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Ethereum: Solidity

Swap/Exchange Protocol Guide

Implementing the Protocol

To integrate an EVM exchange protocol:

Implement the ISwapAdapter.sol interface.
Create a manifest file summarizing the protocol's metadata.

The Manifest File

The manifest file contains author information and additional static details about the protocol and its testing. Here's a list of all valid keys:

yamlCopy# Author information helps us reach out in case of issues
author:
  name: Propellerheads.xyz
  email: alan@propellerheads.xyz

# Protocol Constants
constants:
  # Minimum gas usage for a swap, excluding token transfers
  protocol_gas: 30000
  # Minimum expected capabilities (individual pools may extend these)
  # To learn about Capabilities, see ISwapAdapter.sol)
  capabilities:
    - SellSide
    - BuySide
    - PriceFunction

# Adapter contract (byte)code files
contract: 
  # Contract runtime (deployed) bytecode (required if no source is provided)
  runtime: UniswapV2SwapAdapter.bin
  # Source code (our CI can generate bytecode if you submit this)
  source: UniswapV2SwapAdapter.sol

# Deployment instances for chain-specific bytecode
# Used by the runtime bytecode build script
instances:
  - chain:
      name: mainnet
      id: 1
    # Constructor arguments for building the contract
    arguments:
      - "0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f"

# Automatic test cases (useful if getPoolIds and getTokens aren't implemented)
tests:
  instances:
    - pool_id: "0xB4e16d0168e52d35CaCD2c6185b44281Ec28C9Dc"
      sell_token: "0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2"
      buy_token: "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48"
      block: 17000000
      chain:
        name: mainnet
        id: 1

Key Functions

Price (optional)

Calculates marginal prices for specified amounts.

The marginal price which is distinct from the executed price: swap(amount_in) / amount_in! The marginal price is defined as the price to trade an arbitrarily small (almost zero) amount after the trade of (amount). E.g. the marginal price of a uniswapv2 pool at zero is: price(0) = reserve0/reserve1

function price(
    bytes32 poolId,
    IERC20 sellToken,
    IERC20 buyToken,
    uint256[] memory sellAmounts
) external returns (Fraction[] memory prices);

Return marginal prices in buyToken/sellToken units.
Include all protocol fees (use minimum fee for dynamic fees).
If you don't implement this function, flag it accordingly in capabilities and make it revert using the NotImplemented error.
While optional, we highly recommend implementing this function. If unavailable, we'll numerically estimate the price function from the swap function.

Swap

Simulates token swapping on a given pool.

function swap(
    bytes32 poolId,
    IERC20 sellToken,
    IERC20 buyToken,
    OrderSide side,
    uint256 specifiedAmount
) external returns (Trade memory trade);

Execute the swap and change the VM state accordingly.
Include a gas usage estimate for each amount (use gasleft() function).
Return a Trade struct with a price attribute containing price(specifiedAmount).
If the price function isn't supported, return Fraction(0, 1) for the price (we'll estimate it numerically).

GetLimits

Retrieves token trading limits.

function getLimits(bytes32 poolId, address sellToken, address buyToken)
    external
    returns (uint256[] memory limits);

Return the maximum tradeable amount for each token.
The limit is reached when the change in received amounts is zero or close to zero.
Overestimate the limit if in doubt.
Ensure the swap function doesn't error with LimitExceeded for amounts below the limit.

getCapabilities

Retrieves pool capabilities.

function getCapabilities(bytes32 poolId, IERC20 sellToken, IERC20 buyToken)
    external
    returns (Capability[] memory);

getTokens (optional)

Retrieves tokens for a given pool.

function getTokens(bytes32 poolId)
    external
    returns (IERC20[] memory tokens);

We mainly use this for testing, as it's redundant with the required substreams implementation.

getPoolIds (optional)

Retrieves a range of pool IDs.

function getPoolIds(uint256 offset, uint256 limit)
    external
    returns (bytes32[] memory ids);

We mainly use this for testing. It's okay not to return all available pools here.
This function helps us test against the substreams implementation.
If you implement it, it saves us time writing custom tests.