Swap Encoder

How to implement a SwapEncoder for a Protocol

Overview

The SwapStructEncoder interface is designed to encode the necessary data for a swap, which will be used by the SwapExecutor to interact with a liquidity pool. The encoder is responsible for structuring the swap details, including the input/output tokens, pool addresses, and any additional protocol-specific parameters.

Each protocol must implement its own SwapStructEncoder and ensure that the swap data is correctly encoded for the SwapExecutor.

Dev environment

  • Run aws codeartifact login --tool pip --repository protosim --domain propeller so you can access the propeller packages.

  • Create the dev environment conda env create -f propeller-swap-encoders/environment_dev.yaml

  • Activate it with conda activate propeller-swap-encoders

  • Install dependencies with pip install -r propeller-swap-encoders/requirements.txt

  • Should you get a pyyaml installation error execute the following command: pip install "cython<3.0.0" && pip install --no-build-isolation pyyaml==5.4.1

You can import the abstract class SwapStructEncoder from propeller-solver-core in your python code like:

from core.encoding.interface import SwapStructEncoder

Key Methods

This is the SwapStructEncoder interface can be found here.

  • encode_swap_struct

    • Purpose: To encode the swap details into a bytes object that the SwapExecutor can use to execute the swap.

    • Parameters:

      • swap: A dictionary containing the swap details. These are the fields present in this dict:

        • pool_id: str: The identifier for the liquidity pool where the swap will occur.

        • sell_token: EthereumToken: The token that will be sold in the swap (e.g., DAI).

        • buy_token: EthereumToken: The token that will be bought in the swap (e.g., WETH).

        • split: float: Indicates how the swap should be split between pools (often set to 0).

        • sell_amount: int: The amount of the sell token to be used in the swap.

        • buy_amount: int: The amount of the buy token to be received from the swap.

        • token_approval_needed: bool: A boolean indicating if token approval is needed before the swap.

        • pool_tokens: An optional tuple containing additional token data specific to the pool.

        • pool_type: str: The type of pool where the swap will be executed (e.g., "BalancerStablePoolState").

      • receiver: The address that will receive the output tokens from the swap.

      • encoding_context: Additional context information necessary for encoding (see more here)

      • **kwargs: Any additional protocol-specific parameters that need to be included in the encoding.

    • Returns: A bytes object containing the encoded swap data.

Implementation Steps

  1. Define Protocol-Specific Encoding Logic: Implement the encode_swap_struct function to encode the swap details specific to the protocol. This may include encoding token addresses, pool addresses, and other necessary parameters into a bytes format.

  2. Compatibility with SwapExecutor: Ensure that the encoded data is compatible with the SwapExecutor implementation for the protocol. The SwapExecutor will rely on this data to perform the swap accurately.

  3. Testing: Thoroughly test the encoding process with various swap scenarios to ensure that the encoded data is correct and that the SwapExecutor can process it without errors.

Example Implementation

See the example implementation of a SwapExecutor for Balancer here and test here.

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