pragma solidity ^0.4.18;

// ----------------------------------------------------------------------------
// Safe maths
// ----------------------------------------------------------------------------
contract SafeMath {
    function safeAdd(uint256 a, uint256 b) public pure returns (uint256 c) {
        c = a + b;
        require(c >= a);
    }
    function safeSub(uint256 a, uint256 b) public pure returns (uint256 c) {
        require(b <= a);
        c = a - b;
    }
    function safeMul(uint256 a, uint256 b) public pure returns (uint256 c) {
        c = a * b;
        require(a == 0 || c / a == b);
    }
    function safeDiv(uint256 a, uint256 b) public pure returns (uint256 c) {
        require(b > 0);
        c = a / b;
    }
}


// ----------------------------------------------------------------------------
// ERC Token Standard #20 Interface
// https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20-token-standard.md
// ----------------------------------------------------------------------------
contract ERC20Interface {
    function totalSupply() public constant returns (uint256);
    function balanceOf(address tokenOwner) public constant returns (uint256 balance);
    function allowance(address tokenOwner, address spender) public constant returns (uint256 remaining);
    function transfer(address to, uint256 tokens) public returns (bool success);
    function approve(address spender, uint256 tokens) public returns (bool success);
    function transferFrom(address from, address to, uint256 tokens) public returns (bool success);

    event Transfer(address indexed from, address indexed to, uint256 tokens);
    event Approval(address indexed tokenOwner, address indexed spender, uint256 tokens);
    /* 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);
}


// ----------------------------------------------------------------------------
// Contract function to receive approval and execute function in one call
//
// Borrowed from MiniMeToken
// ----------------------------------------------------------------------------
contract ApproveAndCallFallBack {
    function receiveApproval(address from, uint256 tokens, address token, bytes data) public;
}


// ----------------------------------------------------------------------------
// Owned contract
// ----------------------------------------------------------------------------
contract Owned {
    address public owner;
    //address public newOwner;

    //event OwnershipTransferred(address indexed _from, address indexed _to);
    //event OwnershipTransferInitiated(address indexed _to);

    function Owned() public {
        owner = msg.sender;
    }

    modifier onlyOwner {
        require(msg.sender == owner);
        _;
    }
    
/*
    function transferOwnership(address _newOwner) public onlyOwner {
        newOwner = _newOwner;
        OwnershipTransferInitiated(_newOwner);
    }
    function acceptOwnership() public {
        require(msg.sender == newOwner);
        owner = newOwner;
        OwnershipTransferred(owner, newOwner);
        newOwner = address(0);
    }
    function resetOwner() public onlyOwner{
        newOwner = address(0);
    }
    */
}


// ----------------------------------------------------------------------------
// ERC20 Token, with the addition of symbol, name and decimals and assisted
// token transfers
// ----------------------------------------------------------------------------
contract SatoExchange is ERC20Interface, Owned, SafeMath {
    string public symbol;
    string public  name;
    uint8 public decimals;
    uint256 public _totalSupply;

    mapping(address => uint256) internal balances;
	mapping (address => uint256) internal freezeOf;
    mapping(address => mapping(address => uint256)) internal allowed;


    // ------------------------------------------------------------------------
    // Constructor
    // ------------------------------------------------------------------------
    function SatoExchange() public {
        symbol = 'SATX';
        name = 'SatoExchange';
        decimals = 8;
        _totalSupply = 30000000000000000;
        balances[msg.sender] = _totalSupply;
        Transfer(address(0), msg.sender, _totalSupply);
    }


    // ------------------------------------------------------------------------
    // Total supply
    // ------------------------------------------------------------------------
    function totalSupply() public constant returns (uint256) {
        return _totalSupply  - balances[address(0)];
    }


    // ------------------------------------------------------------------------
    // Get the token balance for account tokenOwner
    // ------------------------------------------------------------------------
    function balanceOf(address tokenOwner) public constant returns (uint256 balance) {
        return balances[tokenOwner];
    }


    // ------------------------------------------------------------------------
    // Transfer the balance from token owner's account to to account
    // - Owner's account must have sufficient balance to transfer
    // - 0 value transfers are allowed
    // ------------------------------------------------------------------------
    function transfer(address to, uint256 tokens) public returns (bool success) {
        if (to == 0x0) revert();                               // Prevent transfer to 0x0 address. Use burn() instead
		if (tokens <= 0) revert(); 
		require(msg.sender != address(0) && msg.sender != to);
	    require(to != address(0));
        if (balances[msg.sender] < tokens) revert();           // Check if the sender has enough
        if (balances[to] + tokens < balances[to]) revert(); // Check for overflows
        balances[msg.sender] = safeSub(balances[msg.sender], tokens);
        balances[to] = safeAdd(balances[to], tokens);
        Transfer(msg.sender, to, tokens);
        return true;
    }


    // ------------------------------------------------------------------------
    // Token owner can approve for spender to transferFrom(...) tokens
    // from the token owner's account
    //
    // https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20-token-standard.md
    // recommends that there are no checks for the approval double-spend attack
    // as this should be implemented in user interfaces 
    // ------------------------------------------------------------------------
    function approve(address spender, uint256 tokens) public returns (bool success) {
        require(tokens > 0); 
        allowed[msg.sender][spender] = tokens;
        Approval(msg.sender, spender, tokens);
        return true;
    }


    function burn(uint256 _value) public returns (bool success) {
        if (balances[msg.sender] < _value) revert();            // Check if the sender has enough
		if (_value <= 0) revert(); 
        balances[msg.sender] = SafeMath.safeSub(balances[msg.sender], _value);                      // Subtract from the sender
        _totalSupply = SafeMath.safeSub(_totalSupply,_value);                                // Updates totalSupply
        Burn(msg.sender, _value);
        return true;
    }
	
	function freeze(uint256 _value) public returns (bool success) {
        if (balances[msg.sender] < _value) revert();            // Check if the sender has enough
		if (_value <= 0) revert(); 
        balances[msg.sender] = SafeMath.safeSub(balances[msg.sender], _value);                      // Subtract from the sender
        freezeOf[msg.sender] = SafeMath.safeAdd(freezeOf[msg.sender], _value);                                // Updates totalSupply
        Freeze(msg.sender, _value);
        return true;
    }
	
	function unfreeze(uint256 _value) public returns (bool success) {
        if (freezeOf[msg.sender] < _value) revert();            // Check if the sender has enough
		if (_value <= 0) revert(); 
        freezeOf[msg.sender] = SafeMath.safeSub(freezeOf[msg.sender], _value);                      // Subtract from the sender
		balances[msg.sender] = SafeMath.safeAdd(balances[msg.sender], _value);
        Unfreeze(msg.sender, _value);
        return true;
    }
	

    // ------------------------------------------------------------------------
    // Transfer tokens from the from account to the to account
    // 
    // The calling account must already have sufficient tokens approve(...)-d
    // for spending from the from account and
    // - From account must have sufficient balance to transfer
    // - Spender must have sufficient allowance to transfer
    // - 0 value transfers are allowed
    // ------------------------------------------------------------------------
    function transferFrom(address from, address to, uint256 tokens) public returns (bool success) {
        if (to == 0x0) revert();                                // Prevent transfer to 0x0 address. Use burn() instead
		if (tokens <= 0) revert(); 
        if (balances[from] < tokens) revert();                 // Check if the sender has enough
        if (balances[to] + tokens < balances[to]) revert();  // Check for overflows
        if (tokens > allowed[from][msg.sender]) revert();     // Check allowance
        balances[from] = safeSub(balances[from], tokens);
        allowed[from][msg.sender] = safeSub(allowed[from][msg.sender], tokens);
        balances[to] = safeAdd(balances[to], tokens);
        Transfer(from, to, tokens);
        return true;
    }


    // ------------------------------------------------------------------------
    // Returns the amount of tokens approved by the owner that can be
    // transferred to the spender's account
    // ------------------------------------------------------------------------
    function allowance(address tokenOwner, address spender) public constant returns (uint256 remaining) {
        return allowed[tokenOwner][spender];
    }


    // ------------------------------------------------------------------------
    // Token owner can approve for spender to transferFrom(...) tokens
    // from the token owner's account. The spender contract function
    // receiveApproval(...) is then executed
    // ------------------------------------------------------------------------
    function approveAndCall(address spender, uint256 tokens, bytes data) public returns (bool success) {
        require(tokens > 0);
        allowed[msg.sender][spender] = tokens;
        Approval(msg.sender, spender, tokens);
        ApproveAndCallFallBack(spender).receiveApproval(msg.sender, tokens, this, data);
        return true;
    }


	// can accept ether
	function() public payable {
	    revert(); //disable receive ether
    }

	// transfer balance to owner
	/*
	function withdrawEther(uint256 amount)  public onlyOwner returns (bool success){
		owner.transfer(amount);
		return true;
	}*/

    // ------------------------------------------------------------------------
    // Owner can transfer out any accidentally sent ERC20 tokens
    // ------------------------------------------------------------------------
    function transferAnyERC20Token(address tokenAddress, uint256 tokens) public onlyOwner returns (bool success) {
        return ERC20Interface(tokenAddress).transfer(owner, tokens);
    }
}