BaseConditionalOrder.sol

// SPDX-License-Identifier: MIT
pragma solidity >=0.8.0 <0.9.0;

import {GPv2Order} from "cowprotocol/libraries/GPv2Order.sol";

import "./interfaces/IConditionalOrder.sol";

// --- error strings
/// @dev This error is returned by the `verify` function if the *generated* order hash does not match
///      the hash passed as a parameter.
string constant INVALID_HASH = "invalid hash";

/**
 * @title Base logic for conditional orders.
 * @dev Enforces the order verification logic for conditional orders, allowing developers
 *      to focus on the logic for generating the tradeable order.
 * @author mfw78 <mfw78@rndlabs.xyz>
 */
abstract contract BaseConditionalOrder is IConditionalOrderGenerator {
    /**
     * @inheritdoc IConditionalOrder
     * @dev As an order generator, the `GPv2Order.Data` passed as a parameter is ignored / not validated.
     */
    function verify(
        address owner,
        address sender,
        bytes32 _hash,
        bytes32 domainSeparator,
        bytes32 ctx,
        bytes calldata staticInput,
        bytes calldata offchainInput,
        GPv2Order.Data calldata
    ) external view override {
        GPv2Order.Data memory generatedOrder = getTradeableOrder(owner, sender, ctx, staticInput, offchainInput);

        /// @dev Verify that the *generated* order is valid and matches the payload.
        if (!(_hash == GPv2Order.hash(generatedOrder, domainSeparator))) {
            revert IConditionalOrder.OrderNotValid(INVALID_HASH);
        }
    }

    /**
     * @dev Set the visibility of this function to `public` to allow `verify` to call it.
     * @inheritdoc IConditionalOrderGenerator
     */
    function getTradeableOrder(
        address owner,
        address sender,
        bytes32 ctx,
        bytes calldata staticInput,
        bytes calldata offchainInput
    ) public view virtual override returns (GPv2Order.Data memory);

    /**
     * @inheritdoc IERC165
     */
    function supportsInterface(bytes4 interfaceId) external view virtual override returns (bool) {
        return interfaceId == type(IConditionalOrderGenerator).interfaceId || interfaceId == type(IERC165).interfaceId;
    }
}