/*

 * reserved comment block

 * DO NOT REMOVE OR ALTER!

 */

/*

 * Copyright 1999-2004 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.sun.org.apache.regexp.internal;

import java.io.Reader;

import java.io.IOException;

/**

 * Encapsulates java.io.Reader as CharacterIterator

 *

 * @author <a href="mailto:ales.novak@netbeans.com">Ales Novak</a>

 */

public final class ReaderCharacterIterator implements CharacterIterator

{

    /** Underlying reader */

    private final Reader reader;

    /** Buffer of read chars */

    private final StringBuffer buff;

    /** read end? */

    private boolean closed;

    /** @param reader a Reader, which is parsed */

    public ReaderCharacterIterator(Reader reader)

    {

        this.reader = reader;

        this.buff = new StringBuffer(512);

        this.closed = false;

    }

    /** @return a substring */

    public String substring(int beginIndex, int endIndex)

    {

        try

        {

            ensure(endIndex);

            return buff.toString().substring(beginIndex, endIndex);

        }

        catch (IOException e)

        {

            throw new StringIndexOutOfBoundsException(e.getMessage());

        }

    }

    /** @return a substring */

    public String substring(int beginIndex)

    {

        try

        {

            readAll();

            return buff.toString().substring(beginIndex);

        }

        catch (IOException e)

        {

            throw new StringIndexOutOfBoundsException(e.getMessage());

        }

    }

    /** @return a character at the specified position. */

    public char charAt(int pos)

    {

        try

        {

            ensure(pos);

            return buff.charAt(pos);

        }

        catch (IOException e)

        {

            throw new StringIndexOutOfBoundsException(e.getMessage());

        }

    }

    /** @return <tt>true</tt> iff if the specified index is after the end of the character stream */

    public boolean isEnd(int pos)

    {

        if (buff.length() > pos)

        {

            return false;

        }

        else

        {

            try

            {

                ensure(pos);

                return (buff.length() <= pos);

            }

            catch (IOException e)

            {

                throw new StringIndexOutOfBoundsException(e.getMessage());

            }

        }

    }

    /** Reads n characters from the stream and appends them to the buffer */

    private int read(int n) throws IOException

    {

        if (closed)

        {

            return 0;

        }

        char[] c = new char[n];

        int count = 0;

        int read = 0;

        do

        {

            read = reader.read(c);

            if (read < 0) // EOF

            {

                closed = true;

                break;

            }

            count += read;

            buff.append(c, 0, read);

        }

        while (count < n);

        return count;

    }

    /** Reads rest of the stream. */

    private void readAll() throws IOException

    {

        while(! closed)

        {

            read(1000);

        }

    }

    /** Reads chars up to the idx */

    private void ensure(int idx) throws IOException

    {

        if (closed)

        {

            return;

        }

        if (idx < buff.length())

        {

            return;

        }

        read(idx + 1 - buff.length());

    }

}