pragma solidity ^0.4.18;

/**
 * @title SafeMath
 * @dev Math operations with safety checks that throw on error
 */
library SafeMath {

    /**
    * @dev Multiplies two numbers, throws on overflow.
    */
    function mul(uint256 a, uint256 b) internal pure returns (uint256 c) {
        if (a == 0) {
            return 0;
        }
        c = a * b;
        assert(c / a == b);
        return c;
    }

    /**
    * @dev Integer division of two numbers, truncating the quotient.
    */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        // assert(b > 0); // Solidity automatically throws when dividing by 0
        // uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold
        return a / b;
    }

    /**
    * @dev Subtracts two numbers, throws on overflow (i.e. if subtrahend is greater than minuend).
    */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        assert(b <= a);
        return a - b;
    }

    /**
    * @dev Adds two numbers, throws on overflow.
    */
    function add(uint256 a, uint256 b) internal pure returns (uint256 c) {
        c = a + b;
        assert(c >= a);
        return c;
    }
}


/**
 * @title Ownable
 * @dev The Ownable contract has an owner address, and provides basic authorization control
 * functions, this simplifies the implementation of "user permissions".
 */
contract Ownable {
    address public owner;


    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);


    /**
     * @dev The Ownable constructor sets the original `owner` of the contract to the sender
     * account.
     */
    function Ownable() public {
        owner = msg.sender;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(msg.sender == owner);
        _;
    }

    /**
     * @dev Allows the current owner to transfer control of the contract to a newOwner.
     * @param newOwner The address to transfer ownership to.
     */
    function transferOwnership(address newOwner) public onlyOwner {
        require(newOwner != address(0));
        emit OwnershipTransferred(owner, newOwner);
        owner = newOwner;
    }
}

/**
 * @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);
}

/**
 * @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];
    }

}

/**
 * @title ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/20
 */
contract ERC20 is ERC20Basic {
    function allowance(address owner, address spender) public view returns (uint256);
    function transferFrom(address from, address to, uint256 value) public returns (bool);
    function approve(address spender, uint256 value) public returns (bool);
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

/**
 * @title 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];
    }
}

/**
 * @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);

    //     _;
    // }
}

/**
 * @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;
    }

}

/**
 * @title Titan Coin Contract
 */
contract TitanToken is Ownable, StandardToken, RBAC {

    string public name = 'Titan Coin';
    string public symbol = 'TC';
    uint256 public decimals = 8;

    string public constant ROLE_EXCHANGER = "exchanger";

    uint256 public constant INITIAL_SUPPLY = 100000000 * 10 ** 8;
    uint256 public MAXIMUM_ICO_TOKENS = 87000000 * 10 ** 8;

    uint256 public MAX_BOUNTY_ALLOCATED_TOKENS = 3000000;
    uint256 public OWNERS_ALLOCATED_TOKENS = 100000000;

    modifier hasExchangePermission() {
        checkRole(msg.sender, ROLE_EXCHANGER);
        _;
    }

    constructor() public {
        totalSupply_ = INITIAL_SUPPLY;
        balances[this] = INITIAL_SUPPLY;
    }

    /**
     * @dev add an exchanger role to an address
     * @param exchanger address
     */
    function addExchanger(address exchanger) onlyOwner public {
        addRole(exchanger, ROLE_EXCHANGER);
    }

    /**
     * @dev remove an exchanger role from an address
     * @param exchanger address
     */
    function removeExchanger(address exchanger) onlyOwner public {
        removeRole(exchanger, ROLE_EXCHANGER);
    }

    function exchangeTokens(address _to, uint256 _amount) hasExchangePermission public returns (bool) {
        this.transfer(_to, _amount);
        return true;
    }
}