// Copyright 2021 Parity Technologies (UK) Ltd.
// This file is part of Cumulus.

// Cumulus 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.

// Cumulus 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 Cumulus.  If not, see <http://www.gnu.org/licenses/>.

use std::{pin::Pin, sync::Arc, time::Duration};

use async_trait::async_trait;
use cumulus_primitives_core::{
	relay_chain::{
		runtime_api::ParachainHost, Block as PBlock, BlockId, CommittedCandidateReceipt,
		Hash as PHash, Header as PHeader, InboundHrmpMessage, OccupiedCoreAssumption, SessionIndex,
		ValidatorId,
	},
	InboundDownwardMessage, ParaId, PersistedValidationData,
};
use cumulus_relay_chain_interface::{RelayChainError, RelayChainInterface, RelayChainResult};
use futures::{FutureExt, Stream, StreamExt};
use polkadot_client::{ClientHandle, ExecuteWithClient, FullBackend};
use polkadot_service::{
	AuxStore, BabeApi, CollatorPair, Configuration, Handle, NewFull, TaskManager,
};
use sc_cli::SubstrateCli;
use sc_client_api::{
	blockchain::BlockStatus, Backend, BlockchainEvents, HeaderBackend, ImportNotifications,
	StorageProof, UsageProvider,
};
use sc_telemetry::TelemetryWorkerHandle;
use sp_api::ProvideRuntimeApi;
use sp_consensus::SyncOracle;
use sp_core::{sp_std::collections::btree_map::BTreeMap, Pair};
use sp_state_machine::{Backend as StateBackend, StorageValue};

/// The timeout in seconds after that the waiting for a block should be aborted.
const TIMEOUT_IN_SECONDS: u64 = 6;

/// Provides an implementation of the [`RelayChainInterface`] using a local in-process relay chain node.
pub struct RelayChainInProcessInterface<Client> {
	full_client: Arc<Client>,
	backend: Arc<FullBackend>,
	sync_oracle: Arc<dyn SyncOracle + Send + Sync>,
	overseer_handle: Handle,
}

impl<Client> RelayChainInProcessInterface<Client> {
	/// Create a new instance of [`RelayChainInProcessInterface`]
	pub fn new(
		full_client: Arc<Client>,
		backend: Arc<FullBackend>,
		sync_oracle: Arc<dyn SyncOracle + Send + Sync>,
		overseer_handle: Handle,
	) -> Self {
		Self { full_client, backend, sync_oracle, overseer_handle }
	}
}

impl<T> Clone for RelayChainInProcessInterface<T> {
	fn clone(&self) -> Self {
		Self {
			full_client: self.full_client.clone(),
			backend: self.backend.clone(),
			sync_oracle: self.sync_oracle.clone(),
			overseer_handle: self.overseer_handle.clone(),
		}
	}
}

#[async_trait]
impl<Client> RelayChainInterface for RelayChainInProcessInterface<Client>
where
	Client: ProvideRuntimeApi<PBlock>
		+ HeaderBackend<PBlock>
		+ BlockchainEvents<PBlock>
		+ AuxStore
		+ UsageProvider<PBlock>
		+ Sync
		+ Send,
	Client::Api: ParachainHost<PBlock> + BabeApi<PBlock>,
{
	async fn retrieve_dmq_contents(
		&self,
		para_id: ParaId,
		relay_parent: PHash,
	) -> RelayChainResult<Vec<InboundDownwardMessage>> {
		Ok(self.full_client.runtime_api().dmq_contents_with_context(
			relay_parent,
			sp_core::ExecutionContext::Importing,
			para_id,
		)?)
	}

	async fn retrieve_all_inbound_hrmp_channel_contents(
		&self,
		para_id: ParaId,
		relay_parent: PHash,
	) -> RelayChainResult<BTreeMap<ParaId, Vec<InboundHrmpMessage>>> {
		Ok(self.full_client.runtime_api().inbound_hrmp_channels_contents_with_context(
			relay_parent,
			sp_core::ExecutionContext::Importing,
			para_id,
		)?)
	}

	async fn header(&self, block_id: BlockId) -> RelayChainResult<Option<PHeader>> {
		let hash = match block_id {
			BlockId::Hash(hash) => hash,
			BlockId::Number(num) => self.full_client.hash(num)?.ok_or_else(|| {
				RelayChainError::GenericError(format!("block with number {num} not found"))
			})?,
		};
		let header = self.full_client.header(hash)?;

		Ok(header)
	}

	async fn persisted_validation_data(
		&self,
		hash: PHash,
		para_id: ParaId,
		occupied_core_assumption: OccupiedCoreAssumption,
	) -> RelayChainResult<Option<PersistedValidationData>> {
		Ok(self.full_client.runtime_api().persisted_validation_data(
			hash,
			para_id,
			occupied_core_assumption,
		)?)
	}

	async fn candidate_pending_availability(
		&self,
		hash: PHash,
		para_id: ParaId,
	) -> RelayChainResult<Option<CommittedCandidateReceipt>> {
		Ok(self.full_client.runtime_api().candidate_pending_availability(hash, para_id)?)
	}

	async fn session_index_for_child(&self, hash: PHash) -> RelayChainResult<SessionIndex> {
		Ok(self.full_client.runtime_api().session_index_for_child(hash)?)
	}

	async fn validators(&self, hash: PHash) -> RelayChainResult<Vec<ValidatorId>> {
		Ok(self.full_client.runtime_api().validators(hash)?)
	}

	async fn import_notification_stream(
		&self,
	) -> RelayChainResult<Pin<Box<dyn Stream<Item = PHeader> + Send>>> {
		let notification_stream = self
			.full_client
			.import_notification_stream()
			.map(|notification| notification.header);
		Ok(Box::pin(notification_stream))
	}

	async fn finality_notification_stream(
		&self,
	) -> RelayChainResult<Pin<Box<dyn Stream<Item = PHeader> + Send>>> {
		let notification_stream = self
			.full_client
			.finality_notification_stream()
			.map(|notification| notification.header);
		Ok(Box::pin(notification_stream))
	}

	async fn best_block_hash(&self) -> RelayChainResult<PHash> {
		Ok(self.backend.blockchain().info().best_hash)
	}

	async fn finalized_block_hash(&self) -> RelayChainResult<PHash> {
		Ok(self.backend.blockchain().info().finalized_hash)
	}

	async fn is_major_syncing(&self) -> RelayChainResult<bool> {
		Ok(self.sync_oracle.is_major_syncing())
	}

	fn overseer_handle(&self) -> RelayChainResult<Handle> {
		Ok(self.overseer_handle.clone())
	}

	async fn get_storage_by_key(
		&self,
		relay_parent: PHash,
		key: &[u8],
	) -> RelayChainResult<Option<StorageValue>> {
		let state = self.backend.state_at(relay_parent)?;
		state.storage(key).map_err(RelayChainError::GenericError)
	}

	async fn prove_read(
		&self,
		relay_parent: PHash,
		relevant_keys: &Vec<Vec<u8>>,
	) -> RelayChainResult<StorageProof> {
		let state_backend = self.backend.state_at(relay_parent)?;

		sp_state_machine::prove_read(state_backend, relevant_keys)
			.map_err(RelayChainError::StateMachineError)
	}

	/// Wait for a given relay chain block in an async way.
	///
	/// The caller needs to pass the hash of a block it waits for and the function will return when the
	/// block is available or an error occurred.
	///
	/// The waiting for the block is implemented as follows:
	///
	/// 1. Get a read lock on the import lock from the backend.
	///
	/// 2. Check if the block is already imported. If yes, return from the function.
	///
	/// 3. If the block isn't imported yet, add an import notification listener.
	///
	/// 4. Poll the import notification listener until the block is imported or the timeout is fired.
	///
	/// The timeout is set to 6 seconds. This should be enough time to import the block in the current
	/// round and if not, the new round of the relay chain already started anyway.
	async fn wait_for_block(&self, hash: PHash) -> RelayChainResult<()> {
		let mut listener =
			match check_block_in_chain(self.backend.clone(), self.full_client.clone(), hash)? {
				BlockCheckStatus::InChain => return Ok(()),
				BlockCheckStatus::Unknown(listener) => listener,
			};

		let mut timeout = futures_timer::Delay::new(Duration::from_secs(TIMEOUT_IN_SECONDS)).fuse();

		loop {
			futures::select! {
				_ = timeout => return Err(RelayChainError::WaitTimeout(hash)),
				evt = listener.next() => match evt {
					Some(evt) if evt.hash == hash => return Ok(()),
					// Not the event we waited on.
					Some(_) => continue,
					None => return Err(RelayChainError::ImportListenerClosed(hash)),
				}
			}
		}
	}

	async fn new_best_notification_stream(
		&self,
	) -> RelayChainResult<Pin<Box<dyn Stream<Item = PHeader> + Send>>> {
		let notifications_stream =
			self.full_client
				.import_notification_stream()
				.filter_map(|notification| async move {
					notification.is_new_best.then_some(notification.header)
				});
		Ok(Box::pin(notifications_stream))
	}
}

pub enum BlockCheckStatus {
	/// Block is in chain
	InChain,
	/// Block status is unknown, listener can be used to wait for notification
	Unknown(ImportNotifications<PBlock>),
}

// Helper function to check if a block is in chain.
pub fn check_block_in_chain<Client>(
	backend: Arc<FullBackend>,
	client: Arc<Client>,
	hash: PHash,
) -> RelayChainResult<BlockCheckStatus>
where
	Client: BlockchainEvents<PBlock>,
{
	let _lock = backend.get_import_lock().read();

	if backend.blockchain().status(hash)? == BlockStatus::InChain {
		return Ok(BlockCheckStatus::InChain)
	}

	let listener = client.import_notification_stream();

	Ok(BlockCheckStatus::Unknown(listener))
}

/// Builder for a concrete relay chain interface, created from a full node. Builds
/// a [`RelayChainInProcessInterface`] to access relay chain data necessary for parachain operation.
///
/// The builder takes a [`polkadot_client::Client`]
/// that wraps a concrete instance. By using [`polkadot_client::ExecuteWithClient`]
/// the builder gets access to this concrete instance and instantiates a [`RelayChainInProcessInterface`] with it.
struct RelayChainInProcessInterfaceBuilder {
	polkadot_client: polkadot_client::Client,
	backend: Arc<FullBackend>,
	sync_oracle: Arc<dyn SyncOracle + Send + Sync>,
	overseer_handle: Handle,
}

impl RelayChainInProcessInterfaceBuilder {
	pub fn build(self) -> Arc<dyn RelayChainInterface> {
		self.polkadot_client.clone().execute_with(self)
	}
}

impl ExecuteWithClient for RelayChainInProcessInterfaceBuilder {
	type Output = Arc<dyn RelayChainInterface>;

	fn execute_with_client<Client, Api, Backend>(self, client: Arc<Client>) -> Self::Output
	where
		Client: ProvideRuntimeApi<PBlock>
			+ HeaderBackend<PBlock>
			+ BlockchainEvents<PBlock>
			+ AuxStore
			+ UsageProvider<PBlock>
			+ 'static
			+ Sync
			+ Send,
		Client::Api: ParachainHost<PBlock> + BabeApi<PBlock>,
	{
		Arc::new(RelayChainInProcessInterface::new(
			client,
			self.backend,
			self.sync_oracle,
			self.overseer_handle,
		))
	}
}

/// Build the Polkadot full node using the given `config`.
#[sc_tracing::logging::prefix_logs_with("Relaychain")]
fn build_polkadot_full_node(
	config: Configuration,
	parachain_config: &Configuration,
	telemetry_worker_handle: Option<TelemetryWorkerHandle>,
	hwbench: Option<sc_sysinfo::HwBench>,
) -> Result<(NewFull<polkadot_client::Client>, Option<CollatorPair>), polkadot_service::Error> {
	let (is_collator, maybe_collator_key) = if parachain_config.role.is_authority() {
		let collator_key = CollatorPair::generate().0;
		(polkadot_service::IsCollator::Yes(collator_key.clone()), Some(collator_key))
	} else {
		(polkadot_service::IsCollator::No, None)
	};

	let relay_chain_full_node = polkadot_service::build_full(
		config,
		is_collator,
		None,
		// Disable BEEFY. It should not be required by the internal relay chain node.
		false,
		None,
		telemetry_worker_handle,
		true,
		polkadot_service::RealOverseerGen,
		None,
		None,
		hwbench,
	)?;

	Ok((relay_chain_full_node, maybe_collator_key))
}

/// Builds a relay chain interface by constructing a full relay chain node
pub fn build_inprocess_relay_chain(
	mut polkadot_config: Configuration,
	parachain_config: &Configuration,
	telemetry_worker_handle: Option<TelemetryWorkerHandle>,
	task_manager: &mut TaskManager,
	hwbench: Option<sc_sysinfo::HwBench>,
) -> RelayChainResult<(Arc<(dyn RelayChainInterface + 'static)>, Option<CollatorPair>)> {
	// This is essentially a hack, but we want to ensure that we send the correct node version
	// to the telemetry.
	polkadot_config.impl_version = polkadot_cli::Cli::impl_version();
	polkadot_config.impl_name = polkadot_cli::Cli::impl_name();

	let (full_node, collator_key) = build_polkadot_full_node(
		polkadot_config,
		parachain_config,
		telemetry_worker_handle,
		hwbench,
	)
	.map_err(|e| RelayChainError::Application(Box::new(e) as Box<_>))?;

	let relay_chain_interface_builder = RelayChainInProcessInterfaceBuilder {
		polkadot_client: full_node.client.clone(),
		backend: full_node.backend.clone(),
		sync_oracle: full_node.sync_service.clone(),
		overseer_handle: full_node.overseer_handle.clone().ok_or(RelayChainError::GenericError(
			"Overseer not running in full node.".to_string(),
		))?,
	};

	task_manager.add_child(full_node.task_manager);

	Ok((relay_chain_interface_builder.build(), collator_key))
}

#[cfg(test)]
mod tests {
	use super::*;

	use polkadot_primitives::Block as PBlock;
	use polkadot_test_client::{
		construct_transfer_extrinsic, BlockBuilderExt, Client, ClientBlockImportExt,
		DefaultTestClientBuilderExt, ExecutionStrategy, InitPolkadotBlockBuilder,
		TestClientBuilder, TestClientBuilderExt,
	};
	use sp_consensus::{BlockOrigin, SyncOracle};
	use sp_runtime::traits::Block as BlockT;
	use std::sync::Arc;

	use futures::{executor::block_on, poll, task::Poll};

	struct DummyNetwork {}

	impl SyncOracle for DummyNetwork {
		fn is_major_syncing(&self) -> bool {
			unimplemented!("Not needed for test")
		}

		fn is_offline(&self) -> bool {
			unimplemented!("Not needed for test")
		}
	}

	fn build_client_backend_and_block(
	) -> (Arc<Client>, PBlock, RelayChainInProcessInterface<Client>) {
		let builder =
			TestClientBuilder::new().set_execution_strategy(ExecutionStrategy::NativeWhenPossible);
		let backend = builder.backend();
		let client = Arc::new(builder.build());

		let block_builder = client.init_polkadot_block_builder();
		let block = block_builder.build().expect("Finalizes the block").block;
		let dummy_network: Arc<dyn SyncOracle + Sync + Send> = Arc::new(DummyNetwork {});

		let (tx, _rx) = metered::channel(30);
		let mock_handle = Handle::new(tx);
		(
			client.clone(),
			block,
			RelayChainInProcessInterface::new(client, backend, dummy_network, mock_handle),
		)
	}

	#[test]
	fn returns_directly_for_available_block() {
		let (mut client, block, relay_chain_interface) = build_client_backend_and_block();
		let hash = block.hash();

		block_on(client.import(BlockOrigin::Own, block)).expect("Imports the block");

		block_on(async move {
			// Should be ready on the first poll
			assert!(matches!(
				poll!(relay_chain_interface.wait_for_block(hash)),
				Poll::Ready(Ok(()))
			));
		});
	}

	#[test]
	fn resolve_after_block_import_notification_was_received() {
		let (mut client, block, relay_chain_interface) = build_client_backend_and_block();
		let hash = block.hash();

		block_on(async move {
			let mut future = relay_chain_interface.wait_for_block(hash);
			// As the block is not yet imported, the first poll should return `Pending`
			assert!(poll!(&mut future).is_pending());

			// Import the block that should fire the notification
			client.import(BlockOrigin::Own, block).await.expect("Imports the block");

			// Now it should have received the notification and report that the block was imported
			assert!(matches!(poll!(future), Poll::Ready(Ok(()))));
		});
	}

	#[test]
	fn wait_for_block_time_out_when_block_is_not_imported() {
		let (_, block, relay_chain_interface) = build_client_backend_and_block();
		let hash = block.hash();

		assert!(matches!(
			block_on(relay_chain_interface.wait_for_block(hash)),
			Err(RelayChainError::WaitTimeout(_))
		));
	}

	#[test]
	fn do_not_resolve_after_different_block_import_notification_was_received() {
		let (mut client, block, relay_chain_interface) = build_client_backend_and_block();
		let hash = block.hash();

		let ext = construct_transfer_extrinsic(
			&client,
			sp_keyring::Sr25519Keyring::Alice,
			sp_keyring::Sr25519Keyring::Bob,
			1000,
		);
		let mut block_builder = client.init_polkadot_block_builder();
		// Push an extrinsic to get a different block hash.
		block_builder.push_polkadot_extrinsic(ext).expect("Push extrinsic");
		let block2 = block_builder.build().expect("Build second block").block;
		let hash2 = block2.hash();

		block_on(async move {
			let mut future = relay_chain_interface.wait_for_block(hash);
			let mut future2 = relay_chain_interface.wait_for_block(hash2);
			// As the block is not yet imported, the first poll should return `Pending`
			assert!(poll!(&mut future).is_pending());
			assert!(poll!(&mut future2).is_pending());

			// Import the block that should fire the notification
			client.import(BlockOrigin::Own, block2).await.expect("Imports the second block");

			// The import notification of the second block should not make this one finish
			assert!(poll!(&mut future).is_pending());
			// Now it should have received the notification and report that the block was imported
			assert!(matches!(poll!(future2), Poll::Ready(Ok(()))));

			client.import(BlockOrigin::Own, block).await.expect("Imports the first block");

			// Now it should be ready
			assert!(matches!(poll!(future), Poll::Ready(Ok(()))));
		});
	}
}