deep-time 0.1.0-alpha.2

use crate::{
    ATTOS_PER_FS, ATTOS_PER_MS, ATTOS_PER_NS, ATTOS_PER_PS, ATTOS_PER_SEC_I128, ATTOS_PER_SECF,
    ATTOS_PER_US, ClockDrift, Dt, LocalSpacetime, Real, TSpan,
};

impl Dt {
    #[inline]
    pub const fn add(self, span: TSpan) -> Self {
        let (sec, attos) = TSpan::add_time(self.sec, self.attos, span.sec, span.attos);
        Self { sec, attos }
    }

    #[inline]
    pub const fn sub(self, span: TSpan) -> Self {
        let (sec, attos) = TSpan::sub_time(self.sec, self.attos, span.sec, span.attos);
        Self { sec, attos }
    }

    /// Converts this `Dt` to a floating-point number of seconds since the reference epoch of its associated scale.
    ///
    /// The conversion is lossy by design, as `f64` (`Real`) provides approximately 15.95 decimal digits of precision.
    /// For full exactness, use the integer components `sec` and `attos` directly or higher-precision arithmetic when available.
    #[inline]
    pub const fn to_sec_f(self) -> Real {
        f!(self.sec) + f!(self.attos) / ATTOS_PER_SECF
    }

    /// Advances this `Dt` by the given elapsed duration while applying the relativistic proper-time correction
    /// derived from the supplied `LocalSpacetime` model.
    ///
    /// This method is intended for simulation of remote clocks (e.g., Earth time as observed from a spacecraft).
    /// For the spacecraft's own hardware proper-time clock, use the plain `add` method instead.
    #[inline]
    pub const fn adjusted_advance(&mut self, elapsed: &TSpan, local_spacetime: &LocalSpacetime) {
        let dtau =
            elapsed.add(ClockDrift::from_local_spacetime(local_spacetime).time_diff_after(elapsed));
        *self = self.add(dtau);
    }

    /// Advances this `Dt` by the given elapsed duration while applying the relativistic proper-time correction
    /// from a pre-computed `ClockDrift` value.
    ///
    /// This is an optimized variant of `adjusted_advance` for callers that already hold a `ClockDrift` instance.
    /// It is intended for simulation of remote clocks; the spacecraft's own hardware clock should use the plain `add` method.
    #[inline]
    pub const fn adjusted_advance_using_drift(&mut self, elapsed: &TSpan, drift: &ClockDrift) {
        let dtau = elapsed.add(drift.time_diff_after(elapsed));
        *self = self.add(dtau);
    }

    /// Computes the TAI signed duration between this `Dt` and an earlier instant.
    #[inline]
    pub const fn to_tai_since(&self, earlier: Self) -> TSpan {
        TSpan::diff_raw(self.sec, self.attos, earlier.sec, earlier.attos)
    }

    /// This method is lossy by design and is provided for testing and debugging purposes only.
    /// For the exact duration, use `duration_since` or `duration_since_ref`.
    #[inline]
    pub const fn to_tai_since_f(&self, other: Self) -> Real {
        self.to_sec_f() - other.to_sec_f()
    }

    /// Adds exactly 1 second to this time value using saturating arithmetic.
    #[inline]
    pub const fn add_1sec(&mut self) {
        self.sec = self.sec.saturating_add(1);
    }

    /// Adds exactly 1 minute (60 seconds) to this time value using saturating arithmetic.
    #[inline]
    pub const fn add_1min(&mut self) {
        self.sec = self.sec.saturating_add(60);
    }

    /// Adds exactly 1 hour (3600 seconds) to this time value using saturating arithmetic.
    #[inline]
    pub const fn add_1hr(&mut self) {
        self.sec = self.sec.saturating_add(3600);
    }

    /// Adds exactly 1 millisecond to this time value.
    ///
    /// This affects the subsecond component and may cause a carry into the seconds field.
    #[inline]
    pub const fn add_1ms(&mut self) {
        TSpan::add_attos_to(&mut self.sec, &mut self.attos, ATTOS_PER_MS);
    }

    /// Adds exactly 1 microsecond to this time value.
    ///
    /// This affects the subsecond component and may cause a carry into the seconds field.
    #[inline]
    pub const fn add_1us(&mut self) {
        TSpan::add_attos_to(&mut self.sec, &mut self.attos, ATTOS_PER_US);
    }

    /// Adds exactly 1 nanosecond to this time value.
    ///
    /// This affects the subsecond component and may cause a carry into the seconds field.
    #[inline]
    pub const fn add_1ns(&mut self) {
        TSpan::add_attos_to(&mut self.sec, &mut self.attos, ATTOS_PER_NS);
    }

    /// Adds the specified number of seconds to this time value using saturating arithmetic.
    #[inline]
    pub const fn add_sec(&mut self, n: i64) {
        self.sec = self.sec.saturating_add(n);
    }

    /// Adds the specified number of minutes to this time value using saturating arithmetic.
    #[inline]
    pub const fn add_min(&mut self, n: i64) {
        self.sec = self.sec.saturating_add(n.saturating_mul(60));
    }

    /// Adds the specified number of hours to this time value using saturating arithmetic.
    #[inline]
    pub const fn add_hr(&mut self, n: i64) {
        self.sec = self.sec.saturating_add(n.saturating_mul(3600));
    }

    /// Adds the specified number of milliseconds to this time value.
    ///
    /// Handles carry into the seconds field using saturating logic.
    #[inline]
    pub const fn add_ms(&mut self, n: i64) {
        TSpan::add_attos_span(&mut self.sec, &mut self.attos, n, ATTOS_PER_MS);
    }

    /// Adds the specified number of microseconds to this time value.
    ///
    /// Handles carry into the seconds field using saturating logic.
    #[inline]
    pub const fn add_us(&mut self, n: i64) {
        TSpan::add_attos_span(&mut self.sec, &mut self.attos, n, ATTOS_PER_US);
    }

    /// Adds the specified number of nanoseconds to this time value.
    ///
    /// Handles carry into the seconds field using saturating logic.
    #[inline]
    pub const fn add_ns(&mut self, n: i64) {
        TSpan::add_attos_span(&mut self.sec, &mut self.attos, n, ATTOS_PER_NS);
    }

    /// Adds the specified number of picoseconds to this time value.
    ///
    /// Handles carry into the seconds field using saturating logic.
    #[inline]
    pub const fn add_ps(&mut self, n: i64) {
        TSpan::add_attos_span(&mut self.sec, &mut self.attos, n, ATTOS_PER_PS);
    }

    /// Adds the specified number of femtoseconds to this time value.
    ///
    /// Handles carry into the seconds field using saturating logic.
    #[inline]
    pub const fn add_fs(&mut self, n: i64) {
        TSpan::add_attos_span(&mut self.sec, &mut self.attos, n, ATTOS_PER_FS);
    }

    /// Adds the specified number of attoseconds to this time value.
    ///
    /// Handles carry into the seconds field using saturating logic.
    #[inline]
    pub const fn add_attos(&mut self, n: i64) {
        TSpan::add_attos_span(&mut self.sec, &mut self.attos, n, 1);
    }

    // =====================================================================
    // Single-unit subtraction methods (convenience methods for -1)
    // =====================================================================

    /// Subtracts exactly 1 hour (3600 seconds) from this time value using saturating arithmetic.
    #[inline]
    pub const fn sub_1hr(&mut self) {
        self.sec = self.sec.saturating_sub(3600);
    }

    /// Subtracts exactly 1 minute (60 seconds) from this time value using saturating arithmetic.
    #[inline]
    pub const fn sub_1min(&mut self) {
        self.sec = self.sec.saturating_sub(60);
    }

    /// Subtracts exactly 1 second from this time value using saturating arithmetic.
    #[inline]
    pub const fn sub_1sec(&mut self) {
        self.sec = self.sec.saturating_sub(1);
    }

    /// Subtracts exactly 1 millisecond from this time value.
    ///
    /// This affects the subsecond component and may cause a borrow from the seconds field.
    #[inline]
    pub const fn sub_1ms(&mut self) {
        TSpan::add_attos_span(&mut self.sec, &mut self.attos, -1, ATTOS_PER_MS);
    }

    /// Subtracts exactly 1 microsecond from this time value.
    ///
    /// This affects the subsecond component and may cause a borrow from the seconds field.
    #[inline]
    pub const fn sub_1us(&mut self) {
        TSpan::add_attos_span(&mut self.sec, &mut self.attos, -1, ATTOS_PER_US);
    }

    /// Subtracts exactly 1 nanosecond from this time value.
    ///
    /// This affects the subsecond component and may cause a borrow from the seconds field.
    #[inline]
    pub const fn sub_1ns(&mut self) {
        TSpan::add_attos_span(&mut self.sec, &mut self.attos, -1, ATTOS_PER_NS);
    }

    /// Subtracts the specified number of seconds from this time value using saturating arithmetic.
    #[inline]
    pub const fn sub_sec(&mut self, n: i64) {
        self.sec = self.sec.saturating_sub(n);
    }

    /// Subtracts the specified number of minutes from this time value using saturating arithmetic.
    #[inline]
    pub const fn sub_min(&mut self, n: i64) {
        self.sec = self.sec.saturating_sub(n.saturating_mul(60));
    }

    /// Subtracts the specified number of hours from this time value using saturating arithmetic.
    #[inline]
    pub const fn sub_hr(&mut self, n: i64) {
        self.sec = self.sec.saturating_sub(n.saturating_mul(3600));
    }

    /// Subtracts the specified number of milliseconds from this time value.
    ///
    /// Handles borrow from the seconds field using saturating logic.
    #[inline]
    pub const fn sub_ms(&mut self, n: i64) {
        TSpan::add_attos_span(
            &mut self.sec,
            &mut self.attos,
            n.saturating_neg(),
            ATTOS_PER_MS,
        );
    }

    /// Subtracts the specified number of microseconds from this time value.
    ///
    /// Handles borrow from the seconds field using saturating logic.
    #[inline]
    pub const fn sub_us(&mut self, n: i64) {
        TSpan::add_attos_span(
            &mut self.sec,
            &mut self.attos,
            n.saturating_neg(),
            ATTOS_PER_US,
        );
    }

    /// Subtracts the specified number of nanoseconds from this time value.
    ///
    /// Handles borrow from the seconds field using saturating logic.
    #[inline]
    pub const fn sub_ns(&mut self, n: i64) {
        TSpan::add_attos_span(
            &mut self.sec,
            &mut self.attos,
            n.saturating_neg(),
            ATTOS_PER_NS,
        );
    }

    /// Subtracts the specified number of picoseconds from this time value.
    ///
    /// Handles borrow from the seconds field using saturating logic.
    #[inline]
    pub const fn sub_ps(&mut self, n: i64) {
        TSpan::add_attos_span(
            &mut self.sec,
            &mut self.attos,
            n.saturating_neg(),
            ATTOS_PER_PS,
        );
    }

    /// Subtracts the specified number of femtoseconds from this time value.
    ///
    /// Handles borrow from the seconds field using saturating logic.
    #[inline]
    pub const fn sub_fs(&mut self, n: i64) {
        TSpan::add_attos_span(
            &mut self.sec,
            &mut self.attos,
            n.saturating_neg(),
            ATTOS_PER_FS,
        );
    }

    /// Subtracts the specified number of attoseconds from this time value.
    ///
    /// Handles borrow from the seconds field using saturating logic.
    #[inline]
    pub const fn sub_attos(&mut self, n: i64) {
        TSpan::add_attos_span(&mut self.sec, &mut self.attos, n.saturating_neg(), 1);
    }

    /// Total attoseconds (exact i128 representation within the representable range).
    #[inline]
    pub const fn to_attos(self) -> i128 {
        (self.sec as i128) * ATTOS_PER_SEC_I128 + (self.attos as i128)
    }

    /// Returns the total duration in milliseconds.
    #[inline]
    pub const fn to_ms(self) -> i128 {
        self.to_attos() / (ATTOS_PER_MS as i128)
    }

    /// Returns the total duration in microseconds.
    #[inline]
    pub const fn to_us(self) -> i128 {
        self.to_attos() / (ATTOS_PER_US as i128)
    }

    /// Returns the total duration in nanoseconds.
    #[inline]
    pub const fn to_ns(self) -> i128 {
        self.to_attos() / (ATTOS_PER_NS as i128)
    }

    /// Returns the total duration in picoseconds.
    #[inline]
    pub const fn to_ps(self) -> i128 {
        self.to_attos() / (ATTOS_PER_PS as i128)
    }

    /// Returns the total duration in femtoseconds.
    #[inline]
    pub const fn to_fs(self) -> i128 {
        self.to_attos() / (ATTOS_PER_FS as i128)
    }
}