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use super::PushStream;
use crate::data::{Fragment, FragmentIds, Peer};
use crate::error::Error;
use async_trait::async_trait;
use futures::prelude::*;

/// Interface for the blockchain node service implementation responsible for
/// exchanging fragments that make up a future block.
#[async_trait]
pub trait FragmentService {
    /// The type of an asynchronous stream that provides blocks in
    /// response to `get_fragments` method.
    type GetFragmentsStream: Stream<Item = Result<Fragment, Error>> + Send + Sync;

    /// Serves a request to retrieve blocks identified by the list of `ids`
    /// Resloves to a stream of blocks to send to the remote client peer.
    async fn get_fragments(&self, ids: FragmentIds) -> Result<Self::GetFragmentsStream, Error>;

    /// The type of outbound asynchronous streams returned by the
    /// `subscription` method.
    type SubscriptionStream: Stream<Item = Result<Fragment, Error>> + Send + Sync;

    /// Called by the protocol implementation to establish a
    /// bidirectional subscription stream.
    /// The inbound stream is passed to the asynchronous method,
    /// which resolves to the outbound stream.
    async fn fragment_subscription(
        &self,
        subscriber: Peer,
        stream: PushStream<Fragment>,
    ) -> Result<Self::SubscriptionStream, Error>;
}