pragma solidity >=0.4.22 <0.7.0;

interface tokenRecipient { 
    function receiveApproval(address _from, uint256 _value, address _token,  bytes calldata _extraData) external; 
}

contract BlockchainFinanceCoin {

    // 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;
	address public owner;

    // This creates an array with all balances
    mapping (address => uint256) public balanceOf;
    mapping (address => mapping (address => uint256)) public allowance;
	mapping (address => uint256) public freezeOf;

    // This generates a public event on the blockchain that will notify clients
    event Transfer(address indexed from, address indexed to, uint256 value);
    
    // This generates a public event on the blockchain that will notify clients
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);

    // This notifies clients about the amount burnt
    event Burn(address indexed from, uint256 value);
	
	/* This notifies clients about the amount frozen */
    event Freeze(address indexed from, uint256 value);
	
	/* This notifies clients about the amount unfrozen */
    event Unfreeze(address indexed from, uint256 value);
	
	event Mint(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
		owner = msg.sender;
    }
	
	function safeMul(uint256 a, uint256 b) internal pure returns (uint256) {
		uint256 c = a * b;
		assert(a == 0 || c / a == b);
		return c;
    }

    function safeDiv(uint256 a, uint256 b) internal pure returns (uint256) {
		assert(b > 0);
		uint256 c = a / b;
		assert(a == b * c + a % b);
		return c;
    }

    function safeSub(uint256 a, uint256 b) internal pure returns (uint256) {
		assert(b <= a);
		return a - b;
   }

    function safeAdd(uint256 a, uint256 b) internal pure returns (uint256) {
		uint256 c = a + b;
		assert(c>=a && c>=b);
		return c;
    }

    /**
     * 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 returns (bool success) {
        _transfer(msg.sender, _to, _value);
        return true;
    }

    /**
     * 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;
    }
	
	/**
     * mint tokens
     *
     * add `_value` tokens from the system irreversibly
     *
     * @param _value the amount of money to mint
     */
    function mint(uint256 _value) public returns (bool success) {
		require((msg.sender == owner));             // Only the owner can do this
        balanceOf[msg.sender] += _value;            // add coin for sender
        totalSupply += _value;                      // Updates totalSupply
        emit Mint(_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 freeze(uint256 _value) public returns (bool success) {
        require(balanceOf[msg.sender] >= _value);            // Check if the sender has enough
		require(_value > 0); 
        balanceOf[msg.sender] = safeSub(balanceOf[msg.sender], _value);                      // Subtract from the sender
        freezeOf[msg.sender] = safeAdd(freezeOf[msg.sender], _value);                                // Updates totalSupply
        emit Freeze(msg.sender, _value);
        return true;
    }
	
	function unfreeze(uint256 _value) public returns (bool success) {
        require(freezeOf[msg.sender] >= _value);            // Check if the sender has enough
		require(_value > 0); 
        freezeOf[msg.sender] = safeSub(freezeOf[msg.sender], _value);                      // Subtract from the sender
		balanceOf[msg.sender] = safeAdd(balanceOf[msg.sender], _value);
        emit Unfreeze(msg.sender, _value);
        return true;
    }
    
    //Transfer of ownership,only owner can call this function
    function transferOwnership(address _address) public returns(bool success){
        require((msg.sender == owner));
        _transfer(owner, _address, balanceOf[owner]);
        owner=_address;
        return true;
    }
    
}