// File: @openzeppelin/contracts/math/SafeMath.sol

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @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) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        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-contracts/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) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message 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, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        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) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message 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, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

// File: @openzeppelin/contracts/token/ERC20/IERC20.sol


pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
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.
     *
     * IMPORTANT: 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: contracts/common/Validating.sol

pragma solidity 0.7.1;


interface Validating {
  modifier notZero(uint number) { require(number > 0, "invalid 0 value"); _; }
  modifier notEmpty(string memory text) { require(bytes(text).length > 0, "invalid empty string"); _; }
  modifier validAddress(address value) { require(value != address(0x0), "invalid address"); _; }
}

// File: contracts/external/BytesLib.sol

pragma solidity 0.7.1;

/*
 * @title Solidity Bytes Arrays Utils
 * @author Gonçalo Sá <goncalo.sa@consensys.net>
 *
 * @dev Bytes tightly packed arrays utility library for ethereum contracts written in Solidity.
 *    The library lets you concatenate, slice and type cast bytes arrays both in memory and storage.
 */
library BytesLib {
  function concat(
    bytes memory _preBytes,
    bytes memory _postBytes
  )
    internal
    pure
    returns (bytes memory)
  {
    bytes memory tempBytes;

    assembly {
      // Get a location of some free memory and store it in tempBytes as
      // Solidity does for memory variables.
      tempBytes := mload(0x40)

      // Store the length of the first bytes array at the beginning of
      // the memory for tempBytes.
      let length := mload(_preBytes)
      mstore(tempBytes, length)

      // Maintain a memory counter for the current write location in the
      // temp bytes array by adding the 32 bytes for the array length to
      // the starting location.
      let mc := add(tempBytes, 0x20)
      // Stop copying when the memory counter reaches the length of the
      // first bytes array.
      let end := add(mc, length)

      for {
        // Initialize a copy counter to the start of the _preBytes data,
        // 32 bytes into its memory.
        let cc := add(_preBytes, 0x20)
      } lt(mc, end) {
        // Increase both counters by 32 bytes each iteration.
        mc := add(mc, 0x20)
        cc := add(cc, 0x20)
      } {
        // Write the _preBytes data into the tempBytes memory 32 bytes
        // at a time.
        mstore(mc, mload(cc))
      }

      // Add the length of _postBytes to the current length of tempBytes
      // and store it as the new length in the first 32 bytes of the
      // tempBytes memory.
      length := mload(_postBytes)
      mstore(tempBytes, add(length, mload(tempBytes)))

      // Move the memory counter back from a multiple of 0x20 to the
      // actual end of the _preBytes data.
      mc := end
      // Stop copying when the memory counter reaches the new combined
      // length of the arrays.
      end := add(mc, length)

      for {
        let cc := add(_postBytes, 0x20)
      } lt(mc, end) {
        mc := add(mc, 0x20)
        cc := add(cc, 0x20)
      } {
        mstore(mc, mload(cc))
      }

      // Update the free-memory pointer by padding our last write location
      // to 32 bytes: add 31 bytes to the end of tempBytes to move to the
      // next 32 byte block, then round down to the nearest multiple of
      // 32. If the sum of the length of the two arrays is zero then add
      // one before rounding down to leave a blank 32 bytes (the length block with 0).
      mstore(0x40, and(
        add(add(end, iszero(add(length, mload(_preBytes)))), 31),
        not(31) // Round down to the nearest 32 bytes.
      ))
    }

    return tempBytes;
  }

  function concatStorage(bytes storage _preBytes, bytes memory _postBytes) internal {
    assembly {
      // Read the first 32 bytes of _preBytes storage, which is the length
      // of the array. (We don't need to use the offset into the slot
      // because arrays use the entire slot.)
      let fslot := sload(_preBytes.slot)
      // Arrays of 31 bytes or less have an even value in their slot,
      // while longer arrays have an odd value. The actual length is
      // the slot divided by two for odd values, and the lowest order
      // byte divided by two for even values.
      // If the slot is even, bitwise and the slot with 255 and divide by
      // two to get the length. If the slot is odd, bitwise and the slot
      // with -1 and divide by two.
      let slength := div(and(fslot, sub(mul(0x100, iszero(and(fslot, 1))), 1)), 2)
      let mlength := mload(_postBytes)
      let newlength := add(slength, mlength)
      // slength can contain both the length and contents of the array
      // if length < 32 bytes so let's prepare for that
      // v. http://solidity.readthedocs.io/en/latest/miscellaneous.html#layout-of-state-variables-in-storage
      switch add(lt(slength, 32), lt(newlength, 32))
      case 2 {
        // Since the new array still fits in the slot, we just need to
        // update the contents of the slot.
        // uint(bytes_storage) = uint(bytes_storage) + uint(bytes_memory) + new_length
        sstore(
          _preBytes.slot,
          // all the modifications to the slot are inside this
          // next block
          add(
            // we can just add to the slot contents because the
            // bytes we want to change are the LSBs
            fslot,
            add(
              mul(
                div(
                  // load the bytes from memory
                  mload(add(_postBytes, 0x20)),
                  // zero all bytes to the right
                  exp(0x100, sub(32, mlength))
                ),
                // and now shift left the number of bytes to
                // leave space for the length in the slot
                exp(0x100, sub(32, newlength))
              ),
              // increase length by the double of the memory
              // bytes length
              mul(mlength, 2)
            )
          )
        )
      }
      case 1 {
        // The stored value fits in the slot, but the combined value
        // will exceed it.
        // get the keccak hash to get the contents of the array
        mstore(0x0, _preBytes.slot)
        let sc := add(keccak256(0x0, 0x20), div(slength, 32))

        // save new length
        sstore(_preBytes.slot, add(mul(newlength, 2), 1))

        // The contents of the _postBytes array start 32 bytes into
        // the structure. Our first read should obtain the `submod`
        // bytes that can fit into the unused space in the last word
        // of the stored array. To get this, we read 32 bytes starting
        // from `submod`, so the data we read overlaps with the array
        // contents by `submod` bytes. Masking the lowest-order
        // `submod` bytes allows us to add that value directly to the
        // stored value.

        let submod := sub(32, slength)
        let mc := add(_postBytes, submod)
        let end := add(_postBytes, mlength)
        let mask := sub(exp(0x100, submod), 1)

        sstore(
          sc,
          add(
            and(
              fslot,
              0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff00
            ),
            and(mload(mc), mask)
          )
        )

        for {
          mc := add(mc, 0x20)
          sc := add(sc, 1)
        } lt(mc, end) {
          sc := add(sc, 1)
          mc := add(mc, 0x20)
        } {
          sstore(sc, mload(mc))
        }

        mask := exp(0x100, sub(mc, end))

        sstore(sc, mul(div(mload(mc), mask), mask))
      }
      default {
        // get the keccak hash to get the contents of the array
        mstore(0x0, _preBytes.slot)
        // Start copying to the last used word of the stored array.
        let sc := add(keccak256(0x0, 0x20), div(slength, 32))

        // save new length
        sstore(_preBytes.slot, add(mul(newlength, 2), 1))

        // Copy over the first `submod` bytes of the new data as in
        // case 1 above.
        let slengthmod := mod(slength, 32)
        let mlengthmod := mod(mlength, 32)
        let submod := sub(32, slengthmod)
        let mc := add(_postBytes, submod)
        let end := add(_postBytes, mlength)
        let mask := sub(exp(0x100, submod), 1)

        sstore(sc, add(sload(sc), and(mload(mc), mask)))

        for {
          sc := add(sc, 1)
          mc := add(mc, 0x20)
        } lt(mc, end) {
          sc := add(sc, 1)
          mc := add(mc, 0x20)
        } {
          sstore(sc, mload(mc))
        }

        mask := exp(0x100, sub(mc, end))

        sstore(sc, mul(div(mload(mc), mask), mask))
      }
    }
  }

  function slice(
    bytes memory _bytes,
    uint _start,
    uint _length
  )
    internal
    pure
    returns (bytes memory)
  {
    require(_length + 31 >= _length, "slice_overflow");
    require(_start + _length >= _start, "slice_overflow");
    require(_bytes.length >= _start + _length, "slice_outOfBounds");

    bytes memory tempBytes;

    assembly {
      switch iszero(_length)
      case 0 {
        // Get a location of some free memory and store it in tempBytes as
        // Solidity does for memory variables.
        tempBytes := mload(0x40)

        // The first word of the slice result is potentially a partial
        // word read from the original array. To read it, we calculate
        // the length of that partial word and start copying that many
        // bytes into the array. The first word we copy will start with
        // data we don't care about, but the last `lengthmod` bytes will
        // land at the beginning of the contents of the new array. When
        // we're done copying, we overwrite the full first word with
        // the actual length of the slice.
        let lengthmod := and(_length, 31)

        // The multiplication in the next line is necessary
        // because when slicing multiples of 32 bytes (lengthmod == 0)
        // the following copy loop was copying the origin's length
        // and then ending prematurely not copying everything it should.
        let mc := add(add(tempBytes, lengthmod), mul(0x20, iszero(lengthmod)))
        let end := add(mc, _length)

        for {
          // The multiplication in the next line has the same exact purpose
          // as the one above.
          let cc := add(add(add(_bytes, lengthmod), mul(0x20, iszero(lengthmod))), _start)
        } lt(mc, end) {
          mc := add(mc, 0x20)
          cc := add(cc, 0x20)
        } {
          mstore(mc, mload(cc))
        }

        mstore(tempBytes, _length)

        //update free-memory pointer
        //allocating the array padded to 32 bytes like the compiler does now
        mstore(0x40, and(add(mc, 31), not(31)))
      }
      //if we want a zero-length slice let's just return a zero-length array
      default {
        tempBytes := mload(0x40)

        mstore(0x40, add(tempBytes, 0x20))
      }
    }

    return tempBytes;
  }

  function toAddress(bytes memory _bytes, uint _start) internal pure returns (address) {
    require(_start + 20 >= _start, "toAddress_overflow");
    require(_bytes.length >= _start + 20, "toAddress_outOfBounds");
    address tempAddress;

    assembly {
      tempAddress := div(mload(add(add(_bytes, 0x20), _start)), 0x1000000000000000000000000)
    }

    return tempAddress;
  }

  function toUint8(bytes memory _bytes, uint _start) internal pure returns (uint8) {
    require(_start + 1 >= _start, "toUint8_overflow");
    require(_bytes.length >= _start + 1 , "toUint8_outOfBounds");
    uint8 tempUint;

    assembly {
      tempUint := mload(add(add(_bytes, 0x1), _start))
    }

    return tempUint;
  }

  function toUint16(bytes memory _bytes, uint _start) internal pure returns (uint16) {
    require(_start + 2 >= _start, "toUint16_overflow");
    require(_bytes.length >= _start + 2, "toUint16_outOfBounds");
    uint16 tempUint;

    assembly {
      tempUint := mload(add(add(_bytes, 0x2), _start))
    }

    return tempUint;
  }

  function toUint32(bytes memory _bytes, uint _start) internal pure returns (uint32) {
    require(_start + 4 >= _start, "toUint32_overflow");
    require(_bytes.length >= _start + 4, "toUint32_outOfBounds");
    uint32 tempUint;

    assembly {
      tempUint := mload(add(add(_bytes, 0x4), _start))
    }

    return tempUint;
  }

  function toUint64(bytes memory _bytes, uint _start) internal pure returns (uint64) {
    require(_start + 8 >= _start, "toUint64_overflow");
    require(_bytes.length >= _start + 8, "toUint64_outOfBounds");
    uint64 tempUint;

    assembly {
      tempUint := mload(add(add(_bytes, 0x8), _start))
    }

    return tempUint;
  }

  function toUint96(bytes memory _bytes, uint _start) internal pure returns (uint96) {
    require(_start + 12 >= _start, "toUint96_overflow");
    require(_bytes.length >= _start + 12, "toUint96_outOfBounds");
    uint96 tempUint;

    assembly {
      tempUint := mload(add(add(_bytes, 0xc), _start))
    }

    return tempUint;
  }

  function toUint128(bytes memory _bytes, uint _start) internal pure returns (uint128) {
    require(_start + 16 >= _start, "toUint128_overflow");
    require(_bytes.length >= _start + 16, "toUint128_outOfBounds");
    uint128 tempUint;

    assembly {
      tempUint := mload(add(add(_bytes, 0x10), _start))
    }

    return tempUint;
  }

  function toUint256(bytes memory _bytes, uint _start) internal pure returns (uint) {
    require(_start + 32 >= _start, "toUint256_overflow");
    require(_bytes.length >= _start + 32, "toUint256_outOfBounds");
    uint tempUint;

    assembly {
      tempUint := mload(add(add(_bytes, 0x20), _start))
    }

    return tempUint;
  }

  function toUint(bytes memory _bytes, uint _start) internal pure returns (uint) {
    return toUint256(_bytes, _start);
  }

  function toBytes32(bytes memory _bytes, uint _start) internal pure returns (bytes32) {
    require(_start + 32 >= _start, "toBytes32_overflow");
    require(_bytes.length >= _start + 32, "toBytes32_outOfBounds");
    bytes32 tempBytes32;

    assembly {
      tempBytes32 := mload(add(add(_bytes, 0x20), _start))
    }

    return tempBytes32;
  }

  function equal(bytes memory _preBytes, bytes memory _postBytes) internal pure returns (bool) {
    bool success = true;

    assembly {
      let length := mload(_preBytes)

      // if lengths don't match the arrays are not equal
      switch eq(length, mload(_postBytes))
      case 1 {
        // cb is a circuit breaker in the for loop since there's
        //  no said feature for inline assembly loops
        // cb = 1 - don't breaker
        // cb = 0 - break
        let cb := 1

        let mc := add(_preBytes, 0x20)
        let end := add(mc, length)

        for {
          let cc := add(_postBytes, 0x20)
        // the next line is the loop condition:
        // while(uint(mc < end) + cb == 2)
        } eq(add(lt(mc, end), cb), 2) {
          mc := add(mc, 0x20)
          cc := add(cc, 0x20)
        } {
          // if any of these checks fails then arrays are not equal
          if iszero(eq(mload(mc), mload(cc))) {
            // unsuccess:
            success := 0
            cb := 0
          }
        }
      }
      default {
        // unsuccess:
        success := 0
      }
    }

    return success;
  }

  function equalStorage(
    bytes storage _preBytes,
    bytes memory _postBytes
  )
    internal
    view
    returns (bool)
  {
    bool success = true;

    assembly {
      // we know _preBytes_offset is 0
      let fslot := sload(_preBytes.slot)
      // Decode the length of the stored array like in concatStorage().
      let slength := div(and(fslot, sub(mul(0x100, iszero(and(fslot, 1))), 1)), 2)
      let mlength := mload(_postBytes)

      // if lengths don't match the arrays are not equal
      switch eq(slength, mlength)
      case 1 {
        // slength can contain both the length and contents of the array
        // if length < 32 bytes so let's prepare for that
        // v. http://solidity.readthedocs.io/en/latest/miscellaneous.html#layout-of-state-variables-in-storage
        if iszero(iszero(slength)) {
          switch lt(slength, 32)
          case 1 {
            // blank the last byte which is the length
            fslot := mul(div(fslot, 0x100), 0x100)

            if iszero(eq(fslot, mload(add(_postBytes, 0x20)))) {
              // unsuccess:
              success := 0
            }
          }
          default {
            // cb is a circuit breaker in the for loop since there's
            //  no said feature for inline assembly loops
            // cb = 1 - don't breaker
            // cb = 0 - break
            let cb := 1

            // get the keccak hash to get the contents of the array
            mstore(0x0, _preBytes.slot)
            let sc := keccak256(0x0, 0x20)

            let mc := add(_postBytes, 0x20)
            let end := add(mc, mlength)

            // the next line is the loop condition:
            // while(uint(mc < end) + cb == 2)
            for {} eq(add(lt(mc, end), cb), 2) {
              sc := add(sc, 1)
              mc := add(mc, 0x20)
            } {
              if iszero(eq(sload(sc), mload(mc))) {
                // unsuccess:
                success := 0
                cb := 0
              }
            }
          }
        }
      }
      default {
        // unsuccess:
        success := 0
      }
    }

    return success;
  }
}

// File: contracts/gluon/AppGovernance.sol

pragma solidity 0.7.1;


interface AppGovernance {
  function approve(uint32 id) external;
  function disapprove(uint32 id) external;
  function activate(uint32 id) external;
}

// File: contracts/gluon/AppLogic.sol

pragma solidity 0.7.1;


/**
  * @notice representing an app's in-and-out transfers of assets
  * @dev an account/asset based app should implement its own bookkeeping
  */
interface AppLogic {

  /// @notice when an app proposal has been activated, Gluon will call this method on the previously active app version
  /// @dev each app must implement, providing a future upgrade path, and call retire_() at the very end.
  /// this is the chance for the previously active app version to migrate to the new version
  /// i.e.: migrating data, deprecate prior behavior, releasing resources, etc.
  function upgrade() external;

  /// @dev once an asset has been deposited into the app's safe within Gluon, the app is given the chance to do
  /// it's own per account/asset bookkeeping
  ///
  /// @param account any Ethereum address
  /// @param asset any ERC20 token or ETH (represented by address 0x0)
  /// @param quantity quantity of asset
  function credit(address account, address asset, uint quantity) external;

  /// @dev before an asset can be withdrawn from the app's safe within Gluon, the quantity and asset to withdraw must be
  /// derived from `parameters`. if the app is account/asset based, it should take this opportunity to:
  /// - also derive the owning account from `parameters`
  /// - prove that the owning account indeed has the derived quantity of the derived asset
  /// - do it's own per account/asset bookkeeping
  /// notice that the derived account is not necessarily the same as the provided account; a classic usage example is
  /// an account transfers assets across app (in which case the provided account would be the target app)
  ///
  /// @param account any Ethereum address to which `quantity` of `asset` would be transferred to
  /// @param parameters a bytes-marshalled record containing all data needed for the app-specific logic
  /// @return asset any ERC20 token or ETH (represented by address 0x0)
  /// @return quantity quantity of asset
  function debit(address account, bytes calldata parameters) external returns (address asset, uint quantity);
}

// File: contracts/gluon/AppState.sol

pragma solidity 0.7.1;

/**
  * @title representing an app's life-cycle
  * @notice an app's life-cycle starts in the ON state, then it is either move to the final OFF state,
  * or to the RETIRED state when it upgrades itself to its successor version.
  */
contract AppState {

  enum State { OFF, ON, RETIRED }
  State public state = State.ON;
  event Off();
  event Retired();

  /// @notice app must be active (when current)
  modifier whenOn() { require(state == State.ON, "must be on"); _; }

  /// @notice app must be halted
  modifier whenOff() { require(state == State.OFF, "must be off"); _; }

  /// @notice app must be retired (when no longer current, after being upgraded)
  modifier whenRetired() { require(state == State.RETIRED, "must be retired"); _; }

  /// @dev retire the app. this action is irreversible.
  /// called during a normal upgrade operation. by the end of this call the approved proposal would be active.
  function retire_() internal whenOn {
    state = State.RETIRED;
    emit Retired();
  }

  /// @notice halt the app. this action is irreversible.
  /// (the only option at this point is have a proposal that will get to approval, then activated.)
  /// should be called by an app-owner when the app has been compromised.
  function switchOff_() internal whenOn {
    state = State.OFF;
    emit Off();
  }

  /// @notice app state is active, i.e: current & active
  function isOn() external view returns (bool) { return state == State.ON; }

}

// File: contracts/common/Versioned.sol

pragma solidity 0.7.1;


contract Versioned {

  string public version;

  constructor(string memory version_) { version = version_; }

}

// File: contracts/gluon/GluonWallet.sol

pragma solidity 0.7.1;


interface GluonWallet {
  function depositEther(uint32 id) external payable;
  function depositToken(uint32 id, address token, uint quantity) external;
  function withdraw(uint32 id, bytes calldata parameters) external;
  function transfer(uint32 from, uint32 to, bytes calldata parameters) external;
}

// File: contracts/apps/stake/Governing.sol

pragma solidity 0.7.1;


interface Governing {
  function deleteVoteTally(address proposal) external;
  function activationInterval() external view returns (uint);
  function governanceToken() external returns (address);
}

// File: contracts/common/HasOwners.sol

pragma solidity 0.7.1;



/// @notice providing an ownership access control mechanism
contract HasOwners is Validating {

  address[] public owners;
  mapping(address => bool) public isOwner;

  event OwnerAdded(address indexed owner);
  event OwnerRemoved(address indexed owner);

  /// @notice initializing the owners list (with at least one owner)
  constructor(address[] memory owners_) {
    require(owners_.length > 0, "there must be at least one owner");
    for (uint i = 0; i < owners_.length; i++) addOwner_(owners_[i]);
  }

  /// @notice requires the sender to be one of the contract owners
  modifier onlyOwner { require(isOwner[msg.sender], "invalid sender; must be owner"); _; }

  /// @notice list all accounts with an owner access
  function getOwners() public view returns (address[] memory) { return owners; }

  /// @notice authorize an `account` with owner access
  function addOwner(address owner) external onlyOwner { addOwner_(owner); }

  function addOwner_(address owner) private validAddress(owner) {
    if (!isOwner[owner]) {
      isOwner[owner] = true;
      owners.push(owner);
      emit OwnerAdded(owner);
    }
  }

  /// @notice revoke an `account` owner access (while ensuring at least one owner remains)
  function removeOwner(address owner) external onlyOwner {
    require(isOwner[owner], 'only owners can be removed');
    require(owners.length > 1, 'can not remove last owner');
    isOwner[owner] = false;
    for (uint i = 0; i < owners.length; i++) {
      if (owners[i] == owner) {
        owners[i] = owners[owners.length - 1];
        owners.pop();
        emit OwnerRemoved(owner);
        break;
      }
    }
  }

}

// File: contracts/gluon/HasAppOwners.sol

pragma solidity 0.7.1;



/// @notice providing a per-app ownership access control
contract HasAppOwners is HasOwners {

  mapping(uint32 => address[]) public appOwners;

  event AppOwnerAdded (uint32 appId, address appOwner);
  event AppOwnerRemoved (uint32 appId, address appOwner);

  constructor(address[] memory owners_) HasOwners(owners_) { }

  /// @notice requires the sender to be one of the app owners (of `appId`)
  ///
  /// @param appId index of the target app
  modifier onlyAppOwner(uint32 appId) { require(isAppOwner(appId, msg.sender), "invalid sender; must be app owner"); _; }

  function isAppOwner(uint32 appId, address appOwner) public view returns (bool) {
    address[] memory currentOwners = appOwners[appId];
    for (uint i = 0; i < currentOwners.length; i++) {
      if (currentOwners[i] == appOwner) return true;
    }
    return false;
  }

  /// @notice list all accounts with an app-owner access for `appId`
  ///
  /// @param appId index of the target app
  function getAppOwners(uint32 appId) public view returns (address[] memory) { return appOwners[appId]; }

  function addAppOwners(uint32 appId, address[] calldata toBeAdded) external onlyAppOwner(appId) {
    addAppOwners_(appId, toBeAdded);
  }

  /// @notice authorize each of `toBeAdded` with app-owner access
  ///
  /// @param appId index of the target app
  /// @param toBeAdded accounts to be authorized
  /// (the initial app-owners are established during app registration)
  function addAppOwners_(uint32 appId, address[] memory toBeAdded) internal {
    for (uint i = 0; i < toBeAdded.length; i++) {
      if (!isAppOwner(appId, toBeAdded[i])) {
        appOwners[appId].push(toBeAdded[i]);
        emit AppOwnerAdded(appId, toBeAdded[i]);
      }
    }
  }


  /// @notice revokes app-owner access for each of `toBeRemoved` (while ensuring at least one app-owner remains)
  ///
  /// @param appId index of the target app
  /// @param toBeRemoved accounts to have their membership revoked
  function removeAppOwners(uint32 appId, address[] calldata toBeRemoved) external onlyAppOwner(appId) {
    address[] storage currentOwners = appOwners[appId];
    require(currentOwners.length > toBeRemoved.length, "can not remove last owner");
    for (uint i = 0; i < toBeRemoved.length; i++) {
      for (uint j = 0; j < currentOwners.length; j++) {
        if (currentOwners[j] == toBeRemoved[i]) {
          currentOwners[j] = currentOwners[currentOwners.length - 1];
          currentOwners.pop();
          emit AppOwnerRemoved(appId, toBeRemoved[i]);
          break;
        }
      }
    }
  }

}

// File: contracts/gluon/Gluon.sol

pragma solidity 0.7.1;











/**
  * @title the Gluon-Plasma contract for upgradable side-chain apps (see: https://leverj.io/GluonPlasma.pdf)
  * @notice once an app has been provisioned with me, I enable:
  * - depositing an asset into an app
  * - withdrawing an asset from an app
  * - transferring an asset across apps
  * - submitting (and discarding) an upgrade proposal for an app
  * - voting for/against app proposals
  * - upgrading an approved app proposal
  */
contract Gluon is Validating, Versioned, AppGovernance, GluonWallet, HasAppOwners {
  using SafeMath for uint;

  struct App {
    address[] history;
    address proposal;
    uint activationBlock;
    mapping(address => uint) balances;
  }

  address private constant ETH = address(0x0);
  uint32 private constant REGISTRY_INDEX = 0;
  uint32 private constant STAKE_INDEX = 1;

  mapping(uint32 => App) public apps;
  mapping(address => bool) public proposals;
  uint32 public totalAppsCount = 0;

  event AppRegistered (uint32 appId);
  event AppProvisioned(uint32 indexed appId, uint8 version, address logic);
  event ProposalAdded(uint32 indexed appId, uint8 version, address logic, uint activationBlock);
  event ProposalRemoved(uint32 indexed appId, uint8 version, address logic);
  event Activated(uint32 indexed appId, uint8 version, address logic);

  constructor(address[] memory owners_, string memory version_) Versioned(version_) HasAppOwners(owners_) {
    registerApp_(REGISTRY_INDEX, owners);
    registerApp_(STAKE_INDEX, owners);
  }

  /// @notice requires the sender to be the currently active (latest) version of the app contract (identified by appId)
  ///
  /// @param appId index of the provisioned app in question
  modifier onlyCurrentLogic(uint32 appId) { require(msg.sender == current(appId), "invalid sender; must be latest logic contract"); _; }

  modifier provisioned(uint32 appId) { require(apps[appId].history.length > 0, "App is not yet provisioned"); _; }

  function registerApp(uint32 appId, address[] calldata accounts) external onlyOwner { registerApp_(appId, accounts); }

  function registerApp_(uint32 appId, address[] memory accounts) private {
    require(appOwners[appId].length == 0, "App already has app owner");
    require(totalAppsCount == appId, "app ids are incremented by 1");
    totalAppsCount++;
    emit AppRegistered(appId);
    addAppOwners_(appId, accounts);
  }

  /// @notice on-boarding an app
  ///
  /// @param logic address of the app's contract (the first version)
  /// @param appId index of the provisioned app in question
  function provisionApp(uint32 appId, address logic) external onlyAppOwner(appId) validAddress(logic) {
    App storage app = apps[appId];
    require(app.history.length == 0, "App is already provisioned");
    app.history.push(logic);
    emit AppProvisioned(appId, uint8(app.history.length - 1), logic);
  }

  /************************************************* Governance ************************************************/

  function addProposal(uint32 appId, address logic) external onlyAppOwner(appId) provisioned(appId) validAddress(logic) {
    App storage app = apps[appId];
    require(app.proposal == address(0x0), "Proposal already exists. remove proposal before adding new one");
    app.proposal = logic;
    app.activationBlock = block.number + Governing(current(STAKE_INDEX)).activationInterval();
    proposals[logic] = true;
    emit ProposalAdded(appId, uint8(app.history.length - 1), app.proposal, app.activationBlock);
  }

  function removeProposal(uint32 appId) external onlyAppOwner(appId) provisioned(appId) {
    App storage app = apps[appId];
    emit ProposalRemoved(appId, uint8(app.history.length - 1), app.proposal);
    deleteProposal(app);
  }

  function deleteProposal(App storage app) private {
    Governing(current(STAKE_INDEX)).deleteVoteTally(app.proposal);
    delete proposals[app.proposal];
    delete app.proposal;
    app.activationBlock = 0;
  }

  /************************************************* AppGovernance ************************************************/

  function approve(uint32 appId) external override onlyCurrentLogic(STAKE_INDEX) {
    apps[appId].activationBlock = block.number;
  }

  function disapprove(uint32 appId) external override onlyCurrentLogic(STAKE_INDEX) {
    App storage app = apps[appId];
    emit ProposalRemoved(appId, uint8(app.history.length - 1), app.proposal);
    deleteProposal(app);
  }

  function activate(uint32 appId) external override onlyCurrentLogic(appId) provisioned(appId) {
    App storage app = apps[appId];
    require(app.activationBlock > 0, "nothing to activate");
    require(app.activationBlock < block.number, "new app can not be activated before activation block");
    app.history.push(app.proposal); // now make it the current
    deleteProposal(app);
    emit Activated(appId, uint8(app.history.length - 1), current(appId));
  }

  /**************************************************** GluonWallet ****************************************************/

  /// @notice deposit ETH asset on behalf of the sender into an app's safe
  ///
  /// @param appId index of the target app
  function depositEther(uint32 appId) external override payable provisioned(appId) {
    App storage app = apps[appId];
    app.balances[ETH] = app.balances[ETH].add(msg.value);
    AppLogic(current(appId)).credit(msg.sender, ETH, msg.value);
  }

  /// @notice deposit ERC20 token asset (represented by address 0x0) on behalf of the sender into an app's safe
  /// @dev an account must call token.approve(logic, quantity) beforehand
  ///
  /// @param appId index of the target app
  /// @param token address of ERC20 token contract
  /// @param quantity how much of token
  function depositToken(uint32 appId, address token, uint quantity) external override provisioned(appId) {
    transferTokensToGluonSecurely(appId, IERC20(token), quantity);
    AppLogic(current(appId)).credit(msg.sender, token, quantity);
  }

  function transferTokensToGluonSecurely(uint32 appId, IERC20 token, uint quantity) private {
    uint balanceBefore = token.balanceOf(address(this));
    require(token.transferFrom(msg.sender, address(this), quantity), "failure to transfer quantity from token");
    uint balanceAfter = token.balanceOf(address(this));
    require(balanceAfter.sub(balanceBefore) == quantity, "bad Token; transferFrom erroneously reported of successful transfer");
    App storage app = apps[appId];
    app.balances[address(token)] = app.balances[address(token)].add(quantity);
  }

  /// @notice withdraw a quantity of asset from an app's safe
  /// @dev quantity & asset should be derived by the app
  ///
  /// @param appId index of the target app
  /// @param parameters a bytes-marshalled record containing at the very least quantity & asset
  function withdraw(uint32 appId, bytes calldata parameters) external override provisioned(appId) {
    (address asset, uint quantity) = AppLogic(current(appId)).debit(msg.sender, parameters);
    if (quantity > 0) {
      App storage app = apps[appId];
      require(app.balances[asset] >= quantity, "not enough funds to transfer");
      app.balances[asset] = apps[appId].balances[asset].sub(quantity);
      asset == ETH ?
        require(address(uint160(msg.sender)).send(quantity), "failed to transfer ether") : // explicit casting to `address payable`
        transferTokensToAccountSecurely(IERC20(asset), quantity, msg.sender);
    }
  }

  function transferTokensToAccountSecurely(IERC20 token, uint quantity, address to) private {
    uint balanceBefore = token.balanceOf(to);
    require(token.transfer(to, quantity), "failure to transfer quantity from token");
    uint balanceAfter = token.balanceOf(to);
    require(balanceAfter.sub(balanceBefore) == quantity, "bad Token; transferFrom erroneously reported of successful transfer");
  }

  /// @notice withdraw a quantity of asset from a source app's safe and transfer it (within Gluon) to a target app's safe
  /// @dev quantity & asset should be derived by the source app
  ///
  /// @param from index of the source app
  /// @param to index of the target app
  /// @param parameters a bytes-marshalled record containing at the very least quantity & asset
  function transfer(uint32 from, uint32 to, bytes calldata parameters) external override provisioned(from) provisioned(to) {
    (address asset, uint quantity) = AppLogic(current(from)).debit(msg.sender, parameters);
    if (quantity > 0) {
      if (from != to) {
        require(apps[from].balances[asset] >= quantity, "not enough balance in logic to transfer");
        apps[from].balances[asset] = apps[from].balances[asset].sub(quantity);
        apps[to].balances[asset] = apps[to].balances[asset].add(quantity);
      }
      AppLogic(current(to)).credit(msg.sender, asset, quantity);
    }
  }

  /**************************************************** GluonView  ****************************************************/

  /// @notice view of current app data
  ///
  /// @param appId index of the provisioned app in question
  /// @return current address of the app's current contract
  /// @return proposal address of the app's pending proposal contract (if any)
  /// @return activationBlock the block in which the proposal can be activated
  function app(uint32 appId) external view returns (address current, address proposal, uint activationBlock) {
    App storage app_ = apps[appId];
    current = app_.history[app_.history.length - 1];
    proposal = app_.proposal;
    activationBlock = app_.activationBlock;
  }

  function current(uint32 appId) public view returns (address) { return apps[appId].history[apps[appId].history.length - 1]; }

  /// @notice view of the full chain of (contract addresses) of the app versions, up to and including the current one
  function history(uint32 appId) external view returns (address[] memory) { return apps[appId].history; }

  /// @notice is the `logic` contract one of the `appId` app?
  function isAnyLogic(uint32 appId, address logic) public view returns (bool) {
    address[] memory history_ = apps[appId].history;
    for (uint i = history_.length; i > 0; i--) {
      if (history_[i - 1] == logic) return true;
    }
    return false;
  }

  /// @notice what is the current balance of `asset` in the `appId` app's safe?
  function getBalance(uint32 appId, address asset) external view returns (uint) { return apps[appId].balances[asset]; }

}

// File: contracts/gluon/GluonCentric.sol

pragma solidity 0.7.1;



/**
  * @title the essentials of a side-chain app participating in Gluon-Plasma
  * @dev both Logic & Data (if exists) contracts should inherit this contract
  */
contract GluonCentric {

  uint32 internal constant REGISTRY_INDEX = 0;
  uint32 internal constant STAKE_INDEX = 1;

  uint32 public id;
  Gluon public gluon;

  /// @param id_ index of the app within gluon
  /// @param gluon_ address of the Gluon contract
  constructor(uint32 id_, address gluon_) {
    id = id_;
    gluon = Gluon(gluon_);
  }

  /// @notice requires the sender to be the currently active (latest) version of me (the app contract)
  modifier onlyCurrentLogic { require(currentLogic() == msg.sender, "invalid sender; must be current logic contract"); _; }

  /// @notice requires the sender must be gluon contract
  modifier onlyGluon { require(address(gluon) == msg.sender, "invalid sender; must be gluon contract"); _; }

  /// @notice requires the sender must be my app owner
  modifier onlyOwner { require(gluon.isAppOwner(id, msg.sender), "invalid sender; must be app owner"); _; }

  /// @return address the address of currently active (latest) version of me (the app contract)
  function currentLogic() public view returns (address) { return gluon.current(id); }

}

// File: contracts/gluon/GluonLogic.sol

pragma solidity 0.7.1;




abstract contract GluonLogic is GluonCentric {
  address public upgradeOperator;

  constructor(uint32 id_, address gluon_) GluonCentric(id_, gluon_) { }

  modifier onlyUpgradeOperator { require(upgradeOperator == msg.sender, "invalid sender; must be upgrade operator"); _; }

  function setUpgradeOperator(address upgradeOperator_) external onlyOwner { upgradeOperator = upgradeOperator_; }

  function upgrade_(AppGovernance appGovernance, uint32 id) internal {
    appGovernance.activate(id);
    delete upgradeOperator;
  }
}

// File: contracts/apps_history/registry/OldRegistry.sol

pragma solidity 0.7.1;


interface OldRegistry {
  function contains(address apiKey) external view returns (bool);
  function register(address apiKey) external;
  function registerWithUserAgreement(address apiKey, bytes32 userAgreement) external;
  function translate(address apiKey) external view returns (address);
}

// File: contracts/apps/registry/RegistryData.sol

pragma solidity 0.7.1;



contract RegistryData is GluonCentric {

  mapping(address => address) public accounts;

  constructor(address gluon_) GluonCentric(REGISTRY_INDEX, gluon_) { }

  function addKey(address apiKey, address account) external onlyCurrentLogic {
    accounts[apiKey] = account;
  }

}

// File: contracts/apps/registry/RegistryLogic.sol

pragma solidity 0.7.1;









/**
  * @title enabling Zero Knowledge API Keys as described in: https://blog.leverj.io/zero-knowledge-api-keys-43280cc93647
  * @notice the Registry app consists of the RegistryLogic & RegistryData contracts.
  * api-key registrations are held within RegistryData for an easier upgrade path.
  * @dev although Registry enable account-based apps needing log-less logins, no app is required to use it.
  */
contract RegistryLogic is Validating, AppLogic, AppState, GluonLogic {

  RegistryData public data;
  OldRegistry public old;

  event Registered(address apiKey, address indexed account);

  constructor(address gluon_, address old_, address data_) GluonLogic(REGISTRY_INDEX, gluon_) {
    data = RegistryData(data_);
    old = OldRegistry(old_);
  }

  modifier isAbsent(address apiKey) { require(translate(apiKey) == address (0x0), "api key already in use"); _; }

  /// @notice register an api-key on behalf of the sender
  /// @dev irreversible operation; the apiKey->sender association cannot be broken or overwritten
  /// (but further apiKey->sender associations can be provided)
  ///
  /// @param apiKey the account to be used to stand-in for the registering sender
  function register(address apiKey) external whenOn validAddress(apiKey) isAbsent(apiKey) {
    data.addKey(apiKey, msg.sender);
    emit Registered(apiKey, msg.sender);
  }

  /// @notice retrieve the stand-in-for account
  ///
  /// @param apiKey the account to be used to stand-in for the registering sender
  function translate(address apiKey) public view returns (address) {
    address account = data.accounts(apiKey);
    if (account == address(0x0)) account = old.translate(apiKey);
    return account;
  }

  /**************************************************** AppLogic ****************************************************/

  /// @notice upgrade the app to a new version; the approved proposal.
  /// by the end of this call the approved proposal would be the current and active version of the app.
  function upgrade() external override onlyUpgradeOperator {
    retire_();
    upgrade_(AppGovernance(gluon), id);
  }

  function credit(address, address, uint) external override pure { revert("not supported"); }

  function debit(address, bytes calldata) external override pure returns (address, uint) { revert("not supported"); }

  /***************************************************** AppState *****************************************************/

  /// @notice halt the app. this action is irreversible.
  /// (the only option at this point is have a proposal that will get to approval, then activated.)
  /// should be called by an app-owner when the app has been compromised.
  ///
  /// Note the constraint that all apps but Registry & Stake must be halted first!
  function switchOff() external onlyOwner {
    uint32 totalAppsCount = gluon.totalAppsCount();
    for (uint32 i = 2; i < totalAppsCount; i++) {
      AppState appState = AppState(gluon.current(i));
      require(!appState.isOn(), "One of the apps is still ON");
    }
    switchOff_();
  }

  /********************************************************************************************************************/
}

// File: contracts/apps/stake/Redeeming.sol

pragma solidity 0.7.1;


interface Redeeming {
  function redeem(address account, uint quantity) external returns (uint toRestake, uint toStake, uint toWithdraw);
}

// File: contracts/apps/stake/StakeData.sol

pragma solidity 0.7.1;




contract StakeData is GluonCentric {
  using SafeMath for uint;

  mapping(address => address[]) public accountToProposals;
  mapping(address => bool[]) public accountToSides;
  mapping(address => mapping(bool => uint)) public voteTally; /// proposal => side(true/false) => totalVotes
  mapping(address => address) public accountLocation;         /// account => logic
  mapping(address => uint) public balance;

  constructor(address gluon) GluonCentric(STAKE_INDEX, gluon) { }

  function updateAccountLocation(address account, address logic) external onlyCurrentLogic { accountLocation[account] = logic; }

  function updateBalance(address account, uint quantity) external onlyCurrentLogic { balance[account] = quantity; }

  function voteAppUpgrade(address proposal, address account, bool side, uint quantity) external onlyCurrentLogic returns (uint, uint) {
    uint index = getVoteIndex(account, proposal);
    bool firstVote = index == accountToProposals[account].length;
    require(firstVote || accountToSides[account][index] != side, "cannot vote same side again");
    if (firstVote) {
      accountToProposals[account].push(proposal);
      accountToSides[account].push(side);
    } else {
      voteTally[proposal][!side] = voteTally[proposal][!side].sub(quantity);
      accountToSides[account][index] = side;
    }
    voteTally[proposal][side] = voteTally[proposal][side].add(quantity);
    return getVoteTally(proposal);
  }

  function deleteVoteTally(address proposal) external onlyCurrentLogic {
    voteTally[proposal][true] = voteTally[proposal][false] = 0;
  }

  function getVoteIndex(address account, address proposal) public view returns (uint) {
    address[] memory proposals = accountToProposals[account];
    for (uint i = 0; i < proposals.length; i++) {
      if (proposals[i] == proposal) return i;
    }
    return proposals.length;
  }

  function getAllProposals(address account) external view returns (address[] memory proposals, bool[] memory sides) {
    proposals = accountToProposals[account];
    sides = accountToSides[account];
  }

  function removeResolvedProposals(address account) external onlyCurrentLogic {
    if (accountToProposals[account].length == 0) return;
    address[] storage allProposed = accountToProposals[account];
    bool[] storage sides = accountToSides[account];
    for (uint i = allProposed.length; i > 0; i--) {
      if (!gluon.proposals(allProposed[i - 1])) {
        allProposed[i - 1] = allProposed[allProposed.length - 1];
        allProposed.pop();
        sides[i - 1] = sides[sides.length - 1];
        sides.pop();
      }
    }
  }

  function updateVotes(address proposal, bool side, uint quantity, bool increased) external onlyCurrentLogic returns (uint approvals, uint disapprovals) {
    uint tally = voteTally[proposal][side];
    voteTally[proposal][side] = increased ? tally.add(quantity) : tally.sub(quantity);
    return getVoteTally(proposal);
  }

  function getVoteTally(address proposal) public view returns (uint approvals, uint disapprovals) {
    approvals = voteTally[proposal][true];
    disapprovals = voteTally[proposal][false];
  }

}

// File: contracts/apps/stake/StakeLogic.sol

pragma solidity 0.7.1;














/**
  * @notice the Stake app consists of the StakeLogic & StakeData contracts.
  * voting data and staked balances are held within StakeData for an easier upgrade path.
  *
  * staking governanceToken tokens allows for:
  *  a. distribution of awards to stakers
  *  b. governance of apps; as stakers can vote for or against proposals (proposed app upgrades)
  */
contract StakeLogic is Validating, AppLogic, AppState, GluonLogic, Governing, Redeeming {
  using BytesLib for bytes;
  using SafeMath for uint;

  /// per stake interval data
  struct Interval {
    uint worth;
    uint[] rewards;
    uint start;
    uint end;
  }

  /// account
  struct UserStake {
    uint intervalIndex;
    uint quantity;
    uint worth;
  }

  address constant private ETH = address(0x0);
  uint public constant name = uint(keccak256("StakeLogic"));
  bool initiated;
  StakeData public data;
  address public override governanceToken;
  address[] public tokens;
  uint[] public toBeDistributed;

  uint public intervalSize;
  uint public currentIntervalIndex;
  uint public quorumPercentage;
  uint public override activationInterval;
  mapping(uint => Interval) public intervals;
  mapping(address => UserStake) public stakes;

  event Staked(address indexed user, uint quantity, uint start, uint end, uint intervalIndex);
  event Restaked(address indexed user, uint quantity, uint start, uint end, uint intervalIndex);
  event Redeemed(address indexed user, uint quantity, uint start, uint end, uint intervalIndex);
  event Reward(address indexed user, address asset, uint reward, uint start, uint end, uint intervalIndex);
  event NewInterval(uint start, uint end, uint intervalIndex);
  event Voted(uint32 indexed appId, address indexed proposal, uint approvals, uint disapprovals, address account);
  event VotingConcluded(uint32 indexed appId, address indexed proposal, uint approvals, uint disapprovals, bool result);

  constructor(address gluon_, address data_, address governanceToken_, address[] memory tokens_, address apiKey_, uint intervalSize_, uint quorumPercentage_, uint activationInterval_)
    GluonLogic(STAKE_INDEX, gluon_)
    validAddress(gluon_)
    validAddress(governanceToken_)
    validAddress(apiKey_)
    notZero(intervalSize_)
    notZero(activationInterval_)
  {
    data = StakeData(data_);
    governanceToken = governanceToken_;
    tokens = tokens_;
    for (uint i = 0; i < tokens.length; i++) toBeDistributed.push(0);
    quorumPercentage = quorumPercentage_;
    intervalSize = intervalSize_;
    registerApiKey_(apiKey_);
    activationInterval = activationInterval_;
  }

  receive() external payable {}

  function init(uint intervalId) external onlyOwner {
    require(initiated == false, "already initiated");
    currentIntervalIndex = intervalId;
    intervals[currentIntervalIndex].start = block.number;
    intervals[currentIntervalIndex].end = block.number.add(intervalSize);
    for (uint i = 0; i < tokens.length; i++) intervals[currentIntervalIndex].rewards.push(0);
    initiated = true;
  }

  function setIntervalSize(uint intervalSize_) external notZero(intervalSize_) onlyOwner {
    ensureInterval();
    intervalSize = intervalSize_;
  }

  function addToken(address token) external validAddress(token) onlyOwner whenOn {
    require(tokens.length < 50, "Can not add more than 50 tokens");
    tokens.push(token);
    toBeDistributed.push(0);
    intervals[currentIntervalIndex].rewards.push(0);
  }

  /// @notice establish an interval if none exists
  function ensureInterval() public whenOn {
    if (intervals[currentIntervalIndex].end > block.number) return;

    Interval storage interval = intervals[currentIntervalIndex];
    for (uint i = 0; i < interval.rewards.length; i++) {
      uint reward = interval.worth == 0 ? 0 : calculateIntervalReward(interval.start, interval.end, i);
      toBeDistributed[i] = toBeDistributed[i].add(reward);
      interval.rewards[i] = reward;
    }

    uint diff = block.number.sub(interval.end) % intervalSize;
    currentIntervalIndex += 1;
    uint start = interval.end;
    uint end = block.number.sub(diff).add(intervalSize);
    intervals[currentIntervalIndex].start = start;
    intervals[currentIntervalIndex].end = end;
    for (uint i = 0; i < tokens.length; i++) intervals[currentIntervalIndex].rewards.push(0);
    emit NewInterval(start, end, currentIntervalIndex);
  }

  function restake(address account, uint quantity) private returns (uint, uint) {
    (uint toRestake, uint toStake, uint toWithdraw) = Redeeming(stakeLocation(account)).redeem(account, quantity);
    if (toRestake == 0) return (toStake, toWithdraw);

    UserStake storage stake = stakes[account];
    stake.quantity = toRestake;
    Interval storage interval = intervals[currentIntervalIndex];
    stake.intervalIndex = currentIntervalIndex;
    stake.worth = stake.quantity.mul(interval.end.sub(interval.start));
    interval.worth = interval.worth.add(stake.worth);
    emit Restaked(account, stake.quantity, interval.start, interval.end, currentIntervalIndex);
    return (toStake, toWithdraw);
  }

  function stake(address account, uint quantity) private whenOn returns (uint toStake, uint toWithdraw) {
    ensureInterval();
    (toStake, toWithdraw) = restake(account, quantity);
    data.removeResolvedProposals(account);
    if (toWithdraw > 0) {
      updateVotes(account, toWithdraw, false);
    }
    if (toStake > 0) {
      updateVotes(account, toStake, true);
      stakeInCurrentPeriod(account, toStake);
    }
    data.updateBalance(account, quantity);
    data.updateAccountLocation(account, stakes[account].worth == 0 ? address(0x0) : address(this));
  }

  function stakeInCurrentPeriod(address account, uint quantity) private {
    Interval storage interval = intervals[currentIntervalIndex];
    stakes[account].intervalIndex = currentIntervalIndex;
    uint worth = quantity.mul(interval.end.sub(block.number));
    stakes[account].worth = stakes[account].worth.add(worth);
    stakes[account].quantity = stakes[account].quantity.add(quantity);
    interval.worth = interval.worth.add(worth);
    emit Staked(account, quantity, interval.start, interval.end, currentIntervalIndex);
  }

  /// @notice calculate the reward for token for the interval: [`start`, `end`)
  /// provided for on-going operational queries
  function calculateIntervalReward(uint start, uint end, uint index) public view returns (uint) {
    uint balance = tokens[index] == ETH ? address(this).balance : IERC20(tokens[index]).balanceOf(address(this));
    return balance.sub(toBeDistributed[index]).mul(end.sub(start)).div(block.number.sub(start));
  }

  function registerApiKey(address apiKey) public onlyOwner { registerApiKey_(apiKey); }

  function registerApiKey_(address apiKey) private {
    RegistryLogic registry = RegistryLogic(gluon.current(REGISTRY_INDEX));
    registry.register(apiKey);
  }

  function withdrawFromApp(uint32 appId, bytes memory withdrawData) public {
    uint action = withdrawData.toUint(0);
    require(action == 1 || action == 5, "only assisted withdraw or exit on halt is allowed");
    GluonWallet(gluon).withdraw(appId, withdrawData);
  }

  function transferToLatestStakeAfterRetire() public whenRetired {
    for (uint i = 0; i < tokens.length; i++) {
      uint balance = tokens[i] == ETH ? address(this).balance : IERC20(tokens[i]).balanceOf(address(this));
      uint quantity = balance.sub(toBeDistributed[i]);
      transfer(tokens[i], currentLogic(), quantity);
    }
  }

  /**************************************************** Redeeming *****************************************************/

  /// @notice redeeming enables both withdrawing and restaking.
  /// first, the quantities {toRestake, toStake, toWithdraw} are calculated from the last staked amount and the given quantity
  /// to redeem, then `toWithdraw` will be transfer to the account, and `toRestake` will be staked in the current interval.
  /// the calculated values are returned to calling functions for further processing.
  ///
  /// @param account the staking account
  /// @param quantity how much to redeem
  /// @return toRestake how much of the staked amount from previously staked interval will be carried over to current stake interval
  /// @return toStake how much (beyond toRestake) will be staked for the remainder of the current interval
  /// @return toWithdraw how much would no longer be staked and instead transferred back to the staker account
  function redeem(address account, uint quantity) public override onlyCurrentLogic returns (uint /* toRestake */, uint  /* toStake */, uint  /* toWithdraw */) {
    UserStake memory userStake = stakes[account];
    if (userStake.intervalIndex == 0) return (0, quantity, 0);
    // non staked thus far, so stake quantity in full

    uint staked = userStake.quantity;
    uint intervalIndex = userStake.intervalIndex;
    Interval memory interval = intervals[intervalIndex];
    uint toWithdraw = staked > quantity ? staked.sub(quantity) : 0;
    if (intervalIndex == currentIntervalIndex) {
      if (toWithdraw > 0) {
        // => quantity > staked
        uint worth = toWithdraw.mul(intervals[currentIntervalIndex].end.sub(block.number));
        stakes[account].worth = userStake.worth.sub(worth);
        stakes[account].quantity = userStake.quantity.sub(toWithdraw);
        intervals[currentIntervalIndex].worth = intervals[currentIntervalIndex].worth.sub(worth);
        emit Redeemed(account, toWithdraw, interval.start, interval.end, intervalIndex);
        return (0, 0, toWithdraw);
      } else {
        // => quantity <= staked
        uint toStake = quantity.sub(staked); // some is already staked, so stake the difference
        return (0, toStake, 0);
      }
    }

    // some is staked in previous interval
    uint toRestake = staked.sub(toWithdraw);
    // staker get previous staked amount carried over to current interval (minus the withdrawn amount)
    uint toStake = quantity > staked ? quantity.sub(staked) : 0;
    // staker get the extra amount (beyond what is already carried over) staked in the remainder of current interval
    uint worth = userStake.worth;
    delete stakes[account];
    distributeRewards(account, worth, interval, intervalIndex);
    emit Redeemed(account, toWithdraw, interval.start, interval.end, intervalIndex);
    return (toRestake, toStake, toWithdraw);
  }

  function distributeRewards(address account, uint worth, Interval memory interval, uint intervalIndex) private {
    if (worth == 0) return;

    for (uint i = 0; i < tokens.length; i++) {
      uint reward = interval.rewards[i].mul(worth).div(interval.worth);
      if (reward == 0) continue;
      toBeDistributed[i] = toBeDistributed[i].sub(reward);
      transfer(tokens[i], account, reward);
      emit Reward(account, tokens[i], reward, interval.start, interval.end, intervalIndex);
    }
  }

  function transfer(address token, address to, uint quantity) private {
    if (quantity == 0) return;

    token == ETH ?
      require(address(uint160(to)).send(quantity), "failed to transfer ether") : // explicit casting to `address payable`
      transferTokensToAccountSecurely(IERC20(token), quantity, to);
  }

  function transferTokensToAccountSecurely(IERC20 token, uint quantity, address to) private {
    uint balanceBefore = token.balanceOf(to);
    require(token.transfer(to, quantity), "failure to transfer quantity from token");
    uint balanceAfter = token.balanceOf(to);
    require(balanceAfter.sub(balanceBefore) == quantity, "bad Token; transferFrom erroneously reported of successful transfer");
  }

  function getTokens() public view returns (address[] memory) { return tokens; }

  function getToBeDistributed() public view returns (uint[] memory) { return toBeDistributed; }

  function getInterval(uint intervalIndex) public view returns (uint worth, uint[] memory rewards, uint start, uint end) {
    Interval memory interval = intervals[intervalIndex];
    worth = interval.worth;
    rewards = interval.rewards;
    start = interval.start;
    end = interval.end;
  }

  /**************************************************** Governing ****************************************************/

  /// @dev cleanup when deleting a proposal
  function deleteVoteTally(address proposal) external override onlyGluon { data.deleteVoteTally(proposal); }

  /**************************************************** AppLogic ****************************************************/

  /// @notice upgrade the app to a new version; the approved proposal.
  /// by the end of this call the approved proposal would be the current and active version of the app.
  function upgrade() external override whenOn onlyUpgradeOperator {
    (, address proposal, uint activationBlock) = gluon.app(id);
    require(activationBlock > 0, "nothing to activate");
    address[] memory logics = gluon.history(id);
    require(proposal != address(this), "can not be the same contract");
    require(GluonCentric(proposal).id() == id, "invalid app id");
    for (uint i = 0; i < logics.length; i++) require(proposal != logics[i], "can not be old contract");
    require(StakeLogic(payable(proposal)).name() == name, "proposal name is different");
    intervals[currentIntervalIndex].end = block.number;
    ensureInterval();
    retire_();
    upgrade_(AppGovernance(gluon), id);
  }

  function stakeLocation(address account) public view returns (address) {
    address accountStakeLocation = data.accountLocation(account);
    if (accountStakeLocation == address(0x0) || accountStakeLocation == address(this)) return address(this);

    (, , uint worth) = StakeLogic(payable(accountStakeLocation)).stakes(account);
    return worth == 0 ?
      address(this) :       // this is a new staker
      accountStakeLocation; // this is an old staker that already withdrew their LEV from previous contract
  }

  function credit(address account, address asset, uint quantity) external override whenOn onlyGluon {
    require(address(governanceToken) == Governing(stakeLocation(account)).governanceToken(), "cannot stake new governance-token (L2) before all of old governance-token (LEV) are redeemed");
    require(asset == address(governanceToken), "can only stake governance-token (L2)");
    stake(account, data.balance(account).add(quantity));
  }

  function debit(address account, bytes calldata parameters) external override whenOn onlyGluon returns (address asset, uint quantity) {
    (asset, quantity) = abi.decode(parameters, (address, uint));
    address stakedGovernanceToken = Governing(stakeLocation(account)).governanceToken();
    bool newWorld = asset == address(governanceToken) && asset == stakedGovernanceToken;
    require(
      newWorld || /* old world */ asset != address(governanceToken) && asset == stakedGovernanceToken,
      "can only redeem new governance-token (L2) or all of old governance-token (LEV)"
    );
    if (newWorld) {
      stake(account, data.balance(account).sub(quantity));
    } else {
      require(data.balance(account) == quantity, "must redeem all of staked quantity");
      stake(account, 0);
    }
  }

  /***************************************************** vote to upgrade ****************************************************/

  /// @notice vote for the current app proposal
  ///
  /// @param appId the app the sender is voting for
  /// @param side yay or nay: true => approve, false => disapprove
  function voteAppUpgrade(uint32 appId, bool side) external whenOn {
    (, address proposal, uint activationBlock) = gluon.app(appId);
    require(activationBlock > block.number, "can not be voted");
    uint quantity = data.balance(msg.sender);
    (uint approvals, uint disapprovals) = data.voteAppUpgrade(proposal, msg.sender, side, quantity);
    emit Voted(appId, proposal, approvals, disapprovals, msg.sender);
    concludeVoting(appId, proposal, approvals, disapprovals);
  }

  function updateVotes(address account, uint quantity, bool increased) private {
    (address[] memory allProposed, bool[] memory sides) = data.getAllProposals(account);
    for (uint i; i < allProposed.length; i++) {
      uint32 appId = GluonCentric(allProposed[i]).id();
      (, , uint activationBlock) = gluon.app(appId);
      if (block.number > activationBlock) continue;
      (uint approvals, uint disapprovals) = data.updateVotes(allProposed[i], sides[i], quantity, increased);
      emit Voted(appId, allProposed[i], approvals, disapprovals, msg.sender);
      concludeVoting(appId, allProposed[i], approvals, disapprovals);
    }
  }

  function concludeVoting(uint32 appId, address proposal, uint approvals, uint disapprovals) private {
    if (approvals.add(disapprovals) >= IERC20(governanceToken).totalSupply().mul(quorumPercentage).div(100)) {
      if (approvals > disapprovals) {
        AppGovernance(gluon).approve(appId);
        emit VotingConcluded(appId, proposal, approvals, disapprovals, true);
      } else {
        AppGovernance(gluon).disapprove(appId);
        emit VotingConcluded(appId, proposal, approvals, disapprovals, false);
      }
    }
  }

  /***************************************************** halting *****************************************************/

  /// @notice halt the app. this action is irreversible.
  /// (the only option at this point is have a proposal that will get to approval, then activated.)
  /// should be called by an app-owner when the app has been compromised.
  ///
  /// Note the constraint that all apps but Registry & Stake must be halted first!
  function switchOff() external onlyOwner {
    uint32 totalAppsCount = gluon.totalAppsCount();
    for (uint32 appId = 2; appId < totalAppsCount; appId++) {
      AppState appState = AppState(gluon.current(appId));
      require(!appState.isOn(), "One of the apps is still ON");
    }
    switchOff_();
  }

  /********************************************************************************************************************/
}