pragma solidity ^0.4.16;

interface tokenRecipient { function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData) external; }

contract TokenERC20 {
  address public owner;

  // Public variables of the token
  string public name;
  string public symbol;
  uint8 public decimals = 18;
  // 18 decimals is the strongly suggested default, avoid changing it
  uint256 public totalSupply;

  // This creates an array with all balances
  mapping (address => uint256) public balanceOf;
  mapping (address => mapping (address => uint256)) public allowance;

  // This generates a public event on the blockchain that will notify clients
  event Transfer(address indexed from, address indexed to, uint256 value);

  // This notifies clients about the amount burnt
  event Burn(address indexed from, uint256 value);

  /**
   * Constructor function
   *
   * Initializes contract with initial supply tokens to the creator of the contract
   */
  function TokenERC20(
    uint256 initialSupply,
    string tokenName,
    string tokenSymbol
  ) public {
    totalSupply = initialSupply * 10 ** uint256(decimals);  // Update total supply with the decimal amount
    balanceOf[msg.sender] = totalSupply;                // Give the creator all initial tokens
    name = tokenName;                                   // Set the name for display purposes
    symbol = tokenSymbol;                               // Set the symbol for display purposes
    owner = msg.sender;
  }

  /**
   * Internal transfer, only can be called by this contract
   */
  function _transfer(address _from, address _to, uint _value) internal {
    // Prevent transfer to 0x0 address. Use burn() instead
    require(_to != 0x0);
    // Check if the sender has enough
    require(balanceOf[_from] >= _value);
    // Check for overflows
    require(balanceOf[_to] + _value >= balanceOf[_to]);
    // Save this for an assertion in the future
    uint previousBalances = balanceOf[_from] + balanceOf[_to];
    // Subtract from the sender
    balanceOf[_from] -= _value;
    // Add the same to the recipient
    balanceOf[_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(balanceOf[_from] + balanceOf[_to] == previousBalances);
  }

  /**
   * Transfer tokens
   *
   * Send `_value` tokens to `_to` from your account
   *
   * @param _to The address of the recipient
   * @param _value the amount to send
   */
  function transfer(address _to, uint256 _value) public {
    _transfer(msg.sender, _to, _value);
  }

  /**
   * Transfer tokens from other address
   *
   * Send `_value` tokens to `_to` on behalf of `_from`
   *
   * @param _from The address of the sender
   * @param _to The address of the recipient
   * @param _value the amount to send
   */
  function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
    require(_value <= allowance[_from][msg.sender]);     // Check allowance
    allowance[_from][msg.sender] -= _value;
    _transfer(_from, _to, _value);
    return true;
  }

  /**
   * Set allowance for other address
   *
   * Allows `_spender` to spend no more than `_value` tokens on your behalf
   *
   * @param _spender The address authorized to spend
   * @param _value the max amount they can spend
   */
  function approve(address _spender, uint256 _value) public
  returns (bool success) {
    allowance[msg.sender][_spender] = _value;
    return true;
  }

  /**
   * Set allowance for other address and notify
   *
   * Allows `_spender` to spend no more than `_value` tokens on your behalf, and then ping the contract about it
   *
   * @param _spender The address authorized to spend
   * @param _value the max amount they can spend
   * @param _extraData some extra information to send to the approved contract
   */
  function approveAndCall(address _spender, uint256 _value, bytes _extraData)
  public
  returns (bool success) {
    tokenRecipient spender = tokenRecipient(_spender);
    if (approve(_spender, _value)) {
      spender.receiveApproval(msg.sender, _value, this, _extraData);
      return true;
    }
  }

  /**
   * 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(balanceOf[msg.sender] >= _value);   // Check if the sender has enough
    balanceOf[msg.sender] -= _value;            // Subtract from the sender
    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(balanceOf[_from] >= _value);                // Check if the targeted balance is enough
    require(_value <= allowance[_from][msg.sender]);    // Check allowance
    balanceOf[_from] -= _value;                         // Subtract from the targeted balance
    allowance[_from][msg.sender] -= _value;             // Subtract from the sender's allowance
    totalSupply -= _value;                              // Update totalSupply
    emit Burn(_from, _value);
    return true;
  }

  function kill() {
    if (owner == msg.sender) {
      selfdestruct(owner);
    }
  }

}