p2panda-sync 0.7.0

Local-first sync for append-only logs and traits to build your own
Documentation 
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// SPDX-License-Identifier: MIT OR Apache-2.0

//! Interfaces for implementing sync protocols and managers.
use std::error::Error as StdError;
use std::fmt::Debug;
use std::pin::Pin;

use futures_util::Sink;
use futures_util::Stream;
use serde::{Deserialize, Serialize};

use crate::{FromSync, SessionConfig, ToSync};

/// Generic protocol interface which runs over a sink and stream pair.
pub trait Protocol {
    type Output;
    type Error: StdError + Send + Sync + 'static;
    type Message: Serialize + for<'a> Deserialize<'a>;

    fn run(
        self,
        sink: &mut (impl Sink<Self::Message, Error = impl Debug> + Unpin),
        stream: &mut (impl Stream<Item = Result<Self::Message, impl Debug>> + Unpin),
    ) -> impl Future<Output = Result<Self::Output, Self::Error>>;
}

/// Interface for managing sync sessions and consuming events they emit.
#[allow(clippy::type_complexity)]
pub trait Manager<T> {
    type Protocol: Protocol + Send + 'static;
    type Args: Clone + Send + 'static;
    type Message: Clone + Send + 'static;
    type Event: Clone + Debug + Send + 'static;
    type Error: StdError + Send + Sync + 'static;

    fn from_args(args: Self::Args) -> Self;

    /// Instantiate a new sync session.
    fn session(
        &mut self,
        session_id: u64,
        config: &SessionConfig<T>,
    ) -> impl Future<Output = Self::Protocol>;

    /// Retrieve a send handle to an already existing sync session.
    fn session_handle(
        &self,
        session_id: u64,
    ) -> impl Future<Output = Option<Pin<Box<dyn Sink<ToSync<Self::Message>, Error = Self::Error>>>>>;

    /// Subscribe to the manager event stream.
    fn subscribe(&mut self) -> impl Stream<Item = FromSync<Self::Event>> + Send + Unpin + 'static;
}