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/*
 * Fabric3
 * Copyright (c) 2009-2015 Metaform Systems
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * Portions originally based on Apache Tuscany 2007
 * licensed under the Apache 2.0 license.
 */
package org.fabric3.util.graph;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

/**
 * Default directed graph implementation.
 */
public class DirectedGraphImpl implements DirectedGraph {
    private Map, VertexHolder> graphVertices;
    private Set> graphEdges;

    public DirectedGraphImpl() {
        graphVertices = new HashMap<>();
        graphEdges = new HashSet<>();
    }

    public Set> getVertices() {
        return graphVertices.keySet();
    }

    public void add(Vertex vertex) {
        if (graphVertices.containsKey(vertex)) {
            return;
        }
        graphVertices.put(vertex, new VertexHolder());
    }

    public void remove(Vertex vertex) {
        List> edges = new ArrayList<>(getOutgoingEdges(vertex));
        for (Edge edge : edges) {
            removeEdge(edge);
        }
        graphVertices.remove(vertex);
    }

    public Set> getAdjacentVertices(Vertex vertex) {
        Set> adjacentVertices = new HashSet<>();
        Set> incidentEdges = getOutgoingEdges(vertex);
        if (incidentEdges != null) {
            for (Edge edge : incidentEdges) {
                adjacentVertices.add(edge.getOppositeVertex(vertex));
            }
        }
        return adjacentVertices;
    }

    public List> getOutgoingAdjacentVertices(Vertex vertex) {
        return getAdjacentVertices(vertex, true);
    }

    public List> getIncomingAdjacentVertices(Vertex vertex) {
        return getAdjacentVertices(vertex, false);
    }

    public Edge getEdge(Vertex source, Vertex sink) {
        Set> edges = getOutgoingEdges(source);
        for (Edge edge : edges) {
            if (edge.getSink() == sink) {
                return edge;
            }
        }
        return null;
    }

    public Set> getOutgoingEdges(Vertex vertex) {
        return graphVertices.get(vertex).getOutgoingEdges();
    }

    public Set> getIncomingEdges(Vertex vertex) {
        return graphVertices.get(vertex).getIncomingEdges();
    }

    public Set> getEdges() {
        return graphEdges;
    }

    public void add(Edge edge) {
        if (graphEdges.contains(edge)) {
            return;
        }
        Vertex source = edge.getSource();
        Vertex sink = edge.getSink();

        if (!graphVertices.containsKey(source)) {
            add(source);
        }
        if ((sink != source) && !graphVertices.containsKey(sink)) {
            add(sink);
        }
        Set> sourceEdges = getOutgoingEdges(source);

        sourceEdges.add(edge);
        if (source != sink) {
            // avoid adding the edge a second time if the edge points back on itself
            Set> sinkEdges = getIncomingEdges(sink);
            sinkEdges.add(edge);
        }

        graphEdges.add(edge);
        VertexHolder sourceHolder = graphVertices.get(edge.getSource());
        VertexHolder sinkHolder = graphVertices.get(edge.getSink());
        sourceHolder.getOutgoingEdges().add(edge);
        sinkHolder.getIncomingEdges().add(edge);
    }

    public void remove(Edge edge) {
        removeEdge(edge);
        Vertex source = edge.getSource();
        Vertex sink = edge.getSink();
        VertexHolder sourceHolder = graphVertices.get(source);
        VertexHolder sinkHolder = graphVertices.get(sink);
        // remove the edge from the source's outgoing edges
        sourceHolder.getOutgoingEdges().remove(edge);
        // remove the edge from the sink's incoming edges
        sinkHolder.getIncomingEdges().remove(edge);
    }

    private void removeEdge(Edge edge) {
        // Remove the edge from the vertices incident edges.
        Vertex source = edge.getSource();
        Set> sourceEdges = getOutgoingEdges(source);
        sourceEdges.remove(edge);

        Vertex sink = edge.getSink();
        Set> sinkEdges = getIncomingEdges(sink);
        sinkEdges.remove(edge);

        // Remove the edge from edgeSet
        graphEdges.remove(edge);
    }

    /**
     * Returns the outgoing or incoming adjacent vertices for a given vertex
     *
     * @param vertex   the vertex.
     * @param outGoing true for returning outgoing vertices.
     * @return the adjacent vertices
     */
    private List> getAdjacentVertices(Vertex vertex, boolean outGoing) {
        List> adjacentVertices = new ArrayList<>();
        Set> edges;
        if (outGoing) {
            edges = getOutgoingEdges(vertex);
        } else {
            edges = getIncomingEdges(vertex);
        }
        for (Edge edge : edges) {
            Vertex oppositeVertex = edge.getOppositeVertex(vertex);
            adjacentVertices.add(oppositeVertex);
        }
        return adjacentVertices;
    }

    private class VertexHolder {
        private Set> incoming = new HashSet<>();
        private Set> outgoingEdges = new HashSet<>();

        public Set> getIncomingEdges() {
            return incoming;
        }

        public Set> getOutgoingEdges() {
            return outgoingEdges;
        }

    }

}