pragma solidity ^0.5.9;

contract owned {
    address public owner;

    constructor () public {
        owner = msg.sender;
    }

    modifier onlyOwner {
        require(msg.sender == owner);
        _;
    }

    function transferOwnerShip(address newOwer) public onlyOwner {
        owner = newOwer;
    }
}

interface tokenRecipient {
	function receiveApproval(address _from, uint256 _value, address _token, bytes calldata _extraData) external;
}

contract TokenERC20 {
    string public name;
    string public symbol;
    uint8 public decimals = 18;
	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);
    event Approval(address indexed _owner, address indexed _spender, 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
     */
    constructor (uint256 _initialSupply, string memory _tokenName, string memory _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
    }
	
    /*
     * 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 != address(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;
		emit Approval(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 memory _extraData)
        public
        returns (bool success) {
        tokenRecipient spender = tokenRecipient(_spender);
        if (approve(_spender, _value)) {
            spender.receiveApproval(msg.sender, _value, address(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;
    }
}

/******************************************/
/*       ADVANCED TOKEN STARTS HERE       */
/******************************************/

contract MyAdvancedToken is owned, TokenERC20 {
    uint256 public sellPrice;
    uint256 public buyPrice;
	
	// Whether to freeze the list of accounts
    mapping (address => bool) public frozenAccount;

	// This generates a public event on the blockchain that will notify clients
    event FrozenFunds(address target, bool frozen);
	
    /*
     * Initializes contract with initial supply tokens to the creator of the contract
     * @param initialSupply
     * @param tokenName
     * @param tokenSymbol
     */
	constructor (uint256 initialSupply, string memory tokenName, string memory tokenSymbol) TokenERC20(initialSupply, tokenName, tokenSymbol) payable public {}

   	/*
     * Internal transfer, only can be called by this contract
     */
    function _transfer(address _from, address _to, uint _value) internal {
        require (_to != address(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(address(0), address(this), mintedAmount);
        emit Transfer(address(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(address(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 {
        require(address(this).balance >= amount * sellPrice);  // checks if the contract has enough ether to buy
        _transfer(msg.sender, address(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
    }
}