Add A2A service skeleton and error types

Add a skeleton for the A2A agent service: new modules src/create.rs (A2aAgentCreate) and src/read.rs (A2aAgentRead), src/errors.rs (A2AAgentError enum with thiserror-based Display tests), and src/service.rs (A2aAgentService stub with todo!() methods). Remove the placeholder main.rs and update lib.rs to register the new modules in the Python module. Also add thiserror as a dependency in the workspace and mark it in the a2a_service Cargo.toml. Provides scaffolding and tests for error handling; implementation details are left as TODOs.

Author: lucarlig

mcpgateway_rust/Cargo.lock

@@ -28,6 +28,9 @@ tokio = { version = "1.49", features = ["full"] }
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 
+# Error handling
+thiserror = "2.0"
+
 [package]
 name = "mcpgateway_rust"
 version.workspace = true

mcpgateway_rust/Cargo.toml

@@ -17,5 +17,6 @@ reqwest.workspace = true
 tokio.workspace = true
 serde.workspace = true
 serde_json.workspace = true
+thiserror.workspace = true
 
 [dev-dependencies]

mcpgateway_rust/services/a2a_service/Cargo.toml

@@ -0,0 +1,7 @@
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Serialize, Deserialize)]
+pub struct A2aAgentCreate {
+    name: String,
+    // Other fields from schema
+}

mcpgateway_rust/services/a2a_service/src/create.rs

@@ -0,0 +1,84 @@
+use thiserror::Error;
+
+/// Base error type for A2A agent-related errors.
+#[derive(Debug, Clone, PartialEq, Eq, Error)]
+pub enum A2AAgentError {
+    /// Raised when a requested A2A agent is not found.
+    #[error("A2A agent not found: {0}")]
+    NotFound(String),
+
+    /// Raised when an A2A agent name conflicts with an existing one.
+    #[error(
+        "A2A agent name conflict: {name} (active: {is_active}, agent_id: {agent_id:?}, visibility: {visibility})"
+    )]
+    NameConflict {
+        name: String,
+        is_active: bool,
+        agent_id: Option<String>,
+        visibility: String,
+    },
+
+    /// Generic A2A agent operation error.
+    #[error("A2A agent error: {0}")]
+    Operation(String),
+
+    /// Permission denied error.
+    #[error("Permission denied: {0}")]
+    PermissionDenied(String),
+
+    /// Invalid value error.
+    #[error("Invalid value: {0}")]
+    ValueError(String),
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_not_found_error_display() {
+        let error = A2AAgentError::NotFound("agent-123".to_string());
+        assert_eq!(error.to_string(), "A2A agent not found: agent-123");
+    }
+
+    #[test]
+    fn test_name_conflict_error_display() {
+        let error = A2AAgentError::NameConflict {
+            name: "test-agent".to_string(),
+            is_active: true,
+            agent_id: Some("agent-456".to_string()),
+            visibility: "public".to_string(),
+        };
+        assert_eq!(
+            error.to_string(),
+            "A2A agent name conflict: test-agent (active: true, agent_id: Some(\"agent-456\"), visibility: public)"
+        );
+    }
+
+    #[test]
+    fn test_operation_error_display() {
+        let error = A2AAgentError::Operation("Failed to invoke agent".to_string());
+        assert_eq!(error.to_string(), "A2A agent error: Failed to invoke agent");
+    }
+
+    #[test]
+    fn test_permission_denied_error_display() {
+        let error =
+            A2AAgentError::PermissionDenied("Only the owner can delete this agent".to_string());
+        assert_eq!(
+            error.to_string(),
+            "Permission denied: Only the owner can delete this agent"
+        );
+    }
+
+    #[test]
+    fn test_value_error_display() {
+        let error = A2AAgentError::ValueError("Invalid passthrough_headers format".to_string());
+        assert_eq!(
+            error.to_string(),
+            "Invalid value: Invalid passthrough_headers format"
+        );
+    }
+}
+
+// Made with Bob

mcpgateway_rust/services/a2a_service/src/errors.rs

@@ -4,10 +4,15 @@
 // A2A Service - High-performance agent invocation with PyO3 bindings
 //
 // This module provides Rust-accelerated HTTP invocation for A2A agents,
-// offering 10-50x performance improvements over Python asyncio/httpx.
+// offering TODO: performance improvements over Python asyncio/httpx.
 
 use pyo3::prelude::*;
 
+mod create;
+mod errors;
+mod read;
+mod service;
+
 /// A2A Service module
 #[pymodule]
 pub fn a2a_service(m: &Bound<'_, PyModule>) -> PyResult<()> {

mcpgateway_rust/services/a2a_service/src/lib.rs

@@ -0,0 +1,8 @@
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Serialize, Deserialize)]
+pub struct A2aAgentRead {
+    id: String,
+    name: String,
+    // Other fields
+}

mcpgateway_rust/services/a2a_service/src/main.rs

@@ -0,0 +1,35 @@
+use super::create::A2aAgentCreate;
+use super::errors::A2AAgentError;
+use super::read::A2aAgentRead;
+
+struct A2aAgentService {
+    initialized: bool,
+    // Add event_streams: Vec<...> if needed
+}
+
+impl A2aAgentService {
+    pub fn new() -> Self {
+        todo!()
+    }
+
+    pub async fn initialize(&mut self) {
+        todo!()
+    }
+
+    pub async fn shutdown(&mut self) {
+        todo!()
+    }
+
+    pub async fn register_agent(
+        &self,
+        // db?
+        agent_data: A2aAgentCreate,
+        // Other optional args
+    ) -> Result<A2aAgentRead, A2AAgentError> {
+        todo!()
+    }
+
+    // TODO: Implement other methods similarly: list, get, update, delete, etc.
+    // For visibility filters, use SQL WHERE clauses in queries.
+    // For batch ops, use sqlx batches.
+}