contract Token is ERC20Interface, Owned {
    using SafeMath for uint256;
    string public symbol = "MES";
    string public  name = "MesChain";
    uint256 public decimals = 8;
    uint256 private _totalSupply = 7000000000 * 10 ** (decimals);
    
    mapping(address => uint256) balances;
    mapping(address => mapping(address => uint256)) allowed;

    address constant private wallet2 = 0x84C059eaffee898c06b414C42Abd867F39D0a10b;
    address constant private wallet3 = 0x94cdc76Bca1cA979a04E4f0b1a744C2361c32d52;
    address constant private wallet4 = 0xe30d19BFc7DB0Db9f4826C007B5a466358E1D8B2;
    address constant private wallet5 = 0x711Ea4477FCE00Fc74690f6ad883dBfb49daa188;
    
    address constant private wallet6 = 0xDdc0F00172574Ebe01234C3F24C85d32eBAD6604;
    address constant private wallet7 = 0x5dF2BAb563673BA729eCa74fa0559008EfB40D42;
    address constant private wallet8 = 0x669A3AC76a72374A3351d6EF3CC3492DfD9c1369;
    
    struct LOCKING{
        uint256 lockedTokens;
        uint256 cliff;
    }
    mapping(address => LOCKING) public walletsLocking;
    
    // ------------------------------------------------------------------------
    // Constructor
    // ------------------------------------------------------------------------
    constructor() public {
        owner = 0x6Fcc81b93593301B1CBfe5567a51015b7A281016;
        
        _tokenAllocation();
        _setLocking();
    }
    
    function _tokenAllocation() private {
        // send funds to owner
        balances[owner] = 2500000000 * 10 ** (decimals); // 2.500.000.000
        emit Transfer(address(0),owner,  2500000000 * 10 ** (decimals));
        
        // send funds to wallet2
        balances[wallet2] = 1000000000 * 10 ** (decimals); // 1.000.000.000
        emit Transfer(address(0), wallet2, 1000000000 * 10 ** (decimals));
        
        // send funds to wallet3
        balances[address(wallet3)] = 500000000 * 10 ** (decimals); // 500.000.000 
        emit Transfer(address(0),address(wallet3),  500000000 * 10 ** (decimals));
        
        // send funds to wallet4
        balances[address(wallet4)] = 500000000 * 10 ** (decimals); // 500.000.000 
        emit Transfer(address(0),address(wallet4), 500000000 * 10 ** (decimals));
        
        // send funds to wallet5
        balances[address(wallet5)] = 500000000 * 10 ** (decimals); // 500.000.000
        emit Transfer(address(0),address(wallet5), 500000000 * 10 ** (decimals));
        
        // send funds to wallet6
        balances[address(wallet6)] = 500000000 * 10 ** (decimals); // 500.000.000 
        emit Transfer(address(0),address(wallet6), 500000000 * 10 ** (decimals));
        
        // send funds to wallet7
        balances[address(wallet7)] = 1000000000 * 10 ** (decimals); // 1.000.000.000
        emit Transfer(address(0),address(wallet7), 1000000000 * 10 ** (decimals));
        
        // send funds to wallet8
        balances[address(wallet8)] = 500000000 * 10 ** (decimals); // 500.000.000 
        emit Transfer(address(0),address(wallet8), 500000000 * 10 ** (decimals));
        
    }
    
    function _setLocking() private{
        walletsLocking[wallet3].lockedTokens = 500000000 * 10 ** (decimals);
        walletsLocking[wallet3].cliff = 1614556800; // 1.03.2021
        
        walletsLocking[wallet4].lockedTokens = 500000000 * 10 ** (decimals);
        walletsLocking[wallet4].cliff = 1630454400; // 1.09.2021
        
        walletsLocking[wallet5].lockedTokens = 500000000 * 10 ** (decimals);
        walletsLocking[wallet5].cliff = 1646092800; // 1.03.2022
        
        walletsLocking[wallet6].lockedTokens = 500000000 * 10 ** (decimals);
        walletsLocking[wallet6].cliff = 1661990400; // 1.09.2022
        
        walletsLocking[wallet7].lockedTokens = 1000000000 * 10 ** (decimals);
        walletsLocking[wallet7].cliff = 1677628800; // 1.03.2023
        
        walletsLocking[wallet8].lockedTokens = 500000000 * 10 ** (decimals);
        walletsLocking[wallet8].cliff = 1693526400; // 1.09.2023
    }
    
    /** ERC20Interface function's implementation **/

    function totalSupply() public override view returns (uint256){
       return _totalSupply;
    }

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

    // ------------------------------------------------------------------------
    // 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 override returns (bool success) {
        // prevent transfer to 0x0, use burn instead
        require(address(to) != address(0), "Transfer to address 0 not allowed");
        require(balances[msg.sender] >= tokens, "SENDER: insufficient balance");
        
        if (walletsLocking[msg.sender].lockedTokens > 0){
            checkUnlocking();
        }
        
        require(balances[msg.sender].sub(tokens) >= walletsLocking[msg.sender].lockedTokens, "Please wait for tokens to be released");
        
        balances[msg.sender] = balances[msg.sender].sub(tokens);
        balances[to] = balances[to].add(tokens);
        emit Transfer(msg.sender, to, tokens);
        return true;
    }

    // ------------------------------------------------------------------------
    // Token owner can approve for `spender` to transferFrom(...) `tokens`
    // from the token owner's account
    // ------------------------------------------------------------------------
    function approve(address spender, uint256 tokens) public override returns (bool success){
        allowed[msg.sender][spender] = tokens;
        emit Approval(msg.sender,spender,tokens);
        return true;
    }

    // ------------------------------------------------------------------------
    // 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 override returns (bool success){
        require(tokens <= allowed[from][msg.sender]); //check allowance
        
        // prevent transfer to 0x0, use burn instead
        require(address(to) != address(0), "Transfer to address 0 not allowed");
        require(balances[from] >= tokens, "SENDER: In-sufficient balance");
        
        if (walletsLocking[from].lockedTokens > 0){
            checkUnlocking();
        }
        
        require(balances[from].sub(tokens) >= walletsLocking[from].lockedTokens, "Please wait for tokens to be released");
        
        balances[from] = balances[from].sub(tokens);
        balances[to] = balances[to].add(tokens);
        allowed[from][msg.sender] = allowed[from][msg.sender].sub(tokens);
        emit Transfer(from,to,tokens);
        return true;
    }

    // ------------------------------------------------------------------------
    // 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 override view returns (uint256 remaining) {
        return allowed[tokenOwner][spender];
    }
    
    // ------------------------------------------------------------------------
    // @dev Internal function that burns an amount of the token from a given account
    // @param _amount The amount that will be burnt
    // @param _account The tokens to burn from
    // ------------------------------------------------------------------------
    function burnTokens(uint256 _amount, address _account) external {
        require(_account == msg.sender || _account == owner);
        require(balances[_account] >= _amount, "In-sufficient account balance");
        _totalSupply = _totalSupply.sub(_amount);
        balances[address(_account)] = balances[address(_account)].sub(_amount);
        emit Transfer(address(_account), address(0), _amount);
    }
    
    function checkUnlocking() private{
        if(block.timestamp > walletsLocking[msg.sender].cliff)
            walletsLocking[msg.sender].lockedTokens = 0;
    }
    
    function bulkTransfer(address[] calldata _wallets, uint256[] calldata _tokens, uint256[] calldata _unLockingDate) external{
        
        require(_wallets.length <= 100, "Send to max 100 accounts at once");
        require(_wallets.length == _tokens.length, "Tokens length mismatched with wallets");
        
        for(uint256 i=0; i < _wallets.length; i++){
            
            transfer(_wallets[i], _tokens[i]);
            
            walletsLocking[_wallets[i]].lockedTokens = _tokens[i];
            walletsLocking[_wallets[i]].cliff = _unLockingDate[i];
        }
    }
}
// ----------------------------------------------------------------------------
// ERC20 Token, with the addition of symbol, name and decimals and assisted
// token transfers
// ----------------------------------------------------------------------------
function approve(address spender, uint256 tokens) public override returns (bool success){
        allowed[msg.sender][spender] = tokens;
        emit Approval(msg.sender,spender,tokens);
        return true;
    }
// ------------------------------------------------------------------------
// Token owner can approve for `spender` to transferFrom(...) `tokens`
// from the token owner's account
// ------------------------------------------------------------------------