The Ethereum Vault Connector (EVC) is a foundational layer designed to facilitate the core functionality required for a lending market. It serves as a base building block for various protocols, providing a robust and flexible framework for developers to build upon. The EVC primarily mediates between vaults, contracts that implement the ERC-4626 interface and contain additional logic for interfacing with other vaults. The EVC not only provides a common base ecosystem but also reduces complexity in the core lending/borrowing contracts, allowing them to focus on their differentiating factors.

For more information about the EVC refer to the EVC WHITEPAPER and the EVC SPECS.

This repository serves as a sandbox for exploring the EVC. It includes various example vaults, operators, and patterns that can be utilized as a foundation for creating your own smart contracts that interact with the EVC. Given the complexity of the EVC, the EVC Playground repository was established to illustrate basic concepts related to the EVC, to foster the development of standard patterns and best practices for building products on top of the EVC. Please note that none of the contracts in this repository have been audited and are intended solely for testing and experimentation. They should not be used in production under any circumstances.

.
├── interfaces
│   ├── IIRM.sol
│   └── IPriceOracle.sol
└── operators
|   ├── LightweightOrderOperator.sol
│   └── SimpleWithdrawOperator.sol
├── utils
|   ├── EVCClient.sol
|   ├── SimpleConditionsEnforcer.sol
│   └── TipsPiggyBank.sol
└── vaults
    ├── VaultBase.sol
    ├── VaultBorrowableWETH.sol
    ├── VaultRegularBorrowable.sol
    ├── VaultSimple.sol
    └── VaultSimpleBorrowable.sol

If you're interested in building a vault that is interoperable with the EVC, you should start by looking at the EVCClient contract and the contracts in the vaults directory.

The EVCClient contract is an abstract base contract for interacting with the EVC. It provides utility functions for authenticating callers in the context of the EVC, scheduling and forgiving status checks, and liquidating collateral shares.

The VaultBase is an abstract base contract that all EVC-interoperable vaults inherit from. It provides standard modifiers for reentrancy protection and account/vault status checks scheduling. It declares functions that must be defined in the child contract in order to correctly implement controller release, vault snapshotting and account/vaults status checks.

The VaultSimple contract is a simple vault that implements the ERC-4626 interface. It provides basic functionality for a vault. The contract showcases a pattern that should be followed in order to properly use EVC's authentication features for non-borrowing operations (when it doesn't matter whether the user has enabled a controller). It implements a simple vault status check based on a pre- and post-operation snapshots. Due to non-borrowing nature of the vault, the account status check is implemented as always valid.

The VaultSimpleBorrowable contract is a simple vault that extents the VaultSimple functionality by adding a borrowing functionality (but no interest accrual). The contract showcases a pattern that should be followed in order to properly use EVC's authentication features for borrowing operations (when it matters whether the user has enabled a controller). It implements a simple vault status check based on a pre- and post-operation snapshots and a simple account status check.

The VaultRegularBorrowable contract is a vault that extends the VaultSimpleBorrowable functionality by adding recognized collaterals, price oracle integration and interest accrual. It implements a simple liquidation pattern that showcases the EVC's impersonate functionality that is used in order to seize violator's collateral shares.

The VaultBorrowableWETH contract is a vault that extends the VaultRegularBorrowable functionality by adding a special function for handling ETH deposits into a WETH vault. It showcases EVC callback functionality for a payable function.

Areas of experimentation for vaults:

1. Real World Assets (RWA) lending
2. NFT lending
3. uncollateralized lending
4. P2P lending
5. deposit-only vaults that can be used a collaterals for other vaults
6. risk management
7. collateral types
8. oracles
9. interest rate models

If you'd like to learn how EVC can be used to enable gasless transactions, you should look at the GaslessTx and ConditionalGaslessTx tests.

The GaslessTx shows how one can use EVC's permit functionality in order to sign a permit message that contains calldata that can be executed by anyone on behalf of the signer. It also shows how a relayer of such a transaction can be incentivized by the signer.

The ConditionalGaslessTx shows how one can use EVC's permit functionality in order to sign a permit message that contains conditional calldata that can be executed by anyone on behalf of the signer, but only when encoded conditions are met. This concept can be used for implementing conditional orders (e.g. stop-loss, take-profit etc.).

If you're interested in learning how to use EVC operators, you should look at the contracts in the operators directory.

SimpleWithdrawOperator shows how to write a contract that allows anyone, in exchange for a tip, to pull liquidity out of a heavily utilised vault on behalf of someone else. Thanks to this operator, a user can delegate the monitoring of their vault to someone else and go on with their life.

LigthweightOrderOperator shows how to write a stateful operator for orders management. It allows for submitting orders that can execute any arbitrary calldata that does not require authentication (i.e. enforcing order conditions) as well as the calldata that requires EVC authentication (i.e. vaults interactions). Submitted orders are publicly visible and therefore executable by anyone in exchange for a tip. The owner of the order can cancel it at any time. In order to understand how the operator works, it's best to look at the relevant test.

Areas of experimentation for permits and operators:

1. gasless transactions, ability to pay for gas in any ERC20 token
2. intents support
3. conditional orders (e.g. stop-loss, take-profit, trailing-stop etc.)
4. position managers (e.g. rebalancing)
5. opt-in liquidation flows
6. lending pool optimizers

To install EVC Playground in a Foundry project:

forge install euler-xyz/evc-playground

EVC Playground includes a suite of tests written in Solidity with Foundry.

Note: The tests are not complete and are only meant to be used as a starting point for building your own test suite.

To install Foundry:

curl -L https://foundry.paradigm.xyz | bash

This will download foundryup. To start Foundry, run:

foundryup

To clone the repo:

git clone https://github.com/euler-xyz/evc-playground.git && cd evc-playground

To run the tests:

forge test

This software is experimental and is provided "as is" and "as available". No warranties are provided, and no liability will be assumed for any loss incurred through the use of this codebase.

Always include thorough tests when using code snippets from this repository to ensure compatibility with your code.

The smart contracts in this repository have not been audited and should not be used in production.

This software is designed to develop standard patterns and best practices for building products on top of EVC. We welcome feedback, new ideas, and contributions. If you're interested in conducting security research, writing more tests (including formal verification), improving readability and documentation, optimizing, simplifying, or developing new integrations, please feel free to contribute.

Licensed under the GPL-2.0-or-later license.