pragma solidity ^0.4.23;

// File: contracts/NokuPricingPlan.sol

/**
* @dev The NokuPricingPlan contract defines the responsibilities of a Noku pricing plan.
*/
contract NokuPricingPlan {
    /**
    * @dev Pay the fee for the service identified by the specified name.
    * The fee amount shall already be approved by the client.
    * @param serviceName The name of the target service.
    * @param multiplier The multiplier of the base service fee to apply.
    * @param client The client of the target service.
    * @return true if fee has been paid.
    */
    function payFee(bytes32 serviceName, uint256 multiplier, address client) public returns(bool paid);

    /**
    * @dev Get the usage fee for the service identified by the specified name.
    * The returned fee amount shall be approved before using #payFee method.
    * @param serviceName The name of the target service.
    * @param multiplier The multiplier of the base service fee to apply.
    * @return The amount to approve before really paying such fee.
    */
    function usageFee(bytes32 serviceName, uint256 multiplier) public constant returns(uint fee);
}

// File: openzeppelin-solidity/contracts/ownership/Ownable.sol

/**
 * @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) public onlyOwner {
    require(newOwner != address(0));
    emit OwnershipTransferred(owner, newOwner);
    owner = newOwner;
  }

}

// File: openzeppelin-solidity/contracts/lifecycle/Pausable.sol

/**
 * @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;
    emit Pause();
  }

  /**
   * @dev called by the owner to unpause, returns to normal state
   */
  function unpause() onlyOwner whenPaused public {
    paused = false;
    emit Unpause();
  }
}

// File: openzeppelin-solidity/contracts/math/SafeMath.sol

/**
 * @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) {
    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;
  }
}

// File: openzeppelin-solidity/contracts/token/ERC20/ERC20Basic.sol

/**
 * @title ERC20Basic
 * @dev Simpler version of ERC20 interface
 * @dev 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);
}

// File: openzeppelin-solidity/contracts/token/ERC20/ERC20.sol

/**
 * @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);
}

// File: contracts/NokuTokenBurner.sol

contract BurnableERC20 is ERC20 {
    function burn(uint256 amount) public returns (bool burned);
}

/**
* @dev The NokuTokenBurner contract has the responsibility to burn the configured fraction of received
* ERC20-compliant tokens and distribute the remainder to the configured wallet.
*/
contract NokuTokenBurner is Pausable {
    using SafeMath for uint256;

    event LogNokuTokenBurnerCreated(address indexed caller, address indexed wallet);
    event LogBurningPercentageChanged(address indexed caller, uint256 indexed burningPercentage);

    // The wallet receiving the unburnt tokens.
    address public wallet;

    // The percentage of tokens to burn after being received (range [0, 100])
    uint256 public burningPercentage;

    // The cumulative amount of burnt tokens.
    uint256 public burnedTokens;

    // The cumulative amount of tokens transferred back to the wallet.
    uint256 public transferredTokens;

    /**
    * @dev Create a new NokuTokenBurner with predefined burning fraction.
    * @param _wallet The wallet receiving the unburnt tokens.
    */
    constructor(address _wallet) public {
        require(_wallet != address(0), "_wallet is zero");
        
        wallet = _wallet;
        burningPercentage = 100;

        emit LogNokuTokenBurnerCreated(msg.sender, _wallet);
    }

    /**
    * @dev Change the percentage of tokens to burn after being received.
    * @param _burningPercentage The percentage of tokens to be burnt.
    */
    function setBurningPercentage(uint256 _burningPercentage) public onlyOwner {
        require(0 <= _burningPercentage && _burningPercentage <= 100, "_burningPercentage not in [0, 100]");
        require(_burningPercentage != burningPercentage, "_burningPercentage equal to current one");
        
        burningPercentage = _burningPercentage;

        emit LogBurningPercentageChanged(msg.sender, _burningPercentage);
    }

    /**
    * @dev Called after burnable tokens has been transferred for burning.
    * @param _token THe extended ERC20 interface supported by the sent tokens.
    * @param _amount The amount of burnable tokens just arrived ready for burning.
    */
    function tokenReceived(address _token, uint256 _amount) public whenNotPaused {
        require(_token != address(0), "_token is zero");
        require(_amount > 0, "_amount is zero");

        uint256 amountToBurn = _amount.mul(burningPercentage).div(100);
        if (amountToBurn > 0) {
            assert(BurnableERC20(_token).burn(amountToBurn));
            
            burnedTokens = burnedTokens.add(amountToBurn);
        }

        uint256 amountToTransfer = _amount.sub(amountToBurn);
        if (amountToTransfer > 0) {
            assert(BurnableERC20(_token).transfer(wallet, amountToTransfer));

            transferredTokens = transferredTokens.add(amountToTransfer);
        }
    }
}

// File: contracts/NokuConsumptionPlan.sol

/**
* @dev The NokuConsumptionPlan contract implements a flexible pricing plan, manageable by the contract owner, which can be:
* - extended by inserting a new service with its associated fee
* - modified by updating an existing service fee
* - reduced by removing an existing service with its associated fee
* - queried to obtain the count of services
* The service [name, fee] association is maintained using an index in order to make the data traversable.
*/
contract NokuConsumptionPlan is NokuPricingPlan, Ownable {
    using SafeMath for uint256;

    event LogNokuConsumptionPlanCreated(address indexed caller, address indexed nokuMasterToken, address indexed tokenBurner);
    event LogServiceAdded(bytes32 indexed serviceName, uint indexed index, uint indexed serviceFee);
    event LogServiceChanged(bytes32 indexed serviceName, uint indexed index, uint indexed serviceFee);
    event LogServiceRemoved(bytes32 indexed serviceName, uint indexed index);
    
    struct NokuService {
        uint serviceFee;
        uint index;
    }

    bytes32[] private serviceIndex;

    mapping(bytes32 => NokuService) private services;

    // The NOKU utility token used for paying fee  
    address public nokuMasterToken;

    // The contract responsible for burning the NOKU tokens paid as service fee
    address public tokenBurner;

    constructor(address _nokuMasterToken, address _tokenBurner) public {
        require(_nokuMasterToken != 0, "_nokuMasterToken is zero");
        require(_tokenBurner != 0, "_tokenBurner is zero");

        nokuMasterToken = _nokuMasterToken;
        tokenBurner = _tokenBurner;

        emit LogNokuConsumptionPlanCreated(msg.sender, _nokuMasterToken, _tokenBurner);
    }

    function isService(bytes32 _serviceName) public constant returns(bool isIndeed) {
        require(_serviceName != 0, "_serviceName is zero");

        if (serviceIndex.length == 0)
            return false;
        else
            return (serviceIndex[services[_serviceName].index] == _serviceName);
    }

    function addService(bytes32 _serviceName, uint _serviceFee) public onlyOwner returns(uint index) {
        require(!isService(_serviceName), "_serviceName already present");

        services[_serviceName].serviceFee = _serviceFee;
        services[_serviceName].index = serviceIndex.push(_serviceName)-1;

        emit LogServiceAdded(_serviceName, serviceIndex.length-1, _serviceFee);

        return serviceIndex.length-1;
    }

    function removeService(bytes32 _serviceName) public onlyOwner returns(uint index) {
        require(isService(_serviceName), "_serviceName not present");

        uint rowToDelete = services[_serviceName].index;
        bytes32 keyToMove = serviceIndex[serviceIndex.length-1];
        serviceIndex[rowToDelete] = keyToMove;
        services[keyToMove].index = rowToDelete; 
        serviceIndex.length--;

        emit LogServiceRemoved(_serviceName,  rowToDelete);
        emit LogServiceChanged(keyToMove, rowToDelete, services[keyToMove].serviceFee);

        return rowToDelete;
    }

    function updateServiceFee(bytes32 _serviceName, uint _serviceFee) public onlyOwner returns(bool success) {
        require(isService(_serviceName), "_serviceName not present");

        services[_serviceName].serviceFee = _serviceFee;

        emit LogServiceChanged(_serviceName, services[_serviceName].index, _serviceFee);

        return true;
    }

    function payFee(bytes32 _serviceName, uint256 _amount, address _client) public returns(bool paid) {
        //require(isService(_serviceName)); // Already checked by #usageFee
        //require(_amount != 0); // Already checked by #usageFee
        require(_client != 0, "_client is zero");

        uint256 fee = usageFee(_serviceName, _amount);
        if (fee == 0) return true;

        require(ERC20(nokuMasterToken).transferFrom(_client, tokenBurner, fee), "NOKU fee payment failed");

        NokuTokenBurner(tokenBurner).tokenReceived(nokuMasterToken, fee);

        return true;
    }

    function usageFee(bytes32 _serviceName, uint256 _amount) public constant returns(uint fee) {
        require(isService(_serviceName), "_serviceName not present");
        require(_amount != 0, "_amount is zero");
        
        // Assume fee are represented in 18-decimals notation
        return _amount.mul(services[_serviceName].serviceFee).div(10**18);
    }

    function serviceCount() public constant returns(uint count) {
        return serviceIndex.length;
    }

    function serviceAtIndex(uint _index) public constant returns(bytes32 serviceName) {
        return serviceIndex[_index];
    }
}