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Livedata SDK is a client library that enables easier integration with the Livedata XML feed. SDK exposes XML feed service interface in a more user-friendly way and isolates the client from having to do XML feed parsing, proper connection handling, error recovery, event queuing and dispatching. It also makes a client solution more stable and robust when it comes to feed handling, especially with the release of new and updated XML feed versions.

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/***************************************************************
 * Copyright (c) 2013, Sportradar AG                           *
 ***************************************************************/

package com.sportradar.livedata.sdk.proto.common;

import com.sportradar.livedata.sdk.common.exceptions.SdkException;
import com.sportradar.livedata.sdk.proto.dto.MessageBase;

import java.io.InputStream;

/**
 * Represents a base class for message parsers.
 */
public abstract class MessageParserBase implements MessageParser {

    private final MessageTokenizer tokenizer;

    /**
     * The {@link MessageParserListener} used to observe the current {@link MessageParserBase}
     */
    private volatile MessageParserListener listener;

    /**
     * Initializes a new instance of the {@link MessageParserBase} class.
     *
     * @param tokenizer A {@link MessageTokenizer} implementation used to tokenize received data, or a null reference.
     */
    protected MessageParserBase(MessageTokenizer tokenizer) {
        this.tokenizer = tokenizer;

        setDependencyListeners();
    }

    /**
     * Sets listeners on injected dependencies.
     */
    private void setDependencyListeners() {
        if (tokenizer == null) {
            return;
        }
        tokenizer.setListener(new MessageTokenizerListener() {
            @Override
            public void onMessageReady(InputStream stream) throws SdkException {
                onDataReady(stream);
            }
        });
    }

    /**
     * When overridden in derived class, it processes the received data.
     *
     * @param stream A {@link InputStream} implementation containing the received data.
     * @throws SdkException thrown when an un-expected situation is encountered.
     */
    protected abstract void onDataReady(InputStream stream) throws SdkException;

    /**
     * Notifies the attached observer that message was successfully parsed.
     *
     * @param message the parsed message
     */
    protected void notifyMessageReady(T message) {
        MessageParserListener copy = this.listener;
        if (copy != null) {
            copy.onMessageReady(message);
        }
    }

    /**
     * Processes passed data. If passed data and any previously stored data represent a whole message the {@code MessageParserListener.onMessageReady(T)} method is invoked
     *
     * @param stream A {@link InputStream} instance containing message data.
     * @throws IllegalArgumentException the {@code stream} is a null reference.
     * @throws ProtocolException        the data could not be processed either because the buffer is full, an un-expected character was encountered or there was an error while un-marshalling the message
     */
    public final void processData(InputStream stream) throws SdkException {
        if (tokenizer != null) {
            tokenizer.processData(stream);
        } else {
            onDataReady(stream);
        }
    }

    /**
     * Removes any data potentially left in the parser's buffer.
     */
    public void clear() {
        if (tokenizer != null) {
            tokenizer.clear();
        }
    }


    /**
     * Sets the {@link MessageParserListener} instance used to observe the current {@link MessageParserBase}
     *
     * @param listener The {@link MessageParserListener} instance used to observe the current {@link MessageParserBase} or a null reference.
     */
    public void setListener(MessageParserListener listener) {
        this.listener = listener;
    }
}