//! # Introduction
//!
//! A struct for recording execution status of async tasks with async methods.
//!
//! Functions:
//! - Able to host `Future`s and query whether they are
//! **not found**, **running**, **successful**, **failed**, or **revoking**.
//! - Able to host `Future`s to revoke the succeeded `Future`s and make them **not found**.
//!
//! Dependency:
//! - Depend on `tokio` with feature `rt`, so cannot use other async runtimes.
//! - Depend on [scc](https://crates.io/crates/scc) for async `HashMap`.
//!
//! Use this crate if:
//! - Easy to generate an **unique** `task_id` (not necessarily `String`) for a future (task).
//! - Don't want tasks with the same `task_id` to succeed more than once.
//! - Require **linearizability**.
//! - Want to revoke a task, and don't want the revoking to succeed more than once.
//!
//! A recorder can only use **single** `task_id` type. The type of `task_id` should be:
//! - `Eq + Hash + Clone + Send + Sync + 'static`
//! - Cheap to clone (sometimes can use `Arc`) (only cloned once when launch).
//!
//! > [async_tasks_recorder](https://crates.io/crates/async_tasks_recorder)
//! is another implement depending on `HashSet`,
//! which is easier to iterate every task in the same state.
//! But you should not use that crate if you only focus on iterate only once state.
//! Instead, you can collect the tasks in certain state into an external `Arc<HashSet>`.
//!
//! # State Transition Diagram
//!
//! ```txt
//!     ┌------- Revoking ←-----┐
//!     ↓                       |
//! NotFound --> Working --> Success
//!               ↑ |
//!               | ↓
//!             Failed
//! ```
//!
//! - Can only launch when `NotFound` or `Failed`.
//! - Can only revoke when `Success`.
//!
//! # Usage
//!
//! Just look at the [`AsyncTasksRecorder`](AsyncTasksRecorder).
//!

mod models;
mod recorder;

pub use models::*;
pub use recorder::*;

pub use scc;