Splyt Smart Contracts

A decentralized bill splitting protocol. This repository contains the core smart contracts for creating and managing bill splits.

Contracts Overview

1. SplytTreasury

Manages operational ETH funds used for gas sponsorship. Holds ETH that is sent to the Paymaster to sponsor user transactions.

Key Functions:

• receive() - Accept ETH deposits
• fundPaymaster(address _paymaster, uint256 _amount) - Send ETH to paymaster for gas sponsorship (owner/operators only)
• setOperator(address _operator, bool _authorized) - Add/remove authorized operators (owner only)
• withdraw(uint256 _amount) - Withdraw ETH from treasury (owner only)
• setLowBalanceThreshold(uint128 _newThreshold) - Update low balance alert threshold (owner only)
• pause() / unpause() - Emergency pause functionality (owner only)
• getBalance() - Get current ETH balance
• isLowBalance() - Check if balance is below threshold
• isOperator(address _address) - Check if address is authorized operator
• getStats() - Get full treasury statistics

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2. SplytPaymaster

Handles gas fee sponsorship for users via ERC-4337 Account Abstraction. Validates and pays for user operations with daily spending limits.

Key Functions:

• validatePaymasterUserOp(...) - Validates user operation and checks daily limits
• postOp(...) - Handles refunds if actual gas cost is less than estimated
• deposit() - Deposit ETH to EntryPoint for gas payments (owner only)
• withdraw(address payable to, uint256 amount) - Withdraw ETH from EntryPoint (owner only)
• setDailyLimit(uint128 _limit) - Update daily spending limit per user (owner only)
• pause() / unpause() - Pause paymaster operations (owner only)

State Variables:

• dailyLimit - Maximum amount a user can spend per day
• dailyUsed[address] - Daily usage tracking per user
• lastDay[address] - Last day a user made a transaction

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3. SplitFactory

Factory contract that creates and manages individual Split contracts. Tracks all splits and provides query functions.

Key Functions:

• createSplit(string _description, address[] _participants, uint256[] _amounts, uint256 _expiryDays) - Create a new bill split
• setLimits(uint256 _maxParticipants, uint256 _maxAmount) - Update max participants and max split amount (owner only)
• pause() / unpause() - Pause split creation (owner only)
• getUserSplits(address _user) - Get all split IDs a user is involved in
• getCreatedSplits(address _user) - Get all split IDs created by a user
• getSplitAddress(uint256 _splitId) - Get the address of a split contract by ID
• getStats() - Get total splits created and pause status

State Variables:

• maxParticipants - Maximum number of participants per split (default: 20)
• maxSplitAmount - Maximum total amount per split (default: 1,000,000 USDC)
• splitCounter - Total number of splits created

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4. Split

Individual bill split contract deployed by SplitFactory. Manages payments from participants and releases funds to creator when complete.

Key Functions:

• payShare(bytes32 _txHash) - Pay your share of the bill (participants only)
• cancelSplit() - Cancel the split and refund paid participants (creator only)
• settleExpired() - Settle expired splits by sending collected funds to creator
• getParticipants() - Get array of all participants and their payment status
• getSplitStatus() - Get comprehensive split status information

States:

• ACTIVE - Split is active and accepting payments
• COMPLETED - All participants have paid, funds released to creator
• CANCELLED - Split was cancelled by creator
• EXPIRED - Split expired before completion

Key Features:

• Automatic fund release when all participants pay
• Optional expiration timestamp
• Refund mechanism for cancelled splits
• Reentrancy protection
• USDC token support

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Contract Relationships

SplytTreasury → funds → SplytPaymaster → sponsors gas → Users
                                                           ↓
SplitFactory → creates → Split contracts ← users pay USDC

Security Features

• ReentrancyGuard on all contracts
• Pausable functionality for emergency stops
• Access control via Ownable/Ownable2Step
• Input validation and zero-address checks
• SafeERC20 for token transfers