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// APCore Protocol — Middleware manager
// Spec reference: Middleware pipeline execution
use std::sync::Arc;
use parking_lot::Mutex;
use super::base::Middleware;
use crate::context::Context;
use crate::errors::{ErrorCode, ModuleError};
/// Manages an ordered pipeline of middleware.
///
/// Thread-safe: internal list is protected by a Mutex. All execution methods
/// clone the Arc pointers out of the mutex before iterating so the lock is
/// never held across `.await` points.
#[derive(Debug)]
pub struct MiddlewareManager {
middlewares: Mutex<Vec<Arc<dyn Middleware>>>,
}
impl MiddlewareManager {
/// Create a new empty middleware manager.
#[must_use]
pub fn new() -> Self {
Self {
middlewares: Mutex::new(vec![]),
}
}
/// Add a middleware to the pipeline.
///
/// Middlewares are maintained in sorted order by priority (higher first).
/// Among middlewares with the same priority, registration order is preserved.
///
/// Returns an error if the middleware's priority exceeds 1000 (the spec-defined
/// maximum from section 11.2).
///
/// Takes `&self` — the internal list is protected by a `Mutex`, so mutation
/// is possible through a shared reference. This allows `MiddlewareManager`
/// to be held as `Arc<MiddlewareManager>` and mutated without `Arc::get_mut`
/// hacks, even after the `Arc` has been cloned into pipeline contexts.
pub fn add(&self, middleware: Box<dyn Middleware>) -> Result<(), ModuleError> {
let priority = middleware.priority();
if priority > 1000 {
tracing::warn!(
middleware = middleware.name(),
priority = priority,
"Middleware rejected: priority {} exceeds maximum 1000",
priority,
);
return Err(ModuleError::new(
ErrorCode::GeneralInvalidInput,
format!(
"Middleware '{}' has priority {} which exceeds the maximum allowed value of 1000",
middleware.name(),
priority,
),
));
}
let mut mws = self.middlewares.lock();
let arc: Arc<dyn Middleware> = Arc::from(middleware);
// Find the first position where existing priority is strictly less than
// the new priority. Insert before that position to maintain stable
// ordering (later registrations go after earlier ones at same priority).
let pos = mws
.iter()
.position(|m| m.priority() < priority)
.unwrap_or(mws.len());
mws.insert(pos, arc);
Ok(())
}
/// Remove the first middleware matching the given name.
///
/// Removes only the first match (not all), matching Python's
/// identity-based semantics which also removes exactly one instance.
///
/// Takes `&self` — mutation goes through the internal `Mutex`.
pub fn remove(&self, name: &str) -> bool {
let mut mws = self.middlewares.lock();
let pos = mws.iter().position(|m| m.name() == name);
if let Some(i) = pos {
mws.remove(i);
true
} else {
false
}
}
/// Return a snapshot of middleware names in pipeline order.
pub fn snapshot(&self) -> Vec<String> {
let mws = self.middlewares.lock();
mws.iter().map(|m| m.name().to_string()).collect()
}
/// Run the before hooks for all middlewares in order.
///
/// Returns the (possibly modified) input and the list of indices of
/// middlewares that were successfully executed (used by `execute_on_error`
/// for onion-model unwinding).
///
/// If a middleware's `before()` fails, wraps the error as a
/// `MiddlewareChainError` and returns it. The `executed` list allows
/// callers to run `on_error` only on middlewares that actually ran.
pub async fn execute_before(
&self,
module_id: &str,
mut inputs: serde_json::Value,
ctx: &Context<serde_json::Value>,
) -> Result<(serde_json::Value, Vec<usize>), ModuleError> {
// Clone Arc pointers so the mutex is not held across .await points.
let mws: Vec<Arc<dyn Middleware>> = {
let guard = self.middlewares.lock();
guard.iter().map(Arc::clone).collect()
};
let mut executed: Vec<usize> = Vec::new();
for (i, mw) in mws.iter().enumerate() {
// Push BEFORE calling before() so the failing middleware is included in
// executed — enabling on_error self-heal (mirrors Python/TS behaviour).
executed.push(i);
match mw.before(module_id, inputs.clone(), ctx).await {
Ok(Some(modified)) => {
inputs = modified;
}
Ok(None) => {
// No modification — keep current inputs
}
Err(e) => {
return Err(ModuleError::new(
ErrorCode::MiddlewareChainError,
e.message.clone(),
)
.with_cause(format!(
"Middleware '{}' before() failed: {}",
mw.name(),
e
)));
}
}
}
Ok((inputs, executed))
}
/// Run the after hooks for all middlewares in reverse order (onion model).
///
/// If a middleware returns `Some(value)`, the output is replaced.
/// If it returns `None`, the current output is kept unchanged.
pub async fn execute_after(
&self,
module_id: &str,
inputs: serde_json::Value,
mut output: serde_json::Value,
ctx: &Context<serde_json::Value>,
) -> Result<serde_json::Value, ModuleError> {
// Clone Arc pointers so the mutex is not held across .await points.
let mws: Vec<Arc<dyn Middleware>> = {
let guard = self.middlewares.lock();
guard.iter().map(Arc::clone).collect()
};
for mw in mws.iter().rev() {
if let Some(modified) = mw
.after(module_id, inputs.clone(), output.clone(), ctx)
.await?
{
output = modified;
} else {
// No modification — keep current output
}
}
Ok(output)
}
/// Run the `on_error` hooks in reverse order over the middlewares that
/// were executed during `execute_before`.
///
/// Returns `Some(recovery)` if any middleware provides a recovery value.
/// Returns `None` if no handler recovers.
///
/// Early-returns on the first recovery value — subsequent middlewares'
/// `on_error` hooks are NOT called after recovery (mirrors Python/TS).
pub async fn execute_on_error(
&self,
module_id: &str,
inputs: serde_json::Value,
error: &ModuleError,
ctx: &Context<serde_json::Value>,
executed: &[usize],
) -> Option<serde_json::Value> {
// Clone Arc pointers so the mutex is not held across .await points.
let mws: Vec<Arc<dyn Middleware>> = {
let guard = self.middlewares.lock();
guard.iter().map(Arc::clone).collect()
};
for &i in executed.iter().rev() {
if let Some(mw) = mws.get(i) {
match mw.on_error(module_id, inputs.clone(), error, ctx).await {
Ok(Some(value)) => {
// Early-return on first recovery (matches Python/TS semantics).
return Some(value);
}
Ok(None) => {
// No recovery from this middleware — continue
}
Err(e) => {
tracing::error!("Middleware '{}' on_error failed: {}", mw.name(), e);
}
}
}
}
None
}
}
impl Default for MiddlewareManager {
fn default() -> Self {
Self::new()
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::context::Context;
use crate::errors::ModuleError;
use async_trait::async_trait;
/// Simple test middleware with configurable name and priority.
#[derive(Debug)]
struct TestMiddleware {
mw_name: String,
mw_priority: u16,
}
impl TestMiddleware {
fn new(name: &str, priority: u16) -> Self {
Self {
mw_name: name.to_string(),
mw_priority: priority,
}
}
fn boxed(name: &str, priority: u16) -> Box<Self> {
Box::new(Self::new(name, priority))
}
}
#[async_trait]
impl Middleware for TestMiddleware {
fn name(&self) -> &str {
&self.mw_name
}
fn priority(&self) -> u16 {
self.mw_priority
}
async fn before(
&self,
_module_id: &str,
_inputs: serde_json::Value,
_ctx: &Context<serde_json::Value>,
) -> Result<Option<serde_json::Value>, ModuleError> {
Ok(None)
}
async fn after(
&self,
_module_id: &str,
_inputs: serde_json::Value,
_output: serde_json::Value,
_ctx: &Context<serde_json::Value>,
) -> Result<Option<serde_json::Value>, ModuleError> {
Ok(None)
}
async fn on_error(
&self,
_module_id: &str,
_inputs: serde_json::Value,
_error: &ModuleError,
_ctx: &Context<serde_json::Value>,
) -> Result<Option<serde_json::Value>, ModuleError> {
Ok(None)
}
}
#[test]
fn test_higher_priority_executes_first_in_before() {
let mgr = MiddlewareManager::new();
mgr.add(TestMiddleware::boxed("low", 1)).unwrap();
mgr.add(TestMiddleware::boxed("high", 10)).unwrap();
mgr.add(TestMiddleware::boxed("mid", 5)).unwrap();
let names = mgr.snapshot();
assert_eq!(names, vec!["high", "mid", "low"]);
}
#[test]
fn test_equal_priority_preserves_registration_order() {
let mgr = MiddlewareManager::new();
mgr.add(TestMiddleware::boxed("first", 5)).unwrap();
mgr.add(TestMiddleware::boxed("second", 5)).unwrap();
mgr.add(TestMiddleware::boxed("third", 5)).unwrap();
let names = mgr.snapshot();
assert_eq!(names, vec!["first", "second", "third"]);
}
#[test]
fn test_default_priority_orders_after_explicit_priority() {
let mgr = MiddlewareManager::new();
mgr.add(TestMiddleware::boxed("default_a", 0)).unwrap();
mgr.add(TestMiddleware::boxed("explicit", 1)).unwrap();
mgr.add(TestMiddleware::boxed("default_b", 0)).unwrap();
let names = mgr.snapshot();
assert_eq!(names, vec!["explicit", "default_a", "default_b"]);
}
#[test]
fn test_snapshot_reflects_priority_sorted_order() {
let mgr = MiddlewareManager::new();
mgr.add(TestMiddleware::boxed("d", 0)).unwrap();
mgr.add(TestMiddleware::boxed("a", 100)).unwrap();
mgr.add(TestMiddleware::boxed("c", 5)).unwrap();
mgr.add(TestMiddleware::boxed("b", 50)).unwrap();
let names = mgr.snapshot();
assert_eq!(names, vec!["a", "b", "c", "d"]);
}
#[test]
fn test_add_rejects_priority_above_1000() {
let mgr = MiddlewareManager::new();
let result = mgr.add(TestMiddleware::boxed("over_limit", 1001));
assert!(result.is_err());
let err = result.unwrap_err();
assert!(
err.message.contains("exceeds the maximum"),
"Expected error about priority limit, got: {}",
err.message,
);
// Pipeline should be empty — the middleware was not added.
assert!(mgr.snapshot().is_empty());
}
#[test]
fn test_add_accepts_priority_at_1000() {
let mgr = MiddlewareManager::new();
mgr.add(TestMiddleware::boxed("at_limit", 1000)).unwrap();
assert_eq!(mgr.snapshot(), vec!["at_limit"]);
}
}