// SPDX-License-Identifier: MIT OR Apache-2.0
pragma solidity >=0.6.11;

// ============ Internal Imports ============
import {IInterchainGasPaymaster} from "../interfaces/IInterchainGasPaymaster.sol";
import {IMailbox} from "../interfaces/IMailbox.sol";

// ============ External Imports ============
import {OwnableUpgradeable} from "@openzeppelin/contracts-upgradeable/access/OwnableUpgradeable.sol";

abstract contract HyperlaneConnectionClient is OwnableUpgradeable {
    // ============ Mutable Storage ============

    IMailbox public mailbox;
    // Interchain Gas Paymaster contract. The relayer associated with this contract
    // must be willing to relay messages dispatched from the current Outbox contract,
    // otherwise payments made to the paymaster will not result in relayed messages.
    IInterchainGasPaymaster public interchainGasPaymaster;

    uint256[48] private __GAP; // gap for upgrade safety

    // ============ Events ============

    /**
     * @notice Emitted when a new mailbox is set.
     * @param mailbox The address of the mailbox contract
     */
    event MailboxSet(address indexed mailbox);

    /**
     * @notice Emitted when a new Interchain Gas Paymaster is set.
     * @param interchainGasPaymaster The address of the Interchain Gas Paymaster.
     */
    event InterchainGasPaymasterSet(address indexed interchainGasPaymaster);

    // ============ Modifiers ============

    /**
     * @notice Only accept messages from an Hyperlane Mailbox contract
     */
    modifier onlyMailbox() {
        require(msg.sender == address(mailbox), "!mailbox");
        _;
    }

    // ======== Initializer =========

    function __HyperlaneConnectionClient_initialize(address _mailbox)
        internal
        onlyInitializing
    {
        _setMailbox(_mailbox);
        __Ownable_init();
    }

    function __HyperlaneConnectionClient_initialize(
        address _mailbox,
        address _interchainGasPaymaster
    ) internal onlyInitializing {
        _setInterchainGasPaymaster(_interchainGasPaymaster);
        __HyperlaneConnectionClient_initialize(_mailbox);
    }

    // ============ External functions ============

    /**
     * @notice Sets the address of the application's Mailbox.
     * @param _mailbox The address of the Mailbox contract.
     */
    function setMailbox(address _mailbox) external virtual onlyOwner {
        _setMailbox(_mailbox);
    }

    /**
     * @notice Sets the address of the application's InterchainGasPaymaster.
     * @param _interchainGasPaymaster The address of the InterchainGasPaymaster contract.
     */
    function setInterchainGasPaymaster(address _interchainGasPaymaster)
        external
        virtual
        onlyOwner
    {
        _setInterchainGasPaymaster(_interchainGasPaymaster);
    }

    // ============ Internal functions ============

    /**
     * @notice Sets the address of the application's InterchainGasPaymaster.
     * @param _interchainGasPaymaster The address of the InterchainGasPaymaster contract.
     */
    function _setInterchainGasPaymaster(address _interchainGasPaymaster)
        internal
    {
        interchainGasPaymaster = IInterchainGasPaymaster(
            _interchainGasPaymaster
        );
        emit InterchainGasPaymasterSet(_interchainGasPaymaster);
    }

    /**
     * @notice Modify the contract the Application uses to validate Inbox contracts
     * @param _mailbox The address of the mailbox contract
     */
    function _setMailbox(address _mailbox) internal {
        mailbox = IMailbox(_mailbox);
        emit MailboxSet(_mailbox);
    }
}