smartbotic/lib/config/config_loader.hpp

#pragma once

#include <string>
#include <optional>
#include <filesystem>
#include <nlohmann/json.hpp>
#include "common/error.hpp"

namespace smartbotic::config {

class ConfigLoader {
public:
    // Load configuration from file
    static common::Result<nlohmann::json> loadFromFile(const std::filesystem::path& path);

    // Load configuration from string
    static common::Result<nlohmann::json> loadFromString(const std::string& content);

    // Expand environment variables in JSON values (${VAR:default})
    static nlohmann::json expandEnvVars(const nlohmann::json& config);

    // Get nested value with dot notation (e.g., "database.host")
    static std::optional<nlohmann::json> get(const nlohmann::json& config,
                                              const std::string& path);

    // Get value with default
    template<typename T>
    static T getOr(const nlohmann::json& config, const std::string& path, T defaultValue) {
        auto value = get(config, path);
        if (value.has_value()) {
            try {
                return value->get<T>();
            } catch (...) {
                return defaultValue;
            }
        }
        return defaultValue;
    }

    // Merge two configurations (second overrides first)
    static nlohmann::json merge(const nlohmann::json& base, const nlohmann::json& override);

    // Validate config against schema
    static common::Result<void> validate(const nlohmann::json& config,
                                         const nlohmann::json& schema);
};

// Configuration holder with typed accessors
class Config {
public:
    Config() = default;
    explicit Config(nlohmann::json data);

    // Load from file
    static common::Result<Config> fromFile(const std::filesystem::path& path);

    // Raw access
    const nlohmann::json& data() const { return data_; }
    nlohmann::json& data() { return data_; }

    // Get value with path
    template<typename T>
    std::optional<T> get(const std::string& path) const {
        auto value = ConfigLoader::get(data_, path);
        if (value.has_value()) {
            try {
                return value->get<T>();
            } catch (...) {
                return std::nullopt;
            }
        }
        return std::nullopt;
    }

    // Get value with default
    template<typename T>
    T getOr(const std::string& path, T defaultValue) const {
        return ConfigLoader::getOr(data_, path, std::move(defaultValue));
    }

    // Get required value (throws if not found)
    template<typename T>
    T getRequired(const std::string& path) const {
        auto value = get<T>(path);
        if (!value.has_value()) {
            throw common::SmartBoticException(
                common::Error(common::ErrorCode::InvalidArgument,
                             "Required config value not found: " + path));
        }
        return *value;
    }

    // Check if path exists
    bool has(const std::string& path) const;

    // Reload from file
    common::Result<void> reload(const std::filesystem::path& path);

private:
    nlohmann::json data_;
};

} // namespace smartbotic::config