@eulerxyz/euler-sdk

Euler-sdk

A basic SDK for interacting with Euler smart contracts in browsers and Node.js applications. Currently this is an alpha software, under intensive development.

Installation

npm i @eulerxyz/euler-sdk

Euler class

The Euler class provides methods for interacting with the Euler protocol.

import { Euler } from "@eulerxyz/euler-sdk"

The constructor arguments are all optional:

• signerOrProvider Ethers Signer or Provider instance.
• chainId Currently the SDK contains built in configurations for mainnet (chainId = 1), which is also default, Ropsten (chainId = 3), Görli (chainId = 5), (chainId = 97) Binance Testnet and (chainId = 84531) Base Görli deployments.
• networkConfig Required when chainId is not 1, 3, 5, 97 or 84531. Object containing euler contract addresses, reference asset address and EUL token config.

const provider = new ethers.providers.JsonRpcProvider("<JSON_RPC_URL>")
const signer = new ethers.Wallet("<PRV_KEY>", provider)

const e = new Euler(signer);

Interacting with the smart contracts

Euler contracts

By default, the SDK provides instances of the ethers.Contract of:

• main Euler modules: Euler, Exec, Liquidation, Markets, Swap and SwapHub
• mining contracts EulStakes and EulDistributor
• lens contract EulerGeneralView
• native governance token EUL

Available on e.contracs property.

// activate a new market
await e.contracts.markets.activateMarket(tokenAddress)

// check to see if liquidation would be profitable
const liquidationOpportunity = await e.contracts.liquidation.callStatic.checkLiquidation(
  liquidator,
  violator,
  underlying,
  collateral
)

// get EUL balance
const balance = await e.contracts.eul.balanceOf(myAccount)

eTokens, dTokens, pTokens

Supply and debt tokens (eToken and dTokens) as well as protected collateral tokens (pTokens) can be instantiated and accessed by helper methods eToken(address), dToken(address), pToken(address)

const eUsdcAddress = await e.contracts.markets.underlyingToEToken(USDC_ADDRESS)
await e.eToken(eUsdcAddress).deposit(0, 1M_USDC)

In addition to that there is also erc20(address) for constructing standard ERC20 contract instances

const daiBalance = await e.erc20(DAI_ADDRESS).balanceOf(myAccount)

Additional helper methods eTokenOf(address), dTokenOf(address), pTokenOf(address) take the underlying address and return a promise for the related Euler token instance. The first snippet in this section can be simplified to:

await (await e.eTokenOf(USDC_ADDRESS)).deposit(0, 1M_USDC)

Swap handlers

The SwapHub module delegates the actual swapping execution to external swap handler contracts. The user designates which handler to use by providing its address while calling the swap function of the SwapHub module. There are currently 3 swap handlers available in the Euler contracts repository. Since swap handlers are not meant to be called directly by users, the Euler class only provides their deployed addresses:

e.addresses.swapHandler1Inch          // swaps through 1Inch
e.addresses.swapHandlerUniAutoRouter  // swaps on Uniswap V2 and V3 with payloads generated by Uniswap's smart-order-router
e.addresses.swapHandlerUniswapV3      // swaps directly on Uniswap V3

Adding external contracts

The SDK can attach any external contract with the addContract method. In this case, both abi and the contract address need to be provided.

e.addContract("weth", WETH_ABI, WETH_ADDRESS)

await e.contracts.weth.deposit({ value: ONE_ETH })

Eul token config

The token configuration like decimals, logo, permit data are provided in eulTokenConfig property:

const { logo, extensions: { permit: { domain } } } = e.eulerTokenConfig

Reference asset

In Euler the reference asset, against which all prices are expressed is WETH. referenceAsset property holds the address of WETH for the selected chain.

Batch transactions

Euler platform supports batching user operations into a single gas efficient transaction. SDK provides a helper method buildBatch to make use of this feature. buildBatch creates encoded payload to the Exec contract's batchDispatch. All public functions of Euler modules are available. The function expects an array of operations:

const batchItems = [
  {
    contract: "eToken",
    address: "0x123..",
    method: "deposit",
    args: [0, 1000000]
  },
  {
    contract: "markets",
    method: "enterMarket",
    args: [0, "0xabc.."]
  }
]

Note that for singleton contracts, the address can be omitted. The contract property can also be a contract instance, in which case the address can also be skipped.

[
  {
    contract: e.eToken("0x123.."),
    method: "deposit",
    args: [0, 1000000]
  },
  /* ... */
]

Finally to send a batch transaction:

const tx = await e.contracts.exec.batchDispatch(e.buildBatch(batchItems), [])

Batch simulations

In Euler it is possible to simulate batch calls in a flexible and powerful way. Internally, the Exec contract exposes a function batchDispatchSimulate, which is meant to be static called. It executes all the operations in a batch, but returns the responses before executing liquidity checks on the accounts involved in the tx. In addition it is possible to add a call to an arbitrary address with and arbitrary payload to a batch, as long as the function invoked doesn't change state (it must be a view function).

By combining batch simulation and calls to external contracts, we are able to build powerful UX for the users. For example we can add a call to the lens contract EulerGeneralView to a simulated batch to receive all state changes to the accounts involved, which the execution of the transaction would result in. In fact we can check any state changes to the chain, as long as there is a view function available (wallet balances, dex slippage etc.).

Because the responses from the batch are returned before the liquidity checks are executed (as long as liquidity check deferral is requested), it is also possible to simulate the state of the account the current batch would result in, even when that would mean collateral violation (health score < 1) or borrow isolation violation. Having full information, the user is then able to modify the batch accordingly.

The SDK provides a helper method simulateBatch

e.simulateBatch(deferredLiquidity, simulationItems)

const {
  simulation,
  gas,
  error,
} = await e.simulateBatch(
  deferredLiquidity,
  simulationItem,
  opts,
  callOverrides,
)
// params:
// `deferredLiquidity` - array of accounts to defer liquidity checks for
// `simulationItems` - array of batch items, in the same format as `buildBatch`
// `opts` - options object, currently only supporting `skipEstimateGas` flag. Optional
// `callOverrides` - ethers standard `CallOverrides` object.

// returns:
// `simulation` - decoded responses from functions called in a batch
// `gas` - gas estimations if tx passes liquidity checks
// `error` - if the batch reverts, contains an object:
//   {
//      isLiquidityCheck: true - the error was thrown by liquidity checks vs execution of batch items
//      value: rawError
//   }
}

External static calls in batch simulations

Internally the calls to external view functions are executed by Exec's doStaticCall function, which takes an encoded call data and contract address as arguments. Therefore payload needs to be encoded twice: first as call data for doStaticCall and then as a batch item. The SDK can simplify this process: as long as the contract called is initialized in the SDK (or it is passed in as an instance), it is possible to define the call in a similar way to a regular batch item, setting a staticCall flag to true. The payload will be encoded for doStaticCall accordingly. The responses will also be unwrapped and decoded automatically.

Note that for gas estimation in batch simulation, all items with staticCall flag are removed. Make sure to remove them also when finally submitting the tx to batchDispatch. If for any reason, a view function should be a part of the transaction and needs to be included in gas estimation, the item should be encoded as a call to doStaticCall directly.

const e = new Euler(signer)
e.addContract("EulerGeneralView")

const items = [
  {
    contract: "eToken",
    address: EUSDC_ADDRESS,
    method: "deposit",
    args: [0, 1M_USDC]
  },
  {
    staticCall: true,
    contract: "eulerGeneralView",
    method: "doQuery"
    args: [{
      eulerContract: e.contracts.euler.address,
      account: MY_ACCOUNT
      markets: [USDC_ADDRESS]
    }]
  }
]

const { simulation } = await e.simulateBatch([MY_ACCOUNT], items)
// simulation[1] contains results from the lens call after the deposit is processed

Using batch simulation as a multicall

The simulation by default makes two calls to the chain: staticCall to get the simulation results and estimateGas to get gas costs. If the purpose of the simulation is only to fetch some onchain data, the gas estimation is not necessary. A flag in options object skipEstimateGas can be used to disable it. It will also be disabled when all the batch items have staticCall flag set (calling external view functions).

In summary, the batch simulation can be made to effectively behave as a multicall for arbitrary view functions.

Signing and using permits

To use EIP2612 permits on Euler, SDK provides signPermit and signPermitBatchItem functions. They both expect a token object with permit extension in euler-tokenlist format. signPermit is a low level function, while signPermitBatchItem should be used when creating calls to batchDispatch.

const batch = [
  await e.signPermitBatchItem(token),
  {
    contract: await e.eTokenOf(token.address),
    method: "deposit",
    args: [0, 10000000]
  }
]

Signers and providers

To switch a signer or provider, call the connect(signerOrProvider) method. All contract instances will automatically switch to the new value. To access currently connected signer or provider, use getSigner() and getProvider() methods.

e.connect(newSigner)

/* ... */

const currentSigner = e.getSigner()

Utilities

Some useful utilities are provided in the utils export of the package. The list will be extended in the future.

import { utils } from "@eulerxyz/euler-sdk" 

Accounts

utils.getSubAccountId(primaryAddress: string, subAccountAddress: string)
Returns an ID of the sub-account given two addresses.

utils.isRealSubAccount(primaryAddress: string, subAccountAddress: string)
Returns true if the second address provided is a sub-account of the first.

utils.getSubAccount(primary: string, subAccountId: number | string)
Returns the sub-account address given primary address and a sub-account ID.