feat(xcm): Adds pallet to allow target parachains to receive fulfillments from acurast

pallets/acurast-xcm-receiver/Cargo.toml

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+[package]
+name = "pallet-acurast-xcm-receiver"
+authors = ["Papers AG"]
+description = "Pallet for defining the receiving logic from acurast parachain."
+version = "0.0.1"
+license = "Unlicense"
+homepage = "https://docs.acurast.com/"
+edition = "2021"
+publish = false
+repository = "https://github.com/acurast/"
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]
+
+[dependencies]
+codec = { package = "parity-scale-codec", version = "3.0.0", default-features = false, features = ["derive"] }
+
+# Benchmarks
+frame-benchmarking = { git = "https://github.com/paritytech/substrate", branch = "polkadot-v0.9.29", optional = true, default-features = false }
+
+# Substrate
+frame-support = { git = "https://github.com/paritytech/substrate", branch = "polkadot-v0.9.29", default-features = false }
+frame-system = { git = "https://github.com/paritytech/substrate", branch = "polkadot-v0.9.29", default-features = false }
+scale-info = { version = "2.0", default-features = false, features = [ "derive" ] }
+sp-std = { git = "https://github.com/paritytech/substrate", branch = "polkadot-v0.9.29", default-features = false }
+
+[dev-dependencies]
+sp-io = { git = "https://github.com/paritytech/substrate", branch = "polkadot-v0.9.29", default-features = false }
+sp-runtime = { git = "https://github.com/paritytech/substrate", branch = "polkadot-v0.9.29", default-features = false }
+sp-core = { git = "https://github.com/paritytech/substrate", branch = "polkadot-v0.9.29", default-features = false }
+# XCM
+xcm = { git = "https://github.com/paritytech/polkadot", branch = "release-v0.9.29" }
+xcm-builder = { git = "https://github.com/paritytech/polkadot", branch = "release-v0.9.29" }
+pallet-xcm = { git = "https://github.com/paritytech/polkadot", branch = "release-v0.9.29" }
+
+[features]
+default = ["std"]
+std = [
+	"codec/std",
+	"scale-info/std",
+	"frame-support/std",
+	"frame-system/std",
+	"frame-benchmarking/std",
+]
+
+runtime-benchmarks = ["frame-benchmarking/runtime-benchmarks"]
+try-runtime = ["frame-support/try-runtime"]

pallets/acurast-xcm-receiver/README.md

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+# Acurast XCM Receiver Pallet
+
+## 🚧🚧🚧 The project is still a work in progress 🚧🚧🚧
+
+## Introduction
+
+The `pallet-acurast-xcm-receiver` adds support for parachains to receive [XCM](https://wiki.polkadot.network/docs/learn-xcm) messages from [Acurast parachain](https://docs.acurast.com/).
+
+The Pallet exposes the following extrinsics.
+
+### fulfill
+
+Allows to post the fulfillment of a registered job. The `fulfill` call will fail if the job was not previously assigned to the origin. The fulfillment structure consists of:
+
+## Setup
+
+1. Add the following dependency to your Cargo manifest:
+
+```toml
+[dependencies]
+pallet-acurast-xcm-receiver = { git = "https://github.com/Acurast/acurast-core.git" }
+```
+
+2. Implement `pallet_acurast_xcm_receiver::Config` for your `Runtime` and add the Pallet:
+
+```rust
+/// Runtime example
+
+pub struct ParachainBarrier;
+impl pallet_acurast_xcm_receiver::traits::ParachainBarrier<Runtime> for ParachainBarrier {
+	fn ensure_xcm_origin(
+		origin: frame_system::pallet_prelude::OriginFor<Runtime>,
+	) -> Result<(), sp_runtime::DispatchError> {
+		// List of allowd parachains
+		let allowed_parachains = [
+			// The Acurast parachain identifier
+			xcm::opaque::latest::Junction::Parachain(2001),
+		];
+
+		// Ensure that the call comes from an xcm message
+		let location = pallet_xcm::ensure_xcm(origin)?;
+
+		let is_valid_origin = location
+			.interior()
+			.iter()
+			.any(|junction| allowed_parachains.contains(junction));
+
+		if !is_valid_origin {
+			return Err(sp_runtime::DispatchError::Other(
+				"MultiLocation not allowed.",
+			));
+		}
+
+		Ok(())
+	}
+}
+
+pub struct OnAcurastFulfillment;
+impl pallet_acurast_xcm_receiver::traits::OnFulfillment<Runtime> for OnAcurastFulfillment {
+	fn fulfill(
+		payload: &[u8],
+	) -> sp_runtime::DispatchResultWithInfo<frame_support::weights::PostDispatchInfo> {
+        // handle payload (e.i. Call a contract)
+	}
+}
+
+impl pallet_acurast_xcm_receiver::Config for Runtime {
+	type Event = Event;
+	type Payload = sp_runtime::bounded::bounded_vec::BoundedVec<u8, ConstU32<128>>;
+	type OnFulfillment = OnAcurastFulfillment;
+	type Barrier = ParachainBarrier;
+}
+
+// Add pallet to the runtime
+construct_runtime!(
+	pub enum Runtime where
+		Block = Block,
+		NodeBlock = opaque::Block,
+		UncheckedExtrinsic = UncheckedExtrinsic,
+	{
+		// All your other pallets
+        ...
+		AcurastReceiver: pallet_acurast_xcm_receiver::{Pallet, Storage, Call, Event<T>};
+	}
+);
+```

pallets/acurast-xcm-receiver/src/benchmarking.rs

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+//! Benchmarking setup for pallet-template
+
+// use super::*;
+
+// #[allow(unused)]
+// use frame_benchmarking::{benchmarks, whitelisted_caller};
+// use frame_system::RawOrigin;
+
+// benchmarks! {
+// 	// TODO: add benchmarks
+// 	impl_benchmark_test_suite!(crate::Pallet, crate::mock::new_test_ext(), crate::mock::Test);
+// }

pallets/acurast-xcm-receiver/src/lib.rs

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+#![cfg_attr(not(feature = "std"), no_std)]
+
+pub use pallet::*;
+
+pub mod traits;
+
+#[cfg(test)]
+mod mock;
+
+#[cfg(test)]
+mod tests;
+
+#[cfg(feature = "runtime-benchmarks")]
+mod benchmarking;
+
+#[frame_support::pallet]
+pub mod pallet {
+    use crate::traits::*;
+    use frame_support::pallet_prelude::*;
+    use frame_system::pallet_prelude::OriginFor;
+    use sp_std::prelude::*;
+
+    /// Configure the pallet by specifying the parameters and types on which it depends.
+    #[pallet::config]
+    pub trait Config: frame_system::Config {
+        /// Because this pallet emits events, it depends on the runtime's definition of an event.
+        type Event: From<Event<Self>> + IsType<<Self as frame_system::Config>::Event>;
+        /// The fulfillment payload.
+        type Payload: Parameter + Member + Clone + Into<Vec<u8>>;
+        /// Generic parameters
+        type Parameters: Parameter + Member + Clone + Into<Vec<u8>>;
+        /// Handler to notify the runtime when a new fulfillment is received.
+        type OnFulfillment: OnFulfillment<Self>;
+        /// Handle origin validation
+        type Barrier: ParachainBarrier<Self>;
+    }
+
+    #[pallet::pallet]
+    #[pallet::generate_store(pub(super) trait Store)]
+    pub struct Pallet<T>(_);
+
+    /// TODO: We may want to add a storage for job identifiers, allowing acurast parachain to send
+    /// the (job identifer + payload). The requester address would be indexed by job identifier.
+
+    // Pallets use events to inform users when important changes are made.
+    // https://docs.substrate.io/v3/runtime/events-and-errors
+    #[pallet::event]
+    #[pallet::generate_deposit(pub(super) fn deposit_event)]
+    pub enum Event<T: Config> {
+        FulfillReceived(T::Payload, Option<T::Parameters>),
+    }
+
+    // Errors inform users that something went wrong.
+    #[pallet::error]
+    pub enum Error<T> {}
+
+    #[pallet::call]
+    impl<T: Config> Pallet<T> {
+        /// Dispatchable function that notifies the runtime about a fulfilment coming from acurast parachain.
+        #[pallet::weight(Weight::from_ref_time(10_000).saturating_add(T::DbWeight::get().writes(1)))]
+        pub fn fulfill(
+            origin: OriginFor<T>,
+            payload: T::Payload,
+            parameters: Option<T::Parameters>,
+        ) -> DispatchResult {
+            // Check that the extrinsic comes from a trusted xcm channel.
+            T::Barrier::ensure_xcm_origin(origin)?;
+
+            // Notify the runtime about the fulfillment.
+            match T::OnFulfillment::fulfill(
+                payload.clone().into(),
+                parameters.clone().map(|parameters| parameters.into()),
+            ) {
+                Err(err) => Err(err.error),
+                Ok(_) => {
+                    // Emit events
+                    Self::deposit_event(Event::FulfillReceived(payload, parameters));
+
+                    Ok(())
+                }
+            }
+        }
+    }
+}

pallets/acurast-xcm-receiver/src/mock.rs

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+use crate as pallet_acurast_xcm_receiver;
+use frame_support::{
+    traits::{ConstU16, ConstU64, Everything, Nothing},
+    weights::{Pays, PostDispatchInfo},
+};
+use frame_system as system;
+use sp_core::H256;
+use sp_runtime::{
+    testing::Header,
+    traits::{BlakeTwo256, IdentityLookup},
+};
+use sp_std::prelude::*;
+use xcm::v2::Junction::Parachain;
+
+type UncheckedExtrinsic = frame_system::mocking::MockUncheckedExtrinsic<Test>;
+type Block = frame_system::mocking::MockBlock<Test>;
+
+// Configure a mock runtime to test the pallet.
+frame_support::construct_runtime!(
+    pub enum Test where
+        Block = Block,
+        NodeBlock = Block,
+        UncheckedExtrinsic = UncheckedExtrinsic,
+    {
+        System: frame_system::{Pallet, Call, Config, Storage, Event<T>},
+        AcurastReceiver: pallet_acurast_xcm_receiver::{Pallet, Call, Storage, Event<T>},
+        PolkadotXcm: pallet_xcm::{Pallet, Storage, Call, Event<T>, Origin, Config},
+    }
+);
+
+frame_support::parameter_types! {
+    /// The amount of weight an XCM operation takes. This is safe overestimate.
+    pub UnitWeightCost: xcm::v2::Weight = 200_000_000;
+    /// Maximum number of instructions in a single XCM fragment. A sanity check against
+    /// weight caculations getting too crazy.
+    pub MaxInstructions: u32 = 100;
+    // The ancestry, defines the multilocation describing this consensus system
+    pub Ancestry: xcm::v2::MultiLocation = Parachain(2001).into();
+}
+
+impl pallet_xcm::Config for Test {
+    type Event = Event;
+    type SendXcmOrigin = xcm_builder::EnsureXcmOrigin<Origin, ()>;
+    type XcmRouter = ();
+    type ExecuteXcmOrigin = xcm_builder::EnsureXcmOrigin<Origin, ()>;
+    type XcmExecuteFilter = Nothing;
+    type XcmExecutor = ();
+    type XcmTeleportFilter = Nothing;
+    type XcmReserveTransferFilter = Everything;
+    type Weigher = xcm_builder::FixedWeightBounds<UnitWeightCost, Call, MaxInstructions>;
+    type LocationInverter = xcm_builder::LocationInverter<Ancestry>;
+    type Origin = Origin;
+    type Call = Call;
+    const VERSION_DISCOVERY_QUEUE_SIZE: u32 = 100;
+    type AdvertisedXcmVersion = pallet_xcm::CurrentXcmVersion;
+}
+
+impl system::Config for Test {
+    type BaseCallFilter = frame_support::traits::Everything;
+    type BlockWeights = ();
+    type BlockLength = ();
+    type DbWeight = ();
+    type Origin = Origin;
+    type Call = Call;
+    type Index = u64;
+    type BlockNumber = u64;
+    type Hash = H256;
+    type Hashing = BlakeTwo256;
+    type AccountId = u64;
+    type Lookup = IdentityLookup<Self::AccountId>;
+    type Header = Header;
+    type Event = Event;
+    type BlockHashCount = ConstU64<250>;
+    type Version = ();
+    type PalletInfo = PalletInfo;
+    type AccountData = ();
+    type OnNewAccount = ();
+    type OnKilledAccount = ();
+    type SystemWeightInfo = ();
+    type SS58Prefix = ConstU16<42>;
+    type OnSetCode = ();
+    type MaxConsumers = frame_support::traits::ConstU32<16>;
+}
+
+pub struct OnAcurastFulfillment;
+impl crate::traits::OnFulfillment<Test> for OnAcurastFulfillment {
+    fn fulfill(
+        _payload: Vec<u8>,
+        _parameters: Option<Vec<u8>>,
+    ) -> frame_support::sp_runtime::DispatchResultWithInfo<PostDispatchInfo> {
+        Ok(PostDispatchInfo {
+            actual_weight: None,
+            pays_fee: Pays::No,
+        })
+    }
+}
+
+pub struct ParachainBarrier;
+impl crate::traits::ParachainBarrier<Test> for ParachainBarrier {
+    fn ensure_xcm_origin(
+        origin: frame_system::pallet_prelude::OriginFor<Test>,
+    ) -> Result<(), sp_runtime::DispatchError> {
+        // List of allowd parachains
+        let allowed_parachains = [
+            // Acurast
+            xcm::opaque::latest::Junction::Parachain(2001),
+        ];
+
+        // Ensure that the call comes from an xcm message
+        let location = pallet_xcm::ensure_xcm(origin)?;
+
+        let is_valid_origin = location
+            .interior()
+            .iter()
+            .any(|junction| allowed_parachains.contains(junction));
+
+        if !is_valid_origin {
+            return Err(sp_runtime::DispatchError::Other(
+                "MultiLocation not allowed.",
+            ));
+        }
+
+        Ok(())
+    }
+}
+
+impl pallet_acurast_xcm_receiver::Config for Test {
+    type Event = Event;
+    type Payload = Vec<u8>;
+    type Parameters = Vec<u8>;
+    type OnFulfillment = OnAcurastFulfillment;
+    type Barrier = ParachainBarrier;
+}
+
+// Build genesis storage according to the mock runtime.
+pub fn new_test_ext() -> sp_io::TestExternalities {
+    system::GenesisConfig::default()
+        .build_storage::<Test>()
+        .unwrap()
+        .into()
+}