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//! A peer connection service wrapper type to handle load tracking and provide access to the
//! reported protocol version.

use std::{
    sync::Arc,
    task::{Context, Poll},
};

use tower::{
    load::{Load, PeakEwma},
    Service,
};

use crate::{
    constants::{EWMA_DECAY_TIME_NANOS, EWMA_DEFAULT_RTT},
    peer::{Client, ConnectionInfo},
    protocol::external::types::Version,
};

/// A client service wrapper that keeps track of its load.
///
/// It also keeps track of the peer's reported protocol version.
#[derive(Debug)]
pub struct LoadTrackedClient {
    /// A service representing a connected peer, wrapped in a load tracker.
    service: PeakEwma<Client>,

    /// The metadata for the connected peer `service`.
    connection_info: Arc<ConnectionInfo>,
}

/// Create a new [`LoadTrackedClient`] wrapping the provided `client` service.
impl From<Client> for LoadTrackedClient {
    fn from(client: Client) -> Self {
        let connection_info = client.connection_info.clone();

        let service = PeakEwma::new(
            client,
            EWMA_DEFAULT_RTT,
            EWMA_DECAY_TIME_NANOS,
            tower::load::CompleteOnResponse::default(),
        );

        LoadTrackedClient {
            service,
            connection_info,
        }
    }
}

impl LoadTrackedClient {
    /// Retrieve the peer's reported protocol version.
    pub fn remote_version(&self) -> Version {
        self.connection_info.remote.version
    }
}

impl<Request> Service<Request> for LoadTrackedClient
where
    Client: Service<Request>,
{
    type Response = <Client as Service<Request>>::Response;
    type Error = <Client as Service<Request>>::Error;
    type Future = <PeakEwma<Client> as Service<Request>>::Future;

    fn poll_ready(&mut self, context: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
        self.service.poll_ready(context)
    }

    fn call(&mut self, request: Request) -> Self::Future {
        self.service.call(request)
    }
}

impl Load for LoadTrackedClient {
    type Metric = <PeakEwma<Client> as Load>::Metric;

    fn load(&self) -> Self::Metric {
        self.service.load()
    }
}