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/*
 * (C) Copyright 2015-2018, by Barak Naveh and Contributors.
 *
 * JGraphT : a free Java graph-theory library
 *
 * This program and the accompanying materials are dual-licensed under
 * either
 *
 * (a) the terms of the GNU Lesser General Public License version 2.1
 * as published by the Free Software Foundation, or (at your option) any
 * later version.
 *
 * or (per the licensee's choosing)
 *
 * (b) the terms of the Eclipse Public License v1.0 as published by
 * the Eclipse Foundation.
 */
package org.jgrapht.graph.specifics;

import java.util.*;

/**
 * An interface encapsulating the basic graph operations. Different implementations have different
 * space-time tradeoffs.
 *
 * @param  the graph vertex type
 * @param  the graph edge type
 *
 * @author Barak Naveh
 */
public interface Specifics
{
    /**
     * Adds a vertex.
     *
     * @param vertex vertex to be added.
     * @return true if the vertex was added, false if the vertex was already present
     */
    boolean addVertex(V vertex);

    /**
     * Get the vertex set.
     * 
     * @return the vertex set
     */
    Set getVertexSet();

    /**
     * Returns a set of all edges connecting source vertex to target vertex if such vertices exist
     * in this graph. If any of the vertices does not exist or is null, returns
     * null. If both vertices exist but no edges found, returns an empty set.
     *
     * @param sourceVertex source vertex of the edge.
     * @param targetVertex target vertex of the edge.
     *
     * @return a set of all edges connecting source vertex to target vertex.
     */
    Set getAllEdges(V sourceVertex, V targetVertex);

    /**
     * Returns an edge connecting source vertex to target vertex if such vertices and such edge
     * exist in this graph. Otherwise returns 
     * null. If any of the specified vertices is null returns null
     *
     * 
     * In undirected graphs, the returned edge may have its source and target vertices in the
     * opposite order.
     * 
     *
     * @param sourceVertex source vertex of the edge.
     * @param targetVertex target vertex of the edge.
     *
     * @return an edge connecting source vertex to target vertex.
     */
    E getEdge(V sourceVertex, V targetVertex);

    /**
     * Adds the specified edge to the edge containers of its source and target vertices.
     *
     * @param e the edge
     */
    void addEdgeToTouchingVertices(E e);

    /**
     * Returns the degree of the specified vertex. A degree of a vertex in an undirected graph is
     * the number of edges touching that vertex.
     *
     * @param vertex vertex whose degree is to be calculated.
     *
     * @return the degree of the specified vertex.
     */
    int degreeOf(V vertex);

    /**
     * Returns a set of all edges touching the specified vertex. If no edges are touching the
     * specified vertex returns an empty set.
     *
     * @param vertex the vertex for which a set of touching edges is to be returned.
     * @return a set of all edges touching the specified vertex.
     */
    Set edgesOf(V vertex);

    /**
     * Returns the "in degree" of the specified vertex.
     *
     * @param vertex vertex whose in degree is to be calculated.
     * @return the in degree of the specified vertex.
     */
    int inDegreeOf(V vertex);

    /**
     * Returns a set of all edges incoming into the specified vertex.
     *
     * @param vertex the vertex for which the list of incoming edges to be returned.
     * @return a set of all edges incoming into the specified vertex.
     */
    Set incomingEdgesOf(V vertex);

    /**
     * Returns the "out degree" of the specified vertex.
     *
     * @param vertex vertex whose out degree is to be calculated.
     * @return the out degree of the specified vertex.
     */
    int outDegreeOf(V vertex);

    /**
     * Returns a set of all edges outgoing from the specified vertex.
     *
     * @param vertex the vertex for which the list of outgoing edges to be returned.
     *
     * @return a set of all edges outgoing from the specified vertex.
     */
    Set outgoingEdgesOf(V vertex);

    /**
     * Removes the specified edge from the edge containers of its source and target vertices.
     *
     * @param e the edge
     */
    void removeEdgeFromTouchingVertices(E e);
}