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Introduction

Cross chain swaps in general work the same way as a normal bridge:

  1. Fetch bridge config and additionally also a new config for supported swap tokens.
  2. Generate a special swap quote.
  3. Commit the quote.
  4. Deposit funds into the bridge contract.
  5. Rhino handles the swap and bridge logic under the hood and sends the funds to the recipient on the destination chain.

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Making cross chain swaps

To make cross chain swaps you can use the same bridge or prepareBridge functions. The only difference is that the arguments are slightly different compared to normal bridges:

const bridgeResult = await rhinoSdk.bridge({
  type: 'bridgeSwap',
  amount: '100',
  tokenIn: SupportedTokens.USDT,
  tokenOut: 'agEUR',
  chainIn: SupportedChains.ARBITRUM_ONE,
  chainOut: SupportedChains.BASE,
  depositor: 'DEPOSITOR_ADDRESS',
  recipient: 'RECIPIENT_ADDRESS',
  mode: 'pay',
}, {
  getChainAdapter: chainConfig =>
    getEvmChainAdapterFromPrivateKey(
      'YOUR_PRIVATE_KEY',
      chainConfig,
    ),
})

Instead of the token field, a swap requires tokenIn and tokenOut fields as well as type: 'bridgeSwap' to indicate that a swap should be performed.

When using swaps only the pay mode is available. receive mode is only supported for bridges without swaps.

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Swap quotes

When using the prepareBridge function with swaps or using the checkQuote hook, you will receive a quote object that contains some additional properties compared to the quote for normal bridges. You will need to compare the _tag field against bridgeSwap first to narrow the type down to the swap quote case to get access to those properties:

  • bridgePayAmount: The amount of tokenIn that will be paid
  • bridgePayAmountUsd: The USD value of the pay amout
  • minReceiveAmount: The minimum amount of tokenOut that will be received on the destination chain after considering slippage.
  • minReceiveAmountUsd: The USD value of the minimum receive amount
  • usdPriceTokenIn: The current USD price of tokenIn
  • usdPriceTokenOut: The current USD price of tokenOut

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Failed swaps

Swaps can fail for a number of reasons, most commonly due to market volatility. Rhino will automatically refund failed swaps to the depositor address on the origin chain. The bridge function will in this case return an error with type SwapFailed that contains metadata about the refund (refund chain, token, amount and transaction hash).
Additionally, the onBridgeStatusChange hook will also first report swap-failed and then follow up with failed-swap-refunded once the refund has been processed. The latter update will contain the same metadata about the swap refund as the returned error.