BASE-YAS

// SPDX-License-Identifier: MIT pragma solidity ^0.8.0;

contract Escrow { address public buyer; address public seller; address public escrowAgent; uint256 public amount; bool public productDelivered;

enum State { Created, Funded, Shipped, Completed, Refunded }
State public currentState;

modifier onlyBuyer() {
    require(msg.sender == buyer, "Only the buyer can call this");
    _;
}

modifier onlySeller() {
    require(msg.sender == seller, "Only the seller can call this");
    _;
}

modifier onlyEscrowAgent() {
    require(msg.sender == escrowAgent, "Only the escrow agent can call this");
    _;
}

modifier inState(State _state) {
    require(currentState == _state, "Invalid state");
    _;
}

constructor(address _buyer, address _seller, address _escrowAgent) {
    buyer = _buyer;
    seller = _seller;
    escrowAgent = _escrowAgent;
    currentState = State.Created;
}

function fund() public payable onlyBuyer inState(State.Created) {
    amount = msg.value;
    currentState = State.Funded;
}

function confirmShipment() public onlySeller inState(State.Funded) {
    currentState = State.Shipped;
}

function confirmDelivery() public onlyBuyer inState(State.Shipped) {
    productDelivered = true;
    payable(seller).transfer(amount);
    currentState = State.Completed;
}

function refund() public onlyEscrowAgent inState(State.Funded) {
    payable(buyer).transfer(amount);
    currentState = State.Refunded;
}

}