/*
 * Copyright 2006 - 2013
 *     Stefan Balev     <stefan.balev@graphstream-project.org>
 *     Julien Baudry    <julien.baudry@graphstream-project.org>
 *     Antoine Dutot    <antoine.dutot@graphstream-project.org>
 *     Yoann Pigné      <yoann.pigne@graphstream-project.org>
 *     Guilhelm Savin   <guilhelm.savin@graphstream-project.org>
 * 
 * This file is part of GraphStream <http://graphstream-project.org>.
 * 
 * GraphStream is a library whose purpose is to handle static or dynamic
 * graph, create them from scratch, file or any source and display them.
 * 
 * This program is free software distributed under the terms of two licenses, the
 * CeCILL-C license that fits European law, and the GNU Lesser General Public
 * License. You can  use, modify and/ or redistribute the software under the terms
 * of the CeCILL-C license as circulated by CEA, CNRS and INRIA at the following
 * URL <http://www.cecill.info> or under the terms of the GNU LGPL 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 Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 * 
 * The fact that you are presently reading this means that you have had
 * knowledge of the CeCILL-C and LGPL licenses and that you accept their terms.
 */
package org.graphstream.graph.implementations;

import java.util.AbstractCollection;
import java.util.Collection;
import java.util.HashSet;
import java.util.Iterator;
import java.util.NoSuchElementException;

import org.graphstream.graph.BreadthFirstIterator;
import org.graphstream.graph.DepthFirstIterator;
import org.graphstream.graph.Edge;
import org.graphstream.graph.Graph;
import org.graphstream.graph.Node;
import org.graphstream.stream.SourceBase;

/**
 * <p>
 * This class provides a basic implementation of {@code Node} interface, to
 * minimize the effort required to implement this interface.
 * </p>
 * 
 * <p>
 * This class implements all the methods of
 * {@link org.graphstream.graph.implementations#AbstractElement} and most of the
 * methods of {@link org.graphstream.graph#Node} (there are "only" ten abstract
 * methods). In addition to these, subclasses must provide implementations for
 * {@link #addEdgeCallback(AbstractEdge)} and
 * {@link #removeEdgeCallback(AbstractEdge)} which are called by the parent
 * graph when an edge incident to this node is added to or removed from the
 * graph. This class has a low memory overhead (one reference as field).
 * </p>
 */
public abstract class AbstractNode extends AbstractElement implements Node {

        // *** Fields ***

        /**
         * The graph to which this node belongs
         */
        protected AbstractGraph graph;

        // *** Constructors

        /**
         * Constructs a new node. This constructor copies the parameters into the
         * corresponding fields
         * 
         * @param graph
         *            The graph to which this node belongs.
         * @param id
         *            Unique identifier of this node.
         */
        protected AbstractNode(AbstractGraph graph, String id) {
                super(id);
                this.graph = graph;
        }

        // *** Inherited from abstract element ***

        @Override
        protected void attributeChanged(AttributeChangeEvent event,
                        String attribute, Object oldValue, Object newValue) {
                graph.listeners.sendAttributeChangedEvent(id,
                                SourceBase.ElementType.NODE, attribute, event, oldValue,
                                newValue);
        }

        /**
         * @return The id of the parent graph
         * @see org.graphstream.graph.implementations.AbstractElement#myGraphId()
         */
        // protected String myGraphId() {
        // return graph.getId();
        // }

        /**
         * This implementation calls the corresponding method of the parent graph
         * 
         * @see org.graphstream.graph.implementations.AbstractElement#newEvent()
         */
        // protected long newEvent() {
        // return graph.newEvent();
        // }

        @Override
        /**
         * This implementation calls the corresponding method of the parent graph
         * 
         * @see org.graphstream.graph.implementations.AbstractElement#nullAttributesAreErrors()
         */
        protected boolean nullAttributesAreErrors() {
                return graph.nullAttributesAreErrors();
        }

        // *** Inherited from Node ***

        /**
         * This implementation returns {@link #graph}.
         * 
         * @see org.graphstream.graph.Node#getGraph()
         */
        public Graph getGraph() {
                return graph;
        }

        public abstract int getDegree();

        public abstract int getInDegree();

        public abstract int getOutDegree();

        // [has|get]Edge[Toward|From|Between](Node|int|String) -> 2 * 3 * 3 = 18
        // methods

        /**
         * This implementation returns {@code true} if {@link #getEdgeToward(Node)}
         * is not {@code null}.
         * 
         * @see org.graphstream.graph.Node#getEdgeToward(org.graphstream.graph.Node)
         */
        public boolean hasEdgeToward(Node node) {
                return getEdgeToward(node) != null;
        }

        /**
         * This implementation returns {@code true} if {@link #getEdgeToward(int)}
         * is not {@code null}.
         * 
         * @see org.graphstream.graph.Node#hasEdgeToward(int)
         */
        public boolean hasEdgeToward(int index) {
                return getEdgeToward(index) != null;
        }

        /**
         * This implementation returns {@code true} if {@link #getEdgeToward(Node)}
         * is not {@code null}.
         * 
         * @see org.graphstream.graph.Node#hasEdgeToward(java.lang.String)
         */
        public boolean hasEdgeToward(String id) {
                return getEdgeToward(id) != null;
        }

        /**
         * This implementation returns {@code true} if {@link #getEdgeFrom(Node)} is
         * not {@code null}.
         * 
         * @see org.graphstream.graph.Node#hasEdgeFrom(org.graphstream.graph.Node)
         */
        public boolean hasEdgeFrom(Node node) {
                return getEdgeFrom(node) != null;
        }

        /**
         * This implementation returns {@code true} if {@link #getEdgeFrom(int)} is
         * not {@code null}.
         * 
         * @see org.graphstream.graph.Node#hasEdgeFrom(int)
         */
        public boolean hasEdgeFrom(int index) {
                return getEdgeFrom(index) != null;
        }

        /**
         * This implementation returns {@code true} if {@link #getEdgeFrom(Node)} is
         * not {@code null}.
         * 
         * @see org.graphstream.graph.Node#hasEdgeFrom(java.lang.String)
         */
        public boolean hasEdgeFrom(String id) {
                return getEdgeFrom(id) != null;
        }

        /**
         * This implementation returns {@code true} if {@link #getEdgeBetween(Node)}
         * is not {@code null}.
         * 
         * @see org.graphstream.graph.Node#hasEdgeBetween(org.graphstream.graph.Node)
         */
        public boolean hasEdgeBetween(Node node) {
                return getEdgeBetween(node) != null;
        }

        /**
         * This implementation returns {@code true} if {@link #getEdgeBetween(int)}
         * is not {@code null}.
         * 
         * @see org.graphstream.graph.Node#hasEdgeBetween(int)
         */
        public boolean hasEdgeBetween(int index) {
                return getEdgeBetween(index) != null;
        }

        /**
         * This implementation returns {@code true} if {@link #getEdgeBetween(Node)}
         * is not {@code null}.
         * 
         * @see org.graphstream.graph.Node#hasEdgeBetween(java.lang.String)
         */
        public boolean hasEdgeBetween(String id) {
                return getEdgeBetween(id) != null;
        }

        public abstract <T extends Edge> T getEdgeToward(Node node);

        /**
         * This implementation uses {@link #getEdgeToward(Node)}
         * 
         * @see org.graphstream.graph.Node#getEdgeToward(int)
         */
        public <T extends Edge> T getEdgeToward(int index) {
                return getEdgeToward(graph.getNode(index));
        }

        /**
         * This implementation uses {@link #getEdgeToward(Node)}
         * 
         * @see org.graphstream.graph.Node#getEdgeToward(java.lang.String)
         */
        public <T extends Edge> T getEdgeToward(String id) {
                return getEdgeToward(graph.getNode(id));
        }

        public abstract <T extends Edge> T getEdgeFrom(Node node);

        /**
         * This implementation uses {@link #getEdgeFrom(Node)}
         * 
         * @see org.graphstream.graph.Node#getEdgeFrom(int)
         */
        public <T extends Edge> T getEdgeFrom(int index) {
                return getEdgeFrom(graph.getNode(index));
        }

        /**
         * This implementation uses {@link #getEdgeFrom(Node)}
         * 
         * @see org.graphstream.graph.Node#getEdgeFrom(java.lang.String)
         */
        public <T extends Edge> T getEdgeFrom(String id) {
                return getEdgeFrom(graph.getNode(id));
        }

        public abstract <T extends Edge> T getEdgeBetween(Node node);

        /**
         * This implementation uses {@link #getEdgeBetween(Node)}
         * 
         * @see org.graphstream.graph.Node#getEdgeBetween(int)
         */
        public <T extends Edge> T getEdgeBetween(int index) {
                return getEdgeBetween(graph.getNode(index));
        }

        /**
         * This implementation uses {@link #getEdgeBetween(Node)}
         * 
         * @see org.graphstream.graph.Node#getEdgeBetween(java.lang.String)
         */
        public <T extends Edge> T getEdgeBetween(String id) {
                return getEdgeBetween(graph.getNode(id));
        }

        // get[_|Entering|Leaving]EdgeIterator

        public abstract <T extends Edge> Iterator<T> getEdgeIterator();

        public abstract <T extends Edge> Iterator<T> getEnteringEdgeIterator();

        public abstract <T extends Edge> Iterator<T> getLeavingEdgeIterator();

        // getEach[_Entering|Leaving]Edge

        /**
         * This implementation uses {@link #getEdgeIterator()}
         * 
         * @see org.graphstream.graph.Node#getEachEdge()
         */
        public <T extends Edge> Iterable<T> getEachEdge() {
                return new Iterable<T>() {
                        public Iterator<T> iterator() {
                                return getEdgeIterator();
                        }
                };
        }

        /**
         * This implementation uses {@link #getEnteringEdgeIterator()}
         * 
         * @see org.graphstream.graph.Node#getEachEnteringEdge()
         */
        public <T extends Edge> Iterable<T> getEachEnteringEdge() {
                return new Iterable<T>() {
                        public Iterator<T> iterator() {
                                return getEnteringEdgeIterator();
                        }
                };
        }

        /**
         * This implementation uses {@link #getLeavingEdgeIterator()}
         * 
         * @see org.graphstream.graph.Node#getEachLeavingEdge()
         */
        public <T extends Edge> Iterable<T> getEachLeavingEdge() {
                return new Iterable<T>() {
                        public Iterator<T> iterator() {
                                return getLeavingEdgeIterator();
                        }
                };
        }

        // get[_|Entering|Leaving]EdgeSet

        /**
         * This implementation uses {@link #getEdgeIterator()} and
         * {@link #getDegree()}
         * 
         * @see org.graphstream.graph.Node#getEdgeSet()
         */
        public <T extends Edge> Collection<T> getEdgeSet() {
                return new AbstractCollection<T>() {
                        @Override
                        public Iterator<T> iterator() {
                                return getEdgeIterator();
                        }

                        @Override
                        public int size() {
                                return getDegree();
                        }
                };
        }

        /**
         * This implementation uses {@link #getEnteringEdgeIterator()} and
         * {@link #geIntDegree()}
         * 
         * @see org.graphstream.graph.Node#getEnteringEdgeSet()
         */
        public <T extends Edge> Collection<T> getEnteringEdgeSet() {
                return new AbstractCollection<T>() {
                        @Override
                        public Iterator<T> iterator() {
                                return getEnteringEdgeIterator();
                        }

                        @Override
                        public int size() {
                                return getInDegree();
                        }
                };
        }

        /**
         * This implementation uses {@link #getLeavingIterator()} and
         * {@link #geOuttDegree()}
         * 
         * @see org.graphstream.graph.Node#getLeavingEdgeSet()
         */
        public <T extends Edge> Collection<T> getLeavingEdgeSet() {
                return new AbstractCollection<T>() {
                        @Override
                        public Iterator<T> iterator() {
                                return getLeavingEdgeIterator();
                        }

                        @Override
                        public int size() {
                                return getOutDegree();
                        }
                };
        }

        /**
         * This implementation uses {@link #getEdgeIterator()}
         * 
         * @see java.lang.Iterable#iterator()
         */
        public Iterator<Edge> iterator() {
                return getEdgeIterator();
        }

        public abstract <T extends Edge> T getEdge(int i);

        public abstract <T extends Edge> T getEnteringEdge(int i);

        public abstract <T extends Edge> T getLeavingEdge(int i);

        /**
         * This implementation uses {@link #getEdgeIterator()} and stores the
         * visited nodes in a set. In this way it ensures that each neighbor will be
         * visited exactly once, even in multi-graph.
         * 
         * @see org.graphstream.graph.Node#getNeighborNodeIterator()
         */
        public <T extends Node> Iterator<T> getNeighborNodeIterator() {
                return new Iterator<T>() {
                        Iterator<Edge> edgeIt = getEdgeIterator();
                        HashSet<T> visited = new HashSet<T>(getDegree());
                        T next;
                        {
                                gotoNext();
                        }

                        private void gotoNext() {
                                while (edgeIt.hasNext()) {
                                        next = edgeIt.next().getOpposite(AbstractNode.this);
                                        if (!visited.contains(next)) {
                                                visited.add(next);
                                                return;
                                        }
                                }
                                next = null;
                        }

                        public boolean hasNext() {
                                return next != null;
                        }

                        public T next() {
                                if (next == null)
                                        throw new NoSuchElementException();
                                T current = next;
                                gotoNext();
                                return current;
                        }

                        public void remove() {
                                throw new UnsupportedOperationException(
                                                "This iterator does not support remove");

                        }

                        // Iterator<Edge> edgeIterator = getEdgeIterator();
                        //
                        // public boolean hasNext() {
                        // return edgeIterator.hasNext();
                        // }
                        //
                        // public T next() {
                        // return edgeIterator.next().getOpposite(AbstractNode.this);
                        // }
                        //
                        // public void remove() {
                        // throw new UnsupportedOperationException(
                        // "This iterator does not support remove");
                        // }
                };
        }

        // breadth- and depth-first iterator

        /**
         * This implementation creates an instance of
         * {@link org.graphstream.graph#BreadthFirstIterator} and returns it.
         * 
         * @see org.graphstream.graph.Node#getBreadthFirstIterator()
         */
        public <T extends Node> Iterator<T> getBreadthFirstIterator() {
                // XXX change it when the old iterator disappears
                // XXX change the return type to have access to the other methods
                return new BreadthFirstIterator<T>(this);
        }

        /**
         * This implementation creates an instance of
         * {@link org.graphstream.graph#BreadthFirstIterator} and returns it.
         * 
         * @see org.graphstream.graph.Node#getBreadthFirstIterator(boolean)
         */
        public <T extends Node> Iterator<T> getBreadthFirstIterator(boolean directed) {
                // XXX change it when the old iterator disappears
                // XXX change the return type to have access to the other methods
                return new BreadthFirstIterator<T>(this, directed);
        }

        /**
         * This implementation creates an instance of
         * {@link org.graphstream.graph#DepthFirstIterator} and returns it.
         * 
         * @see org.graphstream.graph.Node#getDepthFirstIterator()
         */
        public <T extends Node> Iterator<T> getDepthFirstIterator() {
                // XXX change it when the old iterator disappears
                // XXX change the return type to have access to the other methods
                return new DepthFirstIterator<T>(this);
        }

        /**
         * This implementation creates an instance of
         * {@link org.graphstream.graph#DepthFirstIterator} and returns it.
         * 
         * @see org.graphstream.graph.Node#getDepthFirstIterator(boolean)
         */
        public <T extends Node> Iterator<T> getDepthFirstIterator(boolean directed) {
                // XXX change it when the old iterator disappears
                // XXX change the return type to have access to the other methods
                return new DepthFirstIterator<T>(this, directed);
        }

        // *** Other methods ***

        /**
         * This method is called automatically when an edge incident to this node is
         * created. Subclasses use it to add the edge to their data structure.
         * 
         * @param edge
         *            a new edge incident to this node
         */
        protected abstract boolean addEdgeCallback(AbstractEdge edge);

        /**
         * This method is called automatically before removing an edge incident to
         * this node. Subclasses use it to remove the edge from their data
         * structure.
         * 
         * @param edge
         *            an edge incident to this node that will be removed
         */
        protected abstract void removeEdgeCallback(AbstractEdge edge);

        /**
         * This method is called for each node when the graph is cleared. Subclasses
         * may use it to clear their data structures in order to facilitate the
         * garbage collection.
         */
        protected abstract void clearCallback();

        /**
         * Checks if an edge enters this node. Utility method that can be useful in
         * subclasses.
         * 
         * @param e
         *            an edge
         * @return {@code true} if {@code e} is entering edge for this node.
         */
        public boolean isEnteringEdge(Edge e) {
                return e.getTargetNode() == this
                                || (!e.isDirected() && e.getSourceNode() == this);
        }

        /**
         * Checks if an edge leaves this node. Utility method that can be useful in
         * subclasses.
         * 
         * @param e
         *            an edge
         * @return {@code true} if {@code e} is leaving edge for this node.
         */
        public boolean isLeavingEdge(Edge e) {
                return e.getSourceNode() == this
                                || (!e.isDirected() && e.getTargetNode() == this);
        }

        /**
         * Checks if an edge is incident to this node. Utility method that can be
         * useful in subclasses.
         * 
         * @param e
         *            an edge
         * @return {@code true} if {@code e} is incident edge for this node.
         */
        public boolean isIncidentEdge(Edge e) {
                return e.getSourceNode() == this || e.getTargetNode() == this;
        }
}