// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

import {MerkleProof} from "@openzeppelin/contracts/utils/cryptography/MerkleProof.sol";

import {BasePolicy} from "../../policy/BasePolicy.sol";

/// @title MerkleProofPolicy
/// @notice A policy contract enforcing merkle proof validation.
/// Only if they are part of the tree
contract MerkleProofPolicy is BasePolicy {
    // a mapping of addresses that have already enforced
    mapping(address => bool) public enforcedAddresses;

    /// @notice Deploy an instance of MerkleProofPolicy
    // solhint-disable-next-line no-empty-blocks
    constructor() payable {}

    /// @notice Enforce an user based on being part of the tree
    /// @dev Throw if the proof is not valid or the user has already been enforced
    /// @param _subject The user's Ethereum address.
    /// @param _evidence The proof that the user is part of the tree.
    function _enforce(address _subject, bytes calldata _evidence) internal override {
        // ensure that the user has not been enforced yet
        if (enforcedAddresses[_subject]) {
            revert AlreadyEnforced();
        }

        enforcedAddresses[_subject] = true;

        super._enforce(_subject, _evidence);
    }

    /// @notice Get the trait of the Policy
    /// @return The type of the Policy
    function trait() public pure override returns (string memory) {
        return "MerkleProof";
    }
}