/*

 * Copyright (c) 2015, 2018, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

import java.io.IOException;

import java.nio.ByteBuffer;

import java.util.Arrays;

//

//          0   1   2   3   4   5   6   7

//        +---+---+---+---+---+---+---+---+

//        | H |    String Length (7+)     |

//        +---+---------------------------+

//        |  String Data (Length octets)  |

//        +-------------------------------+

//

final class StringReader {

    private static final int NEW             = 0;

    private static final int FIRST_BYTE_READ = 1;

    private static final int LENGTH_READ     = 2;

    private static final int DONE            = 4;

    private final IntegerReader intReader = new IntegerReader();

    private final Huffman.Reader huffmanReader = new Huffman.Reader();

    private final ISO_8859_1.Reader plainReader = new ISO_8859_1.Reader();

    private int state = NEW;

    private boolean huffman;

    private int remainingLength;

    boolean read(ByteBuffer input, Appendable output) throws IOException {

        if (state == DONE) {

            return true;

        }

        if (!input.hasRemaining()) {

            return false;

        }

        if (state == NEW) {

            int p = input.position();

            huffman = (input.get(p) & 0b10000000) != 0;

            state = FIRST_BYTE_READ;

            intReader.configure(7);

        }

        if (state == FIRST_BYTE_READ) {

            boolean lengthRead = intReader.read(input);

            if (!lengthRead) {

                return false;

            }

            remainingLength = intReader.get();

            state = LENGTH_READ;

        }

        if (state == LENGTH_READ) {

            boolean isLast = input.remaining() >= remainingLength;

            int oldLimit = input.limit();

            if (isLast) {

                input.limit(input.position() + remainingLength);

            }

            remainingLength -= Math.min(input.remaining(), remainingLength);

            if (huffman) {

                huffmanReader.read(input, output, isLast);

            } else {

                plainReader.read(input, output);

            }

            if (isLast) {

                input.limit(oldLimit);

                state = DONE;

            }

            return isLast;

        }

        throw new InternalError(Arrays.toString(

                new Object[]{state, huffman, remainingLength}));

    }

    boolean isHuffmanEncoded() {

        if (state < FIRST_BYTE_READ) {

            throw new IllegalStateException("Has not been fully read yet");

        }

        return huffman;

    }

    void reset() {

        if (huffman) {

            huffmanReader.reset();

        } else {

            plainReader.reset();

        }

        intReader.reset();

        state = NEW;

    }

}