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/**
 * Copyright 2013-2016 Guoqiang Chen, Shanghai, China. All rights reserved.
 *
 *   Author: Guoqiang Chen
 *    Email: [email protected]
 *   WebURL: https://github.com/subchen
 *
 * 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.stream;

import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.Charset;
import java.nio.charset.CharsetEncoder;
import java.nio.charset.CoderResult;
import java.nio.charset.CodingErrorAction;

public class ReaderInputStream extends InputStream {
    private static final int DEFAULT_BUFFER_SIZE = 1024;

    private final Reader reader;
    private final CharsetEncoder encoder;
    private final CharBuffer encoderIn;
    private final ByteBuffer encoderOut;
    private CoderResult lastCoderResult;
    private boolean endOfInput;

    public ReaderInputStream(Reader reader, CharsetEncoder encoder) {
        this(reader, encoder, DEFAULT_BUFFER_SIZE);
    }

    public ReaderInputStream(Reader reader, CharsetEncoder encoder, int bufferSize) {
        this.reader = reader;
        this.encoder = encoder;
        encoderIn = CharBuffer.allocate(bufferSize);
        encoderIn.flip();
        encoderOut = ByteBuffer.allocate(128);
        encoderOut.flip();
    }

    public ReaderInputStream(Reader reader, Charset charset, int bufferSize) {
        this(reader, charset.newEncoder().onMalformedInput(CodingErrorAction.REPLACE).onUnmappableCharacter(CodingErrorAction.REPLACE), bufferSize);
    }

    public ReaderInputStream(Reader reader, Charset charset) {
        this(reader, charset, DEFAULT_BUFFER_SIZE);
    }

    public ReaderInputStream(Reader reader, String charsetName, int bufferSize) {
        this(reader, Charset.forName(charsetName), bufferSize);
    }

    public ReaderInputStream(Reader reader, String charsetName) {
        this(reader, charsetName, DEFAULT_BUFFER_SIZE);
    }

    public ReaderInputStream(Reader reader) {
        this(reader, Charset.defaultCharset());
    }

    private void fillBuffer() throws IOException {
        if ((!endOfInput) && ((lastCoderResult == null) || (lastCoderResult.isUnderflow()))) {
            encoderIn.compact();
            int position = encoderIn.position();

            int c = reader.read(encoderIn.array(), position, encoderIn.remaining());
            if (c == -1)
                endOfInput = true;
            else {
                encoderIn.position(position + c);
            }
            encoderIn.flip();
        }
        encoderOut.compact();
        lastCoderResult = encoder.encode(encoderIn, encoderOut, endOfInput);
        encoderOut.flip();
    }

    @Override
    public int read(byte[] b, int off, int len) throws IOException {
        if (b == null) {
            throw new NullPointerException("Byte array must not be null");
        }
        if ((len < 0) || (off < 0) || (off + len > b.length)) {
            throw new IndexOutOfBoundsException("Array Size=" + b.length + ", offset=" + off + ", length=" + len);
        }

        int read = 0;
        if (len == 0) {
            return 0;
        }
        while (len > 0) {
            if (encoderOut.hasRemaining()) {
                int c = Math.min(encoderOut.remaining(), len);
                encoderOut.get(b, off, c);
                off += c;
                len -= c;
                read += c;
            } else {
                fillBuffer();
                if ((endOfInput) && (!encoderOut.hasRemaining())) {
                    break;
                }
            }
        }
        return (read == 0) && (endOfInput) ? -1 : read;
    }

    @Override
    public int read(byte[] b) throws IOException {
        return read(b, 0, b.length);
    }

    @Override
    public int read() throws IOException {
        do {
            if (encoderOut.hasRemaining()) {
                return encoderOut.get() & 0xFF;
            }
            fillBuffer();
        } while ((!endOfInput) || (encoderOut.hasRemaining()));
        return -1;
    }

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