feat: implement transaction handling for upstream and target operations

- Added transaction support in `add_upstream_target`, `remove_upstream`, `remove_upstream_target`, `update_upstream`, and `update_upstream_target` functions to ensure atomicity of operations.
- Updated the `NginxService` to include methods for validating and applying configurations using the agent service.
- Enhanced error handling in agent service interactions, returning appropriate internal server errors when agent communication fails.
- Introduced mock agent service for testing, allowing for simulation of agent interactions without actual network calls.
- Refactored tests to cover scenarios where agent operations fail, ensuring that internal server errors are returned as expected.

apps/api/src/services/agent_client.rs

@@ -1,14 +1,104 @@
 use std::sync::Arc;
 
-use agent_client::apis::{ApiClient, configuration::Configuration};
+use agent_client::{
+    apis::{
+        Api, ApiClient, Error as ApiError, ResponseContent,
+        configuration::Configuration,
+        nginx_agent_api::{ValidateAndReloadParams, ValidateParams, WriteConfigParams},
+    },
+    models::{ValidateAndReloadBody, ValidateBody, WriteConfigBody},
+};
 use tracing::warn;
 
-use crate::configs::agent::AgentSettings;
+use crate::{configs::agent::AgentSettings, errors::service_error::ServiceError};
 
-pub struct AgentService {
+#[derive(Debug)]
+pub enum AgentError {
+    // (internal messages, user-facing messages)
+    #[allow(dead_code)]
+    ValidationFailed(String, String),
+    // (internal messages, user-facing messages)
+    ApplicationFailed(String, String),
+}
+
+impl From<AgentError> for ServiceError {
+    fn from(err: AgentError) -> Self {
+        match err {
+            AgentError::ValidationFailed(_internal, user) => ServiceError::InternalError(user),
+            AgentError::ApplicationFailed(_internal, user) => ServiceError::InternalError(user),
+        }
+    }
+}
+
+impl<T: std::fmt::Debug> From<ResponseContent<T>> for AgentError {
+    fn from(err: ResponseContent<T>) -> Self {
+        let ResponseContent {
+            status,
+            content,
+            entity,
+        } = err;
+        {
+            let entity_str = entity
+                .map(|e| format!("{:?}", e))
+                .unwrap_or_else(|| "<empty>".to_string());
+            AgentError::ApplicationFailed(
+                format!(
+                    "Agent responded with error status {}: {}, entity: {}",
+                    status, content, entity_str
+                ),
+                "Agent reported an error during operation.".to_string(),
+            )
+        }
+    }
+}
+
+impl<T: std::fmt::Debug> From<ApiError<T>> for AgentError {
+    fn from(err: ApiError<T>) -> Self {
+        match err {
+            ApiError::ResponseError(resp) => AgentError::from(resp),
+            ApiError::Io(err) => AgentError::ApplicationFailed(
+                format!("IO error during agent communication: {}", err),
+                "Failed to communicate with the agent.".to_string(),
+            ),
+            ApiError::Reqwest(err) => AgentError::ApplicationFailed(
+                format!("Reqwest error during agent communication: {}", err),
+                "Failed to communicate with the agent.".to_string(),
+            ),
+            ApiError::Serde(err) => AgentError::ApplicationFailed(
+                format!("Serialization error during agent communication: {}", err),
+                "Failed to communicate with the agent.".to_string(),
+            ),
+        }
+    }
+}
+
+#[cfg_attr(test, mockall::automock)]
+#[async_trait::async_trait]
+pub trait AgentService: Send + Sync {
+    #[allow(dead_code)]
+    fn get_client(&self) -> Arc<ApiClient>;
+
+    // TODO: improve error handling and reporting, error reasons
+    // validate configurations that has been created/updated before the given timestamp
+    #[allow(dead_code)]
+    async fn validate(&self, config: &str) -> Result<(), AgentError>;
+    // validate and apply configurations that has been created/updated before the given timestamp
+    async fn apply(&self, config: &str) -> Result<(), AgentError>;
+}
+
+pub struct AgentServiceImpl {
     client: Arc<ApiClient>,
 }
 
+impl AgentServiceImpl {
+    pub fn new(config: impl Into<Arc<Configuration>>) -> Self {
+        let client = ApiClient::new(config.into());
+        AgentServiceImpl {
+            client: Arc::new(client),
+        }
+    }
+}
+
 impl From<AgentSettings> for Configuration {
     fn from(settings: AgentSettings) -> Self {
         let mut config = Configuration::default();
@@ -27,17 +117,73 @@ impl From<AgentSettings> for Configuration {
     }
 }
 
-impl AgentService {
-    pub fn new(config: impl Into<Arc<Configuration>>) -> Self {
-        let client = ApiClient::new(config.into());
-        AgentService {
-            client: Arc::new(client),
-        }
+#[async_trait::async_trait]
+impl AgentService for AgentServiceImpl {
+    fn get_client(&self) -> Arc<ApiClient> {
+        Arc::clone(&self.client)
     }
 
-    #[allow(dead_code)]
-    pub fn get_client(&self) -> Arc<ApiClient> {
-        Arc::clone(&self.client)
+    async fn validate(&self, config: &str) -> Result<(), AgentError> {
+        let timestamp = chrono::Utc::now().timestamp_millis();
+        let name = Self::get_config_name(true);
+        self._validate(&name, timestamp, config).await
+    }
+
+    async fn apply(&self, config: &str) -> Result<(), AgentError> {
+        let timestamp = chrono::Utc::now().timestamp_millis();
+        let name = Self::get_config_name(false);
+        self._validate(&name, timestamp, config).await?;
+        self._apply(&name, timestamp).await
+    }
+}
+
+impl AgentServiceImpl {
+    fn get_config_name(is_validate_only: bool) -> String {
+        format!(
+            "nginx_config_{}{}",
+            if is_validate_only {
+                "validation_"
+            } else {
+                "application_"
+            },
+            uuid::Uuid::new_v4()
+        )
+    }
+
+    async fn _validate(&self, name: &str, timestamp: i64, config: &str) -> Result<(), AgentError> {
+        let api = self.client.nginx_agent_api();
+
+        api.write_config(WriteConfigParams {
+            write_config_body: WriteConfigBody {
+                config_name: name.to_string(),
+                content: config.to_string(),
+                timestamp,
+            },
+        })
+        .await?;
+
+        api.validate(ValidateParams {
+            validate_body: ValidateBody {
+                config_name: name.to_string(),
+                timestamp,
+            },
+        })
+        .await?;
+
+        Ok(())
+    }
+
+    async fn _apply(&self, name: &str, timestamp: i64) -> Result<(), AgentError> {
+        let api = self.client.nginx_agent_api();
+        api.validate_and_reload(ValidateAndReloadParams {
+            validate_and_reload_body: ValidateAndReloadBody {
+                config_name: name.to_string(),
+                timestamp,
+            },
+        })
+        .await?;
+
+        Ok(())
     }
 }
 
@@ -56,7 +202,7 @@ mod tests {
     #[test]
     fn test_agent_service_creation() {
         let config = Configuration::default();
-        let service = AgentService::new(config);
+        let service = AgentServiceImpl::new(config);
         let client = service.get_client();
         assert!(Arc::ptr_eq(&client, &service.client));
     }