/*
 *         Twidere - Twitter client for Android
 *
 * Copyright 2012-2017 Mariotaku Lee <mariotaku.lee@gmail.com>
 *
 * 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 org.mariotaku.microblog.library.util;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.Reader;

/**
 * CRLFLineReader implements a readLine() method that requires
 * exactly CRLF to terminate an input line.
 * This is required for IMAP, which allows bare CR and LF.
 *
 * @since 3.0
 */
public final class CRLFLineReader extends BufferedReader
{
    private static final char LF = '\n';
    private static final char CR = '\r';

    /**
     * Creates a CRLFLineReader that wraps an existing Reader
     * input source.
     * @param reader  The Reader input source.
     */
    public CRLFLineReader(Reader reader)
    {
        super(reader);
    }

    /**
     * Read a line of text.
     * A line is considered to be terminated by carriage return followed immediately by a linefeed.
     * This contrasts with BufferedReader which also allows other combinations.
     * @since 3.0
     */
    @Override
    public String readLine() throws IOException {
        StringBuilder sb = new StringBuilder();
        int intch;
        boolean prevWasCR = false;
        //noinspection SynchronizeOnNonFinalField
        synchronized(lock) { // make thread-safe (hopefully!)
            while((intch = read()) != -1)
            {
                if (prevWasCR && intch == LF) {
                    return sb.substring(0, sb.length()-1);
                }
                prevWasCR = intch == CR;
                sb.append((char) intch);
            }
        }
        String string = sb.toString();
        if (string.length() == 0) { // immediate EOF
            return null;
        }
        return string;
    }
}