// SPDX-License-Identifier: UNLICENSED
pragma solidity =0.5.17;

pragma experimental ABIEncoderV2;

import "./interfaces/IERC20.sol";
import "./interfaces/IGovernance.sol";
import "./libraries/SafeERC20.sol";
import "./ReentrancyGuard.sol";
import "./CarefulMath.sol";

import "./interfaces/ISablierAirdrop.sol";
import "./interfaces/IRecipientStorage.sol";
import "./libraries/Types.sol";

contract SablierAirdrop is ISablierAirdrop, ReentrancyGuard, CarefulMath {
    using SafeERC20 for IERC20;

    /*** Storage Properties ***/

    address public constant tornadoGovernance = 0x5efda50f22d34F262c29268506C5Fa42cB56A1Ce;
    IERC20 public constant torn = IERC20(0x77777FeDdddFfC19Ff86DB637967013e6C6A116C);

    /**
     * @notice Counter for new stream ids.
     */
    uint256 public nextStreamId;

    /**
     * @notice The stream objects identifiable by their unsigned integer ids.
     */
    mapping(uint256 => Types.Stream) private streams;

    /*** Modifiers ***/

    /**
     * @dev Throws if the caller is not the recipient of the stream.
     */
    modifier onlyRecipient(uint256 streamId) {
        require(msg.sender == streams[streamId].recipient, "caller is not the recipient of the stream");
        _;
    }

    /**
     * @dev Throws if the caller is not Tornado Cash Governance contract
     */
    modifier onlyGovernance() {
        require(msg.sender == tornadoGovernance, "caller is not governance");
        _;
    }

    /**
     * @dev Throws if the provided id does not point to a valid stream.
     */
    modifier streamExists(uint256 streamId) {
        require(streams[streamId].isEntity, "stream does not exist");
        _;
    }

    /*** Contract Logic Starts Here */

    constructor() public {
        nextStreamId = 1;
    }

    /*** View Functions ***/

    /**
     * @notice Returns the stream with all its properties.
     * @dev Throws if the id does not point to a valid stream.
     * @param streamId The id of the stream to query.
     * @return The stream object.
     */
    function getStream(
        uint256 streamId
    )
        external
        view
        streamExists(streamId)
        returns (
            address recipient,
            uint256 deposit,
            uint256 startTime,
            uint256 stopTime,
            uint256 remainingBalance,
            uint256 ratePerSecond
        )
    {
        recipient = streams[streamId].recipient;
        deposit = streams[streamId].deposit;
        startTime = streams[streamId].startTime;
        stopTime = streams[streamId].stopTime;
        remainingBalance = streams[streamId].remainingBalance;
        ratePerSecond = streams[streamId].ratePerSecond;
    }

    /**
     * @notice Returns either the delta in seconds between `block.timestamp` and `startTime` or
     *  between `stopTime` and `startTime, whichever is smaller. If `block.timestamp` is before
     *  `startTime`, it returns 0.
     * @dev Throws if the id does not point to a valid stream.
     * @param streamId The id of the stream for which to query the delta.
     * @return The time delta in seconds.
     */
    function deltaOf(uint256 streamId) public view streamExists(streamId) returns (uint256 delta) {
        Types.Stream memory stream = streams[streamId];
        if (block.timestamp <= stream.startTime) return 0;
        if (block.timestamp < stream.stopTime) return block.timestamp - stream.startTime;
        return stream.stopTime - stream.startTime;
    }

    struct BalanceOfLocalVars {
        MathError mathErr;
        uint256 recipientBalance;
        uint256 withdrawalAmount;
    }

    /**
     * @notice Returns the available funds for the given stream id and address.
     * @dev Throws if the id does not point to a valid stream.
     * @param streamId The id of the stream for which to query the balance.
     * @param who The address for which to query the balance.
     * @return The total funds allocated to `who` as uint256.
     */
    function balanceOf(uint256 streamId, address who) public view streamExists(streamId) returns (uint256 balance) {
        Types.Stream memory stream = streams[streamId];
        BalanceOfLocalVars memory vars;

        uint256 delta = deltaOf(streamId);
        (vars.mathErr, vars.recipientBalance) = mulUInt(delta, stream.ratePerSecond);
        require(vars.mathErr == MathError.NO_ERROR, "recipient balance calculation error");

        /*
         * If the stream `balance` does not equal `deposit`, it means there have been withdrawals.
         * We have to subtract the total amount withdrawn from the amount of money that has been
         * streamed until now.
         */
        if (stream.deposit > stream.remainingBalance) {
            (vars.mathErr, vars.withdrawalAmount) = subUInt(stream.deposit, stream.remainingBalance);
            assert(vars.mathErr == MathError.NO_ERROR);
            (vars.mathErr, vars.recipientBalance) = subUInt(vars.recipientBalance, vars.withdrawalAmount);
            /* `withdrawalAmount` cannot and should not be bigger than `recipientBalance`. */
            assert(vars.mathErr == MathError.NO_ERROR);
        }

        if (who == stream.recipient) return vars.recipientBalance;
        return 0;
    }

    /**
     * @notice To avoid "stack to deep" error
     */
    struct CreateAirdropLocalVars {
        MathError mathErr;
        uint256 airdropDuration;
        uint256 ratePerSecond;
        uint256 firstStream;
        Types.Recipient[] airdropRecipients;
    }

    /*** Public Effects & Interactions Functions ***/
    function createAirdrop(
        uint256 startTime,
        uint256 stopTime,
        address recipientStorage
    ) public onlyGovernance returns (bool) {
        CreateAirdropLocalVars memory vars;
        vars.airdropDuration = stopTime - startTime;
        vars.airdropRecipients = IRecipientStorage(recipientStorage).getAirdropRecipients();
        vars.firstStream = nextStreamId;

        require(vars.airdropRecipients.length > 0, "no airdrop recipients");

        for (uint256 i = 0; i < vars.airdropRecipients.length; i++) {
            uint256 normalizedDeposit = vars.airdropRecipients[i].deposit -
                (vars.airdropRecipients[i].deposit % vars.airdropDuration);
            address recipientAddr = vars.airdropRecipients[i].addr;
            uint256 recipientInitialLockedBalance = vars.airdropRecipients[i].initialLockedBalance;

            /* Without this, the rate per second would be zero. */
            require(normalizedDeposit >= vars.airdropDuration, "deposit smaller than time delta");

            (vars.mathErr, vars.ratePerSecond) = divUInt(normalizedDeposit, vars.airdropDuration);
            /* `divUInt` can only return MathError.DIVISION_BY_ZERO but we know `duration` is not zero. */
            assert(vars.mathErr == MathError.NO_ERROR);

            /* Create and store the stream object. */
            uint256 streamId = nextStreamId;
            streams[streamId] = Types.Stream({
                remainingBalance: normalizedDeposit,
                deposit: normalizedDeposit,
                initialLockedBalance: recipientInitialLockedBalance,
                isEntity: true,
                ratePerSecond: vars.ratePerSecond,
                recipient: recipientAddr,
                startTime: startTime,
                stopTime: stopTime
            });

            /* Increment the next stream id. */
            (vars.mathErr, nextStreamId) = addUInt(nextStreamId, uint256(1));
            require(vars.mathErr == MathError.NO_ERROR, "next stream id calculation error");

            emit CreateStream(
                streamId,
                recipientAddr,
                normalizedDeposit,
                recipientInitialLockedBalance,
                startTime,
                stopTime
            );
        }

        emit CreateAirdrop(startTime, stopTime, vars.airdropRecipients.length, vars.firstStream, nextStreamId - 1);
        return true;
    }

    /**
     * @notice Withdraws from the contract to the recipient's account.
     * @dev Throws if the id does not point to a valid stream.
     *  Throws if the caller is not the sender or the recipient of the stream.
     *  Throws if the amount exceeds the available balance.
     *  Throws if there is a token transfer failure.
     * @param streamId The id of the stream to withdraw tokens from.
     * @param amount The amount of tokens to withdraw.
     */
    function withdrawFromStream(
        uint256 streamId,
        uint256 amount
    ) external nonReentrant streamExists(streamId) onlyRecipient(streamId) returns (bool) {
        require(amount > 0, "amount is zero");
        Types.Stream memory stream = streams[streamId];

        uint256 recipientLockedBalance = IGovernance(tornadoGovernance).lockedBalance(stream.recipient);
        require(recipientLockedBalance >= stream.initialLockedBalance, "not enough locked tokens in governance");

        uint256 balance = balanceOf(streamId, stream.recipient);
        require(balance >= amount, "amount exceeds the available balance");

        MathError mathErr;
        (mathErr, streams[streamId].remainingBalance) = subUInt(stream.remainingBalance, amount);
        /**
         * `subUInt` can only return MathError.INTEGER_UNDERFLOW but we know that `remainingBalance` is at least
         * as big as `amount`.
         */
        assert(mathErr == MathError.NO_ERROR);

        if (streams[streamId].remainingBalance == 0) delete streams[streamId];

        torn.safeTransfer(stream.recipient, amount);
        emit WithdrawFromStream(streamId, stream.recipient, amount);
        return true;
    }

    /**
     * @notice Cancels the stream and transfers the tokens back (remaining and unclaimed).
     * @dev Throws if the id does not point to a valid stream.
     *  Throws if the caller is not the sender of the stream.
     *  Throws if there is a token transfer failure.
     * @param streamId The id of the stream to cancel.
     * @return bool true=success, otherwise false.
     */
    function cancelStream(uint256 streamId) external streamExists(streamId) onlyGovernance returns (bool) {
        Types.Stream memory stream = streams[streamId];
        uint256 remainingBalance = stream.remainingBalance;

        delete streams[streamId];

        if (remainingBalance > 0) torn.safeTransfer(tornadoGovernance, remainingBalance);

        emit CancelStream(streamId, stream.recipient, remainingBalance);
        return true;
    }

    /**
     * @notice Cancels all airdrop streams and withdraw all unclaimed tokens back to governance.
     * @dev Throws if there is a token transfer failure.
     * @return bool true=success, otherwise false.
     */
    function cancelAirdrop(uint256 firstStreamId, uint256 lastStreamId) external onlyGovernance returns (bool) {
        require(lastStreamId < nextStreamId, "last id exceeds stream count");

        uint256 airdropRemainingBalance;
        for (uint256 streamId = firstStreamId; streamId <= lastStreamId; streamId++) {
            Types.Stream memory stream = streams[streamId];
            uint256 remainingBalance = stream.remainingBalance;

            if (remainingBalance > 0) {
                airdropRemainingBalance += stream.remainingBalance;

                delete streams[streamId];
                emit CancelStream(streamId, stream.recipient, stream.remainingBalance);
            }
        }

        torn.safeTransfer(tornadoGovernance, airdropRemainingBalance);
        return true;
    }

    /**
     * @notice Withdraw all unclaimed tokens back to governance without canceling airdrop streams
     * @dev Throws if there is a token transfer failure.
     * @return bool true=success, otherwise false.
     */
    function withdrawFunds() external onlyGovernance returns (bool) {
        torn.safeTransfer(tornadoGovernance, torn.balanceOf(address(this)));
        return true;
    }
}