com.kolibrifx.plovercrest.server.internal.streams.RangeStreamObserver Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of plovercrest-server Show documentation

Plovercrest server library.

The newest version!

/*
 * Copyright (c) 2010-2017, KolibriFX AS. Licensed under the Apache License, version 2.0.
 */

package com.kolibrifx.plovercrest.server.internal.streams;

import com.kolibrifx.plovercrest.server.streams.StreamObserver;

/**
 * Base class for observing a range of elements.
 */
public abstract class RangeStreamObserver implements StreamObserver {
    @SuppressWarnings("serial")
    static class EndOfRangeException extends RuntimeException {
    }

    /** Exception constant used for simple control flow. */
    private static final EndOfRangeException END_OF_RANGE = new EndOfRangeException();

    private StreamObserver wrappedObserver;
    private int observedCount = 0;
    private long lastObserved = -1;
    private boolean atEndOfStream = false;
    private long lastValidTimestamp = -1;

    public RangeStreamObserver(final StreamObserver wrappedObserver) {
        this.wrappedObserver = wrappedObserver;
    }

    @Override
    public void onObserveEnd(final long lastValidTimestamp, final long elementCount) {
        atEndOfStream = true;
        this.lastValidTimestamp = lastValidTimestamp;
    }

    @Override
    public void onObserveFrozen() {
        wrappedObserver.onObserveFrozen();
    }

    protected void throwEndOfRange() {
        throw END_OF_RANGE;
    }

    protected void callWrappedObserver(final long timestamp, final long index, final T element) {
        wrappedObserver.onObserve(timestamp, index, element);
        observedCount++;
        lastObserved = timestamp;
    }

    public int getObservedCount() {
        return observedCount;
    }

    public boolean isAtEndOfStream() {
        return atEndOfStream;
    }

    public long getLastValidTimestamp() {
        return Math.max(lastValidTimestamp, lastObserved);
    }

    /**
     * Call to replace the wrapped observer: useful when resuming a read.
     */
    public void setWrappedObserver(final StreamObserver observer) {
        this.wrappedObserver = observer;
    }

    @Override
    public final void onObserve(final long timestamp, final long index, final T element) {
        atEndOfStream = false;
        onObserveImpl(timestamp, index, element);
    }

    protected abstract void onObserveImpl(long timestamp, long index, T element);
}