// File: @openzeppelin/contracts/access/Ownable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (access/Ownable.sol)

pragma solidity ^0.8.0;

import "../utils/Context.sol";

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby disabling any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @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);

    /**
     * @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 `to`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address to, 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 `from` to `to` 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 from, address to, uint256 amount) external returns (bool);
}

// File: @openzeppelin/contracts/utils/Context.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

pragma solidity ^0.8.0;

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}

// File: contracts/ISIN/SnapshotStorage.sol



// SPDX-License-Identifier: Apache-2.0

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/access/Ownable.sol";

import "../interfaces/ISnapshotStorage.sol";

contract SnapshotStorage is ISnapshotStorage, Ownable {

    // Token tracked by this contract
    address public token;
    // Address which is allowed to record snaphots
    address public authorizedContract;
    // Array of unique users
    address[] public userArray; 
    // Flag if the contract supports calculateUserNumberWithNonZeroTwab() 
    // and getUsersListWithNonZeroTwab() functions or not
    bool public supportListTwabFunctions;
    
    // Mapping if a user has interacted with protocol or not  
    mapping(address => bool) public knownUser;   
    // Balance snapshots for users
    mapping(address => Snapshot[]) private _snapshots;  

    constructor(address tokenAddress, address authorized, bool supportListTwab) {
        token = tokenAddress;
        authorizedContract = authorized;
        supportListTwabFunctions = supportListTwab;
    }

    /**
     * @notice Sets new token address
     * @param newToken New token address
     */
    function setToken(address newToken) external onlyOwner {
        token = newToken;
    }

    /**
     * @notice Sets new authorized address
     * @param newAuthorized New authorized address
     */
    function setAuthorized(address newAuthorized) external onlyOwner {
        authorizedContract = newAuthorized;
    }

    /**
     * @notice Returns snapshot of specified wallet at specified index
     * @param user The wallet address
     * @param index The index
     */
    function snapshots(address user, uint256 index) external view override returns(Snapshot memory) {
        require(index < _snapshots[user].length, "incorrect index");
        return _snapshots[user][index];
    }

    /**
     * @notice Returns amount of snapshots regarded to specified wallet
     * @param user The wallet address
     */
    function snapshotCount(address user) external view override returns(uint256) {
        return _snapshots[user].length;
    }

    /**
     * @notice Records balances snapshot using specified transfer parameters
     * @dev Only authorized contract can call it. Should be called BEFORE transfer
     * @param sender Token sender
     * @param recipient Token recipient
     * @param value Token amount
     */
    function takeSnapshot(address sender, address recipient, uint256 value) external override {
        require(msg.sender == authorizedContract, "SnaphotsStorage: Not authorized");
        _takeSnapshot(sender, recipient, value);
    }

    /**
     * @notice Returns number of unique users
     */
    function getUserArrayLength() external view returns(uint256) {
        return userArray.length;
    }

    /**
     * @notice Returns number of users with non-zero TWAB
     * @param start Start timestamp / block number 
     * @param end End timestamp / block number 
     * @param _type Type of the tracker (0 - block number, 1 - timestamp) 
     */
    function calculateUserNumberWithNonZeroTwab(
        uint256 start, 
        uint256 end, 
        TrackerType _type
    ) public view returns(
        uint256
    ) {
        if (!supportListTwabFunctions) return 0;
        uint256 length = userArray.length;   
        uint256 counter = 0;   
        for (uint256 i = 0; i < length; i++) {
            (uint256 twab, , ) = getAverageBalance(
                userArray[i],
                start,
                end,
                _type
            );
            if (twab > 0) counter++;
        }
        return counter;
    }

    /**
     * @notice Returns the list of users with non-zero TWAB
     * @param start Start timestamp / block number 
     * @param end End timestamp / block number 
     * @param _type Type of the tracker (0 - block number, 1 - timestamp) 
     * @param number Number of non-zero TWAB users
     */
    function getUsersListWithNonZeroTwab(
        uint256 start, 
        uint256 end, 
        TrackerType _type,
        uint256 number
    ) public view returns(
        UserOutput[] memory
    ) {
        if (!supportListTwabFunctions) return new UserOutput[](0);
        address[] memory array = userArray;
        uint256 length = array.length;
        UserOutput[] memory userOutputArray = new UserOutput[](number);
        uint256 index = 0;
        for (uint256 i = 0; i < length; i++) {
            (uint256 twab, , ) = getAverageBalance(
                array[i],
                start,
                end,
                _type
            );
            if (twab > 0) {
                userOutputArray[index] = UserOutput(array[i], twab);
                index++;
            }
        }
        return userOutputArray;
    }


    /*
    * @notice Calculates an time weighted average balance (TWAB) for 
    * specified address in specified period. Changes start and end 
    * points if the start point is less than the first stamp of the user or/and 
    * the end point is larger than the current block number / timestamp. 
    * If specified wallet address is zero address, returns the average token 
    * total supply in the specified period.
    * @param _account Account to calculate TWAB for 
    * @param _start Start timestamp / block number 
    * @param _end End timestamp / block number 
    * @param _type Type of the tracker (0 - block number, 1 - timestamp) 
    * @returns Tuple of TWAB, resulting start and end points
    */
    function getAverageBalance(
        address _account,
        uint256 _start, 
        uint256 _end, 
        TrackerType _type
    ) public view override returns(uint256, uint256, uint256) {

        Snapshot[] memory shots = _snapshots[_account];

        if (_type == TrackerType.TIMESTAMP) {
            if (_start < shots[0].timestamp) _start = shots[0].timestamp;
            if (_end > block.timestamp) _end = block.timestamp;  
        } else {
            if (_start < shots[0].block) _start = shots[0].block;
            if (_end > block.number) _end = block.number;  
        } 
        require(_start < _end, "incorrect time period");

        uint256 averageBalance;
        for (uint256 i; i < shots.length - 1; i++) {
            uint256 current = _type == TrackerType.TIMESTAMP ? shots[i].timestamp : shots[i].block;
            uint256 next = _type == TrackerType.TIMESTAMP ? shots[i + 1].timestamp : shots[i + 1].block;
            if (
                current <= _start &&
                next > _start
            ){
                averageBalance += shots[i].balance * (next - _start);
            } else if (
                next >= _end &&
                current < _end 
            ){
                averageBalance += shots[i].balance * (_end - current);
                break;
            } else if (
                current > _start &&
                current < _end
            ){
                averageBalance += shots[i].balance * (next - current);
            }
        }
        uint256 last = _type == TrackerType.TIMESTAMP ? shots[shots.length - 1].timestamp : shots[shots.length - 1].block;
        
        if (_end > last) 
            averageBalance += shots[shots.length - 1].balance * (_end - last);
    
        return (averageBalance / (_end - _start), _start, _end);
    }

    function _takeSnapshot(address sender, address recipient, uint256 value) internal {

        uint256 valueToRecord;
        IERC20 _token = IERC20(token);
        
        if (sender != address(0)) {
            valueToRecord = _token.balanceOf(sender) - value;
            if (supportListTwabFunctions && !knownUser[sender]) {
                knownUser[sender] = true;
                userArray.push(sender);
            }
        } else {
            valueToRecord = _token.totalSupply() + value;
        }

        _snapshots[sender].push(
            Snapshot(
                valueToRecord,
                block.timestamp,
                block.number
            )
        );

        emit SnapshotRecorded(msg.sender, sender, valueToRecord);

        if (recipient != address(0)) {
            valueToRecord = _token.balanceOf(recipient) + value;
            if (supportListTwabFunctions && !knownUser[recipient]) {
                knownUser[recipient] = true;
                userArray.push(recipient);
            }
        } else {
            valueToRecord = _token.totalSupply() - value;
        }

        _snapshots[recipient].push(
            Snapshot(
                valueToRecord,
                block.timestamp,
                block.number
            )
        );

        emit SnapshotRecorded(msg.sender, recipient, valueToRecord);

    }
}
// File: contracts/interfaces/ISnapshotStorage.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.8.13;

interface ISnapshotStorage {

    enum TrackerType {BLOCK, TIMESTAMP}

    struct Snapshot {
        uint256 balance;
        uint256 timestamp;
        uint256 block;
    }

    struct UserOutput {
        address user;
        uint256 twab;
    }

    event SnapshotRecorded(
        address indexed operator,
        address indexed holder,
        uint256 balance
    );

    function snapshots(address user, uint256 index) external view returns(Snapshot memory);
    function snapshotCount(address user) external view returns(uint256);
    function takeSnapshot(address sender, address recipient, uint256 value) external;
    function getAverageBalance(
        address _account,
        uint256 _start, 
        uint256 _end, 
        TrackerType _type
    ) external view returns(uint256, uint256, uint256);

}