Type: Keeper

The Keeper type implements the ICS4Wrapper interface but passes arguments for the corresponding methods to the underlying ics4Wrapper provided during construction. The Keeper stores a reference to a TransferKeeper, which allows submitting ICS-20 transfer messages; a ChannelKeeper for communicating over channels; and a BankKeeper to handle manual balance updates.

Function: ForwardTransferPacket

The ForwardTransferPacket function does the following:

• It calls TransferKeeper.Transfer to transfer the funds (either to the receiver if there is no next hop, or to the next hop, with the remaining forwarding metadata).

• It decrements the InFlightPacket's remaining retries, if this is not the first forwarding attempt.

• It stores InFlightPacket data with the number of remaining retries under RefundPacketKey in the Keeper's store.

Function: GetAndClearInFlightPacket

The GetAndClearInFlightPacket function retrieves InFlightPacket data for the specified channel ID, port ID, and sequence number in the store under the RefundPacketKey if present and deletes it, returning nil if the key was absent from the store and panicking if data is present in the store but fails to unmarshal.

Function: WriteAcknowledgementForForwardedPacket

The WriteAcknowledgementForForwardedPacket function does the following:

• It looks up the channel corresponding to the InFlightPacket's (RefundPortId, RefundChannelId) tuple.

• If the acknowledgment from the next hop is successful, it forwards the acknowledgment to the previous hop via the underlying ics4Wrapper.

• If the packet is nonrefundable (which other middleware can mark by setting NonrefundableKey to true in the context), it calls Keeper.moveFundsToUserRecoverableAccount and propagates the success/failure of that in the acknowledgment.

• It does the following if the tokens in the acknowledgment are issued by a previous hop.

  • If the tokens to be refunded are issued by a forward hop, it moves tokens from the forward escrow to the previous escrow.

  • If the tokens to be refunded are not issued by a forward hop, it burns tokens from the forward escrow.

  • It decreases the total escrow balance (via unescrowToken).

• It does the following if the tokens in the acknowledgment are not issued by a previous hop.

  • It mints tokens to the forward escrow.

  • It increases the total escrow balance (inlined, but symmetric logic to unescrowToken).

Function: moveFundsToUserRecoverableAccount

The moveFundsToUserRecoverableAccount function does the following:

• It determines an address on the current chain that the original sender can operate via userRecoverableAccount.

• If the tokens are not issued by a previous hop, it mints them and transfers them to the user's account on the current chain.

• If the tokens are issued by a previous hop, it transfers them from the escrow account associated with the previous hop to the user's account on the current chain and updates the escrow balance via unescrowToken.

Function: TimeoutShouldRetry

The TimeoutShouldRetry function retrieves InFlightPacket data for the specified channel ID, port ID, and sequence number in the store under the RefundPacketKey. It returns nil if the key was absent from the store, panics if the data is present from the store but fails to unmarshal, returns both the InFlightPacket and an error if it has a nonpositive amount of retries remaining, and returns the InFlightPacket with no error otherwise.

Function: RetryTimeout

The RetryTimeout function populates the metadata.Next field from the packet's memo field (returning an error if it did not contain valid JSON), validates that the packet's Amount parses (returning an error if not), and calls Keeper.ForwardTransferPacket to attempt to forward the packet again.