/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */
package storm.trident.graph;

import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;

import org.jgrapht.DirectedGraph;

import storm.trident.planner.Node;
import storm.trident.util.IndexedEdge;

public class GraphGrouper {
    final DirectedGraph<Node, IndexedEdge> graph;
    final Set<Group> currGroups;
    final Map<Node, Group> groupIndex = new HashMap<>();
    
    public GraphGrouper(DirectedGraph<Node, IndexedEdge> graph, Collection<Group> initialGroups) {
        this.graph = graph;
        this.currGroups = new LinkedHashSet<>(initialGroups);
        reindex();
    }

    public Collection<Group> getAllGroups() {
        return currGroups;
    }

    public void addGroup(Group g) {
        currGroups.add(g);
    }

    public void reindex() {
        groupIndex.clear();
        for (Group g : currGroups) {
            for (Node n : g.nodes) {
                groupIndex.put(n, g);
            }
        }
    }

    public void mergeFully() {
        boolean somethingHappened = true;
        while (somethingHappened) {
            somethingHappened = false;
            for (Group g : currGroups) {
                Collection<Group> outgoingGroups = outgoingGroups(g);
                if (outgoingGroups.size() == 1) {
                    Group out = outgoingGroups.iterator().next();
                    if (out != null) {
                        merge(g, out);
                        somethingHappened = true;
                        break;
                    }
                }

                Collection<Group> incomingGroups = incomingGroups(g);
                if (incomingGroups.size() == 1) {
                    Group in = incomingGroups.iterator().next();
                    if (in != null) {
                        merge(g, in);
                        somethingHappened = true;
                        break;
                    }
                }
            }
        }
    }

    private void merge(Group g1, Group g2) {
        Group newGroup = new Group(g1, g2);
        currGroups.remove(g1);
        currGroups.remove(g2);
        currGroups.add(newGroup);
        for (Node n : newGroup.nodes) {
            groupIndex.put(n, newGroup);
        }
    }

    public Collection<Group> outgoingGroups(Group g) {
        Set<Group> ret = new HashSet<>();
        for(Node n: g.outgoingNodes()) {
            Group other = nodeGroup(n);
            if (other == null || !other.equals(g)) {
                ret.add(other);
            }
        }
        return ret;
    }

    public Collection<Group> incomingGroups(Group g) {
        Set<Group> ret = new HashSet<>();
        for(Node n: g.incomingNodes()) {
            Group other = nodeGroup(n);
            if (other == null || !other.equals(g)) {
                ret.add(other);
            }
        }
        return ret;
    }

    public Group nodeGroup(Node n) {
        return groupIndex.get(n);
    }

}