// File: src/Lock.sol



pragma solidity ^0.8.0;

import "../lib/openzeppelin-contracts/contracts/token/ERC20/IERC20.sol";
import "./Oracle.sol";
import "./interfaces/IOracle.sol";

contract Lock {
    IERC20 public underlying;
    IOracle public oracle;

    mapping(address => uint256) public balances;

    constructor(IERC20 _underlying, IOracle _oracle) {
        underlying = _underlying;
        oracle = _oracle;
    }

    function lock(uint256 amt) public {
        require(!oracle.isExpired(), "Merge has already happened");

        underlying.transferFrom(msg.sender, address(this), amt);
        balances[msg.sender] += amt;
    }

    function unlock(uint256 amt) public {
        require(oracle.isExpired(), "Merge has not happened yet");

        balances[msg.sender] -= amt;
        underlying.transfer(msg.sender, amt);
    }
}

// File: lib/openzeppelin-contracts/contracts/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.6.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);

    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `to`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address to, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `from` to `to` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) external returns (bool);
}

// File: src/Oracle.sol



pragma solidity ^0.8.0;

import "./interfaces/IOracle.sol";

contract ForkOracle is IOracle {
    bool expired = false;
    uint256 deployTime;

    uint256 MIN_RANDAO = 2 ** 128;

    constructor() {
        deployTime = block.timestamp;
    }

    function setExpired() public {
        require((block.timestamp - deployTime > 365 * 24 * 60 * 60) || isExpired());
        expired = true;
    }

    function isExpired() public view returns (bool) {
        return expired || block.chainid != 1 || block.difficulty >= MIN_RANDAO;
    }

    function isRedeemable(bool isPos) public view returns (bool) {
        return isPos == (block.chainid == 1);
    }
}

// File: src/interfaces/IOracle.sol



pragma solidity >=0.5.16;

interface IOracle {
    function isExpired() external view returns (bool);

    function isRedeemable(bool future0) external view returns (bool);
}