VarSub.hpp

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// The Reactive C++ Toolbox.
// Copyright (C) 2013-2019 Swirly Cloud Limited
// Copyright (C) 2021 Reactive Markets Limited
//
// 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.
 
#ifndef TOOLBOX_UTIL_VARSUB_HPP
#define TOOLBOX_UTIL_VARSUB_HPP
 
#include <toolbox/Config.h>
 
#include <functional>
#include <set>
#include <string>
 
namespace toolbox {
inline namespace util {
 
TOOLBOX_API std::string get_env(const std::string& name);
 
class TOOLBOX_API VarSub {
  public:
    explicit VarSub(std::function<std::string(const std::string&)> fn = get_env)
    : fn_{std::move(fn)}
    {
    }
    ~VarSub();
 
    // Copy.
    VarSub(const VarSub&);
    VarSub& operator=(const VarSub&);
 
    // Move.
    VarSub(VarSub&&) noexcept;
    VarSub& operator=(VarSub&&) noexcept;
 
    void operator()(std::string& s) const { substitute(s, std::string::npos, 0); }
 
  private:
    bool substitute(std::string& s, const std::size_t i, std::size_t j,
                    std::set<std::string>* outer = nullptr) const;
 
    std::function<std::string(const std::string&)> fn_;
};
 
} // namespace util
} // namespace toolbox
 
#endif // TOOLBOX_UTIL_VARSUB_HPP