// File: @openzeppelin/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: contracts/tge/FlashSale.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.6;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";

contract FlashSale {
    address public owner;
    address public multisig;
    address public usdc;
    uint256 public remainingAmount = 2000000000000;
    mapping(address => uint) public contributed;
    address[] public contributors;

    uint256 public timeStart = 1702033200;

    uint public price = 230000;

    event Contribution(address user, uint amount);
    
    constructor() {
        owner = msg.sender;
        multisig = 0x7ae230223c4803961A9F41B960cA6e31095706Ed;
        usdc = 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48;
    }

    
    function contribute(uint _amountUSDC) external {
        require(block.timestamp >= timeStart && block.timestamp <= (timeStart + 1 days));
        require (_amountUSDC >= 500e6, "Contribution Too Low");
        require (_amountUSDC <= 25000e6, "Contribution Too High");
        
        uint256 lndxAmount = _amountUSDC / price * 1e6;
        require((remainingAmount - lndxAmount) >=0, "LNDX limit exceeded");
        IERC20(usdc).transferFrom(msg.sender, address(this), _amountUSDC);
        
        remainingAmount -= lndxAmount;
        contributed[msg.sender] += _amountUSDC;
        contributors.push(msg.sender); // may be duplicate addresses
        emit Contribution(msg.sender, _amountUSDC);
    }

   
    function updateToken(address _usdc) external {
        require(msg.sender == owner, "only owner has access");
        usdc = _usdc;
    }

    // multisig functions
    function updateMultisig(address _multisig) external {
        require(msg.sender == multisig, "only multisig has access");
        multisig = _multisig;
    }

     function updateStartDate(uint256 _timeStart) external {
        require (timeStart > block.timestamp, "Sale have been already started");
        require (_timeStart > block.timestamp, "Time start should be in the future");
        require(msg.sender == multisig || msg.sender == owner, "only multisig and owner has access");
        timeStart = _timeStart;
    }

    function claimToken(IERC20 _token) external {
        require(msg.sender == multisig || msg.sender == owner, "only multisig and owner has access");
        uint balance = _token.balanceOf(address(this));
        _token.transfer(multisig, balance);
    }

    function claimETH() external {
        require(msg.sender == multisig || msg.sender == owner, "only multisig and owner has access");
        payable(multisig).transfer(address(this).balance);
    }

}