raiden-state-machine 0.1.0

#![warn(clippy::missing_docs_in_private_items)]

use raiden_primitives::{
	constants::CANONICAL_IDENTIFIER_UNORDERED_QUEUE,
	types::{
		BlockHash,
		BlockNumber,
	},
};

use super::{
	channel,
	mediator,
	secret_registry,
	utils::{
		self,
		update_channel,
	},
};
use crate::{
	errors::StateTransitionError,
	types::{
		ActionInitTarget,
		Block,
		ChainState,
		ChannelState,
		ContractReceiveSecretReveal,
		ErrorUnlockClaimFailed,
		Event,
		PaymentReceivedSuccess,
		ReceiveLockExpired,
		ReceiveSecretReveal,
		ReceiveUnlock,
		SendMessageEventInner,
		SendSecretRequest,
		SendSecretReveal,
		StateChange,
		TargetState,
		TargetTransferState,
	},
	views,
};

/// A transition result for the initiator state.
pub(super) type TransitionResult = std::result::Result<TargetTransition, StateTransitionError>;

/// Target transition content.
#[derive(Debug)]
pub struct TargetTransition {
	pub new_state: Option<TargetTransferState>,
	pub chain_state: ChainState,
	pub events: Vec<Event>,
}

/// Emits the event for revealing the secret on-chain if the transfer
/// can not be settled off-chain.
fn events_for_onchain_secretreveal(
	target_state: &mut TargetTransferState,
	channel_state: &ChannelState,
	block_number: BlockNumber,
	block_hash: BlockHash,
) -> Result<Vec<Event>, String> {
	let transfer = &target_state.transfer;
	let expiration = transfer.lock.expiration;

	let safe_to_wait =
		mediator::is_safe_to_wait(expiration, channel_state.reveal_timeout, block_number).is_ok();
	let secret_known_offchain =
		channel_state.partner_state.is_secret_known_offchain(transfer.lock.secrethash);
	let has_onchain_reveal_started = target_state.state == TargetState::OnchainSecretReveal;

	if !safe_to_wait && secret_known_offchain && !has_onchain_reveal_started {
		target_state.state = TargetState::OnchainSecretReveal;
		let secret = match channel_state.partner_state.get_secret(transfer.lock.secrethash) {
			Some(secret) => secret,
			None => return Err("Secret should be known at this point".to_owned()),
		};

		return Ok(secret_registry::events_for_onchain_secretreveal(
			channel_state,
			secret,
			expiration,
			block_hash,
		))
	}

	Ok(vec![])
}

/// Handles an ActionInitTarget state change.
fn handle_init_target(
	mut chain_state: ChainState,
	target_state: Option<TargetTransferState>,
	state_change: ActionInitTarget,
) -> TransitionResult {
	if target_state.is_some() {
		// Target state should be None
		return Ok(TargetTransition { new_state: target_state, chain_state, events: vec![] })
	}

	let transfer = &state_change.transfer;
	let from_hop = state_change.from_hop;

	let mut channel_state = match views::get_channel_by_canonical_identifier(
		&chain_state,
		transfer.balance_proof.canonical_identifier.clone(),
	) {
		Some(channel_state) => channel_state.clone(),
		None => return Ok(TargetTransition { new_state: None, chain_state, events: vec![] }),
	};

	let sender = match transfer.balance_proof.sender {
		Some(sender) => sender,
		None => return Err("Transfer sender should be set".to_owned().into()),
	};
	let handle_locked_transfer = channel::handle_receive_locked_transfer(
		&mut channel_state,
		transfer.clone(),
		views::get_address_metadata(sender, transfer.route_states.clone()),
	);
	let reveal_timeout = channel_state.reveal_timeout;
	update_channel(&mut chain_state, channel_state).map_err(Into::into)?;

	let mut events = vec![];
	let target_state = match handle_locked_transfer {
		Ok(channel_event) => {
			// A valid balance proof does not mean the payment itself is still valid.
			// e.g. the lock may be near expiration or have expired. This is fine. The
			// message with an unusable lock must be handled to properly synchronize the
			// local view of the partner's channel state, allowing the next balance
			// proofs to be handled. This however, must only be done once, which is
			// enforced by the nonce increasing sequentially, which is verified by
			// the handler handle_receive_lockedtransfer.
			let target_state = TargetTransferState {
				from_hop,
				transfer: transfer.clone(),
				secret: None,
				state: TargetState::SecretRequest,
				initiator_address_metadata: None,
			};
			events.push(channel_event);

			if state_change.received_valid_secret {
				return Ok(TargetTransition { new_state: Some(target_state), chain_state, events })
			}

			let safe_to_wait = mediator::is_safe_to_wait(
				transfer.lock.expiration,
				reveal_timeout,
				chain_state.block_number,
			)
			.is_ok();
			if safe_to_wait {
				let message_identifier = chain_state.pseudo_random_number_generator.next();
				let recipient = transfer.initiator;
				let secret_request = SendSecretRequest {
					inner: SendMessageEventInner {
						recipient,
						recipient_metadata: views::get_address_metadata(
							recipient,
							transfer.route_states.clone(),
						),
						canonical_identifier: CANONICAL_IDENTIFIER_UNORDERED_QUEUE,
						message_identifier,
					},
					payment_identifier: transfer.payment_identifier,
					amount: transfer.lock.amount,
					expiration: transfer.lock.expiration,
					secrethash: transfer.lock.secrethash,
				};
				events.push(secret_request.into());
			}
			Some(target_state)
		},
		Err((e, err_events)) => {
			let unlock_failed = ErrorUnlockClaimFailed {
				identifier: transfer.payment_identifier,
				secrethash: transfer.lock.secrethash,
				reason: e,
			};
			events.push(unlock_failed.into());
			events.extend(err_events);
			None
		},
	};

	Ok(TargetTransition { new_state: target_state, chain_state, events })
}

/// After Raiden learns about a new block this function must be called to
/// handle expiration of the hash time lock.
fn handle_block(
	chain_state: ChainState,
	target_state: Option<TargetTransferState>,
	state_change: Block,
) -> TransitionResult {
	let mut target_state = match target_state {
		Some(target_state) => target_state,
		None => return Err("Block should be accompanied by a valid target state".to_owned().into()),
	};

	let mut events = vec![];

	let transfer = &target_state.transfer;
	let lock = &transfer.lock;

	let channel_state = match views::get_channel_by_canonical_identifier(
		&chain_state,
		transfer.balance_proof.canonical_identifier.clone(),
	) {
		Some(channel_state) => channel_state,
		None =>
			return Ok(TargetTransition {
				new_state: Some(target_state),
				chain_state,
				events: vec![],
			}),
	};

	let secret_known = channel_state.partner_state.is_secret_known(lock.secrethash);
	let lock_has_expired = channel::validators::is_lock_expired(
		&channel_state.our_state,
		lock,
		chain_state.block_number,
		channel::views::get_receiver_expiration_threshold(lock.expiration),
	)
	.is_ok();

	if lock_has_expired && target_state.state != TargetState::Expired {
		target_state.state = TargetState::Expired;
		events.push(
			ErrorUnlockClaimFailed {
				identifier: transfer.payment_identifier,
				secrethash: transfer.lock.secrethash,
				reason: "Lock expired".to_owned(),
			}
			.into(),
		);
	} else if secret_known {
		events.extend(
			events_for_onchain_secretreveal(
				&mut target_state,
				channel_state,
				state_change.block_number,
				state_change.block_hash,
			)
			.map_err(Into::into)?,
		);
	}

	Ok(TargetTransition { new_state: Some(target_state), chain_state, events })
}

/// Validates and handles a ReceiveSecretReveal state change.
fn handle_offchain_secret_reveal(
	mut chain_state: ChainState,
	target_state: Option<TargetTransferState>,
	state_change: ReceiveSecretReveal,
) -> TransitionResult {
	let mut target_state = match target_state {
		Some(target_state) => target_state,
		None => return Err("Block should be accompanied by a valid target state".to_owned().into()),
	};

	let mut events = vec![];

	let transfer = &target_state.transfer;

	let mut channel_state = match views::get_channel_by_canonical_identifier(
		&chain_state,
		transfer.balance_proof.canonical_identifier.clone(),
	) {
		Some(channel_state) => channel_state.clone(),
		None =>
			return Ok(TargetTransition {
				new_state: Some(target_state),
				chain_state,
				events: vec![],
			}),
	};

	let valid_secret = utils::is_valid_secret_reveal(&state_change, transfer.lock.secrethash);
	let has_transfer_expired = channel::validators::is_transfer_expired(
		transfer,
		&channel_state,
		chain_state.block_number,
	);

	if valid_secret && !has_transfer_expired {
		channel::register_offchain_secret(
			&mut channel_state,
			state_change.secret.clone(),
			state_change.secrethash,
		);
		update_channel(&mut chain_state, channel_state).map_err(Into::into)?;

		let from_hop = &target_state.from_hop;
		let message_identifier = chain_state.pseudo_random_number_generator.next();
		target_state.state = TargetState::OffchainSecretReveal;
		target_state.secret = Some(state_change.secret.clone());
		let recipient = from_hop.node_address;

		let reveal = SendSecretReveal {
			inner: SendMessageEventInner {
				recipient,
				recipient_metadata: views::get_address_metadata(
					recipient,
					transfer.route_states.clone(),
				),
				canonical_identifier: CANONICAL_IDENTIFIER_UNORDERED_QUEUE,
				message_identifier,
			},
			secret: state_change.secret,
			secrethash: state_change.secrethash,
		};

		events.push(reveal.into());
	}

	Ok(TargetTransition { new_state: Some(target_state), chain_state, events })
}

/// Validates and handles a `ContractReceiveSecretReveal` state change.
fn handle_onchain_secret_reveal(
	mut chain_state: ChainState,
	target_state: Option<TargetTransferState>,
	state_change: ContractReceiveSecretReveal,
) -> TransitionResult {
	let mut target_state = match target_state {
		Some(target_state) => target_state,
		None => return Err("Block should be accompanied by a valid target state".to_owned().into()),
	};

	let transfer = &target_state.transfer;

	let mut channel_state = match views::get_channel_by_canonical_identifier(
		&chain_state,
		transfer.balance_proof.canonical_identifier.clone(),
	) {
		Some(channel_state) => channel_state.clone(),
		None =>
			return Ok(TargetTransition {
				new_state: Some(target_state),
				chain_state,
				events: vec![],
			}),
	};

	let valid_secret =
		utils::is_valid_onchain_secret_reveal(&state_change, transfer.lock.secrethash);

	if valid_secret {
		channel::register_onchain_secret(
			&mut channel_state,
			state_change.secret.clone(),
			state_change.secrethash,
			state_change.block_number,
			true,
		);
		update_channel(&mut chain_state, channel_state).map_err(Into::into)?;

		target_state.state = TargetState::OffchainSecretReveal;
		target_state.secret = Some(state_change.secret);
	}

	Ok(TargetTransition { new_state: Some(target_state), chain_state, events: vec![] })
}

/// Remove expired locks from channel states.
fn handle_lock_expired(
	mut chain_state: ChainState,
	target_state: Option<TargetTransferState>,
	state_change: ReceiveLockExpired,
) -> TransitionResult {
	let target_state = match target_state {
		Some(target_state) => target_state,
		None => return Err("Block should be accompanied by a valid target state".to_owned().into()),
	};

	let transfer = &target_state.transfer;

	let mut channel_state = match views::get_channel_by_canonical_identifier(
		&chain_state,
		transfer.balance_proof.canonical_identifier.clone(),
	) {
		Some(channel_state) => channel_state.clone(),
		None =>
			return Ok(TargetTransition {
				new_state: Some(target_state),
				chain_state,
				events: vec![],
			}),
	};

	let sender = match transfer.balance_proof.sender {
		Some(sender) => sender,
		None => return Err("Transfer sender should be set".to_owned().into()),
	};
	let recipient_metadata = views::get_address_metadata(sender, transfer.route_states.clone());
	let mut result = channel::handle_receive_lock_expired(
		&mut channel_state,
		state_change,
		chain_state.block_number,
		recipient_metadata,
	)?;
	let channel_state = match result.new_state {
		Some(channel_state) => channel_state,
		None =>
			return Err("handle_receive_lock_expired should not delete channel".to_owned().into()),
	};

	update_channel(&mut chain_state, channel_state.clone()).map_err(Into::into)?;

	if channel::views::get_lock(&channel_state.partner_state, transfer.lock.secrethash).is_none() {
		let unlock_failed = ErrorUnlockClaimFailed {
			identifier: transfer.payment_identifier,
			secrethash: transfer.lock.secrethash,
			reason: "Lock expired".to_owned(),
		};
		result.events.push(unlock_failed.into());
	}

	Ok(TargetTransition { new_state: Some(target_state), chain_state, events: result.events })
}

/// Handles a `ReceiveUnlock` state change.
fn handle_unlock(
	mut chain_state: ChainState,
	target_state: Option<TargetTransferState>,
	state_change: ReceiveUnlock,
) -> TransitionResult {
	let target_state = match target_state {
		Some(target_state) => target_state,
		None => return Err("Block should be accompanied by a valid target state".to_owned().into()),
	};

	let mut events = vec![];
	let transfer = &target_state.transfer;

	let mut channel_state = match views::get_channel_by_canonical_identifier(
		&chain_state,
		transfer.balance_proof.canonical_identifier.clone(),
	) {
		Some(channel_state) => channel_state.clone(),
		None =>
			return Ok(TargetTransition {
				new_state: Some(target_state),
				chain_state,
				events: vec![],
			}),
	};

	let sender = match transfer.balance_proof.sender {
		Some(sender) => sender,
		None => return Err("Transfer sender should be set".to_owned().into()),
	};
	let recipient_metadata = views::get_address_metadata(sender, transfer.route_states.clone());

	let unlock_event =
		match channel::handle_unlock(&mut channel_state, state_change, recipient_metadata) {
			Ok(unlock_event) => unlock_event,
			Err((_, error_event)) =>
				return Ok(TargetTransition {
					new_state: Some(target_state),
					chain_state,
					events: vec![error_event],
				}),
		};

	update_channel(&mut chain_state, channel_state.clone()).map_err(Into::into)?;

	let payment_received_success = PaymentReceivedSuccess {
		token_network_registry_address: channel_state.token_network_registry_address,
		token_network_address: channel_state.canonical_identifier.token_network_address,
		identifier: transfer.payment_identifier,
		amount: transfer.lock.amount,
		initiator: transfer.initiator,
	};
	events.push(unlock_event);
	events.push(payment_received_success.into());

	Ok(TargetTransition { new_state: None, chain_state, events })
}

/// State machine for the target node of a mediated transfer.
pub fn state_transition(
	chain_state: ChainState,
	target_state: Option<TargetTransferState>,
	state_change: StateChange,
) -> TransitionResult {
	match state_change {
		StateChange::ActionInitTarget(inner) =>
			handle_init_target(chain_state, target_state, inner),
		StateChange::Block(inner) => handle_block(chain_state, target_state, inner),
		StateChange::ReceiveSecretReveal(inner) =>
			handle_offchain_secret_reveal(chain_state, target_state, inner),
		StateChange::ContractReceiveSecretReveal(inner) =>
			handle_onchain_secret_reveal(chain_state, target_state, inner),
		StateChange::ReceiveUnlock(inner) => handle_unlock(chain_state, target_state, inner),
		StateChange::ReceiveLockExpired(inner) =>
			handle_lock_expired(chain_state, target_state, inner),
		_ => Ok(TargetTransition { new_state: target_state, chain_state, events: vec![] }),
	}
}