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 * Copyright (c) 2021, 2024, 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
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package jdk.internal.net.http.qpack.readers;

import java.io.IOException;
import java.net.ProtocolException;
import java.nio.ByteBuffer;
import java.util.Arrays;

import jdk.internal.net.http.hpack.ISO_8859_1;
import jdk.internal.net.http.hpack.Huffman;
import jdk.internal.net.http.hpack.QuickHuffman;
import jdk.internal.net.http.http3.Http3Error;

//
//          0   1   2   3   4   5   6   7
//        +---+---+---+---+---+---+---+---+
//        | H |    String Length (7+)     |
//        +---+---------------------------+
//        |  String Data (Length octets)  |
//        +-------------------------------+
//
public 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 ReaderError readError;
    private final IntegerReader intReader;
    private final Huffman.Reader huffmanReader = new QuickHuffman.Reader();
    private final ISO_8859_1.Reader plainReader = new ISO_8859_1.Reader();

    private int state = NEW;
    private boolean huffman;
    private int remainingLength;

    public StringReader() {
        this(new ReaderError(Http3Error.H3_INTERNAL_ERROR, true));
    }

    public StringReader(ReaderError readError) {
        this.readError = readError;
        this.intReader = new IntegerReader(readError);
    }

    public boolean read(ByteBuffer input, Appendable output, int maxLength) {
        return read(7, input, output, maxLength);
    }

    boolean read(int N, ByteBuffer input, Appendable output, int maxLength) {
        if (state == DONE) {
            return true;
        }
        if (!input.hasRemaining()) {
            return false;
        }
        if (state == NEW) {
            int huffmanBit = switch (N) {
                case 7 -> 0b1000_0000; // for all value strings
                case 5 -> 0b0010_0000; // in name string for insert literal
                case 3 -> 0b0000_1000; // in name string for literal
                default -> throw new IllegalStateException("Unexpected value: " + N);
            };
            int p = input.position();
            huffman = (input.get(p) & huffmanBit) != 0;
            state = FIRST_BYTE_READ;
            intReader.configure(N);
        }
        if (state == FIRST_BYTE_READ) {
            boolean lengthRead = intReader.read(input);
            if (!lengthRead) {
                return false;
            }
            long remainingLengthLong = intReader.get();
            if (maxLength >= 0) {
                long huffmanEstimate = huffman ?
                        remainingLengthLong / 4 : remainingLengthLong;
                if (huffmanEstimate > maxLength) {
                    throw readError.toQPackException(new ProtocolException(
                            "Size exceeds MAX_FIELD_SECTION_SIZE or dynamic table capacity."));
                }
            }
            remainingLength = (int) remainingLengthLong;
            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);
            try {
                if (huffman) {
                    huffmanReader.read(input, output, isLast);
                } else {
                    plainReader.read(input, output);
                }
            } catch (IOException ioe) {
                throw readError.toQPackException(ioe);
            }
            if (isLast) {
                input.limit(oldLimit);
                state = DONE;
            }
            return isLast;
        }
        throw new InternalError(Arrays.toString(
                new Object[]{state, huffman, remainingLength}));
    }

    public boolean isHuffmanEncoded() {
        if (state < FIRST_BYTE_READ) {
            throw new IllegalStateException("Has not been fully read yet");
        }
        return huffman;
    }

    public void reset() {
        if (huffman) {
            huffmanReader.reset();
        } else {
            plainReader.reset();
        }
        intReader.reset();
        state = NEW;
    }
}