> For the complete documentation index, see [llms.txt](https://docs.polystream.xyz/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.polystream.xyz/smart-contracts/adapter.md).

# Adapter

### Purpose

* **Uniform Interface:** Adapters implement the `IProtocolAdapter` interface, providing a consistent set of functions regardless of underlying protocol differences.
* **Simplified Interaction:** They allow Polystream to interact seamlessly with multiple DeFi protocols without dealing directly with each protocol's unique implementations.
* **Yield Management:** Adapters handle yield harvesting, compounding, and fee management, simplifying profit calculations and risk management.

#### Key Components and Functionalities

[`IProtocolAdapter.sol`](https://github.com/polystream-core/polystream-contracts/blob/main/src/adapters/interfaces/IProtocolAdapter.sol)

Defines the standardized interface that all adapters must implement, including methods to:

* Supply and withdraw assets.
* Harvest and compound yields.
* Convert platform fees to rewards.
* Retrieve APY, balances, and principal data.

[`AaveAdapter.sol`](https://github.com/polystream-core/polystream-contracts/blob/main/src/adapters/AaveAdapter.sol)

Specific adapter for interacting with the Aave lending protocol:

* Handles supplying and withdrawing of assets to/from Aave pools.
* Harvests yield by withdrawing accrued interest and redepositing it, thereby compounding returns.
* Manages the conversion of fees into yield, tracks principal deposits, and calculates APY from Aave's interest rate models.

[`LayerBankAdapter.sol`](https://github.com/polystream-core/polystream-contracts/blob/main/src/adapters/LayerBankAdapter.sol)

Adapter specifically designed for LayerBank protocol:

* Manages asset deposits, withdrawals, and yield harvesting on LayerBank.
* Implements advanced handling, including error management for different redeem methods.
* Calculates APY based on LayerBank’s rate models, compounding yields by harvesting interest regularly.


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