feat: support system-wide runtime configuration

Add system configuration directory at /etc/linglong. Configs are now
merged merged in order: system global, system app-specific, user global,
then user global and user app-specific, allowing user configs to
override system defaults.

Signed-off-by: reddevillg <reddevillg@gmail.com>

Author: reddevillg

libs/common/src/linglong/common/dir.cpp

@@ -53,4 +53,9 @@ std::filesystem::path getUserRuntimeConfigDir() noexcept
     return configDir / "linglong";
 }
 
+std::filesystem::path getSystemRuntimeConfigDir() noexcept
+{
+    return "/etc/linglong";
+}
+
 } // namespace linglong::common::dir

libs/common/src/linglong/common/dir.h

@@ -29,4 +29,6 @@ std::filesystem::path getUserCacheDir() noexcept;
 
 std::filesystem::path getUserRuntimeConfigDir() noexcept;
 
+std::filesystem::path getSystemRuntimeConfigDir() noexcept;
+
 } // namespace linglong::common::dir

libs/utils/src/linglong/utils/runtime_config.cpp

@@ -45,7 +45,35 @@ loadUserRuntimeConfig(const std::string &appId)
         return LINGLONG_ERR(result);
     }
 
-    return std::move(result).value();
+    return result;
+}
+
+linglong::utils::error::Result<std::optional<RuntimeConfigure>>
+loadSystemRuntimeConfig(const std::string &appId)
+{
+    LINGLONG_TRACE(
+      fmt::format("load system runtime config for {}", appId.empty() ? "global" : appId));
+
+    auto configDir = linglong::common::dir::getSystemRuntimeConfigDir();
+
+    std::filesystem::path configPath;
+    if (appId.empty()) {
+        configPath = configDir / "config.json";
+    } else {
+        configPath = configDir / "apps" / appId / "config.json";
+    }
+
+    std::error_code ec;
+    if (!std::filesystem::exists(configPath, ec)) {
+        return std::nullopt;
+    }
+
+    auto result = linglong::utils::loadRuntimeConfig(configPath);
+    if (!result) {
+        return LINGLONG_ERR(result);
+    }
+
+    return result;
 }
 
 } // namespace
@@ -112,30 +140,46 @@ loadRuntimeConfig(const std::filesystem::path &path)
         return LINGLONG_ERR("failed to load runtime config", result);
     }
 
-    return std::move(result).value();
+    return result;
 }
 
 utils::error::Result<std::optional<RuntimeConfigure>> loadRuntimeConfig(const std::string &appId)
 {
     LINGLONG_TRACE("load runtime config for app: " + appId);
 
-    // Merge configs in order: user global -> user app
+    // Merge configs in order: system global -> system app -> user global -> user app
     std::vector<RuntimeConfigure> configs;
 
+    auto systemGlobal = loadSystemRuntimeConfig("");
+    if (!systemGlobal) {
+        return LINGLONG_ERR(systemGlobal);
+    }
+    if (systemGlobal->has_value()) {
+        configs.emplace_back(systemGlobal->value());
+    }
+
+    auto systemApp = loadSystemRuntimeConfig(appId);
+    if (!systemApp) {
+        return LINGLONG_ERR(systemApp);
+    }
+    if (systemApp->has_value()) {
+        configs.emplace_back(systemApp->value());
+    }
+
     auto userGlobal = loadUserRuntimeConfig("");
     if (!userGlobal) {
         return LINGLONG_ERR(userGlobal);
     }
-    if ((*userGlobal).has_value()) {
-        configs.emplace_back((*userGlobal).value());
+    if (userGlobal->has_value()) {
+        configs.emplace_back(userGlobal->value());
     }
 
     auto userApp = loadUserRuntimeConfig(appId);
     if (!userApp) {
         return LINGLONG_ERR(userApp);
     }
-    if ((*userApp).has_value()) {
-        configs.emplace_back((*userApp).value());
+    if (userApp->has_value()) {
+        configs.emplace_back(userApp->value());
     }
 
     if (configs.empty()) {