stats_snapshot.h

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// BSD 3-Clause License
// Copyright (c) 2025, 🍀☀🌕🌥 🌊
// See the LICENSE file in the project root for full license information.
 
#pragma once
 
#include <chrono>
#include <sstream>
#include <string>
#include <unordered_map>
#include <variant>
#include <iomanip>
 
namespace kcenon::common::interfaces {
 
// Forward declare to avoid circular dependency
using stats_value = std::variant<std::int64_t, double, std::string, bool>;
 
struct stats_snapshot {
    std::string component_name;                             
    std::chrono::system_clock::time_point timestamp;        
    std::unordered_map<std::string, stats_value> values;    
 
    [[nodiscard]] auto to_json() const -> std::string
    {
        std::ostringstream json;
        json << "{\n";
        json << "  \"component\": \"" << component_name << "\",\n";
 
        // Format timestamp as ISO 8601
        const auto time_t = std::chrono::system_clock::to_time_t(timestamp);
        std::tm tm{};
#ifdef _WIN32
        localtime_s(&tm, &time_t);
#else
        localtime_r(&time_t, &tm);
#endif
        json << "  \"timestamp\": \""
             << std::put_time(&tm, "%Y-%m-%dT%H:%M:%S")
             << "Z\",\n";
 
        // Serialize metrics
        json << "  \"metrics\": {\n";
 
        bool first = true;
        for (const auto& [key, value] : values) {
            if (!first) {
                json << ",\n";
            }
            first = false;
 
            json << "    \"" << key << "\": ";
 
            // Visit variant and format value
            std::visit([&json](const auto& v) {
                using T = std::decay_t<decltype(v)>;
                if constexpr (std::is_same_v<T, std::int64_t>) {
                    json << v;
                } else if constexpr (std::is_same_v<T, double>) {
                    json << std::fixed << std::setprecision(6) << v;
                } else if constexpr (std::is_same_v<T, std::string>) {
                    json << "\"" << v << "\"";
                } else if constexpr (std::is_same_v<T, bool>) {
                    json << (v ? "true" : "false");
                }
            }, value);
        }
 
        json << "\n  }\n";
        json << "}";
 
        return json.str();
    }
};
 
} // namespace kcenon::common::interfaces