initializer_dependency_graph.h

/*    Copyright 2012 10gen Inc.
 *
 *    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.
 */

#pragma once

#include <string>
#include <vector>
#include <utility>

#include "mongo/base/disallow_copying.h"
#include "mongo/base/initializer_function.h"
#include "mongo/base/status.h"
#include "mongo/platform/unordered_map.h"
#include "mongo/platform/unordered_set.h"

namespace mongo {

class InitializerDependencyGraph {
    MONGO_DISALLOW_COPYING(InitializerDependencyGraph);

public:
    InitializerDependencyGraph();
    ~InitializerDependencyGraph();

    Status addInitializer(const std::string& name,
                          const InitializerFunction& fn,
                          const std::vector<std::string>& prerequisites,
                          const std::vector<std::string>& dependents);

    InitializerFunction getInitializerFunction(const std::string& name) const;

    Status topSort(std::vector<std::string>* sortedNames) const;

private:
    struct NodeData {
        InitializerFunction fn;
        unordered_set<std::string> prerequisites;
    };

    typedef unordered_map<std::string, NodeData> NodeMap;
    typedef NodeMap::value_type Node;

    static Status recursiveTopSort(const NodeMap& nodeMap,
                                   const Node& currentNode,
                                   std::vector<std::string>* inProgressNodeNames,
                                   unordered_set<std::string>* visitedNodeNames,
                                   std::vector<std::string>* sortedNames);

    NodeMap _nodes;
};

}  // namespace mongo