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/*
* esodata - data structures and other things, of varying utility
* Copyright 2022, Ben Culkin
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program 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 for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
package bjc.data;
import java.util.*;
import java.util.Map.Entry;
/**
* Represents a transition in a Petri net
* @author bjcul
*
* @param <Label> The type of the label
*/
public class PetriTransition<Label> {
private final Label name;
private Map<Label, Integer> sources;
private Map<Label, Integer> destinations;
/**
* Create a new transition
* @param name The name for this transition
*/
public PetriTransition(Label name) {
this.name = name;
sources = new HashMap<>();
destinations = new HashMap<>();
}
/**
* Add a source to this transition
*
* @param lab The label to move from
* @param tokens The number of tokens to move
*/
public void addSource(Label lab, int tokens) {
sources.merge(lab, tokens, (k, v) -> v + tokens);
}
/**
* Remove a source from this transition
*
* @param lab The source to remove
* @return The number of tokens that would've been moved
*/
public int removeSource(Label lab) {
return sources.remove(lab);
}
/**
* Add a destination to this transition.
*
* @param lab The label for the destination
* @param tokens The number of tokens to add
*/
public void addDestination(Label lab, int tokens) {
destinations.merge(lab, tokens, (k, v) -> v + tokens);
}
/**
* Remove a destination from this transition
*
* @param lab The destination to remove
*
* @return The number of tokens which would've moved
*/
public int removeDestination(Label lab) {
return destinations.remove(lab);
}
/**
* Apply this transition to a map
*
* @param nodes The map to apply the transition to
*
* @return Whether the transition was successfully applied.
*/
public boolean apply(Map<Label, Integer> nodes) {
Set<Entry<Label, Integer>> debts = new HashSet<>();
boolean failed = false;
for (Entry<Label, Integer> source : sources.entrySet()) {
Label lab = source.getKey();
int cost = source.getValue();
if (nodes.containsKey(lab)) {
int count = nodes.get(lab);
if (count > cost) {
nodes.put(lab, count - cost);
} else {
failed = true;
break;
}
} else {
throw new IllegalArgumentException("Node " + lab + "missing; needed for transition " + name);
}
}
// If we failed, we may need to re-deposit some tokens
if (failed) {
for (Entry<Label, Integer> debt : debts) {
nodes.computeIfPresent(debt.getKey(), (k, v) -> v + debt.getValue());
}
return false;
}
// NOTE: One possibility would be to use the same loop for both of these, and
// just negate sources by default.
for (Entry<Label, Integer> destination : destinations.entrySet()) {
Label lab = destination.getKey();
int profit = destination.getValue();
if (nodes.containsKey(lab)) {
int count = nodes.get(lab);
if (count > profit) {
nodes.put(lab, count + profit);
} else {
failed = true;
break;
}
} else {
throw new IllegalArgumentException("Node " + lab + "missing; needed for transition " + name);
}
}
return true;
}
/**
* Merge this transition with another one
*
* @param transition The transition to merge
*/
public void merge(PetriTransition<Label> transition) {
for (Entry<Label, Integer> source : transition.sources.entrySet()) {
int val = source.getValue();
sources.merge(source.getKey(), val, (k, v) -> v + val);
}
for (Entry<Label, Integer> destination : transition.destinations.entrySet()) {
int val = destination.getValue();
sources.merge(destination.getKey(), val, (k, v) -> v + val);
}
}
@Override
public String toString() {
return String.format("PetriTransition [name=%s, sources=%s, destinations=%s]", name, sources, destinations);
}
@Override
public int hashCode() {
return Objects.hash(destinations, name, sources);
}
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
PetriTransition<?> other = (PetriTransition<?>) obj;
return Objects.equals(destinations, other.destinations) && Objects.equals(name, other.name)
&& Objects.equals(sources, other.sources);
}
/**
* Create a transition from merging a bunch
*
* @param <Label> The type of the label
*
* @param mergeName The label for the merged transition
* @param transitions The transitions to merge
*
* @return A transition created by merging the given ones
*/
@SafeVarargs
public static <Label> PetriTransition<Label> merged(Label mergeName, PetriTransition<Label>... transitions) {
PetriTransition<Label> result = new PetriTransition<>(mergeName);
for (PetriTransition<Label> transition : transitions) {
result.merge(transition);
}
return result;
}
}
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