/*

 * 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

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package jdk.internal.net.http.websocket;

import jdk.internal.net.http.common.Utils;

import jdk.internal.net.http.websocket.Frame.Opcode;

import java.nio.ByteBuffer;

import java.nio.CharBuffer;

import java.nio.charset.CharacterCodingException;

import static java.lang.String.format;

import java.lang.System.Logger.Level;

import static java.nio.charset.StandardCharsets.UTF_8;

import static java.util.Objects.requireNonNull;

import static jdk.internal.net.http.common.Utils.dump;

import static jdk.internal.net.http.websocket.StatusCodes.NO_STATUS_CODE;

import static jdk.internal.net.http.websocket.StatusCodes.isLegalToReceiveFromServer;

/*

 * Consumes frame parts and notifies a message consumer, when there is

 * sufficient data to produce a message, or part thereof.

 *

 * Data consumed but not yet translated is accumulated until it's sufficient to

 * form a message.

 */

/* Exposed for testing purposes */

class MessageDecoder implements Frame.Consumer {

    private static final boolean DEBUG = Utils.DEBUG_WS;

    private static final System.Logger debug =

            Utils.getWebSocketLogger("[Input]"::toString, DEBUG);

    private final MessageStreamConsumer output;

    private final UTF8AccumulatingDecoder decoder = new UTF8AccumulatingDecoder();

    private boolean fin;

    private Opcode opcode, originatingOpcode;

    private long payloadLen;

    private long unconsumedPayloadLen;

    private ByteBuffer binaryData;

    MessageDecoder(MessageStreamConsumer output) {

        this.output = requireNonNull(output);

    }

    /* Exposed for testing purposes */

    MessageStreamConsumer getOutput() {

        return output;

    }

    @Override

    public void fin(boolean value) {

        fin = value;

    }

    @Override

    public void rsv1(boolean value) {

        if (value) {

            throw new FailWebSocketException("Unexpected rsv1 bit");

        }

    }

    @Override

    public void rsv2(boolean value) {

        if (value) {

            throw new FailWebSocketException("Unexpected rsv2 bit");

        }

    }

    @Override

    public void rsv3(boolean value) {

        if (value) {

            throw new FailWebSocketException("Unexpected rsv3 bit");

        }

    }

    @Override

    public void opcode(Opcode v) {

        if (v == Opcode.PING || v == Opcode.PONG || v == Opcode.CLOSE) {

            if (!fin) {

                throw new FailWebSocketException("Fragmented control frame  " + v);

            }

            opcode = v;

        } else if (v == Opcode.TEXT || v == Opcode.BINARY) {

            if (originatingOpcode != null) {

                throw new FailWebSocketException(

                        format("Unexpected frame %s (fin=%s)", v, fin));

            }

            opcode = v;

            if (!fin) {

                originatingOpcode = v;

            }

        } else if (v == Opcode.CONTINUATION) {

            if (originatingOpcode == null) {

                throw new FailWebSocketException(

                        format("Unexpected frame %s (fin=%s)", v, fin));

            }

            opcode = v;

        } else {

            throw new FailWebSocketException("Unexpected opcode " + v);

        }

    }

    @Override

    public void mask(boolean value) {

        if (value) {

            throw new FailWebSocketException("Masked frame received");

        }

    }

    @Override

    public void payloadLen(long value) {

        if (opcode.isControl()) {

            if (value > Frame.MAX_CONTROL_FRAME_PAYLOAD_LENGTH) {

                throw new FailWebSocketException(

                        format("%s's payload length %s", opcode, value));

            }

            assert Opcode.CLOSE.isControl();

            if (opcode == Opcode.CLOSE && value == 1) {

                throw new FailWebSocketException("Incomplete status code");

            }

        }

        payloadLen = value;

        unconsumedPayloadLen = value;

    }

    @Override

    public void maskingKey(int value) {

        // `MessageDecoder.mask(boolean)` is where a masked frame is detected and

        // reported on; `MessageDecoder.mask(boolean)` MUST be invoked before

        // this method;

        // So this method (`maskingKey`) is not supposed to be invoked while

        // reading a frame that has came from the server. If this method is

        // invoked, then it's an error in implementation, thus InternalError

        throw new InternalError();

    }

    @Override

    public void payloadData(ByteBuffer data) {

        unconsumedPayloadLen -= data.remaining();

        boolean lastPayloadChunk = unconsumedPayloadLen == 0;

        if (opcode.isControl()) {

            if (binaryData != null) { // An intermediate or the last chunk

                binaryData.put(data);

            } else if (!lastPayloadChunk) { // The first chunk

                int remaining = data.remaining();

                // It shouldn't be 125, otherwise the next chunk will be of size

                // 0, which is not what Reader promises to deliver (eager

                // reading)

                assert remaining < Frame.MAX_CONTROL_FRAME_PAYLOAD_LENGTH

                        : dump(remaining);

                binaryData = ByteBuffer.allocate(

                        Frame.MAX_CONTROL_FRAME_PAYLOAD_LENGTH).put(data);

            } else { // The only chunk

                binaryData = ByteBuffer.allocate(data.remaining()).put(data);

            }

        } else {

            boolean last = fin && lastPayloadChunk;

            boolean text = opcode == Opcode.TEXT || originatingOpcode == Opcode.TEXT;

            if (!text) {

                output.onBinary(data.slice(), last);

                data.position(data.limit()); // Consume

            } else {

                boolean binaryNonEmpty = data.hasRemaining();

                CharBuffer textData;

                try {

                    textData = decoder.decode(data, last);

                } catch (CharacterCodingException e) {

                    throw new FailWebSocketException(

                            "Invalid UTF-8 in frame " + opcode,

                            StatusCodes.NOT_CONSISTENT).initCause(e);

                }

                if (!(binaryNonEmpty && !textData.hasRemaining())) {

                    // If there's a binary data, that result in no text, then we

                    // don't deliver anything, otherwise:

                    output.onText(textData, last);

                }

            }

        }

    }

    @Override

    public void endFrame() {

        if (opcode.isControl()) {

            binaryData.flip();

        }

        switch (opcode) {

            case CLOSE:

                char statusCode = NO_STATUS_CODE;

                String reason = "";

                if (payloadLen != 0) {

                    int len = binaryData.remaining();

                    assert 2 <= len

                            && len <= Frame.MAX_CONTROL_FRAME_PAYLOAD_LENGTH

                            : dump(len, payloadLen);

                    statusCode = binaryData.getChar();

                    if (!isLegalToReceiveFromServer(statusCode)) {

                        throw new FailWebSocketException(

                                "Illegal status code: " + statusCode);

                    }

                    try {

                        reason = UTF_8.newDecoder().decode(binaryData).toString();

                    } catch (CharacterCodingException e) {

                        throw new FailWebSocketException("Illegal close reason")

                                .initCause(e);

                    }

                }

                output.onClose(statusCode, reason);

                break;

            case PING:

                output.onPing(binaryData);

                binaryData = null;

                break;

            case PONG:

                output.onPong(binaryData);

                binaryData = null;

                break;

            default:

                assert opcode == Opcode.TEXT || opcode == Opcode.BINARY

                        || opcode == Opcode.CONTINUATION : dump(opcode);

                if (fin) {

                    // It is always the last chunk:

                    // either TEXT(FIN=TRUE)/BINARY(FIN=TRUE) or CONT(FIN=TRUE)

                    originatingOpcode = null;

                }

                break;

        }

        payloadLen = 0;

        opcode = null;

    }

}