/*
Copyright 2018 Virtual Rehab (http://virtualrehab.co)

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
 */

 pragma solidity 0.4.24;








/**
 * @title ERC20Basic
 * @dev Simpler version of ERC20 interface
 * See https://github.com/ethereum/EIPs/issues/179
 */
contract ERC20Basic {
  function totalSupply() public view returns (uint256);
  function balanceOf(address _who) public view returns (uint256);
  function transfer(address _to, uint256 _value) public returns (bool);
  event Transfer(address indexed from, address indexed to, uint256 value);
}




/**
 * @title SafeMath
 * @dev Math operations with safety checks that throw on error
 */
library SafeMath {

  /**
  * @dev Multiplies two numbers, throws on overflow.
  */
  function mul(uint256 _a, uint256 _b) internal pure returns (uint256 c) {
    // Gas optimization: this is cheaper than asserting 'a' not being zero, but the
    // benefit is lost if 'b' is also tested.
    // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
    if (_a == 0) {
      return 0;
    }

    c = _a * _b;
    assert(c / _a == _b);
    return c;
  }

  /**
  * @dev Integer division of two numbers, truncating the quotient.
  */
  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 _a / _b;
  }

  /**
  * @dev Subtracts two numbers, throws on overflow (i.e. if subtrahend is greater than minuend).
  */
  function sub(uint256 _a, uint256 _b) internal pure returns (uint256) {
    assert(_b <= _a);
    return _a - _b;
  }

  /**
  * @dev Adds two numbers, throws on overflow.
  */
  function add(uint256 _a, uint256 _b) internal pure returns (uint256 c) {
    c = _a + _b;
    assert(c >= _a);
    return c;
  }
}



/**
 * @title Basic token
 * @dev Basic version of StandardToken, with no allowances.
 */
contract BasicToken is ERC20Basic {
  using SafeMath for uint256;

  mapping(address => uint256) internal balances;

  uint256 internal totalSupply_;

  /**
  * @dev Total number of tokens in existence
  */
  function totalSupply() public view returns (uint256) {
    return totalSupply_;
  }

  /**
  * @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) public returns (bool) {
    require(_value <= balances[msg.sender]);
    require(_to != address(0));

    balances[msg.sender] = balances[msg.sender].sub(_value);
    balances[_to] = balances[_to].add(_value);
    emit 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) public view returns (uint256) {
    return balances[_owner];
  }

}






/**
 * @title ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/20
 */
contract ERC20 is ERC20Basic {
  function allowance(address _owner, address _spender)
    public view returns (uint256);

  function transferFrom(address _from, address _to, uint256 _value)
    public returns (bool);

  function approve(address _spender, uint256 _value) public returns (bool);
  event Approval(
    address indexed owner,
    address indexed spender,
    uint256 value
  );
}



/**
 * @title Standard ERC20 token
 *
 * @dev Implementation of the basic standard token.
 * https://github.com/ethereum/EIPs/issues/20
 * 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(_value <= balances[_from]);
    require(_value <= allowed[_from][msg.sender]);
    require(_to != address(0));

    balances[_from] = balances[_from].sub(_value);
    balances[_to] = balances[_to].add(_value);
    allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
    emit 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;
    emit 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
    view
    returns (uint256)
  {
    return allowed[_owner][_spender];
  }

  /**
   * @dev Increase the amount of tokens that an owner allowed to a 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
   * @param _spender The address which will spend the funds.
   * @param _addedValue The amount of tokens to increase the allowance by.
   */
  function increaseApproval(
    address _spender,
    uint256 _addedValue
  )
    public
    returns (bool)
  {
    allowed[msg.sender][_spender] = (
      allowed[msg.sender][_spender].add(_addedValue));
    emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
    return true;
  }

  /**
   * @dev Decrease the amount of tokens that an owner allowed to a spender.
   * approve should be called when allowed[_spender] == 0. To decrement
   * allowed value is better to use this function to avoid 2 calls (and wait until
   * the first transaction is mined)
   * From MonolithDAO Token.sol
   * @param _spender The address which will spend the funds.
   * @param _subtractedValue The amount of tokens to decrease the allowance by.
   */
  function decreaseApproval(
    address _spender,
    uint256 _subtractedValue
  )
    public
    returns (bool)
  {
    uint256 oldValue = allowed[msg.sender][_spender];
    if (_subtractedValue >= oldValue) {
      allowed[msg.sender][_spender] = 0;
    } else {
      allowed[msg.sender][_spender] = oldValue.sub(_subtractedValue);
    }
    emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
    return true;
  }

}






/**
 * @title Burnable Token
 * @dev Token that can be irreversibly burned (destroyed).
 */
contract BurnableToken is BasicToken {

  event Burn(address indexed burner, uint256 value);

  /**
   * @dev Burns a specific amount of tokens.
   * @param _value The amount of token to be burned.
   */
  function burn(uint256 _value) public {
    _burn(msg.sender, _value);
  }

  function _burn(address _who, uint256 _value) internal {
    require(_value <= balances[_who]);
    // no need to require value <= totalSupply, since that would imply the
    // sender's balance is greater than the totalSupply, which *should* be an assertion failure

    balances[_who] = balances[_who].sub(_value);
    totalSupply_ = totalSupply_.sub(_value);
    emit Burn(_who, _value);
    emit Transfer(_who, address(0), _value);
  }
}

/*
Copyright 2018 Binod Nirvan

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
 */





/*
Copyright 2018 Binod Nirvan

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
 */






/**
 * @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 OwnershipRenounced(address indexed previousOwner);
  event OwnershipTransferred(
    address indexed previousOwner,
    address indexed newOwner
  );


  /**
   * @dev The Ownable constructor sets the original `owner` of the contract to the sender
   * account.
   */
  constructor() 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 relinquish control of the contract.
   * @notice Renouncing to ownership will leave the contract without an owner.
   * It will not be possible to call the functions with the `onlyOwner`
   * modifier anymore.
   */
  function renounceOwnership() public onlyOwner {
    emit OwnershipRenounced(owner);
    owner = address(0);
  }

  /**
   * @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) public onlyOwner {
    _transferOwnership(_newOwner);
  }

  /**
   * @dev Transfers control of the contract to a newOwner.
   * @param _newOwner The address to transfer ownership to.
   */
  function _transferOwnership(address _newOwner) internal {
    require(_newOwner != address(0));
    emit OwnershipTransferred(owner, _newOwner);
    owner = _newOwner;
  }
}


contract CustomAdmin is Ownable {
  mapping(address => bool) public admins;
  uint256 public numberOfAdmins;

  event AdminAdded(address indexed addr);
  event AdminRemoved(address indexed addr);

  /**
   * @dev Throws if called by any account that's not an administrator.
   */
  modifier onlyAdmin() {
    require(admins[msg.sender] || msg.sender == owner);
    _;
  }

  constructor() public {
    admins[msg.sender] = true;
    numberOfAdmins = 1;

    emit AdminAdded(msg.sender);
  }
  /**
   * @dev Add an address to the adminstrator list.
   * @param addr address
   */
  function addAdmin(address addr) onlyAdmin  public {
    require(addr != address(0));
    require(!admins[addr]);

    admins[addr] = true;
    numberOfAdmins++;

    emit AdminAdded(addr);
  }

  /**
   * @dev Remove an address from the administrator list.
   * @param addr address
   */
  function removeAdmin(address addr) onlyAdmin  public {
    require(addr != address(0));
    require(admins[addr]);
    //the owner can not be unadminsed
    require(addr != owner);

    admins[addr] = false;
    numberOfAdmins--;

    emit AdminRemoved(addr);
  }
}



/**
 * @title Pausable
 * @dev Base contract which allows children to implement an emergency stop mechanism.
 */
contract CustomPausable is CustomAdmin {
  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() onlyAdmin whenNotPaused public {
    paused = true;
    emit Pause();
  }

  /**
   * @dev called by the owner to unpause, returns to normal state
   */
  function unpause() onlyAdmin whenPaused public {
    paused = false;
    emit Unpause();
  }
}


///@title Virtual Rehab Token (VRH) ERC20 Token Contract
///@author Binod Nirvan, Subramanian Venkatesan (http://virtualrehab.co)
///@notice The Virtual Rehab Token (VRH) has been created as a centralized currency
///to be used within the Virtual Rehab network. Users will be able to purchase and sell
///VRH tokens in exchanges. The token follows the standards of Ethereum ERC20 Standard token.
///Its design follows the widely adopted token implementation standards.
///This allows token holders to easily store and manage their VRH tokens using existing solutions
///including ERC20-compatible Ethereum wallets. The VRH Token is a utility token
///and is core to Virtual Rehab’s end-to-end operations.
///
///VRH utility use cases include:
///1- Order & Download Virtual Rehab programs through the Virtual Rehab Online Portal
///2- Request further analysis, conducted by Virtual Rehab's unique expert system (which leverages Artificial Intelligence), of the executed programs
///3- Receive incentives (VRH rewards) for seeking help and counselling from psychologists, therapists, or medical doctors
contract VRHToken is StandardToken, CustomPausable, BurnableToken {
  uint8 public constant decimals = 18;
  string public constant name = "Virtual Rehab";
  string public constant symbol = "VRH";

  uint public constant MAX_SUPPLY = 400000000 * (10 ** uint256(decimals));
  uint public constant INITIAL_SUPPLY = (400000000 - 750000 - 2085000 - 60000000) * (10 ** uint256(decimals));

  bool public released = false;
  uint public ICOEndDate;


  mapping(bytes32 => bool) private mintingList;

  event Mint(address indexed to, uint256 amount);
  event BulkTransferPerformed(address[] _destinations, uint256[] _amounts);
  event TokenReleased(bool _state);
  event ICOEndDateSet(uint256 _date);

  ///@notice Checks if the supplied address is able to perform transfers.
  ///@param _from The address to check against if the transfer is allowed.
  modifier canTransfer(address _from) {
    if(paused || !released) {
      if(!admins[_from]) {
        revert();
      }
    }

    _;
  }

  ///@notice Computes keccak256 hash of the supplied value.
  ///@param _key The string value to compute hash from.
  function computeHash(string _key) private pure returns(bytes32){
    return keccak256(abi.encodePacked(_key));
  }

  ///@notice Checks if the minting for the supplied key was already performed.
  ///@param _key The key or category name of minting.
  modifier whenNotMinted(string _key) {
    if(mintingList[computeHash(_key)]) {
      revert();
    }

    _;
  }

  constructor() public {
    mintTokens(msg.sender, INITIAL_SUPPLY);
    emit Transfer(address(0), msg.sender, totalSupply_);
  }



  ///@notice This function enables token transfers for everyone.
  ///Can only be enabled after the end of the ICO.
  function releaseTokenForTransfer() public onlyAdmin whenNotPaused {
    require(!released);

    released = true;

    emit TokenReleased(released);
  }

  ///@notice This function disables token transfers for everyone.
  function disableTokenTransfers() public onlyAdmin whenNotPaused {
    require(released);

    released = false;

    emit TokenReleased(released);
  }

  ///@notice This function enables the whitelisted application (internal application) to set the ICO end date and can only be used once.
  ///@param _date The date to set as the ICO end date.
  function setICOEndDate(uint _date) public onlyAdmin {
    require(ICOEndDate == 0);
    require(_date > now);

    ICOEndDate = _date;

    emit ICOEndDateSet(_date);
  }

  ///@notice Mints the supplied value of the tokens to the destination address.
  //Minting cannot be performed any further once the maximum supply is reached.
  //This function is private and cannot be used by anyone except for this contract.
  ///@param _to The address which will receive the minted tokens.
  ///@param _value The amount of tokens to mint.
  function mintTokens(address _to, uint _value) private {
    require(_to != address(0));
    require(totalSupply_.add(_value) <= MAX_SUPPLY);

    balances[_to] = balances[_to].add(_value);
    totalSupply_ = totalSupply_.add(_value);

    emit Mint(_to, _value);
    emit Transfer(address(0), _to, _value);
  }

  ///@notice Mints the tokens only once against the supplied key (category).
  ///@param _key The key or the category of the allocation to mint the tokens for.
  ///@param _to The address receiving the minted tokens.
  ///@param _amount The amount of tokens to mint.
  function mintOnce(string _key, address _to, uint256 _amount) private whenNotPaused whenNotMinted(_key) {
    _amount = _amount * (10 ** uint256(decimals));
    mintTokens(_to, _amount);
    mintingList[computeHash(_key)] = true;
  }

  ///@notice Mints the below-mentioned amount of tokens allocated to the Virtual Rehab advisors.
  //The tokens are only available to the advisors after 1 year of the ICO end.
  function mintTokensForAdvisors() public onlyAdmin {
    require(ICOEndDate != 0);

    require(now > (ICOEndDate + 365 days));
    mintOnce("advisors", msg.sender, 750000);
  }

  ///@notice Mints the below-mentioned amount of tokens allocated to the Virtual Rehab founders.
  //The tokens are only available to the founders after 1 year of the ICO end.
  function mintTokensForFounders() public onlyAdmin {
    require(ICOEndDate != 0);
    require(now > (ICOEndDate + 365 days));

    mintOnce("founders", msg.sender, 60000000);
  }

  ///@notice Mints the below-mentioned amount of tokens allocated to Virtual Rehab services.
  //The tokens are only available to the services after 1 year of the ICO end.
  function mintTokensForServices() public onlyAdmin  {
    require(ICOEndDate != 0);
    require(now > (ICOEndDate + 60 days));

    mintOnce("services", msg.sender, 2085000);
  }

  ///@notice Transfers the specified value of VRH tokens to the destination address.
  //Transfers can only happen when the tranfer state is enabled.
  //Transfer state can only be enabled after the end of the crowdsale.
  ///@param _to The destination wallet address to transfer funds to.
  ///@param _value The amount of tokens to send to the destination address.
  function transfer(address _to, uint256 _value) public canTransfer(msg.sender) returns (bool) {
    require(_to != address(0));
    return super.transfer(_to, _value);
  }

  ///@notice Transfers tokens from a specified wallet address.
  ///@dev This function is overriden to leverage transfer state feature.
  ///@param _from The address to transfer funds from.
  ///@param _to The address to transfer funds to.
  ///@param _value The amount of tokens to transfer.
  function transferFrom(address _from, address _to, uint256 _value) canTransfer(_from) public returns (bool) {
    require(_to != address(0));
    return super.transferFrom(_from, _to, _value);
  }

  ///@notice Approves a wallet address to spend on behalf of the sender.
  ///@dev This function is overriden to leverage transfer state feature.
  ///@param _spender The address which is approved to spend on behalf of the sender.
  ///@param _value The amount of tokens approve to spend.
  function approve(address _spender, uint256 _value) public canTransfer(msg.sender) returns (bool) {
    require(_spender != address(0));
    return super.approve(_spender, _value);
  }


  ///@notice Increases the approval of the spender.
  ///@dev This function is overriden to leverage transfer state feature.
  ///@param _spender The address which is approved to spend on behalf of the sender.
  ///@param _addedValue The added amount of tokens approved to spend.
  function increaseApproval(address _spender, uint256 _addedValue) public canTransfer(msg.sender) returns(bool) {
    require(_spender != address(0));
    return super.increaseApproval(_spender, _addedValue);
  }

  ///@notice Decreases the approval of the spender.
  ///@dev This function is overriden to leverage transfer state feature.
  ///@param _spender The address of the spender to decrease the allocation from.
  ///@param _subtractedValue The amount of tokens to subtract from the approved allocation.
  function decreaseApproval(address _spender, uint256 _subtractedValue) public canTransfer(msg.sender) returns (bool) {
    require(_spender != address(0));
    return super.decreaseApproval(_spender, _subtractedValue);
  }

  ///@notice Returns the sum of supplied values.
  ///@param _values The collection of values to create the sum from.
  function sumOf(uint256[] _values) private pure returns(uint256) {
    uint256 total = 0;

    for (uint256 i = 0; i < _values.length; i++) {
      total = total.add(_values[i]);
    }

    return total;
  }

  ///@notice Allows only the admins and/or whitelisted applications to perform bulk transfer operation.
  ///@param _destinations The destination wallet addresses to send funds to.
  ///@param _amounts The respective amount of fund to send to the specified addresses.
  function bulkTransfer(address[] _destinations, uint256[] _amounts) public onlyAdmin {
    require(_destinations.length == _amounts.length);

    //Saving gas by determining if the sender has enough balance
    //to post this transaction.
    uint256 requiredBalance = sumOf(_amounts);
    require(balances[msg.sender] >= requiredBalance);

    for (uint256 i = 0; i < _destinations.length; i++) {
     transfer(_destinations[i], _amounts[i]);
    }

    emit BulkTransferPerformed(_destinations, _amounts);
  }

  ///@notice Burns the coins held by the sender.
  ///@param _value The amount of coins to burn.
  ///@dev This function is overriden to leverage Pausable feature.
  function burn(uint256 _value) public whenNotPaused {
    super.burn(_value);
  }
}