// 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.

//! A module exporting runtime API implementation functions for all runtime APIs using v2
//! primitives.
//!
//! Runtimes implementing the v2 runtime API are recommended to forward directly to these
//! functions.

use crate::{
	configuration, dmp, hrmp, inclusion, initializer, paras, paras_inherent, scheduler,
	session_info, shared,
};
use primitives::v2::{
	AuthorityDiscoveryId, CandidateEvent, CommittedCandidateReceipt, CoreIndex, CoreOccupied,
	CoreState, GroupIndex, GroupRotationInfo, Hash, Id as ParaId, InboundDownwardMessage,
	InboundHrmpMessage, OccupiedCore, OccupiedCoreAssumption, PersistedValidationData,
	PvfCheckStatement, ScheduledCore, ScrapedOnChainVotes, SessionIndex, SessionInfo,
	ValidationCode, ValidationCodeHash, ValidatorId, ValidatorIndex, ValidatorSignature,
};
use sp_runtime::traits::One;
use sp_std::{collections::btree_map::BTreeMap, prelude::*};

/// Implementation for the `validators` function of the runtime API.
pub fn validators<T: initializer::Config>() -> Vec<ValidatorId> {
	<shared::Pallet<T>>::active_validator_keys()
}

/// Implementation for the `validator_groups` function of the runtime API.
pub fn validator_groups<T: initializer::Config>(
) -> (Vec<Vec<ValidatorIndex>>, GroupRotationInfo<T::BlockNumber>) {
	let now = <frame_system::Pallet<T>>::block_number() + One::one();

	let groups = <scheduler::Pallet<T>>::validator_groups();
	let rotation_info = <scheduler::Pallet<T>>::group_rotation_info(now);

	(groups, rotation_info)
}

/// Implementation for the `availability_cores` function of the runtime API.
pub fn availability_cores<T: initializer::Config>() -> Vec<CoreState<T::Hash, T::BlockNumber>> {
	let cores = <scheduler::Pallet<T>>::availability_cores();
	let parachains = <paras::Pallet<T>>::parachains();
	let config = <configuration::Pallet<T>>::config();

	let now = <frame_system::Pallet<T>>::block_number() + One::one();
	<scheduler::Pallet<T>>::clear();
	<scheduler::Pallet<T>>::schedule(Vec::new(), now);

	let rotation_info = <scheduler::Pallet<T>>::group_rotation_info(now);

	let time_out_at = |backed_in_number, availability_period| {
		let time_out_at = backed_in_number + availability_period;

		let current_window = rotation_info.last_rotation_at() + availability_period;
		let next_rotation = rotation_info.next_rotation_at();

		// If we are within `period` blocks of rotation, timeouts are being checked
		// actively. We could even time out this block.
		if time_out_at < current_window {
			time_out_at
		} else if time_out_at <= next_rotation {
			// Otherwise, it will time out at the sooner of the next rotation
			next_rotation
		} else {
			// or the scheduled time-out. This is by definition within `period` blocks
			// of `next_rotation` and is thus a valid timeout block.
			time_out_at
		}
	};

	let group_responsible_for =
		|backed_in_number, core_index| match <scheduler::Pallet<T>>::group_assigned_to_core(
			core_index,
			backed_in_number,
		) {
			Some(g) => g,
			None => {
				log::warn!(
					target: "runtime::polkadot-api::v2",
					"Could not determine the group responsible for core extracted \
					from list of cores for some prior block in same session",
				);

				GroupIndex(0)
			},
		};

	let mut core_states: Vec<_> = cores
		.into_iter()
		.enumerate()
		.map(|(i, core)| match core {
			Some(occupied) => CoreState::Occupied(match occupied {
				CoreOccupied::Parachain => {
					let para_id = parachains[i];
					let pending_availability =
						<inclusion::Pallet<T>>::pending_availability(para_id)
							.expect("Occupied core always has pending availability; qed");

					let backed_in_number = pending_availability.backed_in_number().clone();
					OccupiedCore {
						next_up_on_available: <scheduler::Pallet<T>>::next_up_on_available(
							CoreIndex(i as u32),
						),
						occupied_since: backed_in_number,
						time_out_at: time_out_at(
							backed_in_number,
							config.chain_availability_period,
						),
						next_up_on_time_out: <scheduler::Pallet<T>>::next_up_on_time_out(
							CoreIndex(i as u32),
						),
						availability: pending_availability.availability_votes().clone(),
						group_responsible: group_responsible_for(
							backed_in_number,
							pending_availability.core_occupied(),
						),
						candidate_hash: pending_availability.candidate_hash(),
						candidate_descriptor: pending_availability.candidate_descriptor().clone(),
					}
				},
				CoreOccupied::Parathread(p) => {
					let para_id = p.claim.0;
					let pending_availability =
						<inclusion::Pallet<T>>::pending_availability(para_id)
							.expect("Occupied core always has pending availability; qed");

					let backed_in_number = pending_availability.backed_in_number().clone();
					OccupiedCore {
						next_up_on_available: <scheduler::Pallet<T>>::next_up_on_available(
							CoreIndex(i as u32),
						),
						occupied_since: backed_in_number,
						time_out_at: time_out_at(
							backed_in_number,
							config.thread_availability_period,
						),
						next_up_on_time_out: <scheduler::Pallet<T>>::next_up_on_time_out(
							CoreIndex(i as u32),
						),
						availability: pending_availability.availability_votes().clone(),
						group_responsible: group_responsible_for(
							backed_in_number,
							pending_availability.core_occupied(),
						),
						candidate_hash: pending_availability.candidate_hash(),
						candidate_descriptor: pending_availability.candidate_descriptor().clone(),
					}
				},
			}),
			None => CoreState::Free,
		})
		.collect();

	// This will overwrite only `Free` cores if the scheduler module is working as intended.
	for scheduled in <scheduler::Pallet<T>>::scheduled() {
		core_states[scheduled.core.0 as usize] = CoreState::Scheduled(ScheduledCore {
			para_id: scheduled.para_id,
			collator: scheduled.required_collator().map(|c| c.clone()),
		});
	}

	core_states
}

/// Returns current block number being processed and the corresponding root hash.
fn current_relay_parent<T: frame_system::Config>(
) -> (<T as frame_system::Config>::BlockNumber, <T as frame_system::Config>::Hash) {
	use parity_scale_codec::Decode as _;
	let state_version = <frame_system::Pallet<T>>::runtime_version().state_version();
	let relay_parent_number = <frame_system::Pallet<T>>::block_number();
	let relay_parent_storage_root = T::Hash::decode(&mut &sp_io::storage::root(state_version)[..])
		.expect("storage root must decode to the Hash type; qed");
	(relay_parent_number, relay_parent_storage_root)
}

fn with_assumption<Config, T, F>(
	para_id: ParaId,
	assumption: OccupiedCoreAssumption,
	build: F,
) -> Option<T>
where
	Config: inclusion::Config,
	F: FnOnce() -> Option<T>,
{
	match assumption {
		OccupiedCoreAssumption::Included => {
			<inclusion::Pallet<Config>>::force_enact(para_id);
			build()
		},
		OccupiedCoreAssumption::TimedOut => build(),
		OccupiedCoreAssumption::Free => {
			if <inclusion::Pallet<Config>>::pending_availability(para_id).is_some() {
				None
			} else {
				build()
			}
		},
	}
}

/// Implementation for the `persisted_validation_data` function of the runtime API.
pub fn persisted_validation_data<T: initializer::Config>(
	para_id: ParaId,
	assumption: OccupiedCoreAssumption,
) -> Option<PersistedValidationData<T::Hash, T::BlockNumber>> {
	let (relay_parent_number, relay_parent_storage_root) = current_relay_parent::<T>();
	with_assumption::<T, _, _>(para_id, assumption, || {
		crate::util::make_persisted_validation_data::<T>(
			para_id,
			relay_parent_number,
			relay_parent_storage_root,
		)
	})
}

/// Implementation for the `assumed_validation_data` function of the runtime API.
pub fn assumed_validation_data<T: initializer::Config>(
	para_id: ParaId,
	expected_persisted_validation_data_hash: Hash,
) -> Option<(PersistedValidationData<T::Hash, T::BlockNumber>, ValidationCodeHash)> {
	let (relay_parent_number, relay_parent_storage_root) = current_relay_parent::<T>();
	// This closure obtains the `persisted_validation_data` for the given `para_id` and matches
	// its hash against an expected one.
	let make_validation_data = || {
		crate::util::make_persisted_validation_data::<T>(
			para_id,
			relay_parent_number,
			relay_parent_storage_root,
		)
		.filter(|validation_data| validation_data.hash() == expected_persisted_validation_data_hash)
	};

	let persisted_validation_data = make_validation_data().or_else(|| {
		// Try again with force enacting the core. This check only makes sense if
		// the core is occupied.
		<inclusion::Pallet<T>>::pending_availability(para_id).and_then(|_| {
			<inclusion::Pallet<T>>::force_enact(para_id);
			make_validation_data()
		})
	});
	// If we were successful, also query current validation code hash.
	persisted_validation_data.zip(<paras::Pallet<T>>::current_code_hash(&para_id))
}

/// Implementation for the `check_validation_outputs` function of the runtime API.
pub fn check_validation_outputs<T: initializer::Config>(
	para_id: ParaId,
	outputs: primitives::v2::CandidateCommitments,
) -> bool {
	<inclusion::Pallet<T>>::check_validation_outputs_for_runtime_api(para_id, outputs)
}

/// Implementation for the `session_index_for_child` function of the runtime API.
pub fn session_index_for_child<T: initializer::Config>() -> SessionIndex {
	// Just returns the session index from `inclusion`. Runtime APIs follow
	// initialization so the initializer will have applied any pending session change
	// which is expected at the child of the block whose context the runtime API was invoked
	// in.
	//
	// Incidentally, this is also the rationale for why it is OK to query validators or
	// occupied cores or etc. and expect the correct response "for child".
	<shared::Pallet<T>>::session_index()
}

/// Implementation for the `AuthorityDiscoveryApi::authorities()` function of the runtime API.
/// It is a heavy call, but currently only used for authority discovery, so it is fine.
/// Gets next, current and some historical authority ids using `session_info` module.
pub fn relevant_authority_ids<T: initializer::Config + pallet_authority_discovery::Config>(
) -> Vec<AuthorityDiscoveryId> {
	let current_session_index = session_index_for_child::<T>();
	let earliest_stored_session = <session_info::Pallet<T>>::earliest_stored_session();

	// Due to `max_validators`, the `SessionInfo` stores only the validators who are actively
	// selected to participate in parachain consensus. We'd like all authorities for the current
	// and next sessions to be used in authority-discovery. The two sets likely have large overlap.
	let mut authority_ids = <pallet_authority_discovery::Pallet<T>>::current_authorities().to_vec();
	authority_ids.extend(<pallet_authority_discovery::Pallet<T>>::next_authorities().to_vec());

	// Due to disputes, we'd like to remain connected to authorities of the previous few sessions.
	// For this, we don't need anyone other than the validators actively participating in consensus.
	for session_index in earliest_stored_session..current_session_index {
		let info = <session_info::Pallet<T>>::session_info(session_index);
		if let Some(mut info) = info {
			authority_ids.append(&mut info.discovery_keys);
		}
	}

	authority_ids.sort();
	authority_ids.dedup();

	authority_ids
}

/// Implementation for the `validation_code` function of the runtime API.
pub fn validation_code<T: initializer::Config>(
	para_id: ParaId,
	assumption: OccupiedCoreAssumption,
) -> Option<ValidationCode> {
	with_assumption::<T, _, _>(para_id, assumption, || <paras::Pallet<T>>::current_code(&para_id))
}

/// Implementation for the `candidate_pending_availability` function of the runtime API.
pub fn candidate_pending_availability<T: initializer::Config>(
	para_id: ParaId,
) -> Option<CommittedCandidateReceipt<T::Hash>> {
	<inclusion::Pallet<T>>::candidate_pending_availability(para_id)
}

/// Implementation for the `candidate_events` function of the runtime API.
// NOTE: this runs without block initialization, as it accesses events.
// this means it can run in a different session than other runtime APIs at the same block.
pub fn candidate_events<T, F>(extract_event: F) -> Vec<CandidateEvent<T::Hash>>
where
	T: initializer::Config,
	F: Fn(<T as frame_system::Config>::Event) -> Option<inclusion::Event<T>>,
{
	use inclusion::Event as RawEvent;

	<frame_system::Pallet<T>>::read_events_no_consensus()
		.into_iter()
		.filter_map(|record| extract_event(record.event))
		.map(|event| match event {
			RawEvent::<T>::CandidateBacked(c, h, core, group) =>
				CandidateEvent::CandidateBacked(c, h, core, group),
			RawEvent::<T>::CandidateIncluded(c, h, core, group) =>
				CandidateEvent::CandidateIncluded(c, h, core, group),
			RawEvent::<T>::CandidateTimedOut(c, h, core) =>
				CandidateEvent::CandidateTimedOut(c, h, core),
			RawEvent::<T>::__Ignore(_, _) => unreachable!("__Ignore cannot be used"),
		})
		.collect()
}

/// Get the session info for the given session, if stored.
pub fn session_info<T: session_info::Config>(index: SessionIndex) -> Option<SessionInfo> {
	<session_info::Pallet<T>>::session_info(index)
}

/// Implementation for the `dmq_contents` function of the runtime API.
pub fn dmq_contents<T: dmp::Config>(
	recipient: ParaId,
) -> Vec<InboundDownwardMessage<T::BlockNumber>> {
	<dmp::Pallet<T>>::dmq_contents(recipient)
}

/// Implementation for the `inbound_hrmp_channels_contents` function of the runtime API.
pub fn inbound_hrmp_channels_contents<T: hrmp::Config>(
	recipient: ParaId,
) -> BTreeMap<ParaId, Vec<InboundHrmpMessage<T::BlockNumber>>> {
	<hrmp::Pallet<T>>::inbound_hrmp_channels_contents(recipient)
}

/// Implementation for the `validation_code_by_hash` function of the runtime API.
pub fn validation_code_by_hash<T: paras::Config>(
	hash: ValidationCodeHash,
) -> Option<ValidationCode> {
	<paras::Pallet<T>>::code_by_hash(hash)
}

/// Disputes imported via means of on-chain imports.
pub fn on_chain_votes<T: paras_inherent::Config>() -> Option<ScrapedOnChainVotes<T::Hash>> {
	<paras_inherent::Pallet<T>>::on_chain_votes()
}

/// Submits an PVF pre-checking vote. See [`paras::Pallet::submit_pvf_check_statement`].
pub fn submit_pvf_check_statement<T: paras::Config>(
	stmt: PvfCheckStatement,
	signature: ValidatorSignature,
) {
	<paras::Pallet<T>>::submit_pvf_check_statement(stmt, signature)
}

/// Returns the list of all PVF code hashes that require pre-checking. See
/// [`paras::Pallet::pvfs_require_precheck`].
pub fn pvfs_require_precheck<T: paras::Config>() -> Vec<ValidationCodeHash> {
	<paras::Pallet<T>>::pvfs_require_precheck()
}

/// Returns the validation code hash for the given parachain making the given `OccupiedCoreAssumption`.
pub fn validation_code_hash<T>(
	para_id: ParaId,
	assumption: OccupiedCoreAssumption,
) -> Option<ValidationCodeHash>
where
	T: inclusion::Config,
{
	with_assumption::<T, _, _>(para_id, assumption, || {
		<paras::Pallet<T>>::current_code_hash(&para_id)
	})
}