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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.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;


/**
 * Default implementation of a depth first search.
 */
public class DepthFirstTraverserImpl implements DepthFirstTraverser {

    public List> traverse(DirectedGraph graph, Vertex start) {
        return traverse(graph, start, new TrueVisitor());
    }

    public List> traversePath(DirectedGraph graph, Vertex start, Vertex end) {
        TerminatingVisitor visitor = new TerminatingVisitor<>(end);
        List> path = traverse(graph, start, visitor);
        if (visitor.wasFound()) {
            return path;
        }
        return Collections.emptyList();
    }

    private List> traverse(DirectedGraph graph, Vertex start, Visitor visitor) {
        List> visited = new ArrayList<>();
        List> stack = new ArrayList<>();
        Set> seen = new HashSet<>(visited);
        stack.add(start);
        seen.add(start);
        do {
            // mark as visited
            Vertex next = stack.remove(stack.size() - 1);
            visited.add(next);
            if (!visitor.visit(next)) {
                return visited;
            }

            // add all non-visited adjacent vertices to the stack
            Set> adjacentVertices = graph.getAdjacentVertices(next);
            for (Vertex v : adjacentVertices) {
                seen.add(v);
                stack.add(v);
            }

        } while (!stack.isEmpty());
        return visited;
    }


}