pragma solidity 0.6.12;
pragma experimental ABIEncoderV2;

import "@openzeppelin/contracts/GSN/Context.sol";
import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";
import "@openzeppelin/contracts/utils/Address.sol";
import "./interfaces/IERC20Burnable.sol";

import "hardhat/console.sol";

//    ___    __        __                _               ___                              __         _ 
//   / _ |  / / ____  / /  ___   __ _   (_) __ __       / _ \  ____ ___   ___ ___   ___  / /_  ___  (_)
//  / __ | / / / __/ / _ \/ -_) /  ' \ / /  \ \ /      / ___/ / __// -_) (_-</ -_) / _ \/ __/ (_-< _
// /_/ |_|/_/  \__/ /_//_/\__/ /_/_/_//_/  /_\_\      /_/    /_/   \__/ /___/\__/ /_//_/\__/ /___/(_)
//
// .___________..______           ___      .__   __.      _______..___  ___.  __    __  .___________. _______ .______
// |           ||   _  \         /   \     |  \ |  |     /       ||   \/   | |  |  |  | |           ||   ____||   _  \
// `---|  |----`|  |_)  |       /  ^  \    |   \|  |    |   (----`|  \  /  | |  |  |  | `---|  |----`|  |__   |  |_)  |
//     |  |     |      /       /  /_\  \   |  . `  |     \   \    |  |\/|  | |  |  |  |     |  |     |   __|  |      /
//     |  |     |  |\  \----. /  _____  \  |  |\   | .----)   |   |  |  |  | |  `--'  |     |  |     |  |____ |  |\  \----.
//     |__|     | _| `._____|/__/     \__\ |__| \__| |_______/    |__|  |__|  \______/      |__|     |_______|| _| `._____|
/**
 * @dev Implementation of the {IERC20Burnable} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 * For a generic mechanism see {ERC20PresetMinterPauser}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * We have followed general OpenZeppelin guidelines: functions revert instead
 * of returning `false` on failure. This behavior is nonetheless conventional
 * and does not conflict with the expectations of ERC20 applications.
 *
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See {IERC20Burnable-approve}.
 */
contract Transmuter is Context {
    using SafeMath for uint256;
    using SafeERC20 for IERC20Burnable;
    using Address for address;

    address public constant ZERO_ADDRESS = address(0);
    uint256 public TRANSMUTATION_PERIOD;

    address public AlToken;
    address public Token;

    mapping(address => uint256) public depositedAlTokens;
    mapping(address => uint256) public tokensInBucket;
    mapping(address => uint256) public realisedTokens;
    mapping(address => uint256) public lastDividendPoints;

    mapping(address => bool) public userIsKnown;
    mapping(uint256 => address) public userList;
    uint256 public nextUser;

    uint256 public totalSupplyAltokens;
    uint256 public buffer;
    uint256 public lastDepositBlock;

    ///@dev values needed to calculate the distribution of base asset in proportion for alTokens staked
    uint256 public pointMultiplier = 10e18;

    uint256 public totalDividendPoints;
    uint256 public unclaimedDividends;

    /// @dev alchemist addresses whitelisted
    mapping (address => bool) public whiteList;

    /// @dev The address of the account which currently has administrative capabilities over this contract.
    address public governance;

    /// @dev The address of the pending governance.
    address public pendingGovernance;

    event GovernanceUpdated(
        address governance
    );

    event PendingGovernanceUpdated(
        address pendingGovernance
    );

    event TransmuterPeriodUpdated(
        uint256 newTransmutationPeriod
    );

    constructor(address _AlToken, address _Token, address _governance) public {
        require(_governance != ZERO_ADDRESS, "Transmuter: 0 gov");
        governance = _governance;
        AlToken = _AlToken;
        Token = _Token;
        TRANSMUTATION_PERIOD = 50;
    }

    ///@return displays the user's share of the pooled alTokens.
    function dividendsOwing(address account) public view returns (uint256) {
        uint256 newDividendPoints = totalDividendPoints.sub(lastDividendPoints[account]);
        return depositedAlTokens[account].mul(newDividendPoints).div(pointMultiplier);
    }

    ///@dev modifier to fill the bucket and keep bookkeeping correct incase of increase/decrease in shares
    modifier updateAccount(address account) {
        uint256 owing = dividendsOwing(account);
        if (owing > 0) {
            unclaimedDividends = unclaimedDividends.sub(owing);
            tokensInBucket[account] = tokensInBucket[account].add(owing);
        }
        lastDividendPoints[account] = totalDividendPoints;
        _;
    }
    ///@dev modifier add users to userlist. Users are indexed in order to keep track of when a bond has been filled
    modifier checkIfNewUser() {
        if (!userIsKnown[msg.sender]) {
            userList[nextUser] = msg.sender;
            userIsKnown[msg.sender] = true;
            nextUser++;
        }
        _;
    }

    ///@dev run the phased distribution of the buffered funds
    modifier runPhasedDistribution() {
        uint256 _lastDepositBlock = lastDepositBlock;
        uint256 _currentBlock = block.number;
        uint256 _toDistribute = 0;
        uint256 _buffer = buffer;

        // check if there is something in bufffer
        if (_buffer > 0) {
            // NOTE: if last deposit was updated in the same block as the current call
            // then the below logic gates will fail

            //calculate diffrence in time
            uint256 deltaTime = _currentBlock.sub(_lastDepositBlock);

            // distribute all if bigger than timeframe
            if(deltaTime >= TRANSMUTATION_PERIOD) {
                _toDistribute = _buffer;
            } else {

                //needs to be bigger than 0 cuzz solidity no decimals
                if(_buffer.mul(deltaTime) > TRANSMUTATION_PERIOD)
                {
                    _toDistribute = _buffer.mul(deltaTime).div(TRANSMUTATION_PERIOD);
                }
            }

            // factually allocate if any needs distribution
            if(_toDistribute > 0){

                // remove from buffer
                buffer = _buffer.sub(_toDistribute);

                // increase the allocation
                increaseAllocations(_toDistribute);
            }
        }

        // current timeframe is now the last
        lastDepositBlock = _currentBlock;
        _;
    }

    /// @dev A modifier which checks if whitelisted for minting.
    modifier onlyWhitelisted() {
        require(whiteList[msg.sender], "Transmuter: !whitelisted");
        _;
    }

    /// @dev Checks that the current message sender or caller is the governance address.
    ///
    ///
    modifier onlyGov() {
        require(msg.sender == governance, "Transmuter: !governance");
        _;
    }

    ///@dev set the TRANSMUTATION_PERIOD variable
    ///
    /// sets the length (in blocks) of one full distribution phase
    function setTransmutationPeriod(uint256 newTransmutationPeriod) public onlyGov() {
        TRANSMUTATION_PERIOD = newTransmutationPeriod;
        emit TransmuterPeriodUpdated(TRANSMUTATION_PERIOD);
    }

    ///@dev claims the base token after it has been transmuted
    ///
    ///This function reverts if there is no realisedToken balance
    function claim() public {
        address sender = msg.sender;
        require(realisedTokens[sender] > 0);
        uint256 value = realisedTokens[sender];
        realisedTokens[sender] = 0;
        IERC20Burnable(Token).safeTransfer(sender, value);
    }

    ///@dev Withdraws staked alTokens from the transmuter
    ///
    /// This function reverts if you try to draw more tokens than you deposited
    ///
    ///@param amount the amount of alTokens to unstake
    function unstake(uint256 amount) public updateAccount(msg.sender) {
        // by calling this function before transmuting you forfeit your gained allocation
        address sender = msg.sender;
        require(depositedAlTokens[sender] >= amount,"Transmuter: unstake amount exceeds deposited amount");
        depositedAlTokens[sender] = depositedAlTokens[sender].sub(amount);
        totalSupplyAltokens = totalSupplyAltokens.sub(amount);
        IERC20Burnable(AlToken).safeTransfer(sender, amount);
    }
    ///@dev Deposits alTokens into the transmuter 
    ///
    ///@param amount the amount of alTokens to stake
    function stake(uint256 amount)
        public
        runPhasedDistribution()
        updateAccount(msg.sender)
        checkIfNewUser()
    {
        // requires approval of AlToken first
        address sender = msg.sender;
        //require tokens transferred in;
        IERC20Burnable(AlToken).safeTransferFrom(sender, address(this), amount);
        totalSupplyAltokens = totalSupplyAltokens.add(amount);
        depositedAlTokens[sender] = depositedAlTokens[sender].add(amount);
    }
    /// @dev Converts the staked alTokens to the base tokens in amount of the sum of pendingdivs and tokensInBucket
    ///
    /// once the alToken has been converted, it is burned, and the base token becomes realisedTokens which can be recieved using claim()    
    ///
    /// reverts if there are no pendingdivs or tokensInBucket
    function transmute() public runPhasedDistribution() updateAccount(msg.sender) {
        address sender = msg.sender;
        uint256 pendingz = tokensInBucket[sender];
        uint256 diff;

        require(pendingz > 0, "need to have pending in bucket");

        tokensInBucket[sender] = 0;

        // check bucket overflow
        if (pendingz > depositedAlTokens[sender]) {
            diff = pendingz.sub(depositedAlTokens[sender]);

            // remove overflow
            pendingz = depositedAlTokens[sender];
        }

        // decrease altokens
        depositedAlTokens[sender] = depositedAlTokens[sender].sub(pendingz);

        // BURN ALTOKENS
        IERC20Burnable(AlToken).burn(pendingz);

        // adjust total
        totalSupplyAltokens = totalSupplyAltokens.sub(pendingz);

        // reallocate overflow
        increaseAllocations(diff);

        // add payout
        realisedTokens[sender] = realisedTokens[sender].add(pendingz);
    }

    /// @dev Executes transmute() on another account that has had more base tokens allocated to it than alTokens staked.
    ///
    /// The caller of this function will have the surlus base tokens credited to their tokensInBucket balance, rewarding them for performing this action
    ///
    /// This function reverts if the address to transmute is not over-filled.
    ///
    /// @param toTransmute address of the account you will force transmute.
    function forceTransmute(address toTransmute)
        public
        runPhasedDistribution()
        updateAccount(msg.sender)
        updateAccount(toTransmute)
    {
        //load into memory
        address sender = msg.sender;
        uint256 pendingz = tokensInBucket[toTransmute];
        // check restrictions
        require(
            pendingz > depositedAlTokens[toTransmute],
            "Transmuter: !overflow"
        );

        // empty bucket
        tokensInBucket[toTransmute] = 0;

        // calculaate diffrence
        uint256 diff = pendingz.sub(depositedAlTokens[toTransmute]);

        // remove overflow
        pendingz = depositedAlTokens[toTransmute];

        // decrease altokens
        depositedAlTokens[toTransmute] = 0;

        // BURN ALTOKENS
        IERC20Burnable(AlToken).burn(pendingz);

        // adjust total
        totalSupplyAltokens = totalSupplyAltokens.sub(pendingz);

        // reallocate overflow
        tokensInBucket[sender] = tokensInBucket[sender].add(diff);

        // add payout
        realisedTokens[toTransmute] = realisedTokens[toTransmute].add(pendingz);

        // force payout of realised tokens of the toTransmute address
        if (realisedTokens[toTransmute] > 0) {
            uint256 value = realisedTokens[toTransmute];
            realisedTokens[toTransmute] = 0;
            IERC20Burnable(Token).safeTransfer(toTransmute, value);
        }
    }

    /// @dev Transmutes and unstakes all alTokens
    ///
    /// This function combines the transmute and unstake functions for ease of use
    function exit() public {
        transmute();
        uint256 toWithdraw = depositedAlTokens[msg.sender];
        unstake(toWithdraw);
    }

    /// @dev Transmutes and claims all converted base tokens.
    ///
    /// This function combines the transmute and claim functions while leaving your remaining alTokens staked.
    function transmuteAndClaim() public {
        transmute();
        claim();
    }

    /// @dev Transmutes, claims base tokens, and withdraws alTokens.
    ///
    /// This function helps users to exit the transmuter contract completely after converting their alTokens to the base pair.
    function transmuteClaimAndWithdraw() public {
        transmute();
        claim();
        uint256 toWithdraw = depositedAlTokens[msg.sender];
        unstake(toWithdraw);
    }

    /// @dev Distributes the base token proportionally to all alToken stakers.
    ///
    /// This function is meant to be called by the Alchemist contract for when it is sending yield to the transmuter. 
    /// Anyone can call this and add funds, idk why they would do that though...
    ///
    /// @param origin the account that is sending the tokens to be distributed.
    /// @param amount the amount of base tokens to be distributed to the transmuter.
    function distribute(address origin, uint256 amount) public onlyWhitelisted() runPhasedDistribution() {
        IERC20Burnable(Token).safeTransferFrom(origin, address(this), amount);
        buffer = buffer.add(amount);
    }

    /// @dev Allocates the incoming yield proportionally to all alToken stakers.
    ///
    /// @param amount the amount of base tokens to be distributed in the transmuter.
    function increaseAllocations(uint256 amount) internal {
        if(totalSupplyAltokens > 0 && amount > 0) {
            totalDividendPoints = totalDividendPoints.add(
                amount.mul(pointMultiplier).div(totalSupplyAltokens)
            );
            unclaimedDividends = unclaimedDividends.add(amount);
        } else {
            buffer = buffer.add(amount);
        }
    }

    /// @dev Gets the status of a user's staking position.
    ///
    /// The total amount allocated to a user is the sum of pendingdivs and inbucket.
    ///
    /// @param user the address of the user you wish to query.
    ///
    /// returns user status
    
    function userInfo(address user)
        public
        view
        returns (
            uint256 depositedAl,
            uint256 pendingdivs,
            uint256 inbucket,
            uint256 realised
        )
    {
        uint256 _depositedAl = depositedAlTokens[user];
        uint256 _toDistribute = buffer.mul(block.number.sub(lastDepositBlock)).div(TRANSMUTATION_PERIOD);
        if(block.number.sub(lastDepositBlock) > TRANSMUTATION_PERIOD){
            _toDistribute = buffer;
        }
        uint256 _pendingdivs = _toDistribute.mul(depositedAlTokens[user]).div(totalSupplyAltokens);
        uint256 _inbucket = tokensInBucket[user].add(dividendsOwing(user));
        uint256 _realised = realisedTokens[user];
        return (_depositedAl, _pendingdivs, _inbucket, _realised);
    }

    /// @dev Gets the status of multiple users in one call
    ///
    /// This function is used to query the contract to check for
    /// accounts that have overfilled positions in order to check 
    /// who can be force transmuted.
    ///
    /// @param from the first index of the userList
    /// @param to the last index of the userList
    ///
    /// returns the userList with their staking status in paginated form. 
    function getMultipleUserInfo(uint256 from, uint256 to)
        public
        view
        returns (address[] memory theUserList, uint256[] memory theUserData)
    {
        uint256 i = from;
        uint256 delta = to - from;
        address[] memory _theUserList = new address[](delta); //user
        uint256[] memory _theUserData = new uint256[](delta * 2); //deposited-bucket
        uint256 y = 0;
        uint256 _toDistribute = buffer.mul(block.number.sub(lastDepositBlock)).div(TRANSMUTATION_PERIOD);
        if(block.number.sub(lastDepositBlock) > TRANSMUTATION_PERIOD){
            _toDistribute = buffer;
        }
        for (uint256 x = 0; x < delta; x += 1) {
            _theUserList[x] = userList[i];
            _theUserData[y] = depositedAlTokens[userList[i]];
            _theUserData[y + 1] = dividendsOwing(userList[i]).add(tokensInBucket[userList[i]]).add(_toDistribute.mul(depositedAlTokens[userList[i]]).div(totalSupplyAltokens));
            y += 2;
            i += 1;
        }
        return (_theUserList, _theUserData);
    }

    /// @dev Gets info on the buffer
    ///
    /// This function is used to query the contract to get the
    /// latest state of the buffer
    ///
    /// @return _toDistribute the amount ready to be distributed
    /// @return _deltaBlocks the amount of time since the last phased distribution
    /// @return _buffer the amount in the buffer 
    function bufferInfo() public view returns (uint256 _toDistribute, uint256 _deltaBlocks, uint256 _buffer){
        _deltaBlocks = block.number.sub(lastDepositBlock);
        _buffer = buffer; 
        _toDistribute = _buffer.mul(_deltaBlocks).div(TRANSMUTATION_PERIOD);
    }

    /// @dev Sets the pending governance.
    ///
    /// This function reverts if the new pending governance is the zero address or the caller is not the current
    /// governance. This is to prevent the contract governance being set to the zero address which would deadlock
    /// privileged contract functionality.
    ///
    /// @param _pendingGovernance the new pending governance.
    function setPendingGovernance(address _pendingGovernance) external onlyGov {
        require(_pendingGovernance != ZERO_ADDRESS, "Transmuter: 0 gov");

        pendingGovernance = _pendingGovernance;

        emit PendingGovernanceUpdated(_pendingGovernance);
    }

    /// @dev Accepts the role as governance.
    ///
    /// This function reverts if the caller is not the new pending governance.
    function acceptGovernance() external  {
        require(msg.sender == pendingGovernance,"!pendingGovernance");
        address _pendingGovernance = pendingGovernance;
        governance = _pendingGovernance;

        emit GovernanceUpdated(_pendingGovernance);
    }

    /// This function reverts if the caller is not governance
    ///
    /// @param _toWhitelist the account to mint tokens to.
    /// @param _state the whitelist state.

    function setWhitelist(address _toWhitelist, bool _state) external onlyGov {
        whiteList[_toWhitelist] = _state;
    }
}