session_scoped.h

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// SPDX-License-Identifier: Apache-2.0
#pragma once
 
#include <cstddef>
#include <mutex>
#include <string>
#include <unordered_map>
 
namespace entropic {
 
template <typename T>
class SessionScoped {
public:
    template <typename Fn>
    auto with(const std::string& key, Fn&& fn) {
        std::lock_guard<std::mutex> lock(mutex_);
        return fn(by_session_[key]);
    }
 
    template <typename Fn>
    auto peek(const std::string& key, Fn&& fn) const {
        std::lock_guard<std::mutex> lock(mutex_);
        auto it = by_session_.find(key);
        return fn(it == by_session_.end() ? nullptr : &it->second);
    }
 
    bool release(const std::string& key) {
        std::lock_guard<std::mutex> lock(mutex_);
        return by_session_.erase(key) > 0;
    }
 
    std::size_t session_count() const {
        std::lock_guard<std::mutex> lock(mutex_);
        return by_session_.size();
    }
 
private:
    mutable std::mutex mutex_;                     
    std::unordered_map<std::string, T> by_session_; 
};
 
class SessionStateOwner {
public:
    virtual ~SessionStateOwner() = default;
 
    virtual bool release_session(const std::string& key) = 0;
 
    virtual std::size_t session_count() const = 0;
};
 
}  // namespace entropic