FRAME: General System for Recognizing and Executing Service Work

frame/support/src/traits.rs

@@ -116,6 +116,9 @@ pub use messages::{
 	ProcessMessageError, ServiceQueues, TransformOrigin,
 };
 
+pub mod tasks;
+pub use tasks::*;
+
 #[cfg(feature = "try-runtime")]
 mod try_runtime;
 #[cfg(feature = "try-runtime")]

frame/support/src/traits/tasks.rs

@@ -0,0 +1,43 @@
+// This file is part of Substrate.
+
+// Copyright (C) Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Contains the [`Task`] trait, which defines a general-purpose way for defining and executing
+//! service work, and supporting types.
+
+use codec::FullCodec;
+use sp_runtime::DispatchError;
+use sp_std::iter::Iterator;
+
+/// A general-purpose trait which defines a type of service work (i.e., work to performed by an
+/// off-chain worker) including methods for enumerating, validating, indexing, and running
+/// tasks of this type.
+pub trait Task: Sized + FullCodec {
+	type Enumeration: Iterator<Item = Self>;
+
+	/// Inspects the pallet's state and enumerates tasks of this type.
+	fn enumerate() -> Self::Enumeration;
+
+	/// Checks if a particular instance of this `Task` variant is a valid piece of work.
+	fn is_valid(&self) -> bool;
+
+	/// Returns the `task_index` (analogous to `call_index`, but for tasks) of this `Task`
+	/// variant.
+	fn task_index(&self) -> usize;
+
+	/// Performs the work for this particular `Task` variant.
+	fn run(&self) -> Result<(), DispatchError>;
+}