pragma solidity ^0.4.21;



// ----------------------------------------------------------------------------
// Safe maths
// ----------------------------------------------------------------------------
contract SafeMath {
    function safeAdd(uint a, uint b) public pure returns (uint c) {
        c = a + b;
        require(c >= a);
    }
    function safeSub(uint a, uint b) public pure returns (uint c) {
        require(b <= a);
        c = a - b;
    }
    function safeMul(uint a, uint b) public pure returns (uint c) {
        c = a * b;
        require(a == 0 || c / a == b);
    }
    function safeDiv(uint a, uint b) public pure returns (uint c) {
        require(b > 0);
        c = a / b;
    }
}


// ----------------------------------------------------------------------------
// ERC Token Standard #20 Interface
// ----------------------------------------------------------------------------
contract TokenERC20 {
    function totalSupply() public view returns (uint);
    function balanceOf(address tokenOwner) public view returns (uint balance);
    function allowance(address tokenOwner, address spender) public view returns (uint remaining);
    function transfer(address to, uint tokens) public returns (bool success);
    function approve(address spender, uint tokens) public returns (bool success);
    function transferFrom(address from, address to, uint tokens) public returns (bool success);

    event Transfer(address indexed from, address indexed to, uint tokens);
    event Approval(address indexed tokenOwner, address indexed spender, uint 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);
        _;
    }

    function transferOwnership(address _newOwner) public onlyOwner {
        newOwner = _newOwner;
    }
    function acceptOwnership() public {
        require(msg.sender == newOwner);
        emit OwnershipTransferred(owner, newOwner);
        owner = newOwner;
        newOwner = address(0);
    }
}


// ----------------------------------------------------------------------------
// ERC20 Token, with the addition of symbol, name and decimals
// Receives ETH and generates tokens
// ----------------------------------------------------------------------------
contract AFDTToken is TokenERC20, Owned, SafeMath {
    string public symbol;
    string public  name;
    uint8 public decimals;
    uint public _totalSupply;
  

    mapping(address => uint) public balances;
    mapping(address => mapping(address => uint)) public allowed;
    mapping (address => bool) public frozenAccount;

     /* This generates a public event on the blockchain that will notify clients */
    event FrozenFunds(address target, bool frozen);

     // This notifies clients about the amount burnt
    event Burn(address indexed from, uint256 value);
    /**
    * @dev Fix for the ERC20 short address attack.
    */
    modifier onlyPayloadSize(uint size) {
        assert(msg.data.length >= size + 4);
        _;
    } 


    // ------------------------------------------------------------------------
    // Constructor
    // ------------------------------------------------------------------------
    constructor() public {
        symbol = "AFDTT";
        name = "AFDChain";
        decimals = 8;
        _totalSupply = 2100000000 * 10**uint(decimals);
        owner = 0x1ac6bc75a9e1d32a91e025257eaefc0e8965a16f;
        balances[owner] = _totalSupply;
        emit Transfer(address(0), owner, _totalSupply);
    }


    // ------------------------------------------------------------------------
    // Total supply
    // ------------------------------------------------------------------------
    function totalSupply() public view returns (uint) {
        return safeSub(_totalSupply , balances[address(0)]);
    }


    // ------------------------------------------------------------------------
    // Get the token balance for account `tokenOwner`
    // ------------------------------------------------------------------------
    function balanceOf(address tokenOwner) public view returns (uint 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, uint tokens) onlyPayloadSize(safeMul(2,32)) public  returns (bool success) {
        _transfer(msg.sender, to, tokens);              // makes the transfers
        return true;
    }


    // ------------------------------------------------------------------------
    // Token owner can approve for `spender` to transferFrom(...) `tokens`
    // from the token owner's account
    // recommends that there are no checks for the approval double-spend attack
    // as this should be implemented in user interfaces 
    // ------------------------------------------------------------------------
    function approve(address spender, uint tokens) public 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, uint tokens)  onlyPayloadSize(safeMul(3,32)) public returns (bool success) {

        require (to != 0x0);                               // Prevent transfer to 0x0 address. Use burn() instead
        require (balances[from] >= tokens);               // Check if the sender has enough
        require (safeAdd(balances[to] , tokens) >= balances[to]); // Check for overflows
        require(!frozenAccount[from]);                     // Check if sender is frozen
        require(!frozenAccount[to]);                       // Check if recipient is frozen

        balances[from] = safeSub(balances[from], tokens);
        allowed[from][msg.sender] = safeSub(allowed[from][msg.sender], tokens);
        balances[to] = safeAdd(balances[to], 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 view returns (uint 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, uint 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;
    }



     /// @notice `freeze? Prevent | Allow` `from` from sending & receiving tokens
    /// @param from Address to be frozen
    /// @param freeze either to freeze it or not
    function freezeAccount(address from, bool freeze) onlyOwner public {
        frozenAccount[from] = freeze;
        emit FrozenFunds(from, freeze);
    }
    

    /* Internal transfer, only can be called by this contract */
    function _transfer(address _from, address _to, uint _value) internal {
        require (_to != 0x0);                               // Prevent transfer to 0x0 address. Use burn() instead
        require (balances[_from] >= _value);               // Check if the sender has enough
        require (safeAdd(balances[_to] , _value) >= balances[_to]); // Check for overflows
        require(!frozenAccount[_from]);                     // Check if sender is frozen
        require(!frozenAccount[_to]);                       // Check if recipient is frozen
        
        balances[_from] = safeSub(balances[_from], _value);
        balances[_to] = safeAdd(balances[_to], _value);              
        emit Transfer(_from, _to, _value);
    }

    /**
     * Destroy tokens
     *
     * Remove `_value` tokens from the system irreversibly
     *
     * @param _value the amount of money to burn
     */
    function burn(uint256 _value) public returns (bool success) {
        require(balances[msg.sender] >= _value);   // Check if the sender has enough
        balances[msg.sender] = safeSub(balances[msg.sender], _value); // Subtract from the sender
        _totalSupply = safeSub(_totalSupply, _value); // Updates totalSupply
                     
        emit Burn(msg.sender, _value);
        return true;
    }

    /**
     * Destroy tokens from other account
     *
     * Remove `_value` tokens from the system irreversibly on behalf of `_from`.
     *
     * @param _from the address of the sender
     * @param _value the amount of money to burn
     */
    function burnFrom(address _from, uint256 _value) public returns (bool success) {
        require(balances[_from] >= _value);                // Check if the targeted balance is enough
        require(_value <= allowed[_from][msg.sender]);    // Check allowance
        balances[_from] = safeSub(balances[_from], _value); // Subtract from the targeted balance
        allowed[_from][msg.sender] = safeSub(allowed[_from][msg.sender], _value); // Subtract from the sender's allowance
        _totalSupply = safeSub(_totalSupply, _value);  // Update totalSupply
        emit Burn(_from, _value);
        return true;
    }

}