nautilus_execution/engine/

mod.rs

// -------------------------------------------------------------------------------------------------
//  Copyright (C) 2015-2026 Nautech Systems Pty Ltd. All rights reserved.
//  https://nautechsystems.io
//
//  Licensed under the GNU Lesser General Public License Version 3.0 (the "License");
//  You may not use this file except in compliance with the License.
//  You may obtain a copy of the License at https://www.gnu.org/licenses/lgpl-3.0.en.html
//
//  Unless required by applicable law or agreed to in writing, software
//  distributed under the License is distributed on an "AS IS" BASIS,
//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//  See the License for the specific language governing permissions and
//  limitations under the License.
// -------------------------------------------------------------------------------------------------

//! Provides a generic `ExecutionEngine` for all environments.
//!
//! The execution engines primary responsibility is to orchestrate interactions
//! between the `ExecutionClient` instances, and the rest of the platform. This
//! includes sending commands to, and receiving events from, the trading venue
//! endpoints via its registered execution clients.

pub mod config;
pub mod stubs;

#[cfg(test)]
mod tests;

use std::{
    cell::{RefCell, RefMut},
    collections::{HashMap, HashSet},
    fmt::Debug,
    rc::Rc,
    time::SystemTime,
};

use ahash::{AHashMap, AHashSet};
use config::ExecutionEngineConfig;
use futures::future::join_all;
use nautilus_common::{
    cache::Cache,
    clock::Clock,
    generators::position_id::PositionIdGenerator,
    logging::{CMD, EVT, RECV, SEND},
    messages::execution::{
        BatchCancelOrders, CancelAllOrders, CancelOrder, ModifyOrder, QueryAccount, QueryOrder,
        SubmitOrder, SubmitOrderList, TradingCommand,
    },
    msgbus::{
        self, get_message_bus,
        switchboard::{self},
    },
};
use nautilus_core::UUID4;
use nautilus_model::{
    enums::{ContingencyType, OmsType, OrderSide, PositionSide},
    events::{
        OrderDenied, OrderEvent, OrderEventAny, OrderFilled, PositionChanged, PositionClosed,
        PositionEvent, PositionOpened,
    },
    identifiers::{ClientId, ClientOrderId, InstrumentId, PositionId, StrategyId, Venue},
    instruments::{Instrument, InstrumentAny},
    orderbook::own::{OwnOrderBook, should_handle_own_book_order},
    orders::{Order, OrderAny, OrderError},
    position::Position,
    reports::ExecutionMassStatus,
    types::{Money, Price, Quantity},
};

use crate::client::{ExecutionClient, ExecutionClientAdapter};

/// Central execution engine responsible for orchestrating order routing and execution.
///
/// The execution engine manages the entire order lifecycle from submission to completion,
/// handling routing to appropriate execution clients, position management, and event
/// processing. It supports multiple execution venues through registered clients and
/// provides sophisticated order management capabilities.
pub struct ExecutionEngine {
    clock: Rc<RefCell<dyn Clock>>,
    cache: Rc<RefCell<Cache>>,
    clients: AHashMap<ClientId, ExecutionClientAdapter>,
    default_client: Option<ExecutionClientAdapter>,
    routing_map: HashMap<Venue, ClientId>,
    oms_overrides: HashMap<StrategyId, OmsType>,
    external_order_claims: HashMap<InstrumentId, StrategyId>,
    external_clients: HashSet<ClientId>,
    pos_id_generator: PositionIdGenerator,
    config: ExecutionEngineConfig,
}

impl Debug for ExecutionEngine {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct(stringify!(ExecutionEngine))
            .field("client_count", &self.clients.len())
            .finish()
    }
}

impl ExecutionEngine {
    /// Creates a new [`ExecutionEngine`] instance.
    pub fn new(
        clock: Rc<RefCell<dyn Clock>>,
        cache: Rc<RefCell<Cache>>,
        config: Option<ExecutionEngineConfig>,
    ) -> Self {
        let trader_id = get_message_bus().borrow().trader_id;
        Self {
            clock: clock.clone(),
            cache,
            clients: AHashMap::new(),
            default_client: None,
            routing_map: HashMap::new(),
            oms_overrides: HashMap::new(),
            external_order_claims: HashMap::new(),
            external_clients: config
                .as_ref()
                .and_then(|c| c.external_clients.clone())
                .unwrap_or_default()
                .into_iter()
                .collect(),
            pos_id_generator: PositionIdGenerator::new(trader_id, clock),
            config: config.unwrap_or_default(),
        }
    }

    #[must_use]
    /// Returns the position ID count for the specified strategy.
    pub fn position_id_count(&self, strategy_id: StrategyId) -> usize {
        self.pos_id_generator.count(strategy_id)
    }

    #[must_use]
    /// Checks the integrity of cached execution data.
    pub fn check_integrity(&self) -> bool {
        self.cache.borrow_mut().check_integrity()
    }

    #[must_use]
    /// Returns true if all registered execution clients are connected.
    pub fn check_connected(&self) -> bool {
        let clients_connected = self.clients.values().all(|c| c.is_connected());
        let default_connected = self
            .default_client
            .as_ref()
            .is_none_or(|c| c.is_connected());
        clients_connected && default_connected
    }

    #[must_use]
    /// Returns true if all registered execution clients are disconnected.
    pub fn check_disconnected(&self) -> bool {
        let clients_disconnected = self.clients.values().all(|c| !c.is_connected());
        let default_disconnected = self
            .default_client
            .as_ref()
            .is_none_or(|c| !c.is_connected());
        clients_disconnected && default_disconnected
    }

    #[must_use]
    /// Checks for residual positions and orders in the cache.
    pub fn check_residuals(&self) -> bool {
        self.cache.borrow().check_residuals()
    }

    #[must_use]
    /// Returns the set of instruments that have external order claims.
    pub fn get_external_order_claims_instruments(&self) -> HashSet<InstrumentId> {
        self.external_order_claims.keys().copied().collect()
    }

    #[must_use]
    /// Returns the configured external client IDs.
    pub fn get_external_client_ids(&self) -> HashSet<ClientId> {
        self.external_clients.clone()
    }

    #[must_use]
    /// Returns any external order claim for the given instrument ID.
    pub fn get_external_order_claim(&self, instrument_id: &InstrumentId) -> Option<StrategyId> {
        self.external_order_claims.get(instrument_id).copied()
    }

    // -- REGISTRATION ----------------------------------------------------------------------------

    /// Registers a new execution client.
    ///
    /// # Errors
    ///
    /// Returns an error if a client with the same ID is already registered.
    pub fn register_client(&mut self, client: Box<dyn ExecutionClient>) -> anyhow::Result<()> {
        let client_id = client.client_id();
        let venue = client.venue();

        if self.clients.contains_key(&client_id) {
            anyhow::bail!("Client already registered with ID {client_id}");
        }

        let adapter = ExecutionClientAdapter::new(client);

        self.routing_map.insert(venue, client_id);

        log::debug!("Registered client {client_id}");
        self.clients.insert(client_id, adapter);
        Ok(())
    }

    /// Registers a default execution client for fallback routing.
    pub fn register_default_client(&mut self, client: Box<dyn ExecutionClient>) {
        let client_id = client.client_id();
        let adapter = ExecutionClientAdapter::new(client);

        log::debug!("Registered default client {client_id}");
        self.default_client = Some(adapter);
    }

    #[must_use]
    /// Returns a reference to the execution client registered with the given ID.
    pub fn get_client(&self, client_id: &ClientId) -> Option<&dyn ExecutionClient> {
        self.clients.get(client_id).map(|a| a.client.as_ref())
    }

    #[must_use]
    /// Returns a mutable reference to the execution client adapter registered with the given ID.
    pub fn get_client_adapter_mut(
        &mut self,
        client_id: &ClientId,
    ) -> Option<&mut ExecutionClientAdapter> {
        if let Some(default) = &self.default_client
            && &default.client_id == client_id
        {
            return self.default_client.as_mut();
        }
        self.clients.get_mut(client_id)
    }

    /// Generates mass status for the given client.
    ///
    /// # Errors
    ///
    /// Returns an error if the client is not found or mass status generation fails.
    pub async fn generate_mass_status(
        &mut self,
        client_id: &ClientId,
        lookback_mins: Option<u64>,
    ) -> anyhow::Result<Option<ExecutionMassStatus>> {
        if let Some(client) = self.get_client_adapter_mut(client_id) {
            client.generate_mass_status(lookback_mins).await
        } else {
            anyhow::bail!("Client {client_id} not found")
        }
    }

    #[must_use]
    /// Returns all registered execution client IDs.
    pub fn client_ids(&self) -> Vec<ClientId> {
        let mut ids: Vec<_> = self.clients.keys().copied().collect();

        if let Some(default) = &self.default_client {
            ids.push(default.client_id);
        }
        ids
    }

    #[must_use]
    /// Returns mutable access to all registered execution clients.
    pub fn get_clients_mut(&mut self) -> Vec<&mut ExecutionClientAdapter> {
        let mut adapters: Vec<_> = self.clients.values_mut().collect();
        if let Some(default) = &mut self.default_client {
            adapters.push(default);
        }
        adapters
    }

    #[must_use]
    /// Returns execution clients that would handle the given orders.
    ///
    /// This method first attempts to resolve each order's originating client from the cache,
    /// then falls back to venue routing for any orders without a cached client.
    pub fn get_clients_for_orders(&self, orders: &[OrderAny]) -> Vec<&dyn ExecutionClient> {
        let mut client_ids: AHashSet<ClientId> = AHashSet::new();
        let mut venues: AHashSet<Venue> = AHashSet::new();

        // Collect client IDs from cache and venues for fallback
        for order in orders {
            venues.insert(order.instrument_id().venue);
            if let Some(client_id) = self.cache.borrow().client_id(&order.client_order_id()) {
                client_ids.insert(*client_id);
            }
        }

        let mut clients: Vec<&dyn ExecutionClient> = Vec::new();

        // Add clients for cached client IDs (orders go back to originating client)
        for client_id in &client_ids {
            if let Some(adapter) = self.clients.get(client_id)
                && !clients.iter().any(|c| c.client_id() == adapter.client_id)
            {
                clients.push(adapter.client.as_ref());
            }
        }

        // Add clients for venue routing (for orders not in cache)
        for venue in &venues {
            if let Some(client_id) = self.routing_map.get(venue) {
                if let Some(adapter) = self.clients.get(client_id)
                    && !clients.iter().any(|c| c.client_id() == adapter.client_id)
                {
                    clients.push(adapter.client.as_ref());
                }
            } else if let Some(adapter) = &self.default_client
                && !clients.iter().any(|c| c.client_id() == adapter.client_id)
            {
                clients.push(adapter.client.as_ref());
            }
        }

        clients
    }

    /// Sets routing for a specific venue to a given client ID.
    ///
    /// # Errors
    ///
    /// Returns an error if the client ID is not registered.
    pub fn register_venue_routing(
        &mut self,
        client_id: ClientId,
        venue: Venue,
    ) -> anyhow::Result<()> {
        if !self.clients.contains_key(&client_id) {
            anyhow::bail!("No client registered with ID {client_id}");
        }

        self.routing_map.insert(venue, client_id);
        log::info!("Set client {client_id} routing for {venue}");
        Ok(())
    }

    /// Registers the OMS (Order Management System) type for a strategy.
    ///
    /// If an OMS type is already registered for this strategy, it will be overridden.
    pub fn register_oms_type(&mut self, strategy_id: StrategyId, oms_type: OmsType) {
        self.oms_overrides.insert(strategy_id, oms_type);
        log::info!("Registered OMS::{oms_type:?} for {strategy_id}");
    }

    /// Registers external order claims for a strategy.
    ///
    /// This operation is atomic: either all instruments are registered or none are.
    ///
    /// # Errors
    ///
    /// Returns an error if any instrument already has a registered claim.
    pub fn register_external_order_claims(
        &mut self,
        strategy_id: StrategyId,
        instrument_ids: HashSet<InstrumentId>,
    ) -> anyhow::Result<()> {
        // Validate all instruments first
        for instrument_id in &instrument_ids {
            if let Some(existing) = self.external_order_claims.get(instrument_id) {
                anyhow::bail!(
                    "External order claim for {instrument_id} already exists for {existing}"
                );
            }
        }

        // If validation passed, insert all claims
        for instrument_id in &instrument_ids {
            self.external_order_claims
                .insert(*instrument_id, strategy_id);
        }

        if !instrument_ids.is_empty() {
            log::info!("Registered external order claims for {strategy_id}: {instrument_ids:?}");
        }

        Ok(())
    }

    /// # Errors
    ///
    /// Returns an error if no client is registered with the given ID.
    pub fn deregister_client(&mut self, client_id: ClientId) -> anyhow::Result<()> {
        if self.clients.remove(&client_id).is_some() {
            // Remove from routing map if present
            self.routing_map
                .retain(|_, mapped_id| mapped_id != &client_id);
            log::info!("Deregistered client {client_id}");
            Ok(())
        } else {
            anyhow::bail!("No client registered with ID {client_id}")
        }
    }

    /// Connects all registered execution clients concurrently.
    ///
    /// # Errors
    ///
    /// Returns an error if any client fails to connect.
    pub async fn connect(&mut self) -> anyhow::Result<()> {
        let futures: Vec<_> = self
            .get_clients_mut()
            .into_iter()
            .map(|client| client.connect())
            .collect();

        let results = join_all(futures).await;
        let errors: Vec<_> = results.into_iter().filter_map(Result::err).collect();

        if errors.is_empty() {
            Ok(())
        } else {
            let error_msgs: Vec<_> = errors.iter().map(|e| e.to_string()).collect();
            anyhow::bail!(
                "Failed to connect execution clients: {}",
                error_msgs.join("; ")
            )
        }
    }

    /// Disconnects all registered execution clients concurrently.
    ///
    /// # Errors
    ///
    /// Returns an error if any client fails to disconnect.
    pub async fn disconnect(&mut self) -> anyhow::Result<()> {
        let futures: Vec<_> = self
            .get_clients_mut()
            .into_iter()
            .map(|client| client.disconnect())
            .collect();

        let results = join_all(futures).await;
        let errors: Vec<_> = results.into_iter().filter_map(Result::err).collect();

        if errors.is_empty() {
            Ok(())
        } else {
            let error_msgs: Vec<_> = errors.iter().map(|e| e.to_string()).collect();
            anyhow::bail!(
                "Failed to disconnect execution clients: {}",
                error_msgs.join("; ")
            )
        }
    }

    /// Sets the `manage_own_order_books` configuration option.
    pub fn set_manage_own_order_books(&mut self, value: bool) {
        self.config.manage_own_order_books = value;
    }

    /// Sets the `convert_quote_qty_to_base` configuration option.
    pub fn set_convert_quote_qty_to_base(&mut self, value: bool) {
        self.config.convert_quote_qty_to_base = value;
    }

    /// Starts the position snapshot timer if configured.
    ///
    /// Timer functionality requires a live execution context with an active clock.
    pub fn start_snapshot_timer(&mut self) {
        if let Some(interval_secs) = self.config.snapshot_positions_interval_secs {
            log::info!("Starting position snapshots timer at {interval_secs} second intervals");
        }
    }

    /// Stops the position snapshot timer if running.
    pub fn stop_snapshot_timer(&mut self) {
        if self.config.snapshot_positions_interval_secs.is_some() {
            log::info!("Canceling position snapshots timer");
        }
    }

    /// Creates snapshots of all open positions.
    pub fn snapshot_open_position_states(&self) {
        let positions: Vec<Position> = self
            .cache
            .borrow()
            .positions_open(None, None, None, None)
            .into_iter()
            .cloned()
            .collect();

        for position in positions {
            self.create_position_state_snapshot(&position);
        }
    }

    // -- COMMANDS --------------------------------------------------------------------------------

    #[allow(clippy::await_holding_refcell_ref)]
    /// Loads persistent state into cache and rebuilds indices.
    ///
    /// # Errors
    ///
    /// Returns an error if any cache operation fails.
    pub async fn load_cache(&mut self) -> anyhow::Result<()> {
        let ts = SystemTime::now();

        {
            let mut cache = self.cache.borrow_mut();
            cache.clear_index();
            cache.cache_general()?;
            self.cache.borrow_mut().cache_all().await?;
            cache.build_index();
            let _ = cache.check_integrity();

            if self.config.manage_own_order_books {
                for order in cache.orders(None, None, None, None) {
                    if order.is_closed() || !should_handle_own_book_order(order) {
                        continue;
                    }
                    let mut own_book = self.get_or_init_own_order_book(&order.instrument_id());
                    own_book.add(order.to_own_book_order());
                }
            }
        }

        self.set_position_id_counts();

        log::info!(
            "Loaded cache in {}ms",
            SystemTime::now()
                .duration_since(ts)
                .map_err(|e| anyhow::anyhow!("Failed to calculate duration: {e}"))?
                .as_millis()
        );

        Ok(())
    }

    /// Flushes the database to persist all cached data.
    pub fn flush_db(&self) {
        self.cache.borrow_mut().flush_db();
    }

    /// Processes an order event, updating internal state and routing as needed.
    pub fn process(&mut self, event: &OrderEventAny) {
        self.handle_event(event);
    }

    /// Executes a trading command by routing it to the appropriate execution client.
    pub fn execute(&self, command: &TradingCommand) {
        self.execute_command(command);
    }

    // -- COMMAND HANDLERS ------------------------------------------------------------------------

    fn execute_command(&self, command: &TradingCommand) {
        if self.config.debug {
            log::debug!("{RECV}{CMD} {command:?}");
        }

        if let Some(cid) = command.client_id()
            && self.external_clients.contains(&cid)
        {
            if self.config.debug {
                log::debug!("Skipping execution command for external client {cid}: {command:?}");
            }
            return;
        }

        let client = if let Some(adapter) = command
            .client_id()
            .and_then(|cid| self.clients.get(&cid))
            .or_else(|| {
                self.routing_map
                    .get(&command.instrument_id().venue)
                    .and_then(|client_id| self.clients.get(client_id))
            })
            .or(self.default_client.as_ref())
        {
            adapter.client.as_ref()
        } else {
            log::error!(
                "No execution client found for command: client_id={:?}, venue={}, command={command:?}",
                command.client_id(),
                command.instrument_id().venue,
            );
            return;
        };

        match command {
            TradingCommand::SubmitOrder(cmd) => self.handle_submit_order(client, cmd),
            TradingCommand::SubmitOrderList(cmd) => self.handle_submit_order_list(client, cmd),
            TradingCommand::ModifyOrder(cmd) => self.handle_modify_order(client, cmd),
            TradingCommand::CancelOrder(cmd) => self.handle_cancel_order(client, cmd),
            TradingCommand::CancelAllOrders(cmd) => self.handle_cancel_all_orders(client, cmd),
            TradingCommand::BatchCancelOrders(cmd) => self.handle_batch_cancel_orders(client, cmd),
            TradingCommand::QueryOrder(cmd) => self.handle_query_order(client, cmd),
            TradingCommand::QueryAccount(cmd) => self.handle_query_account(client, cmd),
        }
    }

    fn handle_submit_order(&self, client: &dyn ExecutionClient, cmd: &SubmitOrder) {
        let mut order = cmd.order.clone();
        let client_order_id = order.client_order_id();
        let instrument_id = order.instrument_id();

        // Check if the order exists in the cache
        if !self.cache.borrow().order_exists(&client_order_id) {
            // Add order to cache in a separate scope to drop the mutable borrow
            {
                let mut cache = self.cache.borrow_mut();
                if let Err(e) = cache.add_order(order.clone(), cmd.position_id, cmd.client_id, true)
                {
                    log::error!("Error adding order to cache: {e}");
                    return;
                }
            }

            if self.config.snapshot_orders {
                self.create_order_state_snapshot(&order);
            }
        }

        // Get instrument in a separate scope to manage borrows
        let instrument = {
            let cache = self.cache.borrow();
            if let Some(instrument) = cache.instrument(&instrument_id) {
                instrument.clone()
            } else {
                log::error!(
                    "Cannot handle submit order: no instrument found for {instrument_id}, {cmd}",
                );
                return;
            }
        };

        // Handle quote quantity conversion
        if self.config.convert_quote_qty_to_base
            && !instrument.is_inverse()
            && order.is_quote_quantity()
        {
            log::warn!(
                "`convert_quote_qty_to_base` is deprecated; set `convert_quote_qty_to_base=false` to maintain consistent behavior"
            );
            let last_px = self.last_px_for_conversion(&instrument_id, order.order_side());

            if let Some(price) = last_px {
                let base_qty = instrument.get_base_quantity(order.quantity(), price);
                self.set_order_base_qty(&mut order, base_qty);
            } else {
                self.deny_order(
                    &order,
                    &format!("no-price-to-convert-quote-qty {instrument_id}"),
                );
                return;
            }
        }

        if self.config.manage_own_order_books && should_handle_own_book_order(&order) {
            let mut own_book = self.get_or_init_own_order_book(&order.instrument_id());
            own_book.add(order.to_own_book_order());
        }

        // Send the order to the execution client
        if let Err(e) = client.submit_order(cmd) {
            log::error!("Error submitting order to client: {e}");
            self.deny_order(
                &cmd.order,
                &format!("failed-to-submit-order-to-client: {e}"),
            );
        }
    }

    fn handle_submit_order_list(&self, client: &dyn ExecutionClient, cmd: &SubmitOrderList) {
        let orders = cmd.order_list.orders.clone();

        let mut cache = self.cache.borrow_mut();
        for order in &orders {
            if !cache.order_exists(&order.client_order_id()) {
                if let Err(e) = cache.add_order(order.clone(), cmd.position_id, cmd.client_id, true)
                {
                    log::error!("Error adding order to cache: {e}");
                    return;
                }

                if self.config.snapshot_orders {
                    self.create_order_state_snapshot(order);
                }
            }
        }
        drop(cache);

        let instrument = {
            let cache = self.cache.borrow();
            if let Some(instrument) = cache.instrument(&cmd.instrument_id) {
                instrument.clone()
            } else {
                log::error!(
                    "Cannot handle submit order list: no instrument found for {}, {cmd}",
                    cmd.instrument_id,
                );
                return;
            }
        };

        // Handle quote quantity conversion
        if self.config.convert_quote_qty_to_base && !instrument.is_inverse() {
            let mut conversions: Vec<(ClientOrderId, Quantity)> =
                Vec::with_capacity(cmd.order_list.orders.len());

            for order in &cmd.order_list.orders {
                if !order.is_quote_quantity() {
                    continue; // Base quantity already set
                }

                let last_px =
                    self.last_px_for_conversion(&order.instrument_id(), order.order_side());

                if let Some(px) = last_px {
                    let base_qty = instrument.get_base_quantity(order.quantity(), px);
                    conversions.push((order.client_order_id(), base_qty));
                } else {
                    for order in &cmd.order_list.orders {
                        self.deny_order(
                            order,
                            &format!("no-price-to-convert-quote-qty {}", order.instrument_id()),
                        );
                    }
                    return; // Denied
                }
            }

            if !conversions.is_empty() {
                log::warn!(
                    "`convert_quote_qty_to_base` is deprecated; set `convert_quote_qty_to_base=false` to maintain consistent behavior"
                );

                let mut cache = self.cache.borrow_mut();
                for (client_order_id, base_qty) in conversions {
                    if let Some(mut_order) = cache.mut_order(&client_order_id) {
                        self.set_order_base_qty(mut_order, base_qty);
                    }
                }
            }
        }

        if self.config.manage_own_order_books {
            let mut own_book = self.get_or_init_own_order_book(&cmd.instrument_id);
            for order in &cmd.order_list.orders {
                if should_handle_own_book_order(order) {
                    own_book.add(order.to_own_book_order());
                }
            }
        }

        // Send to execution client
        if let Err(e) = client.submit_order_list(cmd) {
            log::error!("Error submitting order list to client: {e}");
            for order in &orders {
                self.deny_order(
                    order,
                    &format!("failed-to-submit-order-list-to-client: {e}"),
                );
            }
        }
    }

    fn handle_modify_order(&self, client: &dyn ExecutionClient, cmd: &ModifyOrder) {
        if let Err(e) = client.modify_order(cmd) {
            log::error!("Error modifying order: {e}");
        }
    }

    fn handle_cancel_order(&self, client: &dyn ExecutionClient, cmd: &CancelOrder) {
        if let Err(e) = client.cancel_order(cmd) {
            log::error!("Error canceling order: {e}");
        }
    }

    fn handle_cancel_all_orders(&self, client: &dyn ExecutionClient, cmd: &CancelAllOrders) {
        if let Err(e) = client.cancel_all_orders(cmd) {
            log::error!("Error canceling all orders: {e}");
        }
    }

    fn handle_batch_cancel_orders(&self, client: &dyn ExecutionClient, cmd: &BatchCancelOrders) {
        if let Err(e) = client.batch_cancel_orders(cmd) {
            log::error!("Error batch canceling orders: {e}");
        }
    }

    fn handle_query_account(&self, client: &dyn ExecutionClient, cmd: &QueryAccount) {
        if let Err(e) = client.query_account(cmd) {
            log::error!("Error querying account: {e}");
        }
    }

    fn handle_query_order(&self, client: &dyn ExecutionClient, cmd: &QueryOrder) {
        if let Err(e) = client.query_order(cmd) {
            log::error!("Error querying order: {e}");
        }
    }

    fn create_order_state_snapshot(&self, order: &OrderAny) {
        if self.config.debug {
            log::debug!("Creating order state snapshot for {order}");
        }

        if self.cache.borrow().has_backing()
            && let Err(e) = self.cache.borrow().snapshot_order_state(order)
        {
            log::error!("Failed to snapshot order state: {e}");
            return;
        }

        if get_message_bus().borrow().has_backing {
            let topic = switchboard::get_order_snapshots_topic(order.client_order_id());
            msgbus::publish(topic, order);
        }
    }

    fn create_position_state_snapshot(&self, position: &Position) {
        if self.config.debug {
            log::debug!("Creating position state snapshot for {position}");
        }

        // let mut position: Position = position.clone();
        // if let Some(pnl) = self.cache.borrow().calculate_unrealized_pnl(&position) {
        //     position.unrealized_pnl(last)
        // }

        let topic = switchboard::get_positions_snapshots_topic(position.id);
        msgbus::publish(topic, position);
    }

    // -- EVENT HANDLERS --------------------------------------------------------------------------

    fn handle_event(&mut self, event: &OrderEventAny) {
        if self.config.debug {
            log::debug!("{RECV}{EVT} {event:?}");
        }

        let client_order_id = event.client_order_id();
        let cache = self.cache.borrow();
        let mut order = if let Some(order) = cache.order(&client_order_id) {
            order.clone()
        } else {
            log::warn!(
                "Order with {} not found in the cache to apply {}",
                event.client_order_id(),
                event
            );

            // Try to find order by venue order ID if available
            let venue_order_id = if let Some(id) = event.venue_order_id() {
                id
            } else {
                log::error!(
                    "Cannot apply event to any order: {} not found in the cache with no VenueOrderId",
                    event.client_order_id()
                );
                return;
            };

            // Look up client order ID from venue order ID
            let client_order_id = if let Some(id) = cache.client_order_id(&venue_order_id) {
                id
            } else {
                log::error!(
                    "Cannot apply event to any order: {} and {venue_order_id} not found in the cache",
                    event.client_order_id(),
                );
                return;
            };

            // Get order using found client order ID
            if let Some(order) = cache.order(client_order_id) {
                log::info!("Order with {client_order_id} was found in the cache");
                order.clone()
            } else {
                log::error!(
                    "Cannot apply event to any order: {client_order_id} and {venue_order_id} not found in cache",
                );
                return;
            }
        };

        drop(cache);

        match event {
            OrderEventAny::Filled(fill) => {
                let oms_type = self.determine_oms_type(fill);
                let position_id = self.determine_position_id(*fill, oms_type, Some(&order));

                let mut fill = *fill;
                if fill.position_id.is_none() {
                    fill.position_id = Some(position_id);
                }

                if self.apply_fill_to_order(&mut order, fill).is_ok() {
                    self.handle_order_fill(&order, fill, oms_type);
                }
            }
            _ => {
                let _ = self.apply_event_to_order(&mut order, event.clone());
            }
        }
    }

    fn determine_oms_type(&self, fill: &OrderFilled) -> OmsType {
        // Check for strategy OMS override
        if let Some(oms_type) = self.oms_overrides.get(&fill.strategy_id) {
            return *oms_type;
        }

        // Use native venue OMS
        if let Some(client_id) = self.routing_map.get(&fill.instrument_id.venue)
            && let Some(client) = self.clients.get(client_id)
        {
            return client.oms_type();
        }

        if let Some(client) = &self.default_client {
            return client.oms_type();
        }

        OmsType::Netting // Default fallback
    }

    fn determine_position_id(
        &mut self,
        fill: OrderFilled,
        oms_type: OmsType,
        order: Option<&OrderAny>,
    ) -> PositionId {
        match oms_type {
            OmsType::Hedging => self.determine_hedging_position_id(fill, order),
            OmsType::Netting => self.determine_netting_position_id(fill),
            _ => self.determine_netting_position_id(fill), // Default to netting
        }
    }

    fn determine_hedging_position_id(
        &mut self,
        fill: OrderFilled,
        order: Option<&OrderAny>,
    ) -> PositionId {
        // Check if position ID already exists
        if let Some(position_id) = fill.position_id {
            if self.config.debug {
                log::debug!("Already had a position ID of: {position_id}");
            }
            return position_id;
        }

        let cache = self.cache.borrow();

        let order = if let Some(o) = order {
            o
        } else {
            match cache.order(&fill.client_order_id()) {
                Some(o) => o,
                None => {
                    panic!(
                        "Order for {} not found to determine position ID",
                        fill.client_order_id()
                    );
                }
            }
        };

        // Check execution spawn orders
        if let Some(spawn_id) = order.exec_spawn_id() {
            let spawn_orders = cache.orders_for_exec_spawn(&spawn_id);
            for spawned_order in spawn_orders {
                if let Some(pos_id) = spawned_order.position_id() {
                    if self.config.debug {
                        log::debug!("Found spawned {} for {}", pos_id, fill.client_order_id());
                    }
                    return pos_id;
                }
            }
        }

        // Generate new position ID
        let position_id = self.pos_id_generator.generate(fill.strategy_id, false);
        if self.config.debug {
            log::debug!("Generated {} for {}", position_id, fill.client_order_id());
        }
        position_id
    }

    fn determine_netting_position_id(&self, fill: OrderFilled) -> PositionId {
        PositionId::new(format!("{}-{}", fill.instrument_id, fill.strategy_id))
    }

    fn apply_fill_to_order(&self, order: &mut OrderAny, fill: OrderFilled) -> anyhow::Result<()> {
        if order.is_duplicate_fill(&fill) {
            log::warn!(
                "Duplicate fill: {} trade_id={} already applied, skipping",
                order.client_order_id(),
                fill.trade_id
            );
            anyhow::bail!("Duplicate fill");
        }

        self.check_overfill(order, &fill)?;
        let event = OrderEventAny::Filled(fill);
        self.apply_order_event(order, event)
    }

    fn apply_event_to_order(
        &self,
        order: &mut OrderAny,
        event: OrderEventAny,
    ) -> anyhow::Result<()> {
        self.apply_order_event(order, event)
    }

    fn apply_order_event(&self, order: &mut OrderAny, event: OrderEventAny) -> anyhow::Result<()> {
        if let Err(e) = order.apply(event.clone()) {
            match e {
                OrderError::InvalidStateTransition => {
                    // Event already applied to order (e.g., from reconciliation or duplicate processing)
                    // Log warning and continue with downstream processing (cache update, publishing, etc.)
                    log::warn!("InvalidStateTrigger: {e}, did not apply {event}");
                }
                OrderError::DuplicateFill(trade_id) => {
                    // Duplicate fill detected at order level (secondary safety check)
                    log::warn!(
                        "Duplicate fill rejected at order level: trade_id={trade_id}, did not apply {event}"
                    );
                    anyhow::bail!("{e}");
                }
                _ => {
                    // Protection against invalid IDs and other invariants
                    log::error!("Error applying event: {e}, did not apply {event}");
                    if should_handle_own_book_order(order) {
                        self.cache.borrow_mut().update_own_order_book(order);
                    }
                    anyhow::bail!("{e}");
                }
            }
        }

        if let Err(e) = self.cache.borrow_mut().update_order(order) {
            log::error!("Error updating order in cache: {e}");
        }

        if self.config.debug {
            log::debug!("{SEND}{EVT} {event}");
        }

        let topic = switchboard::get_event_orders_topic(event.strategy_id());
        msgbus::publish(topic, &event);

        if self.config.snapshot_orders {
            self.create_order_state_snapshot(order);
        }

        Ok(())
    }

    fn check_overfill(&self, order: &OrderAny, fill: &OrderFilled) -> anyhow::Result<()> {
        let potential_overfill = order.calculate_overfill(fill.last_qty);

        if potential_overfill.is_positive() {
            if self.config.allow_overfills {
                log::warn!(
                    "Order overfill detected: {} potential_overfill={}, current_filled={}, last_qty={}, quantity={}",
                    order.client_order_id(),
                    potential_overfill,
                    order.filled_qty(),
                    fill.last_qty,
                    order.quantity()
                );
            } else {
                let msg = format!(
                    "Order overfill rejected: {} potential_overfill={}, current_filled={}, last_qty={}, quantity={}. \
                Set `allow_overfills=true` in ExecutionEngineConfig to allow overfills.",
                    order.client_order_id(),
                    potential_overfill,
                    order.filled_qty(),
                    fill.last_qty,
                    order.quantity()
                );
                anyhow::bail!("{msg}");
            }
        }

        Ok(())
    }

    fn handle_order_fill(&mut self, order: &OrderAny, fill: OrderFilled, oms_type: OmsType) {
        let instrument =
            if let Some(instrument) = self.cache.borrow().instrument(&fill.instrument_id) {
                instrument.clone()
            } else {
                log::error!(
                    "Cannot handle order fill: no instrument found for {}, {fill}",
                    fill.instrument_id,
                );
                return;
            };

        if self.cache.borrow().account(&fill.account_id).is_none() {
            log::error!(
                "Cannot handle order fill: no account found for {}, {fill}",
                fill.instrument_id.venue,
            );
            return;
        }

        // Skip portfolio position updates for combo fills (spread instruments)
        // Combo fills are only used for order management, not portfolio updates
        let position = if instrument.is_spread() {
            None
        } else {
            self.handle_position_update(instrument.clone(), fill, oms_type);
            let position_id = fill.position_id.unwrap();
            self.cache.borrow().position(&position_id).cloned()
        };

        // Handle contingent orders for both spread and non-spread instruments
        // For spread instruments, contingent orders work without position linkage
        if matches!(order.contingency_type(), Some(ContingencyType::Oto)) {
            // For non-spread instruments, link to position if available
            if !instrument.is_spread()
                && let Some(ref pos) = position
                && pos.is_open()
            {
                let position_id = pos.id;
                for client_order_id in order.linked_order_ids().unwrap_or_default() {
                    let mut cache = self.cache.borrow_mut();
                    let contingent_order = cache.mut_order(client_order_id);
                    if let Some(contingent_order) = contingent_order
                        && contingent_order.position_id().is_none()
                    {
                        contingent_order.set_position_id(Some(position_id));

                        if let Err(e) = self.cache.borrow_mut().add_position_id(
                            &position_id,
                            &contingent_order.instrument_id().venue,
                            &contingent_order.client_order_id(),
                            &contingent_order.strategy_id(),
                        ) {
                            log::error!("Failed to add position ID: {e}");
                        }
                    }
                }
            }
            // For spread instruments, contingent orders can still be triggered
            // but without position linkage (since no position is created for spreads)
        }
    }

    /// Handle position creation or update for a fill.
    ///
    /// This function mirrors the Python `_handle_position_update` method.
    fn handle_position_update(
        &mut self,
        instrument: InstrumentAny,
        fill: OrderFilled,
        oms_type: OmsType,
    ) {
        let position_id = if let Some(position_id) = fill.position_id {
            position_id
        } else {
            log::error!("Cannot handle position update: no position ID found for fill {fill}");
            return;
        };

        let position_opt = self.cache.borrow().position(&position_id).cloned();

        match position_opt {
            None => {
                // Position is None - open new position
                if self.open_position(instrument, None, fill, oms_type).is_ok() {
                    // Position opened successfully
                }
            }
            Some(pos) if pos.is_closed() => {
                // Position is closed - open new position
                if self
                    .open_position(instrument, Some(&pos), fill, oms_type)
                    .is_ok()
                {
                    // Position opened successfully
                }
            }
            Some(mut pos) => {
                if self.will_flip_position(&pos, fill) {
                    // Position will flip
                    self.flip_position(instrument, &mut pos, fill, oms_type);
                } else {
                    // Update existing position
                    self.update_position(&mut pos, fill);
                }
            }
        }
    }

    fn open_position(
        &self,
        instrument: InstrumentAny,
        position: Option<&Position>,
        fill: OrderFilled,
        oms_type: OmsType,
    ) -> anyhow::Result<()> {
        if let Some(position) = position {
            if Self::is_duplicate_closed_fill(position, &fill) {
                log::warn!(
                    "Ignoring duplicate fill {} for closed position {}; no position reopened (side={:?}, qty={}, px={})",
                    fill.trade_id,
                    position.id,
                    fill.order_side,
                    fill.last_qty,
                    fill.last_px
                );
                return Ok(());
            }
            self.reopen_position(position, oms_type)?;
        }

        let position = Position::new(&instrument, fill);
        self.cache
            .borrow_mut()
            .add_position(position.clone(), oms_type)?; // TODO: Remove clone (change method)

        if self.config.snapshot_positions {
            self.create_position_state_snapshot(&position);
        }

        let ts_init = self.clock.borrow().timestamp_ns();
        let event = PositionOpened::create(&position, &fill, UUID4::new(), ts_init);
        let topic = switchboard::get_event_positions_topic(event.strategy_id);
        msgbus::publish(topic, &PositionEvent::PositionOpened(event));

        Ok(())
    }

    fn is_duplicate_closed_fill(position: &Position, fill: &OrderFilled) -> bool {
        position.events.iter().any(|event| {
            event.trade_id == fill.trade_id
                && event.order_side == fill.order_side
                && event.last_px == fill.last_px
                && event.last_qty == fill.last_qty
        })
    }

    fn reopen_position(&self, position: &Position, oms_type: OmsType) -> anyhow::Result<()> {
        if oms_type == OmsType::Netting {
            if position.is_open() {
                anyhow::bail!(
                    "Cannot reopen position {} (oms_type=NETTING): reopening is only valid for closed positions in NETTING mode",
                    position.id
                );
            }
            // Snapshot closed position if reopening (NETTING mode)
            self.cache.borrow_mut().snapshot_position(position)?;
        } else {
            // HEDGING mode
            log::warn!(
                "Received fill for closed position {} in HEDGING mode; creating new position and ignoring previous state",
                position.id
            );
        }
        Ok(())
    }

    fn update_position(&self, position: &mut Position, fill: OrderFilled) {
        // Apply the fill to the position
        position.apply(&fill);

        // Check if position is closed after applying the fill
        let is_closed = position.is_closed();

        // Update position in cache - this should handle the closed state tracking
        if let Err(e) = self.cache.borrow_mut().update_position(position) {
            log::error!("Failed to update position: {e:?}");
            return;
        }

        // Verify cache state after update
        let cache = self.cache.borrow();

        drop(cache);

        // Create position state snapshot if enabled
        if self.config.snapshot_positions {
            self.create_position_state_snapshot(position);
        }

        // Create and publish appropriate position event
        let topic = switchboard::get_event_positions_topic(position.strategy_id);
        let ts_init = self.clock.borrow().timestamp_ns();

        if is_closed {
            let event = PositionClosed::create(position, &fill, UUID4::new(), ts_init);
            msgbus::publish(topic, &PositionEvent::PositionClosed(event));
        } else {
            let event = PositionChanged::create(position, &fill, UUID4::new(), ts_init);
            msgbus::publish(topic, &PositionEvent::PositionChanged(event));
        }
    }

    fn will_flip_position(&self, position: &Position, fill: OrderFilled) -> bool {
        position.is_opposite_side(fill.order_side) && (fill.last_qty.raw > position.quantity.raw)
    }

    fn flip_position(
        &mut self,
        instrument: InstrumentAny,
        position: &mut Position,
        fill: OrderFilled,
        oms_type: OmsType,
    ) {
        let difference = match position.side {
            PositionSide::Long => Quantity::from_raw(
                fill.last_qty.raw - position.quantity.raw,
                position.size_precision,
            ),
            PositionSide::Short => Quantity::from_raw(
                position.quantity.raw.abs_diff(fill.last_qty.raw), // Equivalent to Python's abs(position.quantity - fill.last_qty)
                position.size_precision,
            ),
            _ => fill.last_qty,
        };

        // Split commission between two positions
        let fill_percent = position.quantity.as_f64() / fill.last_qty.as_f64();
        let (commission1, commission2) = if let Some(commission) = fill.commission {
            let commission_currency = commission.currency;
            let commission1 = Money::new(commission * fill_percent, commission_currency);
            let commission2 = commission - commission1;
            (Some(commission1), Some(commission2))
        } else {
            log::error!("Commission is not available.");
            (None, None)
        };

        let mut fill_split1: Option<OrderFilled> = None;
        if position.is_open() {
            fill_split1 = Some(OrderFilled::new(
                fill.trader_id,
                fill.strategy_id,
                fill.instrument_id,
                fill.client_order_id,
                fill.venue_order_id,
                fill.account_id,
                fill.trade_id,
                fill.order_side,
                fill.order_type,
                position.quantity,
                fill.last_px,
                fill.currency,
                fill.liquidity_side,
                UUID4::new(),
                fill.ts_event,
                fill.ts_init,
                fill.reconciliation,
                fill.position_id,
                commission1,
            ));

            self.update_position(position, fill_split1.unwrap());

            // Snapshot closed position before reusing ID (NETTING mode)
            if oms_type == OmsType::Netting
                && let Err(e) = self.cache.borrow_mut().snapshot_position(position)
            {
                log::error!("Failed to snapshot position during flip: {e:?}");
            }
        }

        // Guard against flipping a position with a zero fill size
        if difference.raw == 0 {
            log::warn!(
                "Zero fill size during position flip calculation, this could be caused by a mismatch between instrument `size_precision` and a quantity `size_precision`"
            );
            return;
        }

        let position_id_flip = if oms_type == OmsType::Hedging
            && let Some(position_id) = fill.position_id
            && position_id.is_virtual()
        {
            // Generate new position ID for flipped virtual position (Hedging OMS only)
            Some(self.pos_id_generator.generate(fill.strategy_id, true))
        } else {
            // Default: use the same position ID as the fill (Python behavior)
            fill.position_id
        };

        let fill_split2 = OrderFilled::new(
            fill.trader_id,
            fill.strategy_id,
            fill.instrument_id,
            fill.client_order_id,
            fill.venue_order_id,
            fill.account_id,
            fill.trade_id,
            fill.order_side,
            fill.order_type,
            difference,
            fill.last_px,
            fill.currency,
            fill.liquidity_side,
            UUID4::new(),
            fill.ts_event,
            fill.ts_init,
            fill.reconciliation,
            position_id_flip,
            commission2,
        );

        if oms_type == OmsType::Hedging
            && let Some(position_id) = fill.position_id
            && position_id.is_virtual()
        {
            log::warn!("Closing position {fill_split1:?}");
            log::warn!("Flipping position {fill_split2:?}");
        }

        // Open flipped position
        if let Err(e) = self.open_position(instrument, None, fill_split2, oms_type) {
            log::error!("Failed to open flipped position: {e:?}");
        }
    }

    // -- INTERNAL --------------------------------------------------------------------------------

    fn set_position_id_counts(&mut self) {
        // For the internal position ID generator
        let cache = self.cache.borrow();
        let positions = cache.positions(None, None, None, None);

        // Count positions per instrument_id using a HashMap
        let mut counts: HashMap<StrategyId, usize> = HashMap::new();

        for position in positions {
            *counts.entry(position.strategy_id).or_insert(0) += 1;
        }

        self.pos_id_generator.reset();

        for (strategy_id, count) in counts {
            self.pos_id_generator.set_count(count, strategy_id);
            log::info!("Set PositionId count for {strategy_id} to {count}");
        }
    }

    fn last_px_for_conversion(
        &self,
        instrument_id: &InstrumentId,
        side: OrderSide,
    ) -> Option<Price> {
        let cache = self.cache.borrow();

        // Try to get last trade price
        if let Some(trade) = cache.trade(instrument_id) {
            return Some(trade.price);
        }

        // Fall back to quote if available
        if let Some(quote) = cache.quote(instrument_id) {
            match side {
                OrderSide::Buy => Some(quote.ask_price),
                OrderSide::Sell => Some(quote.bid_price),
                OrderSide::NoOrderSide => None,
            }
        } else {
            None
        }
    }

    fn set_order_base_qty(&self, order: &mut OrderAny, base_qty: Quantity) {
        log::info!(
            "Setting {} order quote quantity {} to base quantity {}",
            order.instrument_id(),
            order.quantity(),
            base_qty
        );

        let original_qty = order.quantity();
        order.set_quantity(base_qty);
        order.set_leaves_qty(base_qty);
        order.set_is_quote_quantity(false);

        if matches!(order.contingency_type(), Some(ContingencyType::Oto)) {
            return;
        }

        if let Some(linked_order_ids) = order.linked_order_ids() {
            for client_order_id in linked_order_ids {
                match self.cache.borrow_mut().mut_order(client_order_id) {
                    Some(contingent_order) => {
                        if !contingent_order.is_quote_quantity() {
                            continue; // Already base quantity
                        }

                        if contingent_order.quantity() != original_qty {
                            log::warn!(
                                "Contingent order quantity {} was not equal to the OTO parent original quantity {} when setting to base quantity of {}",
                                contingent_order.quantity(),
                                original_qty,
                                base_qty
                            );
                        }

                        log::info!(
                            "Setting {} order quote quantity {} to base quantity {}",
                            contingent_order.instrument_id(),
                            contingent_order.quantity(),
                            base_qty
                        );

                        contingent_order.set_quantity(base_qty);
                        contingent_order.set_leaves_qty(base_qty);
                        contingent_order.set_is_quote_quantity(false);
                    }
                    None => {
                        log::error!("Contingency order {client_order_id} not found");
                    }
                }
            }
        } else {
            log::warn!(
                "No linked order IDs found for order {}",
                order.client_order_id()
            );
        }
    }

    fn deny_order(&self, order: &OrderAny, reason: &str) {
        log::error!(
            "Order denied: {reason}, order ID: {}",
            order.client_order_id()
        );

        let denied = OrderDenied::new(
            order.trader_id(),
            order.strategy_id(),
            order.instrument_id(),
            order.client_order_id(),
            reason.into(),
            UUID4::new(),
            self.clock.borrow().timestamp_ns(),
            self.clock.borrow().timestamp_ns(),
        );

        let mut order = order.clone();

        if let Err(e) = order.apply(OrderEventAny::Denied(denied)) {
            log::error!("Failed to apply denied event to order: {e}");
            return;
        }

        if let Err(e) = self.cache.borrow_mut().update_order(&order) {
            log::error!("Failed to update order in cache: {e}");
            return;
        }

        let topic = switchboard::get_event_orders_topic(order.strategy_id());
        msgbus::publish(topic, &OrderEventAny::Denied(denied));

        if self.config.snapshot_orders {
            self.create_order_state_snapshot(&order);
        }
    }

    fn get_or_init_own_order_book(&self, instrument_id: &InstrumentId) -> RefMut<'_, OwnOrderBook> {
        let mut cache = self.cache.borrow_mut();
        if cache.own_order_book_mut(instrument_id).is_none() {
            let own_book = OwnOrderBook::new(*instrument_id);
            cache.add_own_order_book(own_book).unwrap();
        }

        RefMut::map(cache, |c| c.own_order_book_mut(instrument_id).unwrap())
    }
}