// Contract: AsgardERC20Token
// Target function: function at(Bytes4Set storage set, uint256 index)
/**
 *Submitted for verification at Etherscan.io on 2021-03-21
 */

// SPDX-License-Identifier: AGPL-3.0-or-later
pragma solidity 0.7.5;

/**
 * @dev Intended to update the TWAP for a token based on accepting an update call from that token.
 *  expectation is to have this happen in the _beforeTokenTransfer function of ERC20.
 *  Provides a method for a token to register its price sourve adaptor.
 *  Provides a function for a token to register its TWAP updater. Defaults to token itself.
 *  Provides a function a tokent to set its TWAP epoch.
 *  Implements automatic closeing and opening up a TWAP epoch when epoch ends.
 *  Provides a function to report the TWAP from the last epoch when passed a token address.
 */
interface ITWAPOracle {
    function uniV2CompPairAddressForLastEpochUpdateBlockTimstamp(address)
        external
        returns (uint32);

    function priceTokenAddressForPricingTokenAddressForLastEpochUpdateBlockTimstamp(
        address tokenToPrice_,
        address tokenForPriceComparison_,
        uint256 epochPeriod_
    ) external returns (uint32);

    function pricedTokenForPricingTokenForEpochPeriodForPrice(
        address,
        address,
        uint256
    ) external returns (uint256);

    function pricedTokenForPricingTokenForEpochPeriodForLastEpochPrice(
        address,
        address,
        uint256
    ) external returns (uint256);

    function updateTWAP(
        address uniV2CompatPairAddressToUpdate_,
        uint256 eopchPeriodToUpdate_
    ) external returns (bool);
}

library EnumerableSet {
    // To implement this library for multiple types with as little code
    // repetition as possible, we write it in terms of a generic Set type with
    // bytes32 values.
    // The Set implementation uses private functions, and user-facing
    // implementations (such as AddressSet) are just wrappers around the
    // underlying Set.
    // This means that we can only create new EnumerableSets for types that fit
    // in bytes32.
    struct Set {
        // Storage of set values
        bytes32[] _values;
        // Position of the value in the `values` array, plus 1 because index 0
        // means a value is not in the set.
        mapping(bytes32 => uint256) _indexes;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function _add(Set storage set, bytes32 value) private returns (bool) {
        if (!_contains(set, value)) {
            set._values.push(value);
            // The value is stored at length-1, but we add 1 to all indexes
            // and use 0 as a sentinel value
            set._indexes[value] = set._values.length;
            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function _remove(Set storage set, bytes32 value) private returns (bool) {
        // We read and store the value's index to prevent multiple reads from the same storage slot
        uint256 valueIndex = set._indexes[value];

        if (valueIndex != 0) {
            // Equivalent to contains(set, value)
            // To delete an element from the _values array in O(1), we swap the element to delete with the last one in
            // the array, and then remove the last element (sometimes called as 'swap and pop').
            // This modifies the order of the array, as noted in {at}.

            uint256 toDeleteIndex = valueIndex - 1;
            uint256 lastIndex = set._values.length - 1;

            // When the value to delete is the last one, the swap operation is unnecessary. However, since this occurs
            // so rarely, we still do the swap anyway to avoid the gas cost of adding an 'if' statement.

            bytes32 lastvalue = set._values[lastIndex];

            // Move the last value to the index where the value to delete is
            set._values[toDeleteIndex] = lastvalue;
            // Update the index for the moved value
            set._indexes[lastvalue] = toDeleteIndex + 1; // All indexes are 1-based

            // Delete the slot where the moved value was stored
            set._values.pop();

            // Delete the index for the deleted slot
            delete set._indexes[value];

            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function _contains(Set storage set, bytes32 value)
        private
        view
        returns (bool)
    {
        return set._indexes[value] != 0;
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function _length(Set storage set) private view returns (uint256) {
        return set._values.length;
    }

    /**
     * @dev Returns the value stored at position `index` in the set. O(1).
     *
     * Note that there are no guarantees on the ordering of values inside the
     * array, and it may change when more values are added or removed.
     *
     * Requirements:
     *
     * - `index` must be strictly less than {length}.
     */
    function _at(Set storage set, uint256 index)
        private
        view
        returns (bytes32)
    {
        require(
            set._values.length > index,
            "EnumerableSet: index out of bounds"
        );
        return set._values[index];
    }

    function _getValues(Set storage set_)
        private
        view
        returns (bytes32[] storage)
    {
        return set_._values;
    }

    // TODO needs insert function that maintains order.
    // TODO needs NatSpec documentation comment.
    /**
     * Inserts new value by moving existing value at provided index to end of array and setting provided value at provided index
     */
    function _insert(
        Set storage set_,
        uint256 index_,
        bytes32 valueToInsert_
    ) private returns (bool) {
        require(set_._values.length > index_);
        require(
            !_contains(set_, valueToInsert_),
            "Remove value you wish to insert if you wish to reorder array."
        );
        bytes32 existingValue_ = _at(set_, index_);
        set_._values[index_] = valueToInsert_;
        return _add(set_, existingValue_);
    }

    struct Bytes4Set {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(Bytes4Set storage set, bytes4 value) internal returns (bool) {
        return _add(set._inner, value);
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(Bytes4Set storage set, bytes4 value)
        internal
        returns (bool)
    {
        return _remove(set._inner, value);
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(Bytes4Set storage set, bytes4 value)
        internal
        view
        returns (bool)
    {
        return _contains(set._inner, value);
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function length(Bytes4Set storage set) internal view returns (uint256) {
        return _length(set._inner);
    }