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Architecture Overview
Overview of the organization of the code of Borrowing Module of the Angle Protocol
The repository for the Borrowing Module of Angle Protocol can be found on Github here, it is the borrow-contracts repo.
Angle Protocol Borrowing Module Architecture
Angle Borrowing Module has not yet been deployed and will soon be open-sourced. It should be live by the end of May 2022.

Main Contracts

The main contracts in Angle Borrowing Module and their purposes are:
This is the main contract of this borrowing module. It is at the level of this contract that users can deposit collateral, take loans against this collateral by borrowing stablecoins, repaying stablecoins. There is one VaultManager contract per collateral type for each stablecoin. The same collateral could also have different associated VaultManager contracts if different parameters are used.
The main interactions agents have with this contract happen with the following methods:
  • createVault(): for a user to create a vault within the contract
  • angle(): for a user to compose actions with the contract. It can be used to create a vault, add collateral to it, borrow stablecoins against it, remove collateral from a vault, repay debt in a vault, approve the contract for a token through the permit interface for tokens that allow it, or even get debt in a vault from another vault
Keepers monitoring the state of the protocol can participate in the liquidations of unhealthy vaults by calling the liquidate() function. They may call the checkLiquidation() before that to simplify and pass the right parameters to the contract.
VaultManager contracts implement the ERC-721 standard and have minting right on their corresponding AgToken.
Beyond the common ERC-721 functions, Angle leaves the implementations to grant or revoke to an address for all your vaults with a simple permit signature.

​Reactor contract​

This is a contract designed to be plugged on top of a VaultManager contract. It allows users to (indirectly) deposit collateral in a VaultManager and borrow stablecoins from it which are then invested in yield strategies. Stablecoins borrowed from deposited collateral are never accessible to users, they just get a portion of the yield made on it.
There are several entry functions for this contract:
  • deposit() and mint: for a user to deposit collateral in the strategy
  • withdraw() and redeem(): for a user to redeem collateral from the strategy
  • claim(): to claim stablecoin rewards accruing from the strategy.
Strategies can vary. There is a BaseReactor implementation that all reactors should implement.

Supporting Contracts

​CoreBorrow​

This is the core contract of the borrowing module. This contract handles the access control across all contracts (it is read by all treasury contracts), and manages the flashLoanModule. It has no minting rights over the stablecoin contracts.

​Treasury​

This contract is responsible for doing the accounting across all the different VaultManager contracts associated to a stablecoin. There is one such Treasury contract per stablecoin on mainnet.
It is at the level of a Treasury contract that profits and losses from VaultManager and FlashLoan contracts are pooled before a portion is distributed (or not) to veANGLE holders.
Each Treasury contract has the ability to grant minting rights on its associated AgToken: it is hence the contract granting permissions to each new VaultManager.

​Oracle​

Oracle contracts in Angle Borrowing module differ from those in the Core Module of the protocol. Each oracle implementation is different within this new module to optimize for gas cost.

​Settlement​

Settlement contracts can be used to settle that is to say to remove a VaultManager from the protocol. Global settlement corresponds to the situation where all VaultManager contracts associated to one stablecoin are settled at the same time.
In the settlement process, collateral from each VaultManager is transferred to the Settlement contract to first allow owners of over-collateralized vault to claim their collateral upon repaying all their debt. Then owners of stablecoins can redeem collateral at oracle value (if there is enough left).

​Swapper​

This side contract facilitates auto-leverage and liquidations. It can be used to swap from one asset to another hence allowing for instance swaps of stablecoin to collateral to enable users to increase their leverage on the collateral they're using to borrow. The contract implemented by the Angle Core Team is built to optimize interactions with Angle Core Module.

Access Control Conventions and Roles

In this module, there is only one place where roles are stored: it is in the CoreBorrow contract which maintains the integrity of the roles at the module-level.
When a governor or guardian function is called on a contract, this reads (directly or indirectly) in the CoreBorrow contract whether the msg.sender has the correct role.
Beyond the two main guardian and governor roles, the CoreBorrow contract also introduces a FLASHLOANER_TREASURY_ROLE given to Treasury contracts associated to stablecoins on which flash loans can be taken.