/**
 * Copyright 2013-2014 Guoqiang Chen, Shanghai, China. All rights reserved.
 *
 * Email: subchen@gmail.com
 * URL: http://subchen.github.io/
 *
 * 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 jetbrick.io.streams;

import java.io.*;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.*;

public class WriterOutputStream extends OutputStream {
    private static final int DEFAULT_BUFFER_SIZE = 1024;

    private final Writer writer;
    private final CharsetDecoder decoder;
    private final boolean writeImmediately;
    private final ByteBuffer decoderIn = ByteBuffer.allocate(128);
    private final CharBuffer decoderOut;

    public WriterOutputStream(Writer writer, CharsetDecoder decoder) {
        this(writer, decoder, DEFAULT_BUFFER_SIZE, false);
    }

    public WriterOutputStream(Writer writer, CharsetDecoder decoder, int bufferSize, boolean writeImmediately) {
        this.writer = writer;
        this.decoder = decoder;
        this.writeImmediately = writeImmediately;
        decoderOut = CharBuffer.allocate(bufferSize);
    }

    public WriterOutputStream(Writer writer, Charset charset, int bufferSize, boolean writeImmediately) {
        this(writer, charset.newDecoder().onMalformedInput(CodingErrorAction.REPLACE).onUnmappableCharacter(CodingErrorAction.REPLACE).replaceWith("?"), bufferSize, writeImmediately);
    }

    public WriterOutputStream(Writer writer, Charset charset) {
        this(writer, charset, DEFAULT_BUFFER_SIZE, false);
    }

    public WriterOutputStream(Writer writer, String charsetName, int bufferSize, boolean writeImmediately) {
        this(writer, Charset.forName(charsetName), bufferSize, writeImmediately);
    }

    public WriterOutputStream(Writer writer, String charsetName) {
        this(writer, charsetName, DEFAULT_BUFFER_SIZE, false);
    }

    public WriterOutputStream(Writer writer) {
        this(writer, Charset.defaultCharset(), DEFAULT_BUFFER_SIZE, false);
    }

    @Override
    public void write(byte[] b, int off, int len) throws IOException {
        while (len > 0) {
            int c = Math.min(len, decoderIn.remaining());
            decoderIn.put(b, off, c);
            processInput(false);
            len -= c;
            off += c;
        }
        if (writeImmediately) flushOutput();
    }

    @Override
    public void write(byte[] b) throws IOException {
        write(b, 0, b.length);
    }

    @Override
    public void write(int b) throws IOException {
        write(new byte[] { (byte) b }, 0, 1);
    }

    @Override
    public void flush() throws IOException {
        flushOutput();
        writer.flush();
    }

    @Override
    public void close() throws IOException {
        processInput(true);
        flushOutput();
        writer.close();
    }

    private void processInput(boolean endOfInput) throws IOException {
        decoderIn.flip();
        CoderResult coderResult;
        while (true) {
            coderResult = decoder.decode(decoderIn, decoderOut, endOfInput);
            if (!coderResult.isOverflow()) break;
            flushOutput();
        }
        if (!coderResult.isUnderflow()) {
            throw new IOException("Unexpected coder result");
        }

        decoderIn.compact();
    }

    private void flushOutput() throws IOException {
        if (decoderOut.position() > 0) {
            writer.write(decoderOut.array(), 0, decoderOut.position());
            decoderOut.rewind();
        }
    }
}