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use super::Backend;

use anyhow::Result;

/// [`Middleware`]s are used to Modify RPCs or to add extra functionality to the framework.
///
/// # Outgoing RPCs
/// The outgoing [`Call`](crate::Call)<[`Intermediate`](Backend::Intermediate)`>`s are processed by the [`wrap_call`](Middleware::wrap_call) function and passed on.
/// The incomming [`Reply`](crate::Reply)<[`Intermediate`](Backend::Intermediate)`>`s are processed by the [`unwrap_reply`](Middleware::unwrap_reply) function and passed on.
///
/// # Incomming RPCs
/// The incomming [`Call`](crate::Call)<[`Intermediate`](Backend::Intermediate)`>`s are processed by the [`unwrap_call`](Middleware::unwrap_call) function and passed on.
/// The outgoing [`Reply`](crate::Reply)<[`Intermediate`](Backend::Intermediate)`>`s are processed by the [`wrap_reply`](Middleware::wrap_reply) function and passed on.
///
/// # Examples
/// For examples look at the provided [`Middleware`]s:
/// * [`Authentication`](/merfolk_middleware_authentication)
/// * [`Router`](/merfolk_middleware_router)

pub trait Middleware: Send {
  type Backend: Backend;

  /// Wraps the outgoing call [`Call`](crate::Call)<[`Intermediate`](Backend::Intermediate)`>`
  fn wrap_call(&self, call: Result<crate::Call<<Self::Backend as Backend>::Intermediate>>) -> Result<crate::Call<<Self::Backend as Backend>::Intermediate>>;

  /// Wraps the outgoing reply [`Reply`](crate::Reply)<[`Intermediate`](Backend::Intermediate)`>`
  fn wrap_reply(&self, call: Result<crate::Reply<<Self::Backend as Backend>::Intermediate>>) -> Result<crate::Reply<<Self::Backend as Backend>::Intermediate>>;

  /// Unwraps the incomming call [`Call`](crate::Call)<[`Intermediate`](Backend::Intermediate)`>`
  fn unwrap_call(&self, reply: Result<crate::Call<<Self::Backend as Backend>::Intermediate>>) -> Result<crate::Call<<Self::Backend as Backend>::Intermediate>>;

  /// Unwraps the imcomming reply [`Reply`](crate::Reply)<[`Intermediate`](Backend::Intermediate)`>`
  fn unwrap_reply(&self, reply: Result<crate::Reply<<Self::Backend as Backend>::Intermediate>>) -> Result<crate::Reply<<Self::Backend as Backend>::Intermediate>>;

  /// return self as Any. Needed for downcasting when accessing a Middleware through [`Mer`](crate::Mer).
  ///
  /// implement like this `fn as_any(&mut self) -> &mut dyn core::any::Any { self }`
  fn as_any(&mut self) -> &mut dyn core::any::Any;
}