// solium-disable linebreak-style
pragma solidity ^0.4.24;

/**
 * Math operations with safety checks
 */
contract SafeMath 
{
    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;
    }
}
contract EdraSave is SafeMath
{
    string public name;
    string public symbol;
    uint8 public decimals;
    uint256 public totalSupply;
    address public owner;

    /* This creates an array with all balances */
    mapping (address => uint256) public balanceOf;
    mapping (address => uint256) public freezeOf;
    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);

    /* 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);

    /* Initializes contract with initial supply tokens to the creator of the contract */
    constructor( uint256 initialSupply, string tokenName, uint8 decimalUnits, string tokenSymbol ) public 
    {
        balanceOf[msg.sender] = initialSupply;              // Give the creator all initial tokens
        totalSupply = initialSupply;                        // Update total supply
        name = tokenName;                                   // Set the name for display purposes
        symbol = tokenSymbol;                               // Set the symbol for display purposes
        decimals = decimalUnits;                            // Amount of decimals for display purposes
        owner = msg.sender;
    }

    /* Send coins */
    function transfer(address _to, uint256 _value) public 
    {
        require(_to != 0x0, "Receiver must be specified "); 
        require(_value > 0, "Amount must greater than zero");
        require(balanceOf[msg.sender] >= _value, "Sender's balance less than amount");
        require(balanceOf[_to] + _value >= balanceOf[_to], "Overflow!");

        balanceOf[msg.sender] = SafeMath.safeSub(balanceOf[msg.sender], _value);                     // Subtract from the sender
        balanceOf[_to] = SafeMath.safeAdd(balanceOf[_to], _value);                            // Add the same to the recipient
        emit Transfer(msg.sender, _to, _value);                   // Notify anyone listening that this transfer took place
    }

    /* Allow another contract to spend some tokens in your behalf */
    function approve(address _spender, uint256 _value) public returns (bool success) 
    {
        require(_value > 0, "Amount must greater than zero");
        allowance[msg.sender][_spender] = _value;
        return true;
    }

    /* A contract attempts to get the coins */
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) 
    {
        require(_to != 0x0, "Receiver must be specified "); 
        require(_value > 0, "Amount must greater than zero");
        require(balanceOf[msg.sender] >= _value, "Sender's balance less than amount");
        require(balanceOf[_to] + _value >= balanceOf[_to], "Overflow!");
        require(_value <= allowance[_from][msg.sender], "Check allowance!");
        balanceOf[_from] = SafeMath.safeSub(balanceOf[_from], _value);                           // Subtract from the sender
        balanceOf[_to] = SafeMath.safeAdd(balanceOf[_to], _value);                             // Add the same to the recipient
        allowance[_from][msg.sender] = SafeMath.safeSub(allowance[_from][msg.sender], _value);
        emit Transfer(_from, _to, _value);
        return true;
    }

    function burn(uint256 _value) public returns (bool success) 
    {
        require(balanceOf[msg.sender] >= _value, "Balance is not enough");
        require(_value > 0, "Amount must greater than zero");
        balanceOf[msg.sender] = SafeMath.safeSub(balanceOf[msg.sender], _value);           // Subtract from the sender
        totalSupply = SafeMath.safeSub(totalSupply,_value);                                // Updates totalSupply
        emit Burn(msg.sender, _value);
        return true;
    }

    function freeze(uint256 _value) public returns (bool success) 
    {
        require(balanceOf[msg.sender] >= _value, "Balance is not enough");
        require(_value > 0, "Amount must greater than zero");
        balanceOf[msg.sender] = SafeMath.safeSub(balanceOf[msg.sender], _value);                      // Subtract from the sender
        freezeOf[msg.sender] = SafeMath.safeAdd(freezeOf[msg.sender], _value);                                // Updates totalSupply
        emit Freeze(msg.sender, _value);
        return true;
    }

    function unfreeze(uint256 _value) public returns (bool success) 
    {
        require(balanceOf[msg.sender] >= _value, "Balance is not enough");
        require(_value > 0, "Amount must greater than zero");
        freezeOf[msg.sender] = SafeMath.safeSub(freezeOf[msg.sender], _value);                      // Subtract from the sender
        balanceOf[msg.sender] = SafeMath.safeAdd(balanceOf[msg.sender], _value);
        emit Unfreeze(msg.sender, _value);
        return true;
    }

	// transfer balance to owner
    function withdrawEther(uint256 amount) public
    {
        require(msg.sender == owner, "Just owner can withdraw");
        owner.transfer(amount);
    }

	// can accept ether
    // function() payable {}
}