#![doc = include_str!("../README.md")]

// @@ begin lint list maintained by maint/add_warning @@

#![allow(renamed_and_removed_lints)] // @@REMOVE_WHEN(ci_arti_stable)

#![allow(unknown_lints)] // @@REMOVE_WHEN(ci_arti_nightly)

#![warn(missing_docs)]

#![warn(noop_method_call)]

#![warn(unreachable_pub)]

#![warn(clippy::all)]

#![deny(clippy::await_holding_lock)]

#![deny(clippy::cargo_common_metadata)]

#![deny(clippy::cast_lossless)]

#![deny(clippy::checked_conversions)]

#![allow(clippy::cognitive_complexity)] // See arti#2556

#![deny(clippy::debug_assert_with_mut_call)]

#![deny(clippy::exhaustive_enums)]

#![deny(clippy::exhaustive_structs)]

#![deny(clippy::expl_impl_clone_on_copy)]

#![deny(clippy::fallible_impl_from)]

#![deny(clippy::implicit_clone)]

#![deny(clippy::large_stack_arrays)]

#![warn(clippy::manual_ok_or)]

#![deny(clippy::missing_docs_in_private_items)]

#![warn(clippy::needless_borrow)]

#![warn(clippy::needless_pass_by_value)]

#![warn(clippy::option_option)]

#![warn(clippy::or_fun_call)]

#![deny(clippy::print_stderr)]

#![deny(clippy::print_stdout)]

#![warn(clippy::rc_buffer)]

#![deny(clippy::ref_option_ref)]

#![warn(clippy::semicolon_if_nothing_returned)]

#![warn(clippy::trait_duplication_in_bounds)]

#![deny(clippy::unchecked_time_subtraction)]

#![deny(clippy::unnecessary_wraps)]

#![warn(clippy::unseparated_literal_suffix)]

#![deny(clippy::unwrap_used)]

#![deny(clippy::mod_module_files)]

#![allow(clippy::let_unit_value)] // This can reasonably be done for explicitness

#![allow(clippy::uninlined_format_args)]

#![allow(clippy::significant_drop_in_scrutinee)] // arti/-/merge_requests/588/#note_2812945

#![allow(clippy::result_large_err)] // temporary workaround for arti#587

#![allow(clippy::needless_raw_string_hashes)] // complained-about code is fine, often best

#![allow(clippy::needless_lifetimes)] // See arti#1765

#![allow(mismatched_lifetime_syntaxes)] // temporary workaround for arti#2060

#![allow(clippy::collapsible_if)] // See arti#2342

#![deny(clippy::unused_async)]

#![deny(clippy::string_slice)] // See arti#2571

#![allow(recursion_depth_exceeding_limit)] // arti#2715, rust/issues/159228

//! <!-- @@ end lint list maintained by maint/add_warning @@ -->

#![allow(unexpected_cfgs)]

#![forbid(unsafe_code)]

#![cfg_attr(

    saturating_time_nightly,

    feature(time_systemtime_limits, time_saturating_systemtime)

)]

use std::time::{Duration, Instant, SystemTime};

mod internal;

/// The core trait of this crait, [`SaturatingTime`].

///

/// This trait provides methods for performing saturating arithmetic on those

/// types in [`std::time`] that not already come with such a functionality,

/// such as [`SystemTime`] or [`Instant`].

///

/// The trait itself is not implementable from the outside, because it is sealed

/// by an internal trait.

///

/// See the methods or the top-level documentation for concrete code examples.

pub trait SaturatingTime: internal::SaturatingTime {

    /// Returns the maximum value for this type on the current platform.

    ///

    /// This limit is highly platform specific.  It differs heavily between

    /// Unix, Windows, and other operating systems.

    ///

    /// The limit itself is calculated dynamically during runtime with a correct

    /// algorithm.  Afterwards, it gets stored in a lazy static value, meaning

    /// that only the first call to it will be slightly more expensive, whereas

    /// all latter calls will result in an immediate return of the value.

    ///

    /// # Examples

    ///

    /// ```

    /// use std::time::{Duration, SystemTime};

    /// use saturating_time::SaturatingTime;

    ///

    /// let max = SystemTime::max_value();

    ///

    /// // Adding zero to the maximum value will change nothing.

    /// assert!(max.checked_add(Duration::ZERO).is_some());

    ///

    /// // Adding 1ns to the maximum value will fail.

    /// assert!(max.checked_add(Duration::new(0, 1)).is_none());

    ///

    /// // Subtracting 1ns from the maximum value will work of course.

    /// assert!(max.checked_sub(Duration::new(0, 1)).is_some());

    /// ```

    /// Returns the minimum value for this type on the current platform.

    ///

    /// This limit is highly platform specific.  It differs heavily between

    /// Unix, Windows, and other operating systems.

    ///

    /// The limit itself is calculated dynamically during runtime with a correct

    /// algorithm.  Afterwards, it gets stored in a lazy static value, meaning

    /// that only the first call to it will be slightly more expensive, whereas

    /// all latter calls will result in an immediate return of the value.

    ///

    /// # Examples

    ///

    /// ```

    /// use std::time::{Duration, SystemTime};

    /// use saturating_time::SaturatingTime;

    ///

    /// let min = SystemTime::min_value();

    ///

    /// // Subtracting a zero from the minimum value will change nothing.

    /// assert!(min.checked_sub(Duration::ZERO).is_some());

    ///

    /// // Subtracting 1ns from the minimum value will fail.

    /// assert!(min.checked_sub(Duration::new(0, 1)).is_none());

    ///

    /// // Adding 1ns to the minimum value will work of course.

    /// assert!(min.checked_add(Duration::new(0, 1)).is_some());

    /// ```

    /// Performs a saturating addition of a [`Duration`].

    ///

    /// The resulting value will saturate to [`SaturatingTime::max_value()`] in

    /// the case the addition would have caused an overflow of value.

    ///

    /// # Examples

    ///

    /// ```

    /// use std::time::{Duration, SystemTime};

    /// use saturating_time::SaturatingTime;

    ///

    /// let max = SystemTime::max_value();

    ///

    /// // Adding zero will change nothing.

    /// assert_eq!(max.saturating_add(Duration::ZERO), max);

    ///

    /// // Adding 1ns would overflow so we saturate to the maximum.

    /// assert_eq!(max.saturating_add(Duration::new(0, 1)), max);

    /// ```

    /// Performs a saturating subtraction of a [`Duration`].

    ///

    /// The resulting value will saturate to [`SaturatingTime::min_value()`] in

    /// the case the subtraction would have caused an overflow of value.

    ///

    /// # Examples

    ///

    /// ```

    /// use std::time::{Duration, SystemTime};

    /// use saturating_time::SaturatingTime;

    ///

    /// let min = SystemTime::min_value();

    ///

    /// // Subtracting zero will change nothing.

    /// assert_eq!(min.saturating_sub(Duration::ZERO), min);

    ///

    /// // Subtracting 1ns would overflow so we saturate to the minimum.

    /// assert_eq!(min.saturating_sub(Duration::new(0, 1)), min);

    /// ```

    /// Performs a saturating time difference calculation between two points.

    ///

    /// The resulting value will saturate to [`Duration::ZERO`] in the case that

    /// the `earlier` point in time is actually not earlier, thereby resulting

    /// in a negative difference.

    ///

    /// # Examples

    ///

    /// ```

    /// use std::time::{Duration, SystemTime};

    /// use saturating_time::SaturatingTime;

    ///

    /// let epoch = SystemTime::UNIX_EPOCH;

    /// let now = SystemTime::now();

    /// let min = SystemTime::min_value();

    ///

    /// assert!(now.saturating_duration_since(epoch).as_secs() > 0);

    /// assert!(epoch.saturating_duration_since(epoch) == Duration::ZERO);

    /// assert!(min.saturating_duration_since(epoch) == Duration::ZERO);

    /// ```

}

// Use nightly implementation if compiled with the nightly feature.

#[cfg(saturating_time_nightly)]

impl SaturatingTime for SystemTime {

    fn max_value() -> Self {

        Self::MAX

    }

    fn min_value() -> Self {

        Self::MIN

    }

    fn saturating_add(self, duration: Duration) -> Self {

        Self::saturating_add(&self, duration)

    }

    fn saturating_sub(self, duration: Duration) -> Self {

        Self::saturating_sub(&self, duration)

    }

    fn saturating_duration_since(&self, earlier: Self) -> Duration {

        Self::saturating_duration_since(&self, earlier)

    }

}

// Otherwise, use the default one.

#[cfg(not(saturating_time_nightly))]

impl SaturatingTime for SystemTime {}

impl SaturatingTime for Instant {

    // Override to use the provided implementation from the standard library.

}

#[cfg(test)]

mod tests {

    // @@ begin test lint list maintained by maint/add_warning @@

    #![allow(clippy::bool_assert_comparison)]

    #![allow(clippy::clone_on_copy)]

    #![allow(clippy::dbg_macro)]

    #![allow(clippy::mixed_attributes_style)]

    #![allow(clippy::print_stderr)]

    #![allow(clippy::print_stdout)]

    #![allow(clippy::single_char_pattern)]

    #![allow(clippy::unwrap_used)]

    #![allow(clippy::unchecked_time_subtraction)]

    #![allow(clippy::useless_vec)]

    #![allow(clippy::needless_pass_by_value)]

    #![allow(clippy::string_slice)] // See arti#2571

    //! <!-- @@ end test lint list maintained by maint/add_warning @@ -->

    use super::*;

    use crate::internal;

    use std::{

        fmt::Debug,

        ops::{Add, Sub},

        time::{Instant, SystemTime},

    };

    /// Verifies the maximum and minimum values of [`SaturatingTime`] equal

    /// their pedant in [`internal::SaturatingTime`].

    fn min_max<T: SaturatingTime + PartialEq + Debug>() {

        assert_eq!(

            <T as SaturatingTime>::max_value(),

            <T as internal::SaturatingTime>::max_value()

        );

        assert_eq!(

            <T as SaturatingTime>::min_value(),

            <T as internal::SaturatingTime>::min_value()

        );

    }

    /// Verifies the saturating arithmetic for [`SaturatingTime`].

    fn saturating_add_sub<

        T: SaturatingTime + PartialEq + Debug + Add<Duration, Output = T> + Sub<Duration, Output = T>,

    >() {

        let max = <T as SaturatingTime>::max_value();

        assert_eq!(max.saturating_add(Duration::ZERO), max);

        assert_eq!(max.saturating_add(Duration::new(0, 1)), max);

        assert_eq!(max.saturating_sub(Duration::ZERO), max);

        assert_eq!(

            max.saturating_sub(Duration::new(0, 1)),

            max - Duration::new(0, 1)

        );

        let min = <T as SaturatingTime>::min_value();

        assert_eq!(min.saturating_sub(Duration::ZERO), min);

        assert_eq!(min.saturating_sub(Duration::new(0, 1)), min);

        assert_eq!(min.saturating_add(Duration::ZERO), min);

        assert_eq!(

            min.saturating_add(Duration::new(0, 1)),

            min + Duration::new(0, 1)

        );

    }

    /// Verifies whether the saturating logic behind [`Duration`] types work.

    fn saturating_duration<T: SaturatingTime + PartialEq + Debug>() {

        // The duration from the same anchor should always be zero.

        let anchor = T::anchor();

        assert_eq!(anchor.saturating_duration_since(anchor), Duration::ZERO);

        // Try with a later anchor.

        let later_anchor = anchor.checked_add(Duration::from_secs(1)).unwrap();

        assert!(later_anchor.saturating_duration_since(anchor) == Duration::from_secs(1));

        assert_eq!(

            anchor.saturating_duration_since(later_anchor),

            Duration::ZERO

        );

        // Try with min and max.

        let max = <T as SaturatingTime>::max_value();

        let min = <T as SaturatingTime>::min_value();

        // This first assertion might not be so portable, maybe remove it if

        // this becomes a problem.

        assert_eq!(max.saturating_duration_since(min), Duration::MAX);

        assert_eq!(min.saturating_duration_since(max), Duration::ZERO);

    }

    /// Calls [`min_max()`] using [`SystemTime`].

    #[test]

    fn system_time_min_max() {

        min_max::<SystemTime>();

    }

    /// Calls [`min_max()`] using [`Instant`].

    #[test]

    fn instant_min_max() {

        min_max::<Instant>();

    }

    /// Calls [`saturating_add_sub()`] and [`saturating_duration()`] using [`SystemTime`].

    #[test]

    fn system_time_saturating() {

        saturating_add_sub::<SystemTime>();

        saturating_duration::<SystemTime>();

    }

    /// Calls [`saturating_add_sub()`] and [`saturating_duration()`] using [`Instant`].

    #[test]

    fn instant_saturating() {

        saturating_add_sub::<Instant>();

        saturating_duration::<Instant>();

    }

}