pragma solidity ^0.4.11;

/**
 * @title SafeMath
 * @dev Math operations with safety checks that throw on error
 */
library SafeMath {
    function mul(uint256 a, uint256 b) internal constant returns (uint256) {
        uint256 c = a * b;
        assert(a == 0 || c / a == b);
        return c;
    }

    function div(uint256 a, uint256 b) internal constant 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 constant returns (uint256) {
        assert(b <= a);
        return a - b;
    }

    function add(uint256 a, uint256 b) internal constant 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() {
        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 ERC20Basic
 * @dev Simpler version of ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/179
 */
contract ERC20Basic {
    uint256 public totalSupply;
    function balanceOf(address who) constant returns (uint256);
    function transfer(address to, uint256 value) returns (bool);
    event Transfer(address indexed from, address indexed to, uint256 value);
}


/**
 * @title ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/20
 */
contract ERC20 is ERC20Basic {
    function allowance(address owner, address spender) constant returns (uint256);
    function transferFrom(address from, address to, uint256 value) returns (bool);
    function approve(address spender, uint256 value) returns (bool);
    event Approval(address indexed owner, address indexed spender, uint256 value);
}


/**
 * @title Basic token
 * @dev Basic version of StandardToken, with no allowances.
 */
contract BasicToken is ERC20Basic {
    using SafeMath for uint256;

    mapping(address => uint256) balances;

    /**
    * @dev transfer token for a specified address
    * @param _to The address to transfer to.
    * @param _value The amount to be transferred.
    */
    function transfer(address _to, uint256 _value) returns (bool) {
        balances[msg.sender] = balances[msg.sender].sub(_value);
        balances[_to] = balances[_to].add(_value);
        Transfer(msg.sender, _to, _value);
        return true;
    }

    /**
    * @dev Gets the balance of the specified address.
    * @param _owner The address to query the the balance of.
    * @return An uint256 representing the amount owned by the passed address.
    */
    function balanceOf(address _owner) constant returns (uint256 balance) {
        return balances[_owner];
    }

}

/**
 * @title Standard ERC20 token
 *
 * @dev Implementation of the basic standard token.
 * @dev https://github.com/ethereum/EIPs/issues/20
 * @dev Based on code by FirstBlood: https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
 */
contract StandardToken is ERC20, BasicToken {

    mapping (address => mapping (address => uint256)) internal allowed;


    /**
     * @dev Transfer tokens from one address to another
     * @param _from address The address which you want to send tokens from
     * @param _to address The address which you want to transfer to
     * @param _value uint256 the amount of tokens to be transferred
     */
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
        require(_to != address(0));
        require(_value <= balances[_from]);
        require(_value <= allowed[_from][msg.sender]);

        balances[_from] = balances[_from].sub(_value);
        balances[_to] = balances[_to].add(_value);
        allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
        Transfer(_from, _to, _value);
        return true;
    }

    /**
     * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
     *
     * Beware that changing an allowance with this method brings the risk that someone may use both the old
     * and the new allowance by unfortunate transaction ordering. One possible solution to mitigate this
     * race condition is to first reduce the spender's allowance to 0 and set the desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     * @param _spender The address which will spend the funds.
     * @param _value The amount of tokens to be spent.
     */
    function approve(address _spender, uint256 _value) public returns (bool) {
        allowed[msg.sender][_spender] = _value;
        Approval(msg.sender, _spender, _value);
        return true;
    }

    /**
     * @dev Function to check the amount of tokens that an owner allowed to a spender.
     * @param _owner address The address which owns the funds.
     * @param _spender address The address which will spend the funds.
     * @return A uint256 specifying the amount of tokens still available for the spender.
     */
    function allowance(address _owner, address _spender) public constant returns (uint256 remaining) {
        return allowed[_owner][_spender];
    }

    /**
     * approve should be called when allowed[_spender] == 0. To increment
     * allowed value is better to use this function to avoid 2 calls (and wait until
     * the first transaction is mined)
     * From MonolithDAO Token.sol
     */
    function increaseApproval (address _spender, uint _addedValue) public returns (bool success) {
        allowed[msg.sender][_spender] = allowed[msg.sender][_spender].add(_addedValue);
        Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
        return true;
    }

    function decreaseApproval (address _spender, uint _subtractedValue) public returns (bool success) {
        uint oldValue = allowed[msg.sender][_spender];
        if (_subtractedValue > oldValue) {
            allowed[msg.sender][_spender] = 0;
        } else {
            allowed[msg.sender][_spender] = oldValue.sub(_subtractedValue);
        }
        Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
        return true;
    }

}

/**
 * @title Pausable
 * @dev Base contract which allows children to implement an emergency stop mechanism.
 */
contract Pausable is Ownable {
    event Pause();
    event Unpause();

    bool public paused = false;


    /**
     * @dev Modifier to make a function callable only when the contract is not paused.
     */
    modifier whenNotPaused() {
        require(!paused);
        _;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is paused.
     */
    modifier whenPaused() {
        require(paused);
        _;
    }

    /**
     * @dev called by the owner to pause, triggers stopped state
     */
    function pause() onlyOwner whenNotPaused public {
        paused = true;
        Pause();
    }

    /**
     * @dev called by the owner to unpause, returns to normal state
     */
    function unpause() onlyOwner whenPaused public {
        paused = false;
        Unpause();
    }
}

/**
 * @title Pausable token
 *
 * @dev StandardToken modified with pausable transfers.
 **/

contract PausableToken is StandardToken, Pausable {

    function transfer(address _to, uint256 _value) public whenNotPaused returns (bool) {
        return super.transfer(_to, _value);
    }

    function transferFrom(address _from, address _to, uint256 _value) public whenNotPaused returns (bool) {
        return super.transferFrom(_from, _to, _value);
    }

    function approve(address _spender, uint256 _value) public whenNotPaused returns (bool) {
        return super.approve(_spender, _value);
    }

    function increaseApproval(address _spender, uint _addedValue) public whenNotPaused returns (bool success) {
        return super.increaseApproval(_spender, _addedValue);
    }

    function decreaseApproval(address _spender, uint _subtractedValue) public whenNotPaused returns (bool success) {
        return super.decreaseApproval(_spender, _subtractedValue);
    }
}

/**
 * @title Mintable token
 * @dev Simple ERC20 Token example, with mintable token creation
 * @dev Issue: * https://github.com/OpenZeppelin/zeppelin-solidity/issues/120
 * Based on code by TokenMarketNet: https://github.com/TokenMarketNet/ico/blob/master/contracts/MintableToken.sol
 */

contract MintableToken is StandardToken, Ownable {
    event Mint(address indexed to, uint256 amount);
    event MintFinished();

    bool public mintingFinished = false;


    modifier canMint() {
        require(!mintingFinished);
        _;
    }

    /**
     * @dev Function to mint tokens
     * @param _to The address that will receive the minted tokens.
     * @param _amount The amount of tokens to mint.
     * @return A boolean that indicates if the operation was successful.
     */
    function mint(address _to, uint256 _amount) onlyOwner canMint public returns (bool) {
        totalSupply = totalSupply.add(_amount);
        balances[_to] = balances[_to].add(_amount);
        Mint(_to, _amount);
        Transfer(0x0, _to, _amount);
        return true;
    }

    /**
     * @dev Function to stop minting new tokens.
     * @return True if the operation was successful.
     */
    function finishMinting() onlyOwner public returns (bool) {
        mintingFinished = true;
        MintFinished();
        return true;
    }
}

/**
 * @title Signals token
 * @dev Mintable token created for Signals.Network
 */
contract SignalsToken is PausableToken, MintableToken {

    // Standard token variables
    string constant public name = "SGNPresaleToken";
    string constant public symbol = "SGN";
    uint8 constant public decimals = 9;

    event TokensBurned(address initiatior, address indexed _partner, uint256 _tokens);

    /*
     * Constructor which pauses the token at the time of creation
     */
    function SignalsToken() {
        pause();
    }
    /*
    * @dev Token burn function to be called at the time of token swap
    * @param _partner address to use for token balance buring
    * @param _tokens uint256 amount of tokens to burn
    */
    function burnTokens(address _partner, uint256 _tokens) public onlyOwner {
        require(balances[_partner] >= _tokens);

        balances[_partner] -= _tokens;
        totalSupply -= _tokens;
        TokensBurned(msg.sender, _partner, _tokens);
    }
}

// Public PreSale register contract
contract PresaleRegister is Ownable {

    mapping (address => bool) verified;
    event ApprovedInvestor(address indexed investor);

    /*
     * Approve function to adjust allowance to investment of each individual investor
     * @param _investor address sets the beneficiary for later use
     * @param _amount uint256 is the newly assigned allowance of tokens to buy
    */
    function approve(address _investor) onlyOwner public{
        verified[_investor] = true;
        ApprovedInvestor(_investor);
    }

    /*
     * Constant call to find out if an investor is registered
     * @param _investor address to be checked
     * @return bool is true is _investor was approved
     */
    function approved(address _investor) constant public returns (bool) {
        return verified[_investor];
    }

}

/**
 * @title Crowdsale
 * @dev Crowdsale is a base contract for managing a token crowdsale.
 * Crowdsales have a start and end timestamps, where investors can make
 * token purchases and the crowdsale will assign them tokens based
 * on a token per ETH rate. Funds collected are forwarded to a wallet
 * as they arrive.
 */
contract Crowdsale {
    using SafeMath for uint256;

    // The token being sold
    SignalsToken public token;

    // start and end timestamps where investments are allowed (both inclusive)
    uint256 public startTime;
    uint256 public endTime;

    // address where funds are collected
    address public wallet;

    // amount of raised money in wei
    uint256 public weiRaised;

    /**
     * event for token purchase logging
     * @param purchaser who paid for the tokens
     * @param beneficiary who got the tokens
     * @param value weis paid for purchase
     * @param amount amount of tokens purchased
     */
    event TokenPurchase(address indexed purchaser, address indexed beneficiary, uint256 value, uint256 amount);


    function Crowdsale(uint256 _startTime, uint256 _endTime, address _wallet, SignalsToken _tokenAddress) {
        require(_startTime >= now);
        require(_endTime >= _startTime);
        require(_wallet != 0x0);

        token = _tokenAddress;
        startTime = _startTime;
        endTime = _endTime;
        wallet = _wallet;
    }


    // fallback function can be used to buy tokens
    function () payable {
        buyTokens(msg.sender);
    }

    // low level token purchase function
    function buyTokens(address beneficiary) private {}

    // send ether to the fund collection wallet
    // override to create custom fund forwarding mechanisms
    function forwardFunds() internal {
        wallet.transfer(msg.value);
    }

    // @return true if the transaction can buy tokens
    function validPurchase() internal constant returns (bool) {
        bool withinPeriod = now >= startTime && now <= endTime;
        bool nonZeroPurchase = msg.value != 0;
        return withinPeriod && nonZeroPurchase;
    }

    // @return true if crowdsale event has ended
    function hasEnded() public constant returns (bool) {
        return now > endTime;
    }


}

/**
 * @title FinalizableCrowdsale
 * @dev Extension of Crowdsale where an owner can do extra work
 * after finishing.
 */
contract FinalizableCrowdsale is Crowdsale, Ownable {
    using SafeMath for uint256;

    bool public isFinalized = false;

    event Finalized();

    /**
     * @dev Must be called after crowdsale ends, to do some extra finalization
     * work. Calls the contract's finalization function.
     */
    function finalize() onlyOwner public {
        require(!isFinalized);
        require(hasEnded());

        finalization();
        Finalized();

        isFinalized = true;
    }

    /**
     * @dev Can be overridden to add finalization logic. The overriding function
     * should call super.finalization() to ensure the chain of finalization is
     * executed entirely.
     */
    function finalization() internal {
    }
}


/**
 * @title Signals token pre-sale
 * @dev Curated pre-sale contract based on OpenZeppelin implementations
 */
contract PublicPresale is FinalizableCrowdsale {

    // define PublicPresale depended variables
    uint256 tokensSold;
    uint256 toBeSold;
    uint256 price;
    PresaleRegister public register;

    event PresaleExtended(uint256 newEndTime);

    /**
     * @dev The constructor
     * @param _startTime uint256 is a time stamp of presale start
     * @param _endTime uint256 is a time stamp of presale end (can be changed later)
     * @param _wallet address is the address the funds will go to - it's not a multisig
     * @param _token address is the address of the token contract (ownership is required to handle it)
     * @param _register address is the investor registry
     */
    function PublicPresale(uint256 _startTime, uint256 _endTime, address _wallet, SignalsToken _token, PresaleRegister _register)
    FinalizableCrowdsale()
    Crowdsale(_startTime, _endTime, _wallet, _token)
    {
        register = _register;
        toBeSold = 1969482*1000000000;
        price = 692981;
    }

    /*
     * Buy in function to be called mostly from the fallback function
     * @dev kept public in order to buy for someone else
     * @param beneficiary address
     */
    function buyTokens(address beneficiary) private {
        require(beneficiary != 0x0);
        require(validPurchase());

        // Check the register if the investor was approved
        require(register.approved(beneficiary));

        uint256 weiAmount = msg.value;

        // calculate token amount to be created
        uint256 toGet = howMany(msg.value);

        require((toGet > 0) && (toGet.add(tokensSold) <= toBeSold));

        // update state
        weiRaised = weiRaised.add(weiAmount);
        tokensSold = tokensSold.add(toGet);

        token.mint(beneficiary, toGet);
        TokenPurchase(msg.sender, beneficiary, weiAmount, toGet);

        forwardFunds();

    }

    /*
     * Helper token emission functions
     * @param value uint256 of the wei amount that gets invested
     * @return uint256 of how many tokens can one get
     */
    function howMany(uint256 value) view public returns (uint256){
        return (value/price);
    }

    /*
     * Adjust finalization to transfer token ownership to the fund holding address for further use
     */
    function finalization() internal {
        token.transferOwnership(wallet);
    }

    /*
     * Optional settings to extend the duration
     * @param _newEndTime uint256 is the new time stamp of extended presale duration
     */
    function extendDuration(uint256 _newEndTime) onlyOwner {
        require(!isFinalized);
        require(endTime < _newEndTime);
        endTime = _newEndTime;
        PresaleExtended(_newEndTime);
    }
}