### Smart Contract Events for SnowRail Agent

Source: https://chatgpt.com/share/692a6fad-cf18-8012-b784-5366b9c093e7/index

This example demonstrates the essential events that a smart contract should emit to enable the SnowRail agent (x402) to react to payment and swap operations. These events provide on-chain visibility into the system's state and agent permissions.

```Solidity
pragma solidity ^0.8.0;

contract SnowRailEvents {
    // Event emitted when a payment is requested
    event PaymentRequested(address indexed payer, address indexed payee, uint256 amount, address token);

    // Event emitted when a payment is successfully executed
    event PaymentExecuted(address indexed payer, address indexed payee, uint256 amount, address token);

    // Event emitted when authorization is given to perform a swap
    event SwapAuthorized(address indexed owner, address indexed fromToken, address indexed toToken, uint256 maxAmount);

    // Event emitted when a swap is successfully executed
    event SwapExecuted(address indexed swapper, address indexed fromToken, address indexed toToken, uint256 amount);

    // Event emitted when a payment fails
    event PaymentFailed(address indexed payer, address indexed payee, uint256 amount, address token, string reason);

    // Placeholder for actual contract logic
    // ... functions to request payment, authorize swap, etc. ...
}
```

--------------------------------

### Authorize Swap Function and Event

Source: https://chatgpt.com/share/692a6fad-cf18-8012-b784-5366b9c093e7/index

This snippet defines a function to authorize a token swap and the corresponding event emitted onchain. The `authorizeSwap` function takes token addresses and a maximum amount, and the `SwapAuthorized` event logs this authorization. The agent uses this event to know it can perform a swap.

```solidity
function authorizeSwap(address fromToken, address toToken, uint256 maxAmount)

emits SwapAuthorized(msg.sender, fromToken, toToken, maxAmount);

// ... implementation details
```

```solidity
event SwapAuthorized(address indexed owner, address indexed fromToken, address indexed toToken, uint256 maxAmount);
```

--------------------------------

### ERC-20 Token Interface for Avalanche

Source: https://chatgpt.com/share/692a6fad-cf18-8012-b784-5366b9c093e7/index

This interface defines standard ERC-20 functions required to interact with various tokens on the Avalanche C-Chain, such as reading balances, approving spending, and checking allowances. The SnowRail agent uses this interface to manage token assets.

```solidity
interface IERC20 {
    function name() external view returns (string);
    function symbol() external view returns (string);
    function decimals() external view returns (uint8);
    function totalSupply() external view returns (uint256);
    function balanceOf(address account) external view returns (uint256);
    function transfer(address recipient, uint256 amount) external returns (bool);
    function allowance(address owner, address spender) external view returns (uint256);
    function approve(address spender, uint256 amount) external returns (bool);
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
}
```

--------------------------------

### DEX Router Interface for Swaps

Source: https://chatgpt.com/share/692a6fad-cf18-8012-b784-5366b9c093e7/index

This interface represents a Decentralized Exchange (DEX) router, such as Trader Joe or Pangolin, on Avalanche. The SnowRail agent uses this interface to execute token swaps (e.g., AVAX to USDC) when authorized by the Treasury contract, facilitating the payment process when direct USDC funds are unavailable.

```solidity
interface IJoeRouter2 {
    function swapExactTokensForTokens(
        uint256 amountIn,
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external returns (uint256[] memory);

    function getAmountsOut(uint256 amountIn, address[] calldata path) external view returns (uint256[] memory);
    // Other relevant functions for interacting with the DEX
}
```

--------------------------------

### SnowRail Treasury Contract Structure

Source: https://chatgpt.com/share/692a6fad-cf18-8012-b784-5366b9c093e7/index

The SnowRailTreasury contract manages balances, payment requests, and swap authorizations. It emits events to track the state of payments and authorizations, providing a transparent and governable onchain flow for the agent. This contract is central to the Level 2 'Pro' implementation.

```solidity
contract SnowRailTreasury {
    // State variables for balances, etc.

    event PaymentRequested(address indexed payer, address indexed recipient, uint256 amount, address token);
    event SwapAuthorized(address indexed owner, address indexed fromToken, address indexed toToken, uint256 maxAmount);
    event PaymentCompleted(address indexed paymentId);
    event PaymentFailed(address indexed paymentId, string reason);

    function requestPayment(address recipient, uint256 amount, address token) public {
        // ... emit PaymentRequested
    }

    function authorizeSwap(address fromToken, address toToken, uint256 maxAmount) public {
        // ... emit SwapAuthorized
    }

    function executePayment(bytes32 paymentId) public {
        // ... logic to check USDC balance or perform swap using authorized permissions
        // ... emit PaymentCompleted or PaymentFailed
    }
}
```

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