Add Parachain Onboarding to Rococo (#2660)

* Add Parachain Onboarding Pallets to Rococo

* remove propose_parachain

* add back para sudo wrapper

* Revert "remove propose_parachain"

This reverts commit 38b7c33c817964c9f8ad48531a72aede83670291.

* turn propose_parachains into validator_manager

* Update runtime/rococo/src/lib.rs

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* update origin

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

polkadot/runtime/rococo/src/validator_manager.rs

@@ -0,0 +1,142 @@
+// Copyright 2020 Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Polkadot is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+//! A pallet for managing validators on Rococo.
+
+use frame_support::{
+	decl_event, decl_error, decl_module, decl_storage,
+	traits::EnsureOrigin,
+};
+use sp_staking::SessionIndex;
+use sp_std::vec::Vec;
+
+type Session<T> = pallet_session::Module<T>;
+
+/// Configuration for the parachain proposer.
+pub trait Config: pallet_session::Config {
+	/// The overreaching event type.
+	type Event: From<Event<Self>> + Into<<Self as frame_system::Config>::Event>;
+
+	/// Privileged origin that can add or remove validators.
+	type PrivilegedOrigin: EnsureOrigin<<Self as frame_system::Config>::Origin>;
+}
+
+decl_event! {
+	pub enum Event<T> where ValidatorId = <T as pallet_session::Config>::ValidatorId {
+		/// New validators were added to the set.
+		ValidatorsRegistered(Vec<ValidatorId>),
+		/// Validators were removed from the set.
+		ValidatorsDeregistered(Vec<ValidatorId>),
+	}
+}
+
+decl_error! {
+	pub enum Error for Module<T: Config> {}
+}
+
+decl_storage! {
+	trait Store for Module<T: Config> as ParachainProposer {
+		/// Validators that should be retired, because their Parachain was deregistered.
+		ValidatorsToRetire: Vec<T::ValidatorId>;
+		/// Validators that should be added.
+		ValidatorsToAdd: Vec<T::ValidatorId>;
+	}
+}
+
+decl_module! {
+	pub struct Module<T: Config> for enum Call where origin: <T as frame_system::Config>::Origin {
+		type Error = Error<T>;
+
+		fn deposit_event() = default;
+
+		/// Add new validators to the set.
+		///
+		/// The new validators will be active from current session + 2.
+		#[weight = 100_000]
+		fn register_validators(
+			origin,
+			validators: Vec<T::ValidatorId>,
+		) {
+			T::PrivilegedOrigin::ensure_origin(origin)?;
+
+			validators.clone().into_iter().for_each(|v| ValidatorsToAdd::<T>::append(v));
+
+			Self::deposit_event(RawEvent::ValidatorsRegistered(validators));
+		}
+
+		/// Remove validators from the set.
+		///
+		/// The removed validators will be deactivated from current session + 2.
+		#[weight = 100_000]
+		fn deregister_validators(
+			origin,
+			validators: Vec<T::ValidatorId>,
+		) {
+			T::PrivilegedOrigin::ensure_origin(origin)?;
+
+			validators.clone().into_iter().for_each(|v| ValidatorsToRetire::<T>::append(v));
+
+			Self::deposit_event(RawEvent::ValidatorsDeregistered(validators));
+		}
+	}
+}
+
+impl<T: Config> Module<T> {}
+
+impl<T: Config> pallet_session::SessionManager<T::ValidatorId> for Module<T> {
+	fn new_session(new_index: SessionIndex) -> Option<Vec<T::ValidatorId>> {
+		if new_index <= 1 {
+			return None;
+		}
+
+		let mut validators = Session::<T>::validators();
+
+		ValidatorsToRetire::<T>::take().iter().for_each(|v| {
+			if let Some(pos) = validators.iter().position(|r| r == v) {
+				validators.swap_remove(pos);
+			}
+		});
+
+		ValidatorsToAdd::<T>::take().into_iter().for_each(|v| {
+			if !validators.contains(&v) {
+				validators.push(v);
+			}
+		});
+
+		Some(validators)
+	}
+
+	fn end_session(_: SessionIndex) {}
+
+	fn start_session(_start_index: SessionIndex) {}
+}
+
+impl<T: Config> pallet_session::historical::SessionManager<T::ValidatorId, ()> for Module<T> {
+	fn new_session(
+		new_index: SessionIndex,
+	) -> Option<Vec<(T::ValidatorId, ())>> {
+		<Self as pallet_session::SessionManager<_>>::new_session(new_index)
+			.map(|r| r.into_iter().map(|v| (v, Default::default())).collect())
+	}
+
+	fn start_session(start_index: SessionIndex) {
+		<Self as pallet_session::SessionManager<_>>::start_session(start_index)
+	}
+
+	fn end_session(end_index: SessionIndex) {
+		<Self as pallet_session::SessionManager<_>>::end_session(end_index)
+	}
+}