual number of bytes skipped is
     * returned.
     * <p>
     * This method simply performs <code>inputStream.skip(n)</code>.
     *
     * @param      n   the number of bytes to be skipped.
     * @return     the actual number of bytes skipped.
     * @throws     IOException  if {@code inputStream.skip(n)} throws an IOException.
     */
    override long skip(long n) {
        return inputStream.skip(n);
    }

    /**
     * Returns an estimate of the number of bytes that can be read (or
     * skipped over) from this input stream without blocking by the next
     * caller of a method for this input stream. The next caller might be
     * the same thread or another thread.  A single read or skip of this
     * many bytes will not block, but may read or skip fewer bytes.
     * <p>
     * This method returns the result of {@link #inputStream inputStream}.available().
     *
     * @return     an estimate of the number of bytes that can be read (or skipped
     *             over) from this input stream without blocking.
     * @exception  IOException  if an I/O error occurs.
     */
    override int available() {
        return inputStream.available();
    }

    /**
     * Closes this input stream and releases any system resources
     * associated with the stream.
     * This
     * method simply performs <code>inputStream.close()</code>.
     *
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterInputStream#inputStream
     */
    override void close() {
        inputStream.close();
    }

    /**
     * Marks the current position in this input stream. A subsequent
     * call to the <code>reset</code> method repositions this stream at
     * the last marked position so that subsequent reads re-read the same bytes.
     * <p>
     * The <code>readlimit</code> argument tells this input stream to
     * allow that many bytes to be read before the mark position gets
     * invalidated.
     * <p>
     * This method simply performs <code>inputStream.mark(readlimit)</code>.
     *
     * @param   readlimit   the maximum limit of bytes that can be read before
     *                      the mark position becomes invalid.
     * @see     java.io.FilterInputStream#inputStream
     * @see     java.io.FilterInputStream#reset()
     */
    override void mark(int readlimit) {
        inputStream.mark(readlimit);
    }

    /**
     * Repositions this stream to the position at the time the
     * <code>mark</code> method was last called on this input stream.
     * <p>
     * This method
     * simply performs <code>inputStream.reset()</code>.
     * <p>
     * Stream marks are intended to be used in
     * situations where you need to read ahead a little to see what's in
     * the stream. Often this is most easily done by invoking some
     * general parser. If the stream is of the type handled by the
     * parse, it just chugs along happily. If the stream is not of
     * that type, the parser should toss an exception when it fails.
     * If this happens within readlimit bytes, it allows the outer
     * code to reset the stream and try another parser.
     *
     * @exception  IOException  if the stream has not been marked or if the
     *               mark has been invalidated.
     * @see        java.io.FilterInputStream#inputStream
     * @see        java.io.FilterInputStream#mark(int)
     */
    override void reset() {
        inputStream.reset();
    }

    /**
     * Tests if this input stream supports the <code>mark</code>
     * and <code>reset</code> methods.
     * This method
     * simply performs <code>inputStream.markSupported()</code>.
     *
     * @return  <code>true</code> if this stream type supports the
     *          <code>mark</code> and <code>reset</code> method;
     *          <code>false</code> otherwise.
     * @see     java.io.FilterInputStream#inputStream
     * @see     java.io.InputStream#mark(int)
     * @see     java.io.InputStream#reset()
     */
    override bool markSupported() {
        return inputStream.markSupported();
    }
}