include/Orderbook.h

#pragma once

#include <map>
#include <unordered_map>
#include <list>
#include <thread>
#include <condition_variable>
#include <mutex>
#include <atomic>
#include <functional>
#include <optional>
#include <chrono>
#include <vector>

#include "Types.h"
#include "Order.h"
#include "Trade.h"

class Orderbook {
public:
    using OnTradeCallback    = std::function<void(const Trade&)>;
    using OnOrderCallback    = std::function<void(const Order&)>;
    using OnSnapshotCallback = std::function<void(const OrderbookSnapshot&)>;

    Orderbook();
    ~Orderbook();
    Orderbook(const Orderbook&)            = delete;
    Orderbook& operator=(const Orderbook&) = delete;
    Orderbook(Orderbook&&)                 = delete;
    Orderbook& operator=(Orderbook&&)      = delete;

    // ─── Core API ─────────────────────────────────────────────────────────────
    Trades   AddOrder   (OrderPointer order);
    void     CancelOrder(OrderId orderId);
    Trades   ModifyOrder(OrderModify order);

    // ─── Query API ────────────────────────────────────────────────────────────
    std::size_t       Size()        const;
    bool              HasOrder(OrderId) const;
    OrderbookSnapshot GetSnapshot() const;
    Price             BestBid()     const;
    Price             BestAsk()     const;
    Price             MidPrice()    const;
    Price             Spread()      const;

    // ─── Statistics ───────────────────────────────────────────────────────────
    uint64_t GetTotalOrders()    const noexcept { return stats_.totalOrders.load();  }
    uint64_t GetTotalTrades()    const noexcept { return stats_.totalTrades.load();  }
    uint64_t GetTotalCancels()   const noexcept { return stats_.totalCancels.load(); }
    uint64_t GetTotalVolume()    const noexcept { return stats_.totalVolume.load();  }
    uint64_t GetSequenceNumber() const noexcept { return stats_.seqNum.load();       }

    // ─── Event Hooks ──────────────────────────────────────────────────────────
    void SetOnTrade(OnTradeCallback cb)          { onTrade_     = std::move(cb); }
    void SetOnOrderAdded(OnOrderCallback cb)     { onAdded_     = std::move(cb); }
    void SetOnOrderCancelled(OnOrderCallback cb) { onCancelled_ = std::move(cb); }

    // BUG FIX #3: No longer public — called internally only, no longer calls
    // AddOrderInternal directly to avoid recursive MatchOrders → stack overflow.
    void CheckAndTriggerStops(Price lastTrade);

private:
    struct OrderEntry {
        OrderPointer           order;
        OrderPointers::iterator location;
    };

    struct LevelData {
        Quantity quantity{0};
        uint32_t count{0};
        enum class Action { Add, Remove, Match };
    };

    std::map<Price, OrderPointers, std::greater<Price>> bids_;
    std::map<Price, OrderPointers, std::less<Price>>    asks_;
    std::unordered_map<OrderId, OrderEntry>             orders_;
    std::unordered_map<Price, LevelData>                levelData_;
    std::multimap<Price, OrderPointer>                  stopBuys_;
    std::multimap<Price, OrderPointer, std::greater<Price>> stopSells_;

    // BUG FIX #3: Deferred stop injection buffer — stops collected here during
    // MatchOrders and injected AFTER matching loop exits, preventing recursive
    // MatchOrders calls that could cause stack overflow on stop chains.
    std::vector<OrderPointer> pendingStops_;

    mutable std::mutex         ordersMutex_;
    std::thread                pruneThread_;
    std::condition_variable    shutdownCV_;
    std::atomic<bool>          shutdown_{false};

    struct Stats {
        std::atomic<uint64_t> totalOrders{0};
        std::atomic<uint64_t> totalTrades{0};
        std::atomic<uint64_t> totalCancels{0};
        std::atomic<uint64_t> totalVolume{0};
        std::atomic<uint64_t> seqNum{0};
        std::atomic<Price>    lastTradePrice{0};
        std::atomic<Quantity> lastTradeQty{0};
    } stats_;

    OnTradeCallback  onTrade_;
    OnOrderCallback  onAdded_;
    OnOrderCallback  onCancelled_;

    void   PruneGoodForDayOrders();
    void   CancelOrdersInternal(const OrderIds& ids);
    void   CancelOrderInternal (OrderId orderId);
    Trades AddOrderInternal    (OrderPointer order);

    bool   CanMatch     (Side side, Price price) const;
    bool   CanFullyFill (Side side, Price price, Quantity qty) const;

    Trades MatchOrders  ();
    Trade  MakeTrade    (OrderPointer bid, OrderPointer ask, Quantity qty);

    void   UpdateLevelData  (Price price, Quantity qty, LevelData::Action action);
    void   OnOrderAdded     (OrderPointer order);
    void   OnOrderCancelled (OrderPointer order);
    void   OnOrderMatched   (Price price, Quantity qty, bool fullyFilled);
};