/*
 * Copyright 2004-2005 The Apache Software Foundation.
 *
 *  Licensed 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 com.cburch.logisim.file;

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

/**
 * Adapts a <code>Reader</code> as an <code>InputStream</code>.
 * Adapted from <CODE>StringInputStream</CODE>.
 *
 */
public class ReaderInputStream extends InputStream {

	/** Source Reader */
	private Reader in;

	private String encoding = System.getProperty("file.encoding");

	private byte[] slack;

	private int begin;

	/**
	 * Construct a <CODE>ReaderInputStream</CODE>
	 * for the specified <CODE>Reader</CODE>.
	 *
	 * @param reader   <CODE>Reader</CODE>.  Must not be <code>null</code>.
	 */
	public ReaderInputStream(Reader reader) {
		in = reader;
	}

	/**
	 * Construct a <CODE>ReaderInputStream</CODE>
	 * for the specified <CODE>Reader</CODE>,
	 * with the specified encoding.
	 *
	 * @param reader     non-null <CODE>Reader</CODE>.
	 * @param encoding   non-null <CODE>String</CODE> encoding.
	 */
	public ReaderInputStream(Reader reader, String encoding) {
		this(reader);
		if (encoding == null) {
			throw new IllegalArgumentException("encoding must not be null");
		} else {
			this.encoding = encoding;
		}
	}

	/**
	 * Reads from the <CODE>Reader</CODE>, returning the same value.
	 *
	 * @return the value of the next character in the <CODE>Reader</CODE>.
	 *
	 * @exception IOException if the original <code>Reader</code> fails to be read
	 */
	@Override
	public synchronized int read() throws IOException {
		if (in == null) {
			throw new IOException("Stream Closed");
		}

		byte result;
		if (slack != null && begin < slack.length) {
			result = slack[begin];
			if (++begin == slack.length) {
				slack = null;
			}
		} else {
			byte[] buf = new byte[1];
			if (read(buf, 0, 1) <= 0) {
				result = -1;
			}
			result = buf[0];
		}

		if (result < -1) {
			result += 256;
		}

		return result;
	}

	/**
	 * Reads from the <code>Reader</code> into a byte array
	 *
	 * @param b  the byte array to read into
	 * @param off the offset in the byte array
	 * @param len the length in the byte array to fill
	 * @return the actual number read into the byte array, -1 at
	 *         the end of the stream
	 * @exception IOException if an error occurs
	 */
	@Override
	public synchronized int read(byte[] b, int off, int len)
		throws IOException {
		if (in == null) {
			throw new IOException("Stream Closed");
		}

		while (slack == null) {
			char[] buf = new char[len]; // might read too much
			int n = in.read(buf);
			if (n == -1) {
				return -1;
			}
			if (n > 0) {
				slack = new String(buf, 0, n).getBytes(encoding);
				begin = 0;
			}
		}

		if (len > slack.length - begin) {
			len = slack.length - begin;
		}

		System.arraycopy(slack, begin, b, off, len);

		if ((begin += len) >= slack.length) {
			slack = null;
		}

		return len;
	}

	/**
	 * Marks the read limit of the StringReader.
	 *
	 * @param limit the maximum limit of bytes that can be read before the
	 *              mark position becomes invalid
	 */
	@Override
	public synchronized void mark(final int limit) {
		try {
			in.mark(limit);
		} catch (IOException ioe) {
			throw new RuntimeException(ioe.getMessage());
		}
	}


	/**
	 * @return   the current number of bytes ready for reading
	 * @exception IOException if an error occurs
	 */
	@Override
	public synchronized int available() throws IOException {
		if (in == null) {
			throw new IOException("Stream Closed");
		}
		if (slack != null) {
			return slack.length - begin;
		}
		if (in.ready()) {
			return 1;
		} else {
			return 0;
		}
	}

	/**
	 * @return false - mark is not supported
	 */
	@Override
	public boolean markSupported () {
		return false;   // would be imprecise
	}

	/**
	 * Resets the StringReader.
	 *
	 * @exception IOException if the StringReader fails to be reset
	 */
	@Override
	public synchronized void reset() throws IOException {
		if (in == null) {
			throw new IOException("Stream Closed");
		}
		slack = null;
		in.reset();
	}

	/**
	 * Closes the Stringreader.
	 *
	 * @exception IOException if the original StringReader fails to be closed
	 */
	@Override
	public synchronized void close() throws IOException {
		if (in != null) {
			in.close();
			slack = null;
			in = null;
		}
	}
}