nautilus_model/orders/

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.
// -------------------------------------------------------------------------------------------------

//! Order types for the trading domain model.
//!
//! Each order type wraps an [`OrderCore`] carrying the state common to all of them and adds its
//! own type-specific fields. [`OrderAny`] dispatches over the concrete types.
//!
//! Orders are event sourced. [`OrderCore::apply`] validates the status transition, runs the
//! handler for that event, then appends it, so [`OrderAny::from_events`] replays a stream to
//! reconstruct its event-derived state.
//!
//! A fill-void correction rebuilds the derived fill state from the fills that survive it.
//! `avg_px` folds those fills in `Decimal` and keeps the quotient at that precision, so no float
//! conversion enters the next average and a rebuild agrees with the incremental update over the
//! same fills. `slippage` derives from `avg_px` in the same arithmetic.

pub mod any;
pub mod limit;
pub mod limit_if_touched;
pub mod list;
pub mod market;
pub mod market_if_touched;
pub mod market_to_limit;
pub mod stop_limit;
pub mod stop_market;
pub mod trailing_stop_limit;
pub mod trailing_stop_market;

#[cfg(any(test, feature = "stubs"))]
pub mod builder;
#[cfg(any(test, feature = "stubs"))]
pub mod stubs;

// Re-exports
use ahash::AHashSet;
use enum_dispatch::enum_dispatch;
use indexmap::IndexMap;
use nautilus_core::{
    UUID4, UnixNanos,
    correctness::{CorrectnessError, check_predicate_false},
};
use rust_decimal::Decimal;
use serde::{Deserialize, Serialize};
use ustr::Ustr;

#[cfg(any(test, feature = "stubs"))]
pub use crate::orders::builder::OrderTestBuilder;
pub use crate::orders::{
    any::{LimitOrderAny, OrderAny, OrderReplayError, PassiveOrderAny, StopOrderAny},
    limit::LimitOrder,
    limit_if_touched::LimitIfTouchedOrder,
    list::{OrderList, OrderListValidationError},
    market::MarketOrder,
    market_if_touched::MarketIfTouchedOrder,
    market_to_limit::MarketToLimitOrder,
    stop_limit::StopLimitOrder,
    stop_market::StopMarketOrder,
    trailing_stop_limit::TrailingStopLimitOrder,
    trailing_stop_market::TrailingStopMarketOrder,
};
use crate::{
    enums::{
        ContingencyType, LiquiditySide, OrderSide, OrderSideSpecified, OrderStatus, OrderType,
        PositionSide, TimeInForce, TrailingOffsetType, TriggerType,
    },
    events::{
        OrderAccepted, OrderCancelRejected, OrderCanceled, OrderDenied, OrderEmulated,
        OrderEventAny, OrderExpired, OrderFillVoided, OrderFilled, OrderInitialized,
        OrderModifyRejected, OrderPendingCancel, OrderPendingUpdate, OrderRejected, OrderReleased,
        OrderSubmitted, OrderTriggered, OrderUpdated,
    },
    identifiers::{
        AccountId, ClientOrderId, ExecAlgorithmId, InstrumentId, OrderListId, PositionId,
        StrategyId, Symbol, TradeId, TraderId, Venue, VenueOrderId,
    },
    orderbook::OwnBookOrder,
    reports::OrderStatusReport,
    types::{
        Currency, Money, Price, Quantity,
        quantity::{QUANTITY_RAW_MAX, QuantityRaw},
    },
};

/// Order types that have stop/trigger prices.
pub const STOP_ORDER_TYPES: &[OrderType] = &[
    OrderType::StopMarket,
    OrderType::StopLimit,
    OrderType::MarketIfTouched,
    OrderType::LimitIfTouched,
];

/// Order types that have limit prices.
pub const LIMIT_ORDER_TYPES: &[OrderType] = &[
    OrderType::Limit,
    OrderType::StopLimit,
    OrderType::LimitIfTouched,
    OrderType::TrailingStopLimit,
];

/// Order types that support the TRIGGERED order status.
///
/// Market-style stops (`StopMarket`, `MarketIfTouched`, `TrailingStopMarket`) execute
/// immediately on trigger and have no intermediate TRIGGERED state.
pub const TRIGGERABLE_ORDER_TYPES: &[OrderType] = &[
    OrderType::StopLimit,
    OrderType::TrailingStopLimit,
    OrderType::LimitIfTouched,
];

/// Order statuses for locally active orders (pre-submission to venue).
pub const LOCAL_ACTIVE_ORDER_STATUSES: &[OrderStatus] = &[
    OrderStatus::Initialized,
    OrderStatus::Emulated,
    OrderStatus::Released,
];

#[derive(thiserror::Error, Debug)]
pub enum OrderError {
    #[error("Order not found: {0}")]
    NotFound(ClientOrderId),
    #[error("Order invariant failed: must have a side for this operation")]
    NoOrderSide,
    #[error("Invalid event for order type")]
    InvalidOrderEvent,
    #[error("Invalid order state transition")]
    InvalidStateTransition,
    #[error("Order was already initialized")]
    AlreadyInitialized,
    #[error("Order had no previous state")]
    NoPreviousState,
    #[error("Duplicate fill: trade_id {0} already applied to order")]
    DuplicateFill(TradeId),
    #[error("Duplicate fill void: trade_id {0} already has this cumulative correction")]
    DuplicateFillVoid(TradeId),
    #[error("Fill void for trade_id {0} is older than the applied correction")]
    StaleFillVoid(TradeId),
    #[error("Fill void quantity exceeds the original fill for trade_id {0}")]
    OverVoid(TradeId),
    #[error("Fill void commission is missing or conflicts with trade_id {0}")]
    InvalidFillVoidCommission(TradeId),
    #[error("{0}")]
    Invariant(#[from] CorrectnessError),
}

/// Converts an `IndexMap` with `Ustr` keys and values to `String` keys and values.
#[must_use]
pub fn ustr_indexmap_to_str(h: IndexMap<Ustr, Ustr>) -> IndexMap<String, String> {
    h.into_iter()
        .map(|(k, v)| (k.to_string(), v.to_string()))
        .collect()
}

/// Converts an `IndexMap` with `String` keys and values to `Ustr` keys and values.
#[must_use]
pub fn str_indexmap_to_ustr(h: IndexMap<String, String>) -> IndexMap<Ustr, Ustr> {
    h.into_iter()
        .map(|(k, v)| (Ustr::from(&k), Ustr::from(&v)))
        .collect()
}

#[inline]
pub(crate) fn check_display_qty(
    display_qty: Option<Quantity>,
    quantity: Quantity,
) -> Result<(), OrderError> {
    if let Some(q) = display_qty {
        check_predicate_false(q > quantity, "`display_qty` may not exceed `quantity`")?;
    }
    Ok(())
}

#[inline]
pub(crate) fn check_time_in_force(
    time_in_force: TimeInForce,
    expire_time: Option<UnixNanos>,
) -> Result<(), OrderError> {
    check_predicate_false(
        time_in_force == TimeInForce::Gtd && expire_time.unwrap_or_default() == 0,
        "`expire_time` is required for `GTD` order",
    )?;
    Ok(())
}

#[inline]
fn checked_quantity_raw_sum(lhs: QuantityRaw, rhs: QuantityRaw) -> Option<QuantityRaw> {
    lhs.checked_add(rhs).filter(|raw| *raw <= QUANTITY_RAW_MAX)
}

#[inline]
fn quantity_from_domain_raw(raw: QuantityRaw, precision: u8) -> Quantity {
    Quantity::from_raw(raw.min(QUANTITY_RAW_MAX), precision)
}

impl OrderStatus {
    /// Transitions the order state machine based on the given `event`.
    ///
    /// # Errors
    ///
    /// Returns an error if the state transition is invalid from the current status.
    #[rustfmt::skip]
    pub fn transition(&mut self, event: &OrderEventAny) -> Result<Self, OrderError> {
        let new_state = match (self, event) {
            (Self::Initialized, OrderEventAny::Denied(_)) => Self::Denied,
            (Self::Initialized, OrderEventAny::Emulated(_)) => Self::Emulated,  // Emulated orders
            (Self::Initialized, OrderEventAny::Released(_)) => Self::Released,  // Emulated orders
            (Self::Initialized, OrderEventAny::Submitted(_)) => Self::Submitted,
            (Self::Initialized, OrderEventAny::Rejected(_)) => Self::Rejected,  // External orders
            (Self::Initialized, OrderEventAny::Accepted(_)) => Self::Accepted,  // External orders
            (Self::Initialized, OrderEventAny::Canceled(_)) => Self::Canceled,  // External orders
            (Self::Initialized, OrderEventAny::Expired(_)) => Self::Expired,  // External orders
            (Self::Initialized, OrderEventAny::Triggered(_)) => Self::Triggered, // External orders
            (Self::Initialized, OrderEventAny::Updated(_)) => Self::Initialized, // In-place modification
            (Self::Emulated, OrderEventAny::Canceled(_)) => Self::Canceled,  // Emulated orders
            (Self::Emulated, OrderEventAny::Expired(_)) => Self::Expired,  // Emulated orders
            (Self::Emulated, OrderEventAny::Updated(_)) => Self::Emulated, // In-place modification
            (Self::Emulated, OrderEventAny::Released(_)) => Self::Released,  // Emulated orders
            (Self::Released, OrderEventAny::Submitted(_)) => Self::Submitted,  // Emulated orders
            (Self::Released, OrderEventAny::Denied(_)) => Self::Denied,  // Emulated orders
            (Self::Released, OrderEventAny::Canceled(_)) => Self::Canceled,  // Execution algo
            (Self::Released, OrderEventAny::Updated(_)) => Self::Released, // In-place modification
            (Self::Submitted, OrderEventAny::PendingUpdate(_)) => Self::PendingUpdate,
            (Self::Submitted, OrderEventAny::PendingCancel(_)) => Self::PendingCancel,
            (Self::Submitted, OrderEventAny::Rejected(_)) => Self::Rejected,
            (Self::Submitted, OrderEventAny::Canceled(_)) => Self::Canceled,  // FOK and IOC cases
            (Self::Submitted, OrderEventAny::Accepted(_)) => Self::Accepted,
            (Self::Submitted, OrderEventAny::Updated(_)) => Self::Submitted,
            (Self::Submitted, OrderEventAny::Filled(_)) => Self::Filled,
            (Self::Accepted, OrderEventAny::Rejected(_)) => Self::Rejected,  // StopLimit order
            (Self::Accepted, OrderEventAny::PendingUpdate(_)) => Self::PendingUpdate,
            (Self::Accepted, OrderEventAny::PendingCancel(_)) => Self::PendingCancel,
            (Self::Accepted, OrderEventAny::Canceled(_)) => Self::Canceled,
            (Self::Accepted, OrderEventAny::Triggered(_)) => Self::Triggered,
            (Self::Accepted, OrderEventAny::Updated(_)) => Self::Accepted,  // Updates should preserve state
            (Self::Accepted, OrderEventAny::Expired(_)) => Self::Expired,
            (Self::Accepted, OrderEventAny::Filled(_)) => Self::Filled,
            (Self::Accepted, OrderEventAny::FillVoided(_)) => Self::Accepted,
            (Self::Canceled, OrderEventAny::Filled(_)) => Self::Filled,  // Real world possibility
            (Self::Canceled, OrderEventAny::FillVoided(_)) => Self::Canceled,
            (Self::Canceled, OrderEventAny::Updated(_)) => Self::Canceled,
            (Self::PendingUpdate, OrderEventAny::Rejected(_)) => Self::Rejected,
            (Self::PendingUpdate, OrderEventAny::Accepted(_)) => Self::Accepted,
            (Self::PendingUpdate, OrderEventAny::Canceled(_)) => Self::Canceled,
            (Self::PendingUpdate, OrderEventAny::Expired(_)) => Self::Expired,
            (Self::PendingUpdate, OrderEventAny::Triggered(_)) => Self::Triggered,
            (Self::PendingUpdate, OrderEventAny::Submitted(_)) => Self::PendingUpdate,  // Real world possibility
            (Self::PendingUpdate, OrderEventAny::PendingUpdate(_)) => Self::PendingUpdate,  // Allow multiple requests
            (Self::PendingUpdate, OrderEventAny::PendingCancel(_)) => Self::PendingCancel,
            (Self::PendingUpdate, OrderEventAny::ModifyRejected(_)) => Self::PendingUpdate,  // Handled by modify_rejected to restore previous_status
            (Self::PendingUpdate, OrderEventAny::Updated(_)) => Self::PendingUpdate,  // Handled by updated to restore previous_status
            (Self::PendingUpdate, OrderEventAny::Filled(_)) => Self::Filled,
            (Self::PendingUpdate, OrderEventAny::FillVoided(_)) => Self::PendingUpdate,
            (Self::PendingCancel, OrderEventAny::Rejected(_)) => Self::Rejected,
            (Self::PendingCancel, OrderEventAny::PendingCancel(_)) => Self::PendingCancel,  // Allow multiple requests
            (Self::PendingCancel, OrderEventAny::CancelRejected(_)) => Self::PendingCancel,  // Handled by cancel_rejected to restore previous_status
            (Self::PendingCancel, OrderEventAny::Canceled(_)) => Self::Canceled,
            (Self::PendingCancel, OrderEventAny::Expired(_)) => Self::Expired,
            (Self::PendingCancel, OrderEventAny::Accepted(_)) => Self::Accepted,  // Allow failed cancel requests
            (Self::PendingCancel, OrderEventAny::Updated(_)) => Self::PendingCancel,  // Handled by updated to restore previous_status
            (Self::PendingCancel, OrderEventAny::Filled(_)) => Self::Filled,
            (Self::PendingCancel, OrderEventAny::FillVoided(_)) => Self::PendingCancel,
            (Self::Triggered, OrderEventAny::Rejected(_)) => Self::Rejected,
            (Self::Triggered, OrderEventAny::PendingUpdate(_)) => Self::PendingUpdate,
            (Self::Triggered, OrderEventAny::PendingCancel(_)) => Self::PendingCancel,
            (Self::Triggered, OrderEventAny::Canceled(_)) => Self::Canceled,
            (Self::Triggered, OrderEventAny::Expired(_)) => Self::Expired,
            (Self::Triggered, OrderEventAny::Filled(_)) => Self::Filled,
            (Self::Triggered, OrderEventAny::Updated(_)) => Self::Triggered,
            (Self::Triggered, OrderEventAny::FillVoided(_)) => Self::Triggered,
            (Self::PartiallyFilled, OrderEventAny::PendingUpdate(_)) => Self::PendingUpdate,
            (Self::PartiallyFilled, OrderEventAny::PendingCancel(_)) => Self::PendingCancel,
            (Self::PartiallyFilled, OrderEventAny::Canceled(_)) => Self::Canceled,
            (Self::PartiallyFilled, OrderEventAny::Expired(_)) => Self::Expired,
            (Self::PartiallyFilled, OrderEventAny::Filled(_)) => Self::Filled,
            (Self::PartiallyFilled, OrderEventAny::Accepted(_)) => Self::Accepted,
            (Self::PartiallyFilled, OrderEventAny::Updated(_)) => Self::PartiallyFilled,
            (Self::PartiallyFilled, OrderEventAny::FillVoided(_)) => Self::PartiallyFilled,
            (Self::Filled, OrderEventAny::FillVoided(_)) => Self::Voided,
            (Self::Filled, OrderEventAny::Updated(_)) => Self::Filled,
            (Self::Expired, OrderEventAny::FillVoided(_)) => Self::Expired,
            (Self::Expired, OrderEventAny::Updated(_)) => Self::Expired,
            (Self::Voided, OrderEventAny::FillVoided(_)) => Self::Voided,
            _ => return Err(OrderError::InvalidStateTransition),
        };
        Ok(new_state)
    }
}

#[enum_dispatch]
pub trait Order: 'static + Send {
    fn into_any(self) -> OrderAny;
    fn status(&self) -> OrderStatus;
    fn trader_id(&self) -> TraderId;
    fn strategy_id(&self) -> StrategyId;
    fn instrument_id(&self) -> InstrumentId;
    fn symbol(&self) -> Symbol;
    fn venue(&self) -> Venue;
    fn client_order_id(&self) -> ClientOrderId;
    fn venue_order_id(&self) -> Option<VenueOrderId>;
    fn position_id(&self) -> Option<PositionId>;
    fn account_id(&self) -> Option<AccountId>;
    fn last_trade_id(&self) -> Option<TradeId>;
    fn order_side(&self) -> OrderSide;
    fn order_type(&self) -> OrderType;
    fn quantity(&self) -> Quantity;
    fn time_in_force(&self) -> TimeInForce;
    fn expire_time(&self) -> Option<UnixNanos>;
    fn price(&self) -> Option<Price>;
    fn activation_price(&self) -> Option<Price> {
        None
    }
    fn trigger_price(&self) -> Option<Price>;
    fn trigger_type(&self) -> Option<TriggerType>;
    fn liquidity_side(&self) -> Option<LiquiditySide>;
    fn is_post_only(&self) -> bool;
    fn is_reduce_only(&self) -> bool;
    fn is_quote_quantity(&self) -> bool;
    fn display_qty(&self) -> Option<Quantity>;
    fn limit_offset(&self) -> Option<Decimal>;
    fn trailing_offset(&self) -> Option<Decimal>;
    fn trailing_offset_type(&self) -> Option<TrailingOffsetType>;
    fn emulation_trigger(&self) -> Option<TriggerType>;
    fn trigger_instrument_id(&self) -> Option<InstrumentId>;
    fn contingency_type(&self) -> Option<ContingencyType>;
    fn order_list_id(&self) -> Option<OrderListId>;
    fn linked_order_ids(&self) -> Option<&[ClientOrderId]>;
    fn parent_order_id(&self) -> Option<ClientOrderId>;
    fn exec_algorithm_id(&self) -> Option<ExecAlgorithmId>;
    fn exec_algorithm_params(&self) -> Option<&IndexMap<Ustr, Ustr>>;
    fn exec_spawn_id(&self) -> Option<ClientOrderId>;
    fn tags(&self) -> Option<&[Ustr]>;
    fn filled_qty(&self) -> Quantity;
    fn voided_qty(&self) -> Quantity;
    fn leaves_qty(&self) -> Quantity;
    fn overfill_qty(&self) -> Quantity;

    /// Calculates potential overfill quantity without mutating order state.
    fn calculate_overfill(&self, fill_qty: Quantity) -> Quantity {
        let potential_filled = self.filled_qty() + fill_qty;
        let quantity = self.quantity();
        if potential_filled > quantity {
            potential_filled - quantity
        } else {
            Quantity::zero(fill_qty.precision)
        }
    }

    fn avg_px(&self) -> Option<Decimal>;
    fn slippage(&self) -> Option<Decimal>;
    fn init_id(&self) -> UUID4;
    fn ts_init(&self) -> UnixNanos;
    fn ts_submitted(&self) -> Option<UnixNanos>;
    fn ts_accepted(&self) -> Option<UnixNanos>;
    fn ts_closed(&self) -> Option<UnixNanos>;
    fn ts_last(&self) -> UnixNanos;

    fn order_side_specified(&self) -> OrderSideSpecified {
        self.order_side().as_specified()
    }
    fn commissions(&self) -> &IndexMap<Currency, Money>;

    /// Applies the `event` to the order.
    ///
    /// # Errors
    ///
    /// Returns an error if the event is invalid for the current order status.
    fn apply(&mut self, event: OrderEventAny) -> Result<(), OrderError>;

    fn update(&mut self, event: &OrderUpdated);

    fn events(&self) -> Vec<&OrderEventAny>;

    fn last_event(&self) -> &OrderEventAny {
        self.events()
            .last()
            .expect("Order invariant violated: no events")
    }

    fn event_count(&self) -> usize {
        self.events().len()
    }

    fn venue_order_ids(&self) -> Vec<&VenueOrderId>;

    fn trade_ids(&self) -> Vec<&TradeId>;

    fn has_price(&self) -> bool;

    /// Returns `true` if a fill with matching `trade_id`, side, qty, and price already exists.
    fn is_duplicate_fill(&self, fill: &OrderFilled) -> bool {
        self.events().iter().any(|event| {
            if let OrderEventAny::Filled(existing) = event {
                existing.trade_id == fill.trade_id
                    && existing.order_side == fill.order_side
                    && existing.last_qty == fill.last_qty
                    && existing.last_px == fill.last_px
            } else {
                false
            }
        })
    }

    fn is_buy(&self) -> bool {
        self.order_side() == OrderSide::Buy
    }

    fn is_sell(&self) -> bool {
        self.order_side() == OrderSide::Sell
    }

    fn is_passive(&self) -> bool {
        self.order_type() != OrderType::Market
    }

    fn is_aggressive(&self) -> bool {
        self.order_type() == OrderType::Market
    }

    fn is_emulated(&self) -> bool {
        self.status() == OrderStatus::Emulated
    }

    fn is_active_local(&self) -> bool {
        matches!(
            self.status(),
            OrderStatus::Initialized | OrderStatus::Emulated | OrderStatus::Released
        )
    }

    fn is_primary(&self) -> bool {
        self.exec_algorithm_id().is_some()
            && self
                .exec_spawn_id()
                .is_some_and(|spawn_id| self.client_order_id() == spawn_id)
    }

    fn is_spawned(&self) -> bool {
        self.exec_algorithm_id().is_some()
            && self
                .exec_spawn_id()
                .is_some_and(|spawn_id| self.client_order_id() != spawn_id)
    }

    fn is_contingency(&self) -> bool {
        self.contingency_type().is_some()
    }

    fn is_parent_order(&self) -> bool {
        match self.contingency_type() {
            Some(c) => c == ContingencyType::Oto,
            None => false,
        }
    }

    fn is_child_order(&self) -> bool {
        self.parent_order_id().is_some()
    }

    fn is_open(&self) -> bool {
        if let Some(emulation_trigger) = self.emulation_trigger()
            && emulation_trigger != TriggerType::NoTrigger
        {
            return false;
        }

        matches!(
            self.status(),
            OrderStatus::Accepted
                | OrderStatus::Triggered
                | OrderStatus::PendingCancel
                | OrderStatus::PendingUpdate
                | OrderStatus::PartiallyFilled
        )
    }

    fn is_canceled(&self) -> bool {
        self.status() == OrderStatus::Canceled
    }

    fn is_closed(&self) -> bool {
        matches!(
            self.status(),
            OrderStatus::Denied
                | OrderStatus::Rejected
                | OrderStatus::Canceled
                | OrderStatus::Expired
                | OrderStatus::Filled
                | OrderStatus::Voided
        )
    }

    fn is_inflight(&self) -> bool {
        if let Some(emulation_trigger) = self.emulation_trigger()
            && emulation_trigger != TriggerType::NoTrigger
        {
            return false;
        }

        matches!(
            self.status(),
            OrderStatus::Submitted | OrderStatus::PendingCancel | OrderStatus::PendingUpdate
        )
    }

    fn is_pending_update(&self) -> bool {
        self.status() == OrderStatus::PendingUpdate
    }

    fn is_pending_cancel(&self) -> bool {
        self.status() == OrderStatus::PendingCancel
    }

    fn to_own_book_order(&self) -> OwnBookOrder {
        OwnBookOrder::new(
            self.trader_id(),
            self.client_order_id(),
            self.venue_order_id(),
            self.order_side().as_specified(),
            self.price().expect("`OwnBookOrder` must have a price"),
            self.leaves_qty(),
            self.order_type(),
            self.time_in_force(),
            self.status(),
            self.ts_last(),
            self.ts_accepted().unwrap_or_default(),
            self.ts_submitted().unwrap_or_default(),
            self.ts_init(),
        )
    }

    /// Builds an [`OrderStatusReport`] snapshot from the order's current state.
    ///
    /// Returns `None` if the order has no `venue_order_id` or `account_id`:
    /// a status report describes a venue-acknowledged order, and both fields
    /// are set by the time a venue acknowledges the order.
    fn to_order_status_report(&self, report_id: Option<UUID4>) -> Option<OrderStatusReport> {
        let account_id = self.account_id()?;
        let venue_order_id = self.venue_order_id()?;

        let mut report = OrderStatusReport::new(
            account_id,
            self.instrument_id(),
            Some(self.client_order_id()),
            venue_order_id,
            self.order_side(),
            self.order_type(),
            self.time_in_force(),
            self.status(),
            self.quantity(),
            self.filled_qty(),
            self.ts_accepted().unwrap_or_else(|| self.ts_last()),
            self.ts_last(),
            self.ts_init(),
            report_id,
        )
        .with_post_only(self.is_post_only())
        .with_reduce_only(self.is_reduce_only());

        if let Some(price) = self.price() {
            report = report.with_price(price);
        }

        if let Some(activation_price) = self.activation_price() {
            report = report.with_activation_price(activation_price);
        }

        if let Some(trigger_price) = self.trigger_price() {
            report = report.with_trigger_price(trigger_price);
        }

        if let Some(trigger_type) = self.trigger_type() {
            report = report.with_trigger_type(trigger_type);
        }

        if let Some(limit_offset) = self.limit_offset() {
            report = report.with_limit_offset(limit_offset);
        }

        if let Some(trailing_offset) = self.trailing_offset() {
            report = report.with_trailing_offset(trailing_offset);
        }

        if let Some(trailing_offset_type) = self.trailing_offset_type() {
            report = report.with_trailing_offset_type(trailing_offset_type);
        }

        if let Some(display_qty) = self.display_qty() {
            report = report.with_display_qty(display_qty);
        }

        if let Some(expire_time) = self.expire_time() {
            report = report.with_expire_time(expire_time);
        }

        if let Some(contingency_type) = self.contingency_type() {
            report = report.with_contingency_type(contingency_type);
        }

        if let Some(order_list_id) = self.order_list_id() {
            report = report.with_order_list_id(order_list_id);
        }

        if let Some(linked_order_ids) = self.linked_order_ids() {
            report = report.with_linked_order_ids(linked_order_ids.iter().copied());
        }

        if let Some(parent_order_id) = self.parent_order_id() {
            report = report.with_parent_order_id(parent_order_id);
        }

        if let Some(position_id) = self.position_id() {
            report = report.with_venue_position_id(position_id);
        }

        // The trait exposes no trigger or rejection metadata accessors,
        // recover the last occurrences from the event history.
        let mut ts_triggered = None;
        let mut rejected_reason = None;

        for event in self.events() {
            match event {
                OrderEventAny::Triggered(triggered) => ts_triggered = Some(triggered.ts_event),
                OrderEventAny::Rejected(rejected) => rejected_reason = Some(rejected.reason),
                _ => {}
            }
        }

        if let Some(ts_triggered) = ts_triggered {
            report = report.with_ts_triggered(ts_triggered);
        }

        // `cancel_reason` is the report's only reason channel,
        // reconciliation reads it for rejected orders.
        if let Some(reason) = rejected_reason {
            report = report.with_cancel_reason(reason.to_string());
        }

        if let Some(avg_px) = self.avg_px() {
            report = report.with_avg_px(avg_px);
        }

        Some(report)
    }

    fn is_triggered(&self) -> Option<bool>; // TODO: Temporary on trait
    fn set_position_id(&mut self, position_id: Option<PositionId>);
    fn set_quantity(&mut self, quantity: Quantity);
    fn set_leaves_qty(&mut self, leaves_qty: Quantity);
    fn set_emulation_trigger(&mut self, emulation_trigger: Option<TriggerType>);
    fn set_is_quote_quantity(&mut self, is_quote_quantity: bool);
    fn set_liquidity_side(&mut self, liquidity_side: LiquiditySide);
    fn would_reduce_only(&self, side: PositionSide, position_qty: Quantity) -> bool;
    fn previous_status(&self) -> Option<OrderStatus>;
}

impl<T> From<&T> for OrderInitialized
where
    T: Order,
{
    fn from(order: &T) -> Self {
        Self {
            trader_id: order.trader_id(),
            strategy_id: order.strategy_id(),
            instrument_id: order.instrument_id(),
            client_order_id: order.client_order_id(),
            order_side: order.order_side(),
            order_type: order.order_type(),
            quantity: order.quantity(),
            price: order.price(),
            activation_price: order.activation_price(),
            trigger_price: order.trigger_price(),
            trigger_type: order.trigger_type(),
            time_in_force: order.time_in_force(),
            expire_time: order.expire_time(),
            post_only: order.is_post_only(),
            reduce_only: order.is_reduce_only(),
            quote_quantity: order.is_quote_quantity(),
            display_qty: order.display_qty(),
            limit_offset: order.limit_offset(),
            trailing_offset: order.trailing_offset(),
            trailing_offset_type: order.trailing_offset_type(),
            emulation_trigger: order.emulation_trigger(),
            trigger_instrument_id: order.trigger_instrument_id(),
            contingency_type: order.contingency_type(),
            order_list_id: order.order_list_id(),
            linked_order_ids: order.linked_order_ids().map(<[ClientOrderId]>::to_vec),
            parent_order_id: order.parent_order_id(),
            exec_algorithm_id: order.exec_algorithm_id(),
            exec_algorithm_params: order.exec_algorithm_params().map(ToOwned::to_owned),
            exec_spawn_id: order.exec_spawn_id(),
            tags: order.tags().map(<[Ustr]>::to_vec),
            event_id: order.init_id(),
            ts_event: order.ts_init(),
            ts_init: order.ts_init(),
            reconciliation: false,
            causation_id: None,
        }
    }
}

#[derive(Clone, Debug, Serialize, Deserialize)]
pub struct OrderCore {
    pub events: Vec<OrderEventAny>,
    pub commissions: IndexMap<Currency, Money>,
    pub venue_order_ids: Vec<VenueOrderId>,
    pub trade_ids: Vec<TradeId>,
    pub previous_status: Option<OrderStatus>,
    pub status: OrderStatus,
    pub trader_id: TraderId,
    pub strategy_id: StrategyId,
    pub instrument_id: InstrumentId,
    pub client_order_id: ClientOrderId,
    pub venue_order_id: Option<VenueOrderId>,
    pub position_id: Option<PositionId>,
    pub account_id: Option<AccountId>,
    pub last_trade_id: Option<TradeId>,
    pub side: OrderSide,
    pub order_type: OrderType,
    pub quantity: Quantity,
    pub time_in_force: TimeInForce,
    pub liquidity_side: Option<LiquiditySide>,
    pub is_reduce_only: bool,
    pub is_quote_quantity: bool,
    pub emulation_trigger: Option<TriggerType>,
    pub contingency_type: Option<ContingencyType>,
    pub order_list_id: Option<OrderListId>,
    pub linked_order_ids: Option<Vec<ClientOrderId>>,
    pub parent_order_id: Option<ClientOrderId>,
    pub exec_algorithm_id: Option<ExecAlgorithmId>,
    pub exec_algorithm_params: Option<IndexMap<Ustr, Ustr>>,
    pub exec_spawn_id: Option<ClientOrderId>,
    pub tags: Option<Vec<Ustr>>,
    pub filled_qty: Quantity,
    #[serde(default)]
    pub voided_qty: Quantity,
    pub leaves_qty: Quantity,
    pub overfill_qty: Quantity,
    pub avg_px: Option<Decimal>,
    pub slippage: Option<Decimal>,
    pub init_id: UUID4,
    pub ts_init: UnixNanos,
    pub ts_submitted: Option<UnixNanos>,
    pub ts_accepted: Option<UnixNanos>,
    pub ts_closed: Option<UnixNanos>,
    pub ts_last: UnixNanos,
}

impl OrderCore {
    /// Creates a new [`OrderCore`] instance.
    #[must_use]
    pub fn new(init: OrderInitialized) -> Self {
        let events: Vec<OrderEventAny> = vec![OrderEventAny::Initialized(init.clone())];
        Self {
            events,
            commissions: IndexMap::new(),
            venue_order_ids: Vec::new(),
            trade_ids: Vec::new(),
            previous_status: None,
            status: OrderStatus::Initialized,
            trader_id: init.trader_id,
            strategy_id: init.strategy_id,
            instrument_id: init.instrument_id,
            client_order_id: init.client_order_id,
            venue_order_id: None,
            position_id: None,
            account_id: None,
            last_trade_id: None,
            side: init.order_side,
            order_type: init.order_type,
            quantity: init.quantity,
            time_in_force: init.time_in_force,
            liquidity_side: Some(LiquiditySide::NoLiquiditySide),
            is_reduce_only: init.reduce_only,
            is_quote_quantity: init.quote_quantity,
            emulation_trigger: init.emulation_trigger.or(Some(TriggerType::NoTrigger)),
            contingency_type: init
                .contingency_type
                .or(Some(ContingencyType::NoContingency)),
            order_list_id: init.order_list_id,
            linked_order_ids: init.linked_order_ids,
            parent_order_id: init.parent_order_id,
            exec_algorithm_id: init.exec_algorithm_id,
            exec_algorithm_params: init.exec_algorithm_params,
            exec_spawn_id: init.exec_spawn_id,
            tags: init.tags,
            filled_qty: Quantity::zero(init.quantity.precision),
            voided_qty: Quantity::zero(init.quantity.precision),
            leaves_qty: init.quantity,
            overfill_qty: Quantity::zero(init.quantity.precision),
            avg_px: None,
            slippage: None,
            init_id: init.event_id,
            ts_init: init.ts_event,
            ts_submitted: None,
            ts_accepted: None,
            ts_closed: None,
            ts_last: init.ts_event,
        }
    }

    /// Applies the `event` to the order.
    ///
    /// # Errors
    ///
    /// Returns an error if the event is invalid for the current order status, or if
    /// `event.client_order_id()` or `event.strategy_id()` does not match the order.
    pub fn apply(&mut self, event: OrderEventAny) -> Result<(), OrderError> {
        if self.client_order_id != event.client_order_id() {
            return Err(CorrectnessError::PredicateViolation {
                message: format!(
                    "Event client_order_id {} does not match order client_order_id {}",
                    event.client_order_id(),
                    self.client_order_id
                ),
            }
            .into());
        }

        if self.strategy_id != event.strategy_id() {
            return Err(CorrectnessError::PredicateViolation {
                message: format!(
                    "Event strategy_id {} does not match order strategy_id {}",
                    event.strategy_id(),
                    self.strategy_id
                ),
            }
            .into());
        }

        if let OrderEventAny::FillVoided(event) = &event {
            self.validate_fill_void(event)?;
        }

        // Check for duplicate fill before state transition to maintain consistency
        if let OrderEventAny::Filled(fill) = &event
            && self.events.iter().any(
                |event| matches!(event, OrderEventAny::Filled(existing) if existing.trade_id == fill.trade_id),
            )
        {
            return Err(OrderError::DuplicateFill(fill.trade_id));
        }

        if matches!(event, OrderEventAny::Triggered(_))
            && !TRIGGERABLE_ORDER_TYPES.contains(&self.order_type)
        {
            return Err(OrderError::InvalidOrderEvent);
        }

        if matches!(event, OrderEventAny::Initialized(_)) {
            return Err(OrderError::AlreadyInitialized);
        }

        let new_status = self.status.transition(&event)?;
        if let OrderEventAny::Filled(fill) = &event
            && checked_quantity_raw_sum(self.filled_qty.raw, fill.last_qty.raw).is_none()
        {
            return Err(CorrectnessError::PredicateViolation {
                message: format!(
                    "filled quantity overflowed Quantity raw bounds: {} + {}",
                    self.filled_qty, fill.last_qty
                ),
            }
            .into());
        }

        let rejection_status = if matches!(
            event,
            OrderEventAny::ModifyRejected(_) | OrderEventAny::CancelRejected(_)
        ) {
            self.previous_status.ok_or(OrderError::NoPreviousState)?
        } else {
            self.status
        };

        // Reject an update carrying fields the order type cannot hold before any
        // mutation. Runs after the identity and transition checks so an identity
        // mismatch or invalid transition is reported ahead of a field violation.
        if let OrderEventAny::Updated(update) = &event {
            let invalid_fields = match self.order_type {
                OrderType::Market => update.price.is_some() || update.trigger_price.is_some(),
                OrderType::StopMarket
                | OrderType::MarketIfTouched
                | OrderType::TrailingStopMarket => update.price.is_some(),
                OrderType::Limit | OrderType::MarketToLimit => update.trigger_price.is_some(),
                OrderType::StopLimit | OrderType::LimitIfTouched | OrderType::TrailingStopLimit => {
                    false
                }
            };

            if invalid_fields {
                return Err(OrderError::InvalidOrderEvent);
            }
        }

        let source_status = self.status;

        // Save current status as previous_status for ALL transitions except:
        // - Initialized (no prior state exists)
        // - ModifyRejected/CancelRejected (need to preserve the pre Pending state)
        // - When already in Pending* state (avoid overwriting the pre Pending state when receiving multiple pending requests)
        if !matches!(
            event,
            OrderEventAny::Initialized(_)
                | OrderEventAny::ModifyRejected(_)
                | OrderEventAny::CancelRejected(_)
        ) && !matches!(
            self.status,
            OrderStatus::PendingUpdate | OrderStatus::PendingCancel
        ) {
            self.previous_status = Some(self.status);
        }

        self.status = new_status;

        match &event {
            // Rejected by the pre-commit check above; kept for exhaustiveness
            OrderEventAny::Initialized(_) => return Err(OrderError::AlreadyInitialized),
            OrderEventAny::Denied(event) => self.denied(event),
            OrderEventAny::Emulated(event) => self.emulated(event),
            OrderEventAny::Released(event) => self.released(event),
            OrderEventAny::Submitted(event) => self.submitted(event),
            OrderEventAny::Rejected(event) => self.rejected(event),
            OrderEventAny::Accepted(event) => self.accepted(event),
            OrderEventAny::PendingUpdate(event) => self.pending_update(event),
            OrderEventAny::PendingCancel(event) => self.pending_cancel(event),
            OrderEventAny::ModifyRejected(event) => self.modify_rejected(event, rejection_status),
            OrderEventAny::CancelRejected(event) => self.cancel_rejected(event, rejection_status),
            OrderEventAny::Updated(event) => self.updated(event),
            OrderEventAny::Triggered(event) => self.triggered(event),
            OrderEventAny::Canceled(event) => self.canceled(event),
            OrderEventAny::Expired(event) => self.expired(event),
            OrderEventAny::Filled(event) => self.filled(event),
            OrderEventAny::FillVoided(event) => self.fill_voided(event, source_status),
        }

        self.ts_last = event.ts_event();
        self.events.push(event);
        Ok(())
    }

    fn denied(&mut self, event: &OrderDenied) {
        self.ts_closed = Some(event.ts_event);
    }

    fn emulated(&self, _event: &OrderEmulated) {
        // Do nothing else
    }

    fn released(&mut self, _event: &OrderReleased) {
        self.emulation_trigger = None;
    }

    fn submitted(&mut self, event: &OrderSubmitted) {
        self.account_id = Some(event.account_id);
        self.ts_submitted = Some(event.ts_event);
    }

    fn accepted(&mut self, event: &OrderAccepted) {
        self.account_id = Some(event.account_id);
        self.venue_order_id = Some(event.venue_order_id);
        self.venue_order_ids.push(event.venue_order_id);
        self.ts_accepted = Some(event.ts_event);
    }

    fn rejected(&mut self, event: &OrderRejected) {
        self.ts_closed = Some(event.ts_event);
    }

    fn pending_update(&self, _event: &OrderPendingUpdate) {
        // Do nothing else
    }

    fn pending_cancel(&self, _event: &OrderPendingCancel) {
        // Do nothing else
    }

    fn modify_rejected(&mut self, _event: &OrderModifyRejected, previous_status: OrderStatus) {
        self.status = previous_status;
    }

    fn cancel_rejected(&mut self, _event: &OrderCancelRejected, previous_status: OrderStatus) {
        self.status = previous_status;
    }

    fn triggered(&self, _event: &OrderTriggered) {}

    fn canceled(&mut self, event: &OrderCanceled) {
        self.ts_closed = Some(event.ts_event);
    }

    fn expired(&mut self, event: &OrderExpired) {
        self.ts_closed = Some(event.ts_event);
    }

    fn validate_fill_void(&self, event: &OrderFillVoided) -> Result<(), OrderError> {
        let fill = self.events.iter().find_map(|candidate| match candidate {
            OrderEventAny::Filled(fill) if fill.trade_id == event.trade_id => Some(fill),
            _ => None,
        });

        if event.voided_qty.is_zero() {
            return Err(OrderError::OverVoid(event.trade_id));
        }

        let previous = self.latest_fill_void(event.trade_id);
        if let Some(previous) = previous {
            if event.voided_qty < previous.voided_qty {
                return Err(OrderError::StaleFillVoid(event.trade_id));
            }

            if event.voided_qty == previous.voided_qty
                && event.commission_voided == previous.commission_voided
                && event.is_reopened == previous.is_reopened
            {
                return Err(OrderError::DuplicateFillVoid(event.trade_id));
            }
        }

        let Some(fill) = fill else {
            if event.is_reopened {
                return Err(OrderError::InvalidOrderEvent);
            }

            if !self.matches_fill_void_identity(event) {
                return Err(OrderError::InvalidOrderEvent);
            }

            if event.voided_qty > self.quantity
                || event
                    .commission_voided
                    .is_some_and(|commission| !commission.is_zero())
            {
                return Err(OrderError::OverVoid(event.trade_id));
            }
            return Ok(());
        };

        if fill.venue_order_id != event.venue_order_id
            || fill.account_id != event.account_id
            || fill.order_side != event.order_side
            || fill.order_type != event.order_type
            || fill.last_px != event.last_px
            || fill.currency != event.currency
            || fill.liquidity_side != event.liquidity_side
            || fill.position_id != event.position_id
        {
            return Err(OrderError::InvalidOrderEvent);
        }

        if event.voided_qty > fill.last_qty {
            return Err(OrderError::OverVoid(event.trade_id));
        }

        self.validate_fill_void_commission(fill, event, previous)
    }

    fn matches_fill_void_identity(&self, event: &OrderFillVoided) -> bool {
        event.trader_id == self.trader_id
            && event.instrument_id == self.instrument_id
            && event.order_side == self.side
            && event.order_type == self.order_type
            && (self.venue_order_id == Some(event.venue_order_id)
                || self.venue_order_ids.contains(&event.venue_order_id))
            && self.account_id == Some(event.account_id)
    }

    fn validate_fill_void_commission(
        &self,
        fill: &OrderFilled,
        event: &OrderFillVoided,
        previous: Option<&OrderFillVoided>,
    ) -> Result<(), OrderError> {
        match (fill.commission, event.commission_voided) {
            (None, None) => Ok(()),
            (None, Some(commission)) if commission.is_zero() => Ok(()),
            (Some(_), None) if previous.and_then(|prior| prior.commission_voided).is_none() => {
                Ok(())
            }
            (Some(commission), Some(voided))
                if commission.currency == voided.currency
                    && commission.raw.signum() == voided.raw.signum()
                    && voided.raw.abs() <= commission.raw.abs()
                    && previous
                        .and_then(|prior| prior.commission_voided)
                        .is_none_or(|prior| voided.raw.abs() >= prior.raw.abs()) =>
            {
                Ok(())
            }
            _ => Err(OrderError::InvalidFillVoidCommission(event.trade_id)),
        }
    }

    fn latest_fill_void(&self, trade_id: TradeId) -> Option<&OrderFillVoided> {
        self.events
            .iter()
            .rev()
            .find_map(|candidate| match candidate {
                OrderEventAny::FillVoided(event) if event.trade_id == trade_id => Some(event),
                _ => None,
            })
    }

    fn fill_voided(&mut self, event: &OrderFillVoided, source_status: OrderStatus) {
        let has_local_fill = self.events.iter().any(
            |candidate| matches!(candidate, OrderEventAny::Filled(fill) if fill.trade_id == event.trade_id),
        );
        let non_reopened_voided_qty = self.recompute_fill_state(Some(event));
        let unfilled_qty = self.quantity.saturating_sub(self.filled_qty);
        let working_leaves = unfilled_qty.saturating_sub(non_reopened_voided_qty);

        match source_status {
            OrderStatus::Voided => {
                self.status = OrderStatus::Voided;
                self.leaves_qty = Quantity::zero(self.quantity.precision);
            }
            _ if !has_local_fill && !event.is_reopened => {
                self.status = OrderStatus::Voided;
                self.leaves_qty = Quantity::zero(self.quantity.precision);
            }
            OrderStatus::Canceled | OrderStatus::Expired => {
                self.status = source_status;
                self.leaves_qty = unfilled_qty;
            }
            _ if working_leaves.is_zero() => {
                self.status = OrderStatus::Voided;
                self.leaves_qty = working_leaves;
            }
            OrderStatus::PendingUpdate | OrderStatus::PendingCancel | OrderStatus::Triggered => {
                self.status = source_status;
                self.leaves_qty = working_leaves;
            }
            _ => {
                self.status = if self.filled_qty.is_zero() {
                    OrderStatus::Accepted
                } else {
                    OrderStatus::PartiallyFilled
                };
                self.leaves_qty = working_leaves;
            }
        }

        if self.status.is_open() {
            self.ts_closed = None;
        } else if self.status.is_closed() {
            self.ts_closed = self.ts_closed.or(Some(event.ts_event));
        }
    }

    fn recompute_fill_state(&mut self, additional: Option<&OrderFillVoided>) -> Quantity {
        let corrections = self.fill_corrections(additional);

        let mut filled_raw = Quantity::zero(self.quantity.precision).raw;
        let mut voided_raw = Quantity::zero(self.quantity.precision).raw;
        let mut non_reopened_voided_raw = Quantity::zero(self.quantity.precision).raw;
        let mut commissions = IndexMap::<Currency, Money>::new();
        let mut trade_ids = Vec::new();
        let mut last_trade_id = None;
        let mut position_id = None;
        let mut liquidity_side = Some(LiquiditySide::NoLiquiditySide);
        let mut matched_corrections = AHashSet::new();

        for candidate in &self.events {
            let OrderEventAny::Filled(fill) = candidate else {
                continue;
            };
            let correction = corrections.get(&fill.trade_id).copied();
            if correction.is_some() {
                matched_corrections.insert(fill.trade_id);
            }
            let removed = Self::removed_fill_qty(fill, correction);
            let effective = fill.last_qty - removed;
            voided_raw = voided_raw.saturating_add(removed.raw);
            if correction.is_some_and(|event| !event.is_reopened) {
                non_reopened_voided_raw = non_reopened_voided_raw.saturating_add(removed.raw);
            }

            if !effective.is_zero() {
                filled_raw = filled_raw.saturating_add(effective.raw);
                trade_ids.push(fill.trade_id);
                last_trade_id = Some(fill.trade_id);
                position_id = fill.position_id;
                liquidity_side = Some(fill.liquidity_side);
            }

            if let Some(commission) = fill.commission {
                let surviving = correction
                    .and_then(|event| event.commission_voided)
                    .filter(|voided| !voided.is_zero())
                    .map_or(commission, |voided| commission - voided);

                if !surviving.is_zero() {
                    commissions
                        .entry(surviving.currency)
                        .and_modify(|total| *total = *total + surviving)
                        .or_insert(surviving);
                }
            }
        }

        for (trade_id, correction) in corrections {
            if !matched_corrections.contains(&trade_id) {
                voided_raw = voided_raw.saturating_add(correction.voided_qty.raw);
            }
        }

        self.filled_qty = quantity_from_domain_raw(filled_raw, self.quantity.precision);
        self.voided_qty = quantity_from_domain_raw(voided_raw, self.quantity.precision);
        self.overfill_qty = self.filled_qty.saturating_sub(self.quantity);
        self.avg_px = self.avg_px_from_fills(additional, None);
        self.commissions = commissions;
        self.trade_ids = trade_ids;
        self.last_trade_id = last_trade_id;
        self.position_id = position_id;
        self.liquidity_side = liquidity_side;

        quantity_from_domain_raw(non_reopened_voided_raw, self.quantity.precision)
    }

    fn updated(&mut self, event: &OrderUpdated) {
        if matches!(
            self.status,
            OrderStatus::PendingUpdate | OrderStatus::PendingCancel,
        ) && let Some(previous) = self.previous_status
        {
            self.status = previous;
        }

        if event.reconciliation && !self.filled_qty.is_zero() && event.quantity == self.filled_qty {
            self.status = OrderStatus::Filled;
            self.ts_closed = Some(event.ts_event);
        }

        if let Some(venue_order_id) = &event.venue_order_id
            && (self.venue_order_id.is_none()
                || venue_order_id != self.venue_order_id.as_ref().unwrap())
        {
            self.venue_order_id = Some(*venue_order_id);
            self.venue_order_ids.push(*venue_order_id);
        }

        self.is_quote_quantity = event.is_quote_quantity;
    }

    fn filled(&mut self, event: &OrderFilled) {
        let raw = checked_quantity_raw_sum(self.filled_qty.raw, event.last_qty.raw)
            .expect("fill raw bounds pre-checked");
        let new_filled_qty = Quantity::from_raw(raw, self.filled_qty.precision);

        // Calculate overfill if any
        if new_filled_qty > self.quantity {
            let overfill_raw = new_filled_qty.raw - self.quantity.raw;
            self.overfill_qty = quantity_from_domain_raw(
                self.overfill_qty.raw.saturating_add(overfill_raw),
                self.filled_qty.precision,
            );
        }

        let new_leaves_qty = self.leaves_qty.saturating_sub(event.last_qty);

        if new_filled_qty >= self.quantity {
            self.status = OrderStatus::Filled;
            self.ts_closed = Some(event.ts_event);
        } else if new_leaves_qty.is_zero() && !self.voided_qty.is_zero() {
            self.status = OrderStatus::Voided;
            self.ts_closed = Some(event.ts_event);
        } else {
            self.status = OrderStatus::PartiallyFilled;
        }

        self.venue_order_id = Some(event.venue_order_id);
        self.position_id = event.position_id;
        self.trade_ids.push(event.trade_id);
        self.last_trade_id = Some(event.trade_id);
        self.liquidity_side = Some(event.liquidity_side);
        self.filled_qty = new_filled_qty;
        self.leaves_qty = new_leaves_qty;
        self.ts_last = event.ts_event;

        if let Some(commission) = event.commission {
            let commission_currency = commission.currency;
            if let Some(existing_commission) = self.commissions.get_mut(&commission_currency) {
                *existing_commission = *existing_commission + commission;
            } else {
                self.commissions.insert(commission_currency, commission);
            }
        }

        if self.ts_accepted.is_none() {
            // Set ts_accepted to time of first fill if not previously set
            self.ts_accepted = Some(event.ts_event);
        }

        self.avg_px = self.avg_px_from_fills(None, Some(event));

        debug_assert!(
            matches!(
                self.status,
                OrderStatus::PartiallyFilled | OrderStatus::Filled | OrderStatus::Voided
            ),
            "Invariant: status must be PartiallyFilled, Filled, or Voided after fill handler (status={:?})",
            self.status
        );
        debug_assert!(
            self.venue_order_id.is_some()
                && self.last_trade_id.is_some()
                && !self.trade_ids.is_empty(),
            "Invariant: venue_order_id, last_trade_id, and trade_ids must be set after fill"
        );
        debug_assert!(
            self.filled_qty
                .raw
                .saturating_add(self.voided_qty.raw)
                .saturating_add(self.leaves_qty.raw)
                >= self.quantity.raw,
            "Invariant: filled_qty + voided_qty + leaves_qty >= quantity (filled={}, voided={}, leaves={}, quantity={})",
            self.filled_qty,
            self.voided_qty,
            self.leaves_qty,
            self.quantity
        );
    }

    // `Order::apply` appends the event after its handler runs, so a correction or fill still in
    // flight arrives as `additional` / `pending` rather than through `self.events`.
    fn avg_px_from_fills(
        &self,
        additional: Option<&OrderFillVoided>,
        pending: Option<&OrderFilled>,
    ) -> Option<Decimal> {
        let corrections = self.fill_corrections(additional);
        let mut notional = Decimal::ZERO;
        let mut quantity = Decimal::ZERO;

        for candidate in &self.events {
            let OrderEventAny::Filled(fill) = candidate else {
                continue;
            };
            let removed = Self::removed_fill_qty(fill, corrections.get(&fill.trade_id).copied());
            let effective = (fill.last_qty - removed).as_decimal();
            if effective.is_zero() {
                continue;
            }

            notional = notional.saturating_add(effective.saturating_mul(fill.last_px.as_decimal()));
            quantity = quantity.saturating_add(effective);
        }

        if let Some(fill) = pending {
            let last_qty = fill.last_qty.as_decimal();
            notional = notional.saturating_add(last_qty.saturating_mul(fill.last_px.as_decimal()));
            quantity = quantity.saturating_add(last_qty);
        }

        notional.checked_div(quantity)
    }

    fn fill_corrections<'a>(
        &'a self,
        additional: Option<&'a OrderFillVoided>,
    ) -> IndexMap<TradeId, &'a OrderFillVoided> {
        let mut corrections = IndexMap::new();

        for candidate in &self.events {
            if let OrderEventAny::FillVoided(event) = candidate {
                corrections.insert(event.trade_id, event);
            }
        }

        if let Some(event) = additional {
            corrections.insert(event.trade_id, event);
        }

        corrections
    }

    fn removed_fill_qty(fill: &OrderFilled, correction: Option<&OrderFillVoided>) -> Quantity {
        correction.map_or_else(
            || Quantity::zero(fill.last_qty.precision),
            |event| event.voided_qty.min(fill.last_qty),
        )
    }

    pub fn set_slippage(&mut self, price: Price) {
        self.slippage = self.avg_px.and_then(|avg_px| {
            let current_price = price.as_decimal();
            match self.side {
                OrderSide::Buy if avg_px > current_price => avg_px.checked_sub(current_price),
                OrderSide::Sell if avg_px < current_price => current_price.checked_sub(avg_px),
                _ => None,
            }
        });
    }

    /// Returns the opposite order side.
    #[must_use]
    pub fn opposite_side(side: OrderSide) -> OrderSide {
        match side {
            OrderSide::Buy => OrderSide::Sell,
            OrderSide::Sell => OrderSide::Buy,
            OrderSide::NoOrderSide => OrderSide::NoOrderSide,
        }
    }

    /// Returns the order side needed to close a position.
    #[must_use]
    pub fn closing_side(side: PositionSide) -> OrderSide {
        match side {
            PositionSide::Long => OrderSide::Sell,
            PositionSide::Short => OrderSide::Buy,
            PositionSide::Flat => OrderSide::NoOrderSide,
            PositionSide::NoPositionSide => OrderSide::NoOrderSide,
        }
    }

    /// # Panics
    ///
    /// Panics if the order side is neither `Buy` nor `Sell`.
    #[must_use]
    pub fn signed_decimal_qty(&self) -> Decimal {
        match self.side {
            OrderSide::Buy => self.quantity.as_decimal(),
            OrderSide::Sell => -self.quantity.as_decimal(),
            OrderSide::NoOrderSide => panic!("Invalid order side"),
        }
    }

    #[must_use]
    pub fn would_reduce_only(&self, side: PositionSide, position_qty: Quantity) -> bool {
        if side == PositionSide::Flat {
            return false;
        }

        match (self.side, side) {
            (OrderSide::Buy, PositionSide::Long) => false,
            (OrderSide::Buy, PositionSide::Short) => self.leaves_qty <= position_qty,
            (OrderSide::Sell, PositionSide::Short) => false,
            (OrderSide::Sell, PositionSide::Long) => self.leaves_qty <= position_qty,
            _ => true,
        }
    }

    #[must_use]
    pub fn commission(&self, currency: &Currency) -> Option<Money> {
        self.commissions.get(currency).copied()
    }

    #[must_use]
    pub fn commissions(&self) -> IndexMap<Currency, Money> {
        self.commissions.clone()
    }

    #[must_use]
    pub fn commissions_vec(&self) -> Vec<Money> {
        self.commissions.values().copied().collect()
    }

    #[must_use]
    pub fn init_event(&self) -> Option<OrderEventAny> {
        self.events.first().cloned()
    }
}

#[cfg(test)]
mod tests {
    use std::str::FromStr;

    use rstest::rstest;
    use rust_decimal_macros::dec;

    use super::*;
    use crate::{
        enums::{LiquiditySide, OrderSide, OrderStatus, PositionSide, TriggerType},
        events::order::spec::{
            OrderAcceptedSpec, OrderCancelRejectedSpec, OrderCanceledSpec, OrderDeniedSpec,
            OrderExpiredSpec, OrderFillVoidedSpec, OrderFilledSpec, OrderInitializedSpec,
            OrderModifyRejectedSpec, OrderPendingCancelSpec, OrderPendingUpdateSpec,
            OrderRejectedSpec, OrderSubmittedSpec, OrderTriggeredSpec, OrderUpdatedSpec,
        },
        identifiers::InstrumentId,
        instruments::{CurrencyPair, Instrument, InstrumentAny, stubs::audusd_sim},
        orders::{MarketOrder, builder::OrderTestBuilder, stubs::TestOrderStubs},
        types::{
            Price, Quantity,
            quantity::{QUANTITY_RAW_MAX, QuantityRaw},
        },
    };

    // TODO: WIP
    // fn test_display_market_order() {
    //     let order = MarketOrder::default();
    //     assert_eq!(order.events().len(), 1);
    //     assert_eq!(
    //         stringify!(order.events().get(0)),
    //         stringify!(OrderInitialized)
    //     );
    // }

    #[rstest]
    #[case(OrderSide::Buy, OrderSide::Sell)]
    #[case(OrderSide::Sell, OrderSide::Buy)]
    #[case(OrderSide::NoOrderSide, OrderSide::NoOrderSide)]
    fn test_order_opposite_side(#[case] order_side: OrderSide, #[case] expected_side: OrderSide) {
        let result = OrderCore::opposite_side(order_side);
        assert_eq!(result, expected_side);
    }

    #[rstest]
    #[case(PositionSide::Long, OrderSide::Sell)]
    #[case(PositionSide::Short, OrderSide::Buy)]
    #[case(PositionSide::NoPositionSide, OrderSide::NoOrderSide)]
    fn test_closing_side(#[case] position_side: PositionSide, #[case] expected_side: OrderSide) {
        let result = OrderCore::closing_side(position_side);
        assert_eq!(result, expected_side);
    }

    #[rstest]
    #[case(OrderSide::Buy, dec!(10_000))]
    #[case(OrderSide::Sell, dec!(-10_000))]
    fn test_signed_decimal_qty(#[case] order_side: OrderSide, #[case] expected: Decimal) {
        let order: MarketOrder = OrderInitializedSpec::builder()
            .order_side(order_side)
            .quantity(Quantity::from(10_000))
            .build()
            .try_into()
            .unwrap();

        let result = order.signed_decimal_qty();
        assert_eq!(result, expected);
    }

    #[rustfmt::skip]
    #[rstest]
    #[case(OrderSide::Buy, Quantity::from(100), PositionSide::Long, Quantity::from(50), false)]
    #[case(OrderSide::Buy, Quantity::from(50), PositionSide::Short, Quantity::from(50), true)]
    #[case(OrderSide::Buy, Quantity::from(50), PositionSide::Short, Quantity::from(100), true)]
    #[case(OrderSide::Buy, Quantity::from(50), PositionSide::Flat, Quantity::from(0), false)]
    #[case(OrderSide::Sell, Quantity::from(50), PositionSide::Flat, Quantity::from(0), false)]
    #[case(OrderSide::Sell, Quantity::from(50), PositionSide::Long, Quantity::from(50), true)]
    #[case(OrderSide::Sell, Quantity::from(50), PositionSide::Long, Quantity::from(100), true)]
    #[case(OrderSide::Sell, Quantity::from(100), PositionSide::Short, Quantity::from(50), false)]
    fn test_would_reduce_only(
        #[case] order_side: OrderSide,
        #[case] order_qty: Quantity,
        #[case] position_side: PositionSide,
        #[case] position_qty: Quantity,
        #[case] expected: bool,
    ) {
        let order: MarketOrder = OrderInitializedSpec::builder()
            .order_side(order_side)
            .quantity(order_qty)
            .build()
            .try_into()
            .unwrap();

        assert_eq!(
            order.would_reduce_only(position_side, position_qty),
            expected
        );
    }

    #[rstest]
    fn test_order_state_transition_denied() {
        let mut order: MarketOrder = OrderInitializedSpec::builder().build().try_into().unwrap();
        let denied = OrderDeniedSpec::builder().build();
        let event = OrderEventAny::Denied(denied);

        order.apply(event.clone()).unwrap();

        assert_eq!(order.status, OrderStatus::Denied);
        assert!(order.is_closed());
        assert!(!order.is_open());
        assert_eq!(order.event_count(), 2);
        assert_eq!(order.last_event(), &event);
    }

    #[rstest]
    fn test_order_life_cycle_to_filled() {
        let init = OrderInitializedSpec::builder().build();
        let submitted = OrderSubmittedSpec::builder().build();
        let accepted = OrderAcceptedSpec::builder().build();
        let filled = OrderFilledSpec::builder().build();

        let mut order: MarketOrder = init.clone().try_into().unwrap();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        order.apply(OrderEventAny::Filled(filled)).unwrap();

        assert_eq!(order.client_order_id, init.client_order_id);
        assert_eq!(order.status(), OrderStatus::Filled);
        assert_eq!(order.filled_qty(), Quantity::from(100_000));
        assert_eq!(order.leaves_qty(), Quantity::from(0));
        assert_eq!(order.avg_px(), Some(dec!(1.0)));
        assert!(!order.is_open());
        assert!(order.is_closed());
        assert_eq!(order.commission(&Currency::USD()), None);
        assert_eq!(order.commissions(), &IndexMap::new());
    }

    #[rstest]
    fn test_order_life_cycle_fills_with_negative_prices() {
        // Options and spreads can legitimately trade at negative prices. The
        // weighted average-price update must not panic when `last_px` or the
        // prior `avg_px` is below zero.
        let init = OrderInitializedSpec::builder()
            .quantity(Quantity::from(100_000))
            .build();
        let submitted = OrderSubmittedSpec::builder().build();
        let accepted = OrderAcceptedSpec::builder().build();
        let fill1 = OrderFilledSpec::builder()
            .last_qty(Quantity::from(50_000))
            .last_px(Price::from("-5.00000"))
            .trade_id(TradeId::from("TRADE-1"))
            .build();
        let fill2 = OrderFilledSpec::builder()
            .last_qty(Quantity::from(50_000))
            .last_px(Price::from("-7.00000"))
            .trade_id(TradeId::from("TRADE-2"))
            .build();

        let mut order: MarketOrder = init.try_into().unwrap();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        order.apply(OrderEventAny::Filled(fill1)).unwrap();
        order.apply(OrderEventAny::Filled(fill2)).unwrap();

        assert_eq!(order.status(), OrderStatus::Filled);
        assert_eq!(order.filled_qty(), Quantity::from(100_000));
        assert_eq!(order.leaves_qty(), Quantity::from(0));
        // Weighted avg: (50_000 * -5.0 + 50_000 * -7.0) / 100_000 = -6.0
        assert_eq!(order.avg_px(), Some(dec!(-6.0)));
    }

    fn fill(trade_id: &str, last_qty: &str, last_px: &str) -> (TradeId, Quantity, Price) {
        (
            TradeId::from(trade_id),
            Quantity::from(last_qty),
            Price::from(last_px),
        )
    }

    fn market_order_with_fills(
        order_side: OrderSide,
        quantity: Quantity,
        fills: &[(TradeId, Quantity, Price)],
    ) -> MarketOrder {
        let mut order: MarketOrder = OrderInitializedSpec::builder()
            .order_side(order_side)
            .quantity(quantity)
            .build()
            .try_into()
            .unwrap();
        order
            .apply(OrderEventAny::Accepted(
                OrderAcceptedSpec::builder().build(),
            ))
            .unwrap();

        for (trade_id, last_qty, last_px) in fills {
            order
                .apply(OrderEventAny::Filled(
                    OrderFilledSpec::builder()
                        .order_side(order_side)
                        .trade_id(*trade_id)
                        .last_qty(*last_qty)
                        .last_px(*last_px)
                        .build(),
                ))
                .unwrap();
        }

        order
    }

    #[rstest]
    #[case(OrderSide::Buy)]
    #[case(OrderSide::Sell)]
    fn test_avg_px_weighted_average_is_exact(#[case] order_side: OrderSide) {
        // (1 * 0.07) + (2 * 0.13) + (3 * 0.29) = 1.20 over 6 filled, so the exact average is
        // 0.20. Accumulating the notional in f64 returns 0.19999999999999998 instead.
        let order = market_order_with_fills(
            order_side,
            Quantity::from(6),
            &[
                fill("TRADE-1", "1", "0.07"),
                fill("TRADE-2", "2", "0.13"),
                fill("TRADE-3", "3", "0.29"),
            ],
        );

        assert_eq!(order.status(), OrderStatus::Filled);
        assert_eq!(order.filled_qty(), Quantity::from(6));
        assert_eq!(order.leaves_qty(), Quantity::from(0));
        assert_eq!(order.voided_qty(), Quantity::from(0));
        assert_eq!(order.avg_px(), Some(dec!(0.2)));
    }

    #[rstest]
    fn test_avg_px_keeps_a_quotient_no_f64_can_hold() {
        // (1 * 1.00) + (2 * 2.00) = 5.00 over 3 filled. The exact quotient repeats, so `Decimal`
        // carries it to its full 28-place scale where the widest `f64` holds 1.6666666666666667.
        let order = market_order_with_fills(
            OrderSide::Buy,
            Quantity::from(3),
            &[fill("TRADE-1", "1", "1.00"), fill("TRADE-2", "2", "2.00")],
        );

        assert_eq!(order.status(), OrderStatus::Filled);
        assert_eq!(order.filled_qty(), Quantity::from(3));
        assert_eq!(order.avg_px(), Some(dec!(1.6666666666666666666666666667)));
        assert_ne!(
            order.avg_px(),
            Some(Decimal::from_f64_retain(5.0_f64 / 3.0).unwrap())
        );
    }

    #[rstest]
    #[case(OrderSide::Buy, "1.07", "1.00", Some(dec!(0.07)))]
    #[case(OrderSide::Sell, "0.93", "1.00", Some(dec!(0.07)))]
    #[case(OrderSide::Buy, "0.93", "1.00", None)]
    #[case(OrderSide::Sell, "1.07", "1.00", None)]
    fn test_set_slippage_by_side(
        #[case] order_side: OrderSide,
        #[case] fill_px: &str,
        #[case] reference_px: &str,
        #[case] expected: Option<Decimal>,
    ) {
        // Slippage only accrues against the order: a buy filled above the reference price and a
        // sell filled below it. The opposite cases are price improvement and stay `None`.
        let mut order =
            market_order_with_fills(order_side, Quantity::from(1), &[fill("T-1", "1", fill_px)]);

        order.set_slippage(Price::from(reference_px));

        assert_eq!(order.avg_px(), Some(Decimal::from_str(fill_px).unwrap()));
        assert_eq!(order.slippage(), expected);
    }

    #[rstest]
    fn test_avg_px_invariant_to_fill_arrival_order() {
        // (50_000 * 1.00001) + (30_000 * 1.00002) + (20_000 * 1.00003) = 100_001.7 over
        // 100_000 filled, so the exact average is 1.000017 whichever order the fills arrive
        // in. The f64 fold returns 1.0000170000000002 for the ascending sequence only.
        let mut fills = [
            fill("TRADE-1", "50000", "1.00001"),
            fill("TRADE-2", "30000", "1.00002"),
            fill("TRADE-3", "20000", "1.00003"),
        ];

        let ascending = market_order_with_fills(OrderSide::Buy, Quantity::from(100_000), &fills);
        fills.reverse();
        let descending = market_order_with_fills(OrderSide::Buy, Quantity::from(100_000), &fills);

        assert_eq!(ascending.avg_px(), Some(dec!(1.000_017)));
        assert_eq!(descending.avg_px(), ascending.avg_px());
        assert_eq!(descending.filled_qty(), ascending.filled_qty());
    }

    #[rstest]
    fn test_avg_px_after_fill_void_matches_order_without_voided_fill() {
        let surviving = [fill("TRADE-1", "1", "0.05"), fill("TRADE-2", "3", "0.15")];
        let voided = fill("TRADE-VOIDED", "2", "0.13");

        let expected = market_order_with_fills(OrderSide::Buy, Quantity::from(6), &surviving);
        let mut corrected = market_order_with_fills(
            OrderSide::Buy,
            Quantity::from(6),
            &[surviving[0], surviving[1], voided],
        );
        corrected
            .apply(OrderEventAny::FillVoided(
                OrderFillVoidedSpec::builder()
                    .trade_id(voided.0)
                    .voided_qty(voided.1)
                    .last_px(voided.2)
                    .build(),
            ))
            .unwrap();

        let replayed =
            OrderAny::from_events(corrected.events().into_iter().cloned().collect()).unwrap();

        // (1 * 0.05) + (3 * 0.15) = 0.50 over 4 filled: 0.125 exactly, whether the fold runs
        // incrementally over the fills, as the rebuild after the void drops the third fill, or
        // over the whole event stream on replay. The f64 rebuild returns 0.12499999999999999.
        assert_eq!(expected.avg_px(), Some(dec!(0.125)));
        assert_eq!(corrected.avg_px(), expected.avg_px());
        assert_eq!(replayed.avg_px(), expected.avg_px());
        assert_eq!(corrected.status(), OrderStatus::Voided);
        assert_eq!(corrected.filled_qty(), Quantity::from(4));
        assert_eq!(corrected.voided_qty(), Quantity::from(2));
        assert_eq!(corrected.leaves_qty(), Quantity::from(0));
        assert_eq!(replayed.filled_qty(), corrected.filled_qty());
        assert_eq!(replayed.voided_qty(), corrected.voided_qty());
    }

    #[rstest]
    fn test_avg_px_recomputed_from_partially_voided_fill() {
        let mut order = market_order_with_fills(
            OrderSide::Buy,
            Quantity::from(6),
            &[fill("TRADE-1", "4", "1.00"), fill("TRADE-2", "2", "1.14")],
        );
        order
            .apply(OrderEventAny::FillVoided(
                OrderFillVoidedSpec::builder()
                    .trade_id(TradeId::from("TRADE-1"))
                    .voided_qty(Quantity::from(2))
                    .last_px(Price::from("1.00"))
                    .build(),
            ))
            .unwrap();

        // Surviving (2 * 1.00) + (2 * 1.14) = 4.28 over 4 filled: 1.07 exactly, where the f64
        // rebuild returns 1.0699999999999998.
        assert_eq!(order.status(), OrderStatus::Voided);
        assert_eq!(order.filled_qty(), Quantity::from(4));
        assert_eq!(order.voided_qty(), Quantity::from(2));
        assert_eq!(order.leaves_qty(), Quantity::from(0));
        assert_eq!(order.avg_px(), Some(dec!(1.07)));
    }

    #[rstest]
    fn test_avg_px_over_reopened_fill_void_and_replacement_fill() {
        let mut order = market_order_with_fills(
            OrderSide::Buy,
            Quantity::from(6),
            &[fill("TRADE-1", "4", "1.00")],
        );
        order
            .apply(OrderEventAny::FillVoided(
                OrderFillVoidedSpec::builder()
                    .trade_id(TradeId::from("TRADE-1"))
                    .voided_qty(Quantity::from(2))
                    .last_px(Price::from("1.00"))
                    .is_reopened(true)
                    .build(),
            ))
            .unwrap();
        order
            .apply(OrderEventAny::Filled(
                OrderFilledSpec::builder()
                    .trade_id(TradeId::from("TRADE-2"))
                    .last_qty(Quantity::from(2))
                    .last_px(Price::from("1.14"))
                    .build(),
            ))
            .unwrap();
        order.set_slippage(Price::from("1.00"));

        // The reopened void leaves 2 of the first fill, so the replacement fill folds against
        // the surviving quantity: (2 * 1.00) + (2 * 1.14) = 4.28 over 4 filled, or 1.07
        // exactly. The f64 update returns 1.0699999999999998, which slippage then inherits.
        assert_eq!(order.status(), OrderStatus::PartiallyFilled);
        assert_eq!(order.filled_qty(), Quantity::from(4));
        assert_eq!(order.voided_qty(), Quantity::from(2));
        assert_eq!(order.leaves_qty(), Quantity::from(2));
        assert_eq!(order.avg_px(), Some(dec!(1.07)));
        assert_eq!(order.slippage(), Some(dec!(0.07)));
    }

    #[rstest]
    fn test_avg_px_cleared_when_every_fill_is_voided() {
        let mut order = market_order_with_fills(
            OrderSide::Buy,
            Quantity::from(6),
            &[fill("TRADE-1", "4", "1.50")],
        );
        order
            .apply(OrderEventAny::FillVoided(
                OrderFillVoidedSpec::builder()
                    .trade_id(TradeId::from("TRADE-1"))
                    .voided_qty(Quantity::from(4))
                    .last_px(Price::from("1.50"))
                    .build(),
            ))
            .unwrap();

        assert_eq!(order.status(), OrderStatus::Accepted);
        assert_eq!(order.filled_qty(), Quantity::from(0));
        assert_eq!(order.voided_qty(), Quantity::from(4));
        assert_eq!(order.leaves_qty(), Quantity::from(2));
        assert_eq!(order.avg_px(), None);
    }

    #[cfg(feature = "high-precision")]
    #[rstest]
    fn test_avg_px_exact_over_high_precision_quantities() {
        // Same weighting as `test_avg_px_invariant_to_fill_arrival_order`, at a quantity
        // precision only the wider raw backing can hold.
        let order = market_order_with_fills(
            OrderSide::Buy,
            Quantity::from("0.000000000010"),
            &[
                fill("TRADE-1", "0.000000000005", "1.00001"),
                fill("TRADE-2", "0.000000000003", "1.00002"),
                fill("TRADE-3", "0.000000000002", "1.00003"),
            ],
        );

        assert_eq!(order.status(), OrderStatus::Filled);
        assert_eq!(order.filled_qty(), Quantity::from("0.000000000010"));
        assert_eq!(order.avg_px(), Some(dec!(1.000_017)));
    }

    #[cfg(feature = "high-precision")]
    #[rstest]
    fn test_avg_px_exact_at_the_widest_representable_fill_scale() {
        // Pins the exactness bound: a 16-decimal quantity against a 12-decimal price needs the
        // 28 fractional digits Decimal carries, so no product rounds.
        let order = market_order_with_fills(
            OrderSide::Buy,
            Quantity::from("0.0000000000000008"),
            &[
                fill("TRADE-1", "0.0000000000000002", "0.000000000001"),
                fill("TRADE-2", "0.0000000000000006", "0.000000000003"),
            ],
        );

        // (2e-16 * 1e-12) + (6e-16 * 3e-12) = 2e-27 over 8e-16 filled: 2.5e-12 exactly.
        assert_eq!(order.status(), OrderStatus::Filled);
        assert_eq!(order.filled_qty(), Quantity::from("0.0000000000000008"));
        assert_eq!(order.avg_px(), Some(dec!(2.5e-12)));
    }

    #[rstest]
    fn test_order_life_cycle_accumulates_fill_commissions() {
        let init = OrderInitializedSpec::builder()
            .quantity(Quantity::from(100_000))
            .build();
        let submitted = OrderSubmittedSpec::builder().build();
        let accepted = OrderAcceptedSpec::builder().build();
        let fill1 = OrderFilledSpec::builder()
            .last_qty(Quantity::from(50_000))
            .trade_id(TradeId::from("TRADE-1"))
            .commission(Money::from("1.25 USD"))
            .build();
        let fill2 = OrderFilledSpec::builder()
            .last_qty(Quantity::from(50_000))
            .trade_id(TradeId::from("TRADE-2"))
            .commission(Money::from("1.35 USD"))
            .build();

        let mut order: MarketOrder = init.try_into().unwrap();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        order.apply(OrderEventAny::Filled(fill1)).unwrap();
        order.apply(OrderEventAny::Filled(fill2)).unwrap();

        assert_eq!(order.status(), OrderStatus::Filled);
        assert_eq!(
            order.commission(&Currency::USD()),
            Some(Money::from("2.60 USD"))
        );
        assert_eq!(order.commissions_vec(), vec![Money::from("2.60 USD")]);
    }

    #[rstest]
    fn test_fill_void_reopens_only_when_explicitly_marked() {
        let init = OrderInitializedSpec::builder()
            .quantity(Quantity::from(100_000))
            .build();
        let filled = OrderFilledSpec::builder()
            .trade_id(TradeId::from("TRADE-VOID"))
            .last_qty(Quantity::from(100_000))
            .commission(Money::from("1.00 USD"))
            .build();
        let fill_voided = OrderFillVoidedSpec::builder()
            .trade_id(filled.trade_id)
            .voided_qty(Quantity::from(40_000))
            .commission_voided(Money::from("0.40 USD"))
            .build();
        let later_fill = OrderFilledSpec::builder()
            .trade_id(TradeId::from("TRADE-AFTER-REOPEN"))
            .last_qty(Quantity::from(40_000))
            .build();
        let mut order: MarketOrder = init.try_into().unwrap();
        order
            .apply(OrderEventAny::Accepted(
                OrderAcceptedSpec::builder().build(),
            ))
            .unwrap();
        order.apply(OrderEventAny::Filled(filled)).unwrap();

        let mut terminal = order.clone();
        terminal
            .apply(OrderEventAny::FillVoided(fill_voided.clone()))
            .unwrap();
        let fill_while_terminal = terminal.apply(OrderEventAny::Filled(later_fill.clone()));

        order
            .apply(OrderEventAny::FillVoided(OrderFillVoided {
                is_reopened: true,
                ..fill_voided
            }))
            .unwrap();
        let status_after_correction = order.status();
        order.apply(OrderEventAny::Filled(later_fill)).unwrap();

        assert!(matches!(
            fill_while_terminal,
            Err(OrderError::InvalidStateTransition)
        ));
        assert_eq!(terminal.status(), OrderStatus::Voided);
        assert_eq!(status_after_correction, OrderStatus::PartiallyFilled);
        assert_eq!(order.status(), OrderStatus::Filled);
        assert_eq!(order.filled_qty(), Quantity::from(100_000));
        assert_eq!(order.voided_qty(), Quantity::from(40_000));
        assert_eq!(order.leaves_qty(), Quantity::from(0));
        assert_eq!(
            order.commission(&Currency::USD()),
            Some(Money::from("0.60 USD"))
        );
    }

    #[rstest]
    fn test_fill_void_preserves_existing_working_remainder() {
        let init = OrderInitializedSpec::builder()
            .quantity(Quantity::from(100_000))
            .build();
        let filled = OrderFilledSpec::builder()
            .trade_id(TradeId::from("TRADE-VOID"))
            .last_qty(Quantity::from(40_000))
            .build();
        let later_fill = OrderFilledSpec::builder()
            .trade_id(TradeId::from("TRADE-REMAINDER"))
            .last_qty(Quantity::from(60_000))
            .build();
        let mut order: MarketOrder = init.try_into().unwrap();
        order
            .apply(OrderEventAny::Accepted(
                OrderAcceptedSpec::builder().build(),
            ))
            .unwrap();
        order.apply(OrderEventAny::Filled(filled.clone())).unwrap();

        order
            .apply(OrderEventAny::FillVoided(
                OrderFillVoidedSpec::builder()
                    .trade_id(filled.trade_id)
                    .voided_qty(filled.last_qty)
                    .build(),
            ))
            .unwrap();

        assert_eq!(order.status(), OrderStatus::Accepted);
        assert_eq!(order.filled_qty(), Quantity::from(0));
        assert_eq!(order.voided_qty(), Quantity::from(40_000));
        assert_eq!(order.leaves_qty(), Quantity::from(60_000));
        assert!(order.is_open());

        order.apply(OrderEventAny::Filled(later_fill)).unwrap();

        assert_eq!(order.status(), OrderStatus::Voided);
        assert_eq!(order.filled_qty(), Quantity::from(60_000));
        assert_eq!(order.voided_qty(), Quantity::from(40_000));
        assert_eq!(order.leaves_qty(), Quantity::from(0));
        assert!(order.is_closed());
    }

    #[rstest]
    fn test_reopened_fill_void_requires_existing_fill() {
        let trade_id = TradeId::from("TRADE-OUT-OF-ORDER");
        let init = OrderInitializedSpec::builder()
            .quantity(Quantity::from(100_000))
            .build();
        let early_void = OrderFillVoidedSpec::builder()
            .trade_id(trade_id)
            .voided_qty(Quantity::from(10_000))
            .is_reopened(true)
            .build();
        let late_fill = OrderFilledSpec::builder()
            .trade_id(trade_id)
            .last_qty(Quantity::from(40_000))
            .build();
        let mut order: MarketOrder = init.try_into().unwrap();
        order
            .apply(OrderEventAny::Accepted(
                OrderAcceptedSpec::builder().build(),
            ))
            .unwrap();

        let result = order.apply(OrderEventAny::FillVoided(early_void));
        order.apply(OrderEventAny::Filled(late_fill)).unwrap();

        assert!(matches!(result, Err(OrderError::InvalidOrderEvent)));
        assert_eq!(order.status(), OrderStatus::PartiallyFilled);
        assert_eq!(order.filled_qty(), Quantity::from(40_000));
        assert_eq!(order.voided_qty(), Quantity::from(0));
        assert_eq!(order.leaves_qty(), Quantity::from(60_000));
    }

    #[rstest]
    #[case(OrderStatus::Accepted)]
    #[case(OrderStatus::Canceled)]
    #[case(OrderStatus::Expired)]
    fn test_terminal_fill_void_rejects_later_order_events(#[case] status_before_void: OrderStatus) {
        let trade_id = TradeId::from("TRADE-TERMINAL-VOID");
        let init = OrderInitializedSpec::builder()
            .quantity(Quantity::from(100_000))
            .build();
        let terminal_void = OrderFillVoidedSpec::builder()
            .trade_id(trade_id)
            .voided_qty(Quantity::from(40_000))
            .commission_voided(Money::from("0 USD"))
            .build();
        let late_fill = OrderFilledSpec::builder()
            .trade_id(trade_id)
            .last_qty(Quantity::from(40_000))
            .build();
        let mut order: MarketOrder = init.try_into().unwrap();
        order
            .apply(OrderEventAny::Accepted(
                OrderAcceptedSpec::builder().build(),
            ))
            .unwrap();

        match status_before_void {
            OrderStatus::Accepted => {}
            OrderStatus::Canceled => order
                .apply(OrderEventAny::Canceled(
                    OrderCanceledSpec::builder().build(),
                ))
                .unwrap(),
            OrderStatus::Expired => order
                .apply(OrderEventAny::Expired(OrderExpiredSpec::builder().build()))
                .unwrap(),
            _ => unreachable!(),
        }

        order
            .apply(OrderEventAny::FillVoided(terminal_void))
            .unwrap();
        let update_result = order.apply(OrderEventAny::Updated(
            OrderUpdatedSpec::builder()
                .quantity(Quantity::from(120_000))
                .build(),
        ));
        let cancel_result = order.apply(OrderEventAny::Canceled(
            OrderCanceledSpec::builder().build(),
        ));
        let fill_result = order.apply(OrderEventAny::Filled(late_fill));

        assert!(matches!(
            update_result,
            Err(OrderError::InvalidStateTransition)
        ));
        assert!(matches!(
            cancel_result,
            Err(OrderError::InvalidStateTransition)
        ));
        assert!(matches!(
            fill_result,
            Err(OrderError::InvalidStateTransition)
        ));
        assert_eq!(order.status(), OrderStatus::Voided);
        assert_eq!(order.filled_qty(), Quantity::from(0));
        assert_eq!(order.voided_qty(), Quantity::from(40_000));
        assert_eq!(order.leaves_qty(), Quantity::from(0));
    }

    #[rstest]
    #[case(Quantity::from(100_001), None)]
    #[case(Quantity::from(100_000), Some(Money::from("1 USD")))]
    fn test_terminal_fill_void_rejects_invalid_economic_values(
        #[case] voided_qty: Quantity,
        #[case] commission_voided: Option<Money>,
    ) {
        let trade_id = TradeId::from("TRADE-TERMINAL-VOID");
        let init = OrderInitializedSpec::builder()
            .quantity(Quantity::from(100_000))
            .build();
        let mut order: MarketOrder = init.try_into().unwrap();
        order
            .apply(OrderEventAny::Accepted(
                OrderAcceptedSpec::builder().build(),
            ))
            .unwrap();
        let mut invalid = OrderFillVoidedSpec::builder()
            .trade_id(trade_id)
            .voided_qty(voided_qty)
            .build();
        invalid.commission_voided = commission_voided;

        let result = order.apply(OrderEventAny::FillVoided(invalid));

        assert!(matches!(
            result,
            Err(OrderError::OverVoid(error_trade_id)) if error_trade_id == trade_id
        ));
        assert_eq!(order.status(), OrderStatus::Accepted);
        assert_eq!(order.voided_qty(), Quantity::from(0));
    }

    #[rstest]
    fn test_terminal_fill_void_accepts_current_venue_order_id_after_fill_before_accept() {
        let init = OrderInitializedSpec::builder()
            .quantity(Quantity::from(100_000))
            .build();
        let submitted = OrderSubmittedSpec::builder().build();
        let filled = OrderFilledSpec::builder()
            .account_id(submitted.account_id)
            .trade_id(TradeId::from("TRADE-APPLIED"))
            .last_qty(Quantity::from(40_000))
            .build();
        let terminal_void = OrderFillVoidedSpec::builder()
            .venue_order_id(filled.venue_order_id)
            .account_id(filled.account_id)
            .trade_id(TradeId::from("TRADE-TERMINAL-VOID"))
            .voided_qty(Quantity::from(10_000))
            .build();
        let mut order: MarketOrder = init.try_into().unwrap();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Filled(filled)).unwrap();

        order
            .apply(OrderEventAny::FillVoided(terminal_void))
            .unwrap();

        assert_eq!(order.status(), OrderStatus::Voided);
        assert_eq!(order.filled_qty(), Quantity::from(40_000));
        assert_eq!(order.voided_qty(), Quantity::from(10_000));
        assert_eq!(order.leaves_qty(), Quantity::from(0));
    }

    #[rstest]
    fn test_terminal_fill_void_requires_matching_order_identity() {
        let init = OrderInitializedSpec::builder()
            .quantity(Quantity::from(100_000))
            .build();
        let mut order: MarketOrder = init.try_into().unwrap();
        order
            .apply(OrderEventAny::Accepted(
                OrderAcceptedSpec::builder().build(),
            ))
            .unwrap();
        let mismatched = OrderFillVoidedSpec::builder()
            .instrument_id(InstrumentId::from("OTHER.SIM"))
            .trade_id(TradeId::from("TRADE-TERMINAL-VOID"))
            .voided_qty(Quantity::from(100_000))
            .build();

        let result = order.apply(OrderEventAny::FillVoided(mismatched));

        assert!(matches!(result, Err(OrderError::InvalidOrderEvent)));
        assert_eq!(order.status(), OrderStatus::Accepted);
        assert_eq!(order.voided_qty(), Quantity::from(0));
    }

    #[rstest]
    #[case(OrderStatus::Canceled)]
    #[case(OrderStatus::Expired)]
    fn test_fill_void_does_not_reopen_canceled_or_expired_order(
        #[case] terminal_status: OrderStatus,
    ) {
        let init = OrderInitializedSpec::builder()
            .quantity(Quantity::from(100_000))
            .build();
        let filled = OrderFilledSpec::builder()
            .trade_id(TradeId::from("TRADE-TERMINAL-VOID"))
            .last_qty(Quantity::from(60_000))
            .build();
        let mut order: MarketOrder = init.try_into().unwrap();
        order
            .apply(OrderEventAny::Accepted(
                OrderAcceptedSpec::builder().build(),
            ))
            .unwrap();
        order.apply(OrderEventAny::Filled(filled.clone())).unwrap();
        match terminal_status {
            OrderStatus::Canceled => order
                .apply(OrderEventAny::Canceled(
                    OrderCanceledSpec::builder().build(),
                ))
                .unwrap(),
            OrderStatus::Expired => order
                .apply(OrderEventAny::Expired(OrderExpiredSpec::builder().build()))
                .unwrap(),
            _ => unreachable!(),
        }
        let voided = OrderFillVoidedSpec::builder()
            .trade_id(filled.trade_id)
            .voided_qty(Quantity::from(20_000))
            .is_reopened(true)
            .build();

        order.apply(OrderEventAny::FillVoided(voided)).unwrap();

        assert_eq!(order.status(), terminal_status);
        assert_eq!(order.filled_qty(), Quantity::from(40_000));
        assert_eq!(order.voided_qty(), Quantity::from(20_000));
        assert!(order.is_closed());
        assert!(order.ts_closed().is_some());
    }

    #[rstest]
    fn test_fill_void_rejects_duplicate_stale_and_over_void() {
        let init = OrderInitializedSpec::builder()
            .quantity(Quantity::from(100_000))
            .build();
        let filled = OrderFilledSpec::builder()
            .trade_id(TradeId::from("TRADE-VOID"))
            .last_qty(Quantity::from(100_000))
            .build();
        let mut order: MarketOrder = init.try_into().unwrap();
        order
            .apply(OrderEventAny::Accepted(
                OrderAcceptedSpec::builder().build(),
            ))
            .unwrap();
        order.apply(OrderEventAny::Filled(filled)).unwrap();
        order
            .apply(OrderEventAny::FillVoided(
                OrderFillVoidedSpec::builder()
                    .trade_id(TradeId::from("TRADE-VOID"))
                    .voided_qty(Quantity::from(40_000))
                    .build(),
            ))
            .unwrap();

        let duplicate = order.apply(OrderEventAny::FillVoided(
            OrderFillVoidedSpec::builder()
                .trade_id(TradeId::from("TRADE-VOID"))
                .voided_qty(Quantity::from(40_000))
                .build(),
        ));
        let stale = order.apply(OrderEventAny::FillVoided(
            OrderFillVoidedSpec::builder()
                .trade_id(TradeId::from("TRADE-VOID"))
                .voided_qty(Quantity::from(30_000))
                .build(),
        ));
        let over_void = order.apply(OrderEventAny::FillVoided(
            OrderFillVoidedSpec::builder()
                .trade_id(TradeId::from("TRADE-VOID"))
                .voided_qty(Quantity::from(100_001))
                .build(),
        ));
        assert!(matches!(
            duplicate,
            Err(OrderError::DuplicateFillVoid(trade_id))
                if trade_id == TradeId::from("TRADE-VOID")
        ));
        assert!(matches!(
            stale,
            Err(OrderError::StaleFillVoid(trade_id))
                if trade_id == TradeId::from("TRADE-VOID")
        ));
        assert!(matches!(
            over_void,
            Err(OrderError::OverVoid(trade_id))
                if trade_id == TradeId::from("TRADE-VOID")
        ));
        assert_eq!(order.filled_qty(), Quantity::from(60_000));
        assert_eq!(order.voided_qty(), Quantity::from(40_000));
    }

    #[rstest]
    fn test_unknown_fill_void_does_not_reverse_surviving_fill() {
        let init = OrderInitializedSpec::builder()
            .quantity(Quantity::from(100_000))
            .build();
        let filled = OrderFilledSpec::builder()
            .trade_id(TradeId::from("TRADE-APPLIED"))
            .last_qty(Quantity::from(60_000))
            .build();
        let voided = OrderFillVoidedSpec::builder()
            .trade_id(TradeId::from("TRADE-NEVER-APPLIED"))
            .voided_qty(Quantity::from(40_000))
            .build();
        let mut order: MarketOrder = init.try_into().unwrap();
        order
            .apply(OrderEventAny::Accepted(
                OrderAcceptedSpec::builder().build(),
            ))
            .unwrap();
        order.apply(OrderEventAny::Filled(filled)).unwrap();

        order.apply(OrderEventAny::FillVoided(voided)).unwrap();
        order
            .apply(OrderEventAny::FillVoided(
                OrderFillVoidedSpec::builder()
                    .trade_id(TradeId::from("TRADE-APPLIED"))
                    .voided_qty(Quantity::from(10_000))
                    .is_reopened(true)
                    .build(),
            ))
            .unwrap();
        let late_fill = order.apply(OrderEventAny::Filled(
            OrderFilledSpec::builder()
                .trade_id(TradeId::from("TRADE-LATE"))
                .last_qty(Quantity::from(10_000))
                .build(),
        ));

        assert_eq!(order.status(), OrderStatus::Voided);
        assert_eq!(order.filled_qty(), Quantity::from(50_000));
        assert_eq!(order.voided_qty(), Quantity::from(50_000));
        assert_eq!(order.leaves_qty(), Quantity::zero(0));
        assert!(order.is_closed());
        assert!(matches!(late_fill, Err(OrderError::InvalidStateTransition)));
    }

    #[rstest]
    fn test_order_state_transition_to_canceled() {
        let mut order: MarketOrder = OrderInitializedSpec::builder().build().try_into().unwrap();
        let submitted = OrderSubmittedSpec::builder().build();
        let canceled = OrderCanceledSpec::builder().build();

        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Canceled(canceled)).unwrap();

        assert_eq!(order.status(), OrderStatus::Canceled);
        assert!(order.is_closed());
        assert!(!order.is_open());
    }

    #[rstest]
    fn test_order_life_cycle_to_partially_filled() {
        let init = OrderInitializedSpec::builder().build();
        let submitted = OrderSubmittedSpec::builder().build();
        let accepted = OrderAcceptedSpec::builder().build();
        let filled = OrderFilledSpec::builder()
            .last_qty(Quantity::from(50_000))
            .build();

        let mut order: MarketOrder = init.clone().try_into().unwrap();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        order.apply(OrderEventAny::Filled(filled)).unwrap();

        assert_eq!(order.client_order_id, init.client_order_id);
        assert_eq!(order.status(), OrderStatus::PartiallyFilled);
        assert_eq!(order.filled_qty(), Quantity::from(50_000));
        assert_eq!(order.leaves_qty(), Quantity::from(50_000));
        assert!(order.is_open());
        assert!(!order.is_closed());
    }

    #[rstest]
    fn test_order_commission_calculation() {
        let mut order: MarketOrder = OrderInitializedSpec::builder().build().try_into().unwrap();
        order
            .commissions
            .insert(Currency::USD(), Money::new(10.0, Currency::USD()));

        assert_eq!(
            order.commission(&Currency::USD()),
            Some(Money::new(10.0, Currency::USD()))
        );
        assert_eq!(
            order.commissions_vec(),
            vec![Money::new(10.0, Currency::USD())]
        );
    }

    #[rstest]
    fn test_order_is_primary() {
        let order: MarketOrder = OrderInitializedSpec::builder()
            .exec_algorithm_id(ExecAlgorithmId::from("ALGO-001"))
            .exec_spawn_id(ClientOrderId::from("O-001"))
            .client_order_id(ClientOrderId::from("O-001"))
            .build()
            .try_into()
            .unwrap();

        assert!(order.is_primary());
        assert!(!order.is_spawned());
    }

    #[rstest]
    fn test_order_is_spawned() {
        let order: MarketOrder = OrderInitializedSpec::builder()
            .exec_algorithm_id(ExecAlgorithmId::from("ALGO-001"))
            .exec_spawn_id(ClientOrderId::from("O-002"))
            .client_order_id(ClientOrderId::from("O-001"))
            .build()
            .try_into()
            .unwrap();

        assert!(!order.is_primary());
        assert!(order.is_spawned());
    }

    #[rstest]
    fn test_order_is_contingency() {
        let order: MarketOrder = OrderInitializedSpec::builder()
            .contingency_type(ContingencyType::Oto)
            .linked_order_ids(vec![ClientOrderId::from("O-LINKED")])
            .build()
            .try_into()
            .unwrap();

        assert!(order.is_contingency());
        assert!(order.is_parent_order());
        assert!(!order.is_child_order());
    }

    #[rstest]
    fn test_order_is_child_order() {
        let order: MarketOrder = OrderInitializedSpec::builder()
            .parent_order_id(ClientOrderId::from("PARENT-001"))
            .build()
            .try_into()
            .unwrap();

        assert!(order.is_child_order());
        assert!(!order.is_parent_order());
    }

    #[rstest]
    fn test_to_own_book_order_timestamp_ordering() {
        use crate::orders::limit::LimitOrder;

        // Create order with distinct timestamps to verify parameter ordering
        let init = OrderInitializedSpec::builder()
            .price(Price::from("100.00"))
            .build();
        let submitted = OrderSubmittedSpec::builder()
            .ts_event(UnixNanos::from(1_000_000))
            .build();
        let accepted = OrderAcceptedSpec::builder()
            .ts_event(UnixNanos::from(2_000_000))
            .build();

        let mut order: LimitOrder = init.try_into().unwrap();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();

        let own_book_order = order.to_own_book_order();

        // Verify timestamps are in correct positions
        assert_eq!(own_book_order.ts_submitted, UnixNanos::from(1_000_000));
        assert_eq!(own_book_order.ts_accepted, UnixNanos::from(2_000_000));
        assert_eq!(own_book_order.ts_last, UnixNanos::from(2_000_000));
    }

    #[rstest]
    fn test_to_own_book_order_partial_fill_uses_leaves_qty() {
        use crate::orders::limit::LimitOrder;

        let init = OrderInitializedSpec::builder()
            .price(Price::from("100.00"))
            .quantity(Quantity::from(100_000))
            .build();
        let submitted = OrderSubmittedSpec::builder().build();
        let accepted = OrderAcceptedSpec::builder().build();
        let filled = OrderFilledSpec::builder()
            .order_type(OrderType::Limit)
            .last_qty(Quantity::from(40_000))
            .last_px(Price::from("100.00"))
            .build();

        let mut order: LimitOrder = init.try_into().unwrap();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        order.apply(OrderEventAny::Filled(filled)).unwrap();

        let own_book_order = order.to_own_book_order();

        assert_eq!(order.status(), OrderStatus::PartiallyFilled);
        assert_eq!(order.leaves_qty(), Quantity::from(60_000));
        assert_eq!(own_book_order.size, Quantity::from(60_000));
    }

    #[rstest]
    fn test_order_accepted_without_submitted_sets_account_id() {
        // Test external order flow: Initialized -> Accepted (no Submitted)
        let init = OrderInitializedSpec::builder().build();
        let accepted = OrderAcceptedSpec::builder()
            .account_id(AccountId::from("EXTERNAL-001"))
            .build();

        let mut order: MarketOrder = init.try_into().unwrap();

        // Verify account_id is initially None
        assert_eq!(order.account_id(), None);

        // Apply accepted event directly (external order case)
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();

        // Verify account_id is now set from the accepted event
        assert_eq!(order.account_id(), Some(AccountId::from("EXTERNAL-001")));
        assert_eq!(order.status(), OrderStatus::Accepted);
    }

    #[rstest]
    fn test_order_accepted_after_submitted_preserves_account_id() {
        // Test normal order flow: Initialized -> Submitted -> Accepted
        let init = OrderInitializedSpec::builder().build();
        let submitted = OrderSubmittedSpec::builder()
            .account_id(AccountId::from("SUBMITTED-001"))
            .build();
        let accepted = OrderAcceptedSpec::builder()
            .account_id(AccountId::from("ACCEPTED-001"))
            .build();

        let mut order: MarketOrder = init.try_into().unwrap();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();

        // After submitted, account_id should be set
        assert_eq!(order.account_id(), Some(AccountId::from("SUBMITTED-001")));

        // Apply accepted event
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();

        // account_id should now be updated to the accepted event's account_id
        assert_eq!(order.account_id(), Some(AccountId::from("ACCEPTED-001")));
        assert_eq!(order.status(), OrderStatus::Accepted);
    }

    #[rstest]
    fn test_overfill_tracks_overfill_qty() {
        // Test that overfill is tracked on the order
        let init = OrderInitializedSpec::builder()
            .quantity(Quantity::from(100_000))
            .build();
        let submitted = OrderSubmittedSpec::builder().build();
        let accepted = OrderAcceptedSpec::builder().build();
        let overfill = OrderFilledSpec::builder()
            .last_qty(Quantity::from(110_000)) // Overfill: 110k > 100k
            .build();

        let mut order: MarketOrder = init.try_into().unwrap();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        order.apply(OrderEventAny::Filled(overfill)).unwrap();

        // Order should track overfill
        assert_eq!(order.overfill_qty(), Quantity::from(10_000));
        assert_eq!(order.filled_qty(), Quantity::from(110_000));
        assert_eq!(order.leaves_qty(), Quantity::from(0));
        assert_eq!(order.status(), OrderStatus::Filled);
    }

    #[rstest]
    fn test_partial_fill_then_overfill() {
        // Test multiple fills resulting in overfill
        let init = OrderInitializedSpec::builder()
            .quantity(Quantity::from(100_000))
            .build();
        let submitted = OrderSubmittedSpec::builder().build();
        let accepted = OrderAcceptedSpec::builder().build();
        let fill1 = OrderFilledSpec::builder()
            .last_qty(Quantity::from(80_000))
            .trade_id(TradeId::from("TRADE-1"))
            .build();
        let fill2 = OrderFilledSpec::builder()
            .last_qty(Quantity::from(30_000)) // Total 110k > 100k
            .trade_id(TradeId::from("TRADE-2"))
            .build();

        let mut order: MarketOrder = init.try_into().unwrap();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        order.apply(OrderEventAny::Filled(fill1)).unwrap();

        // After first fill, no overfill
        assert_eq!(order.overfill_qty(), Quantity::from(0));
        assert_eq!(order.filled_qty(), Quantity::from(80_000));
        assert_eq!(order.leaves_qty(), Quantity::from(20_000));

        order.apply(OrderEventAny::Filled(fill2)).unwrap();

        // After second fill, overfill detected
        assert_eq!(order.overfill_qty(), Quantity::from(10_000));
        assert_eq!(order.filled_qty(), Quantity::from(110_000));
        assert_eq!(order.leaves_qty(), Quantity::from(0));
        assert_eq!(order.status(), OrderStatus::Filled);
    }

    #[rstest]
    fn test_exact_fill_no_overfill() {
        // Test that exact fill doesn't trigger overfill tracking
        let init = OrderInitializedSpec::builder()
            .quantity(Quantity::from(100_000))
            .build();
        let submitted = OrderSubmittedSpec::builder().build();
        let accepted = OrderAcceptedSpec::builder().build();
        let filled = OrderFilledSpec::builder()
            .last_qty(Quantity::from(100_000)) // Exact fill
            .build();

        let mut order: MarketOrder = init.try_into().unwrap();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        order.apply(OrderEventAny::Filled(filled)).unwrap();

        // No overfill
        assert_eq!(order.overfill_qty(), Quantity::from(0));
        assert_eq!(order.filled_qty(), Quantity::from(100_000));
        assert_eq!(order.leaves_qty(), Quantity::from(0));
    }

    #[rstest]
    fn test_partial_fill_then_overfill_with_fractional_quantities() {
        // Simulates real exchange scenario with fractional fills:
        // Order for 2450.5 units, partially filled 1202.5, then fill of 1285.5 arrives
        // Total filled: 2488.0, overfill: 37.5
        let init = OrderInitializedSpec::builder()
            .quantity(Quantity::from("2450.5"))
            .build();
        let submitted = OrderSubmittedSpec::builder().build();
        let accepted = OrderAcceptedSpec::builder().build();
        let fill1 = OrderFilledSpec::builder()
            .last_qty(Quantity::from("1202.5"))
            .trade_id(TradeId::from("TRADE-1"))
            .build();
        let fill2 = OrderFilledSpec::builder()
            .last_qty(Quantity::from("1285.5")) // 1202.5 + 1285.5 = 2488 > 2450.5
            .trade_id(TradeId::from("TRADE-2"))
            .build();

        let mut order: MarketOrder = init.try_into().unwrap();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        order.apply(OrderEventAny::Filled(fill1)).unwrap();

        // After first fill, no overfill
        assert_eq!(order.overfill_qty(), Quantity::from(0));
        assert_eq!(order.filled_qty(), Quantity::from("1202.5"));
        assert_eq!(order.leaves_qty(), Quantity::from("1248.0"));
        assert_eq!(order.status(), OrderStatus::PartiallyFilled);

        order.apply(OrderEventAny::Filled(fill2)).unwrap();

        // After second fill, overfill detected and tracked
        assert_eq!(order.overfill_qty(), Quantity::from("37.5"));
        assert_eq!(order.filled_qty(), Quantity::from("2488.0"));
        assert_eq!(order.leaves_qty(), Quantity::from(0));
        assert_eq!(order.status(), OrderStatus::Filled);
    }

    #[rstest]
    fn test_calculate_overfill_returns_zero_when_no_overfill() {
        let order: MarketOrder = OrderInitializedSpec::builder()
            .quantity(Quantity::from(100_000))
            .build()
            .try_into()
            .unwrap();

        // Fill qty less than order qty - no overfill
        let overfill = order.calculate_overfill(Quantity::from(50_000));
        assert_eq!(overfill, Quantity::from(0));

        // Fill qty equals order qty - no overfill
        let overfill = order.calculate_overfill(Quantity::from(100_000));
        assert_eq!(overfill, Quantity::from(0));
    }

    #[rstest]
    fn test_calculate_overfill_returns_overfill_amount() {
        let order: MarketOrder = OrderInitializedSpec::builder()
            .quantity(Quantity::from(100_000))
            .build()
            .try_into()
            .unwrap();

        // Fill qty exceeds order qty
        let overfill = order.calculate_overfill(Quantity::from(110_000));
        assert_eq!(overfill, Quantity::from(10_000));
    }

    #[rstest]
    fn test_calculate_overfill_accounts_for_existing_fills() {
        let init = OrderInitializedSpec::builder()
            .quantity(Quantity::from(100_000))
            .build();
        let submitted = OrderSubmittedSpec::builder().build();
        let accepted = OrderAcceptedSpec::builder().build();
        let partial_fill = OrderFilledSpec::builder()
            .last_qty(Quantity::from(60_000))
            .build();

        let mut order: MarketOrder = init.try_into().unwrap();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        order.apply(OrderEventAny::Filled(partial_fill)).unwrap();

        // Order is 60k filled, 40k remaining
        // Fill of 50k would overfill by 10k
        let overfill = order.calculate_overfill(Quantity::from(50_000));
        assert_eq!(overfill, Quantity::from(10_000));

        // Fill of 40k would not overfill
        let overfill = order.calculate_overfill(Quantity::from(40_000));
        assert_eq!(overfill, Quantity::from(0));
    }

    #[rstest]
    fn test_calculate_overfill_with_fractional_quantities() {
        let order: MarketOrder = OrderInitializedSpec::builder()
            .quantity(Quantity::from("2450.5"))
            .build()
            .try_into()
            .unwrap();

        // Simulates the exact scenario from user's log
        // Order for 2450.5, if fill of 2488.0 arrives
        let overfill = order.calculate_overfill(Quantity::from("2488.0"));
        assert_eq!(overfill, Quantity::from("37.5"));
    }

    #[rstest]
    fn test_calculate_overfill_zero_after_fractional_partial_fill() {
        let init = OrderInitializedSpec::builder()
            .quantity(Quantity::from("1.000"))
            .build();
        let submitted = OrderSubmittedSpec::builder().build();
        let accepted = OrderAcceptedSpec::builder().build();
        let partial_fill = OrderFilledSpec::builder()
            .last_qty(Quantity::from("0.072"))
            .build();

        let mut order: MarketOrder = init.try_into().unwrap();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        order.apply(OrderEventAny::Filled(partial_fill)).unwrap();

        // After filling 0.072 of 1.000, another 0.072 fill should not overfill
        let overfill = order.calculate_overfill(Quantity::from("0.072"));
        assert_eq!(overfill, Quantity::from("0.000"));
    }

    #[rstest]
    fn test_duplicate_fill_rejected() {
        let init = OrderInitializedSpec::builder()
            .quantity(Quantity::from(100_000))
            .build();
        let submitted = OrderSubmittedSpec::builder().build();
        let accepted = OrderAcceptedSpec::builder().build();
        let fill1 = OrderFilledSpec::builder()
            .last_qty(Quantity::from(50_000))
            .trade_id(TradeId::from("TRADE-001"))
            .build();
        let fill2_duplicate = OrderFilledSpec::builder()
            .last_qty(Quantity::from(50_000))
            .trade_id(TradeId::from("TRADE-001")) // Same trade_id as fill1
            .build();

        let mut order: MarketOrder = init.try_into().unwrap();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        order.apply(OrderEventAny::Filled(fill1)).unwrap();

        // Verify first fill applied successfully
        assert_eq!(order.filled_qty(), Quantity::from(50_000));
        assert_eq!(order.status(), OrderStatus::PartiallyFilled);

        // Applying duplicate fill should return DuplicateFill error
        let result = order.apply(OrderEventAny::Filled(fill2_duplicate));
        assert!(result.is_err());
        match result.unwrap_err() {
            OrderError::DuplicateFill(trade_id) => {
                assert_eq!(trade_id, TradeId::from("TRADE-001"));
            }
            e => panic!("Expected DuplicateFill error, was: {e:?}"),
        }

        // Order state should be unchanged after rejected duplicate
        assert_eq!(order.filled_qty(), Quantity::from(50_000));
        assert_eq!(order.status(), OrderStatus::PartiallyFilled);
    }

    #[rstest]
    fn test_fill_raw_overflow_rejected_without_mutation() {
        let unit = Quantity::from(1);
        let almost_max = Quantity::from_raw(QUANTITY_RAW_MAX - unit.raw, 0);
        let max = Quantity::from_raw(QUANTITY_RAW_MAX, 0);
        let init = OrderInitializedSpec::builder().quantity(max).build();
        let accepted = OrderAcceptedSpec::builder().build();
        let fill1 = OrderFilledSpec::builder()
            .last_qty(almost_max)
            .trade_id(TradeId::from("TRADE-001"))
            .build();
        let fill2 = OrderFilledSpec::builder()
            .last_qty(Quantity::from(2))
            .trade_id(TradeId::from("TRADE-002"))
            .build();

        let mut order: MarketOrder = init.try_into().unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        order.apply(OrderEventAny::Filled(fill1)).unwrap();

        assert_eq!(order.filled_qty(), almost_max);
        assert_eq!(order.status(), OrderStatus::PartiallyFilled);

        let result = order.apply(OrderEventAny::Filled(fill2));
        let Err(OrderError::Invariant(CorrectnessError::PredicateViolation { message })) = result
        else {
            panic!("Expected typed invariant error, was: {result:?}");
        };
        assert_eq!(
            message,
            format!("filled quantity overflowed Quantity raw bounds: {almost_max} + 2")
        );
        assert_eq!(order.filled_qty(), almost_max);
        assert_eq!(order.status(), OrderStatus::PartiallyFilled);
        assert_eq!(order.event_count(), 3);
    }

    #[rstest]
    fn test_late_fill_on_filled_order_is_invalid_transition_not_overflow() {
        let max = Quantity::from_raw(QUANTITY_RAW_MAX, 0);
        let init = OrderInitializedSpec::builder().quantity(max).build();
        let accepted = OrderAcceptedSpec::builder().build();
        let fill1 = OrderFilledSpec::builder()
            .last_qty(max)
            .trade_id(TradeId::from("TRADE-001"))
            .build();
        let fill2 = OrderFilledSpec::builder()
            .last_qty(Quantity::from(1))
            .trade_id(TradeId::from("TRADE-002"))
            .build();

        let mut order: MarketOrder = init.try_into().unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        order.apply(OrderEventAny::Filled(fill1)).unwrap();

        let result = order.apply(OrderEventAny::Filled(fill2));
        assert!(matches!(result, Err(OrderError::InvalidStateTransition)));
        assert_eq!(order.filled_qty(), max);
        assert_eq!(order.status(), OrderStatus::Filled);
    }

    #[rstest]
    fn test_quantity_from_domain_raw_clamps_undef_sentinel() {
        let qty = quantity_from_domain_raw(QuantityRaw::MAX, 0);

        assert_eq!(qty, Quantity::from_raw(QUANTITY_RAW_MAX, 0));
        assert!(!qty.is_undefined());
    }

    #[rstest]
    fn test_check_display_qty_returns_typed_invariant_with_stable_display() {
        let error = check_display_qty(Some(Quantity::from(2)), Quantity::from(1)).unwrap_err();

        match error {
            OrderError::Invariant(CorrectnessError::PredicateViolation { ref message }) => {
                assert_eq!(message, "`display_qty` may not exceed `quantity`");
            }
            other => panic!("Expected typed invariant error, was: {other:?}"),
        }

        assert_eq!(error.to_string(), "`display_qty` may not exceed `quantity`");
    }

    #[rstest]
    fn test_check_time_in_force_returns_typed_invariant_with_stable_display() {
        let error = check_time_in_force(TimeInForce::Gtd, None).unwrap_err();

        match error {
            OrderError::Invariant(CorrectnessError::PredicateViolation { ref message }) => {
                assert_eq!(message, "`expire_time` is required for `GTD` order");
            }
            other => panic!("Expected typed invariant error, was: {other:?}"),
        }

        assert_eq!(
            error.to_string(),
            "`expire_time` is required for `GTD` order"
        );
    }

    #[rstest]
    fn test_different_trade_ids_allowed() {
        let init = OrderInitializedSpec::builder()
            .quantity(Quantity::from(100_000))
            .build();
        let submitted = OrderSubmittedSpec::builder().build();
        let accepted = OrderAcceptedSpec::builder().build();
        let fill1 = OrderFilledSpec::builder()
            .last_qty(Quantity::from(50_000))
            .trade_id(TradeId::from("TRADE-001"))
            .build();
        let fill2 = OrderFilledSpec::builder()
            .last_qty(Quantity::from(50_000))
            .trade_id(TradeId::from("TRADE-002")) // Different trade_id
            .build();

        let mut order: MarketOrder = init.try_into().unwrap();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        order.apply(OrderEventAny::Filled(fill1)).unwrap();
        order.apply(OrderEventAny::Filled(fill2)).unwrap();

        // Both fills should be applied
        assert_eq!(order.filled_qty(), Quantity::from(100_000));
        assert_eq!(order.status(), OrderStatus::Filled);
        assert_eq!(order.trade_ids.len(), 2);
    }

    #[rstest]
    fn test_pending_update_order_restores_status_on_updated() {
        let init = OrderInitializedSpec::builder()
            .quantity(Quantity::from(100_000))
            .build();
        let submitted = OrderSubmittedSpec::builder().build();
        let accepted = OrderAcceptedSpec::builder().build();
        let pending_update = OrderPendingUpdateSpec::builder().build();
        let updated = OrderUpdatedSpec::builder()
            .quantity(Quantity::from(50_000))
            .build();

        let mut order: MarketOrder = init.try_into().unwrap();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();

        assert_eq!(order.status(), OrderStatus::Accepted);

        order
            .apply(OrderEventAny::PendingUpdate(pending_update))
            .unwrap();
        assert_eq!(order.status(), OrderStatus::PendingUpdate);

        order.apply(OrderEventAny::Updated(updated)).unwrap();

        assert_eq!(order.status(), OrderStatus::Accepted);
        assert_eq!(order.quantity(), Quantity::from(50_000));
    }

    #[rstest]
    fn test_pending_update_accepts_delayed_submitted() {
        let init = OrderInitializedSpec::builder()
            .quantity(Quantity::from(100_000))
            .build();
        let submitted = OrderSubmittedSpec::builder()
            .ts_event(UnixNanos::from(1_000))
            .build();
        let accepted = OrderAcceptedSpec::builder().build();
        let pending_update = OrderPendingUpdateSpec::builder().build();

        // A distinct account and timestamp so the `submitted` handler's writes are
        // observable: with identical specs the assertions below cannot tell whether
        // the handler ran at all.
        let delayed_submitted = OrderSubmittedSpec::builder()
            .account_id(AccountId::from("SIM-002"))
            .ts_event(UnixNanos::from(3_000))
            .build();
        let updated = OrderUpdatedSpec::builder()
            .quantity(Quantity::from(50_000))
            .build();

        let mut order: MarketOrder = init.try_into().unwrap();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        order
            .apply(OrderEventAny::PendingUpdate(pending_update))
            .unwrap();

        assert_eq!(order.status(), OrderStatus::PendingUpdate);
        assert_eq!(order.previous_status(), Some(OrderStatus::Accepted));
        assert_eq!(order.account_id(), Some(AccountId::from("SIM-001")));
        assert_eq!(order.ts_submitted(), Some(UnixNanos::from(1_000)));

        order
            .apply(OrderEventAny::Submitted(delayed_submitted))
            .unwrap();

        // The order holds PendingUpdate and keeps the pre-update status, so the
        // in-flight modify can still be resolved.
        assert_eq!(order.status(), OrderStatus::PendingUpdate);
        assert_eq!(order.previous_status(), Some(OrderStatus::Accepted));

        assert_eq!(order.account_id(), Some(AccountId::from("SIM-002")));
        assert_eq!(order.ts_submitted(), Some(UnixNanos::from(3_000)));

        order.apply(OrderEventAny::Updated(updated)).unwrap();

        assert_eq!(order.status(), OrderStatus::Accepted);
        assert_eq!(order.quantity(), Quantity::from(50_000));
    }

    #[rstest]
    fn test_rejected_event_preserves_status_restoration() {
        let init = OrderInitializedSpec::builder().build();
        let submitted = OrderSubmittedSpec::builder().build();
        let accepted = OrderAcceptedSpec::builder().build();
        let invalid = OrderSubmittedSpec::builder().build();
        let pending_update = OrderPendingUpdateSpec::builder().build();
        let modify_rejected = OrderModifyRejectedSpec::builder().build();
        let mut order: MarketOrder = init.try_into().unwrap();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        let previous_status = order.previous_status();

        let result = order.apply(OrderEventAny::Submitted(invalid));

        assert!(matches!(result, Err(OrderError::InvalidStateTransition)));
        assert_eq!(order.previous_status(), previous_status);

        order
            .apply(OrderEventAny::PendingUpdate(pending_update))
            .unwrap();
        order
            .apply(OrderEventAny::ModifyRejected(modify_rejected))
            .unwrap();
        assert_eq!(order.status(), OrderStatus::Accepted);
    }

    #[rstest]
    fn test_rejected_event_preserves_cancel_rejected_restoration() {
        let init = OrderInitializedSpec::builder().build();
        let submitted = OrderSubmittedSpec::builder().build();
        let accepted = OrderAcceptedSpec::builder().build();
        let invalid = OrderSubmittedSpec::builder().build();
        let pending_cancel = OrderPendingCancelSpec::builder().build();
        let cancel_rejected = OrderCancelRejectedSpec::builder().build();
        let mut order: MarketOrder = init.try_into().unwrap();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        let previous_status = order.previous_status();

        let result = order.apply(OrderEventAny::Submitted(invalid));

        assert!(matches!(result, Err(OrderError::InvalidStateTransition)));
        assert_eq!(order.previous_status(), previous_status);

        order
            .apply(OrderEventAny::PendingCancel(pending_cancel))
            .unwrap();
        order
            .apply(OrderEventAny::CancelRejected(cancel_rejected))
            .unwrap();
        assert_eq!(order.status(), OrderStatus::Accepted);
    }

    #[rstest]
    #[case(true, false, "client_order_id")]
    #[case(false, true, "strategy_id")]
    fn test_update_identity_mismatch_precedes_field_validation(
        #[case] wrong_client: bool,
        #[case] wrong_strategy: bool,
        #[case] expected_field: &str,
    ) {
        let init = OrderInitializedSpec::builder().build();
        let submitted = OrderSubmittedSpec::builder().build();
        let accepted = OrderAcceptedSpec::builder().build();
        let mut order: MarketOrder = init.try_into().unwrap();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        let state = (
            order.status(),
            order.previous_status(),
            order.ts_last(),
            order.events().len(),
        );
        let client_order_id = if wrong_client {
            ClientOrderId::from("O-INVALID")
        } else {
            order.client_order_id()
        };
        let strategy_id = if wrong_strategy {
            StrategyId::from("OTHER-001")
        } else {
            order.strategy_id()
        };
        // Carry both a mismatched identity and a price a MarketOrder cannot hold:
        // the identity mismatch must be reported ahead of the field violation.
        let updated = OrderUpdatedSpec::builder()
            .client_order_id(client_order_id)
            .strategy_id(strategy_id)
            .price(Price::new(95.0, 2))
            .build();

        let result = order.apply(OrderEventAny::Updated(updated));

        // The specific identity predicate must surface, not the field violation.
        let Err(OrderError::Invariant(CorrectnessError::PredicateViolation { message })) = result
        else {
            panic!("expected an identity predicate violation, was {result:?}");
        };
        assert!(
            message.contains(expected_field),
            "message did not name {expected_field}: {message}"
        );
        assert_eq!(order.status(), state.0);
        assert_eq!(order.previous_status(), state.1);
        assert_eq!(order.ts_last(), state.2);
        assert_eq!(order.events().len(), state.3);
    }

    #[rstest]
    fn test_update_invalid_transition_precedes_field_validation() {
        let init = OrderInitializedSpec::builder().build();
        let denied = OrderDeniedSpec::builder().build();
        let mut order: MarketOrder = init.try_into().unwrap();
        order.apply(OrderEventAny::Denied(denied)).unwrap();
        let state = (
            order.status(),
            order.previous_status(),
            order.ts_last(),
            order.events().len(),
        );
        // No (Denied, Updated) transition exists, and the price is invalid for a
        // MarketOrder: the transition check must win over the field violation.
        let updated = OrderUpdatedSpec::builder()
            .price(Price::new(95.0, 2))
            .build();

        let result = order.apply(OrderEventAny::Updated(updated));

        assert!(matches!(result, Err(OrderError::InvalidStateTransition)));
        assert_eq!(order.status(), state.0);
        assert_eq!(order.previous_status(), state.1);
        assert_eq!(order.ts_last(), state.2);
        assert_eq!(order.events().len(), state.3);
    }

    #[rstest]
    fn test_direct_update_panics_on_invalid_field_before_mutation() {
        let init = OrderInitializedSpec::builder()
            .quantity(Quantity::from(100_000))
            .build();
        let mut order: MarketOrder = init.try_into().unwrap();
        let original_quantity = order.quantity();
        // A distinct quantity so any mutation would be observable, alongside a
        // price the type cannot hold. The low-level mutation path retains a
        // defensive guard: a direct update() panics on the invalid field before
        // it reaches the quantity assignment.
        let updated = OrderUpdatedSpec::builder()
            .quantity(Quantity::from(50_000))
            .price(Price::new(95.0, 2))
            .build();

        let result =
            std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| order.update(&updated)));

        assert!(result.is_err());
        assert_eq!(order.quantity(), original_quantity);
    }

    #[rstest]
    fn test_partially_filled_order_can_be_updated() {
        // Test that a partially filled order can receive an Updated event
        // and remain in PartiallyFilled status
        let init = OrderInitializedSpec::builder()
            .quantity(Quantity::from(100_000))
            .build();
        let submitted = OrderSubmittedSpec::builder().build();
        let accepted = OrderAcceptedSpec::builder().build();
        let partial_fill = OrderFilledSpec::builder()
            .last_qty(Quantity::from(40_000))
            .build();
        let updated = OrderUpdatedSpec::builder()
            .quantity(Quantity::from(80_000)) // Reduce to 80k (still > 40k filled)
            .build();

        let mut order: MarketOrder = init.try_into().unwrap();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        order.apply(OrderEventAny::Filled(partial_fill)).unwrap();

        assert_eq!(order.status(), OrderStatus::PartiallyFilled);
        assert_eq!(order.filled_qty(), Quantity::from(40_000));

        order.apply(OrderEventAny::Updated(updated)).unwrap();

        assert_eq!(order.status(), OrderStatus::PartiallyFilled);
        assert_eq!(order.quantity(), Quantity::from(80_000));
        assert_eq!(order.leaves_qty(), Quantity::from(40_000)); // 80k - 40k filled
    }

    #[rstest]
    fn test_triggered_order_can_be_updated() {
        // Test that a triggered order can receive an Updated event
        // and remain in Triggered status
        let instrument_id = InstrumentId::from("ETHUSDT-LINEAR.BYBIT");
        let submitted = OrderSubmittedSpec::builder().build();
        let accepted = OrderAcceptedSpec::builder().build();
        let triggered = OrderTriggeredSpec::builder().build();
        let updated = OrderUpdatedSpec::builder()
            .quantity(Quantity::from(80_000))
            .build();

        let mut order = OrderTestBuilder::new(OrderType::StopLimit)
            .instrument_id(instrument_id)
            .quantity(Quantity::from(100_000))
            .price(Price::from("0.99500"))
            .trigger_price(Price::from("1.00000"))
            .trigger_type(TriggerType::LastPrice)
            .build();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        order.apply(OrderEventAny::Triggered(triggered)).unwrap();

        assert_eq!(order.status(), OrderStatus::Triggered);

        order.apply(OrderEventAny::Updated(updated)).unwrap();

        assert_eq!(order.status(), OrderStatus::Triggered);
        assert_eq!(order.quantity(), Quantity::from(80_000));
    }

    #[rstest]
    fn test_order_updated_with_is_quote_quantity_clears_flag() {
        let init = OrderInitializedSpec::builder()
            .quantity(Quantity::new(10.0, 6))
            .quote_quantity(true)
            .build();
        let submitted = OrderSubmittedSpec::builder().build();
        let accepted = OrderAcceptedSpec::builder().build();
        let updated = OrderUpdatedSpec::builder()
            .quantity(Quantity::new(47.393_365, 6))
            .is_quote_quantity(false)
            .build();

        let mut order: MarketOrder = init.try_into().unwrap();
        assert!(order.is_quote_quantity());

        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        order.apply(OrderEventAny::Updated(updated)).unwrap();

        assert!(!order.is_quote_quantity());
        assert_eq!(order.quantity(), Quantity::new(47.393_365, 6));
        assert_eq!(order.leaves_qty(), Quantity::new(47.393_365, 6));
    }

    #[rstest]
    fn test_order_updated_default_is_quote_quantity_clears_flag() {
        let init = OrderInitializedSpec::builder()
            .quantity(Quantity::new(10.0, 6))
            .quote_quantity(true)
            .build();
        let submitted = OrderSubmittedSpec::builder().build();
        let accepted = OrderAcceptedSpec::builder().build();
        // Builder defaults is_quote_quantity to false
        let updated = OrderUpdatedSpec::builder()
            .quantity(Quantity::new(8.0, 6))
            .build();

        let mut order: MarketOrder = init.try_into().unwrap();
        assert!(order.is_quote_quantity());

        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        order.apply(OrderEventAny::Updated(updated)).unwrap();

        assert!(!order.is_quote_quantity());
        assert_eq!(order.quantity(), Quantity::new(8.0, 6));
    }

    #[rstest]
    fn test_canceled_then_partial_fill_then_canceled() {
        let mut order: MarketOrder = OrderInitializedSpec::builder().build().try_into().unwrap();
        let submitted = OrderSubmittedSpec::builder().build();
        let accepted = OrderAcceptedSpec::builder().build();
        let canceled1 = OrderCanceledSpec::builder().build();
        let fill = OrderFilledSpec::builder()
            .last_qty(Quantity::from(50_000))
            .trade_id(TradeId::from("FILL-1"))
            .build();
        let canceled2 = OrderCanceledSpec::builder().build();

        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        order.apply(OrderEventAny::Canceled(canceled1)).unwrap();
        assert_eq!(order.status(), OrderStatus::Canceled);
        assert!(order.is_closed());

        // Fill arrives after cancel (real-world race condition)
        order.apply(OrderEventAny::Filled(fill)).unwrap();
        assert_eq!(order.status(), OrderStatus::PartiallyFilled);
        assert_eq!(order.filled_qty(), Quantity::from(50_000));
        assert!(order.is_open());

        // Re-emitted cancel restores terminal state
        order.apply(OrderEventAny::Canceled(canceled2)).unwrap();
        assert_eq!(order.status(), OrderStatus::Canceled);
        assert!(order.is_closed());
    }

    #[rstest]
    fn test_updated_restores_status_before_pending_cancel() {
        let mut order: MarketOrder = OrderInitializedSpec::builder().build().try_into().unwrap();
        let submitted = OrderSubmittedSpec::builder().build();
        let accepted = OrderAcceptedSpec::builder().build();
        let pending_cancel = OrderPendingCancelSpec::builder().build();
        let updated = OrderUpdatedSpec::builder()
            .quantity(Quantity::from(150_000))
            .build();

        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        let ts_accepted = order.ts_accepted();
        let venue_order_ids: Vec<VenueOrderId> =
            order.venue_order_ids().into_iter().copied().collect();
        order
            .apply(OrderEventAny::PendingCancel(pending_cancel))
            .unwrap();
        order.apply(OrderEventAny::Updated(updated)).unwrap();

        assert_eq!(order.status(), OrderStatus::Accepted);
        assert_eq!(order.quantity(), Quantity::from(150_000));
        assert_eq!(order.ts_accepted(), ts_accepted);
        assert_eq!(
            order
                .venue_order_ids()
                .into_iter()
                .copied()
                .collect::<Vec<_>>(),
            venue_order_ids,
        );
    }

    #[rstest]
    fn test_apply_triggered_to_stop_market_order_returns_error() {
        let instrument_id = InstrumentId::from("ETHUSDT-LINEAR.BYBIT");
        let submitted = OrderSubmittedSpec::builder().build();
        let accepted = OrderAcceptedSpec::builder().build();
        let triggered = OrderTriggeredSpec::builder().build();

        let mut order = OrderTestBuilder::new(OrderType::StopMarket)
            .instrument_id(instrument_id)
            .quantity(Quantity::from(1))
            .trigger_price(Price::from("1.00000"))
            .trigger_type(TriggerType::LastPrice)
            .build();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();

        let result = order.apply(OrderEventAny::Triggered(triggered));
        assert!(result.is_err());
        assert_eq!(order.status(), OrderStatus::Accepted);
    }

    #[rstest]
    fn test_apply_triggered_to_stop_limit_order_succeeds() {
        let instrument_id = InstrumentId::from("ETHUSDT-LINEAR.BYBIT");
        let submitted = OrderSubmittedSpec::builder().build();
        let accepted = OrderAcceptedSpec::builder().build();
        let triggered = OrderTriggeredSpec::builder().build();

        let mut order = OrderTestBuilder::new(OrderType::StopLimit)
            .instrument_id(instrument_id)
            .quantity(Quantity::from(1))
            .price(Price::from("0.99500"))
            .trigger_price(Price::from("1.00000"))
            .trigger_type(TriggerType::LastPrice)
            .build();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        order.apply(OrderEventAny::Triggered(triggered)).unwrap();

        assert_eq!(order.status(), OrderStatus::Triggered);
    }

    #[rstest]
    fn test_to_order_status_report_for_accepted_limit_order() {
        let order = OrderTestBuilder::new(OrderType::Limit)
            .instrument_id(InstrumentId::from("AUDUSD.SIM"))
            .side(OrderSide::Buy)
            .quantity(Quantity::from(100_000))
            .price(Price::from("1.00000"))
            .build();
        let accepted = TestOrderStubs::make_accepted_order(&order);

        let report = accepted.to_order_status_report(None).unwrap();

        assert_eq!(report.account_id, AccountId::from("SIM-001"));
        assert_eq!(report.instrument_id, InstrumentId::from("AUDUSD.SIM"));
        assert_eq!(report.client_order_id, Some(accepted.client_order_id()));
        assert_eq!(report.venue_order_id, VenueOrderId::from("V-001"));
        assert_eq!(report.order_side, OrderSide::Buy);
        assert_eq!(report.order_type, OrderType::Limit);
        assert_eq!(report.time_in_force, accepted.time_in_force());
        assert_eq!(report.order_status, OrderStatus::Accepted);
        assert_eq!(report.quantity, Quantity::from(100_000));
        assert_eq!(report.filled_qty, Quantity::from(0));
        assert_eq!(report.price, Some(Price::from("1.00000")));
        assert_eq!(report.avg_px, None);
        assert_eq!(report.ts_accepted, accepted.ts_accepted().unwrap());
        assert_eq!(report.ts_last, accepted.ts_last());
        assert_eq!(report.ts_init, accepted.ts_init());
    }

    #[rstest]
    fn test_to_order_status_report_for_filled_market_order(audusd_sim: CurrencyPair) {
        let audusd_sim = InstrumentAny::CurrencyPair(audusd_sim);
        let order = OrderTestBuilder::new(OrderType::Market)
            .instrument_id(audusd_sim.id())
            .side(OrderSide::Buy)
            .quantity(Quantity::from(100_000))
            .build();
        let filled = TestOrderStubs::make_filled_order(&order, &audusd_sim, LiquiditySide::Maker);
        let report_id = UUID4::new();

        let report = filled.to_order_status_report(Some(report_id)).unwrap();

        assert_eq!(report.report_id, report_id);
        assert_eq!(report.order_status, OrderStatus::Filled);
        assert_eq!(report.quantity, Quantity::from(100_000));
        assert_eq!(report.filled_qty, Quantity::from(100_000));
        assert_eq!(report.price, None);
        assert_eq!(report.avg_px, Some(dec!(1)));
        assert_eq!(report.venue_position_id, Some(PositionId::from("1")));
        assert_eq!(report.ts_accepted, filled.ts_accepted().unwrap());
        assert_eq!(report.ts_last, filled.ts_last());
    }

    #[rstest]
    fn test_to_order_status_report_maps_optional_fields() {
        let order = OrderTestBuilder::new(OrderType::StopLimit)
            .instrument_id(InstrumentId::from("AUDUSD.SIM"))
            .side(OrderSide::Sell)
            .quantity(Quantity::from(100_000))
            .price(Price::from("0.99500"))
            .trigger_price(Price::from("1.00000"))
            .trigger_type(TriggerType::LastPrice)
            .time_in_force(TimeInForce::Gtd)
            .expire_time(UnixNanos::from(5_000_000_000))
            .display_qty(Quantity::from(10_000))
            .post_only(true)
            .reduce_only(true)
            .contingency_type(ContingencyType::Oto)
            .order_list_id(OrderListId::from("OL-001"))
            .linked_order_ids(vec![ClientOrderId::from("O-CHILD")])
            .parent_order_id(ClientOrderId::from("O-PARENT"))
            .build();
        let accepted = TestOrderStubs::make_accepted_order(&order);

        let report = accepted.to_order_status_report(None).unwrap();

        assert_eq!(report.price, Some(Price::from("0.99500")));
        assert_eq!(report.trigger_price, Some(Price::from("1.00000")));
        assert_eq!(report.trigger_type, Some(TriggerType::LastPrice));
        assert_eq!(report.expire_time, Some(UnixNanos::from(5_000_000_000)));
        assert_eq!(report.display_qty, Some(Quantity::from(10_000)));
        assert!(report.post_only);
        assert!(report.reduce_only);
        assert_eq!(report.contingency_type, ContingencyType::Oto);
        assert_eq!(report.order_list_id, Some(OrderListId::from("OL-001")));
        assert_eq!(
            report.linked_order_ids,
            Some(vec![ClientOrderId::from("O-CHILD")])
        );
        assert_eq!(
            report.parent_order_id,
            Some(ClientOrderId::from("O-PARENT"))
        );
    }

    #[rstest]
    fn test_to_order_status_report_maps_ts_triggered() {
        let order = OrderTestBuilder::new(OrderType::StopLimit)
            .instrument_id(InstrumentId::from("AUDUSD.SIM"))
            .side(OrderSide::Buy)
            .quantity(Quantity::from(100_000))
            .price(Price::from("0.99500"))
            .trigger_price(Price::from("1.00000"))
            .trigger_type(TriggerType::LastPrice)
            .build();
        let mut order = TestOrderStubs::make_accepted_order(&order);
        let triggered = OrderTriggeredSpec::builder()
            .ts_event(UnixNanos::from(1_500_000_000))
            .build();
        order.apply(OrderEventAny::Triggered(triggered)).unwrap();

        let report = order.to_order_status_report(None).unwrap();

        assert_eq!(report.order_status, OrderStatus::Triggered);
        assert_eq!(report.ts_triggered, Some(UnixNanos::from(1_500_000_000)));
    }

    #[rstest]
    fn test_to_order_status_report_maps_rejection_reason() {
        let order = OrderTestBuilder::new(OrderType::Limit)
            .instrument_id(InstrumentId::from("AUDUSD.SIM"))
            .side(OrderSide::Buy)
            .quantity(Quantity::from(100_000))
            .price(Price::from("1.00000"))
            .build();
        let mut order = TestOrderStubs::make_accepted_order(&order);
        let rejected = OrderRejectedSpec::builder()
            .reason(Ustr::from("INSUFFICIENT_MARGIN"))
            .build();
        order.apply(OrderEventAny::Rejected(rejected)).unwrap();

        let report = order.to_order_status_report(None).unwrap();

        assert_eq!(report.order_status, OrderStatus::Rejected);
        assert_eq!(
            report.cancel_reason,
            Some("INSUFFICIENT_MARGIN".to_string())
        );
    }

    #[rstest]
    fn test_to_order_status_report_maps_distinct_timestamps() {
        let mut order = OrderTestBuilder::new(OrderType::Limit)
            .instrument_id(InstrumentId::from("AUDUSD.SIM"))
            .side(OrderSide::Buy)
            .quantity(Quantity::from(100_000))
            .price(Price::from("1.00000"))
            .ts_init(UnixNanos::from(1_000))
            .build();
        let submitted = OrderSubmittedSpec::builder()
            .ts_event(UnixNanos::from(2_000))
            .build();
        let accepted = OrderAcceptedSpec::builder()
            .ts_event(UnixNanos::from(3_000))
            .build();
        let filled = OrderFilledSpec::builder()
            .last_qty(Quantity::from(50_000))
            .ts_event(UnixNanos::from(4_000))
            .build();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Accepted(accepted)).unwrap();
        order.apply(OrderEventAny::Filled(filled)).unwrap();

        let report = order.to_order_status_report(None).unwrap();

        assert_eq!(report.order_status, OrderStatus::PartiallyFilled);
        assert_eq!(report.filled_qty, Quantity::from(50_000));
        assert_eq!(report.ts_accepted, UnixNanos::from(3_000));
        assert_eq!(report.ts_last, UnixNanos::from(4_000));
        assert_eq!(report.ts_init, UnixNanos::from(1_000));
    }

    #[rstest]
    fn test_to_order_status_report_ts_accepted_falls_back_to_ts_last() {
        // Venue ack can arrive through an update before any acceptance event
        let mut order = OrderTestBuilder::new(OrderType::Limit)
            .instrument_id(InstrumentId::from("AUDUSD.SIM"))
            .side(OrderSide::Buy)
            .quantity(Quantity::from(100_000))
            .price(Price::from("1.00000"))
            .build();
        let submitted = OrderSubmittedSpec::builder()
            .ts_event(UnixNanos::from(2_000))
            .build();
        let updated = OrderUpdatedSpec::builder()
            .venue_order_id(VenueOrderId::from("V-001"))
            .ts_event(UnixNanos::from(3_000))
            .build();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();
        order.apply(OrderEventAny::Updated(updated)).unwrap();

        let report = order.to_order_status_report(None).unwrap();

        assert_eq!(report.order_status, OrderStatus::Submitted);
        assert_eq!(report.venue_order_id, VenueOrderId::from("V-001"));
        assert_eq!(report.ts_accepted, UnixNanos::from(3_000));
        assert_eq!(report.ts_last, UnixNanos::from(3_000));
    }

    #[rstest]
    fn test_to_order_status_report_maps_trailing_offsets() {
        let order = OrderTestBuilder::new(OrderType::TrailingStopLimit)
            .instrument_id(InstrumentId::from("AUDUSD.SIM"))
            .side(OrderSide::Sell)
            .quantity(Quantity::from(100_000))
            .price(Price::from("0.99500"))
            .activation_price(Price::from("1.00500"))
            .trigger_price(Price::from("1.00000"))
            .trigger_type(TriggerType::LastPrice)
            .limit_offset(dec!(0.0001))
            .trailing_offset(dec!(0.0002))
            .trailing_offset_type(TrailingOffsetType::Price)
            .build();
        let accepted = TestOrderStubs::make_accepted_order(&order);

        let report = accepted.to_order_status_report(None).unwrap();

        assert_eq!(report.activation_price, Some(Price::from("1.00500")));
        assert_eq!(report.limit_offset, Some(dec!(0.0001)));
        assert_eq!(report.trailing_offset, Some(dec!(0.0002)));
        assert_eq!(report.trailing_offset_type, TrailingOffsetType::Price);
    }

    #[rstest]
    fn test_to_order_status_report_returns_none_before_venue_ack() {
        let order = OrderTestBuilder::new(OrderType::Limit)
            .instrument_id(InstrumentId::from("AUDUSD.SIM"))
            .side(OrderSide::Buy)
            .quantity(Quantity::from(100_000))
            .price(Price::from("1.00000"))
            .build();

        assert!(order.to_order_status_report(None).is_none());
    }

    #[rstest]
    fn test_to_order_status_report_returns_none_for_submitted_order() {
        // Inflight orders have an account_id but no venue_order_id yet
        let mut order = OrderTestBuilder::new(OrderType::Limit)
            .instrument_id(InstrumentId::from("AUDUSD.SIM"))
            .side(OrderSide::Buy)
            .quantity(Quantity::from(100_000))
            .price(Price::from("1.00000"))
            .build();
        let submitted = OrderSubmittedSpec::builder().build();
        order.apply(OrderEventAny::Submitted(submitted)).unwrap();

        assert!(order.account_id().is_some());
        assert!(order.to_order_status_report(None).is_none());
    }
}