ruststream 0.2.3

//! The contract a `#[subscriber]`-generated type implements so it can be mounted with
//! [`BrokerScope::include`](super::BrokerScope::include).

use super::handler::Handler;

/// A handler definition produced by the `#[subscriber]` macro.
///
/// It bundles a typed [`Handler`] with the subscription [`Source`](Self::Source) it binds to, so
/// [`BrokerScope::include`](super::BrokerScope::include) can subscribe and wire decoding without the
/// caller repeating anything. The source is a [`Name`](crate::Name) for `#[subscriber("topic")]`, or
/// a broker descriptor for `#[subscriber(RedisStream::new(..))]`. The generated type is itself the
/// handler, so [`Handler`](Self::Handler) is usually `Self`.
pub trait SubscriberDef: Sized {
    /// The decoded message type the handler consumes.
    type Input;

    /// The concrete handler type over [`Input`](Self::Input).
    type Handler: Handler<Self::Input>;

    /// The subscription source this handler binds to. The bound to
    /// [`SubscriptionSource`](crate::SubscriptionSource) for the target broker is applied where the
    /// def is mounted, not on the trait, so a def can name any broker's descriptor.
    type Source;

    /// Builds the subscription source (fresh each call).
    fn source(&self) -> Self::Source;

    /// An optional human description (from the handler's doc comment), for `AsyncAPI`.
    fn description(&self) -> Option<&str> {
        None
    }

    /// The input type's serialized JSON Schema, when it implements [`schemars::JsonSchema`] and the
    /// `asyncapi` feature is on. The macro fills this in; the default omits it.
    fn input_schema(&self) -> Option<String> {
        None
    }

    /// Consumes the definition, returning the handler.
    fn into_handler(self) -> Self::Handler;
}