il.ac.bgu.cs.bp.bpjs.model.eventselection.AbstractEventSelectionStrategy Maven / Gradle / Ivy
/*
* The MIT License
*
* Copyright 2017 BGU.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
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package il.ac.bgu.cs.bp.bpjs.model.eventselection;
import il.ac.bgu.cs.bp.bpjs.model.SyncStatement;
import il.ac.bgu.cs.bp.bpjs.model.BEvent;
import il.ac.bgu.cs.bp.bpjs.model.BProgramSyncSnapshot;
import il.ac.bgu.cs.bp.bpjs.model.eventsets.EventSet;
import java.util.ArrayList;
import static java.util.Collections.singleton;
import java.util.List;
import java.util.Optional;
import java.util.Random;
import java.util.Set;
import java.util.stream.Collectors;
import static java.util.stream.Collectors.toSet;
import org.mozilla.javascript.Context;
/**
* A convenience class for implementing event selection strategies. Contains mostly reusable code for randomizing selectable events.
*
*
* @author michael
*/
public abstract class AbstractEventSelectionStrategy implements EventSelectionStrategy {
protected final Random rnd;
protected final long seed;
public AbstractEventSelectionStrategy( long seed ) {
rnd = new Random(seed);
this.seed = seed;
}
public AbstractEventSelectionStrategy() {
rnd = new Random();
seed = rnd.nextLong();
rnd.setSeed(seed);
}
public long getSeed() {
return seed;
}
/**
* Randomly select an event from {@code selectableEvents}, or a non-blocked event from {@code externalEvents}, in case {@code selectableEvents} is empty.
*
* @param bpss a b-program at synchronization point.
* @param selectableEvents Set of events that can be selected.
* @return An optional event selection result.
*/
@Override
public Optional select(BProgramSyncSnapshot bpss, Set selectableEvents) {
if (selectableEvents.isEmpty()) {
return Optional.empty();
}
BEvent chosen = new ArrayList<>(selectableEvents).get(rnd.nextInt(selectableEvents.size()));
Set requested = bpss.getStatements().stream()
.filter((SyncStatement stmt) -> stmt != null)
.flatMap((SyncStatement stmt) -> stmt.getRequest().stream())
.collect(Collectors.toSet());
if (requested.contains(chosen)) {
return Optional.of(new EventSelectionResult(chosen));
} else {
// that was an external event, need to find the first index
return Optional.of(new EventSelectionResult(chosen, singleton(bpss.getExternalEvents().indexOf(chosen))));
}
}
protected Set getRequestedAndNotBlocked(SyncStatement stmt, EventSet blocked) {
try {
Context.enter();
return stmt.getRequest().stream().filter((BEvent req) -> !blocked.contains(req)).collect(toSet());
} finally {
Context.exit();
}
}
}