//! Streaming server for Mastodon
//!
//!
//! This server provides live, streaming updates for Mastodon clients.  Specifically, when a server
//! is running this sever, Mastodon clients can use either Server Sent Events or WebSockets to
//! connect to the server with the API described [in Mastodon's public API
//! documentation](https://docs.joinmastodon.org/api/streaming/).
//!
//! # Data Flow
//! * **Parsing the client request**
//! When the client request first comes in, it is parsed based on the endpoint it targets (for
//! server sent events), its query parameters, and its headers (for WebSocket).  Based on this
//! data, we authenticate the user, retrieve relevant user data from Postgres, and determine the
//! timeline targeted by the request.  Successfully parsing the client request results in generating
//! a `User` and target `timeline` for the request.  If any requests are invalid/not authorized, we
//! reject them in this stage.
//! * **Streaming update from Redis to the client**:
//! After the user request is parsed, we pass the `User` and `timeline` data on to the
//! `ClientAgent`.  The `ClientAgent` is responsible for communicating the user's request to the
//! `Receiver`, polling the `Receiver` for any updates, and then for wording those updates on to the
//! client.  The `Receiver`, in tern, is responsible for managing the Redis subscriptions,
//! periodically polling Redis, and sorting the replies from Redis into queues for when it is polled
//! by the `ClientAgent`.
//!
//! # Concurrency
//! The `Receiver` is created when the server is first initialized, and there is only one
//! `Receiver`.  Thus, the `Receiver` is a potential bottleneck.  On the other hand, each
//! client request results in a new green thread, which spawns its own `ClientAgent`.  Thus,
//! their will be many `ClientAgent`s polling a single `Receiver`.  Accordingly, it is very
//! important that polling the `Receiver` remain as fast as possible.  It is less important
//! that the `Receiver`'s poll of Redis be fast, since there will only ever be one
//! `Receiver`.
//!
//! # Configuration
//! By default, the server uses config values from the `config.rs` module; these values can be
//! overwritten with environmental variables or in the `.env` file.  The most important settings
//! for performance control the frequency with which the `ClientAgent` polls the `Receiver` and
//! the frequency with which the `Receiver` polls Redis.
//!
pub mod config;
pub mod parse_client_request;
pub mod redis_to_client_stream;