nautilus_common/

clock.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.
// -------------------------------------------------------------------------------------------------

//! Real-time and static `Clock` implementations.

#![warn(clippy::clone_on_ref_ptr)]

use std::{
    any::Any,
    cell::RefCell,
    collections::{BTreeMap, BinaryHeap},
    fmt::Debug,
    ops::Deref,
    time::Duration,
};

use ahash::AHashMap;
use chrono::{DateTime, Utc};
use nautilus_core::{
    AtomicTime, UUID4, UnixNanos,
    correctness::{check_positive_u64, check_predicate_true, check_valid_string_utf8},
    datetime::NANOSECONDS_IN_SECOND,
    string::formatting::Separable,
};
use ustr::Ustr;

use crate::timer::{
    ScheduledTimeEvent, TestTimer, TimeEvent, TimeEventCallback, TimeEventHandler, Timer,
    create_valid_interval,
};

/// Represents a type of clock.
///
/// # Notes
///
/// An active timer is one which has not expired (`timer.is_expired == False`).
pub trait Clock: Debug + Any {
    /// Returns the current date and time as a timezone-aware `DateTime<UTC>`.
    fn utc_now(&self) -> DateTime<Utc> {
        DateTime::from_timestamp_nanos(self.timestamp_ns().as_i64())
    }

    /// Returns the current UNIX timestamp in nanoseconds (ns).
    fn timestamp_ns(&self) -> UnixNanos;

    /// Returns the current UNIX timestamp in microseconds (μs).
    fn timestamp_us(&self) -> u64;

    /// Returns the current UNIX timestamp in milliseconds (ms).
    fn timestamp_ms(&self) -> u64;

    /// Returns the current UNIX timestamp in seconds.
    fn timestamp(&self) -> f64;

    /// Returns the names of active timers in the clock.
    fn timer_names(&self) -> Vec<&str>;

    /// Returns the count of active timers in the clock.
    fn timer_count(&self) -> usize;

    /// If a timer with the `name` exists.
    fn timer_exists(&self, name: &Ustr) -> bool;

    /// Register a default event handler for the clock. If a timer
    /// does not have an event handler, then this handler is used.
    fn register_default_handler(&mut self, callback: TimeEventCallback);

    /// Cancel the registered default event handler (if any).
    ///
    /// Releases the held callback so any Python object owned by it can be dropped.
    /// Required to break reference cycles between Python components and their clock,
    /// since the clock stores callbacks as `Py<PyAny>` which Python's GC cannot trace.
    fn cancel_default_handler(&mut self);

    /// Cancel all registered named event callbacks.
    ///
    /// Releases callbacks registered via [`Clock::set_time_alert_ns`] or
    /// [`Clock::set_timer_ns`] with an explicit `callback` argument. Called during
    /// component disposal to break reference cycles via Python `Py<PyAny>` callbacks.
    fn cancel_callbacks(&mut self);

    /// Get handler for [`TimeEvent`].
    ///
    /// Note: Panics if the event does not have an associated handler
    fn get_handler(&self, event: TimeEvent) -> TimeEventHandler;

    /// Set a timer to alert at the specified time.
    ///
    /// See [`Clock::set_time_alert_ns`] for flag semantics.
    ///
    /// # Callback
    ///
    /// - `callback`: Some, then callback handles the time event.
    /// - `callback`: None, then the clock's default time event callback is used.
    ///
    /// # Errors
    ///
    /// Returns an error if `name` is invalid, `alert_time` is in the past when not allowed,
    /// or any predicate check fails.
    fn set_time_alert(
        &mut self,
        name: &str,
        alert_time: DateTime<Utc>,
        callback: Option<TimeEventCallback>,
        allow_past: Option<bool>,
    ) -> anyhow::Result<()> {
        self.set_time_alert_ns(name, alert_time.into(), callback, allow_past)
    }

    /// Set a timer to alert at the specified time.
    ///
    /// Any existing timer registered under the same `name` is cancelled with a warning before the new alert is scheduled.
    ///
    /// # Flags
    ///
    /// | `allow_past` | Behavior                                                                                |
    /// |--------------|-----------------------------------------------------------------------------------------|
    /// | `true`       | If alert time is **in the past**, the alert fires immediately; otherwise at alert time. |
    /// | `false`      | Returns an error if alert time is earlier than now.                                     |
    ///
    /// # Callback
    ///
    /// - `callback`: Some, then callback handles the time event.
    /// - `callback`: None, then the clock's default time event callback is used.
    ///
    /// # Errors
    ///
    /// Returns an error if `name` is invalid, `alert_time_ns` is earlier than now when not allowed,
    /// or any predicate check fails.
    fn set_time_alert_ns(
        &mut self,
        name: &str,
        alert_time_ns: UnixNanos,
        callback: Option<TimeEventCallback>,
        allow_past: Option<bool>,
    ) -> anyhow::Result<()>;

    /// Set a timer to fire time events at every interval between start and stop time.
    ///
    /// Any existing timer registered under the same `name` is cancelled with a warning before the new timer is scheduled.
    ///
    /// See [`Clock::set_timer_ns`] for flag semantics.
    ///
    /// # Callback
    ///
    /// - `callback`: Some, then callback handles the time event.
    /// - `callback`: None, then the clock's default time event callback is used.
    ///
    /// # Errors
    ///
    /// Returns an error if `name` is invalid, `interval` is not positive,
    /// or if any predicate check fails.
    #[expect(clippy::too_many_arguments)]
    fn set_timer(
        &mut self,
        name: &str,
        interval: Duration,
        start_time: Option<DateTime<Utc>>,
        stop_time: Option<DateTime<Utc>>,
        callback: Option<TimeEventCallback>,
        allow_past: Option<bool>,
        fire_immediately: Option<bool>,
    ) -> anyhow::Result<()> {
        self.set_timer_ns(
            name,
            interval.as_nanos() as u64,
            start_time.map(UnixNanos::from),
            stop_time.map(UnixNanos::from),
            callback,
            allow_past,
            fire_immediately,
        )
    }

    /// Set a timer to fire time events at every interval between start and stop time.
    ///
    /// Any existing timer registered under the same `name` is cancelled before the new timer is scheduled.
    ///
    /// # Start Time
    ///
    /// - `None` or `Some(0)`: Uses the current time as start time.
    /// - `Some(non_zero)`: Uses the specified timestamp as start time.
    ///
    /// # Flags
    ///
    /// | `allow_past` | `fire_immediately` | Behavior                                                                              |
    /// |--------------|--------------------|---------------------------------------------------------------------------------------|
    /// | `true`       | `true`             | First event fires immediately at start time, even if start time is in the past.       |
    /// | `true`       | `false`            | First event fires at start time + interval, even if start time is in the past.        |
    /// | `false`      | `true`             | Returns error if start time is in the past (first event would be immediate but past). |
    /// | `false`      | `false`            | Returns error if start time + interval is in the past.                                |
    ///
    /// # Callback
    ///
    /// - `callback`: Some, then callback handles the time event.
    /// - `callback`: None, then the clock's default time event callback is used.
    ///
    /// # Errors
    ///
    /// Returns an error if `name` is invalid, `interval_ns` is not positive,
    /// or if any predicate check fails.
    #[expect(clippy::too_many_arguments)]
    fn set_timer_ns(
        &mut self,
        name: &str,
        interval_ns: u64,
        start_time_ns: Option<UnixNanos>,
        stop_time_ns: Option<UnixNanos>,
        callback: Option<TimeEventCallback>,
        allow_past: Option<bool>,
        fire_immediately: Option<bool>,
    ) -> anyhow::Result<()>;

    /// Returns the time interval in which the timer `name` is triggered.
    ///
    /// If the timer doesn't exist `None` is returned.
    fn next_time_ns(&self, name: &str) -> Option<UnixNanos>;

    /// Cancels the timer with `name`.
    fn cancel_timer(&mut self, name: &str);

    /// Cancels all timers.
    fn cancel_timers(&mut self);

    /// Resets the clock by clearing it's internal state.
    fn reset(&mut self);
}

impl dyn Clock {
    /// Returns a reference to this clock as `Any` for downcasting.
    pub fn as_any(&self) -> &dyn std::any::Any {
        self
    }
    /// Returns a mutable reference to this clock as `Any` for downcasting.
    pub fn as_any_mut(&mut self) -> &mut dyn std::any::Any {
        self
    }
}

/// User-facing clock API.
#[derive(Debug)]
pub struct ClockApi<'a> {
    backing: ClockApiBacking<'a>,
}

enum ClockApiBacking<'a> {
    Native(&'a RefCell<dyn Clock>),
    Handlers(ClockApiHandlers<'a>),
}

struct ClockApiHandlers<'a> {
    timestamp_ns: Box<dyn Fn() -> UnixNanos + 'a>,
    set_time_alert_ns: Box<SetTimeAlertNsHandler<'a>>,
    set_timer_ns: Box<SetTimerNsHandler<'a>>,
    timer_names: Box<dyn Fn() -> Vec<String> + 'a>,
    timer_count: Box<dyn Fn() -> usize + 'a>,
    timer_exists: Box<dyn Fn(&str) -> bool + 'a>,
    next_time_ns: Box<NextTimeNsHandler<'a>>,
    cancel_timer: Box<dyn Fn(&str) + 'a>,
    cancel_timers: Box<dyn Fn() + 'a>,
}

impl Debug for ClockApiBacking<'_> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::Native(_) => f.write_str("Native"),
            Self::Handlers(_) => f.write_str("Handlers"),
        }
    }
}

type SetTimeAlertNsHandler<'a> =
    dyn Fn(&str, UnixNanos, Option<TimeEventCallback>, Option<bool>) -> anyhow::Result<()> + 'a;
type NextTimeNsHandler<'a> = dyn Fn(&str) -> Option<UnixNanos> + 'a;
type SetTimerNsHandler<'a> = dyn Fn(
        &str,
        u64,
        Option<UnixNanos>,
        Option<UnixNanos>,
        Option<TimeEventCallback>,
        Option<bool>,
        Option<bool>,
    ) -> anyhow::Result<()>
    + 'a;

impl<'a> ClockApi<'a> {
    pub(crate) fn new(clock: &'a RefCell<dyn Clock>) -> Self {
        Self {
            backing: ClockApiBacking::Native(clock),
        }
    }

    /// Creates a clock API from backing callbacks.
    #[doc(hidden)]
    #[must_use]
    #[expect(
        clippy::too_many_arguments,
        reason = "clock API backing mirrors the full ClockApi surface"
    )]
    pub fn from_handlers<
        TimestampNs,
        SetTimeAlertNs,
        SetTimerNs,
        TimerNames,
        TimerCount,
        TimerExists,
        NextTimeNs,
        CancelTimer,
        CancelTimers,
    >(
        timestamp_ns: TimestampNs,
        set_time_alert_ns: SetTimeAlertNs,
        set_timer_ns: SetTimerNs,
        timer_names: TimerNames,
        timer_count: TimerCount,
        timer_exists: TimerExists,
        next_time_ns: NextTimeNs,
        cancel_timer: CancelTimer,
        cancel_timers: CancelTimers,
    ) -> Self
    where
        TimestampNs: Fn() -> UnixNanos + 'a,
        SetTimeAlertNs:
            Fn(&str, UnixNanos, Option<TimeEventCallback>, Option<bool>) -> anyhow::Result<()> + 'a,
        SetTimerNs: Fn(
                &str,
                u64,
                Option<UnixNanos>,
                Option<UnixNanos>,
                Option<TimeEventCallback>,
                Option<bool>,
                Option<bool>,
            ) -> anyhow::Result<()>
            + 'a,
        TimerNames: Fn() -> Vec<String> + 'a,
        TimerCount: Fn() -> usize + 'a,
        TimerExists: Fn(&str) -> bool + 'a,
        NextTimeNs: Fn(&str) -> Option<UnixNanos> + 'a,
        CancelTimer: Fn(&str) + 'a,
        CancelTimers: Fn() + 'a,
    {
        Self {
            backing: ClockApiBacking::Handlers(ClockApiHandlers {
                timestamp_ns: Box::new(timestamp_ns),
                set_time_alert_ns: Box::new(set_time_alert_ns),
                set_timer_ns: Box::new(set_timer_ns),
                timer_names: Box::new(timer_names),
                timer_count: Box::new(timer_count),
                timer_exists: Box::new(timer_exists),
                next_time_ns: Box::new(next_time_ns),
                cancel_timer: Box::new(cancel_timer),
                cancel_timers: Box::new(cancel_timers),
            }),
        }
    }

    /// Returns the current UNIX nanoseconds timestamp.
    ///
    /// # Panics
    ///
    /// Panics if the clock is already mutably borrowed.
    #[must_use]
    pub fn timestamp_ns(&self) -> UnixNanos {
        match &self.backing {
            ClockApiBacking::Native(clock) => clock.borrow().timestamp_ns(),
            ClockApiBacking::Handlers(handlers) => (handlers.timestamp_ns)(),
        }
    }

    /// Returns the current UNIX timestamp in microseconds.
    ///
    /// # Panics
    ///
    /// Panics if the clock is already mutably borrowed.
    #[must_use]
    pub fn timestamp_us(&self) -> u64 {
        match &self.backing {
            ClockApiBacking::Native(clock) => clock.borrow().timestamp_us(),
            ClockApiBacking::Handlers(handlers) => (handlers.timestamp_ns)().as_micros(),
        }
    }

    /// Returns the current UNIX timestamp in milliseconds.
    ///
    /// # Panics
    ///
    /// Panics if the clock is already mutably borrowed.
    #[must_use]
    pub fn timestamp_ms(&self) -> u64 {
        match &self.backing {
            ClockApiBacking::Native(clock) => clock.borrow().timestamp_ms(),
            ClockApiBacking::Handlers(handlers) => (handlers.timestamp_ns)().as_millis(),
        }
    }

    /// Returns the current UNIX timestamp in seconds.
    ///
    /// # Panics
    ///
    /// Panics if the clock is already mutably borrowed.
    #[must_use]
    pub fn timestamp(&self) -> f64 {
        match &self.backing {
            ClockApiBacking::Native(clock) => clock.borrow().timestamp(),
            ClockApiBacking::Handlers(handlers) => {
                (handlers.timestamp_ns)().as_f64() / (NANOSECONDS_IN_SECOND as f64)
            }
        }
    }

    /// Returns the current UTC time.
    ///
    /// # Panics
    ///
    /// Panics if the clock is already mutably borrowed.
    #[must_use]
    pub fn utc_now(&self) -> DateTime<Utc> {
        match &self.backing {
            ClockApiBacking::Native(clock) => clock.borrow().utc_now(),
            ClockApiBacking::Handlers(handlers) => {
                DateTime::from_timestamp_nanos((handlers.timestamp_ns)().as_i64())
            }
        }
    }

    // panics-doc-ok
    /// Sets a time alert delivered through the actor's `on_time_event` callback.
    ///
    /// # Errors
    ///
    /// Returns an error if the alert cannot be scheduled.
    ///
    /// # Panics
    ///
    /// Panics if the clock is already borrowed.
    pub fn set_time_alert(
        &self,
        name: &str,
        alert_time: DateTime<Utc>,
        callback: Option<TimeEventCallback>,
        allow_past: Option<bool>,
    ) -> anyhow::Result<()> {
        match &self.backing {
            ClockApiBacking::Native(clock) => clock
                .borrow_mut()
                .set_time_alert(name, alert_time, callback, allow_past),
            ClockApiBacking::Handlers(handlers) => {
                (handlers.set_time_alert_ns)(name, alert_time.into(), callback, allow_past)
            }
        }
    }

    // panics-doc-ok
    /// Sets a time alert in UNIX nanoseconds delivered through the actor's `on_time_event` callback.
    ///
    /// # Errors
    ///
    /// Returns an error if the alert cannot be scheduled.
    ///
    /// # Panics
    ///
    /// Panics if the clock is already borrowed.
    pub fn set_time_alert_ns(
        &self,
        name: &str,
        alert_time_ns: UnixNanos,
        callback: Option<TimeEventCallback>,
        allow_past: Option<bool>,
    ) -> anyhow::Result<()> {
        match &self.backing {
            ClockApiBacking::Native(clock) => {
                clock
                    .borrow_mut()
                    .set_time_alert_ns(name, alert_time_ns, callback, allow_past)
            }
            ClockApiBacking::Handlers(handlers) => {
                (handlers.set_time_alert_ns)(name, alert_time_ns, callback, allow_past)
            }
        }
    }

    // panics-doc-ok
    /// Sets a timer delivered through the actor's `on_time_event` callback.
    ///
    /// # Errors
    ///
    /// Returns an error if the timer cannot be scheduled.
    ///
    /// # Panics
    ///
    /// Panics if the clock is already borrowed.
    #[expect(clippy::too_many_arguments, reason = "timer scheduling mirrors Clock")]
    pub fn set_timer(
        &self,
        name: &str,
        interval: Duration,
        start_time: Option<DateTime<Utc>>,
        stop_time: Option<DateTime<Utc>>,
        callback: Option<TimeEventCallback>,
        allow_past: Option<bool>,
        fire_immediately: Option<bool>,
    ) -> anyhow::Result<()> {
        match &self.backing {
            ClockApiBacking::Native(clock) => clock.borrow_mut().set_timer(
                name,
                interval,
                start_time,
                stop_time,
                callback,
                allow_past,
                fire_immediately,
            ),
            ClockApiBacking::Handlers(handlers) => (handlers.set_timer_ns)(
                name,
                interval.as_nanos() as u64,
                start_time.map(UnixNanos::from),
                stop_time.map(UnixNanos::from),
                callback,
                allow_past,
                fire_immediately,
            ),
        }
    }

    // panics-doc-ok
    /// Sets a timer in UNIX nanoseconds delivered through the actor's `on_time_event` callback.
    ///
    /// # Errors
    ///
    /// Returns an error if the timer cannot be scheduled.
    ///
    /// # Panics
    ///
    /// Panics if the clock is already borrowed.
    #[expect(clippy::too_many_arguments, reason = "timer scheduling mirrors Clock")]
    pub fn set_timer_ns(
        &self,
        name: &str,
        interval_ns: u64,
        start_time_ns: Option<UnixNanos>,
        stop_time_ns: Option<UnixNanos>,
        callback: Option<TimeEventCallback>,
        allow_past: Option<bool>,
        fire_immediately: Option<bool>,
    ) -> anyhow::Result<()> {
        match &self.backing {
            ClockApiBacking::Native(clock) => clock.borrow_mut().set_timer_ns(
                name,
                interval_ns,
                start_time_ns,
                stop_time_ns,
                callback,
                allow_past,
                fire_immediately,
            ),
            ClockApiBacking::Handlers(handlers) => (handlers.set_timer_ns)(
                name,
                interval_ns,
                start_time_ns,
                stop_time_ns,
                callback,
                allow_past,
                fire_immediately,
            ),
        }
    }

    /// Returns active timer names.
    ///
    /// # Panics
    ///
    /// Panics if the clock is already mutably borrowed.
    #[must_use]
    pub fn timer_names(&self) -> Vec<String> {
        match &self.backing {
            ClockApiBacking::Native(clock) => clock
                .borrow()
                .timer_names()
                .into_iter()
                .map(str::to_string)
                .collect(),
            ClockApiBacking::Handlers(handlers) => (handlers.timer_names)(),
        }
    }

    /// Returns the count of active timers.
    ///
    /// # Panics
    ///
    /// Panics if the clock is already mutably borrowed.
    #[must_use]
    pub fn timer_count(&self) -> usize {
        match &self.backing {
            ClockApiBacking::Native(clock) => clock.borrow().timer_count(),
            ClockApiBacking::Handlers(handlers) => (handlers.timer_count)(),
        }
    }

    /// Returns whether the timer `name` exists.
    ///
    /// # Panics
    ///
    /// Panics if the clock is already mutably borrowed.
    #[must_use]
    pub fn timer_exists(&self, name: &str) -> bool {
        match &self.backing {
            ClockApiBacking::Native(clock) => clock.borrow().timer_exists(&Ustr::from(name)),
            ClockApiBacking::Handlers(handlers) => (handlers.timer_exists)(name),
        }
    }

    /// Returns the next trigger timestamp for the timer `name`.
    ///
    /// # Panics
    ///
    /// Panics if the clock is already mutably borrowed.
    #[must_use]
    pub fn next_time_ns(&self, name: &str) -> Option<UnixNanos> {
        match &self.backing {
            ClockApiBacking::Native(clock) => clock.borrow().next_time_ns(name),
            ClockApiBacking::Handlers(handlers) => (handlers.next_time_ns)(name),
        }
    }

    /// Cancels the timer `name`.
    ///
    /// # Panics
    ///
    /// Panics if the clock is already borrowed.
    pub fn cancel_timer(&self, name: &str) {
        match &self.backing {
            ClockApiBacking::Native(clock) => clock.borrow_mut().cancel_timer(name),
            ClockApiBacking::Handlers(handlers) => (handlers.cancel_timer)(name),
        }
    }

    /// Cancels all timers.
    ///
    /// # Panics
    ///
    /// Panics if the clock is already borrowed.
    pub fn cancel_timers(&self) {
        match &self.backing {
            ClockApiBacking::Native(clock) => clock.borrow_mut().cancel_timers(),
            ClockApiBacking::Handlers(handlers) => (handlers.cancel_timers)(),
        }
    }
}

/// Registry for timer event callbacks.
///
/// Provides shared callback registration and retrieval logic used by both
/// `TestClock` and `LiveClock`.
#[derive(Debug, Default)]
pub struct CallbackRegistry {
    default_callback: Option<TimeEventCallback>,
    callbacks: AHashMap<Ustr, TimeEventCallback>,
}

impl CallbackRegistry {
    /// Creates a new [`CallbackRegistry`] instance.
    #[must_use]
    pub fn new() -> Self {
        Self {
            default_callback: None,
            callbacks: AHashMap::new(),
        }
    }

    /// Registers a default handler callback.
    pub fn register_default_handler(&mut self, callback: TimeEventCallback) {
        self.default_callback = Some(callback);
    }

    /// Cancels the registered default handler callback (if any).
    pub fn cancel_default_handler(&mut self) {
        self.default_callback = None;
    }

    /// Registers a callback for a specific timer name.
    pub fn register_callback(&mut self, name: Ustr, callback: TimeEventCallback) {
        self.callbacks.insert(name, callback);
    }

    /// Returns whether a callback exists for the given name (either specific or default).
    #[must_use]
    pub fn has_any_callback(&self, name: &Ustr) -> bool {
        self.callbacks.contains_key(name) || self.default_callback.is_some()
    }

    /// Gets the callback for a specific timer name, falling back to the default.
    #[must_use]
    pub fn get_callback(&self, name: &Ustr) -> Option<TimeEventCallback> {
        self.callbacks
            .get(name)
            .cloned()
            .or_else(|| self.default_callback.clone())
    }

    /// Gets a handler for a time event.
    ///
    /// # Panics
    ///
    /// Panics if no callback exists for the event name.
    #[must_use]
    pub fn get_handler(&self, event: TimeEvent) -> TimeEventHandler {
        let callback = self
            .get_callback(&event.name)
            .unwrap_or_else(|| panic!("Event '{}' should have associated handler", event.name));

        TimeEventHandler::new(event, callback)
    }

    /// Clears all registered callbacks.
    pub fn clear(&mut self) {
        self.callbacks.clear();
    }
}

/// Validates and prepares parameters for setting a time alert.
///
/// Handles name validation, default value unwrapping, and past timestamp adjustment.
///
/// # Errors
///
/// Returns an error if the name is invalid or if the alert time is in the past when not allowed.
pub fn validate_and_prepare_time_alert(
    name: &str,
    mut alert_time_ns: UnixNanos,
    allow_past: Option<bool>,
    ts_now: UnixNanos,
) -> anyhow::Result<(Ustr, UnixNanos)> {
    check_valid_string_utf8(name, stringify!(name))?;

    let name = Ustr::from(name);
    let allow_past = allow_past.unwrap_or(true);

    if alert_time_ns < ts_now {
        if allow_past {
            alert_time_ns = ts_now;
            log::warn!(
                "Timer '{name}' alert time {} was in the past, adjusted to current time for immediate firing",
                alert_time_ns.to_rfc3339(),
            );
        } else {
            anyhow::bail!(
                "Timer '{name}' alert time {} was in the past (current time is {ts_now})",
                alert_time_ns.to_rfc3339(),
            );
        }
    }

    Ok((name, alert_time_ns))
}

/// Validates and prepares parameters for setting a timer.
///
/// Handles name and interval validation, default value unwrapping, start time normalization,
/// and stop time validation.
///
/// # Errors
///
/// Returns an error if name is invalid, interval is not positive, or stop time validation fails.
pub fn validate_and_prepare_timer(
    name: &str,
    interval_ns: u64,
    start_time_ns: Option<UnixNanos>,
    stop_time_ns: Option<UnixNanos>,
    allow_past: Option<bool>,
    fire_immediately: Option<bool>,
    ts_now: UnixNanos,
) -> anyhow::Result<(Ustr, UnixNanos, Option<UnixNanos>, bool, bool)> {
    check_valid_string_utf8(name, stringify!(name))?;
    check_positive_u64(interval_ns, stringify!(interval_ns))?;

    let name = Ustr::from(name);
    let allow_past = allow_past.unwrap_or(true);
    let fire_immediately = fire_immediately.unwrap_or(false);

    let mut start_time_ns = start_time_ns.unwrap_or_default();

    if start_time_ns == 0 {
        // Zero start time indicates no explicit start; we use the current time
        start_time_ns = ts_now;
    } else if !allow_past {
        let next_event_time = if fire_immediately {
            start_time_ns
        } else {
            start_time_ns + interval_ns
        };

        if next_event_time < ts_now {
            anyhow::bail!(
                "Timer '{name}' next event time {} would be in the past (current time is {ts_now})",
                next_event_time.to_rfc3339(),
            );
        }
    }

    if let Some(stop_time) = stop_time_ns {
        if stop_time <= start_time_ns {
            anyhow::bail!(
                "Timer '{name}' stop time {} must be after start time {}",
                stop_time.to_rfc3339(),
                start_time_ns.to_rfc3339(),
            );
        }

        if !allow_past && stop_time <= ts_now {
            anyhow::bail!(
                "Timer '{name}' stop time {} is in the past (current time is {ts_now})",
                stop_time.to_rfc3339(),
            );
        }
    }

    Ok((
        name,
        start_time_ns,
        stop_time_ns,
        allow_past,
        fire_immediately,
    ))
}

/// A static test clock.
///
/// Stores the current timestamp internally which can be advanced.
///
/// # Threading
///
/// This clock is thread-affine; use it only from the thread that created it.
#[derive(Debug)]
pub struct TestClock {
    time: AtomicTime,
    timers: BTreeMap<Ustr, TestTimer>,
    timer_queue: BinaryHeap<ScheduledTimeEvent>,
    callbacks: CallbackRegistry,
}

impl TestClock {
    /// Creates a new [`TestClock`] instance.
    #[must_use]
    pub fn new() -> Self {
        Self {
            time: AtomicTime::new(false, UnixNanos::default()),
            timers: BTreeMap::new(),
            timer_queue: BinaryHeap::new(),
            callbacks: CallbackRegistry::new(),
        }
    }

    /// Returns a reference to the internal timers for the clock.
    #[must_use]
    pub const fn get_timers(&self) -> &BTreeMap<Ustr, TestTimer> {
        &self.timers
    }

    /// Advances the internal clock to the specified `to_time_ns` and optionally sets the clock to that time.
    ///
    /// This function ensures that the clock behaves in a non-decreasing manner. If `set_time` is `true`,
    /// the internal clock will be updated to the value of `to_time_ns`. Otherwise, the clock will advance
    /// without explicitly setting the time.
    ///
    /// The method processes active timers, advancing them to `to_time_ns`, and collects any `TimeEvent`
    /// objects that are triggered as a result. Only timers that are not expired are processed.
    ///
    /// # Warnings
    ///
    /// Logs a warning if >= 1,000,000 time events are allocated during advancement.
    ///
    /// # Panics
    ///
    /// Panics if `to_time_ns` is less than the current internal clock time.
    pub fn advance_time(&mut self, to_time_ns: UnixNanos, set_time: bool) -> Vec<TimeEvent> {
        const WARN_TIME_EVENTS_THRESHOLD: usize = 1_000_000;

        let from_time_ns = self.time.get_time_ns();

        assert!(
            to_time_ns >= from_time_ns,
            "Invariant: time must be non-decreasing, `to_time_ns` {to_time_ns} < `from_time_ns` {from_time_ns}"
        );

        if set_time {
            self.time.set_time(to_time_ns);
        }

        let mut events: Vec<TimeEvent> = Vec::new();

        while self
            .timer_queue
            .peek()
            .is_some_and(|entry| entry.0.ts_event <= to_time_ns)
        {
            let entry = self
                .timer_queue
                .pop()
                .expect("timer queue peeked Some but pop returned None");

            let Some((event, next_event)) = self.advance_timer_from_entry(&entry.0) else {
                continue;
            };

            events.push(event);
            if let Some(next_event) = next_event {
                self.timer_queue.push(next_event);
            }
        }

        self.compact_timer_queue_if_needed();

        if events.len() >= WARN_TIME_EVENTS_THRESHOLD {
            log::warn!(
                "Allocated {} time events during clock advancement from {} to {}, \
                 consider stopping the timer between large time ranges with no data points",
                events.len().separate_with_commas(),
                from_time_ns,
                to_time_ns
            );
        }

        events.sort_by(|a, b| {
            a.ts_event
                .cmp(&b.ts_event)
                .then_with(|| a.name.cmp(&b.name))
        });
        events
    }

    /// Matches `TimeEvent` objects with their corresponding event handlers.
    ///
    /// This function takes an `events` vector of `TimeEvent` objects, assumes they are already sorted
    /// by their `ts_event`, and matches them with the appropriate callback handler from the internal
    /// registry of callbacks. If no specific callback is found for an event, the default callback is used.
    ///
    /// # Panics
    ///
    /// Panics if the default callback is not set for the clock when matching handlers.
    #[must_use]
    pub fn match_handlers(&self, events: Vec<TimeEvent>) -> Vec<TimeEventHandler> {
        events
            .into_iter()
            .map(|event| self.callbacks.get_handler(event))
            .collect()
    }

    fn replace_existing_timer_if_needed(&mut self, name: &Ustr) {
        replace_existing_timer(&mut self.timers, name);
        self.compact_timer_queue_if_needed();
    }

    fn insert_timer(&mut self, timer: TestTimer) {
        self.timer_queue.push(Self::scheduled_event(&timer));
        self.timers.insert(timer.name, timer);
        self.compact_timer_queue_if_needed();
    }

    fn advance_timer_from_entry(
        &mut self,
        entry: &TimeEvent,
    ) -> Option<(TimeEvent, Option<ScheduledTimeEvent>)> {
        let timer = self.timers.get_mut(&entry.name)?;
        if timer.next_time_ns() != entry.ts_event {
            return None;
        }

        let Some((event, _)) = timer.next() else {
            self.timers.remove(&entry.name);
            return None;
        };

        let next_entry = if timer.is_expired() {
            self.timers.remove(&entry.name);
            None
        } else {
            Some(Self::scheduled_event(timer))
        };

        Some((event, next_entry))
    }

    fn compact_timer_queue_if_needed(&mut self) {
        if self.timer_queue.len() > self.timers.len().saturating_mul(2) {
            self.compact_timer_queue();
        }
    }

    fn compact_timer_queue(&mut self) {
        self.timer_queue = self.timers.values().map(Self::scheduled_event).collect();
    }

    fn scheduled_event(timer: &TestTimer) -> ScheduledTimeEvent {
        ScheduledTimeEvent::new(TimeEvent::new(
            timer.name,
            UUID4::new(),
            timer.next_time_ns(),
            timer.next_time_ns(),
        ))
    }
}

impl Default for TestClock {
    /// Creates a new default [`TestClock`] instance.
    fn default() -> Self {
        Self::new()
    }
}

impl Deref for TestClock {
    type Target = AtomicTime;

    fn deref(&self) -> &Self::Target {
        &self.time
    }
}

impl Clock for TestClock {
    fn timestamp_ns(&self) -> UnixNanos {
        self.time.get_time_ns()
    }

    fn timestamp_us(&self) -> u64 {
        self.time.get_time_us()
    }

    fn timestamp_ms(&self) -> u64 {
        self.time.get_time_ms()
    }

    fn timestamp(&self) -> f64 {
        self.time.get_time()
    }

    fn timer_names(&self) -> Vec<&str> {
        self.timers
            .iter()
            .filter(|(_, timer)| !timer.is_expired())
            .map(|(k, _)| k.as_str())
            .collect()
    }

    fn timer_count(&self) -> usize {
        self.timers
            .iter()
            .filter(|(_, timer)| !timer.is_expired())
            .count()
    }

    fn timer_exists(&self, name: &Ustr) -> bool {
        self.timers.contains_key(name)
    }

    fn register_default_handler(&mut self, callback: TimeEventCallback) {
        self.callbacks.register_default_handler(callback);
    }

    fn cancel_default_handler(&mut self) {
        self.callbacks.cancel_default_handler();
    }

    fn cancel_callbacks(&mut self) {
        self.callbacks.clear();
    }

    /// Returns the handler for the given `TimeEvent`.
    ///
    /// # Panics
    ///
    /// Panics if no event-specific or default callback has been registered for the event.
    fn get_handler(&self, event: TimeEvent) -> TimeEventHandler {
        self.callbacks.get_handler(event)
    }

    fn set_time_alert_ns(
        &mut self,
        name: &str,
        alert_time_ns: UnixNanos,
        callback: Option<TimeEventCallback>,
        allow_past: Option<bool>,
    ) -> anyhow::Result<()> {
        let ts_now = self.get_time_ns();
        let (name, alert_time_ns) =
            validate_and_prepare_time_alert(name, alert_time_ns, allow_past, ts_now)?;

        self.replace_existing_timer_if_needed(&name);

        check_predicate_true(
            callback.is_some() | self.callbacks.has_any_callback(&name),
            "No callbacks provided",
        )?;

        if let Some(callback) = callback {
            self.callbacks.register_callback(name, callback);
        }

        // Safe to calculate interval now that we've ensured alert_time_ns >= ts_now
        let interval_ns = create_valid_interval((alert_time_ns - ts_now).into());
        let fire_immediately = alert_time_ns == ts_now;

        let timer = TestTimer::new(
            name,
            interval_ns,
            ts_now,
            Some(alert_time_ns),
            fire_immediately,
        );
        self.insert_timer(timer);

        Ok(())
    }

    fn set_timer_ns(
        &mut self,
        name: &str,
        interval_ns: u64,
        start_time_ns: Option<UnixNanos>,
        stop_time_ns: Option<UnixNanos>,
        callback: Option<TimeEventCallback>,
        allow_past: Option<bool>,
        fire_immediately: Option<bool>,
    ) -> anyhow::Result<()> {
        let ts_now = self.get_time_ns();
        let (name, start_time_ns, stop_time_ns, _allow_past, fire_immediately) =
            validate_and_prepare_timer(
                name,
                interval_ns,
                start_time_ns,
                stop_time_ns,
                allow_past,
                fire_immediately,
                ts_now,
            )?;

        check_predicate_true(
            callback.is_some() | self.callbacks.has_any_callback(&name),
            "No callbacks provided",
        )?;

        self.replace_existing_timer_if_needed(&name);

        if let Some(callback) = callback {
            self.callbacks.register_callback(name, callback);
        }

        let interval_ns = create_valid_interval(interval_ns);

        let timer = TestTimer::new(
            name,
            interval_ns,
            start_time_ns,
            stop_time_ns,
            fire_immediately,
        );
        self.insert_timer(timer);

        Ok(())
    }

    fn next_time_ns(&self, name: &str) -> Option<UnixNanos> {
        self.timers
            .get(&Ustr::from(name))
            .map(TestTimer::next_time_ns)
    }

    fn cancel_timer(&mut self, name: &str) {
        let timer = self.timers.remove(&Ustr::from(name));
        if let Some(mut timer) = timer {
            timer.cancel();
        }
        self.compact_timer_queue_if_needed();
    }

    fn cancel_timers(&mut self) {
        for timer in &mut self.timers.values_mut() {
            timer.cancel();
        }

        self.timers.clear();
        self.timer_queue.clear();
    }

    fn reset(&mut self) {
        self.time = AtomicTime::new(false, UnixNanos::default());
        self.timers = BTreeMap::new();
        self.timer_queue = BinaryHeap::new();
        self.callbacks.clear();
    }
}

pub(crate) fn replace_existing_timer<T: Timer>(timers: &mut BTreeMap<Ustr, T>, name: &Ustr) {
    let is_expired = timers.get(name).map(T::is_expired);
    match is_expired {
        Some(true) => {
            timers.remove(name);
        }
        Some(false) => {
            if let Some(mut timer) = timers.remove(name) {
                timer.cancel();
            }
            log::warn!("Timer '{name}' replaced");
        }
        None => {}
    }
}

#[cfg(test)]
mod tests {
    use std::{
        cell::RefCell,
        sync::{Arc, Mutex},
        time::Duration,
    };

    use nautilus_core::{MUTEX_POISONED, UnixNanos};
    use rstest::{fixture, rstest};
    use ustr::Ustr;

    use super::*;
    use crate::timer::{TimeEvent, TimeEventCallback};

    #[derive(Debug, Default)]
    struct TestCallback {
        /// Shared flag updated from within the timer callback; Mutex keeps the closure `Send` for tests.
        called: Arc<Mutex<bool>>,
    }

    impl TestCallback {
        fn new(called: Arc<Mutex<bool>>) -> Self {
            Self { called }
        }
    }

    impl From<TestCallback> for TimeEventCallback {
        fn from(callback: TestCallback) -> Self {
            Self::from(move |_event: TimeEvent| {
                if let Ok(mut called) = callback.called.lock() {
                    *called = true;
                }
            })
        }
    }

    #[fixture]
    pub fn test_clock() -> TestClock {
        let mut clock = TestClock::new();
        clock.register_default_handler(TestCallback::default().into());
        clock
    }

    #[rstest]
    fn test_time_monotonicity(mut test_clock: TestClock) {
        let initial_time = test_clock.timestamp_ns();
        test_clock.advance_time(UnixNanos::from(*initial_time + 1000), true);
        assert!(test_clock.timestamp_ns() > initial_time);
    }

    #[rstest]
    fn test_timer_registration(mut test_clock: TestClock) {
        test_clock
            .set_time_alert_ns(
                "test_timer",
                (*test_clock.timestamp_ns() + 1000).into(),
                None,
                None,
            )
            .unwrap();
        assert_eq!(test_clock.timer_count(), 1);
        assert_eq!(test_clock.timer_names(), vec!["test_timer"]);
    }

    #[rstest]
    fn test_timer_expiration(mut test_clock: TestClock) {
        let alert_time = (*test_clock.timestamp_ns() + 1000).into();
        test_clock
            .set_time_alert_ns("test_timer", alert_time, None, None)
            .unwrap();
        let events = test_clock.advance_time(alert_time, true);
        assert_eq!(events.len(), 1);
        assert_eq!(events[0].name.as_str(), "test_timer");
    }

    #[rstest]
    fn test_timer_cancellation(mut test_clock: TestClock) {
        test_clock
            .set_time_alert_ns(
                "test_timer",
                (*test_clock.timestamp_ns() + 1000).into(),
                None,
                None,
            )
            .unwrap();
        assert_eq!(test_clock.timer_count(), 1);
        test_clock.cancel_timer("test_timer");
        assert_eq!(test_clock.timer_count(), 0);
    }

    #[rstest]
    fn test_time_advancement(mut test_clock: TestClock) {
        let start_time = test_clock.timestamp_ns();
        test_clock
            .set_timer_ns("test_timer", 1000, Some(start_time), None, None, None, None)
            .unwrap();
        let events = test_clock.advance_time(UnixNanos::from(*start_time + 2500), true);
        assert_eq!(events.len(), 2);
        assert_eq!(*events[0].ts_event, *start_time + 1000);
        assert_eq!(*events[1].ts_event, *start_time + 2000);
    }

    #[rstest]
    fn test_default_and_custom_callbacks() {
        let mut clock = TestClock::new();
        let default_called = Arc::new(Mutex::new(false));
        let custom_called = Arc::new(Mutex::new(false));

        let default_callback = TestCallback::new(Arc::clone(&default_called));
        let custom_callback = TestCallback::new(Arc::clone(&custom_called));

        clock.register_default_handler(TimeEventCallback::from(default_callback));
        clock
            .set_time_alert_ns(
                "default_timer",
                (*clock.timestamp_ns() + 1000).into(),
                None,
                None,
            )
            .unwrap();
        clock
            .set_time_alert_ns(
                "custom_timer",
                (*clock.timestamp_ns() + 1000).into(),
                Some(TimeEventCallback::from(custom_callback)),
                None,
            )
            .unwrap();

        let events = clock.advance_time(UnixNanos::from(*clock.timestamp_ns() + 1000), true);
        let handlers = clock.match_handlers(events);

        for handler in handlers {
            handler.callback.call(handler.event);
        }

        assert!(*default_called.lock().expect(MUTEX_POISONED));
        assert!(*custom_called.lock().expect(MUTEX_POISONED));
    }

    #[rstest]
    fn test_timer_with_rust_local_callback() {
        use std::{cell::RefCell, rc::Rc};

        let mut clock = TestClock::new();
        let call_count = Rc::new(RefCell::new(0_u32));
        let call_count_clone = Rc::clone(&call_count);

        // Create RustLocal callback using Rc (not Send/Sync)
        let callback: Rc<dyn Fn(TimeEvent)> = Rc::new(move |_event: TimeEvent| {
            *call_count_clone.borrow_mut() += 1;
        });

        clock
            .set_time_alert_ns(
                "local_timer",
                (*clock.timestamp_ns() + 1000).into(),
                Some(TimeEventCallback::from(callback)),
                None,
            )
            .unwrap();

        let events = clock.advance_time(UnixNanos::from(*clock.timestamp_ns() + 1000), true);
        let handlers = clock.match_handlers(events);

        for handler in handlers {
            handler.callback.call(handler.event);
        }

        assert_eq!(*call_count.borrow(), 1);
    }

    #[rstest]
    fn test_multiple_timers(mut test_clock: TestClock) {
        let start_time = test_clock.timestamp_ns();
        test_clock
            .set_timer_ns("timer1", 1000, Some(start_time), None, None, None, None)
            .unwrap();
        test_clock
            .set_timer_ns("timer2", 2000, Some(start_time), None, None, None, None)
            .unwrap();
        let events = test_clock.advance_time(UnixNanos::from(*start_time + 2000), true);
        assert_eq!(events.len(), 3);
        assert_eq!(events[0].name.as_str(), "timer1");
        assert_eq!(events[1].name.as_str(), "timer1");
        assert_eq!(events[2].name.as_str(), "timer2");
    }

    #[rstest]
    fn test_allow_past_parameter_true(mut test_clock: TestClock) {
        test_clock.set_time(UnixNanos::from(2000));
        let current_time = test_clock.timestamp_ns();
        let past_time = UnixNanos::from(current_time.as_u64() - 1000);

        // With allow_past=true (default), should adjust to current time and succeed
        test_clock
            .set_time_alert_ns("past_timer", past_time, None, Some(true))
            .unwrap();

        // Verify timer was created with adjusted time
        assert_eq!(test_clock.timer_count(), 1);
        assert_eq!(test_clock.timer_names(), vec!["past_timer"]);

        // Next time should be at or after current time, not in the past
        let next_time = test_clock.next_time_ns("past_timer").unwrap();
        assert!(next_time >= current_time);
    }

    #[rstest]
    fn test_allow_past_parameter_false(mut test_clock: TestClock) {
        test_clock.set_time(UnixNanos::from(2000));
        let current_time = test_clock.timestamp_ns();
        let past_time = current_time - 1000;

        // With allow_past=false, should fail for past times
        let result = test_clock.set_time_alert_ns("past_timer", past_time, None, Some(false));

        // Verify the operation failed with appropriate error
        assert!(result.is_err());
        assert!(format!("{}", result.unwrap_err()).contains("was in the past"));

        // Verify no timer was created
        assert_eq!(test_clock.timer_count(), 0);
        assert!(test_clock.timer_names().is_empty());
    }

    #[rstest]
    fn test_invalid_stop_time_validation(mut test_clock: TestClock) {
        test_clock.set_time(UnixNanos::from(2000));
        let current_time = test_clock.timestamp_ns();
        let start_time = current_time + 1000;
        let stop_time = current_time + 500; // Stop time before start time

        // Should fail because stop_time < start_time
        let result = test_clock.set_timer_ns(
            "invalid_timer",
            100,
            Some(start_time),
            Some(stop_time),
            None,
            None,
            None,
        );

        // Verify the operation failed with appropriate error
        assert!(result.is_err());
        assert!(format!("{}", result.unwrap_err()).contains("must be after start time"));

        // Verify no timer was created
        assert_eq!(test_clock.timer_count(), 0);
    }

    #[rstest]
    fn test_set_timer_ns_fire_immediately_true(mut test_clock: TestClock) {
        let start_time = test_clock.timestamp_ns();
        let interval_ns = 1000;

        test_clock
            .set_timer_ns(
                "fire_immediately_timer",
                interval_ns,
                Some(start_time),
                None,
                None,
                None,
                Some(true),
            )
            .unwrap();

        // Advance time to check immediate firing and subsequent intervals
        let events = test_clock.advance_time(start_time + 2500, true);

        // Should fire immediately at start_time (0), then at start_time+1000, then at start_time+2000
        assert_eq!(events.len(), 3);
        assert_eq!(*events[0].ts_event, *start_time); // Fires immediately
        assert_eq!(*events[1].ts_event, *start_time + 1000); // Then after interval
        assert_eq!(*events[2].ts_event, *start_time + 2000); // Then after second interval
    }

    #[rstest]
    fn test_set_timer_ns_fire_immediately_false(mut test_clock: TestClock) {
        let start_time = test_clock.timestamp_ns();
        let interval_ns = 1000;

        test_clock
            .set_timer_ns(
                "normal_timer",
                interval_ns,
                Some(start_time),
                None,
                None,
                None,
                Some(false),
            )
            .unwrap();

        // Advance time to check normal behavior
        let events = test_clock.advance_time(start_time + 2500, true);

        // Should fire after first interval, not immediately
        assert_eq!(events.len(), 2);
        assert_eq!(*events[0].ts_event, *start_time + 1000); // Fires after first interval
        assert_eq!(*events[1].ts_event, *start_time + 2000); // Then after second interval
    }

    #[rstest]
    fn test_set_timer_ns_fire_immediately_default_is_false(mut test_clock: TestClock) {
        let start_time = test_clock.timestamp_ns();
        let interval_ns = 1000;

        // Don't specify fire_immediately (should default to false)
        test_clock
            .set_timer_ns(
                "default_timer",
                interval_ns,
                Some(start_time),
                None,
                None,
                None,
                None,
            )
            .unwrap();

        let events = test_clock.advance_time(start_time + 1500, true);

        // Should behave the same as fire_immediately=false
        assert_eq!(events.len(), 1);
        assert_eq!(*events[0].ts_event, *start_time + 1000); // Fires after first interval
    }

    #[rstest]
    fn test_set_timer_ns_fire_immediately_with_zero_start_time(mut test_clock: TestClock) {
        test_clock.set_time(5000.into());
        let interval_ns = 1000;

        test_clock
            .set_timer_ns(
                "zero_start_timer",
                interval_ns,
                None,
                None,
                None,
                None,
                Some(true),
            )
            .unwrap();

        let events = test_clock.advance_time(UnixNanos::from(7000), true);

        // With zero start time, should use current time as start
        // Fire immediately at current time (5000), then at 6000, 7000
        assert_eq!(events.len(), 3);
        assert_eq!(*events[0].ts_event, 5000); // Immediate fire at current time
        assert_eq!(*events[1].ts_event, 6000);
        assert_eq!(*events[2].ts_event, 7000);
    }

    #[rstest]
    fn test_multiple_timers_different_fire_immediately_settings(mut test_clock: TestClock) {
        let start_time = test_clock.timestamp_ns();
        let interval_ns = 1000;

        // One timer with fire_immediately=true
        test_clock
            .set_timer_ns(
                "immediate_timer",
                interval_ns,
                Some(start_time),
                None,
                None,
                None,
                Some(true),
            )
            .unwrap();

        // One timer with fire_immediately=false
        test_clock
            .set_timer_ns(
                "normal_timer",
                interval_ns,
                Some(start_time),
                None,
                None,
                None,
                Some(false),
            )
            .unwrap();

        let events = test_clock.advance_time(start_time + 1500, true);

        // Should have 3 events total: immediate_timer fires at start & 1000, normal_timer fires at 1000
        assert_eq!(events.len(), 3);

        // Sort events by timestamp to check order
        let mut event_times: Vec<u64> = events.iter().map(|e| e.ts_event.as_u64()).collect();
        event_times.sort_unstable();

        assert_eq!(event_times[0], start_time.as_u64()); // immediate_timer fires immediately
        assert_eq!(event_times[1], start_time.as_u64() + 1000); // both timers fire at 1000
        assert_eq!(event_times[2], start_time.as_u64() + 1000); // both timers fire at 1000
    }

    #[rstest]
    fn test_timer_name_collision_overwrites(mut test_clock: TestClock) {
        let start_time = test_clock.timestamp_ns();

        // Set first timer
        test_clock
            .set_timer_ns(
                "collision_timer",
                1000,
                Some(start_time),
                None,
                None,
                None,
                None,
            )
            .unwrap();

        // Setting timer with same name should overwrite the existing one
        let result = test_clock.set_timer_ns(
            "collision_timer",
            2000,
            Some(start_time),
            None,
            None,
            None,
            None,
        );

        assert!(result.is_ok());
        // Should still only have one timer (overwritten)
        assert_eq!(test_clock.timer_count(), 1);

        // The timer should have the new interval
        let next_time = test_clock.next_time_ns("collision_timer").unwrap();
        // With interval 2000 and start at start_time, next time should be start_time + 2000
        assert_eq!(next_time, start_time + 2000);
    }

    #[rstest]
    fn test_timer_zero_interval_error(mut test_clock: TestClock) {
        let start_time = test_clock.timestamp_ns();

        // Attempt to set timer with zero interval should fail
        let result =
            test_clock.set_timer_ns("zero_interval", 0, Some(start_time), None, None, None, None);

        assert!(result.is_err());
        assert_eq!(test_clock.timer_count(), 0);
    }

    #[rstest]
    fn test_timer_empty_name_error(mut test_clock: TestClock) {
        let start_time = test_clock.timestamp_ns();

        // Attempt to set timer with empty name should fail
        let result = test_clock.set_timer_ns("", 1000, Some(start_time), None, None, None, None);

        assert!(result.is_err());
        assert_eq!(test_clock.timer_count(), 0);
    }

    #[rstest]
    fn test_timer_exists(mut test_clock: TestClock) {
        let name = Ustr::from("exists_timer");
        assert!(!test_clock.timer_exists(&name));

        test_clock
            .set_time_alert_ns(
                name.as_str(),
                (*test_clock.timestamp_ns() + 1_000).into(),
                None,
                None,
            )
            .unwrap();

        assert!(test_clock.timer_exists(&name));
    }

    #[rstest]
    fn test_timer_rejects_past_stop_time_when_not_allowed(mut test_clock: TestClock) {
        test_clock.set_time(UnixNanos::from(10_000));
        let current = test_clock.timestamp_ns();

        let result = test_clock.set_timer_ns(
            "past_stop",
            10_000,
            Some(current - 500),
            Some(current - 100),
            None,
            Some(false),
            None,
        );

        let err = result.expect_err("expected stop time validation error");
        let err_msg = err.to_string();
        assert!(err_msg.contains("stop time"));
        assert!(err_msg.contains("in the past"));
    }

    #[rstest]
    fn test_timer_accepts_future_stop_time(mut test_clock: TestClock) {
        let current = test_clock.timestamp_ns();

        let result = test_clock.set_timer_ns(
            "future_stop",
            1_000,
            Some(current),
            Some(current + 10_000),
            None,
            Some(false),
            None,
        );

        assert!(result.is_ok());
    }

    #[rstest]
    fn test_timer_fire_immediately_at_exact_stop_time(mut test_clock: TestClock) {
        let start_time = test_clock.timestamp_ns();
        let interval_ns = 1000;
        let stop_time = start_time + interval_ns; // Stop exactly at first interval

        test_clock
            .set_timer_ns(
                "exact_stop",
                interval_ns,
                Some(start_time),
                Some(stop_time),
                None,
                None,
                Some(true),
            )
            .unwrap();

        let events = test_clock.advance_time(stop_time, true);

        // Should fire immediately at start, then at stop time (which equals first interval)
        assert_eq!(events.len(), 2);
        assert_eq!(*events[0].ts_event, *start_time); // Immediate fire
        assert_eq!(*events[1].ts_event, *stop_time); // Fire at stop time
    }

    #[rstest]
    fn test_timer_advance_to_exact_next_time(mut test_clock: TestClock) {
        let start_time = test_clock.timestamp_ns();
        let interval_ns = 1000;

        test_clock
            .set_timer_ns(
                "exact_advance",
                interval_ns,
                Some(start_time),
                None,
                None,
                None,
                Some(false),
            )
            .unwrap();

        // Advance to exactly the next fire time
        let next_time = test_clock.next_time_ns("exact_advance").unwrap();
        let events = test_clock.advance_time(next_time, true);

        assert_eq!(events.len(), 1);
        assert_eq!(*events[0].ts_event, *next_time);
    }

    #[rstest]
    fn test_allow_past_bar_aggregation_use_case(mut test_clock: TestClock) {
        // Simulate bar aggregation scenario: current time is in middle of a bar window
        test_clock.set_time(UnixNanos::from(100_500)); // 100.5 seconds

        let bar_start_time = UnixNanos::from(100_000); // 100 seconds (0.5 sec ago)
        let interval_ns = 1000; // 1 second bars

        // With allow_past=false and fire_immediately=false:
        // start_time is in past (100 sec) but next event (101 sec) is in future
        // This should be ALLOWED for bar aggregation
        let result = test_clock.set_timer_ns(
            "bar_timer",
            interval_ns,
            Some(bar_start_time),
            None,
            None,
            Some(false), // allow_past = false
            Some(false), // fire_immediately = false
        );

        // Should succeed because next event time (100_000 + 1000 = 101_000) > current time (100_500)
        assert!(result.is_ok());
        assert_eq!(test_clock.timer_count(), 1);

        // Next event should be at bar_start_time + interval = 101_000
        let next_time = test_clock.next_time_ns("bar_timer").unwrap();
        assert_eq!(*next_time, 101_000);
    }

    #[rstest]
    fn test_allow_past_false_rejects_when_next_event_in_past(mut test_clock: TestClock) {
        test_clock.set_time(UnixNanos::from(102_000)); // 102 seconds

        let past_start_time = UnixNanos::from(100_000); // 100 seconds (2 sec ago)
        let interval_ns = 1000; // 1 second interval

        // With allow_past=false and fire_immediately=false:
        // Next event would be 100_000 + 1000 = 101_000, which is < current time (102_000)
        // This should be REJECTED
        let result = test_clock.set_timer_ns(
            "past_event_timer",
            interval_ns,
            Some(past_start_time),
            None,
            None,
            Some(false), // allow_past = false
            Some(false), // fire_immediately = false
        );

        // Should fail because next event time (101_000) < current time (102_000)
        assert!(result.is_err());
        assert!(
            result
                .unwrap_err()
                .to_string()
                .contains("would be in the past")
        );
    }

    #[rstest]
    fn test_allow_past_false_with_fire_immediately_true(mut test_clock: TestClock) {
        test_clock.set_time(UnixNanos::from(100_500)); // 100.5 seconds

        let past_start_time = UnixNanos::from(100_000); // 100 seconds (0.5 sec ago)
        let interval_ns = 1000;

        // With fire_immediately=true, next event = start_time (which is in past)
        // This should be REJECTED with allow_past=false
        let result = test_clock.set_timer_ns(
            "immediate_past_timer",
            interval_ns,
            Some(past_start_time),
            None,
            None,
            Some(false), // allow_past = false
            Some(true),  // fire_immediately = true
        );

        // Should fail because next event time (100_000) < current time (100_500)
        assert!(result.is_err());
        assert!(
            result
                .unwrap_err()
                .to_string()
                .contains("would be in the past")
        );
    }

    #[rstest]
    fn test_cancel_timer_during_execution(mut test_clock: TestClock) {
        let start_time = test_clock.timestamp_ns();

        test_clock
            .set_timer_ns(
                "cancel_test",
                1000,
                Some(start_time),
                None,
                None,
                None,
                None,
            )
            .unwrap();

        assert_eq!(test_clock.timer_count(), 1);

        // Cancel the timer
        test_clock.cancel_timer("cancel_test");

        assert_eq!(test_clock.timer_count(), 0);

        // Advance time - should get no events from cancelled timer
        let events = test_clock.advance_time(start_time + 2000, true);
        assert_eq!(events.len(), 0);
    }

    #[rstest]
    fn test_cancelled_timer_queue_entry_is_skipped(mut test_clock: TestClock) {
        let start_time = test_clock.timestamp_ns();
        test_clock
            .set_time_alert_ns("cancelled", start_time + 1000, None, None)
            .unwrap();
        test_clock
            .set_time_alert_ns("active", start_time + 2000, None, None)
            .unwrap();

        test_clock.cancel_timer("cancelled");
        assert_eq!(test_clock.timer_count(), 1);
        assert_eq!(test_clock.timer_queue.len(), 2);

        let events = test_clock.advance_time(start_time + 1000, true);
        assert!(events.is_empty());
        assert_eq!(test_clock.timer_names(), vec!["active"]);

        let events = test_clock.advance_time(start_time + 2000, true);
        assert_eq!(events.len(), 1);
        assert_eq!(events[0].name.as_str(), "active");
    }

    #[rstest]
    fn test_timer_queue_compacts_stale_entries(mut test_clock: TestClock) {
        let start_time = test_clock.timestamp_ns();
        test_clock
            .set_time_alert_ns("active", start_time + 1000, None, None)
            .unwrap();
        test_clock
            .set_time_alert_ns("cancelled-1", start_time + 2000, None, None)
            .unwrap();
        test_clock
            .set_time_alert_ns("cancelled-2", start_time + 3000, None, None)
            .unwrap();

        test_clock.cancel_timer("cancelled-1");
        assert_eq!(test_clock.timer_queue.len(), 3);

        test_clock.cancel_timer("cancelled-2");
        assert_eq!(test_clock.timer_count(), 1);
        assert_eq!(test_clock.timer_queue.len(), 1);
    }

    #[rstest]
    fn test_cancel_all_timers(mut test_clock: TestClock) {
        // Create multiple timers
        test_clock
            .set_timer_ns("timer1", 1000, None, None, None, None, None)
            .unwrap();
        test_clock
            .set_timer_ns("timer2", 1500, None, None, None, None, None)
            .unwrap();
        test_clock
            .set_timer_ns("timer3", 2000, None, None, None, None, None)
            .unwrap();

        assert_eq!(test_clock.timer_count(), 3);

        // Cancel all timers
        test_clock.cancel_timers();

        assert_eq!(test_clock.timer_count(), 0);

        // Advance time - should get no events
        let events = test_clock.advance_time(UnixNanos::from(5000), true);
        assert_eq!(events.len(), 0);
    }

    #[rstest]
    fn test_clock_reset_clears_timers(mut test_clock: TestClock) {
        test_clock
            .set_timer_ns("reset_test", 1000, None, None, None, None, None)
            .unwrap();

        assert_eq!(test_clock.timer_count(), 1);

        // Reset the clock
        test_clock.reset();

        assert_eq!(test_clock.timer_count(), 0);
        assert_eq!(test_clock.timestamp_ns(), UnixNanos::default()); // Time reset to zero
    }

    #[rstest]
    fn test_cancel_default_handler_clears_default(mut test_clock: TestClock) {
        // Default handler is registered by the fixture
        test_clock.cancel_default_handler();

        // Without a default and without an explicit callback, scheduling fails
        let alert_time: UnixNanos = (*test_clock.timestamp_ns() + 1000).into();
        let err = test_clock
            .set_time_alert_ns("alert", alert_time, None, None)
            .unwrap_err();
        assert!(
            err.to_string().contains("No callbacks provided"),
            "unexpected error: {err}"
        );
    }

    #[rstest]
    fn test_cancel_default_handler_is_idempotent_on_empty_registry() {
        // Fresh clock with no handler registered: cancel must not panic
        let mut clock = TestClock::new();
        clock.cancel_default_handler();
        clock.cancel_default_handler();
    }

    #[rstest]
    fn test_cancel_callbacks_clears_named(mut test_clock: TestClock) {
        let alert_time: UnixNanos = (*test_clock.timestamp_ns() + 1000).into();
        let callback = TimeEventCallback::from(TestCallback::default());
        test_clock
            .set_time_alert_ns("named_alert", alert_time, Some(callback), None)
            .unwrap();
        test_clock.cancel_timer("named_alert");

        // Cancel both default and named callbacks; rescheduling without a callback fails
        test_clock.cancel_default_handler();
        test_clock.cancel_callbacks();

        let err = test_clock
            .set_time_alert_ns("named_alert", alert_time, None, None)
            .unwrap_err();
        assert!(
            err.to_string().contains("No callbacks provided"),
            "unexpected error: {err}"
        );
    }

    #[rstest]
    fn test_cancel_default_handler_preserves_named_callbacks(mut test_clock: TestClock) {
        let alert_time: UnixNanos = (*test_clock.timestamp_ns() + 1000).into();
        let callback = TimeEventCallback::from(TestCallback::default());
        test_clock
            .set_time_alert_ns("alert", alert_time, Some(callback), None)
            .unwrap();
        test_clock.cancel_timer("alert");

        test_clock.cancel_default_handler();

        // Named callback survives: rescheduling under the same name without a callback works
        test_clock
            .set_time_alert_ns("alert", alert_time, None, None)
            .unwrap();
    }

    #[rstest]
    fn test_cancel_callbacks_preserves_default_handler(mut test_clock: TestClock) {
        // Default handler from fixture remains available
        test_clock.cancel_callbacks();

        let alert_time: UnixNanos = (*test_clock.timestamp_ns() + 1000).into();
        test_clock
            .set_time_alert_ns("alert", alert_time, None, None)
            .unwrap();
    }

    #[rstest]
    fn test_set_time_alert_default_impl(mut test_clock: TestClock) {
        let current_time = test_clock.utc_now();
        let alert_time = current_time + chrono::Duration::seconds(1);

        // Test the default implementation that delegates to set_time_alert_ns
        test_clock
            .set_time_alert("alert_test", alert_time, None, None)
            .unwrap();

        assert_eq!(test_clock.timer_count(), 1);
        assert_eq!(test_clock.timer_names(), vec!["alert_test"]);

        // Verify the timer is set for the correct time
        let expected_ns = UnixNanos::from(alert_time);
        let next_time = test_clock.next_time_ns("alert_test").unwrap();

        // Should be very close (within a few nanoseconds due to conversion)
        let diff = if next_time >= expected_ns {
            next_time.as_u64() - expected_ns.as_u64()
        } else {
            expected_ns.as_u64() - next_time.as_u64()
        };
        assert!(
            diff < 1000,
            "Timer should be set within 1 microsecond of expected time"
        );
    }

    #[rstest]
    fn test_set_timer_default_impl(mut test_clock: TestClock) {
        let current_time = test_clock.utc_now();
        let start_time = current_time + chrono::Duration::seconds(1);
        let interval = Duration::from_millis(500);

        // Test the default implementation that delegates to set_timer_ns
        test_clock
            .set_timer(
                "timer_test",
                interval,
                Some(start_time),
                None,
                None,
                None,
                None,
            )
            .unwrap();

        assert_eq!(test_clock.timer_count(), 1);
        assert_eq!(test_clock.timer_names(), vec!["timer_test"]);

        // Advance time and verify timer fires at correct intervals
        let start_ns = UnixNanos::from(start_time);
        let interval_ns = interval.as_nanos() as u64;

        let events = test_clock.advance_time(start_ns + interval_ns * 3, true);
        assert_eq!(events.len(), 3); // Should fire 3 times

        // Verify timing
        assert_eq!(*events[0].ts_event, *start_ns + interval_ns);
        assert_eq!(*events[1].ts_event, *start_ns + interval_ns * 2);
        assert_eq!(*events[2].ts_event, *start_ns + interval_ns * 3);
    }

    #[rstest]
    fn test_set_timer_with_stop_time_default_impl(mut test_clock: TestClock) {
        let current_time = test_clock.utc_now();
        let start_time = current_time + chrono::Duration::seconds(1);
        let stop_time = current_time + chrono::Duration::seconds(3);
        let interval = Duration::from_secs(1);

        // Test with stop time
        test_clock
            .set_timer(
                "timer_with_stop",
                interval,
                Some(start_time),
                Some(stop_time),
                None,
                None,
                None,
            )
            .unwrap();

        assert_eq!(test_clock.timer_count(), 1);

        // Advance beyond stop time
        let stop_ns = UnixNanos::from(stop_time);
        let events = test_clock.advance_time(stop_ns + 1000, true);

        // Should fire twice: at start_time + 1s and start_time + 2s, but not at start_time + 3s since that would be at stop_time
        assert_eq!(events.len(), 2);

        let start_ns = UnixNanos::from(start_time);
        let interval_ns = interval.as_nanos() as u64;
        assert_eq!(*events[0].ts_event, *start_ns + interval_ns);
        assert_eq!(*events[1].ts_event, *start_ns + interval_ns * 2);
    }

    #[rstest]
    fn test_set_timer_fire_immediately_default_impl(mut test_clock: TestClock) {
        let current_time = test_clock.utc_now();
        let start_time = current_time + chrono::Duration::seconds(1);
        let interval = Duration::from_millis(500);

        // Test with fire_immediately=true
        test_clock
            .set_timer(
                "immediate_timer",
                interval,
                Some(start_time),
                None,
                None,
                None,
                Some(true),
            )
            .unwrap();

        let start_ns = UnixNanos::from(start_time);
        let interval_ns = interval.as_nanos() as u64;

        // Advance to start time + 1 interval
        let events = test_clock.advance_time(start_ns + interval_ns, true);

        // Should fire immediately at start_time, then again at start_time + interval
        assert_eq!(events.len(), 2);
        assert_eq!(*events[0].ts_event, *start_ns); // Immediate fire
        assert_eq!(*events[1].ts_event, *start_ns + interval_ns); // Regular interval
    }

    #[rstest]
    fn test_set_time_alert_when_alert_time_equals_current_time(mut test_clock: TestClock) {
        let current_time = test_clock.timestamp_ns();

        // Set time alert for exactly the current time
        test_clock
            .set_time_alert_ns("alert_at_current_time", current_time, None, None)
            .unwrap();

        assert_eq!(test_clock.timer_count(), 1);

        // Advance time by exactly 0 (to current time) - should fire immediately
        let events = test_clock.advance_time(current_time, true);

        // Should fire immediately since alert_time_ns == ts_now
        assert_eq!(events.len(), 1);
        assert_eq!(events[0].name.as_str(), "alert_at_current_time");
        assert_eq!(*events[0].ts_event, *current_time);
    }

    #[rstest]
    fn test_cancel_and_reschedule_same_name(mut test_clock: TestClock) {
        let start = test_clock.timestamp_ns();

        test_clock
            .set_time_alert_ns("timer", UnixNanos::from(*start + 1000), None, None)
            .unwrap();
        assert_eq!(test_clock.timer_count(), 1);

        test_clock.cancel_timer("timer");
        assert_eq!(test_clock.timer_count(), 0);

        test_clock
            .set_time_alert_ns("timer", UnixNanos::from(*start + 2000), None, None)
            .unwrap();
        assert_eq!(test_clock.timer_count(), 1);

        let events = test_clock.advance_time(UnixNanos::from(*start + 1500), true);
        assert!(events.is_empty());

        let events = test_clock.advance_time(UnixNanos::from(*start + 2000), true);
        assert_eq!(events.len(), 1);
        assert_eq!(*events[0].ts_event, *start + 2000);
    }

    #[rstest]
    fn test_multiple_timers_same_timestamp_all_fire(mut test_clock: TestClock) {
        let fire_time = UnixNanos::from(*test_clock.timestamp_ns() + 1000);

        for i in 0..5 {
            test_clock
                .set_time_alert_ns(&format!("timer_{i}"), fire_time, None, None)
                .unwrap();
        }
        assert_eq!(test_clock.timer_count(), 5);

        let events = test_clock.advance_time(fire_time, true);
        assert_eq!(events.len(), 5);
        for event in &events {
            assert_eq!(*event.ts_event, *fire_time);
        }
    }

    #[rstest]
    fn test_events_ordered_by_timestamp_after_advance() {
        let mut clock = TestClock::new();
        clock.register_default_handler(TestCallback::default().into());
        let start = clock.timestamp_ns();

        clock
            .set_time_alert_ns("third", UnixNanos::from(*start + 300), None, None)
            .unwrap();
        clock
            .set_time_alert_ns("first", UnixNanos::from(*start + 100), None, None)
            .unwrap();
        clock
            .set_time_alert_ns("second", UnixNanos::from(*start + 200), None, None)
            .unwrap();

        let events = clock.advance_time(UnixNanos::from(*start + 400), true);
        assert_eq!(events.len(), 3);
        assert_eq!(events[0].name.as_str(), "first");
        assert_eq!(events[1].name.as_str(), "second");
        assert_eq!(events[2].name.as_str(), "third");
    }

    #[rstest]
    fn test_large_interval_does_not_overflow(mut test_clock: TestClock) {
        let start = test_clock.timestamp_ns();
        let large_interval: u64 = 1_000_000_000 * 60 * 60 * 24 * 365; // ~1 year in ns

        test_clock
            .set_timer_ns(
                "large_interval",
                large_interval,
                Some(start),
                None,
                None,
                None,
                None,
            )
            .unwrap();

        let events = test_clock.advance_time(UnixNanos::from(*start + large_interval), true);
        assert_eq!(events.len(), 1);
        assert_eq!(*events[0].ts_event, *start + large_interval);
    }

    #[rstest]
    fn test_near_zero_interval_fires_correctly(mut test_clock: TestClock) {
        let start = test_clock.timestamp_ns();

        test_clock
            .set_timer_ns("tiny", 1, Some(start), None, None, None, None)
            .unwrap();

        let events = test_clock.advance_time(UnixNanos::from(*start + 10), true);
        assert_eq!(events.len(), 10);

        for i in 1..events.len() {
            assert!(events[i].ts_event >= events[i - 1].ts_event);
        }
    }

    #[rstest]
    fn test_repeated_advance_to_same_time_no_double_fire(mut test_clock: TestClock) {
        let fire_time = UnixNanos::from(*test_clock.timestamp_ns() + 1000);

        test_clock
            .set_time_alert_ns("once", fire_time, None, None)
            .unwrap();

        let events1 = test_clock.advance_time(fire_time, true);
        assert_eq!(events1.len(), 1);

        let events2 = test_clock.advance_time(fire_time, true);
        assert!(events2.is_empty());
    }

    #[rstest]
    fn test_advance_with_no_timers(mut test_clock: TestClock) {
        let start = test_clock.timestamp_ns();

        let events = test_clock.advance_time(UnixNanos::from(*start + 1000), true);
        assert!(events.is_empty());
        assert_eq!(*test_clock.timestamp_ns(), *start + 1000);
    }

    #[rstest]
    fn test_clock_api_new_uses_native_backing(test_clock: TestClock) {
        let clock = RefCell::new(test_clock);
        let api = ClockApi::new(&clock);

        api.set_timer_ns(
            "native-timer",
            1_000,
            None,
            None,
            None,
            Some(true),
            Some(false),
        )
        .unwrap();

        assert_eq!(api.timer_count(), 1);
        assert_eq!(api.timer_names(), vec!["native-timer".to_string()]);
        assert_eq!(
            api.next_time_ns("native-timer"),
            Some(UnixNanos::from(1_000))
        );
    }

    #[rstest]
    fn test_clock_api_handlers_back_full_surface() {
        let alerts = Arc::new(Mutex::new(Vec::new()));
        let timers = Arc::new(Mutex::new(Vec::new()));
        let cancellations = Arc::new(Mutex::new(Vec::new()));
        let cancel_all = Arc::new(Mutex::new(false));

        let alerts_for_handler = Arc::clone(&alerts);
        let timers_for_handler = Arc::clone(&timers);
        let cancellations_for_handler = Arc::clone(&cancellations);
        let cancel_all_for_handler = Arc::clone(&cancel_all);

        let clock = ClockApi::from_handlers(
            || UnixNanos::from(1_700_000_000_123_456_789),
            move |name, alert_time_ns, _callback, allow_past| {
                alerts_for_handler.lock().expect(MUTEX_POISONED).push((
                    name.to_string(),
                    alert_time_ns,
                    allow_past,
                ));
                Ok(())
            },
            move |name,
                  interval_ns,
                  start_time_ns,
                  stop_time_ns,
                  _callback,
                  allow_past,
                  fire_immediately| {
                timers_for_handler.lock().expect(MUTEX_POISONED).push((
                    name.to_string(),
                    interval_ns,
                    start_time_ns,
                    stop_time_ns,
                    allow_past,
                    fire_immediately,
                ));
                Ok(())
            },
            || vec!["alpha".to_string(), "beta".to_string()],
            || 2,
            |name| name == "alpha",
            |name| (name == "alpha").then(|| UnixNanos::from(1_700_000_000_999_000_000)),
            move |name| {
                cancellations_for_handler
                    .lock()
                    .expect(MUTEX_POISONED)
                    .push(name.to_string());
            },
            move || {
                *cancel_all_for_handler.lock().expect(MUTEX_POISONED) = true;
            },
        );

        let alert_time = DateTime::from_timestamp_nanos(1_700_000_000_333_000_000);
        let start_time = DateTime::from_timestamp_nanos(1_700_000_000_444_000_000);
        let stop_time = DateTime::from_timestamp_nanos(1_700_000_001_444_000_000);
        clock
            .set_time_alert("alert", alert_time, None, Some(false))
            .unwrap();
        clock
            .set_time_alert_ns(
                "alert-ns",
                UnixNanos::from(1_700_000_000_555_000_000),
                None,
                Some(true),
            )
            .unwrap();
        clock
            .set_timer(
                "timer",
                Duration::from_millis(250),
                Some(start_time),
                Some(stop_time),
                None,
                Some(true),
                Some(false),
            )
            .unwrap();
        clock
            .set_timer_ns(
                "timer-ns",
                500_000_000,
                Some(UnixNanos::from(1_700_000_000_666_000_000)),
                Some(UnixNanos::from(1_700_000_001_666_000_000)),
                None,
                Some(false),
                Some(true),
            )
            .unwrap();
        clock.cancel_timer("alpha");
        clock.cancel_timers();

        assert_eq!(
            clock.timestamp_ns(),
            UnixNanos::from(1_700_000_000_123_456_789)
        );
        assert_eq!(clock.timestamp_us(), 1_700_000_000_123_456);
        assert_eq!(clock.timestamp_ms(), 1_700_000_000_123);
        assert_eq!(clock.timestamp(), 1_700_000_000.123_456_7);
        assert_eq!(
            clock.utc_now(),
            DateTime::from_timestamp_nanos(1_700_000_000_123_456_789)
        );
        assert_eq!(clock.timer_names(), vec!["alpha", "beta"]);
        assert_eq!(clock.timer_count(), 2);
        assert!(clock.timer_exists("alpha"));
        assert!(!clock.timer_exists("gamma"));
        assert_eq!(
            clock.next_time_ns("alpha"),
            Some(UnixNanos::from(1_700_000_000_999_000_000))
        );
        assert_eq!(
            alerts.lock().expect(MUTEX_POISONED).as_slice(),
            &[
                (
                    "alert".to_string(),
                    UnixNanos::from(1_700_000_000_333_000_000),
                    Some(false)
                ),
                (
                    "alert-ns".to_string(),
                    UnixNanos::from(1_700_000_000_555_000_000),
                    Some(true)
                )
            ]
        );
        assert_eq!(
            timers.lock().expect(MUTEX_POISONED).as_slice(),
            &[
                (
                    "timer".to_string(),
                    250_000_000,
                    Some(UnixNanos::from(1_700_000_000_444_000_000)),
                    Some(UnixNanos::from(1_700_000_001_444_000_000)),
                    Some(true),
                    Some(false)
                ),
                (
                    "timer-ns".to_string(),
                    500_000_000,
                    Some(UnixNanos::from(1_700_000_000_666_000_000)),
                    Some(UnixNanos::from(1_700_000_001_666_000_000)),
                    Some(false),
                    Some(true)
                )
            ]
        );
        assert_eq!(
            cancellations.lock().expect(MUTEX_POISONED).as_slice(),
            &["alpha".to_string()]
        );
        assert!(*cancel_all.lock().expect(MUTEX_POISONED));
    }
}