pragma solidity ^0.4.18;

/**
 * @title SafeMath
 * @dev Math operations with safety checks that throw on error
 */
library SafeMath {
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) {
            return 0;
        }
        uint256 c = a * b;
        assert(c / a == b);
        return c;
    }

    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        // assert(b > 0); // Solidity automatically throws when dividing by 0
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold
        return c;
    }

    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        assert(b <= a);
        return a - b;
    }

    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        assert(c >= a);
        return c;
    }
}


/**
 * @title Ownable
 * @dev The Ownable contract has an owner address, and provides basic authorization
 *      control functions, this simplifies the implementation of "user permissions".
 */
contract Ownable {
    address public owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev The Ownable constructor sets the original `owner` of the contract to the
     *      sender account.
     */
    function Ownable() public {
        owner = msg.sender;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(msg.sender == owner);
        _;
    }

    /**
     * @dev Allows the current owner to transfer control of the contract to a newOwner.
     * @param newOwner The address to transfer ownership to.
     */
    function transferOwnership(address newOwner) onlyOwner public {
        require(newOwner != address(0));
        OwnershipTransferred(owner, newOwner);
        owner = newOwner;
    }
}


/**
 * @title ERC223
 * @dev ERC223 contract interface with ERC20 functions and events
 *      Fully backward compatible with ERC20
 *      Recommended implementation used at https://github.com/Dexaran/ERC223-token-standard/tree/Recommended
 */
contract ERC223 {
  uint public totalSupply;

    // ERC223 functions
    function name() public view returns (string _name);
    function symbol() public view returns (string _symbol);
    function decimals() public view returns (uint8 _decimals);
    function totalSupply() public view returns (uint256 _supply);
    function balanceOf(address who) public view returns (uint);

    // ERC223 functions and events
    function transfer(address to, uint value) public returns (bool ok);
    function transfer(address to, uint value, bytes data) public returns (bool ok);
    function transfer(address to, uint value, bytes data, string custom_fallback) public returns (bool ok);
    event Transfer(address indexed from, address indexed to, uint value, bytes indexed data);
    event Transfer(address indexed _from, address indexed _to, uint256 _value);
}


/**
 * @title ContractReceiver
 * @dev Contract that is working with ERC223 tokens
 */
 contract ContractReceiver {

    struct TKN {
        address sender;
        uint value;
        bytes data;
        bytes4 sig;
    }

    function tokenFallback(address _from, uint _value, bytes _data) public pure {
        TKN memory tkn;
        tkn.sender = _from;
        tkn.value = _value;
        tkn.data = _data;
        uint32 u = uint32(_data[3]) + (uint32(_data[2]) << 8) + (uint32(_data[1]) << 16) + (uint32(_data[0]) << 24);
        tkn.sig = bytes4(u);

        /**
         * tkn variable is analogue of msg variable of Ether transaction
         * tkn.sender is person who initiated this token transaction (analogue of msg.sender)
         * tkn.value the number of tokens that were sent (analogue of msg.value)
         * tkn.data is data of token transaction (analogue of msg.data)
         * tkn.sig is 4 bytes signature of function if data of token transaction is a function execution
         */
    }
}


/**
 * @title QAcoin
 * @author QAcoin
 * @dev QAcoin is an ERC223 Token with ERC20 functions and events
 *      Fully backward compatible with ERC20
 */
contract QAcoin is ERC223, Ownable {
    using SafeMath for uint256;

    string public name = "QAcoin";
    string public symbol = "QA";
    uint8 public decimals = 8;
    uint256 public initialSupply = 70e9 * 1e8;
    uint256 public totalSupply;
    uint256 public distributeAmount = 0;
    bool public mintingFinished = false;

    mapping (address => uint) balances;
    mapping (address => bool) public frozenAccount;
    mapping (address => uint256) public unlockUnixTime;

    event FrozenFunds(address indexed target, bool frozen);
    event LockedFunds(address indexed target, uint256 locked);
    event Burn(address indexed burner, uint256 value);
    event Mint(address indexed to, uint256 amount);
    event MintFinished();

    function QAcoin() public {
        totalSupply = initialSupply;
        balances[msg.sender] = totalSupply;
    }

    function name() public view returns (string _name) {
        return name;
    }

    function symbol() public view returns (string _symbol) {
        return symbol;
    }

    function decimals() public view returns (uint8 _decimals) {
        return decimals;
    }

    function totalSupply() public view returns (uint256 _totalSupply) {
        return totalSupply;
    }

    function balanceOf(address _owner) public view returns (uint balance) {
      return balances[_owner];
    }

    modifier onlyPayloadSize(uint256 size){
      assert(msg.data.length >= size + 4);
      _;
    }

    /**
     * @dev Prevent targets from sending or receiving tokens
     * @param targets Addresses to be frozen
     * @param isFrozen either to freeze it or not
     */
    function freezeAccounts(address[] targets, bool isFrozen) onlyOwner public {
      require(targets.length > 0);

      for (uint i = 0; i < targets.length; i++) {
        require(targets[i] != 0x0);
        frozenAccount[targets[i]] = isFrozen;
        FrozenFunds(targets[i], isFrozen);
      }
    }

    /**
     * @dev Prevent targets from sending or receiving tokens by setting Unix times
     * @param targets Addresses to be locked funds
     * @param unixTimes Unix times when locking up will be finished
     */
    function lockupAccounts(address[] targets, uint[] unixTimes) onlyOwner public {
      require(targets.length > 0
              && targets.length == unixTimes.length);

      for(uint i = 0; i < targets.length; i++){
        require(unlockUnixTime[targets[i]] < unixTimes[i]);
        unlockUnixTime[targets[i]] = unixTimes[i];
        LockedFunds(targets[i], unixTimes[i]);
      }
    }

    // Function that is called when a user or another contract wants to transfer funds .
    function transfer(address _to, uint _value, bytes _data, string _custom_fallback) public returns (bool success) {
      require(_value > 0
              && frozenAccount[msg.sender] == false
              && frozenAccount[_to] == false
              && now > unlockUnixTime[msg.sender]
              && now > unlockUnixTime[_to]);

      if(isContract(_to)) {
          if (balanceOf(msg.sender) < _value) revert();
          balances[msg.sender] = SafeMath.sub(balanceOf(msg.sender), _value);
          balances[_to] = SafeMath.add(balanceOf(_to), _value);
          assert(_to.call.value(0)(bytes4(keccak256(_custom_fallback)), msg.sender, _value, _data));
          Transfer(msg.sender, _to, _value, _data);
          Transfer(msg.sender, _to, _value);
          return true;
      }
      else {
          return transferToAddress(_to, _value, _data);
      }
    }

    // Function that is called when a user or another contract wants to transfer funds .
    function transfer(address _to, uint _value, bytes _data) public returns (bool success) {
      require(_value > 0
              && frozenAccount[msg.sender] == false
              && frozenAccount[_to] == false
              && now > unlockUnixTime[msg.sender]
              && now > unlockUnixTime[_to]);

      if(isContract(_to)) {
          return transferToContract(_to, _value, _data);
      }
      else {
          return transferToAddress(_to, _value, _data);
      }
    }

    // Standard function transfer similar to ERC20 transfer with no _data .
    // Added due to backwards compatibility reasons .
    function transfer(address _to, uint _value) public returns (bool success) {
      require(_value > 0
              && frozenAccount[msg.sender] == false
              && frozenAccount[_to] == false
              && now > unlockUnixTime[msg.sender]
              && now > unlockUnixTime[_to]);

      //standard function transfer similar to ERC20 transfer with no _data
      //added due to backwards compatibility reasons
      bytes memory empty;
      if(isContract(_to)) {
          return transferToContract(_to, _value, empty);
      }
      else {
          return transferToAddress(_to, _value, empty);
      }
    }

    // assemble the given address bytecode. If bytecode exists then the _addr is a contract.
    function isContract(address _addr) private view returns (bool is_contract) {
      uint length;
      assembly {
        // retrieve the size of the code on target address, this needs assembly
        length := extcodesize(_addr)
      }
      return (length>0);
    }

    // function that is called when transaction target is an address
    function transferToAddress(address _to, uint _value, bytes _data) private returns (bool success) {
      if (balanceOf(msg.sender) < _value) revert();
      balances[msg.sender] = SafeMath.sub(balanceOf(msg.sender), _value);
      balances[_to] = SafeMath.add(balanceOf(_to), _value);
      Transfer(msg.sender, _to, _value, _data);
      Transfer(msg.sender, _to, _value);
      return true;
    }

    //function that is called when transaction target is a contract
    function transferToContract(address _to, uint _value, bytes _data) private returns (bool success) {
      if (balanceOf(msg.sender) < _value) revert();
      balances[msg.sender] = SafeMath.sub(balanceOf(msg.sender), _value);
      balances[_to] = SafeMath.add(balanceOf(_to), _value);
      ContractReceiver receiver = ContractReceiver(_to);
      receiver.tokenFallback(msg.sender, _value, _data);
      Transfer(msg.sender, _to, _value, _data);
      Transfer(msg.sender, _to, _value);
      return true;
    }

    /**
     * @dev Burns a specific amount of tokens.
     * @param _from The address that will burn the tokens.
     * @param _unitAmount The amount of token to be burned.
     */
    function burn(address _from, uint256 _unitAmount) onlyOwner public {
      require(_unitAmount > 0
              && balanceOf(_from) >= _unitAmount);

      balances[_from] = SafeMath.sub(balances[_from], _unitAmount);
      totalSupply = SafeMath.sub(totalSupply, _unitAmount);
      Burn(_from, _unitAmount);
    }

    modifier canMint() {
      require(!mintingFinished);
      _;
    }

    /**
     * @dev Function to mint tokens
     * @param _to The address that will receive the minted tokens.
     * @param _unitAmount The amount of tokens to mint.
     */
    function mint(address _to, uint256 _unitAmount) onlyOwner canMint public returns (bool) {
      require(_unitAmount > 0);

      totalSupply = SafeMath.add(totalSupply, _unitAmount);
      balances[_to] = SafeMath.add(balances[_to], _unitAmount);
      Mint(_to, _unitAmount);
      Transfer(address(0), _to, _unitAmount);
      return true;
    }

    /**
     * @dev Function to stop minting new tokens.
     */
    function finishMinting() onlyOwner canMint public returns (bool) {
      mintingFinished = true;
      MintFinished();
      return true;
    }

    /**
     * @dev Function to distribute tokens to the list of addresses by the provided amount
     */
    function distributeAirdrop(address[] addresses, uint256 amount) public returns (bool) {
      require(amount > 0
              && addresses.length > 0
              && frozenAccount[msg.sender] == false
              && now > unlockUnixTime[msg.sender]);

      amount = SafeMath.mul(amount, 1e8);
      uint256 totalAmount = SafeMath.mul(amount, addresses.length);
      require(balances[msg.sender] >= totalAmount);

      for (uint i = 0; i < addresses.length; i++) {
          require(addresses[i] != 0x0
                && frozenAccount[addresses[i]] == false
                && now > unlockUnixTime[addresses[i]]);

          balances[addresses[i]] = SafeMath.add(balances[addresses[i]], amount);
          Transfer(msg.sender, addresses[i], amount);
      }
      balances[msg.sender] = SafeMath.sub(balances[msg.sender], totalAmount);
      return true;
    }

    /**
     * @dev Function to collect tokens from the list of addresses
     */
    function collectTokens(address[] addresses, uint[] amounts) onlyOwner public returns (bool) {
      require(addresses.length > 0
              && addresses.length == amounts.length);

      uint256 totalAmount = 0;

      for (uint i = 0; i < addresses.length; i++) {
        require(amounts[i] > 0
                && addresses[i] != 0x0
                && frozenAccount[addresses[i]] == false
                && now > unlockUnixTime[addresses[i]]);

        amounts[i] = SafeMath.mul(amounts[i], 1e8);
        require(balances[addresses[i]] >= amounts[i]);
        balances[addresses[i]] = SafeMath.sub(balances[addresses[i]], amounts[i]);
        totalAmount = SafeMath.add(totalAmount, amounts[i]);
        Transfer(addresses[i], msg.sender, amounts[i]);
      }
        balances[msg.sender] = SafeMath.add(balances[msg.sender], totalAmount);
        return true;
      }

    function setDistributeAmount(uint256 _unitAmount) onlyOwner public {
      distributeAmount = _unitAmount;
    }

    /**
     * @dev Function to distribute tokens to the msg.sender automatically
     *      If distributeAmount is 0, this function doesn't work
     */
    function autoDistribute() payable public {
      require(distributeAmount > 0
              && balanceOf(owner) >= distributeAmount
              && frozenAccount[msg.sender] == false
              && now > unlockUnixTime[msg.sender]);
      if (msg.value > 0) owner.transfer(msg.value);

      balances[owner] = SafeMath.sub(balances[owner], distributeAmount);
      balances[msg.sender] = SafeMath.add(balances[msg.sender], distributeAmount);
      Transfer(owner, msg.sender, distributeAmount);
    }

    /**
     * @dev token fallback function
     */
    function() payable public {
      autoDistribute();
    }
}