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/*
 * Copyright (c) 2016, 2020 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package org.glassfish.grizzly.http2.hpack;

import java.util.Arrays;

import org.glassfish.grizzly.Buffer;

//
//          0   1   2   3   4   5   6   7
//        +---+---+---+---+---+---+---+---+
//        | H |    String Length (7+)     |
//        +---+---------------------------+
//        |  String Data (Length octets)  |
//        +-------------------------------+
//
final class StringReader {

    private static final byte NEW = 0x0;
    private static final byte FIRST_BYTE_READ = 0x1;
    private static final byte LENGTH_READ = 0x2;
    private static final byte DONE = 0x4;

    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 byte state = NEW;

    private boolean huffman;
    private int remainingLength;

    boolean read(Buffer input, Appendable output) {
        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;
    }
}