pragma solidity ^0.5.16;

// Inheritance
import "./Owned.sol";
import "./MixinResolver.sol";
import "./interfaces/IBinaryOptionMarket.sol";

// Libraries
import "./SafeDecimalMath.sol";

// Internal references
import "./BinaryOptionMarketManager.sol";
import "./BinaryOption.sol";
import "./interfaces/IExchangeRates.sol";
import "./interfaces/IERC20.sol";
import "./interfaces/IFeePool.sol";


// https://docs.synthetix.io/contracts/source/contracts/binaryoptionmarket
contract BinaryOptionMarket is Owned, MixinResolver, IBinaryOptionMarket {
    /* ========== LIBRARIES ========== */

    using SafeMath for uint;
    using SafeDecimalMath for uint;

    /* ========== TYPES ========== */

    struct Options {
        BinaryOption long;
        BinaryOption short;
    }

    struct Prices {
        uint long;
        uint short;
    }

    struct Times {
        uint biddingEnd;
        uint maturity;
        uint expiry;
    }

    struct OracleDetails {
        bytes32 key;
        uint strikePrice;
        uint finalPrice;
    }

    /* ========== STATE VARIABLES ========== */

    Options public options;
    Prices public prices;
    Times public times;
    OracleDetails public oracleDetails;
    BinaryOptionMarketManager.Fees public fees;
    BinaryOptionMarketManager.CreatorLimits public creatorLimits;

    // `deposited` tracks the sum of open bids on short and long, plus withheld refund fees.
    // This must explicitly be kept, in case tokens are transferred to the contract directly.
    uint public deposited;
    address public creator;
    bool public resolved;
    bool public refundsEnabled;

    uint internal _feeMultiplier;

    /* ---------- Address Resolver Configuration ---------- */

    bytes32 internal constant CONTRACT_SYSTEMSTATUS = "SystemStatus";
    bytes32 internal constant CONTRACT_EXRATES = "ExchangeRates";
    bytes32 internal constant CONTRACT_SYNTHSUSD = "SynthsUSD";
    bytes32 internal constant CONTRACT_FEEPOOL = "FeePool";

    /* ========== CONSTRUCTOR ========== */

    constructor(
        address _owner,
        address _creator,
        address _resolver,
        uint[2] memory _creatorLimits, // [capitalRequirement, skewLimit]
        bytes32 _oracleKey,
        uint _strikePrice,
        bool _refundsEnabled,
        uint[3] memory _times, // [biddingEnd, maturity, expiry]
        uint[2] memory _bids, // [longBid, shortBid]
        uint[3] memory _fees // [poolFee, creatorFee, refundFee]
    ) public Owned(_owner) MixinResolver(_resolver) {
        creator = _creator;
        creatorLimits = BinaryOptionMarketManager.CreatorLimits(_creatorLimits[0], _creatorLimits[1]);

        oracleDetails = OracleDetails(_oracleKey, _strikePrice, 0);
        times = Times(_times[0], _times[1], _times[2]);

        refundsEnabled = _refundsEnabled;

        (uint longBid, uint shortBid) = (_bids[0], _bids[1]);
        _checkCreatorLimits(longBid, shortBid);
        emit Bid(Side.Long, _creator, longBid);
        emit Bid(Side.Short, _creator, shortBid);

        // Note that the initial deposit of synths must be made by the manager, otherwise the contract's assumed
        // deposits will fall out of sync with its actual balance. Similarly the total system deposits must be updated in the manager.
        // A balance check isn't performed here since the manager doesn't know the address of the new contract until after it is created.
        uint initialDeposit = longBid.add(shortBid);
        deposited = initialDeposit;

        (uint poolFee, uint creatorFee) = (_fees[0], _fees[1]);
        fees = BinaryOptionMarketManager.Fees(poolFee, creatorFee, _fees[2]);
        _feeMultiplier = SafeDecimalMath.unit().sub(poolFee.add(creatorFee));

        // Compute the prices now that the fees and deposits have been set.
        _updatePrices(longBid, shortBid, initialDeposit);

        // Instantiate the options themselves
        options.long = new BinaryOption(_creator, longBid);
        options.short = new BinaryOption(_creator, shortBid);
    }

    /* ========== VIEWS ========== */

    function resolverAddressesRequired() public view returns (bytes32[] memory addresses) {
        addresses = new bytes32[](4);
        addresses[0] = CONTRACT_SYSTEMSTATUS;
        addresses[1] = CONTRACT_EXRATES;
        addresses[2] = CONTRACT_SYNTHSUSD;
        addresses[3] = CONTRACT_FEEPOOL;
    }

    /* ---------- External Contracts ---------- */

    function _systemStatus() internal view returns (ISystemStatus) {
        return ISystemStatus(requireAndGetAddress(CONTRACT_SYSTEMSTATUS));
    }

    function _exchangeRates() internal view returns (IExchangeRates) {
        return IExchangeRates(requireAndGetAddress(CONTRACT_EXRATES));
    }

    function _sUSD() internal view returns (IERC20) {
        return IERC20(requireAndGetAddress(CONTRACT_SYNTHSUSD));
    }

    function _feePool() internal view returns (IFeePool) {
        return IFeePool(requireAndGetAddress(CONTRACT_FEEPOOL));
    }

    function _manager() internal view returns (BinaryOptionMarketManager) {
        return BinaryOptionMarketManager(owner);
    }

    /* ---------- Phases ---------- */

    function _biddingEnded() internal view returns (bool) {
        return times.biddingEnd < now;
    }

    function _matured() internal view returns (bool) {
        return times.maturity < now;
    }

    function _expired() internal view returns (bool) {
        return resolved && (times.expiry < now || deposited == 0);
    }

    function phase() external view returns (Phase) {
        if (!_biddingEnded()) {
            return Phase.Bidding;
        }
        if (!_matured()) {
            return Phase.Trading;
        }
        if (!_expired()) {
            return Phase.Maturity;
        }
        return Phase.Expiry;
    }

    /* ---------- Market Resolution ---------- */

    function _oraclePriceAndTimestamp() internal view returns (uint price, uint updatedAt) {
        return _exchangeRates().rateAndUpdatedTime(oracleDetails.key);
    }

    function oraclePriceAndTimestamp() external view returns (uint price, uint updatedAt) {
        return _oraclePriceAndTimestamp();
    }

    function _isFreshPriceUpdateTime(uint timestamp) internal view returns (bool) {
        (uint maxOraclePriceAge, , ) = _manager().durations();
        return (times.maturity.sub(maxOraclePriceAge)) <= timestamp;
    }

    function canResolve() external view returns (bool) {
        (, uint updatedAt) = _oraclePriceAndTimestamp();
        return !resolved && _matured() && _isFreshPriceUpdateTime(updatedAt);
    }

    function _result() internal view returns (Side) {
        uint price;
        if (resolved) {
            price = oracleDetails.finalPrice;
        } else {
            (price, ) = _oraclePriceAndTimestamp();
        }

        return oracleDetails.strikePrice <= price ? Side.Long : Side.Short;
    }

    function result() external view returns (Side) {
        return _result();
    }

    /* ---------- Option Prices ---------- */

    function _computePrices(
        uint longBids,
        uint shortBids,
        uint _deposited
    ) internal view returns (uint long, uint short) {
        require(longBids != 0 && shortBids != 0, "Bids must be nonzero");
        uint optionsPerSide = _exercisableDeposits(_deposited);

        // The math library rounds up on an exact half-increment -- the price on one side may be an increment too high,
        // but this only implies a tiny extra quantity will go to fees.
        return (longBids.divideDecimalRound(optionsPerSide), shortBids.divideDecimalRound(optionsPerSide));
    }

    function senderPriceAndExercisableDeposits() external view returns (uint price, uint exercisable) {
        // When the market is not yet resolved, both sides might be able to exercise all the options.
        // On the other hand, if the market has resolved, then only the winning side may exercise.
        exercisable = 0;
        if (!resolved || address(_option(_result())) == msg.sender) {
            exercisable = _exercisableDeposits(deposited);
        }

        // Send the correct price for each side of the market.
        if (msg.sender == address(options.long)) {
            price = prices.long;
        } else if (msg.sender == address(options.short)) {
            price = prices.short;
        } else {
            revert("Sender is not an option");
        }
    }

    function pricesAfterBidOrRefund(
        Side side,
        uint value,
        bool refund
    ) external view returns (uint long, uint short) {
        (uint longTotalBids, uint shortTotalBids) = _totalBids();
        // prettier-ignore
        function(uint, uint) pure returns (uint) operation = refund ? SafeMath.sub : SafeMath.add;

        if (side == Side.Long) {
            longTotalBids = operation(longTotalBids, value);
        } else {
            shortTotalBids = operation(shortTotalBids, value);
        }

        if (refund) {
            value = value.multiplyDecimalRound(SafeDecimalMath.unit().sub(fees.refundFee));
        }
        return _computePrices(longTotalBids, shortTotalBids, operation(deposited, value));
    }

    // Returns zero if the result would be negative. See the docs for the formulae this implements.
    function bidOrRefundForPrice(
        Side bidSide,
        Side priceSide,
        uint price,
        bool refund
    ) external view returns (uint) {
        uint adjustedPrice = price.multiplyDecimalRound(_feeMultiplier);
        uint bids = _option(priceSide).totalBids();
        uint _deposited = deposited;
        uint unit = SafeDecimalMath.unit();
        uint refundFeeMultiplier = unit.sub(fees.refundFee);

        if (bidSide == priceSide) {
            uint depositedByPrice = _deposited.multiplyDecimalRound(adjustedPrice);

            // For refunds, the numerator is the negative of the bid case and,
            // in the denominator the adjusted price has an extra factor of (1 - the refundFee).
            if (refund) {
                (depositedByPrice, bids) = (bids, depositedByPrice);
                adjustedPrice = adjustedPrice.multiplyDecimalRound(refundFeeMultiplier);
            }

            // The adjusted price is guaranteed to be less than 1: all its factors are also less than 1.
            return _subToZero(depositedByPrice, bids).divideDecimalRound(unit.sub(adjustedPrice));
        } else {
            uint bidsPerPrice = bids.divideDecimalRound(adjustedPrice);

            // For refunds, the numerator is the negative of the bid case.
            if (refund) {
                (bidsPerPrice, _deposited) = (_deposited, bidsPerPrice);
            }

            uint value = _subToZero(bidsPerPrice, _deposited);
            return refund ? value.divideDecimalRound(refundFeeMultiplier) : value;
        }
    }

    /* ---------- Option Balances and Bids ---------- */

    function _bidsOf(address account) internal view returns (uint long, uint short) {
        return (options.long.bidOf(account), options.short.bidOf(account));
    }

    function bidsOf(address account) external view returns (uint long, uint short) {
        return _bidsOf(account);
    }

    function _totalBids() internal view returns (uint long, uint short) {
        return (options.long.totalBids(), options.short.totalBids());
    }

    function totalBids() external view returns (uint long, uint short) {
        return _totalBids();
    }

    function _claimableBalancesOf(address account) internal view returns (uint long, uint short) {
        return (options.long.claimableBalanceOf(account), options.short.claimableBalanceOf(account));
    }

    function claimableBalancesOf(address account) external view returns (uint long, uint short) {
        return _claimableBalancesOf(account);
    }

    function totalClaimableSupplies() external view returns (uint long, uint short) {
        return (options.long.totalClaimableSupply(), options.short.totalClaimableSupply());
    }

    function _balancesOf(address account) internal view returns (uint long, uint short) {
        return (options.long.balanceOf(account), options.short.balanceOf(account));
    }

    function balancesOf(address account) external view returns (uint long, uint short) {
        return _balancesOf(account);
    }

    function totalSupplies() external view returns (uint long, uint short) {
        return (options.long.totalSupply(), options.short.totalSupply());
    }

    function _exercisableDeposits(uint _deposited) internal view returns (uint) {
        // Fees are deducted at resolution, so remove them if we're still bidding or trading.
        return resolved ? _deposited : _deposited.multiplyDecimalRound(_feeMultiplier);
    }

    function exercisableDeposits() external view returns (uint) {
        return _exercisableDeposits(deposited);
    }

    /* ---------- Utilities ---------- */

    function _chooseSide(
        Side side,
        uint longValue,
        uint shortValue
    ) internal pure returns (uint) {
        if (side == Side.Long) {
            return longValue;
        }
        return shortValue;
    }

    function _option(Side side) internal view returns (BinaryOption) {
        if (side == Side.Long) {
            return options.long;
        }
        return options.short;
    }

    // Returns zero if the result would be negative.
    function _subToZero(uint a, uint b) internal pure returns (uint) {
        return a < b ? 0 : a.sub(b);
    }

    function _checkCreatorLimits(uint longBid, uint shortBid) internal view {
        uint totalBid = longBid.add(shortBid);
        require(creatorLimits.capitalRequirement <= totalBid, "Insufficient capital");
        uint skewLimit = creatorLimits.skewLimit;
        require(
            skewLimit <= longBid.divideDecimal(totalBid) && skewLimit <= shortBid.divideDecimal(totalBid),
            "Bids too skewed"
        );
    }

    function _incrementDeposited(uint value) internal returns (uint _deposited) {
        _deposited = deposited.add(value);
        deposited = _deposited;
        _manager().incrementTotalDeposited(value);
    }

    function _decrementDeposited(uint value) internal returns (uint _deposited) {
        _deposited = deposited.sub(value);
        deposited = _deposited;
        _manager().decrementTotalDeposited(value);
    }

    function _requireManagerNotPaused() internal view {
        require(!_manager().paused(), "This action cannot be performed while the contract is paused");
    }

    function requireActiveAndUnpaused() external view {
        _systemStatus().requireSystemActive();
        _requireManagerNotPaused();
    }

    /* ========== MUTATIVE FUNCTIONS ========== */

    /* ---------- Bidding and Refunding ---------- */

    function _updatePrices(
        uint longBids,
        uint shortBids,
        uint _deposited
    ) internal {
        (uint256 longPrice, uint256 shortPrice) = _computePrices(longBids, shortBids, _deposited);
        prices = Prices(longPrice, shortPrice);
        emit PricesUpdated(longPrice, shortPrice);
    }

    function bid(Side side, uint value) external duringBidding {
        if (value == 0) {
            return;
        }

        _option(side).bid(msg.sender, value);
        emit Bid(side, msg.sender, value);

        uint _deposited = _incrementDeposited(value);
        _sUSD().transferFrom(msg.sender, address(this), value);

        (uint longTotalBids, uint shortTotalBids) = _totalBids();
        _updatePrices(longTotalBids, shortTotalBids, _deposited);
    }

    function refund(Side side, uint value) external duringBidding returns (uint refundMinusFee) {
        require(refundsEnabled, "Refunds disabled");
        if (value == 0) {
            return 0;
        }

        // Require the market creator to leave sufficient capital in the market.
        if (msg.sender == creator) {
            (uint thisBid, uint thatBid) = _bidsOf(msg.sender);
            if (side == Side.Short) {
                (thisBid, thatBid) = (thatBid, thisBid);
            }
            _checkCreatorLimits(thisBid.sub(value), thatBid);
        }

        // Safe subtraction here and in related contracts will fail if either the
        // total supply, deposits, or wallet balance are too small to support the refund.
        refundMinusFee = value.multiplyDecimalRound(SafeDecimalMath.unit().sub(fees.refundFee));

        _option(side).refund(msg.sender, value);
        emit Refund(side, msg.sender, refundMinusFee, value.sub(refundMinusFee));

        uint _deposited = _decrementDeposited(refundMinusFee);
        _sUSD().transfer(msg.sender, refundMinusFee);

        (uint longTotalBids, uint shortTotalBids) = _totalBids();
        _updatePrices(longTotalBids, shortTotalBids, _deposited);
    }

    /* ---------- Market Resolution ---------- */

    function resolve() external onlyOwner afterMaturity systemActive managerNotPaused {
        require(!resolved, "Market already resolved");

        // We don't need to perform stale price checks, so long as the price was
        // last updated recently enough before the maturity date.
        (uint price, uint updatedAt) = _oraclePriceAndTimestamp();
        require(_isFreshPriceUpdateTime(updatedAt), "Price is stale");

        oracleDetails.finalPrice = price;
        resolved = true;

        // Now remit any collected fees.
        // Since the constructor enforces that creatorFee + poolFee < 1, the balance
        // in the contract will be sufficient to cover these transfers.
        IERC20 sUSD = _sUSD();

        uint _deposited = deposited;
        uint poolFees = _deposited.multiplyDecimalRound(fees.poolFee);
        uint creatorFees = _deposited.multiplyDecimalRound(fees.creatorFee);
        _decrementDeposited(creatorFees.add(poolFees));
        sUSD.transfer(_feePool().FEE_ADDRESS(), poolFees);
        sUSD.transfer(creator, creatorFees);

        emit MarketResolved(_result(), price, updatedAt, deposited, poolFees, creatorFees);
    }

    /* ---------- Claiming and Exercising Options ---------- */

    function _claimOptions()
        internal
        systemActive
        managerNotPaused
        afterBidding
        returns (uint longClaimed, uint shortClaimed)
    {
        uint exercisable = _exercisableDeposits(deposited);
        Side outcome = _result();
        bool _resolved = resolved;

        // Only claim options if we aren't resolved, and only claim the winning side.
        uint longOptions;
        uint shortOptions;
        if (!_resolved || outcome == Side.Long) {
            longOptions = options.long.claim(msg.sender, prices.long, exercisable);
        }
        if (!_resolved || outcome == Side.Short) {
            shortOptions = options.short.claim(msg.sender, prices.short, exercisable);
        }

        require(longOptions != 0 || shortOptions != 0, "Nothing to claim");
        emit OptionsClaimed(msg.sender, longOptions, shortOptions);
        return (longOptions, shortOptions);
    }

    function claimOptions() external returns (uint longClaimed, uint shortClaimed) {
        return _claimOptions();
    }

    function exerciseOptions() external returns (uint) {
        // The market must be resolved if it has not been.
        if (!resolved) {
            _manager().resolveMarket(address(this));
        }

        // If there are options to be claimed, claim them and proceed.
        (uint claimableLong, uint claimableShort) = _claimableBalancesOf(msg.sender);
        if (claimableLong != 0 || claimableShort != 0) {
            _claimOptions();
        }

        // If the account holds no options, revert.
        (uint longBalance, uint shortBalance) = _balancesOf(msg.sender);
        require(longBalance != 0 || shortBalance != 0, "Nothing to exercise");

        // Each option only needs to be exercised if the account holds any of it.
        if (longBalance != 0) {
            options.long.exercise(msg.sender);
        }
        if (shortBalance != 0) {
            options.short.exercise(msg.sender);
        }

        // Only pay out the side that won.
        uint payout = _chooseSide(_result(), longBalance, shortBalance);
        emit OptionsExercised(msg.sender, payout);
        if (payout != 0) {
            _decrementDeposited(payout);
            _sUSD().transfer(msg.sender, payout);
        }
        return payout;
    }

    /* ---------- Market Expiry ---------- */

    function _selfDestruct(address payable beneficiary) internal {
        uint _deposited = deposited;
        if (_deposited != 0) {
            _decrementDeposited(_deposited);
        }

        // Transfer the balance rather than the deposit value in case there are any synths left over
        // from direct transfers.
        IERC20 sUSD = _sUSD();
        uint balance = sUSD.balanceOf(address(this));
        if (balance != 0) {
            sUSD.transfer(beneficiary, balance);
        }

        // Destroy the option tokens before destroying the market itself.
        options.long.expire(beneficiary);
        options.short.expire(beneficiary);
        selfdestruct(beneficiary);
    }

    function cancel(address payable beneficiary) external onlyOwner duringBidding {
        (uint longTotalBids, uint shortTotalBids) = _totalBids();
        (uint creatorLongBids, uint creatorShortBids) = _bidsOf(creator);
        bool cancellable = longTotalBids == creatorLongBids && shortTotalBids == creatorShortBids;
        require(cancellable, "Not cancellable");
        _selfDestruct(beneficiary);
    }

    function expire(address payable beneficiary) external onlyOwner {
        require(_expired(), "Unexpired options remaining");
        _selfDestruct(beneficiary);
    }

    /* ========== MODIFIERS ========== */

    modifier duringBidding() {
        require(!_biddingEnded(), "Bidding inactive");
        _;
    }

    modifier afterBidding() {
        require(_biddingEnded(), "Bidding incomplete");
        _;
    }

    modifier afterMaturity() {
        require(_matured(), "Not yet mature");
        _;
    }

    modifier systemActive() {
        _systemStatus().requireSystemActive();
        _;
    }

    modifier managerNotPaused() {
        _requireManagerNotPaused();
        _;
    }

    /* ========== EVENTS ========== */

    event Bid(Side side, address indexed account, uint value);
    event Refund(Side side, address indexed account, uint value, uint fee);
    event PricesUpdated(uint longPrice, uint shortPrice);
    event MarketResolved(
        Side result,
        uint oraclePrice,
        uint oracleTimestamp,
        uint deposited,
        uint poolFees,
        uint creatorFees
    );
    event OptionsClaimed(address indexed account, uint longOptions, uint shortOptions);
    event OptionsExercised(address indexed account, uint value);
}