/**
 * Source Code first verified at https://etherscan.io on Wednesday, March 20, 2019
 (UTC) */

pragma solidity ^0.4.24;

// ----------------------------------------------------------------------------
// 'learn coin' CROWDSALE token contract
//
// Deployed to : 0xD0FDf2ECd4CadE671a7EE1063393eC0eB90816FD
// Symbol      : LEN
// Name        : len Token
// Total supply: Gazillion
// Decimals    : 18
//
// Enjoy.
//
// (c) by Chen Ying. The MIT Licence.
// ----------------------------------------------------------------------------


// ----------------------------------------------------------------------------
// Safe maths
// ----------------------------------------------------------------------------
contract SafeMath {
    function safeAdd(uint256 a, uint256 b) internal pure returns (uint256 c) {
        c = a + b;
        require(c >= a, "add error");
    }
    function safeSub(uint256 a, uint256 b) internal pure returns (uint256 c) {
        require(b <= a, "sub error");
        c = a - b;
    }
    function safeMul(uint256 a, uint256 b) internal pure returns (uint256 c) {
        c = a * b;
        require(a == 0 || c / a == b, "mul error");
    }
    function safeDiv(uint256 a, uint256 b) internal pure returns (uint256 c) {
        require(b > 0, "div by less than 0");
        c = a / b;
    }
}


// ----------------------------------------------------------------------------
// ERC Token Standard #20 Interface
// https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20-token-standard.md
// ----------------------------------------------------------------------------
contract ERC20Interface {
    function totalSupply() public view returns (uint256);
    function balanceOf(address _owner) public view returns (uint256 balance);
    function allowance(address _owner, address _spender) public view returns (uint256 remaining);
    function transfer(address _to, uint256 _value) public returns (bool success);
    function approve(address _spender, uint256 _value) public returns (bool success);
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success);

    event Transfer(address indexed from, address indexed to, uint256 tokens);
    event Approval(address indexed tokenOwner, address indexed spender, uint256 tokens);
}


// ----------------------------------------------------------------------------
// Contract function to receive approval and execute function in one call
//
// Borrowed from MiniMeToken
// ----------------------------------------------------------------------------
contract ApproveAndCallFallBack {
    function receiveApproval(address from, uint256 tokens, address token, bytes data) public;
}


// ----------------------------------------------------------------------------
// Owned contract
// ----------------------------------------------------------------------------
contract Owned {
    address public owner;
    address public newOwner;

    event OwnershipTransferred(address indexed _from, address indexed _to);

    constructor() public {
        owner = msg.sender;
    }

    modifier onlyOwner {
        require(msg.sender == owner, "not owner");
        _;
    }

    function transferOwnership(address _newOwner) public onlyOwner {
        newOwner = _newOwner;
    }
    function acceptOwnership() public {
        require(msg.sender == newOwner, "not owner");
        emit OwnershipTransferred(owner, newOwner);
        owner = newOwner;
        newOwner = address(0);
    }
}


// ----------------------------------------------------------------------------
// ERC20 Token, with the addition of symbol, name and decimals and assisted
// token transfers
// ----------------------------------------------------------------------------
contract LenToken is ERC20Interface, Owned, SafeMath {
    string public symbol;
    string public  name;
    uint8 public decimals;
    uint256 public _totalSupply = 0;
    uint public startDate;
    uint public bonusEnds;
    uint public endDate;

    mapping(address => uint256) balances;
    mapping(address => mapping(address => uint256)) allowed;


    // ------------------------------------------------------------------------
    // Constructor
    // ------------------------------------------------------------------------
    constructor() public {
        symbol = "LEN";
        name = "len Token";
        decimals = 18;
        bonusEnds = now + 1 weeks;
        endDate = now + 7 weeks;

        uint256 initialSupply = 100000000;
        _totalSupply = initialSupply * 10 ** uint256(decimals); // Update total supply with the decimal amount
        balances[msg.sender] = _totalSupply;                    // Give the creator all initial tokens
        emit Transfer(address(0), msg.sender, _totalSupply);
    }


    // ------------------------------------------------------------------------
    // Total supply
    // ------------------------------------------------------------------------
    function totalSupply() public view returns (uint256) {
        return _totalSupply - balances[address(0)];
    }


    // ------------------------------------------------------------------------
    // Get the token balance for account `tokenOwner`
    // ------------------------------------------------------------------------
    function balanceOf(address tokenOwner) public view returns (uint256 balance) {
        return balances[tokenOwner];
    }


    function _transfer(address _from, address _to, uint256 _value) internal { 
        require(_to != 0x0, "Prevent transfer to 0x0 address.");
        // Save this for an assertion in the future
        uint256 previousBalances = balances[_from] + balances[_to];
        balances[_from] = safeSub(balances[_from], _value);
        balances[_to] = safeAdd(balances[_to], _value);
        emit Transfer(_from, _to, _value);
         // Asserts are used to use static analysis to find bugs in your code. They should never fail
        assert(balances[_from] + balances[_to] == previousBalances);
    }
    // ------------------------------------------------------------------------
    // Transfer the balance from token owner's account to `to` account
    // - Owner's account must have sufficient balance to transfer
    // - 0 value transfers are allowed
    // ------------------------------------------------------------------------
    function transfer(address to, uint256 tokens) public returns (bool success) {
        _transfer(msg.sender, to, tokens);
        return true;
    }
    function transferWithDecimals(address to, uint256 tokens) public returns (bool success) {
        _transfer(msg.sender, to, tokens * 10 ** uint256(decimals));
        return true;
    }

    // ------------------------------------------------------------------------
    // Token owner can approve for `spender` to transferFrom(...) `tokens`
    // from the token owner's account
    //
    // https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20-token-standard.md
    // recommends that there are no checks for the approval double-spend attack
    // as this should be implemented in user interfaces
    // ------------------------------------------------------------------------
    function approve(address spender, uint256 tokens) public returns (bool success) {
        allowed[msg.sender][spender] = tokens;
        emit Approval(msg.sender, spender, tokens);
        return true;
    }
    function approveWithDecimals(address spender, uint256 tokens) public returns (bool success) {
        return approve(spender, tokens * 10 ** uint256(decimals));
    }

    // ------------------------------------------------------------------------
    // Transfer `tokens` from the `from` account to the `to` account
    //
    // The calling account must already have sufficient tokens approve(...)-d
    // for spending from the `from` account and
    // - From account must have sufficient balance to transfer
    // - Spender must have sufficient allowance to transfer
    // - 0 value transfers are allowed
    // ------------------------------------------------------------------------
    function transferFrom(address from, address to, uint256 tokens) public returns (bool success) {
        allowed[from][msg.sender] = safeSub(allowed[from][msg.sender], tokens); 
        _transfer(from, to, tokens);
        return true;
    }
    function transferFromWithDecimals(address from, address to, uint256 tokens) public returns (bool success) {
        return transferFrom(from, to, tokens * 10 ** uint256(decimals)) ;
    }

    // ------------------------------------------------------------------------
    // Returns the amount of tokens approved by the owner that can be
    // transferred to the spender's account
    // ------------------------------------------------------------------------
    function allowance(address tokenOwner, address spender) public view returns (uint256 remaining) {
        return allowed[tokenOwner][spender];
    }


    // ------------------------------------------------------------------------
    // Token owner can approve for `spender` to transferFrom(...) `tokens`
    // from the token owner's account. The `spender` contract function
    // `receiveApproval(...)` is then executed
    // ------------------------------------------------------------------------
    function approveAndCall(address spender, uint256 tokens, bytes data) public returns (bool success) {
        allowed[msg.sender][spender] = tokens;
        emit Approval(msg.sender, spender, tokens);
        ApproveAndCallFallBack(spender).receiveApproval(msg.sender, tokens, this, data);
        return true;
    }

    // ------------------------------------------------------------------------
    // 1,000 LEN Tokens per 1 ETH
    // ------------------------------------------------------------------------
    function () public payable {
        require(now >= startDate && now <= endDate, "out of ico date");
        uint256 tokens;
        if (now <= bonusEnds) {
            tokens = msg.value * 1200;
        } else {
            tokens = msg.value * 1000;
        }
        allowed[owner][msg.sender] = tokens;
        emit Approval(msg.sender, owner, tokens);
        transferFrom(owner, msg.sender, tokens);
        owner.transfer(msg.value);
    }



    // ------------------------------------------------------------------------
    // Owner can transfer out any accidentally sent ERC20 tokens
    // ------------------------------------------------------------------------
    function transferAnyERC20Token(address tokenAddress, uint256 tokens) public onlyOwner returns (bool success) {
        return ERC20Interface(tokenAddress).transfer(owner, tokens);
    }
}