/*
 * Copyright (c) 2014, Harald Kuhr
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name "TwelveMonkeys" nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package com.twelvemonkeys.imageio.plugins.pnm;

import com.twelvemonkeys.util.StringTokenIterator;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.nio.charset.Charset;

final class Plain16BitDecoder extends InputStream {
    private final BufferedReader reader;

    private StringTokenIterator currentLine;
    private int leftOver = -1;

    public Plain16BitDecoder(final InputStream in) {
        reader = new BufferedReader(new InputStreamReader(in, Charset.forName("ASCII")));
    }

    @Override public int read() throws IOException {
        if (leftOver != -1) {
            int next = leftOver;
            leftOver = -1;

            return next;
        }

        // Each number is one byte. Skip whitespace.
        if (currentLine == null || !currentLine.hasNext()) {
            String line = reader.readLine();
            if (line == null) {
                return -1;
            }

            currentLine = new StringTokenIterator(line);

            if (!currentLine.hasNext()) {
                return -1;
            }
        }

        int next = Integer.parseInt(currentLine.next()) & 0xffff;
        leftOver = next & 0xff;

        return (next >> 8) & 0xff;
    }

    @Override public void close() throws IOException {
        reader.close();
    }
}
