feat(Core/Config): Implement config override with env vars (#16817)

* Core/Config: Implement config override with env vars

Implement overriding of configuration from the .conf file with environment variables.
Environment variables keys are autogenerated based on the keys defined in .conf file.

Usage example:

$ export TC_DATA_DIR=/usr
$ AC_WORLD_SERVER_PORT=8080 ./worldserver

* Add tests for env vars config

5 files changed, 277 insertions, 5 deletions

diff --git a/src/common/Configuration/Config.cpp b/src/common/Configuration/Config.cpp
index d5750120d0..d01d3f7b88 100644
--- a/src/common/Configuration/Config.cpp
+++ b/src/common/Configuration/Config.cpp
@@ -21,6 +21,7 @@
 #include "StringFormat.h"
 #include "Tokenize.h"
 #include "Util.h"
+#include <cstdlib>
 #include <fstream>
 #include <mutex>
 #include <unordered_map>
@@ -215,6 +216,81 @@ namespace
 
         return false;
     }
+
+    // Converts ini keys to the environment variable key (upper snake case).
+    // Example of conversions:
+    //   SomeConfig => SOME_CONFIG
+    //   myNestedConfig.opt1 => MY_NESTED_CONFIG_OPT_1
+    //   LogDB.Opt.ClearTime => LOG_DB_OPT_CLEAR_TIME
+    std::string IniKeyToEnvVarKey(std::string const& key)
+    {
+        std::string result;
+
+        const char* str = key.c_str();
+        size_t n = key.length();
+
+        char curr;
+        bool isEnd;
+        bool nextIsUpper;
+        bool currIsNumeric;
+        bool nextIsNumeric;
+
+        for (size_t i = 0; i < n; ++i)
+        {
+            curr = str[i];
+            if (curr == ' ' || curr == '.' || curr == '-')
+            {
+                result += '_';
+                continue;
+            }
+
+            isEnd = i == n - 1;
+            if (!isEnd)
+            {
+                nextIsUpper = isupper(str[i + 1]);
+
+                // handle "aB" to "A_B"
+                if (!isupper(curr) && nextIsUpper)
+                {
+                    result += static_cast<char>(std::toupper(curr));
+                    result += '_';
+                    continue;
+                }
+
+                currIsNumeric = isNumeric(curr);
+                nextIsNumeric = isNumeric(str[i + 1]);
+
+                // handle "a1" to "a_1"
+                if (!currIsNumeric && nextIsNumeric)
+                {
+                    result += static_cast<char>(std::toupper(curr));
+                    result += '_';
+                    continue;
+                }
+
+                // handle "1a" to "1_a"
+                if (currIsNumeric && !nextIsNumeric)
+                {
+                    result += static_cast<char>(std::toupper(curr));
+                    result += '_';
+                    continue;
+                }
+            }
+
+            result += static_cast<char>(std::toupper(curr));
+        }
+        return result;
+    }
+
+    Optional<std::string> EnvVarForIniKey(std::string const& key)
+    {
+        std::string envKey = "AC_" + IniKeyToEnvVarKey(key);
+        char* val = std::getenv(envKey.c_str());
+        if (!val)
+            return std::nullopt;
+
+        return std::string(val);
+    }
 }
 
 bool ConfigMgr::LoadInitial(std::string const& file, bool isReload /*= false*/)
@@ -243,25 +319,72 @@ bool ConfigMgr::Reload()
         return false;
     }
 
-    return LoadModulesConfigs(true, false);
+    if (!LoadModulesConfigs(true, false))
+    {
+        return false;
+    }
+
+    OverrideWithEnvVariablesIfAny();
+
+    return true;
+}
+
+std::vector<std::string> ConfigMgr::OverrideWithEnvVariablesIfAny()
+{
+    std::lock_guard<std::mutex> lock(_configLock);
+
+    std::vector<std::string> overriddenKeys;
+
+    for (auto& itr : _configOptions)
+    {
+        if (itr.first.empty())
+            continue;
+
+        Optional<std::string> envVar = EnvVarForIniKey(itr.first);
+        if (!envVar)
+            continue;
+
+        itr.second = *envVar;
+
+        overriddenKeys.push_back(itr.first);
+    }
+
+    return overriddenKeys;
 }
 
 template<class T>
 T ConfigMgr::GetValueDefault(std::string const& name, T const& def, bool showLogs /*= true*/) const
 {
+    std::string strValue;
     auto const& itr = _configOptions.find(name);
     if (itr == _configOptions.end())
     {
+        Optional<std::string> envVar = EnvVarForIniKey(name);
+        if (!envVar)
+        {
+            if (showLogs)
+            {
+                LOG_ERROR("server.loading", "> Config: Missing property {} in config file {}, add \"{} = {}\" to this file.",
+                    name, _filename, name, Acore::ToString(def));
+            }
+
+            return def;
+        }
+
         if (showLogs)
         {
-            LOG_ERROR("server.loading", "> Config: Missing property {} in config file {}, add \"{} = {}\" to this file.",
-                name, _filename, name, Acore::ToString(def));
+            LOG_WARN("server.loading", "Missing property {} in config file {}, recovered with environment '{}' value.",
+                name.c_str(), _filename.c_str(), envVar->c_str());
         }
 
-        return def;
+        strValue = *envVar;
+    }
+    else
+    {
+        strValue = itr->second;
     }
 
-    auto value = Acore::StringTo<T>(itr->second);
+    auto value = Acore::StringTo<T>(strValue);
     if (!value)
     {
         if (showLogs)
@@ -282,6 +405,18 @@ std::string ConfigMgr::GetValueDefault<std::string>(std::string const& name, std
     auto const& itr = _configOptions.find(name);
     if (itr == _configOptions.end())
     {
+        Optional<std::string> envVar = EnvVarForIniKey(name);
+        if (envVar)
+        {
+            if (showLogs)
+            {
+                LOG_WARN("server.loading", "Missing property {} in config file {}, recovered with environment '{}' value.",
+                    name.c_str(), _filename.c_str(), envVar->c_str());
+            }
+
+            return *envVar;
+        }
+
         if (showLogs)
         {
             LOG_ERROR("server.loading", "> Config: Missing property {} in config file {}, add \"{} = {}\" to this file.",
diff --git a/src/common/Configuration/Config.h b/src/common/Configuration/Config.h
index ddac0efb68..db7410e05e 100644
--- a/src/common/Configuration/Config.h
+++ b/src/common/Configuration/Config.h
@@ -39,6 +39,9 @@ public:
 
     bool Reload();
 
+    /// Overrides configuration with environment variables and returns overridden keys
+    std::vector<std::string> OverrideWithEnvVariablesIfAny();
+
     std::string const GetFilename();
     std::string const GetConfigPath();
     [[nodiscard]] std::vector<std::string> const& GetArguments() const;
diff --git a/src/server/apps/authserver/Main.cpp b/src/server/apps/authserver/Main.cpp
index 4c110db7aa..bc40f2f10b 100644
--- a/src/server/apps/authserver/Main.cpp
+++ b/src/server/apps/authserver/Main.cpp
@@ -85,6 +85,8 @@ int main(int argc, char** argv)
     if (!sConfigMgr->LoadAppConfigs())
         return 1;
 
+    std::vector<std::string> overriddenKeys = sConfigMgr->OverrideWithEnvVariablesIfAny();
+
     // Init logging
     sLog->RegisterAppender<AppenderDB>();
     sLog->Initialize(nullptr);
@@ -101,6 +103,9 @@ int main(int argc, char** argv)
             LOG_INFO("server.authserver", "> Using Boost version:           {}.{}.{}", BOOST_VERSION / 100000, BOOST_VERSION / 100 % 1000, BOOST_VERSION % 100);
         });
 
+    for (std::string const& key : overriddenKeys)
+        LOG_INFO("server.authserver", "Configuration field {} was overridden with environment variable.", key);
+
     OpenSSLCrypto::threadsSetup();
 
     std::shared_ptr<void> opensslHandle(nullptr, [](void*) { OpenSSLCrypto::threadsCleanup(); });
diff --git a/src/server/apps/worldserver/Main.cpp b/src/server/apps/worldserver/Main.cpp
index 01b9f56ab9..7ddcf9ceb5 100644
--- a/src/server/apps/worldserver/Main.cpp
+++ b/src/server/apps/worldserver/Main.cpp
@@ -184,6 +184,8 @@ int main(int argc, char** argv)
     if (!sConfigMgr->LoadAppConfigs())
         return 1;
 
+    std::vector<std::string> overriddenKeys = sConfigMgr->OverrideWithEnvVariablesIfAny();
+
     std::shared_ptr<Acore::Asio::IoContext> ioContext = std::make_shared<Acore::Asio::IoContext>();
 
     // Init all logs
@@ -203,6 +205,9 @@ int main(int argc, char** argv)
             LOG_INFO("server.worldserver", "> Using Boost version:           {}.{}.{}", BOOST_VERSION / 100000, BOOST_VERSION / 100 % 1000, BOOST_VERSION % 100);
         });
 
+    for (std::string const& key : overriddenKeys)
+        LOG_INFO("server.worldserver", "Configuration field {} was overridden with environment variable.", key);
+
     OpenSSLCrypto::threadsSetup();
 
     std::shared_ptr<void> opensslHandle(nullptr, [](void*) { OpenSSLCrypto::threadsCleanup(); });
diff --git a/src/test/common/Configuration/Config.cpp b/src/test/common/Configuration/Config.cpp
new file mode 100644
index 0000000000..81d784d398
--- /dev/null
+++ b/src/test/common/Configuration/Config.cpp
@@ -0,0 +1,124 @@
+/*
+ * This file is part of the AzerothCore Project. See AUTHORS file for Copyright information
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Affero General Public License as published by the
+ * Free Software Foundation; either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "Config.h"
+#include "gtest/gtest.h"
+
+#include <boost/filesystem.hpp>
+#include <cstdlib>
+#include <string>
+
+std::string CreateConfigWithMap(std::map<std::string, std::string> const& map)
+{
+    auto mTempFileRel = boost::filesystem::unique_path("deleteme.ini");
+    auto mTempFileAbs = boost::filesystem::temp_directory_path() / mTempFileRel;
+    std::ofstream iniStream;
+    iniStream.open(mTempFileAbs.c_str());
+
+    iniStream << "[test]\n";
+    for (auto const& itr : map)
+        iniStream << itr.first << " = " << itr.second << "\n";
+
+    iniStream.close();
+
+    return mTempFileAbs.native();
+}
+
+class ConfigEnvTest : public testing::Test {
+protected:
+    void SetUp() override {
+        std::map<std::string, std::string> config;
+        config["Int.Nested"] = "4242";
+        config["lower"] = "simpleString";
+        config["UPPER"] = "simpleString";
+        config["SomeLong.NestedNameWithNumber.Like1"] = "1";
+        config["GM.InGMList.Level"] = "50";
+
+        confFilePath = CreateConfigWithMap(config);
+
+        sConfigMgr->Configure(confFilePath, std::vector<std::string>());
+        sConfigMgr->LoadAppConfigs();
+    }
+
+    void TearDown() override {
+        std::remove(confFilePath.c_str());
+    }
+
+    std::string confFilePath;
+};
+
+TEST_F(ConfigEnvTest, NestedInt)
+{
+    EXPECT_EQ(sConfigMgr->GetOption<int32>("Int.Nested", 10), 4242);
+    setenv("AC_INT_NESTED", "8080", 1);
+    EXPECT_EQ(sConfigMgr->OverrideWithEnvVariablesIfAny().empty(), false);
+    EXPECT_EQ(sConfigMgr->GetOption<int32>("Int.Nested", 10), 8080);
+}
+
+TEST_F(ConfigEnvTest, SimpleLowerString)
+{
+    EXPECT_EQ(sConfigMgr->GetOption<std::string>("lower", ""), "simpleString");
+    setenv("AC_LOWER", "envstring", 1);
+    EXPECT_EQ(sConfigMgr->OverrideWithEnvVariablesIfAny().empty(), false);
+    EXPECT_EQ(sConfigMgr->GetOption<std::string>("lower", ""), "envstring");
+}
+
+TEST_F(ConfigEnvTest, SimpleUpperString)
+{
+    EXPECT_EQ(sConfigMgr->GetOption<std::string>("UPPER", ""), "simpleString");
+    setenv("AC_UPPER", "envupperstring", 1);
+    EXPECT_EQ(sConfigMgr->OverrideWithEnvVariablesIfAny().empty(), false);
+    EXPECT_EQ(sConfigMgr->GetOption<std::string>("UPPER", ""), "envupperstring");
+}
+
+TEST_F(ConfigEnvTest, LongNestedNameWithNumber)
+{
+    EXPECT_EQ(sConfigMgr->GetOption<float>("SomeLong.NestedNameWithNumber.Like1", 0), 1);
+    setenv("AC_SOME_LONG_NESTED_NAME_WITH_NUMBER_LIKE_1", "42", 1);
+    EXPECT_EQ(sConfigMgr->OverrideWithEnvVariablesIfAny().empty(), false);
+    EXPECT_EQ(sConfigMgr->GetOption<float>("SomeLong.NestedNameWithNumber.Like1", 0), 42);
+}
+
+TEST_F(ConfigEnvTest, ValueWithSeveralUpperlLaters)
+{
+    EXPECT_EQ(sConfigMgr->GetOption<int>("GM.InGMList.Level", 1), 50);
+    setenv("AC_GM_IN_GMLIST_LEVEL", "42", 1);
+    EXPECT_EQ(sConfigMgr->OverrideWithEnvVariablesIfAny().empty(), false);
+    EXPECT_EQ(sConfigMgr->GetOption<int>("GM.InGMList.Level", 0), 42);
+}
+
+TEST_F(ConfigEnvTest, StringThatNotExistInConfig)
+{
+    setenv("AC_UNIQUE_STRING", "somevalue", 1);
+    EXPECT_EQ(sConfigMgr->GetOption<std::string>("Unique.String", ""), "somevalue");
+}
+
+TEST_F(ConfigEnvTest, IntThatNotExistInConfig)
+{
+    setenv("AC_UNIQUE_INT", "100", 1);
+    EXPECT_EQ(sConfigMgr->GetOption<int>("Unique.Int", 1), 100);
+}
+
+TEST_F(ConfigEnvTest, NotExistingString)
+{
+    EXPECT_EQ(sConfigMgr->GetOption<std::string>("NotFound.String", "none"), "none");
+}
+
+TEST_F(ConfigEnvTest, NotExistingInt)
+{
+    EXPECT_EQ(sConfigMgr->GetOption<int>("NotFound.Int", 1), 1);
+}