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package org.onap.sdc.dcae.catalog.commons;
import java.util.List;
import java.util.LinkedList;
import java.util.Collections;
import java.util.concurrent.CountDownLatch;
import java.util.function.Function;
import org.onap.sdc.common.onaplog.OnapLoggerDebug;
import org.onap.sdc.common.onaplog.Enums.LogLevel;
/**
*/
public class Futures<T> {
private Futures() {
}
public static <T> Future<T> failedFuture(Throwable theError) {
return new BasicFuture<T>()
.cause(theError);
}
public static <T> Future<T> succeededFuture(T theResult) {
return new BasicFuture<T>()
.result(theResult);
}
public static <T> Future<T> future() {
return new BasicFuture<T>();
}
public static <U,V> Future<V> advance(Future<U> theStep,
final Function<U,V> theResultFunction) {
return advance(theStep, theResultFunction, Function.identity());
}
public static <U,V> Future<V> advance(Future<U> theStep,
final Function<U,V> theResultFunction,
final Function<Throwable, Throwable> theErrorFunction) {
final Future<V> adv = new BasicFuture<V>();
theStep.setHandler(new FutureHandler<U>() {
public void handle(Future<U> theResult) {
if (theResult.failed())
adv.cause(theErrorFunction.apply(theResult.cause()));
else
adv.result(theResultFunction.apply(theResult.result()));
}
});
return adv;
}
/** */
public static class BasicFuture<T> implements Future<T> {
protected boolean succeeded,
failed;
protected FutureHandler<T> handler;
protected Throwable cause;
protected T result;
protected BasicFuture() {
}
public T result() {
return this.result;
}
public Future<T> result(T theResult) {
this.result = theResult;
this.succeeded = true;
this.cause = null;
this.failed = false;
callHandler();
return this;
}
public Throwable cause() {
return this.cause;
}
public Future<T> cause(Throwable theCause) {
this.cause = theCause;
this.failed = true;
this.result = null;
this.succeeded = false;
callHandler();
return this;
}
public boolean succeeded() {
return this.succeeded;
}
public boolean failed() {
return this.failed;
}
public boolean complete() {
return this.failed || this.succeeded;
}
public Future<T> setHandler(FutureHandler<T> theHandler) {
this.handler = theHandler;
callHandler();
return this;
}
public T waitForResult() throws Exception {
BasicHandler<T> hnd = buildHandler();
setHandler(hnd);
hnd.waitForCompletion();
if (failed())
throw (Exception)cause();
else
return result();
}
public Future<T> waitForCompletion() throws InterruptedException {
BasicHandler<T> hnd = buildHandler();
setHandler(hnd);
hnd.waitForCompletion();
return this;
}
protected void callHandler() {
if (this.handler != null && complete()) {
this.handler.handle(this);
}
}
protected BasicHandler<T> buildHandler() {
return new BasicHandler<T>();
}
}
/** */
public static class BasicHandler<T>
implements FutureHandler<T> {
protected T result = null;
protected Throwable error = null;
protected CountDownLatch latch = null;
BasicHandler() {
this(new CountDownLatch(1));
}
BasicHandler(CountDownLatch theLatch) {
this.latch = theLatch;
}
public void handle(Future<T> theResult) {
process(theResult);
if (this.latch != null) {
this.latch.countDown();
}
}
protected void process(Future<T> theResult) {
if (theResult.failed()) {
this.error = theResult.cause();
}
else {
this.result = theResult.result();
}
}
public T result(boolean doWait)
throws InterruptedException, RuntimeException {
if (doWait) {
waitForCompletion();
}
if (null == this.error)
return this.result;
throw new RuntimeException(this.error);
}
public T result()
throws InterruptedException, RuntimeException {
return result(true);
}
public BasicHandler<T> waitForCompletion() throws InterruptedException {
this.latch.await();
return this;
}
}
public static class Accumulator<T> extends BasicFuture<List<T>>
implements Future<List<T>> {
protected List<Future<T>> futures = new LinkedList<Future<T>>();
protected BasicHandler<T> accumulatorHandler = null;
private static OnapLoggerDebug debugLogger = OnapLoggerDebug.getInstance();
public Accumulator() {
this.result = new LinkedList<T>();
}
public Accumulator<T> add(Future<T> theFuture) {
debugLogger.log(LogLevel.DEBUG, this.getClass().getName(), "Intersection add");
this.futures.add(theFuture);
this.result.add(null);
return this;
}
public Accumulator<T> addAll(Accumulator<T> theFutures) {
debugLogger.log(LogLevel.DEBUG, this.getClass().getName(), "Intersection addAll");
return this;
}
public Future<List<T>> accumulate() {
this.futures = Collections.unmodifiableList(this.futures);
this.accumulatorHandler = new BasicHandler<T>(new CountDownLatch(this.futures.size())) {
protected void process(Future<T> theResult) {
if (theResult.failed()) {
Accumulator.this.cause = theResult.cause();
}
else {
Accumulator.this.result.set(
Accumulator.this.futures.indexOf(theResult), theResult.result());
}
if (this.latch.getCount() == 1) {
if (Accumulator.this.cause != null)
Accumulator.this.cause(Accumulator.this.cause);
else
Accumulator.this.result(Accumulator.this.result);
}
}
};
futures.stream()
.forEach(f -> f.setHandler(this.accumulatorHandler));
return this;
}
}
}
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