pragma solidity ^0.4.0;

contract owned {
    address public owner;

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

    modifier onlyOwner {
        require(msg.sender == owner);
        _;
    }

    function transferableOwnership(address newOwner) onlyOwner public {
        owner = newOwner;
    }
}

interface tokenRecepient {
    function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData) external;
}

contract TokenERC20 {
    // Public variables of Token

    string public name;
    string public symbol;
    uint8 public decimal = 18; // 18 decimal values is strongly suggested. 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 events on blockchain that will notify clients
    event Transfer(address indexed from, address indexed to , uint256 value);

    // This generates a public events on blockchain that will notify clients
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);

    // This notified client ablout the amount burns
    event Burn(address indexed From, uint256 value);

    // /**
    //     * constructor function
    //     *
    //     * Initializes contract with initial supply tokens with creator of contract
    //  */

    constructor(uint256 initialSupply, string tokenName, string tokenSymbol) public {
        totalSupply = initialSupply * 10 ** uint256(decimal); // update total supply with decimal amount
        balanceof[msg.sender] = totalSupply; // Give the creator all initial token
        name = tokenName; // the name for display purpose
        symbol = tokenSymbol; // the symbol for display purpose
    }

    /**
     * Internal transfer, only can be handled 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 overflow
         require(balanceof[_to] + _value > balanceof[_to]);

         // Save this for assestion in 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);

         // Assert are used to use static analysis to find bugs in your code. They should never fail.
         assert(balanceof[_to] + balanceof[_from] == previousBalances);

     }

     /**
      * Token Transfer
      *
      * Send '_value' tokens to '_to' in behalf of '_from'
      *
      * @param _to The address of the receiver
      * @param _value the amount to send
      *
      */

      function transfer(address _to, uint256 _value) public returns (bool success) {
          _transfer(msg.sender, _to, _value);
          return true;
      }

      /**
      * Token Transfer from other Address
      *
      * Send '_value' tokens to '_to' in behalf of '_from'
      *
      * @param _from The address of the sender
      * @param _to The address of the receiver
      * @param _value the amount to send
      *
      */

      function transferFrom(address _to, address _from ,uint256 _value) public returns (bool success) {
          require(_value <= allowance[_from][msg.sender]); // check allowance
          _transfer(_from, _to, _value);
          return true;
      }

      /**
      * Set allowance for other address
      *
      * Allows `_spender` to spend no more than `_value` tokens in 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;
          emit Approval(msg.sender, _spender, _value);
          return true;
      }


      /**
      * Set allowance for other address and notify
      *
      * Allows `_spender` to spend no more than `_value` tokens in 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) {
          tokenRecepient spender = tokenRecepient(_spender);
          if(approve(_spender, _value)) {
              spender.receiveApproval(msg.sender, _value, this, _extraData);
              return true;
          }
      }

      /**
       *
       * Remove '_value' token from the system irreversibly
       *
       * @param _value the amount to burn
       *
       */

       function burn(uint256 _value) public returns (bool success) {
           require(balanceof[msg.sender] >= _value); // Check if sender has enough
           balanceof[msg.sender] -= _value; // Subtract from the sender
           totalSupply -= _value; // Updates total supply
           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 targeted balance is enough
          require(_value <= allowance[_from][msg.sender]); // Check allowance
          balanceof[_from] -= _value; // Subtract from the targeted balanceof
          allowance[_from][msg.sender] -= _value; // Subtract from the sender's allowance
          totalSupply -= _value; // Update totalSupply
          emit Burn(_from, _value);
          return true;
       }

        // 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;
        // }


}

        contract Sikka is owned, TokenERC20 {
          uint256 public sellPrice;
          uint256 public buyPrice;

          mapping(address => bool) public frozenAccount;

          /* This generates a public event in blockchain that will notify clients */

          event FrozenFunds(address target, bool frozen);

          /* Initialize contract with initial supply tokens to the creator of the contract */

          constructor(
              uint256 initialSupply,
              string tokenName,
              string tokenSymbol
            ) TokenERC20(initialSupply, tokenName, tokenSymbol) public {}

            /* 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 (balanceof[_from] >= _value);               // Check if the sender has enough
            require (balanceof[_to] + _value >= balanceof[_to]); // Check for overflows
            require(!frozenAccount[_from]);                     // Check if sender is frozen
            require(!frozenAccount[_to]);                       // Check if recipient is frozen
            balanceof[_from] -= _value;                         // Subtract from the sender
            balanceof[_to] += _value;                           // Add the same to the recipient
            emit Transfer(_from, _to, _value);
        }

        /// @notice Create `mintedAmount` tokens and send it to `target`
    /// @param target Address to receive the tokens
    /// @param mintedAmount the amount of tokens it will receive
    function mintToken(address target, uint256 mintedAmount) onlyOwner public {
        balanceof[target] += mintedAmount;
        totalSupply += mintedAmount;
        emit Transfer(0, this, mintedAmount);
        emit Transfer(this, target, mintedAmount);
    }

/// @notice `freeze? Prevent | Allow` `target` from sending & receiving tokens
    /// @param target Address to be frozen
    /// @param freeze either to freeze it or not
    function freezeAccount(address target, bool freeze) onlyOwner public {
        frozenAccount[target] = freeze;
        emit FrozenFunds(target, freeze);
    }


/// @notice Allow users to buy tokens for `newBuyPrice` eth and sell tokens for `newSellPrice` eth
    /// @param newSellPrice Price the users can sell to the contract
    /// @param newBuyPrice Price users can buy from the contract
    function setPrices(uint256 newSellPrice, uint256 newBuyPrice) onlyOwner public {
        sellPrice = newSellPrice;
        buyPrice = newBuyPrice;
    }
/// @notice Buy tokens from contract by sending ether
    function buy() payable public {
        uint amount = msg.value / buyPrice;               // calculates the amount
        _transfer(this, msg.sender, amount);              // makes the transfers
    }
/// @notice Sell `amount` tokens to contract
    /// @param amount amount of tokens to be sold
    function sell(uint256 amount) public {
        address myAddress = this;
        require(myAddress.balance >= amount * sellPrice);      // checks if the contract has enough ether to buy
        _transfer(msg.sender, this, amount);              // makes the transfers
        msg.sender.transfer(amount * sellPrice);          // sends ether to the seller. It's important to do this last to avoid recursion attacks
    }
}