The `SimpleCaller` contract facilitates external calls by decoding input data, approving token allowances, and forwarding calls to specified targets. It handles token transfers by approving tokens to a target, executing the call, and then transferring any remaining input tokens and all output tokens back to the sender. It ensures the call target is not zero and supports both ETH and ERC-20 tokens.

The `ProtocolFee` contract manages protocol fees for a system. It allows the owner to set and update a default protocol fee, which includes a share percentage and a beneficiary address. It also allows setting a signer address for fee-related signatures. The contract includes validation to ensure the fee share is within acceptable limits and that the beneficiary and signer addresses are not zero.

The `UniswapCaller` contract facilitates token swaps using UniswapV2-like pools. It allows users to execute swaps by specifying input/output tokens, pairs, directions, swap type (fixed input or output), and amount. It handles ETH wrapping/unwrapping, calculates required amounts for swaps, and transfers tokens accordingly. The contract ensures proper token handling and slippage checks during the swap process.

The `Router` contract facilitates token swaps with integrated fee handling and security checks. It supports ERC20 tokens and Ether, allowing users to execute swaps via external calls. The contract validates signatures, manages token transfers, calculates fees, and ensures compliance with specified swap parameters. It also supports permit functionality for token allowances and emits events to track swap executions.

The `SignatureVerifier` contract implements EIP-712 for typed structured data hashing and signing. It verifies and hashes various data structures related to token swaps, including account signatures, protocol fee signatures, and swap descriptions. It also tracks used hashes to prevent double-spending. The contract provides functions to hash specific data structures and mark hashes as used.