Added support for getting optional value #33 (#34)

* getOptional function added

* getOptional unit test added

* added optional function instances

* code refractor

* review comments

* minor comment

include/config-cxx/Config.h

@@ -32,6 +32,24 @@ class Config
     template <typename T>
     T get(const std::string& keyPath);
 
+    /**
+     * @brief Get a config value by path if it exists.
+     *
+     * @tparam T The target type of config value.
+     *
+     * @param path The path to config key.
+     *
+     * @return The value of config key casted to provided type or std::nullopt.
+     *
+     * @code
+     * Config().getOptional<std::string>("db.host") // "localhost"
+     * Config().getOptional<int>("db.port") // 3306
+     * Config().getOptional<std::string>("redis.host") // std::nullopt
+     * @endcode
+     */
+    template <typename T>
+    std::optional<T> getOptional(const std::string& keyPath);
+
     /**
      * @brief Get a config value by path.
      *

src/Config.cpp

@@ -2,6 +2,7 @@
 
 #include <filesystem>
 #include <iostream>
+#include <optional>
 #include <stdexcept>
 #include <variant>
 
@@ -56,6 +57,47 @@ T Config::get(const std::string& keyPath)
     }
 }
 
+template <typename T>
+std::optional<T> Config::getOptional(const std::string& keyPath)
+{
+    std::lock_guard<std::mutex> lockGuard(lock);
+
+    if (!initialized)
+    {
+        initialize();
+    }
+
+    if constexpr (std::is_same_v<T, std::vector<std::string>>)
+    {
+        return getArray(keyPath);
+    }
+
+    auto it = values.find(keyPath);
+    if (it == values.end())
+    {
+        return std::nullopt;
+    }
+
+    const auto& value = it->second;
+
+    if (value.index() == 0)
+    {
+        return std::nullopt;
+    }
+
+    std::optional<T> castedValue = config::cast<T>(value);
+
+    if (castedValue)
+    {
+        return castedValue.value();
+    }
+
+    else
+    {
+        throw std::runtime_error("Config key " + keyPath + " has value of wrong type.");
+    }
+}
+
 ConfigValue Config::get(const std::string& keyPath)
 {
     std::lock_guard<std::mutex> lockGuard(lock);
@@ -226,4 +268,10 @@ template bool Config::get<bool>(const std::string&);
 template std::string Config::get<std::string>(const std::string&);
 template std::vector<std::string> Config::get<std::vector<std::string>>(const std::string&);
 template float Config::get<float>(const std::string&);
+
+template std::optional<int> Config::getOptional<int>(const std::string&);
+template std::optional<bool> Config::getOptional<bool>(const std::string&);
+template std::optional<std::string> Config::getOptional<std::string>(const std::string&);
+template std::optional<std::vector<std::string>> Config::getOptional<std::vector<std::string>>(const std::string&);
+template std::optional<float> Config::getOptional<float>(const std::string&);
 }

src/ConfigTest.cpp

@@ -1,6 +1,7 @@
 #include "config-cxx/Config.h"
 
 #include <filesystem>
+#include <optional>
 #include <fstream>
 #include <stdexcept>
 
@@ -421,4 +422,36 @@ TEST_F(ConfigTest, configWorksWithJsonAndXml)
     ASSERT_EQ(authRolesValue, expectedAuthRoles);
     ASSERT_EQ(userNameValue, "Koko");
     ASSERT_EQ(userActiveValue, false);
-}
+}
+
+TEST_F(ConfigTest, givenCxxEnvAndConfigDir_returnsOptionalKeyValues)
+{
+    EnvironmentSetter::setEnvironmentVariable("CXX_ENV", "test");
+    EnvironmentSetter::setEnvironmentVariable("CXX_CONFIG_DIR", testConfigDirectory.string());
+
+    const auto awsAccountId = "9999999999";
+    const auto awsAccountKey = "806223445";
+
+    EnvironmentSetter::setEnvironmentVariable("AWS_ACCOUNT_ID", awsAccountId);
+    EnvironmentSetter::setEnvironmentVariable("AWS_ACCOUNT_KEY", awsAccountKey);
+
+    Config config;
+
+    const std::string dbHostKey = "db.host";
+    const std::string dbPortKey = "db.port";
+    const std::string awsAccountIdKey = "aws.accountId";
+    const std::string awsAccountKeyKey = "aws.accountKey";
+    const std::string nonExistantKey = "redis.host";
+
+    const auto dbHostValue = config.getOptional<std::string>(dbHostKey);
+    const auto dbPortValue = config.getOptional<int>(dbPortKey);
+    const auto awsAccountIdValue = config.getOptional<std::string>(awsAccountIdKey);
+    const auto awsAccountKeyValue = config.getOptional<std::string>(awsAccountKeyKey);
+    const auto nonExistantKeyValue = config.getOptional<std::string>(nonExistantKey);
+
+    ASSERT_EQ(*dbHostValue, "localhost");
+    ASSERT_EQ(*dbPortValue, 1996);
+    ASSERT_EQ(*awsAccountIdValue, awsAccountId);
+    ASSERT_EQ(*awsAccountKeyValue, awsAccountKey);
+    ASSERT_EQ(nonExistantKeyValue.has_value(), false);
+}