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/*
 * Copyright 2016 the original author or authors.
 *
 * 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.gradle.internal.io;

import org.gradle.internal.SystemProperties;

import java.io.IOException;
import java.io.OutputStream;

/**
 * An OutputStream which separates bytes written into lines of text. Uses the platform default encoding. Is not thread safe.
 */
public class LineBufferingOutputStream extends OutputStream {
    private boolean hasBeenClosed;
    private final byte[] lineSeparator;
    private final int bufferIncrement;
    private final TextStream handler;
    private byte[] buf;
    private int count;

    public LineBufferingOutputStream(TextStream handler) {
        this(handler, 2048);
    }

    public LineBufferingOutputStream(TextStream handler, int bufferLength) {
        this.handler = handler;
        bufferIncrement = bufferLength;
        buf = new byte[bufferLength];
        count = 0;
        lineSeparator = SystemProperties.getInstance().getLineSeparator().getBytes();
    }

    /**
     * Closes this output stream and releases any system resources associated with this stream. The general contract of
     * close is that it closes the output stream. A closed stream cannot perform output operations and
     * cannot be reopened.
     */
    public void close() throws IOException {
        hasBeenClosed = true;
        flush();
        handler.endOfStream(null);
    }

    /**
     * Writes the specified byte to this output stream. The general contract for write is that one byte is
     * written to the output stream. The byte to be written is the eight low-order bits of the argument b.
     * The 24 high-order bits of b are ignored.
     *
     * @param b the byte to write
     * @throws java.io.IOException if an I/O error occurs. In particular, an IOException may be thrown if
     * the output stream has been closed.
     */
    public void write(final int b) throws IOException {
        if (hasBeenClosed) {
            throw new IOException("The stream has been closed.");
        }

        if (count == buf.length) {
            // grow the buffer
            final int newBufLength = buf.length + bufferIncrement;
            final byte[] newBuf = new byte[newBufLength];

            System.arraycopy(buf, 0, newBuf, 0, buf.length);
            buf = newBuf;
        }

        buf[count] = (byte) b;
        count++;
        if (endsWithLineSeparator()) {
            flush();
        }
    }

    private boolean endsWithLineSeparator() {
        if (count < lineSeparator.length) {
            return false;
        }
        for (int i = 0; i < lineSeparator.length; i++) {
            if (buf[count - lineSeparator.length + i] != lineSeparator[i]) {
                return false;
            }
        }
        return true;
    }

    public void flush() {
        if (count != 0) {
            handler.text(new String(buf, 0, count));
        }
        reset();
    }

    private void reset() {
        if (buf.length > bufferIncrement) {
            buf = new byte[bufferIncrement];
        }
        count = 0;
    }
}