pragma solidity ^0.5.0;

interface ApproveAndCallFallBack {
    function receiveApproval(address from, uint256 _amount, address _token, bytes calldata _data) external;
}

contract Token {

    /// @return total amount of tokens
    function totalSupply() view public returns (uint256 supply) {}

    /// @param _owner The address from which the balance will be retrieved
    /// @return The balance
    function balanceOf(address _owner) public view returns (uint256 balance) {}

    /// @notice send `_value` token to `_to` from `msg.sender`
    /// @param _to The address of the recipient
    /// @param _value The amount of token to be transferred
    /// @return Whether the transfer was successful or not
    function transfer(address _to, uint256 _value) public returns (bool success) {}

    /// @notice send `_value` token to `_to` from `_from` on the condition it is approved by `_from`
    /// @param _from The address of the sender
    /// @param _to The address of the recipient
    /// @param _value The amount of token to be transferred
    /// @return Whether the transfer was successful or not
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {}

    /// @notice `msg.sender` approves `_addr` to spend `_value` tokens
    /// @param _spender The address of the account able to transfer the tokens
    /// @param _value The amount of wei to be approved for transfer
    /// @return Whether the approval was successful or not
    function approve(address _spender, uint256 _value) public returns (bool success) {}

    /// @param _owner The address of the account owning tokens
    /// @param _spender The address of the account able to transfer the tokens
    /// @return Amount of remaining tokens allowed to spent
    function allowance(address _owner, address _spender) public view returns (uint256 remaining) {}

    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);
}



contract StandardToken is Token {

    function transfer(address _to, uint256 _value) public returns (bool success) {
        //Default assumes totalSupply can't be over max (2^256 - 1).
        //If your token leaves out totalSupply and can issue more tokens as time goes on, you need to check if it doesn't wrap.
        //Replace the if with this one instead.
        //if (balances[msg.sender] >= _value && balances[_to] + _value > balances[_to]) {
        if (balances[msg.sender] >= _value && _value > 0) {
            balances[msg.sender] -= _value;
            balances[_to] += _value;
            emit Transfer(msg.sender, _to, _value);
            return true;
        } else { return false; }
    }

    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
        if (msg.sender == _from){
            return transfer(_to, _value);
        }else{
            //same as above. Replace this line with the following if you want to protect against wrapping uints.
            //if (balances[_from] >= _value && allowed[_from][msg.sender] >= _value && balances[_to] + _value > balances[_to]) {
            if (balances[_from] >= _value && allowed[_from][msg.sender] >= _value && _value > 0) {
                balances[_to] += _value;
                balances[_from] -= _value;
                allowed[_from][msg.sender] -= _value;
                emit Transfer(_from, _to, _value);
                return true;
            } else { return false; }
        }

    }

    function balanceOf(address _owner) public view returns (uint256 balance) {
        return balances[_owner];
    }

    function approve(address _spender, uint256 _value) public returns (bool success) {
        allowed[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }

    function allowance(address _owner, address _spender) public view returns (uint256 remaining) {
      return allowed[_owner][_spender];
    }

    function totalSupply() public view returns (uint256){
      return total;
    }

    mapping (address => uint256) balances;
    mapping (address => mapping (address => uint256)) allowed;
    uint256 total;
}


//name this contract whatever you'd like
contract WalletToken is StandardToken {

    function () external {
        //if ether is sent to this address, send it back.
        revert();
    }

    /* Public variables of the token */

    /*
    NOTE:
    The following variables are OPTIONAL vanities. One does not have to include them.
    They allow one to customise the token contract & in no way influences the core functionality.
    Some wallets/interfaces might not even bother to look at this information.
    */
    string public name;                   //fancy name: eg Simon Bucks
    uint8 public decimals;                //How many decimals to show. ie. There could 1000 base units with 3 decimals. Meaning 0.980 SBX = 980 base units. It's like comparing 1 wei to 1 ether.
    string public symbol;                 //An identifier: eg SBX
    string public version = 'H1.0';       //human 0.1 standard. Just an arbitrary versioning scheme.

//
// CHANGE THESE VALUES FOR YOUR TOKEN
//

//make sure this function name matches the contract name above. So if you're token is called TutorialToken, make sure the //contract name above is also TutorialToken instead of ERC20Token

    constructor() public {
        balances[msg.sender] = 1*10**27;               // Give the creator all initial tokens
        total = 1*10**27;   // Update total supply
        name = "Wallet Token";        // Set the name for display purposes
        decimals = 18;           // Amount of decimals for display purposes
        symbol = "WT";         // Set the symbol for display purposes
    }

    /* Approves and then calls the receiving contract */
    function approveAndCall(address _spender, uint256 _value, bytes memory _extraData) public returns (bool success) {
      if (!approve(_spender, _value)) revert();

      ApproveAndCallFallBack(_spender).receiveApproval(
          msg.sender,
          _value,
          address(this),
          _extraData
      );

      return true;
    }
}