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/**
* Copyright (C) 2020-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include <memory>
#include <string>
#include <utility>
#include <vector>
#include "mongo/base/status.h"
#include "mongo/stdx/unordered_map.h"
#include "mongo/stdx/unordered_set.h"
namespace mongo {
/**
* To separate concerns, this just captures the setup and execution of a
* topological sort without regard to higher-level semantics like process
* initialization. Each node is mapped to an abstract Data payload.
*/
class DependencyGraph {
public:
class Payload {
public:
virtual ~Payload() = default;
};
/**
* Add a new initializer node, named `name`, to the dependency graph,
* having the given `prerequisites` and `dependents`, which are the names
* of other nodes which will be in the graph when `topSort` is called.
*
* The new node can be mapped to an abstract `payload`, which can
* be retrieved with `find`.
*
* Note that cycles in the dependency graph are not discovered by this function.
* Rather, they're discovered by `topSort`, below.
*/
void addNode(std::string name,
std::vector<std::string> prerequisites,
std::vector<std::string> dependents,
std::unique_ptr<Payload> payload = nullptr);
/**
* Returns a topological sort of the dependency graph, represented
* as an ordered vector of node names.
*
* Throws with `ErrorCodes::GraphContainsCycle` if the graph contains a cycle.
* If a `cycle` is given, it will be overwritten with the node sequence involved.
*
* Throws with `ErrorCodes::BadValue` if any node in the graph names a
* prerequisite that is missing from the graph.
*/
std::vector<std::string> topSort(std::vector<std::string>* cycle = nullptr) const;
Payload* find(const std::string& name);
private:
struct Node {
stdx::unordered_set<std::string> prerequisites;
std::unique_ptr<Payload> payload;
};
/**
* Map of all named nodes. Nodes named as prerequisites or dependents but not explicitly
* added via addInitializer will either be absent from this map or be present with
* NodeData::fn set to a false-ish value.
*/
stdx::unordered_map<std::string, Node> _nodes;
};
} // namespace mongo
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