// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.6.0) (crosschain/CrossChainEnabled.sol)

pragma solidity ^0.8.4;

import "./errors.sol";

/**
 * @author OpenZeppelin
 * @dev LibOptimism was removed from the OpenZeppelin Contracts library as of v4.7.0
 * @dev Provides information for building cross-chain aware contracts. This
 * abstract contract provides accessors and modifiers to control the execution
 * flow when receiving cross-chain messages.
 *
 * Actual implementations of cross-chain aware contracts, which are based on
 * this abstraction, will have to inherit from a bridge-specific
 * specialization. Such specializations are provided under
 * `crosschain/<chain>/CrossChainEnabled<chain>.sol`.
 *
 * _Available since v4.6._
 */
abstract contract CrossChainEnabled {
    /**
     * @dev Throws if the current function call is not the result of a
     * cross-chain execution.
     */
    modifier onlyCrossChain() {
        if (!_isCrossChain()) revert NotCrossChainCall();
        _;
    }

    /**
     * @dev Throws if the current function call is not the result of a
     * cross-chain execution initiated by `account`.
     */
    modifier onlyCrossChainSender(address expected) {
        address actual = _crossChainSender();
        if (expected != actual)
            revert InvalidCrossChainSender(actual, expected);
        _;
    }

    /**
     * @dev Returns whether the current function call is the result of a
     * cross-chain message.
     */
    function _isCrossChain() internal view virtual returns (bool);

    /**
     * @dev Returns the address of the sender of the cross-chain message that
     * triggered the current function call.
     *
     * IMPORTANT: Should revert with `NotCrossChainCall` if the current function
     * call is not the result of a cross-chain message.
     */
    function _crossChainSender() internal view virtual returns (address);
}