// File: openzeppelin-solidity/contracts/token/ERC20/IERC20.sol

pragma solidity ^0.5.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP. Does not include
 * the optional functions; to access them see `ERC20Detailed`.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a `Transfer` event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through `transferFrom`. This is
     * zero by default.
     *
     * This value changes when `approve` or `transferFrom` are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * > 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
     *
     * Emits an `Approval` event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a `Transfer` event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to `approve`. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

// File: openzeppelin-solidity/contracts/math/SafeMath.sol

pragma solidity ^0.5.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring '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;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, "SafeMath: division by zero");
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b != 0, "SafeMath: modulo by zero");
        return a % b;
    }
}

// File: openzeppelin-solidity/contracts/token/ERC20/ERC20.sol

pragma solidity ^0.5.0;



/**
 * @dev Implementation of the `IERC20` interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using `_mint`.
 * For a generic mechanism see `ERC20Mintable`.
 *
 * *For a detailed writeup see our guide [How to implement supply
 * mechanisms](https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226).*
 *
 * We have followed general OpenZeppelin guidelines: functions revert instead
 * of returning `false` on failure. This behavior is nonetheless conventional
 * and does not conflict with the expectations of ERC20 applications.
 *
 * Additionally, an `Approval` event is emitted on calls to `transferFrom`.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard `decreaseAllowance` and `increaseAllowance`
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See `IERC20.approve`.
 */
contract ERC20 is IERC20 {
    using SafeMath for uint256;

    mapping (address => uint256) private _balances;

    mapping (address => mapping (address => uint256)) private _allowances;

    uint256 private _totalSupply;

    /**
     * @dev See `IERC20.totalSupply`.
     */
    function totalSupply() public view returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See `IERC20.balanceOf`.
     */
    function balanceOf(address account) public view returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See `IERC20.transfer`.
     *
     * Requirements:
     *
     * - `recipient` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address recipient, uint256 amount) public returns (bool) {
        _transfer(msg.sender, recipient, amount);
        return true;
    }

    /**
     * @dev See `IERC20.allowance`.
     */
    function allowance(address owner, address spender) public view returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See `IERC20.approve`.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 value) public returns (bool) {
        _approve(msg.sender, spender, value);
        return true;
    }

    /**
     * @dev See `IERC20.transferFrom`.
     *
     * Emits an `Approval` event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of `ERC20`;
     *
     * Requirements:
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `value`.
     * - the caller must have allowance for `sender`'s tokens of at least
     * `amount`.
     */
    function transferFrom(address sender, address recipient, uint256 amount) public returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(sender, msg.sender, _allowances[sender][msg.sender].sub(amount));
        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to `approve` that can be used as a mitigation for
     * problems described in `IERC20.approve`.
     *
     * Emits an `Approval` event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public returns (bool) {
        _approve(msg.sender, spender, _allowances[msg.sender][spender].add(addedValue));
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to `approve` that can be used as a mitigation for
     * problems described in `IERC20.approve`.
     *
     * Emits an `Approval` event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) {
        _approve(msg.sender, spender, _allowances[msg.sender][spender].sub(subtractedValue));
        return true;
    }

    /**
     * @dev Moves tokens `amount` from `sender` to `recipient`.
     *
     * This is internal function is equivalent to `transfer`, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a `Transfer` event.
     *
     * Requirements:
     *
     * - `sender` cannot be the zero address.
     * - `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     */
    function _transfer(address sender, address recipient, uint256 amount) internal {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        _balances[sender] = _balances[sender].sub(amount);
        _balances[recipient] = _balances[recipient].add(amount);
        emit Transfer(sender, recipient, amount);
    }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a `Transfer` event with `from` set to the zero address.
     *
     * Requirements
     *
     * - `to` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal {
        require(account != address(0), "ERC20: mint to the zero address");

        _totalSupply = _totalSupply.add(amount);
        _balances[account] = _balances[account].add(amount);
        emit Transfer(address(0), account, amount);
    }

     /**
     * @dev Destoys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a `Transfer` event with `to` set to the zero address.
     *
     * Requirements
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 value) internal {
        require(account != address(0), "ERC20: burn from the zero address");

        _totalSupply = _totalSupply.sub(value);
        _balances[account] = _balances[account].sub(value);
        emit Transfer(account, address(0), value);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner`s tokens.
     *
     * This is internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an `Approval` event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(address owner, address spender, uint256 value) internal {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = value;
        emit Approval(owner, spender, value);
    }

    /**
     * @dev Destoys `amount` tokens from `account`.`amount` is then deducted
     * from the caller's allowance.
     *
     * See `_burn` and `_approve`.
     */
    function _burnFrom(address account, uint256 amount) internal {
        _burn(account, amount);
        _approve(account, msg.sender, _allowances[account][msg.sender].sub(amount));
    }
}

// File: openzeppelin-solidity/contracts/access/Roles.sol

pragma solidity ^0.5.0;

/**
 * @title Roles
 * @dev Library for managing addresses assigned to a Role.
 */
library Roles {
    struct Role {
        mapping (address => bool) bearer;
    }

    /**
     * @dev Give an account access to this role.
     */
    function add(Role storage role, address account) internal {
        require(!has(role, account), "Roles: account already has role");
        role.bearer[account] = true;
    }

    /**
     * @dev Remove an account's access to this role.
     */
    function remove(Role storage role, address account) internal {
        require(has(role, account), "Roles: account does not have role");
        role.bearer[account] = false;
    }

    /**
     * @dev Check if an account has this role.
     * @return bool
     */
    function has(Role storage role, address account) internal view returns (bool) {
        require(account != address(0), "Roles: account is the zero address");
        return role.bearer[account];
    }
}

// File: openzeppelin-solidity/contracts/access/roles/MinterRole.sol

pragma solidity ^0.5.0;


contract MinterRole {
    using Roles for Roles.Role;

    event MinterAdded(address indexed account);
    event MinterRemoved(address indexed account);

    Roles.Role private _minters;

    constructor () internal {
        _addMinter(msg.sender);
    }

    modifier onlyMinter() {
        require(isMinter(msg.sender), "MinterRole: caller does not have the Minter role");
        _;
    }

    function isMinter(address account) public view returns (bool) {
        return _minters.has(account);
    }

    function addMinter(address account) public onlyMinter {
        _addMinter(account);
    }

    function renounceMinter() public {
        _removeMinter(msg.sender);
    }

    function _addMinter(address account) internal {
        _minters.add(account);
        emit MinterAdded(account);
    }

    function _removeMinter(address account) internal {
        _minters.remove(account);
        emit MinterRemoved(account);
    }
}

// File: contracts/token/ERC20Interface.sol

pragma solidity 0.5.9;


interface ERC20Interface {
  // Standard ERC-20 interface.
  function transfer(address to, uint256 value) external returns (bool);
  function approve(address spender, uint256 value) external returns (bool);
  function transferFrom(address from, address to, uint256 value) external returns (bool);
  function totalSupply() external view returns (uint256);
  function balanceOf(address who) external view returns (uint256);
  function allowance(address owner, address spender) external view returns (uint256);
  // Extension of ERC-20 interface to support supply adjustment.
  function mint(address to, uint256 value) external returns (bool);
  function burn(address from, uint256 value) external returns (bool);
}

// File: contracts/token/ERC20Base.sol

pragma solidity 0.5.9;





/// "ERC20Base" is the standard ERC-20 implementation that allows its minter to mint tokens. Both BandToken and
/// CommunityToken extend from ERC20Base. In addition to the standard functions, the class provides `transferAndCall`
/// function, which performs a transfer and invokes the given function using the provided data. If the destination
/// contract uses "ERC20Acceptor" interface, it can verify that the caller properly sends appropriate amount of tokens.
contract ERC20Base is ERC20Interface, ERC20, MinterRole {
  string public name;
  string public symbol;
  uint8 public decimals = 18;

  constructor(string memory _name, string memory _symbol) public {
    name = _name;
    symbol = _symbol;
  }

  function transferAndCall(address to, uint256 value, bytes4 sig, bytes memory data) public returns (bool) {
    require(to != address(this));
    _transfer(msg.sender, to, value);
    (bool success,) = to.call(abi.encodePacked(sig, uint256(msg.sender), value, data));
    require(success);
    return true;
  }

  function mint(address to, uint256 value) public onlyMinter returns (bool) {
    _mint(to, value);
    return true;
  }

  function burn(address from, uint256 value) public onlyMinter returns (bool) {
    _burn(from, value);
    return true;
  }
}

// File: contracts/token/SnapshotToken.sol

pragma solidity 0.5.9;




contract SnapshotToken is ERC20Base {
  using SafeMath for uint256;

  /// IMPORTANT: votingPowers are kept as a linked list of ALL historical changes.
  /// - This allows the contract to figure out voting power of the address at any nonce `n`, by
  /// searching for the node that has the biggest nonce that is not greater than `n`.
  /// - For efficiency, nonce and power are packed into one uint256 integer, with the top 64 bits
  /// representing nonce, and the bottom 192 bits representing voting power.
  mapping (address => mapping(uint256 => uint256)) _votingPower;
  mapping (address => uint256) public votingPowerChangeCount;
  uint256 public votingPowerChangeNonce = 0;

  /// Returns user voting power at the given index, that is, as of the user's index^th voting power change
  function historicalVotingPowerAtIndex(address owner, uint256 index) public view returns (uint256) {
    require(index <= votingPowerChangeCount[owner]);
    return _votingPower[owner][index] & ((1 << 192) - 1);  // Lower 192 bits
  }

  /// Returns user voting power at the given time. Under the hood, this performs binary search
  /// to look for the largest index at which the nonce is not greater than 'nonce'.
  /// The voting power at that index is the returning value.
  function historicalVotingPowerAtNonce(address owner, uint256 nonce) public view returns (uint256) {
    require(nonce <= votingPowerChangeNonce && nonce < (1 << 64));
    uint256 start = 0;
    uint256 end = votingPowerChangeCount[owner];
    while (start < end) {
      uint256 mid = start.add(end).add(1).div(2); /// Use (start+end+1)/2 to prevent infinite loop.
      if ((_votingPower[owner][mid] >> 192) > nonce) {  /// Upper 64-bit nonce
        /// If midTime > nonce, this mid can't possibly be the answer.
        end = mid.sub(1);
      } else {
        /// Otherwise, search on the greater side, but still keep mid as a possible option.
        start = mid;
      }
    }
    return historicalVotingPowerAtIndex(owner, start);
  }

  function _transfer(address from, address to, uint256 value) internal {
    super._transfer(from, to, value);
    votingPowerChangeNonce = votingPowerChangeNonce.add(1);
    _changeVotingPower(from);
    _changeVotingPower(to);
  }

  function _mint(address account, uint256 amount) internal {
    super._mint(account, amount);
    votingPowerChangeNonce = votingPowerChangeNonce.add(1);
    _changeVotingPower(account);
  }

  function _burn(address account, uint256 amount) internal {
    super._burn(account, amount);
    votingPowerChangeNonce = votingPowerChangeNonce.add(1);
    _changeVotingPower(account);
  }

  function _changeVotingPower(address account) internal {
    uint256 currentIndex = votingPowerChangeCount[account];
    uint256 newPower = balanceOf(account);
    require(newPower < (1 << 192));
    require(votingPowerChangeNonce < (1 << 64));
    currentIndex = currentIndex.add(1);
    votingPowerChangeCount[account] = currentIndex;
    _votingPower[account][currentIndex] = (votingPowerChangeNonce << 192) | newPower;
  }
}

// File: openzeppelin-solidity/contracts/math/Math.sol

pragma solidity ^0.5.0;

/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library Math {
    /**
     * @dev Returns the largest of two numbers.
     */
    function max(uint256 a, uint256 b) internal pure returns (uint256) {
        return a >= b ? a : b;
    }

    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }

    /**
     * @dev Returns the average of two numbers. The result is rounded towards
     * zero.
     */
    function average(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b) / 2 can overflow, so we distribute
        return (a / 2) + (b / 2) + ((a % 2 + b % 2) / 2);
    }
}

// File: openzeppelin-solidity/contracts/access/roles/CapperRole.sol

pragma solidity ^0.5.0;


contract CapperRole {
    using Roles for Roles.Role;

    event CapperAdded(address indexed account);
    event CapperRemoved(address indexed account);

    Roles.Role private _cappers;

    constructor () internal {
        _addCapper(msg.sender);
    }

    modifier onlyCapper() {
        require(isCapper(msg.sender), "CapperRole: caller does not have the Capper role");
        _;
    }

    function isCapper(address account) public view returns (bool) {
        return _cappers.has(account);
    }

    function addCapper(address account) public onlyCapper {
        _addCapper(account);
    }

    function renounceCapper() public {
        _removeCapper(msg.sender);
    }

    function _addCapper(address account) internal {
        _cappers.add(account);
        emit CapperAdded(account);
    }

    function _removeCapper(address account) internal {
        _cappers.remove(account);
        emit CapperRemoved(account);
    }
}

// File: contracts/token/LockableToken.sol

pragma solidity 0.5.9;






/// "LockableToken" adds token locking functionality to ERC-20 smart contract. The authorized addresses (Cappers) are
/// allowed to lock tokens from any token holder to prevent token transfers up to that amount. If a token holder is
/// locked by multiple cappers, the maximum number is used as the amount of locked tokens.
contract LockableToken is ERC20Base, CapperRole {
  using SafeMath for uint256;

  event TokenLocked(address indexed locker, address indexed owner, uint256 value);
  event TokenUnlocked(address indexed locker, address indexed owner, uint256 value);

  uint256 constant NOT_FOUND = uint256(-1);

  struct TokenLock {
    address locker;
    uint256 value;
  }

  mapping (address => TokenLock[]) _locks;

  function getLockedToken(address owner) public view returns (uint256) {
    TokenLock[] storage locks = _locks[owner];
    uint256 maxLock = 0;
    for (uint256 i = 0; i < locks.length; ++i) {
      maxLock = Math.max(maxLock, locks[i].value);
    }
    return maxLock;
  }

  function getLockedTokenAt(address owner, address locker) public view returns (uint256) {
    uint256 index = _getTokenLockIndex(owner, locker);
    if (index != NOT_FOUND) return _locks[owner][index].value;
    else return 0;
  }

  function unlockedBalanceOf(address owner) public view returns (uint256) {
    return balanceOf(owner).sub(getLockedToken(owner));
  }

  function lock(address owner, uint256 value) public onlyCapper returns (bool) {
    uint256 index = _getTokenLockIndex(owner, msg.sender);
    if (index != NOT_FOUND) {
      uint256 currentLock = _locks[owner][index].value;
      require(balanceOf(owner) >= currentLock.add(value));
      _locks[owner][index].value = currentLock.add(value);
    } else {
      require(balanceOf(owner) >= value);
      _locks[owner].push(TokenLock(msg.sender, value));
    }
    emit TokenLocked(msg.sender, owner, value);
    return true;
  }

  function unlock(address owner, uint256 value) public returns (bool) {
    uint256 index = _getTokenLockIndex(owner, msg.sender);
    require(index != NOT_FOUND);
    TokenLock[] storage locks = _locks[owner];
    require(locks[index].value >= value);
    locks[index].value = locks[index].value.sub(value);
    if (locks[index].value == 0) {
      if (index != locks.length - 1) {
        locks[index] = locks[locks.length - 1];
      }
      locks.pop();
    }
    emit TokenUnlocked(msg.sender, owner, value);
    return true;
  }

  function _getTokenLockIndex(address owner, address locker) internal view returns (uint256) {
    TokenLock[] storage locks = _locks[owner];
    for (uint256 i = 0; i < locks.length; ++i) {
      if (locks[i].locker == locker) return i;
    }
    return NOT_FOUND;
  }

  function _transfer(address from, address to, uint256 value) internal {
    require(unlockedBalanceOf(from) >= value);
    super._transfer(from, to, value);
  }

  function _burn(address account, uint256 value) internal {
    require(unlockedBalanceOf(account) >= value);
    super._burn(account, value);
  }
}

// File: contracts/CommunityToken.sol

pragma solidity 0.5.9;





/// "CommunityToken" is an ERC-20 token specific for each dataset community.
contract CommunityToken is SnapshotToken, LockableToken {
  constructor(string memory name, string memory symbol) public ERC20Base(name, symbol) {}
}

{
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