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//! Method type for the RPC system.
use std::collections::HashSet;
use derive_deftly::define_derive_deftly;
use downcast_rs::Downcast;
use once_cell::sync::Lazy;
/// The parameters and method name associated with a given Request.
///
/// We use [`typetag`] here so that we define `Method`s in other crates.
///
/// Use [`derive_deftly(DynMethod)`](derive_deftly_template_DynMethod)
/// for a template to declare one of these.
///
/// # Note
///
/// In order to comply with our spec, all Methods' data must be represented as a json
/// object.
//
// TODO RPC: Possible issue here is that, if this trait is public, anybody outside
// of Arti can use this trait to add new methods to the RPC engine. Should we
// care?
#[typetag::deserialize(tag = "method", content = "params")]
pub trait DynMethod: std::fmt::Debug + Send + Downcast {}
downcast_rs::impl_downcast!(DynMethod);
/// A typed method, used to ensure that all implementations of a method have the
/// same success and updates types.
///
/// Prefer to implement this trait, rather than `DynMethod`. (`DynMethod`
/// represents a type-erased method, with statically-unknown `Output` and
/// `Update` types.)
pub trait Method: DynMethod {
/// A type returned by this method on success.
type Output: serde::Serialize + Send + 'static;
/// A type sent by this method on updates.
///
/// If this method will never send updates, use the uninhabited
/// [`NoUpdates`] type.
type Update: serde::Serialize + Send + 'static;
}
/// An uninhabited type, used to indicate that a given method will never send
/// updates.
#[derive(serde::Serialize)]
#[allow(clippy::exhaustive_enums)]
pub enum NoUpdates {}
/// A method we're registering.
///
/// This struct's methods are public so it can be constructed from
/// `decl_method!`.
///
/// If you construct it yourself, you'll be in trouble. But you already knew
/// that, since you're looking at a `doc(hidden)` thing.
#[doc(hidden)]
#[allow(clippy::exhaustive_structs)]
pub struct MethodInfo_ {
/// The name of the method.
pub method_name: &'static str,
}
inventory::collect!(MethodInfo_);
define_derive_deftly! {
/// Declare that one or more space-separated types should be considered
/// as dynamically dispatchable RPC methods.
///
/// # Example
///
/// ```
/// use tor_rpcbase::{self as rpc, templates::*};
/// use derive_deftly::Deftly;
///
/// #[derive(Debug, serde::Deserialize, Deftly)]
/// #[derive_deftly(rpc::DynMethod)]
/// #[deftly(rpc(method_name = "x-example:castigate"))]
/// struct Castigate {
/// severity: f64,
/// offenses: Vec<String>,
/// accomplice: Option<rpc::ObjectId>,
/// }
///
/// impl rpc::Method for Castigate {
/// type Output = String;
/// type Update = rpc::NoUpdates;
/// }
/// ```
///
/// # Limitations
///
/// For now you'll need to import the `typetag` crate; unfortunately, it doesn't
/// yet behave well when used where it is not in scope as `typetag`.
pub DynMethod =
#[$crate::typetag::deserialize(name = ${tmeta(rpc(method_name)) as str})]
// Note that we do not support generics in method types.
// If we did, we would have to give each instantiation type its own method name.
impl $crate::DynMethod for $ttype {}
$crate::inventory::submit! {
$crate::MethodInfo_ { method_name : ${tmeta(rpc(method_name)) as str} }
}
}
pub use derive_deftly_template_DynMethod;
/// Return true if `name` is the name of some method.
pub fn is_method_name(name: &str) -> bool {
/// Lazy set of all method names.
static METHOD_NAMES: Lazy<HashSet<&'static str>> = Lazy::new(|| iter_method_names().collect());
METHOD_NAMES.contains(name)
}
/// Return an iterator that yields every registered method name.
///
/// Used (e.g.) to enforce syntactic requirements on method names.
pub fn iter_method_names() -> impl Iterator<Item = &'static str> {
inventory::iter::<MethodInfo_>().map(|mi| mi.method_name)
}
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