uniol.apt.adt.pn.PetriNet.java Source code

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/*-
 * APT - Analysis of Petri Nets and labeled Transition systems
 * Copyright (C) 2012-2013  Members of the project group APT
 *
 * 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 2 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, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

package uniol.apt.adt.pn;

import java.util.AbstractSet;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.Set;
import java.util.SortedMap;
import java.util.TreeMap;

import uniol.apt.adt.AbstractGraph;
import uniol.apt.adt.CollectionToUnmodifiableSetAdapter;
import uniol.apt.adt.EdgeKey;
import uniol.apt.adt.IGraph;
import uniol.apt.adt.SoftMap;
import uniol.apt.adt.exception.FlowExistsException;
import uniol.apt.adt.exception.IllegalFlowException;
import uniol.apt.adt.exception.NoSuchEdgeException;
import uniol.apt.adt.exception.NoSuchNodeException;
import uniol.apt.adt.exception.NodeExistsException;
import uniol.apt.adt.exception.StructureException;
import uniol.apt.adt.exception.TransitionFireException;

import static org.apache.commons.collections4.iterators.EmptyIterator.emptyIterator;

/**
 * The PetriNet is the base class for representing a petri net. With flows, places, transitions, a initial marking and
 * final markings.
 * @author Dennis-Michael Borde, Manuel Gieseking
 */
public class PetriNet extends AbstractGraph<PetriNet, Flow, Node> implements IGraph<PetriNet, Flow, Node> {

    private String name;
    private long nextPlaceId = 0;
    private long nextTransitionId = 0;
    private final SortedMap<String, Node> nodes = new TreeMap<>();
    private final SortedMap<String, Place> places = new TreeMap<>();
    private List<Place> placesList = Collections.emptyList();
    private final SortedMap<String, Transition> transitions = new TreeMap<>();
    private final Map<String, Set<Node>> presetNodes = new SoftMap<>();
    private final Map<String, Set<Node>> postsetNodes = new SoftMap<>();
    private final Map<String, Map<EdgeKey, Flow>> presetEdges = new HashMap<>();
    private final Map<String, Map<EdgeKey, Flow>> postsetEdges = new HashMap<>();
    private int numFlows = 0;
    private Marking initialMarking = new Marking(this);
    private final Set<Marking> finalMarkings = new HashSet<>();

    /**
     * Creates a new PetriNet with the name "".
     */
    public PetriNet() {
        this("");
    }

    /**
     * Creates a new PetriNet with the given name.
     * @param name Name of the petri net as String.
     */
    public PetriNet(String name) {
        this.name = name;
    }

    /**
     * Copies a petri net. The constructor also copies the references of the extensions.
     * @param pn the petri net that should be copied.
     */
    public PetriNet(PetriNet pn) {
        this.name = pn.name;
        this.nextPlaceId = pn.nextPlaceId;
        this.nextTransitionId = pn.nextTransitionId;
        for (String key : pn.places.keySet()) {
            this.addPlace(key, new Place(this, pn.places.get(key)));
        }
        for (String key : pn.transitions.keySet()) {
            this.addTransition(key, new Transition(this, pn.transitions.get(key)));
        }
        // Iterate over all EdgeKey instances
        for (Map<EdgeKey, Flow> postsets : pn.postsetEdges.values()) {
            for (Map.Entry<EdgeKey, Flow> entry : postsets.entrySet()) {
                this.addFlow(entry.getKey(), new Flow(this, entry.getValue()));
            }
        }
        for (Marking m : pn.finalMarkings) {
            this.finalMarkings.add(new Marking(this, m));
        }
        this.initialMarking = new Marking(this, pn.initialMarking);
        copyExtensions(pn);
    }

    /**
     * Creates a new flow in this petri net with the given sourceId, targetId and weight 1.
     * @param sourceId the id of the source node.
     * @param targetId the id of the target node.
     * @return a reference object to the created flow.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NoSuchNodeException      thrown if one of the ids does not match a node in this petri net.
     * @throws FlowExistsException      thrown if a flow with the same source and target already exists in this
     *                                  petri net.
     * @throws IllegalFlowException     thrown if argument don't correspond to a place and a transition.
     */
    public Flow createFlow(String sourceId, String targetId) {
        return createFlow(sourceId, targetId, 1);
    }

    /**
     * Add a given flow directly without any checks.
     * @param key the EdgeKey of the flow
     * @param f the flow to add
     * @return the flow
     */
    private Flow addFlow(EdgeKey key, Flow f) {
        String targetId = key.getTargetId();
        String sourceId = key.getSourceId();
        this.presetEdges.get(targetId).put(key, f);
        this.postsetEdges.get(sourceId).put(key, f);
        this.numFlows++;
        //update pre- and postsets
        Set<Node> preNodes = presetNodes.get(targetId);
        if (preNodes != null) {
            preNodes.add(this.getNode(sourceId));
        }
        Set<Node> postNodes = postsetNodes.get(sourceId);
        if (postNodes != null) {
            postNodes.add(this.getNode(targetId));
        }
        invokeListeners();
        return f;
    }

    /**
     * Creates a new flow in this petri net with the given sourceId, targetId and weight.
     * @param sourceId the id of the source node.
     * @param targetId the id of the target node.
     * @param weight   the weight of the new created flow.
     * @return a reference object to the created flow.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NoSuchNodeException      thrown if one of the ids does not match a node in this petri net.
     * @throws FlowExistsException      thrown if a flow with the same source and target already exists in this
     *                                  petri net.
     * @throws IllegalFlowException     thrown if argument don't correspond to a place and a transition.
     */
    public Flow createFlow(String sourceId, String targetId, int weight) {
        if (sourceId == null) {
            throw new IllegalArgumentException("sourceId == null");
        }
        if (targetId == null) {
            throw new IllegalArgumentException("targetId == null");
        }
        if (weight < 0) {
            throw new IllegalArgumentException("weight < 0");
        }

        final EdgeKey key = this.createEdgeKey(sourceId, targetId);
        // createEdgeKey() makes sure the node exists
        if (this.postsetEdges.get(sourceId).containsKey(key)) {
            throw new FlowExistsException(this, key);
        }
        boolean hasPlace = places.containsKey(sourceId) || places.containsKey(targetId);
        boolean hasTransition = transitions.containsKey(sourceId) || transitions.containsKey(targetId);
        if (!hasPlace || !hasTransition) {
            throw new IllegalFlowException(this, key);
        }
        Flow f = new Flow(this, getNode(sourceId), getNode(targetId), weight);
        if (weight > 0) {
            addFlow(key, f);
        }
        return f;
    }

    /**
     * Creates a new flow in this petri net with the given source, target and weight.
     * @param source the source node.
     * @param target the target node.
     * @param weight the weight of the new created flow.
     * @return a reference object to the created flow.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NoSuchNodeException      thrown if one of the ids does not match a node in this petri net.
     * @throws FlowExistsException      thrown if a flow with the same source and target already exists in this
     *                                  petri net.
     * @throws IllegalFlowException     thrown if argument don't correspond to a place and a transition.
     */
    public Flow createFlow(Node source, Node target, int weight) {
        if (source == null) {
            throw new IllegalArgumentException("source == null");
        }
        if (target == null) {
            throw new IllegalArgumentException("target == null");
        }
        return createFlow(source.getId(), target.getId(), weight);
    }

    /**
     * Creates a new flow in this petri net with the given source, target and weight 1.
     * @param source the source node.
     * @param target the target node.
     * @return a reference object to the created flow.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NoSuchNodeException      thrown if one of the ids does not match a node in this petri net.
     * @throws FlowExistsException      thrown if a flow with the same source and target already exists in this
     *                                  petri net.
     * @throws IllegalFlowException     thrown if argument don't correspond to a place and a transition.
     */
    public Flow createFlow(Node source, Node target) {
        return createFlow(source, target, 1);
    }

    /**
     * Creates a new flow in this petri net by copying the values from an existing arc. Also copies the references
     * of the extensions of the given flow.
     * @param flow the template flow.
     * @return a reference object to the created flow.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NoSuchNodeException      thrown if one of the ids does not match a node in this petri net.
     * @throws FlowExistsException      thrown if a flow with the same source and target already exists in this
     *                                  petri net.
     * @throws IllegalFlowException     thrown if argument don't correspond to a place and a transition.
     */
    public Flow createFlow(Flow flow) {
        if (flow == null) {
            throw new IllegalArgumentException("flow == null");
        }
        Flow f = createFlow(flow.getSourceId(), flow.getTargetId(), flow.getWeight());
        f.copyExtensions(flow);
        return f;
    }

    /**
     * Add a given place directly without any checks.
     * @param id the id of the place
     * @param p the place to add
     * @return the place
     */
    private Place addPlace(String id, Place p) {
        this.places.put(id, p);
        this.nodes.put(id, p);
        this.placesList = new ArrayList<>(this.placesList);
        this.placesList.add(p);
        // update pre- and postsets
        presetNodes.put(id, new HashSet<Node>());
        postsetNodes.put(id, new HashSet<Node>());
        presetEdges.put(id, new HashMap<EdgeKey, Flow>());
        postsetEdges.put(id, new HashMap<EdgeKey, Flow>());
        invokeListeners();
        return p;
    }

    /**
     * Creates a new place to the petri net with the given id.
     * @param id the id of the new place.
     * @return a reference object to the created place.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NodeExistsException      thrown if an other node with the same id already exists in the petri net.
     */
    public Place createPlace(String id) {
        if (id == null) {
            throw new IllegalArgumentException("id == null");
        }

        if (!this.nodes.containsKey(id)) {
            return addPlace(id, new Place(this, id));
        } else {
            throw new NodeExistsException(this, id);
        }
    }

    /**
     * Creates a new place with an autogenerated id to the petri net.
     * @return a reference object to the created place.
     */
    public Place createPlace() {
        while (nodes.containsKey("p" + nextPlaceId)) {
            ++nextPlaceId;
        }
        Place p = createPlace("p" + nextPlaceId);
        ++nextPlaceId;
        return p;
    }

    /**
     * Creates a new place to the petri net by copying the values from a existing place. It also copies the
     * references of the extension of the given place.
     * @param p the template place.
     * @return a reference object to the created place.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NodeExistsException      thrown if an other node with the same id already exists in the petri net.
     */
    public Place createPlace(Place p) {
        if (p == null) {
            throw new IllegalArgumentException("p == null");
        }
        Place place = createPlace(p.getId());
        place.copyExtensions(p);
        return place;
    }

    /**
     * Creates a few new places in this petri net by copying the values from the other places. It also copies the
     * references of the extension of the given places.
     * @param placeList a list of places to get the id and extensions from.
     * @return a list of the newly created places.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NodeExistsException      thrown if an other node with the same id already exists in the petri net.
     */
    public Place[] createPlaces(Place... placeList) {
        if (placeList == null) {
            throw new IllegalArgumentException("places == null");
        }
        Place[] out = new Place[placeList.length];
        for (int i = 0; i < placeList.length; i++) {
            out[i] = this.createPlace(placeList[i]);
        }
        return out;
    }

    /**
     * Creates a few new places in this petri net with the given ids.
     * @param idList a list of ids.
     * @return a list of the newly created places.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NodeExistsException      thrown if an other node with the same id already exists in the petri net.
     */
    public Place[] createPlaces(String... idList) {
        if (idList == null) {
            throw new IllegalArgumentException("places == null");
        }
        Place[] out = new Place[idList.length];
        for (int i = 0; i < idList.length; i++) {
            out[i] = this.createPlace(idList[i]);
        }
        return out;
    }

    /**
     * Creates #count new places in this petri net with auto generated ids.
     * @param count how many places should be created.
     * @return a list of the newly created places.
     */
    public Place[] createPlaces(int count) {
        Place[] out = new Place[count];
        for (int i = 0; i < count; i++) {
            out[i] = this.createPlace();
        }
        return out;
    }

    /**
     * Creates a new transition to the petri net with the given id. The label of this transition will be it's id.
     * @param id the id of the new transition.
     * @return a reference object to the created transition.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NodeExistsException      thrown if an other node with the same id already exists in the petri net.
     */
    public Transition createTransition(String id) {
        return createTransition(id, id);
    }

    /**
     * Add a given transition directly without any checks.
     * @param id the id of the transition
     * @param t the transition to add
     * @return the transition
     */
    private Transition addTransition(String id, Transition t) {
        this.transitions.put(id, t);
        this.nodes.put(id, t);
        // update pre- and postsets
        presetNodes.put(id, new HashSet<Node>());
        postsetNodes.put(id, new HashSet<Node>());
        presetEdges.put(id, new HashMap<EdgeKey, Flow>());
        postsetEdges.put(id, new HashMap<EdgeKey, Flow>());
        invokeListeners();
        return t;
    }

    /**
     * Creates a new transition to the petri net with the given id and label.
     * @param id    the id of the new transition.
     * @param label the label of the new transition.
     * @return a reference object to the created transition.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NodeExistsException      thrown if an other node with the same id already exists in the petri net.
     */
    public Transition createTransition(String id, String label) {
        if (label == null) {
            throw new IllegalArgumentException("label == null");
        }
        if (id == null) {
            throw new IllegalArgumentException("id == null");
        }

        if (!this.nodes.containsKey(id)) {
            final Transition t = new Transition(this, id);
            t.label = label;
            return addTransition(id, t);
        } else {
            throw new NodeExistsException(this, id);
        }
    }

    /**
     * Creates a new transition with an autogenerated id and the same as label to the petri net.
     * @return a reference object to the created transition.
     */
    public Transition createTransition() {
        while (nodes.containsKey("t" + nextTransitionId)) {
            ++nextTransitionId;
        }
        Transition t = createTransition("t" + nextTransitionId);
        ++nextTransitionId;
        return t;
    }

    /**
     * Creates a new transition to the petri net by copying the values from a existing place. It also copies the
     * references of the extension of the given transition.
     * @param t the template transition.
     * @return a reference object to the created transition.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NodeExistsException      thrown if an other node with the same id already exists in the petri net.
     */
    public Transition createTransition(Transition t) {
        if (t == null) {
            throw new IllegalArgumentException("t == null");
        }
        Transition trans = createTransition(t.getId(), t.getLabel());
        trans.copyExtensions(t);
        return trans;
    }

    /**
     * Creates a few new transitions in this petri net by copying the values from the other transitions. It also
     * copies the references of the extension of the given transitions.
     * @param transitionList a list of transitions to get the id, label and extensions from.
     * @return a list of the newly created transitions.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NodeExistsException      thrown if an other node with the same id already exists in the petri net.
     */
    public Transition[] createTransitions(Transition... transitionList) {
        if (transitionList == null) {
            throw new IllegalArgumentException("transitions == null");
        }
        Transition[] out = new Transition[transitionList.length];
        for (int i = 0; i < transitionList.length; i++) {
            out[i] = this.createTransition(transitionList[i]);
        }
        return out;
    }

    /**
     * Creates a few new transitions in this petri net with the given ids.
     * @param idList a list of ids.
     * @return a list of the newly created transitions.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NodeExistsException      thrown if an other node with the same id already exists in the petri net.
     */
    public Transition[] createTransitions(String... idList) {
        if (idList == null) {
            throw new IllegalArgumentException("transitions == null");
        }
        Transition[] out = new Transition[idList.length];
        for (int i = 0; i < idList.length; i++) {
            out[i] = this.createTransition(idList[i]);
        }
        return out;
    }

    /**
     * Creates #count new transitions in this petri net with auto generated ids and the same as label.
     * @param count how many transitions should be created.
     * @return a list of the newly created transitions.
     */
    public Transition[] createTransitions(int count) {
        Transition[] out = new Transition[count];
        for (int i = 0; i < count; i++) {
            out[i] = this.createTransition();
        }
        return out;
    }

    /**
     * Removes a flow with the given source and target id from this petri net.
     * @param sourceId the id of the source node of the flow to remove.
     * @param targetId the id of the target node of the flow to remove.
     * @throws NoSuchEdgeException      thrown if there is no flow with the given target and source in this petri
     *                                  net.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NoSuchNodeException      thrown if one of the ids does not match a node in this petri net.
     */
    public void removeFlow(String sourceId, String targetId) {
        if (sourceId == null) {
            throw new IllegalArgumentException("sourceId == null");
        }
        if (targetId == null) {
            throw new IllegalArgumentException("targetId == null");
        }
        // createEdgeKey() makes sure the node exists
        final EdgeKey key = this.createEdgeKey(sourceId, targetId);
        Flow f = postsetEdges.get(sourceId).get(key);
        if (f == null) {
            throw new NoSuchEdgeException(this, sourceId, targetId);
        }
        // update pre- and postsets
        Set<Node> preNodes = presetNodes.get(targetId);
        if (preNodes != null) {
            preNodes.remove(nodes.get(sourceId));
        }
        Set<Node> postNodes = postsetNodes.get(sourceId);
        if (postNodes != null) {
            postNodes.remove(nodes.get(targetId));
        }
        Flow old;
        old = presetEdges.get(targetId).remove(key);
        assert old == f;
        old = postsetEdges.get(sourceId).remove(key);
        assert old == f;
        this.numFlows--;
        invokeListeners();
    }

    /**
     * Removes a flow with the given source and target from this petri net.
     * @param source the source node of the flow to remove.
     * @param target the target node of the flow to remove.
     * @throws NoSuchEdgeException      thrown if there is no flow with the given target and source in this petri
     *                                  net.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NoSuchNodeException      thrown if the given nodes do not belong to this petri net.
     */
    public void removeFlow(Node source, Node target) {
        if (source == null) {
            throw new IllegalArgumentException("source == null");
        }
        if (target == null) {
            throw new IllegalArgumentException("target == null");
        }
        removeFlow(source.getId(), target.getId());
    }

    /**
     * * Removes a flow from this petri net.
     * @param flow the flow to remove.
     * @throws NoSuchEdgeException      thrown if this flow does not belong to this petri net.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NoSuchNodeException      thrown if the belonging nodes do not match in this petri net.
     */
    public void removeFlow(Flow flow) {
        if (flow == null) {
            throw new IllegalArgumentException("flow == null");
        }
        removeFlow(flow.getSourceId(), flow.getTargetId());
    }

    /**
     * Removes a node with the given id from this petri net. It also removes all the flows that lead to/from the
     * node.
     * @param id the id of the node to remove.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NoSuchNodeException      thrown if the given node do not belong to this petri net.
     */
    public void removeNode(String id) {
        if (id == null) {
            throw new IllegalArgumentException("id == null");
        }
        if (this.transitions.containsKey(id)) {
            removeTransition(id);
        } else if (this.places.containsKey(id)) {
            removePlace(id);
        } else {
            throw new NoSuchNodeException(this, id);
        }
    }

    /**
     * Removes a node from this petri net. It also removes all the flows that lead to/from the node.
     * @param node the node to remove.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NoSuchNodeException      thrown if the given node do not belong to this petri net.
     */
    public void removeNode(Node node) {
        if (node == null) {
            throw new IllegalArgumentException("node == null");
        }
        removeNode(node.getId());
    }

    /**
     * Removes a node from this petri net. It also removes all the flows that lead to/from the node.
     * @param id the id of the node to remove.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NoSuchNodeException      thrown if the given node do not belong to this petri net.
     */
    private void rmNode(String id) {
        if (id == null) {
            throw new IllegalArgumentException("id == null");
        }
        Node n = this.nodes.get(id);
        if (n == null) {
            throw new NoSuchNodeException(this, id);
        }

        // update flows
        Collection<Flow> pe = new HashSet<>(getPresetEdges(id));
        for (Flow f : pe) {
            this.removeFlow(f);
        }
        pe = new HashSet<>(getPostsetEdges(id));
        for (Flow f : pe) {
            this.removeFlow(f);
        }

        // update pre- and postsets
        presetNodes.remove(id);
        postsetNodes.remove(id);
        presetEdges.remove(id);
        postsetEdges.remove(id);
        this.nodes.remove(id);
    }

    /**
     * Removes a place from this petri net. It also removes all the flows that lead to/from the place.
     * @param id the id of the place to remove.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NoSuchNodeException      thrown if the given place do not belong to this petri net.
     */
    public void removePlace(String id) {
        if (id == null) {
            throw new IllegalArgumentException("id == null");
        }
        if (!this.places.containsKey(id)) {
            throw new NoSuchNodeException(this, id);
        }
        this.placesList = new ArrayList<>(this.placesList);
        this.placesList.remove(places.get(id));
        rmNode(id);
        places.remove(id);
        invokeListeners();
    }

    /**
     * Removes a place from this petri net. It also removes all the flows that lead to/from the place.
     * @param place the place to remove.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NoSuchNodeException      thrown if the given place do not belong to this petri net.
     */
    public void removePlace(Place place) {
        if (place == null) {
            throw new IllegalArgumentException("place == null");
        }
        removePlace(place.getId());
    }

    /**
     * Removes a transition from this petri net. It also removes all the flows that lead to/from the transition.
     * @param id the id of the transition to remove.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NoSuchNodeException      thrown if the given transition do not belong to this petri net.
     */
    public void removeTransition(String id) {
        if (id == null) {
            throw new IllegalArgumentException("id == null");
        }
        if (!this.transitions.containsKey(id)) {
            throw new NoSuchNodeException(this, id);
        }
        rmNode(id);
        this.transitions.remove(id);
        invokeListeners();
    }

    /**
     * Removes a transition from this petri net. It also removes all the flows that lead to/from the transition.
     * @param trans the transition to remove.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NoSuchNodeException      thrown if the given transition do not belong to this petri net.
     */
    public void removeTransition(Transition trans) {
        if (trans == null) {
            throw new IllegalArgumentException("trans == null");
        }
        removeTransition(trans.getId());
    }

    /**
     * Returns a flow with the given source and target id.
     * @param sourceId the id of the source node of the flow.
     * @param targetId the id of the target node of the flow.
     * @return a reference to the flow with the given source and target.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NoSuchNodeException      thrown if one of the given nodes do not belong to this petri net.
     * @throws NoSuchEdgeException      thrown if there is no flow between the given nodes in this petri net.
     */
    public Flow getFlow(String sourceId, String targetId) {
        if (sourceId == null) {
            throw new IllegalArgumentException("sourceId == null");
        }
        if (targetId == null) {
            throw new IllegalArgumentException("targetId == null");
        }
        // createEdgeKey() makes sure the node exists
        EdgeKey key = this.createEdgeKey(sourceId, targetId);
        Flow f = this.postsetEdges.get(sourceId).get(key);
        if (f == null) {
            throw new NoSuchEdgeException(this, sourceId, targetId);
        }
        return f;
    }

    /**
     * Returns a flow with the given source and target.
     * @param source the source node of the flow.
     * @param target the target node of the flow.
     * @return a reference to the flow with the given source and target.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NoSuchNodeException      thrown if one of the given nodes do not belong to this petri net.
     * @throws NoSuchEdgeException      thrown if there is no flow between the given nodes in this petri net.
     */
    public Flow getFlow(Node source, Node target) {
        if (source == null) {
            throw new IllegalArgumentException("source == null");
        }
        if (target == null) {
            throw new IllegalArgumentException("target == null");
        }
        return getFlow(source.getId(), target.getId());
    }

    /**
     * Returns the place with the given id.
     * @param id the id of the place to get.
     * @return a reference to the place.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NoSuchNodeException      thrown if the given id do not belong to this petri net.
     */
    public Place getPlace(String id) {
        if (id == null) {
            throw new IllegalArgumentException("id == null");
        }
        Place p = places.get(id);
        if (p == null) {
            throw new NoSuchNodeException(this, id);
        }
        return p;
    }

    /**
     * Returns the transition with the given id.
     * @param id the id of the transition to get.
     * @return a reference to the transition.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NoSuchNodeException      thrown if the given id do not belong to this petri net.
     */
    public Transition getTransition(String id) {
        if (id == null) {
            throw new IllegalArgumentException("id == null");
        }
        Transition t = transitions.get(id);
        if (t == null) {
            throw new NoSuchNodeException(this, id);
        }
        return t;
    }

    /**
     * Checks if this petri net contains a node with the given id.
     * @param id the id of the node.
     * @return true if the node exists in this petri net.
     * @throws IllegalArgumentException thrown if passing a null argument.
     */
    public boolean containsNode(String id) {
        if (id == null) {
            throw new IllegalArgumentException("id == null");
        }
        return nodes.containsKey(id);
    }

    /**
     * Checks if this petri net contains a node.
     * @param n the node.
     * @return true if the node exists in this petri net.
     * @throws IllegalArgumentException thrown if passing a null argument.
     */
    public boolean containsNode(Node n) {
        if (n == null) {
            throw new IllegalArgumentException("id == null");
        }
        return containsNode(n.getId());
    }

    /**
     * Checks if this petri net contains a place with the given id.
     * @param id the id of the place.
     * @return true if the place exists in this petri net.
     * @throws IllegalArgumentException thrown if passing a null argument.
     */
    public boolean containsPlace(String id) {
        if (id == null) {
            throw new IllegalArgumentException("id == null");
        }
        return places.containsKey(id);
    }

    /**
     * Checks if this petri net contains a place.
     * @param p the place.
     * @return true if the place exists in this petri net.
     * @throws IllegalArgumentException thrown if passing a null argument.
     */
    public boolean containsPlace(Place p) {
        if (p == null) {
            throw new IllegalArgumentException("p == null");
        }
        return containsPlace(p.getId());
    }

    /**
     * Checks if this petri net contains a transition with the given id.
     * @param id the id of the transition.
     * @return true if the transition exists in this petri net.
     * @throws IllegalArgumentException thrown if passing a null argument.
     */
    public boolean containsTransition(String id) {
        if (id == null) {
            throw new IllegalArgumentException("id == null");
        }
        return transitions.containsKey(id);
    }

    /**
     * Checks if this petri net contains a transition.
     * @param t the transition.
     * @return true if the transition exists in this petri net.
     * @throws IllegalArgumentException thrown if passing a null argument.
     */
    public boolean containsTransition(Transition t) {
        if (t == null) {
            throw new IllegalArgumentException("t == null");
        }
        return containsTransition(t.getId());
    }

    /**
     * Gets a view of the places of this petri net.
     * @return a view of the places of this petri net.
     */
    public Set<Place> getPlaces() {
        // This really behaves like a Set, but the Map doesn't know that its values are unique.
        return new CollectionToUnmodifiableSetAdapter<>(this.places.values());
    }

    /**
     * Gets a view of the transitions of this petri net.
     * @return a view of the transitions of this petri net.
     */
    public Set<Transition> getTransitions() {
        // This really behaves like a Set, but the Map doesn't know that its values are unique.
        return new CollectionToUnmodifiableSetAdapter<>(this.transitions.values());
    }

    /**
     * Sets the initial marking for this petri net.
     * @param m the marking to set as initial.
     * @throws IllegalArgumentException thrown if the given marking do not belong to this petri net.
     */
    public void setInitialMarking(Marking m) {
        if (m.getNet() != this) {
            throw new IllegalArgumentException("Marking do not belong to the" + " net " + getName());
        }
        this.initialMarking = m;
        invokeListeners();
    }

    /**
     * Returns a copy of the initial marking of this petri net.
     * @return the copy of the initial marking of this petri net.
     */
    public Marking getInitialMarking() {
        return new Marking(initialMarking);
    }

    /**
     * Returns a copy of the initial marking of this petri net.
     * @return the copy of the initial marking of this petri net.
     * @deprecated Use {@link #getInitialMarking()} instead, because the function name is better.
     */
    @Deprecated
    public Marking getInitialMarkingCopy() {
        return getInitialMarking();
    }

    /**
     * Adds a final marking to this petri net.
     * @param m the marking to add as final marking.
     * @return true on successfully added.
     * @throws IllegalArgumentException thrown if the given marking do not belong to this petri net.
     */
    public boolean addFinalMarking(Marking m) {
        if (m.getNet() != this) {
            throw new IllegalArgumentException("Marking do not belong to the" + " net " + getName());
        }
        return this.finalMarkings.add(m);
    }

    /**
     * Gets a view of the final markings of this petri net.
     * @return a view of the final markings of this petri net.
     */
    public Set<Marking> getFinalMarkings() {
        return Collections.unmodifiableSet(this.finalMarkings);
    }

    /**
     * Get a list of all places. This list is never modified and is instead replaced every time a place is created
     * or removed. This is used by the {@link Marking} class.
     * @return A list with all places of the net.
     */
    List<Place> getPlacesList() {
        return placesList;
    }

    /**
     * Creates an edge key to find or save a flow by it's primary key, that mean it's sourceId and targetId.
     * @param sourceId the id of the source node.
     * @param targetId the id of the target node.
     * @return the edge key.
     * @throws NoSuchNodeException thrown if one of the nodes does not exist in this petri net.
     */
    private EdgeKey createEdgeKey(String sourceId, String targetId) {
        final Node s = this.getNode(sourceId);
        if (s == null) {
            throw new NoSuchNodeException(this, sourceId);
        }
        final Node t = this.getNode(targetId);
        if (t == null) {
            throw new NoSuchNodeException(this, targetId);
        }

        return new EdgeKey(sourceId, targetId);
    }

    /**
     * Returns the initial token count of a place given by it's id.
     * @param id the id of the place.
     * @return the token count of the place.
     */
    Token getInitialToken(String id) {
        return initialMarking.getToken(id);
    }

    /**
     * Changes the initial marking of this petri net by setting the token count of a place given by it's id.
     * @param id the id of the place.
     * @param t  the token count to set.
     */
    void setInitialToken(String id, Token t) {
        initialMarking = initialMarking.setTokenCount(id, t);
        invokeListeners();
    }

    /**
     * Sets the weight of a flow with the given source and target id. Is the weight less then 1 the flow will be
     * removed from this petri net.
     * @param sourceId the id of the source node.
     * @param targetId the id of the target node.
     * @param w        the weight of the flow.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NoSuchNodeException      thrown if one of the nodes does not exist in this petri net.
     * @throws NoSuchEdgeException      thrown if there is no flow between the given nodes in this petri net.
     */
    void setFlowWeight(String sourceId, String targetId, int w) {
        if (sourceId == null) {
            throw new IllegalArgumentException("sourceId == null");
        }
        if (targetId == null) {
            throw new IllegalArgumentException("targetId == null");
        }
        // createEdgeKey() makes sure the node exists
        EdgeKey key = createEdgeKey(sourceId, targetId);
        Flow f = postsetEdges.get(sourceId).get(key);
        if (f == null) {
            throw new NoSuchEdgeException(this, sourceId, targetId);
        }
        if (w < 1) {
            this.removeFlow(sourceId, targetId);
        } else {
            f.weight = w;
            invokeListeners();
        }
    }

    /**
     * Returns the place of a flow with the given source and target id.
     * @param sourceId the id of the source node of the flow.
     * @param targetId the id of the target node of the flow.
     * @return the place which id is equal to the sourceId or targetId.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NoSuchNodeException      thrown if one of the nodes does not exist in this petri net.
     */
    Place getFlowPlace(String sourceId, String targetId) {
        if (sourceId == null) {
            throw new IllegalArgumentException("sourceId == null");
        }
        if (targetId == null) {
            throw new IllegalArgumentException("targetId == null");
        }
        Place p = places.get(sourceId);
        if (p != null) {
            return p;
        } else if (places.containsKey(targetId)) {
            return places.get(targetId);
        } else {
            throw new NoSuchNodeException(this, sourceId);
        }
    }

    /**
     * Returns the transition of a flow with the given source and target id.
     * @param sourceId the id of the source node of the flow.
     * @param targetId the id of the target node of the flow.
     * @return the transition which id is equal to the sourceId or targetId.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NoSuchNodeException      thrown if one of the nodes does not exist in this petri net.
     */
    Transition getFlowTransition(String sourceId, String targetId) {
        if (sourceId == null) {
            throw new IllegalArgumentException("sourceId == null");
        }
        if (targetId == null) {
            throw new IllegalArgumentException("targetId == null");
        }
        Transition t = transitions.get(sourceId);
        if (t != null) {
            return t;
        } else if (transitions.containsKey(targetId)) {
            return transitions.get(targetId);
        } else {
            throw new NoSuchNodeException(this, sourceId);
        }
    }

    /**
     * Sets the label of a transition with the given id.
     * @param id    the id of the transition.
     * @param label the label.
     * @throws IllegalArgumentException thrown if passing a null argument.
     * @throws NoSuchNodeException      thrown if the transition does not exist in this petri net.
     */
    void setTransitionLabel(String id, String label) {
        if (id == null) {
            throw new IllegalArgumentException("id == null");
        }
        if (label == null) {
            throw new IllegalArgumentException("label == null");
        }
        Transition t = transitions.get(id);
        if (t == null) {
            throw new NoSuchNodeException(this, id);
        }
        t.label = label;
        invokeListeners();
    }

    /**
     * Checks if a transition can be fired under a given marking.
     * @param id the id of the transition.
     * @param m  the marking.
     * @return true if the transition can be fired under the given marking.
     */
    boolean getTransitionIsFireable(String id, Marking m) {
        for (Flow f : this.getPresetEdges(id)) {
            if (m.getToken(f.getPlace()).compareTo(Token.valueOf(f.getWeight())) < 0) {
                return false;
            }
        }
        return true;
    }

    /**
     * Fires a transition and returns the resulting marking.
     * @param id the id of the transition.
     * @param m  the marking.
     * @return the resulting marking.
     * @throws TransitionFireException thrown if the transition is not fireable under the given marking.
     */
    Marking fireTransition(String id, Marking m) {
        if (getTransitionIsFireable(id, m)) {
            for (Flow f : this.getPresetEdges(id)) {
                m = m.addTokenCount(f.getPlace(), -f.getWeight());
            }
            for (Flow f : this.getPostsetEdges(id)) {
                m = m.addTokenCount(f.getPlace(), +f.getWeight());
            }
            return m;
        } else {
            throw new TransitionFireException(
                    "transition '" + id + "' is not fireable in marking '" + m.toString() + "'.");
        }
    }

    /**
     * Calculates and returns the incidencematrix of this petri net.
     * @return the incidencematrix of this petri net.
     */
    public int[][] getIncidenceMatrix() {
        int[][] incidenceMatrix = new int[this.places.size()][this.transitions.size()];
        for (Flow a : getEdges()) {
            Transition t = a.getTransition();
            final int row = this.indexOfPlace(a.getPlace());
            final int col = this.indexOfTransition(t);
            if ((row >= 0) && (col >= 0)) {
                incidenceMatrix[row][col] += (a.getSourceId().equals(t.getId())) ? a.getWeight() : -a.getWeight();
            }
        }
        return incidenceMatrix;
    }

    /**
     * Returns the index of a place in the lexically ordered list of places.
     * @param p the place.
     * @return the index of the place.
     */
    private int indexOfPlace(Place p) {
        final Iterator<Place> iter = this.places.values().iterator();
        for (int i = 0; iter.hasNext(); ++i) {
            if (Objects.equals(iter.next(), p)) {
                return i;
            }
        }
        return -1;
    }

    /**
     * Returns the index of a transition in the lexically ordered list of transitions.
     * @param t the transition.
     * @return the index of the transition.
     */
    private int indexOfTransition(Transition t) {
        final Iterator<Transition> iter = this.transitions.values().iterator();
        for (int i = 0; iter.hasNext(); ++i) {
            if (Objects.equals(iter.next(), t)) {
                return i;
            }
        }
        return -1;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String getName() {
        return this.name;
    }

    /**
     * Retrieves the node with the given id.
     * @param id the id of the node.
     * @return a reference object of a node identified by the id.
     * @throws IllegalArgumentException thrown if null is passed to the method.
     * @throws NoSuchNodeException      thrown if no node with the id exists in this petri net.
     */
    @Override
    public Node getNode(String id) {
        if (id == null) {
            throw new IllegalArgumentException("id == null");
        }
        Node node = nodes.get(id);
        if (node != null) {
            return node;
        } else {
            throw new NoSuchNodeException(this, id);
        }
    }

    @Override
    public Set<Flow> getEdges() {
        return new AbstractSet<Flow>() {
            @Override
            public int size() {
                return PetriNet.this.numFlows;
            }

            @Override
            public Iterator<Flow> iterator() {
                return new Iterator<Flow>() {
                    private Iterator<Map<EdgeKey, Flow>> postsetIter = PetriNet.this.postsetEdges.values()
                            .iterator();
                    private Iterator<Flow> flowIter = emptyIterator();

                    @Override
                    public boolean hasNext() {
                        while (!flowIter.hasNext() && postsetIter.hasNext())
                            flowIter = postsetIter.next().values().iterator();
                        return flowIter.hasNext();
                    }

                    @Override
                    public Flow next() {
                        // Update flowIter, if needed
                        hasNext();
                        return flowIter.next();
                    }

                    @Override
                    public void remove() {
                        throw new UnsupportedOperationException();
                    }
                };
            }
        };
    }

    @Override
    public Set<Node> getNodes() {
        // This really behaves like a Set, but the Map doesn't know that its values are unique.
        return new CollectionToUnmodifiableSetAdapter<>(this.nodes.values());
    }

    /**
     * Calculates the preset nodes of a node with the given id.
     * @param id - the id of the node
     * @return the preset nodes of the given node.
     */
    private Set<Node> calcPresetNodes(String id) {
        Set<Node> pre = presetNodes.get(id);
        if (pre == null) {
            pre = new HashSet<>();
            for (Flow a : this.getPresetEdges(id)) {
                pre.add(a.getSource());
            }
            presetNodes.put(id, pre);
        }
        return pre;
    }

    /**
     * Calculates the postset nodes of a node with the given id.
     * @param id - the id of the node
     * @return the postset nodes of the given node.
     */
    private Set<Node> calcPostsetNodes(String id) {
        Set<Node> post = postsetNodes.get(id);
        if (post == null) {
            post = new HashSet<>();
            for (Flow a : this.getPostsetEdges(id)) {
                post.add(a.getTarget());
            }
            postsetNodes.put(id, post);
        }
        return post;
    }

    /**
     * Retrieves a view of all nodes which have an outgoing edge to the node identified by the id.
     * @param id the id of a node.
     * @return a unmodifiable set of nodes.
     * @throws IllegalArgumentException thrown if null is passed to the method.
     * @throws NoSuchNodeException      thrown if no node with the given id exists in this graph.
     */
    @Override
    public Set<Node> getPresetNodes(String id) {
        if (id == null) {
            throw new IllegalArgumentException("id == null");
        }
        if (!nodes.containsKey(id)) {
            throw new NoSuchNodeException(this, id);
        }
        return Collections.unmodifiableSet(calcPresetNodes(id));
    }

    /**
     * Retrieves a view of all nodes which have an incoming edge from the node with the given id.
     * @param id The id of a node.
     * @return A unmodifiable set of nodes.
     * @throws IllegalArgumentException thrown if null is passed to the method.
     * @throws NoSuchNodeException      thrown if no node with the given id exists in this graph.
     */
    @Override
    public Set<Node> getPostsetNodes(String id) {
        if (id == null) {
            throw new IllegalArgumentException("id == null");
        }
        if (!nodes.containsKey(id)) {
            throw new NoSuchNodeException(this, id);
        }
        return Collections.unmodifiableSet(calcPostsetNodes(id));
    }

    /**
     * Retrieves a view of all edges targeting the node with the given id.
     * @param id The id of a node.
     * @return A unmodifiable set of flows.
     * @throws IllegalArgumentException thrown if null is passed to the method.
     * @throws NoSuchNodeException      thrown if no node with the given id exists in this graph.
     */
    @Override
    public Set<Flow> getPresetEdges(String id) {
        if (id == null) {
            throw new IllegalArgumentException("id == null");
        }
        if (!nodes.containsKey(id)) {
            throw new NoSuchNodeException(this, id);
        }

        return Collections.unmodifiableSet(new LinkedHashSet<>(presetEdges.get(id).values()));
    }

    /**
     * Retrieves a view of all edges beginning in the node with the given id.
     * @param id The id of a node.
     * @return A unmodifiable set of flows.
     * @throws IllegalArgumentException thrown if null is passed to the method.
     * @throws NoSuchNodeException      thrown if no node with the given id exists in this graph.
     */
    @Override
    public Set<Flow> getPostsetEdges(String id) {
        if (id == null) {
            throw new IllegalArgumentException("id == null");
        }
        if (!nodes.containsKey(id)) {
            throw new NoSuchNodeException(this, id);
        }
        return Collections.unmodifiableSet(new LinkedHashSet<>(postsetEdges.get(id).values()));
    }

    /**
     * Retrieves a view of all edges beginning in the given node.
     * @param node The node.
     * @return A unmodifiable set of flows.
     * @throws IllegalArgumentException thrown if null is passed to the method.
     * @throws NoSuchNodeException      thrown if no node with the given id exists in this graph.
     * @throws StructureException       thrown if the given node does not belong to this graph.
     */
    @Override
    public Set<Flow> getPostsetEdges(Node node) {
        if (node == null) {
            throw new IllegalArgumentException("node == null");
        }
        if (this != node.getGraph()) {
            throw new StructureException(
                    "node'" + node.getId() + "' does not belong to the net '" + this.getName() + "'.");
        }
        return getPostsetEdges(node.getId());
    }

    /**
     * Retrieves a view of all nodes which have an incoming edge from the given node.
     * @param node The node.
     * @return A unmodifiable set of nodes.
     * @throws IllegalArgumentException thrown if null is passed to the method.
     * @throws NoSuchNodeException      thrown if no node with the given id exists in this graph.
     * @throws StructureException       thrown if the given node does not belong to this graph.
     */
    @Override
    public Set<Node> getPostsetNodes(Node node) {
        if (node == null) {
            throw new IllegalArgumentException("node == null");
        }
        if (this != node.getGraph()) {
            throw new StructureException(
                    "node'" + node.getId() + "' does not belong to the net '" + this.getName() + "'.");
        }
        return getPostsetNodes(node.getId());
    }

    /**
     * Retrieves a view of all edges targeting the given node.
     * @param node The node.
     * @return A unmodifiable set of flows.
     * @throws IllegalArgumentException thrown if null is passed to the method.
     * @throws NoSuchNodeException      thrown if no node with the given id exists in this graph.
     * @throws StructureException       thrown if the given node does not belong to this graph.
     */
    @Override
    public Set<Flow> getPresetEdges(Node node) {
        if (node == null) {
            throw new IllegalArgumentException("node == null");
        }
        if (this != node.getGraph()) {
            throw new StructureException(
                    "node'" + node.getId() + "' does not belong to the net '" + this.getName() + "'.");
        }
        return getPresetEdges(node.getId());
    }

    /**
     * Retrieves a view of all nodes which have an outgoing edge to the given node
     * @param node the node.
     * @return a unmodifiable set of nodes.
     * @throws IllegalArgumentException thrown if null is passed to the method.
     * @throws NoSuchNodeException      thrown if no node with the given id exists in this graph.
     * @throws StructureException       thrown if the given node does not belong to this graph.
     */
    @Override
    public Set<Node> getPresetNodes(Node node) {
        if (node == null) {
            throw new IllegalArgumentException("node == null");
        }
        if (this != node.getGraph()) {
            throw new StructureException(
                    "node'" + node.getId() + "' does not belong to the net '" + this.getName() + "'.");
        }
        return getPresetNodes(node.getId());
    }
}

// vim: ft=java:noet:sw=8:sts=8:ts=8:tw=120