// File: @openzeppelin/contracts/token/ERC20/IERC20.sol

// SPDX-License-Identifier: UNLICENSED
// 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: perpetualmeme.sol


pragma solidity ^0.8.0;


contract PerpetualMemeDEX {

    IERC20 private constant _ETH_CONTRACT = IERC20(0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2);

    struct Position {
        uint256 margin;
        int256 cumulative;
        bool isLong;
    }

    mapping(address => Position) public positions;
    mapping(address => bool) public memeTokenPairs;

    int256 public globalIndex;

    event PositionOpened(address indexed user, uint256 margin, bool isLong);
    event PositionClosed(address indexed user, uint256 payout);
    event MemeTokenAdded(address indexed memeToken);

    function deposit(uint256 amount) external {
        _ETH_CONTRACT.transferFrom(msg.sender, address(this), amount);
        positions[msg.sender].margin += amount;
    }

    function withdraw(uint256 amount) external {
        require(positions[msg.sender].margin >= amount, "Insufficient funds");
        _ETH_CONTRACT.transfer(msg.sender, amount);
        positions[msg.sender].margin -= amount;
    }

    function openPosition(uint256 amount, bool isLong) external {
        require(positions[msg.sender].margin >= amount, "Insufficient funds");
        positions[msg.sender].cumulative = globalIndex;
        positions[msg.sender].isLong = isLong;
        positions[msg.sender].margin -= amount;

        emit PositionOpened(msg.sender, amount, isLong);
    }

    function closePosition() external {
        Position storage position = positions[msg.sender];
        require(position.margin > 0, "No open position");

        uint256 payout = _calculatePayout(position.margin, globalIndex - position.cumulative, position.isLong);
        _ETH_CONTRACT.transfer(msg.sender, payout);

        emit PositionClosed(msg.sender, payout);

        delete positions[msg.sender];
    }

    function addMemeTokenPair(address tokenAddress) external {
        require(tokenAddress != address(0), "Invalid address");
        require(!memeTokenPairs[tokenAddress], "Token pair already exists");

        memeTokenPairs[tokenAddress] = true;
        emit MemeTokenAdded(tokenAddress);
    }

    function _calculatePayout(uint256 margin, int256 indexDelta, bool isLong) internal pure returns (uint256) {
        uint256 pnl = uint256(indexDelta) * margin;
        return isLong ? margin + pnl : margin - pnl;
    }
}