pragma solidity 0.4.25;

// File: contracts/LinkedListLib.sol

/**
 * @title LinkedListLib
 * @author Darryl Morris (o0ragman0o) and Modular.network
 *
 * This utility library was forked from https://github.com/o0ragman0o/LibCLL
 * into the Modular-Network ethereum-libraries repo at https://github.com/Modular-Network/ethereum-libraries
 * It has been updated to add additional functionality and be more compatible with solidity 0.4.18
 * coding patterns.
 *
 * version 1.1.1
 * Copyright (c) 2017 Modular Inc.
 * The MIT License (MIT)
 * https://github.com/Modular-network/ethereum-libraries/blob/master/LICENSE
 *
 * The LinkedListLib provides functionality for implementing data indexing using
 * a circlular linked list
 *
 * Modular provides smart contract services and security reviews for contract
 * deployments in addition to working on open source projects in the Ethereum
 * community. Our purpose is to test, document, and deploy reusable code onto the
 * blockchain and improve both security and usability. We also educate non-profits,
 * schools, and other community members about the application of blockchain
 * technology. For further information: modular.network
 *
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/


library LinkedListLib {

    uint256 constant NULL = 0;
    uint256 constant HEAD = 0;
    bool constant PREV = false;
    bool constant NEXT = true;

    struct LinkedList{
        mapping (uint256 => mapping (bool => uint256)) list;
    }

    /// @dev returns true if the list exists
    /// @param self stored linked list from contract
    function listExists(LinkedList storage self)
        public
        view returns (bool)
    {
        // if the head nodes previous or next pointers both point to itself, then there are no items in the list
        if (self.list[HEAD][PREV] != HEAD || self.list[HEAD][NEXT] != HEAD) {
            return true;
        } else {
            return false;
        }
    }

    /// @dev returns true if the node exists
    /// @param self stored linked list from contract
    /// @param _node a node to search for
    function nodeExists(LinkedList storage self, uint256 _node)
        public
        view returns (bool)
    {
        if (self.list[_node][PREV] == HEAD && self.list[_node][NEXT] == HEAD) {
            if (self.list[HEAD][NEXT] == _node) {
                return true;
            } else {
                return false;
            }
        } else {
            return true;
        }
    }

    /// @dev Returns the number of elements in the list
    /// @param self stored linked list from contract
    function sizeOf(LinkedList storage self) public view returns (uint256 numElements) {
        bool exists;
        uint256 i;
        (exists,i) = getAdjacent(self, HEAD, NEXT);
        while (i != HEAD) {
            (exists,i) = getAdjacent(self, i, NEXT);
            numElements++;
        }
        return;
    }

    /// @dev Returns the links of a node as a tuple
    /// @param self stored linked list from contract
    /// @param _node id of the node to get
    function getNode(LinkedList storage self, uint256 _node)
        public view returns (bool,uint256,uint256)
    {
        if (!nodeExists(self,_node)) {
            return (false,0,0);
        } else {
            return (true,self.list[_node][PREV], self.list[_node][NEXT]);
        }
    }

    /// @dev Returns the link of a node `_node` in direction `_direction`.
    /// @param self stored linked list from contract
    /// @param _node id of the node to step from
    /// @param _direction direction to step in
    function getAdjacent(LinkedList storage self, uint256 _node, bool _direction)
        public view returns (bool,uint256)
    {
        if (!nodeExists(self,_node)) {
            return (false,0);
        } else {
            return (true,self.list[_node][_direction]);
        }
    }

    /// @dev Can be used before `insert` to build an ordered list
    /// @param self stored linked list from contract
    /// @param _node an existing node to search from, e.g. HEAD.
    /// @param _value value to seek
    /// @param _direction direction to seek in
    //  @return next first node beyond '_node' in direction `_direction`
    function getSortedSpot(LinkedList storage self, uint256 _node, uint256 _value, bool _direction)
        public view returns (uint256)
    {
        if (sizeOf(self) == 0) { return 0; }
        require((_node == 0) || nodeExists(self,_node));
        bool exists;
        uint256 next;
        (exists,next) = getAdjacent(self, _node, _direction);
        while  ((next != 0) && (_value != next) && ((_value < next) != _direction)) next = self.list[next][_direction];
        return next;
    }

    /// @dev Creates a bidirectional link between two nodes on direction `_direction`
    /// @param self stored linked list from contract
    /// @param _node first node for linking
    /// @param _link  node to link to in the _direction
    function createLink(LinkedList storage self, uint256 _node, uint256 _link, bool _direction) private  {
        self.list[_link][!_direction] = _node;
        self.list[_node][_direction] = _link;
    }

    /// @dev Insert node `_new` beside existing node `_node` in direction `_direction`.
    /// @param self stored linked list from contract
    /// @param _node existing node
    /// @param _new  new node to insert
    /// @param _direction direction to insert node in
    function insert(LinkedList storage self, uint256 _node, uint256 _new, bool _direction) internal returns (bool) {
        if(!nodeExists(self,_new) && nodeExists(self,_node)) {
            uint256 c = self.list[_node][_direction];
            createLink(self, _node, _new, _direction);
            createLink(self, _new, c, _direction);
            return true;
        } else {
            return false;
        }
    }

    /// @dev removes an entry from the linked list
    /// @param self stored linked list from contract
    /// @param _node node to remove from the list
    function remove(LinkedList storage self, uint256 _node) internal returns (uint256) {
        if ((_node == NULL) || (!nodeExists(self,_node))) { return 0; }
        createLink(self, self.list[_node][PREV], self.list[_node][NEXT], NEXT);
        delete self.list[_node][PREV];
        delete self.list[_node][NEXT];
        return _node;
    }

    /// @dev pushes an enrty to the head of the linked list
    /// @param self stored linked list from contract
    /// @param _node new entry to push to the head
    /// @param _direction push to the head (NEXT) or tail (PREV)
    function push(LinkedList storage self, uint256 _node, bool _direction) internal  {
        insert(self, HEAD, _node, _direction);
    }

    /// @dev pops the first entry from the linked list
    /// @param self stored linked list from contract
    /// @param _direction pop from the head (NEXT) or the tail (PREV)
    function pop(LinkedList storage self, bool _direction) internal returns (uint256) {
        bool exists;
        uint256 adj;

        (exists,adj) = getAdjacent(self, HEAD, _direction);

        return remove(self, adj);
    }
}

// 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 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.
   */
  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;
  }
}

// File: openzeppelin-solidity/contracts/ownership/rbac/Roles.sol

/**
 * @title Roles
 * @author Francisco Giordano (@frangio)
 * @dev Library for managing addresses assigned to a Role.
 *      See RBAC.sol for example usage.
 */
library Roles {
  struct Role {
    mapping (address => bool) bearer;
  }

  /**
   * @dev give an address access to this role
   */
  function add(Role storage role, address addr)
    internal
  {
    role.bearer[addr] = true;
  }

  /**
   * @dev remove an address' access to this role
   */
  function remove(Role storage role, address addr)
    internal
  {
    role.bearer[addr] = false;
  }

  /**
   * @dev check if an address has this role
   * // reverts
   */
  function check(Role storage role, address addr)
    view
    internal
  {
    require(has(role, addr));
  }

  /**
   * @dev check if an address has this role
   * @return bool
   */
  function has(Role storage role, address addr)
    view
    internal
    returns (bool)
  {
    return role.bearer[addr];
  }
}

// File: openzeppelin-solidity/contracts/ownership/rbac/RBAC.sol

/**
 * @title RBAC (Role-Based Access Control)
 * @author Matt Condon (@Shrugs)
 * @dev Stores and provides setters and getters for roles and addresses.
 * @dev Supports unlimited numbers of roles and addresses.
 * @dev See //contracts/mocks/RBACMock.sol for an example of usage.
 * This RBAC method uses strings to key roles. It may be beneficial
 *  for you to write your own implementation of this interface using Enums or similar.
 * It's also recommended that you define constants in the contract, like ROLE_ADMIN below,
 *  to avoid typos.
 */
contract RBAC {
  using Roles for Roles.Role;

  mapping (string => Roles.Role) private roles;

  event RoleAdded(address addr, string roleName);
  event RoleRemoved(address addr, string roleName);

  /**
   * @dev reverts if addr does not have role
   * @param addr address
   * @param roleName the name of the role
   * // reverts
   */
  function checkRole(address addr, string roleName)
    view
    public
  {
    roles[roleName].check(addr);
  }

  /**
   * @dev determine if addr has role
   * @param addr address
   * @param roleName the name of the role
   * @return bool
   */
  function hasRole(address addr, string roleName)
    view
    public
    returns (bool)
  {
    return roles[roleName].has(addr);
  }

  /**
   * @dev add a role to an address
   * @param addr address
   * @param roleName the name of the role
   */
  function addRole(address addr, string roleName)
    internal
  {
    roles[roleName].add(addr);
    emit RoleAdded(addr, roleName);
  }

  /**
   * @dev remove a role from an address
   * @param addr address
   * @param roleName the name of the role
   */
  function removeRole(address addr, string roleName)
    internal
  {
    roles[roleName].remove(addr);
    emit RoleRemoved(addr, roleName);
  }

  /**
   * @dev modifier to scope access to a single role (uses msg.sender as addr)
   * @param roleName the name of the role
   * // reverts
   */
  modifier onlyRole(string roleName)
  {
    checkRole(msg.sender, roleName);
    _;
  }

  /**
   * @dev modifier to scope access to a set of roles (uses msg.sender as addr)
   * @param roleNames the names of the roles to scope access to
   * // reverts
   *
   * @TODO - when solidity supports dynamic arrays as arguments to modifiers, provide this
   *  see: https://github.com/ethereum/solidity/issues/2467
   */
  // modifier onlyRoles(string[] roleNames) {
  //     bool hasAnyRole = false;
  //     for (uint8 i = 0; i < roleNames.length; i++) {
  //         if (hasRole(msg.sender, roleNames[i])) {
  //             hasAnyRole = true;
  //             break;
  //         }
  //     }

  //     require(hasAnyRole);

  //     _;
  // }
}

// File: openzeppelin-solidity/contracts/ownership/Whitelist.sol

/**
 * @title Whitelist
 * @dev The Whitelist contract has a whitelist of addresses, and provides basic authorization control functions.
 * @dev This simplifies the implementation of "user permissions".
 */
contract Whitelist is Ownable, RBAC {
  event WhitelistedAddressAdded(address addr);
  event WhitelistedAddressRemoved(address addr);

  string public constant ROLE_WHITELISTED = "whitelist";

  /**
   * @dev Throws if called by any account that's not whitelisted.
   */
  modifier onlyWhitelisted() {
    checkRole(msg.sender, ROLE_WHITELISTED);
    _;
  }

  /**
   * @dev add an address to the whitelist
   * @param addr address
   * @return true if the address was added to the whitelist, false if the address was already in the whitelist
   */
  function addAddressToWhitelist(address addr)
    onlyOwner
    public
  {
    addRole(addr, ROLE_WHITELISTED);
    emit WhitelistedAddressAdded(addr);
  }

  /**
   * @dev getter to determine if address is in whitelist
   */
  function whitelist(address addr)
    public
    view
    returns (bool)
  {
    return hasRole(addr, ROLE_WHITELISTED);
  }

  /**
   * @dev add addresses to the whitelist
   * @param addrs addresses
   * @return true if at least one address was added to the whitelist,
   * false if all addresses were already in the whitelist
   */
  function addAddressesToWhitelist(address[] addrs)
    onlyOwner
    public
  {
    for (uint256 i = 0; i < addrs.length; i++) {
      addAddressToWhitelist(addrs[i]);
    }
  }

  /**
   * @dev remove an address from the whitelist
   * @param addr address
   * @return true if the address was removed from the whitelist,
   * false if the address wasn't in the whitelist in the first place
   */
  function removeAddressFromWhitelist(address addr)
    onlyOwner
    public
  {
    removeRole(addr, ROLE_WHITELISTED);
    emit WhitelistedAddressRemoved(addr);
  }

  /**
   * @dev remove addresses from the whitelist
   * @param addrs addresses
   * @return true if at least one address was removed from the whitelist,
   * false if all addresses weren't in the whitelist in the first place
   */
  function removeAddressesFromWhitelist(address[] addrs)
    onlyOwner
    public
  {
    for (uint256 i = 0; i < addrs.length; i++) {
      removeAddressFromWhitelist(addrs[i]);
    }
  }

}

// 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) {
    // 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;
  }
}

// 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/BasicToken.sol

/**
 * @title Basic token
 * @dev Basic version of StandardToken, with no allowances.
 */
contract BasicToken is ERC20Basic {
  using SafeMath for uint256;

  mapping(address => uint256) balances;

  uint256 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(_to != address(0));
    require(_value <= balances[msg.sender]);

    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];
  }

}

// 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: openzeppelin-solidity/contracts/token/ERC20/StandardToken.sol

/**
 * @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);
    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,
    uint _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,
    uint _subtractedValue
  )
    public
    returns (bool)
  {
    uint 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;
  }

}

// File: contracts/QuantstampAuditData.sol

contract QuantstampAuditData is Whitelist {
  // state of audit requests submitted to the contract
  enum AuditState {
    None,
    Queued,
    Assigned,
    Refunded,
    Completed,  // automated audit finished successfully and the report is available
    Error,      // automated audit failed to finish; the report contains detailed information about the error
    Expired,
    Resolved
  }

  // structure representing an audit
  struct Audit {
    address requestor;
    string contractUri;
    uint256 price;
    uint256 requestBlockNumber; // block number that audit was requested
    QuantstampAuditData.AuditState state;
    address auditor;       // the address of the node assigned to the audit
    uint256 assignBlockNumber;  // block number that audit was assigned
    string reportHash;     // stores the hash of audit report
    uint256 reportBlockNumber;  // block number that the payment and the audit report were submitted
    address registrar;  // address of the contract which registers this request
  }

  // map audits (requestId, Audit)
  mapping(uint256 => Audit) public audits;

  // token used to pay for audits. This contract assumes that the owner of the contract trusts token's code and
  // that transfer function (such as transferFrom, transfer) do the right thing
  StandardToken public token;

  // Once an audit node gets an audit request, they must submit a report within this many blocks.
  // After that, the report is verified by the police.
  uint256 public auditTimeoutInBlocks = 50;

  // maximum number of assigned audits per each audit node
  uint256 public maxAssignedRequests = 10;

  // map audit nodes to their minimum prices. Defaults to zero: the node accepts all requests.
  mapping(address => uint256) public minAuditPrice;

  // For generating requestIds starting from 1
  uint256 private requestCounter;

  /**
   * @dev The constructor creates an audit contract.
   * @param tokenAddress The address of a StandardToken that will be used to pay audit nodes.
   */
  constructor (address tokenAddress) public {
    require(tokenAddress != address(0));
    token = StandardToken(tokenAddress);
  }

  function addAuditRequest (address requestor, string contractUri, uint256 price) public onlyWhitelisted returns(uint256) {
    // assign the next request ID
    uint256 requestId = ++requestCounter;
    // store the audit
    audits[requestId] = Audit(requestor, contractUri, price, block.number, AuditState.Queued, address(0), 0, "", 0, msg.sender);  // solhint-disable-line not-rely-on-time
    return requestId;
  }

  /**
   * @dev Allows a whitelisted logic contract (QuantstampAudit) to spend stored tokens.
   * @param amount The number of wei-QSP that will be approved.
   */
  function approveWhitelisted(uint256 amount) public onlyWhitelisted {
    token.approve(msg.sender, amount);
  }

  function getAuditContractUri(uint256 requestId) public view returns(string) {
    return audits[requestId].contractUri;
  }

  function getAuditRequestor(uint256 requestId) public view returns(address) {
    return audits[requestId].requestor;
  }

  function getAuditPrice (uint256 requestId) public view returns(uint256) {
    return audits[requestId].price;
  }

  function getAuditState (uint256 requestId) public view returns(AuditState) {
    return audits[requestId].state;
  }

  function getAuditRequestBlockNumber (uint256 requestId) public view returns(uint) {
    return audits[requestId].requestBlockNumber;
  }

  function setAuditState (uint256 requestId, AuditState state) public onlyWhitelisted {
    audits[requestId].state = state;
  }

  function getAuditAuditor (uint256 requestId) public view returns(address) {
    return audits[requestId].auditor;
  }

  function getAuditRegistrar (uint256 requestId) public view returns(address) {
    return audits[requestId].registrar;
  }

  function setAuditAuditor (uint256 requestId, address auditor) public onlyWhitelisted {
    audits[requestId].auditor = auditor;
  }

  function getAuditAssignBlockNumber (uint256 requestId) public view returns(uint256) {
    return audits[requestId].assignBlockNumber;
  }

  function getAuditReportBlockNumber (uint256 requestId) public view returns (uint256) {
    return audits[requestId].reportBlockNumber;
  }

  function setAuditAssignBlockNumber (uint256 requestId, uint256 assignBlockNumber) public onlyWhitelisted {
    audits[requestId].assignBlockNumber = assignBlockNumber;
  }

  function setAuditReportHash (uint256 requestId, string reportHash) public onlyWhitelisted {
    audits[requestId].reportHash = reportHash;
  }

  function setAuditReportBlockNumber (uint256 requestId, uint256 reportBlockNumber) public onlyWhitelisted {
    audits[requestId].reportBlockNumber = reportBlockNumber;
  }

  function setAuditRegistrar (uint256 requestId, address registrar) public onlyWhitelisted {
    audits[requestId].registrar = registrar;
  }

  function setAuditTimeout (uint256 timeoutInBlocks) public onlyOwner {
    auditTimeoutInBlocks = timeoutInBlocks;
  }

  /**
   * @dev Set the maximum number of audits any audit node can handle at any time.
   * @param maxAssignments Maximum number of audit requests for each audit node.
   */
  function setMaxAssignedRequests (uint256 maxAssignments) public onlyOwner {
    maxAssignedRequests = maxAssignments;
  }

  function getMinAuditPrice (address auditor) public view returns(uint256) {
    return minAuditPrice[auditor];
  }

  /**
   * @dev Allows the audit node to set its minimum price per audit in wei-QSP.
   * @param price The minimum price.
   */
  function setMinAuditPrice(address auditor, uint256 price) public onlyWhitelisted {
    minAuditPrice[auditor] = price;
  }
}

// File: openzeppelin-solidity/contracts/token/ERC20/SafeERC20.sol

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure.
 * To use this library you can add a `using SafeERC20 for ERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
  function safeTransfer(ERC20Basic token, address to, uint256 value) internal {
    require(token.transfer(to, value));
  }

  function safeTransferFrom(
    ERC20 token,
    address from,
    address to,
    uint256 value
  )
    internal
  {
    require(token.transferFrom(from, to, value));
  }

  function safeApprove(ERC20 token, address spender, uint256 value) internal {
    require(token.approve(spender, value));
  }
}

// File: contracts/token_escrow/TokenEscrow.sol

/**
 * NOTE: All contracts in this directory were taken from a non-master branch of openzeppelin-solidity.
 * This contract was modified to be a whitelist.
 * Commit: ed451a8688d1fa7c927b27cec299a9726667d9b1
 */

pragma solidity ^0.4.24;






/**
 * @title TokenEscrow
 * @dev Holds tokens destinated to a payee until they withdraw them.
 * The contract that uses the TokenEscrow as its payment method
 * should be its owner, and provide public methods redirecting
 * to the TokenEscrow's deposit and withdraw.
 * Moreover, the TokenEscrow should also be allowed to transfer
 * tokens from the payer to itself.
 */
contract TokenEscrow is Ownable, Whitelist {
  using SafeMath for uint256;
  using SafeERC20 for ERC20;

  event Deposited(address indexed payee, uint256 tokenAmount);
  event Withdrawn(address indexed payee, uint256 tokenAmount);

  mapping(address => uint256) public deposits;

  ERC20 public token;

  constructor (ERC20 _token) public {
    require(_token != address(0));
    token = _token;
  }

  function depositsOf(address _payee) public view returns (uint256) {
    return deposits[_payee];
  }

  /**
  * @dev Puts in escrow a certain amount of tokens as credit to be withdrawn.
  * @param _payee The destination address of the tokens.
  * @param _amount The amount of tokens to deposit in escrow.
  */
  function deposit(address _payee, uint256 _amount) public onlyWhitelisted {
    deposits[_payee] = deposits[_payee].add(_amount);

    token.safeTransferFrom(msg.sender, address(this), _amount);

    emit Deposited(_payee, _amount);
  }

  /**
  * @dev Withdraw accumulated tokens for a payee.
  * @param _payee The address whose tokens will be withdrawn and transferred to.
  */
  function withdraw(address _payee) public onlyWhitelisted {
    uint256 payment = deposits[_payee];
    assert(token.balanceOf(address(this)) >= payment);

    deposits[_payee] = 0;

    token.safeTransfer(_payee, payment);

    emit Withdrawn(_payee, payment);
  }
}

// File: contracts/token_escrow/ConditionalTokenEscrow.sol

/**
 * NOTE: All contracts in this directory were taken from a non-master branch of openzeppelin-solidity.
 * Commit: ed451a8688d1fa7c927b27cec299a9726667d9b1
 */

pragma solidity ^0.4.24;



/**
 * @title ConditionalTokenEscrow
 * @dev Base abstract escrow to only allow withdrawal of tokens
 * if a condition is met.
 */
contract ConditionalTokenEscrow is TokenEscrow {
  /**
  * @dev Returns whether an address is allowed to withdraw their tokens.
  * To be implemented by derived contracts.
  * @param _payee The destination address of the tokens.
  */
  function withdrawalAllowed(address _payee) public view returns (bool);

  function withdraw(address _payee) public {
    require(withdrawalAllowed(_payee));
    super.withdraw(_payee);
  }
}

// File: contracts/QuantstampAuditTokenEscrow.sol

contract QuantstampAuditTokenEscrow is ConditionalTokenEscrow {

  // the escrow maintains the list of staked addresses
  using LinkedListLib for LinkedListLib.LinkedList;

  // constants used by LinkedListLib
  uint256 constant internal NULL = 0;
  uint256 constant internal HEAD = 0;
  bool constant internal PREV = false;
  bool constant internal NEXT = true;

  // maintain the number of staked nodes
  // saves gas cost over needing to call stakedNodesList.sizeOf()
  uint256 public stakedNodesCount = 0;

  // the minimum amount of wei-QSP that must be staked in order to be a node
  uint256 public minAuditStake = 10000 * (10 ** 18);

  // if true, the payee cannot currently withdraw their funds
  mapping(address => bool) public lockedFunds;

  // if funds are locked, they may be retrieved after this block
  // if funds are unlocked, the number should be ignored
  mapping(address => uint256) public unlockBlockNumber;

  // staked audit nodes -- needed to inquire about audit node statistics, such as min price
  // this list contains all nodes that have *ANY* stake, however when getNextStakedNode is called,
  // it skips nodes that do not meet the minimum stake.
  // the reason for this approach is that if the owner lowers the minAuditStake,
  // we must be aware of any node with a stake.
  LinkedListLib.LinkedList internal stakedNodesList;

  event Slashed(address addr, uint256 amount);
  event StakedNodeAdded(address addr);
  event StakedNodeRemoved(address addr);

  // the constructor of TokenEscrow requires an ERC20, not an address
  constructor(address tokenAddress) public TokenEscrow(ERC20(tokenAddress)) {} // solhint-disable no-empty-blocks

  /**
  * @dev Puts in escrow a certain amount of tokens as credit to be withdrawn.
  *      Overrides the function in TokenEscrow.sol to add the payee to the staked list.
  * @param _payee The destination address of the tokens.
  * @param _amount The amount of tokens to deposit in escrow.
  */
  function deposit(address _payee, uint256 _amount) public onlyWhitelisted {
    super.deposit(_payee, _amount);
    if (_amount > 0) {
      // fails gracefully if the node already exists
      addNodeToStakedList(_payee);
    }
  }

 /**
  * @dev Withdraw accumulated tokens for a payee.
  *      Overrides the function in TokenEscrow.sol to remove the payee from the staked list.
  * @param _payee The address whose tokens will be withdrawn and transferred to.
  */
  function withdraw(address _payee) public onlyWhitelisted {
    super.withdraw(_payee);
    removeNodeFromStakedList(_payee);
  }

  /**
   * @dev Sets the minimum stake to a new value.
   * @param _value The new value. _value must be greater than zero in order for the linked list to be maintained correctly.
   */
  function setMinAuditStake(uint256 _value) public onlyOwner {
    require(_value > 0);
    minAuditStake = _value;
  }

  /**
   * @dev Returns true if the sender staked enough.
   * @param addr The address to check.
   */
  function hasEnoughStake(address addr) public view returns(bool) {
    return depositsOf(addr) >= minAuditStake;
  }

  /**
   * @dev Overrides ConditionalTokenEscrow function. If true, funds may be withdrawn.
   * @param _payee The address that wants to withdraw funds.
   */
  function withdrawalAllowed(address _payee) public view returns (bool) {
    return !lockedFunds[_payee] || unlockBlockNumber[_payee] < block.number;
  }

  /**
   * @dev Prevents the payee from withdrawing funds.
   * @param _payee The address that will be locked.
   */
  function lockFunds(address _payee, uint256 _unlockBlockNumber) public onlyWhitelisted returns (bool) {
    lockedFunds[_payee] = true;
    unlockBlockNumber[_payee] = _unlockBlockNumber;
    return true;
  }

    /**
   * @dev Slash a percentage of the stake of an address.
   *      The percentage is taken from the minAuditStake, not the total stake of the address.
   *      The caller of this function receives the slashed QSP.
   *      If the current stake does not cover the slash amount, the full stake is taken.
   *
   * @param addr The address that will be slashed.
   * @param percentage The percent of the minAuditStake that should be slashed.
   */
  function slash(address addr, uint256 percentage) public onlyWhitelisted returns (uint256) {
    require(0 <= percentage && percentage <= 100);

    uint256 slashAmount = getSlashAmount(percentage);
    uint256 balance = depositsOf(addr);
    if (balance < slashAmount) {
      slashAmount = balance;
    }

    // subtract from the deposits amount of the addr
    deposits[addr] = deposits[addr].sub(slashAmount);

    emit Slashed(addr, slashAmount);

    // if the deposits of the address are now zero, remove from the list
    if (depositsOf(addr) == 0) {
      removeNodeFromStakedList(addr);
    }

    // transfer the slashAmount to the police contract
    token.safeTransfer(msg.sender, slashAmount);

    return slashAmount;
  }

  /**
   * @dev Returns the slash amount for a given percentage.
   * @param percentage The percent of the minAuditStake that should be slashed.
   */
  function getSlashAmount(uint256 percentage) public view returns (uint256) {
    return (minAuditStake.mul(percentage)).div(100);
  }

  /**
   * @dev Given a staked address, returns the next address from the list that meets the minAuditStake.
   * @param addr The staked address.
   * @return The next address in the list.
   */
  function getNextStakedNode(address addr) public view returns(address) {
    bool exists;
    uint256 next;
    (exists, next) = stakedNodesList.getAdjacent(uint256(addr), NEXT);
    // only return addresses that meet the minAuditStake
    while (exists && next != HEAD && !hasEnoughStake(address(next))) {
      (exists, next) = stakedNodesList.getAdjacent(next, NEXT);
    }
    return address(next);
  }

  /**
   * @dev Adds an address to the stakedNodesList.
   * @param addr The address to be added to the list.
   * @return true if the address was added to the list.
   */
  function addNodeToStakedList(address addr) internal returns(bool success) {
    if (stakedNodesList.insert(HEAD, uint256(addr), PREV)) {
      stakedNodesCount++;
      emit StakedNodeAdded(addr);
      success = true;
    }
  }

  /**
   * @dev Removes an address from the stakedNodesList.
   * @param addr The address to be removed from the list.
   * @return true if the address was removed from the list.
   */
  function removeNodeFromStakedList(address addr) internal returns(bool success) {
    if (stakedNodesList.remove(uint256(addr)) != 0) {
      stakedNodesCount--;
      emit StakedNodeRemoved(addr);
      success = true;
    }
  }
}

// File: contracts/QuantstampAuditPolice.sol

// TODO (QSP-833): salary and taxing
// TODO transfer existing salary if removing police
contract QuantstampAuditPolice is Whitelist {   // solhint-disable max-states-count

  using SafeMath for uint256;
  using LinkedListLib for LinkedListLib.LinkedList;

  // constants used by LinkedListLib
  uint256 constant internal NULL = 0;
  uint256 constant internal HEAD = 0;
  bool constant internal PREV = false;
  bool constant internal NEXT = true;

  enum PoliceReportState {
    UNVERIFIED,
    INVALID,
    VALID,
    EXPIRED
  }

  // whitelisted police nodes
  LinkedListLib.LinkedList internal policeList;

  // the total number of police nodes
  uint256 public numPoliceNodes = 0;

  // the number of police nodes assigned to each report
  uint256 public policeNodesPerReport = 3;

  // the number of blocks the police have to verify a report
  uint256 public policeTimeoutInBlocks = 100;

  // number from [0-100] that indicates the percentage of the minAuditStake that should be slashed
  uint256 public slashPercentage = 20;

    // this is only deducted once per report, regardless of the number of police nodes assigned to it
  uint256 public reportProcessingFeePercentage = 5;

  event PoliceNodeAdded(address addr);
  event PoliceNodeRemoved(address addr);
  // TODO: we may want these parameters indexed
  event PoliceNodeAssignedToReport(address policeNode, uint256 requestId);
  event PoliceSubmissionPeriodExceeded(uint256 requestId, uint256 timeoutBlock, uint256 currentBlock);
  event PoliceSlash(uint256 requestId, address policeNode, address auditNode, uint256 amount);
  event PoliceFeesClaimed(address policeNode, uint256 fee);
  event PoliceFeesCollected(uint256 requestId, uint256 fee);
  event PoliceAssignmentExpiredAndCleared(uint256 requestId);

  // pointer to the police node that was last assigned to a report
  address private lastAssignedPoliceNode = address(HEAD);

  // maps each police node to the IDs of reports it should check
  mapping(address => LinkedListLib.LinkedList) internal assignedReports;

  // maps request IDs to the police nodes that are expected to check the report
  mapping(uint256 => LinkedListLib.LinkedList) internal assignedPolice;

  // maps each audit node to the IDs of reports that are pending police approval for payment
  mapping(address => LinkedListLib.LinkedList) internal pendingPayments;

  // maps request IDs to police timeouts
  mapping(uint256 => uint256) public policeTimeouts;

  // maps request IDs to reports submitted by police nodes
  mapping(uint256 => mapping(address => bytes)) public policeReports;

  // maps request IDs to the result reported by each police node
  mapping(uint256 => mapping(address => PoliceReportState)) public policeReportResults;

  // maps request IDs to whether they have been verified by the police
  mapping(uint256 => PoliceReportState) public verifiedReports;

  // maps request IDs to whether their reward has been claimed by the submitter
  mapping(uint256 => bool) public rewardHasBeenClaimed;

  // tracks the total number of reports ever assigned to a police node
  mapping(address => uint256) public totalReportsAssigned;

  // tracks the total number of reports ever checked by a police node
  mapping(address => uint256) public totalReportsChecked;

  // the collected fees for each report
  mapping(uint256 => uint256) public collectedFees;

  // contract that stores audit data (separate from the auditing logic)
  QuantstampAuditData public auditData;

  // contract that stores token escrows of nodes on the network
  QuantstampAuditTokenEscrow public tokenEscrow;

  /**
   * @dev The constructor creates a police contract.
   * @param auditDataAddress The address of an AuditData that stores data used for performing audits.
   * @param escrowAddress The address of a QuantstampTokenEscrow contract that holds staked deposits of nodes.
   */
  constructor (address auditDataAddress, address escrowAddress) public {
    require(auditDataAddress != address(0));
    require(escrowAddress != address(0));
    auditData = QuantstampAuditData(auditDataAddress);
    tokenEscrow = QuantstampAuditTokenEscrow(escrowAddress);
  }

  /**
   * @dev Assigns police nodes to a submitted report
   * @param requestId The ID of the audit request.
   */
  function assignPoliceToReport(uint256 requestId) public onlyWhitelisted {
    // ensure that the requestId has not already been assigned to police already
    require(policeTimeouts[requestId] == 0);
    // set the timeout for police reports
    policeTimeouts[requestId] = block.number + policeTimeoutInBlocks;
    // if there are not enough police nodes, this avoids assigning the same node twice
    uint256 numToAssign = policeNodesPerReport;
    if (numPoliceNodes < numToAssign) {
      numToAssign = numPoliceNodes;
    }
    while (numToAssign > 0) {
      lastAssignedPoliceNode = getNextPoliceNode(lastAssignedPoliceNode);
      if (lastAssignedPoliceNode != address(0)) {
        // push the request ID to the tail of the assignment list for the police node
        assignedReports[lastAssignedPoliceNode].push(requestId, PREV);
        // push the police node to the list of nodes assigned to check the report
        assignedPolice[requestId].push(uint256(lastAssignedPoliceNode), PREV);
        emit PoliceNodeAssignedToReport(lastAssignedPoliceNode, requestId);
        totalReportsAssigned[lastAssignedPoliceNode] = totalReportsAssigned[lastAssignedPoliceNode].add(1);
        numToAssign = numToAssign.sub(1);
      }
    }
  }

  /**
   * Cleans the list of assignments to police node (msg.sender), but checks only up to a limit
   * of assignments. If the limit is 0, attempts to clean the entire list.
   * @param policeNode The node whose assignments should be cleared.
   * @param limit The number of assigments to check.
   */
  function clearExpiredAssignments (address policeNode, uint256 limit) public {
    removeExpiredAssignments(policeNode, 0, limit);
  }

  /**
   * @dev Collects the police fee for checking a report.
   *      NOTE: this function assumes that the fee will be transferred by the calling contract.
   * @param requestId The ID of the audit request.
   * @return The amount collected.
   */
  function collectFee(uint256 requestId) public onlyWhitelisted returns (uint256) {
    uint256 policeFee = getPoliceFee(auditData.getAuditPrice(requestId));
    // the collected fee needs to be stored in a map since the owner could change the fee percentage
    collectedFees[requestId] = policeFee;
    emit PoliceFeesCollected(requestId, policeFee);
    return policeFee;
  }

  /**
   * @dev Split a payment, which may be for report checking or from slashing, amongst all police nodes
   * @param amount The amount to be split, which should have been transferred to this contract earlier.
   */
  function splitPayment(uint256 amount) public onlyWhitelisted {
    require(numPoliceNodes != 0);
    address policeNode = getNextPoliceNode(address(HEAD));
    uint256 amountPerNode = amount.div(numPoliceNodes);
    // TODO: upgrade our openzeppelin version to use mod
    uint256 largerAmount = amountPerNode.add(amount % numPoliceNodes);
    bool largerAmountClaimed = false;
    while (policeNode != address(HEAD)) {
      // give the largerAmount to the current lastAssignedPoliceNode if it is not equal to HEAD
      // this approach is only truly fair if numPoliceNodes and policeNodesPerReport are relatively prime
      // but the remainder should be extremely small in any case
      // the last conditional handles the edge case where all police nodes were removed and then re-added
      if (!largerAmountClaimed && (policeNode == lastAssignedPoliceNode || lastAssignedPoliceNode == address(HEAD))) {
        require(auditData.token().transfer(policeNode, largerAmount));
        emit PoliceFeesClaimed(policeNode, largerAmount);
        largerAmountClaimed = true;
      } else {
        require(auditData.token().transfer(policeNode, amountPerNode));
        emit PoliceFeesClaimed(policeNode, amountPerNode);
      }
      policeNode = getNextPoliceNode(address(policeNode));
    }
  }

  /**
   * @dev Associates a pending payment with an auditor that can be claimed after the policing period.
   * @param auditor The audit node that submitted the report.
   * @param requestId The ID of the audit request.
   */
  function addPendingPayment(address auditor, uint256 requestId) public onlyWhitelisted {
    pendingPayments[auditor].push(requestId, PREV);
  }

  /**
   * @dev Submits verification of a report by a police node.
   * @param policeNode The address of the police node.
   * @param auditNode The address of the audit node.
   * @param requestId The ID of the audit request.
   * @param report The compressed bytecode representation of the report.
   * @param isVerified Whether the police node's report matches the submitted report.
   *                   If not, the audit node is slashed.
   * @return two bools and a uint256: (true if the report was successfully submitted, true if a slash occurred, the slash amount).
   */
  function submitPoliceReport(
    address policeNode,
    address auditNode,
    uint256 requestId,
    bytes report,
    bool isVerified) public onlyWhitelisted returns (bool, bool, uint256) {
    // remove expired assignments
    bool hasRemovedCurrentId = removeExpiredAssignments(policeNode, requestId, 0);
    // if the current request has timed out, return
    if (hasRemovedCurrentId) {
      emit PoliceSubmissionPeriodExceeded(requestId, policeTimeouts[requestId], block.number);
      return (false, false, 0);
    }
    // the police node is assigned to the report
    require(isAssigned(requestId, policeNode));

    // remove the report from the assignments to the node
    assignedReports[policeNode].remove(requestId);
    // increment the number of reports checked by the police node
    totalReportsChecked[policeNode] = totalReportsChecked[policeNode] + 1;
    // store the report
    policeReports[requestId][policeNode] = report;
    // emit an event
    PoliceReportState state;
    if (isVerified) {
      state = PoliceReportState.VALID;
    } else {
      state = PoliceReportState.INVALID;
    }
    policeReportResults[requestId][policeNode] = state;

    // the report was already marked invalid by a different police node
    if (verifiedReports[requestId] == PoliceReportState.INVALID) {
      return (true, false, 0);
    } else {
      verifiedReports[requestId] = state;
    }
    bool slashOccurred;
    uint256 slashAmount;
    if (!isVerified) {
      pendingPayments[auditNode].remove(requestId);
      // an audit node can only be slashed once for each report,
      // even if multiple police mark the report as invalid
      slashAmount = tokenEscrow.slash(auditNode, slashPercentage);
      slashOccurred = true;
      emit PoliceSlash(requestId, policeNode, auditNode, slashAmount);
    }
    return (true, slashOccurred, slashAmount);
  }

  /**
   * @dev Determines whether an audit node is allowed by the police to claim an audit.
   * @param auditNode The address of the audit node.
   * @param requestId The ID of the requested audit.
   */
  function canClaimAuditReward (address auditNode, uint256 requestId) public view returns (bool) {
    // NOTE: can't use requires here, as claimNextReward needs to iterate the full list
    return
      // the report is in the pending payments list for the audit node
      pendingPayments[auditNode].nodeExists(requestId) &&
      // the policing period has ended for the report
      policeTimeouts[requestId] < block.number &&
      // the police did not invalidate the report
      verifiedReports[requestId] != PoliceReportState.INVALID &&
      // the reward has not already been claimed
      !rewardHasBeenClaimed[requestId] &&
      // the requestId is non-zero
      requestId > 0;
  }

  /**
   * @dev Given a requestId, returns the next pending available reward for the audit node.
   * @param auditNode The address of the audit node.
   * @param requestId The ID of the current linked list node
   * @return true if the next reward exists, and the corresponding requestId in the linked list
   */
  function getNextAvailableReward (address auditNode, uint256 requestId) public view returns (bool, uint256) {
    bool exists;
    (exists, requestId) = pendingPayments[auditNode].getAdjacent(requestId, NEXT);
    // NOTE: Do NOT short circuit this list based on timeouts.
    // The ordering may be broken if the owner changes the timeouts.
    while (exists && requestId != HEAD) {
      if (canClaimAuditReward(auditNode, requestId)) {
        return (true, requestId);
      }
      (exists, requestId) = pendingPayments[auditNode].getAdjacent(requestId, NEXT);
    }
    return (false, 0);
  }

  /**
   * @dev Sets the reward as claimed after checking that it can be claimed.
   *      This function also ensures double payment does not occur.
   * @param auditNode The address of the audit node.
   * @param requestId The ID of the requested audit.
   */
  function setRewardClaimed (address auditNode, uint256 requestId) public onlyWhitelisted returns (bool) {
    // set the reward to claimed, to avoid double payment
    rewardHasBeenClaimed[requestId] = true;
    pendingPayments[auditNode].remove(requestId);
    // if it is possible to claim yet the state is UNVERIFIED, mark EXPIRED
    if (verifiedReports[requestId] == PoliceReportState.UNVERIFIED) {
      verifiedReports[requestId] = PoliceReportState.EXPIRED;
    }
    return true;
  }

  /**
   * @dev Selects the next ID to be rewarded.
   * @param auditNode The address of the audit node.
   * @param requestId The previous claimed requestId (initially set to HEAD).
   * @return True if another reward exists, and the request ID.
   */
  function claimNextReward (address auditNode, uint256 requestId) public onlyWhitelisted returns (bool, uint256) {
    bool exists;
    (exists, requestId) = pendingPayments[auditNode].getAdjacent(requestId, NEXT);
    // NOTE: Do NOT short circuit this list based on timeouts.
    // The ordering may be broken if the owner changes the timeouts.
    while (exists && requestId != HEAD) {
      if (canClaimAuditReward(auditNode, requestId)) {
        setRewardClaimed(auditNode, requestId);
        return (true, requestId);
      }
      (exists, requestId) = pendingPayments[auditNode].getAdjacent(requestId, NEXT);
    }
    return (false, 0);
  }

  /**
   * @dev Gets the next assigned report to the police node.
   * @param policeNode The address of the police node.
   * @return true if the list is non-empty, requestId, auditPrice, uri, and policeAssignmentBlockNumber.
   */
  function getNextPoliceAssignment(address policeNode) public view returns (bool, uint256, uint256, string, uint256) {
    bool exists;
    uint256 requestId;
    (exists, requestId) = assignedReports[policeNode].getAdjacent(HEAD, NEXT);
    // if the head of the list is an expired assignment, try to find a current one
    while (exists && requestId != HEAD) {
      if (policeTimeouts[requestId] < block.number) {
        (exists, requestId) = assignedReports[policeNode].getAdjacent(requestId, NEXT);
      } else {
        uint256 price = auditData.getAuditPrice(requestId);
        string memory uri = auditData.getAuditContractUri(requestId);
        uint256 policeAssignmentBlockNumber = auditData.getAuditReportBlockNumber(requestId);
        return (exists, requestId, price, uri, policeAssignmentBlockNumber);
      }
    }
    return (false, 0, 0, "", 0);
  }

  /**
   * @dev Gets the next assigned police node to an audit request.
   * @param requestId The ID of the audit request.
   * @param policeNode The previous claimed requestId (initially set to HEAD).
   * @return true if the next police node exists, and the address of the police node.
   */
  function getNextAssignedPolice(uint256 requestId, address policeNode) public view returns (bool, address) {
    bool exists;
    uint256 nextPoliceNode;
    (exists, nextPoliceNode) = assignedPolice[requestId].getAdjacent(uint256(policeNode), NEXT);
    if (nextPoliceNode == HEAD) {
      return (false, address(0));
    }
    return (exists, address(nextPoliceNode));
  }

  /**
   * @dev Sets the number of police nodes that should check each report.
   * @param numPolice The number of police.
   */
  function setPoliceNodesPerReport(uint256 numPolice) public onlyOwner {
    policeNodesPerReport = numPolice;
  }

  /**
   * @dev Sets the police timeout.
   * @param numBlocks The number of blocks for the timeout.
   */
  function setPoliceTimeoutInBlocks(uint256 numBlocks) public onlyOwner {
    policeTimeoutInBlocks = numBlocks;
  }

  /**
   * @dev Sets the slash percentage.
   * @param percentage The percentage as an integer from [0-100].
   */
  function setSlashPercentage(uint256 percentage) public onlyOwner {
    require(0 <= percentage && percentage <= 100);
    slashPercentage = percentage;
  }

  /**
   * @dev Sets the report processing fee percentage.
   * @param percentage The percentage in the range of [0-100].
   */
  function setReportProcessingFeePercentage(uint256 percentage) public onlyOwner {
    require(percentage <= 100);
    reportProcessingFeePercentage = percentage;
  }

  /**
   * @dev Returns true if a node is whitelisted.
   * @param node The node to check.
   */
  function isPoliceNode(address node) public view returns (bool) {
    return policeList.nodeExists(uint256(node));
  }

  /**
   * @dev Adds an address to the police.
   * @param addr The address to be added.
   * @return true if the address was added to the whitelist.
   */
  function addPoliceNode(address addr) public onlyOwner returns (bool success) {
    if (policeList.insert(HEAD, uint256(addr), PREV)) {
      numPoliceNodes = numPoliceNodes.add(1);
      emit PoliceNodeAdded(addr);
      success = true;
    }
  }

  /**
   * @dev Removes an address from the whitelist linked-list.
   * @param addr The address to be removed.
   * @return true if the address was removed from the whitelist.
   */
  function removePoliceNode(address addr) public onlyOwner returns (bool success) {
    // if lastAssignedPoliceNode is addr, need to move the pointer
    bool exists;
    uint256 next;
    if (lastAssignedPoliceNode == addr) {
      (exists, next) = policeList.getAdjacent(uint256(addr), NEXT);
      lastAssignedPoliceNode = address(next);
    }

    if (policeList.remove(uint256(addr)) != NULL) {
      numPoliceNodes = numPoliceNodes.sub(1);
      emit PoliceNodeRemoved(addr);
      success = true;
    }
  }

  /**
   * @dev Given a whitelisted address, returns the next address from the whitelist.
   * @param addr The address in the whitelist.
   * @return The next address in the whitelist.
   */
  function getNextPoliceNode(address addr) public view returns (address) {
    bool exists;
    uint256 next;
    (exists, next) = policeList.getAdjacent(uint256(addr), NEXT);
    return address(next);
  }

  /**
   * @dev Returns the resulting state of a police report for a given audit request.
   * @param requestId The ID of the audit request.
   * @param policeAddr The address of the police node.
   * @return the PoliceReportState of the (requestId, policeNode) pair.
   */
  function getPoliceReportResult(uint256 requestId, address policeAddr) public view returns (PoliceReportState) {
    return policeReportResults[requestId][policeAddr];
  }

  function getPoliceReport(uint256 requestId, address policeAddr) public view returns (bytes) {
    return policeReports[requestId][policeAddr];
  }

  function getPoliceFee(uint256 auditPrice) public view returns (uint256) {
    return auditPrice.mul(reportProcessingFeePercentage).div(100);
  }

  function isAssigned(uint256 requestId, address policeAddr) public view returns (bool) {
    return assignedReports[policeAddr].nodeExists(requestId);
  }

  /**
   * Cleans the list of assignments to a given police node.
   * @param policeNode The address of the police node.
   * @param requestId The ID of the audit request.
   * @param limit The number of assigments to check. Use 0 if the entire list should be checked.
   * @return true if the current request ID gets removed during cleanup.
   */
  function removeExpiredAssignments (address policeNode, uint256 requestId, uint256 limit) internal returns (bool) {
    bool hasRemovedCurrentId = false;
    bool exists;
    uint256 potentialExpiredRequestId;
    uint256 nextExpiredRequestId;
    uint256 iterationsLeft = limit;
    (exists, nextExpiredRequestId) = assignedReports[policeNode].getAdjacent(HEAD, NEXT);
    // NOTE: Short circuiting this list may cause expired assignments to exist later in the list.
    //       The may occur if the owner changes the global police timeout.
    //       These expired assignments will be removed in subsequent calls.
    while (exists && nextExpiredRequestId != HEAD && (limit == 0 || iterationsLeft > 0)) {
      potentialExpiredRequestId = nextExpiredRequestId;
      (exists, nextExpiredRequestId) = assignedReports[policeNode].getAdjacent(nextExpiredRequestId, NEXT);
      if (policeTimeouts[potentialExpiredRequestId] < block.number) {
        assignedReports[policeNode].remove(potentialExpiredRequestId);
        emit PoliceAssignmentExpiredAndCleared(potentialExpiredRequestId);
        if (potentialExpiredRequestId == requestId) {
          hasRemovedCurrentId = true;
        }
      } else {
        break;
      }
      iterationsLeft -= 1;
    }
    return hasRemovedCurrentId;
  }
}

// File: contracts/QuantstampAuditReportData.sol

contract QuantstampAuditReportData is Whitelist {

  // mapping from requestId to a report
  mapping(uint256 => bytes) public reports;

  function setReport(uint256 requestId, bytes report) external onlyWhitelisted {
    reports[requestId] = report;
  }

  function getReport(uint256 requestId) external view returns(bytes) {
    return reports[requestId];
  }

}

// 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: contracts/QuantstampAudit.sol

contract QuantstampAudit is Pausable {
  using SafeMath for uint256;
  using LinkedListLib for LinkedListLib.LinkedList;

  // constants used by LinkedListLib
  uint256 constant internal NULL = 0;
  uint256 constant internal HEAD = 0;
  bool constant internal PREV = false;
  bool constant internal NEXT = true;

  uint256 private minAuditPriceLowerCap = 0;

  // mapping from an audit node address to the number of requests that it currently processes
  mapping(address => uint256) public assignedRequestCount;

  // increasingly sorted linked list of prices
  LinkedListLib.LinkedList internal priceList;
  // map from price to a list of request IDs
  mapping(uint256 => LinkedListLib.LinkedList) internal auditsByPrice;

  // list of request IDs of assigned audits (the list preserves temporal order of assignments)
  LinkedListLib.LinkedList internal assignedAudits;

  // stores request ids of the most recently assigned audits for each audit node
  mapping(address => uint256) public mostRecentAssignedRequestIdsPerAuditor;

  // contract that stores audit data (separate from the auditing logic)
  QuantstampAuditData public auditData;

  // contract that stores audit reports on-chain
  QuantstampAuditReportData public reportData;

  // contract that handles policing
  QuantstampAuditPolice public police;

  // contract that stores token escrows of nodes on the network
  QuantstampAuditTokenEscrow public tokenEscrow;

  event LogAuditFinished(
    uint256 requestId,
    address auditor,
    QuantstampAuditData.AuditState auditResult,
    bytes report
  );

  event LogPoliceAuditFinished(
    uint256 requestId,
    address policeNode,
    bytes report,
    bool isVerified
  );

  event LogAuditRequested(uint256 requestId,
    address requestor,
    string uri,
    uint256 price
  );

  event LogAuditAssigned(uint256 requestId,
    address auditor,
    address requestor,
    string uri,
    uint256 price,
    uint256 requestBlockNumber);

  /* solhint-disable event-name-camelcase */
  event LogReportSubmissionError_InvalidAuditor(uint256 requestId, address auditor);
  event LogReportSubmissionError_InvalidState(uint256 requestId, address auditor, QuantstampAuditData.AuditState state);
  event LogReportSubmissionError_InvalidResult(uint256 requestId, address auditor, QuantstampAuditData.AuditState state);
  event LogReportSubmissionError_ExpiredAudit(uint256 requestId, address auditor, uint256 allowanceBlockNumber);
  event LogAuditAssignmentError_ExceededMaxAssignedRequests(address auditor);
  event LogAuditAssignmentError_Understaked(address auditor, uint256 stake);
  event LogAuditAssignmentUpdate_Expired(uint256 requestId, uint256 allowanceBlockNumber);
  event LogClaimRewardsReachedGasLimit(address auditor);

  /* solhint-enable event-name-camelcase */

  event LogAuditQueueIsEmpty();

  event LogPayAuditor(uint256 requestId, address auditor, uint256 amount);
  event LogAuditNodePriceChanged(address auditor, uint256 amount);

  event LogRefund(uint256 requestId, address requestor, uint256 amount);
  event LogRefundInvalidRequestor(uint256 requestId, address requestor);
  event LogRefundInvalidState(uint256 requestId, QuantstampAuditData.AuditState state);
  event LogRefundInvalidFundsLocked(uint256 requestId, uint256 currentBlock, uint256 fundLockEndBlock);

  // the audit queue has elements, but none satisfy the minPrice of the audit node
  // amount corresponds to the current minPrice of the audit node
  event LogAuditNodePriceHigherThanRequests(address auditor, uint256 amount);

  enum AuditAvailabilityState {
    Error,
    Ready,      // an audit is available to be picked up
    Empty,      // there is no audit request in the queue
    Exceeded,   // number of incomplete audit requests is reached the cap
    Underpriced, // all queued audit requests are less than the expected price
    Understaked // the audit node's stake is not large enough to request its min price
  }

  /**
   * @dev The constructor creates an audit contract.
   * @param auditDataAddress The address of an AuditData that stores data used for performing audits.
   * @param reportDataAddress The address of a ReportData that stores audit reports.
   * @param escrowAddress The address of a QuantstampTokenEscrow contract that holds staked deposits of nodes.
   * @param policeAddress The address of a QuantstampAuditPolice that performs report checking.
   */
  constructor (address auditDataAddress, address reportDataAddress, address escrowAddress, address policeAddress) public {
    require(auditDataAddress != address(0));
    require(reportDataAddress != address(0));
    require(escrowAddress != address(0));
    require(policeAddress != address(0));
    auditData = QuantstampAuditData(auditDataAddress);
    reportData = QuantstampAuditReportData(reportDataAddress);
    tokenEscrow = QuantstampAuditTokenEscrow(escrowAddress);
    police = QuantstampAuditPolice(policeAddress);
  }

  /**
   * @dev Allows contract owner to set the lower cap the min audit price.
   * @param amount The amount of wei-QSP.
   */
  function setMinAuditPriceLowerCap(uint256 amount) external onlyOwner {
    minAuditPriceLowerCap = amount;
  }

  /**
   * @dev Allows nodes to stake a deposit. The audit node must approve QuantstampAudit before invoking.
   * @param amount The amount of wei-QSP to deposit.
   */
  function stake(uint256 amount) external returns(bool) {
    // first acquire the tokens approved by the audit node
    require(auditData.token().transferFrom(msg.sender, address(this), amount));
    // use those tokens to approve a transfer in the escrow
    auditData.token().approve(address(tokenEscrow), amount);
    // a "Deposited" event is emitted in TokenEscrow
    tokenEscrow.deposit(msg.sender, amount);
    return true;
  }

  /**
   * @dev Allows audit nodes to retrieve a deposit.
   */
  function unstake() external returns(bool) {
    // the escrow contract ensures that the deposit is not currently locked
    tokenEscrow.withdraw(msg.sender);
    return true;
  }

  /**
   * @dev Returns funds to the requestor.
   * @param requestId Unique ID of the audit request.
   */
  function refund(uint256 requestId) external returns(bool) {
    QuantstampAuditData.AuditState state = auditData.getAuditState(requestId);
    // check that the audit exists and is in a valid state
    if (state != QuantstampAuditData.AuditState.Queued &&
          state != QuantstampAuditData.AuditState.Assigned &&
            state != QuantstampAuditData.AuditState.Expired) {
      emit LogRefundInvalidState(requestId, state);
      return false;
    }
    address requestor = auditData.getAuditRequestor(requestId);
    if (requestor != msg.sender) {
      emit LogRefundInvalidRequestor(requestId, msg.sender);
      return;
    }
    uint256 refundBlockNumber = auditData.getAuditAssignBlockNumber(requestId).add(auditData.auditTimeoutInBlocks());
    // check that the audit node has not recently started the audit (locking the funds)
    if (state == QuantstampAuditData.AuditState.Assigned) {
      if (block.number <= refundBlockNumber) {
        emit LogRefundInvalidFundsLocked(requestId, block.number, refundBlockNumber);
        return false;
      }
      // the request is expired but not detected by getNextAuditRequest
      updateAssignedAudits(requestId);
    } else if (state == QuantstampAuditData.AuditState.Queued) {
      // remove the request from the queue
      // note that if an audit node is currently assigned the request, it is already removed from the queue
      removeQueueElement(requestId);
    }

    // set the audit state to refunded
    auditData.setAuditState(requestId, QuantstampAuditData.AuditState.Refunded);

    // return the funds to the requestor
    uint256 price = auditData.getAuditPrice(requestId);
    emit LogRefund(requestId, requestor, price);
    safeTransferFromDataContract(requestor, price);
    return true;
  }

  /**
   * @dev Submits audit request.
   * @param contractUri Identifier of the resource to audit.
   * @param price The total amount of tokens that will be paid for the audit.
   */
  function requestAudit(string contractUri, uint256 price) public returns(uint256) {
    // it passes HEAD as the existing price, therefore may result in extra gas needed for list iteration
    return requestAuditWithPriceHint(contractUri, price, HEAD);
  }

  /**
   * @dev Submits audit request.
   * @param contractUri Identifier of the resource to audit.
   * @param price The total amount of tokens that will be paid for the audit.
   * @param existingPrice Existing price in the list (price hint allows for optimization that can make insertion O(1)).
   */
  function requestAuditWithPriceHint(string contractUri, uint256 price, uint256 existingPrice) public whenNotPaused returns(uint256) {
    require(price > 0);
    require(price >= minAuditPriceLowerCap);

    // transfer tokens to the data contract
    require(auditData.token().transferFrom(msg.sender, address(auditData), price));
    // store the audit
    uint256 requestId = auditData.addAuditRequest(msg.sender, contractUri, price);

    queueAuditRequest(requestId, existingPrice);

    emit LogAuditRequested(requestId, msg.sender, contractUri, price); // solhint-disable-line not-rely-on-time

    return requestId;
  }

  /**
   * @dev Submits the report and pays the audit node for their work if the audit is completed.
   * @param requestId Unique identifier of the audit request.
   * @param auditResult Result of an audit.
   * @param report a compressed report. TODO, let's document the report format.
   */
  function submitReport(uint256 requestId, QuantstampAuditData.AuditState auditResult, bytes report) public { // solhint-disable-line function-max-lines
    if (QuantstampAuditData.AuditState.Completed != auditResult && QuantstampAuditData.AuditState.Error != auditResult) {
      emit LogReportSubmissionError_InvalidResult(requestId, msg.sender, auditResult);
      return;
    }

    QuantstampAuditData.AuditState auditState = auditData.getAuditState(requestId);
    if (auditState != QuantstampAuditData.AuditState.Assigned) {
      emit LogReportSubmissionError_InvalidState(requestId, msg.sender, auditState);
      return;
    }

    // the sender must be the audit node
    if (msg.sender != auditData.getAuditAuditor(requestId)) {
      emit LogReportSubmissionError_InvalidAuditor(requestId, msg.sender);
      return;
    }

    // remove the requestId from assigned queue
    updateAssignedAudits(requestId);

    // the audit node should not send a report after its allowed period
    uint256 allowanceBlockNumber = auditData.getAuditAssignBlockNumber(requestId) + auditData.auditTimeoutInBlocks();
    if (allowanceBlockNumber < block.number) {
      // update assigned to expired state
      auditData.setAuditState(requestId, QuantstampAuditData.AuditState.Expired);
      emit LogReportSubmissionError_ExpiredAudit(requestId, msg.sender, allowanceBlockNumber);
      return;
    }

    // update the audit information held in this contract
    auditData.setAuditState(requestId, auditResult);
    auditData.setAuditReportBlockNumber(requestId, block.number); // solhint-disable-line not-rely-on-time

    // validate the audit state
    require(isAuditFinished(requestId));

    // store reports on-chain
    reportData.setReport(requestId, report);

    emit LogAuditFinished(requestId, msg.sender, auditResult, report);

    // alert the police to verify the report
    police.assignPoliceToReport(requestId);
    // add the requestId to the pending payments that should be paid to the audit node after policing
    police.addPendingPayment(msg.sender, requestId);
    // pay fee to the police
    if (police.reportProcessingFeePercentage() > 0 && police.numPoliceNodes() > 0) {
      uint256 policeFee = police.collectFee(requestId);
      safeTransferFromDataContract(address(police), policeFee);
      police.splitPayment(policeFee);
    }
  }

  /**
   * @dev Returns the compressed report submitted by the audit node.
   * @param requestId The ID of the audit request.
   */
  function getReport(uint256 requestId) public view returns (bytes) {
    return reportData.getReport(requestId);
  }

  /**
   * @dev Checks whether a given node is a police.
   * @param node The address of the node to be checked.
   * @return true if the target address is a police node.
   */
  function isPoliceNode(address node) public view returns(bool) {
    return police.isPoliceNode(node);
  }

  /**
   * @dev Submits verification of a report by a police node.
   * @param requestId The ID of the audit request.
   * @param report The compressed bytecode representation of the report.
   * @param isVerified Whether the police node's report matches the submitted report.
   *                   If not, the audit node is slashed.
   * @return true if the report was submitted successfully.
   */
  function submitPoliceReport(
    uint256 requestId,
    bytes report,
    bool isVerified) public returns (bool) {
    require(police.isPoliceNode(msg.sender));
    // get the address of the audit node
    address auditNode = auditData.getAuditAuditor(requestId);
    bool hasBeenSubmitted;
    bool slashOccurred;
    uint256 slashAmount;
    // hasBeenSubmitted may be false if the police submission period has ended
    (hasBeenSubmitted, slashOccurred, slashAmount) = police.submitPoliceReport(msg.sender, auditNode, requestId, report, isVerified);
    if (hasBeenSubmitted) {
      emit LogPoliceAuditFinished(requestId, msg.sender, report, isVerified);
    }
    if (slashOccurred) {
      // transfer the audit request price to the police
      uint256 auditPoliceFee = police.collectedFees(requestId);
      uint256 adjustedPrice = auditData.getAuditPrice(requestId).sub(auditPoliceFee);
      safeTransferFromDataContract(address(police), adjustedPrice);

      // divide the adjusted price + slash among police assigned to report
      police.splitPayment(adjustedPrice.add(slashAmount));
    }
    return hasBeenSubmitted;
  }

  /**
   * @dev Determines whether the address (of an audit node) can claim any audit rewards.
   */
  function hasAvailableRewards () public view returns (bool) {
    bool exists;
    uint256 next;
    (exists, next) = police.getNextAvailableReward(msg.sender, HEAD);
    return exists;
  }

  /**
   * @dev Returns the minimum price nodes could set
   */
  function getMinAuditPriceLowerCap() public view returns(uint256) {
    return minAuditPriceLowerCap;
  }

  /**
   * @dev Given a requestId, returns the next pending available reward for the audit node.
   *      This can be used in conjunction with claimReward() if claimRewards fails due to gas limits.
   * @param requestId The ID of the current linked list node
   * @return true if the next reward exists, and the corresponding requestId in the linked list
   */
  function getNextAvailableReward (uint256 requestId) public view returns(bool, uint256) {
    return police.getNextAvailableReward(msg.sender, requestId);
  }

  /**
   * @dev If the policing period has ended without the report being marked invalid,
   *      allow the audit node to claim the audit's reward.
   * @param requestId The ID of the audit request.
   * NOTE: We need this function if claimRewards always fails due to gas limits.
   *       I think this can only happen if the audit node receives many (i.e., hundreds) of audits,
   *       and never calls claimRewards() until much later.
   */
  function claimReward (uint256 requestId) public returns (bool) {
    require(police.canClaimAuditReward(msg.sender, requestId));
    police.setRewardClaimed(msg.sender, requestId);
    transferReward(requestId);
    return true;
  }

  /**
   * @dev Claim all pending rewards for the audit node.
   * @return Returns true if the operation ran to completion, or false if the loop exits due to gas limits.
   */
  function claimRewards () public returns (bool) {
    // Yet another list iteration. Could ignore this check, but makes testing painful.
    require(hasAvailableRewards());
    bool exists;
    uint256 requestId = HEAD;
    uint256 remainingGasBeforeCall;
    uint256 remainingGasAfterCall;
    bool loopExitedDueToGasLimit;
    // This loop occurs here (not in QuantstampAuditPolice) due to requiring the audit price,
    // as otherwise we require more dependencies/mappings in QuantstampAuditPolice.
    while (true) {
      remainingGasBeforeCall = gasleft();
      (exists, requestId) = police.claimNextReward(msg.sender, HEAD);
      if (!exists) {
        break;
      }
      transferReward(requestId);
      remainingGasAfterCall = gasleft();
      // multiplying by 2 to leave a bit of extra leeway, particularly due to the while-loop in claimNextReward
      if (remainingGasAfterCall < remainingGasBeforeCall.sub(remainingGasAfterCall).mul(2)) {
        loopExitedDueToGasLimit = true;
        emit LogClaimRewardsReachedGasLimit(msg.sender);
        break;
      }
    }
    return loopExitedDueToGasLimit;
  }

  /**
   * @dev Returns the total stake deposited by an address.
   * @param addr The address to check.
   */
  function totalStakedFor(address addr) public view returns(uint256) {
    return tokenEscrow.depositsOf(addr);
  }

  /**
   * @dev Returns true if the sender staked enough.
   * @param addr The address to check.
   */
  function hasEnoughStake(address addr) public view returns(bool) {
    return tokenEscrow.hasEnoughStake(addr);
  }

  /**
   * @dev Returns the minimum stake required to be an audit node.
   */
  function getMinAuditStake() public view returns(uint256) {
    return tokenEscrow.minAuditStake();
  }

  /**
   *  @dev Returns the timeout time (in blocks) for any given audit.
   */
  function getAuditTimeoutInBlocks() public view returns(uint256) {
    return auditData.auditTimeoutInBlocks();
  }

  /**
   *  @dev Returns the minimum price for a specific audit node.
   */
  function getMinAuditPrice (address auditor) public view returns(uint256) {
    return auditData.getMinAuditPrice(auditor);
  }

  /**
   * @dev Returns the maximum number of assigned audits for any given audit node.
   */
  function getMaxAssignedRequests() public view returns(uint256) {
    return auditData.maxAssignedRequests();
  }

  /**
   * @dev Determines if there is an audit request available to be picked up by the caller.
   */
  function anyRequestAvailable() public view returns(AuditAvailabilityState) {
    uint256 requestId;

    // check that the audit node's stake is large enough
    if (!hasEnoughStake(msg.sender)) {
      return AuditAvailabilityState.Understaked;
    }

    // there are no audits in the queue
    if (!auditQueueExists()) {
      return AuditAvailabilityState.Empty;
    }

    // check if the audit node's assignment count is not exceeded
    if (assignedRequestCount[msg.sender] >= auditData.maxAssignedRequests()) {
      return AuditAvailabilityState.Exceeded;
    }

    requestId = anyAuditRequestMatchesPrice(auditData.getMinAuditPrice(msg.sender));
    if (requestId == 0) {
      return AuditAvailabilityState.Underpriced;
    }
    return AuditAvailabilityState.Ready;
  }

  /**
   * @dev Returns the next assigned report in a police node's assignment queue.
   * @return true if the list is non-empty, requestId, auditPrice, uri, and policeAssignmentBlockNumber.
   */
  function getNextPoliceAssignment() public view returns (bool, uint256, uint256, string, uint256) {
    return police.getNextPoliceAssignment(msg.sender);
  }

  /**
   * @dev Finds a list of most expensive audits and assigns the oldest one to the audit node.
   */
  /* solhint-disable function-max-lines */
  function getNextAuditRequest() public {
    // remove an expired audit request
    if (assignedAudits.listExists()) {
      bool exists;
      uint256 potentialExpiredRequestId;
      (exists, potentialExpiredRequestId) = assignedAudits.getAdjacent(HEAD, NEXT);
      uint256 allowanceBlockNumber = auditData.getAuditAssignBlockNumber(potentialExpiredRequestId) + auditData.auditTimeoutInBlocks();
      if (allowanceBlockNumber < block.number) {
        updateAssignedAudits(potentialExpiredRequestId);
        auditData.setAuditState(potentialExpiredRequestId, QuantstampAuditData.AuditState.Expired);
        emit LogAuditAssignmentUpdate_Expired(potentialExpiredRequestId, allowanceBlockNumber);
      }
    }

    AuditAvailabilityState isRequestAvailable = anyRequestAvailable();
    // there are no audits in the queue
    if (isRequestAvailable == AuditAvailabilityState.Empty) {
      emit LogAuditQueueIsEmpty();
      return;
    }

    // check if the audit node's assignment is not exceeded
    if (isRequestAvailable == AuditAvailabilityState.Exceeded) {
      emit LogAuditAssignmentError_ExceededMaxAssignedRequests(msg.sender);
      return;
    }

    uint256 minPrice = auditData.getMinAuditPrice(msg.sender);
    require(minPrice >= minAuditPriceLowerCap);

    // check that the audit node has staked enough QSP
    if (isRequestAvailable == AuditAvailabilityState.Understaked) {
      emit LogAuditAssignmentError_Understaked(msg.sender, totalStakedFor(msg.sender));
      return;
    }

    // there are no audits in the queue with a price high enough for the audit node
    uint256 requestId = dequeueAuditRequest(minPrice);
    if (requestId == 0) {
      emit LogAuditNodePriceHigherThanRequests(msg.sender, minPrice);
      return;
    }

    auditData.setAuditState(requestId, QuantstampAuditData.AuditState.Assigned);
    auditData.setAuditAuditor(requestId, msg.sender);
    auditData.setAuditAssignBlockNumber(requestId, block.number);
    assignedRequestCount[msg.sender]++;
    // push to the tail
    assignedAudits.push(requestId, PREV);

    // lock stake when assigned
    tokenEscrow.lockFunds(msg.sender, block.number.add(auditData.auditTimeoutInBlocks()).add(police.policeTimeoutInBlocks()));

    mostRecentAssignedRequestIdsPerAuditor[msg.sender] = requestId;
    emit LogAuditAssigned(requestId,
      auditData.getAuditAuditor(requestId),
      auditData.getAuditRequestor(requestId),
      auditData.getAuditContractUri(requestId),
      auditData.getAuditPrice(requestId),
      auditData.getAuditRequestBlockNumber(requestId));
  }
  /* solhint-enable function-max-lines */

  /**
   * @dev Allows the audit node to set its minimum price per audit in wei-QSP.
   * @param price The minimum price.
   */
  function setAuditNodePrice(uint256 price) public {
    require(price >= minAuditPriceLowerCap);
    require(price <= auditData.token().totalSupply());
    auditData.setMinAuditPrice(msg.sender, price);
    emit LogAuditNodePriceChanged(msg.sender, price);
  }

  /**
   * @dev Checks if an audit is finished. It is considered finished when the audit is either completed or failed.
   * @param requestId Unique ID of the audit request.
   */
  function isAuditFinished(uint256 requestId) public view returns(bool) {
    QuantstampAuditData.AuditState state = auditData.getAuditState(requestId);
    return state == QuantstampAuditData.AuditState.Completed || state == QuantstampAuditData.AuditState.Error;
  }

  /**
   * @dev Given a price, returns the next price from the priceList.
   * @param price A price indicated by a node in priceList.
   * @return The next price in the linked list.
   */
  function getNextPrice(uint256 price) public view returns(uint256) {
    bool exists;
    uint256 next;
    (exists, next) = priceList.getAdjacent(price, NEXT);
    return next;
  }

  /**
   * @dev Given a requestId, returns the next one from assignedAudits.
   * @param requestId The ID of the current linked list node
   * @return next requestId in the linked list
   */
  function getNextAssignedRequest(uint256 requestId) public view returns(uint256) {
    bool exists;
    uint256 next;
    (exists, next) = assignedAudits.getAdjacent(requestId, NEXT);
    return next;
  }

  /**
   * @dev Returns the audit request most recently assigned to msg.sender.
   * @return A tuple (requestId, audit_uri, audit_price, request_block_number).
   */
  function myMostRecentAssignedAudit() public view returns(
    uint256, // requestId
    address, // requestor
    string,  // contract uri
    uint256, // price
    uint256  // request block number
  ) {
    uint256 requestId = mostRecentAssignedRequestIdsPerAuditor[msg.sender];
    return (
      requestId,
      auditData.getAuditRequestor(requestId),
      auditData.getAuditContractUri(requestId),
      auditData.getAuditPrice(requestId),
      auditData.getAuditRequestBlockNumber(requestId)
    );
  }

  /**
   * @dev Given a price and a requestId, the function returns the next requestId with the same price.
   * Return 0, provided the given price does not exist in auditsByPrice.
   * @param price The price value of the current bucket.
   * @param requestId Unique Id of a requested audit.
   * @return The next requestId with the same price.
   */
  function getNextAuditByPrice(uint256 price, uint256 requestId) public view returns(uint256) {
    bool exists;
    uint256 next;
    (exists, next) = auditsByPrice[price].getAdjacent(requestId, NEXT);
    return next;
  }

  /**
   * @dev Given a price finds where it should be placed to build a sorted list.
   * @return next First existing price higher than the passed price.
   */
  function findPrecedingPrice(uint256 price) public view returns(uint256) {
    return priceList.getSortedSpot(HEAD, price, NEXT);
  }

  /**
   * @dev Given a requestId, the function removes it from the list of audits and decreases the number of assigned
   * audits of the associated audit node.
   * @param requestId Unique ID of a requested audit.
   */
  function updateAssignedAudits(uint256 requestId) internal {
    assignedAudits.remove(requestId);
    assignedRequestCount[auditData.getAuditAuditor(requestId)] =
      assignedRequestCount[auditData.getAuditAuditor(requestId)].sub(1);
  }

  /**
   * @dev Checks if the list of audits has any elements.
   */
  function auditQueueExists() internal view returns(bool) {
    return priceList.listExists();
  }

  /**
   * @dev Adds an audit request to the queue.
   * @param requestId Request ID.
   * @param existingPrice The price of an existing audit in the queue (makes insertion O(1)).
   */
  function queueAuditRequest(uint256 requestId, uint256 existingPrice) internal {
    uint256 price = auditData.getAuditPrice(requestId);
    if (!priceList.nodeExists(price)) {
      uint256 priceHint = priceList.nodeExists(existingPrice) ? existingPrice : HEAD;
      // if a price bucket doesn't exist, create it next to an existing one
      priceList.insert(priceList.getSortedSpot(priceHint, price, NEXT), price, PREV);
    }
    // push to the tail
    auditsByPrice[price].push(requestId, PREV);
  }

  /**
   * @dev Evaluates if there is an audit price >= minPrice.
   * Note that there should not be any audit with price as 0.
   * @param minPrice The minimum audit price.
   * @return The requestId of an audit adhering to the minPrice, or 0 if no such audit exists.
   */
  function anyAuditRequestMatchesPrice(uint256 minPrice) internal view returns(uint256) {
    bool priceExists;
    uint256 price;
    uint256 requestId;

    // picks the tail of price buckets
    (priceExists, price) = priceList.getAdjacent(HEAD, PREV);
    if (price < minPrice) {
      return 0;
    }
    requestId = getNextAuditByPrice(price, HEAD);
    return requestId;
  }

  /**
   * @dev Finds a list of most expensive audits and returns the oldest one that has a price >= minPrice.
   * @param minPrice The minimum audit price.
   */
  function dequeueAuditRequest(uint256 minPrice) internal returns(uint256) {

    uint256 requestId;
    uint256 price;

    // picks the tail of price buckets
    // TODO seems the following statement is redundantly called from getNextAuditRequest. If this is the only place
    // to call dequeueAuditRequest, then removing the following line saves gas, but leaves dequeueAuditRequest
    // unsafe for further extension.
    requestId = anyAuditRequestMatchesPrice(minPrice);

    if (requestId > 0) {
      price = auditData.getAuditPrice(requestId);
      auditsByPrice[price].remove(requestId);
      // removes the price bucket if it contains no requests
      if (!auditsByPrice[price].listExists()) {
        priceList.remove(price);
      }
      return requestId;
    }
    return 0;
  }

  /**
   * @dev Removes an element from the list.
   * @param requestId The Id of the request to be removed.
   */
  function removeQueueElement(uint256 requestId) internal {
    uint256 price = auditData.getAuditPrice(requestId);

    // the node must exist in the list
    require(priceList.nodeExists(price));
    require(auditsByPrice[price].nodeExists(requestId));

    auditsByPrice[price].remove(requestId);
    if (!auditsByPrice[price].listExists()) {
      priceList.remove(price);
    }
  }

  /**
   * @dev Internal helper function to perform the transfer of rewards.
   * @param requestId The ID of the audit request.
   */
  function transferReward (uint256 requestId) internal {
    uint256 auditPoliceFee = police.collectedFees(requestId);
    uint256 auditorPayment = auditData.getAuditPrice(requestId).sub(auditPoliceFee);
    safeTransferFromDataContract(msg.sender, auditorPayment);
    emit LogPayAuditor(requestId, msg.sender, auditorPayment);
  }

  /**
   * @dev Used to transfer funds stored in the data contract to a given address.
   * @param _to The address to transfer funds.
   * @param amount The number of wei-QSP to be transferred.
   */
  function safeTransferFromDataContract(address _to, uint256 amount) internal {
    auditData.approveWhitelisted(amount);
    require(auditData.token().transferFrom(address(auditData), _to, amount));
  }
}