dsi-progress-logger 0.8.8

/*
 * SPDX-FileCopyrightText: 2023 Inria
 * SPDX-FileCopyrightText: 2023 Sebastiano Vigna
 *
 * SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later
 */

/// A unit of time, from nanoseconds to days.
///
/// Time units are used to display timings and speeds. Usually the most
/// convenient unit is chosen automatically, but you can fix a specific unit
/// with [`ProgressLog::time_unit`](crate::ProgressLog::time_unit).
#[derive(Debug, Copy, Clone)]
pub enum TimeUnit {
    /// A nanosecond (10⁻⁹ seconds).
    NanoSeconds,
    /// A microsecond (10⁻⁶ seconds).
    MicroSeconds,
    /// A millisecond (10⁻³ seconds).
    MilliSeconds,
    /// A second.
    Seconds,
    /// A minute (60 seconds).
    Minutes,
    /// An hour (3600 seconds).
    Hours,
    /// A day (86400 seconds).
    Days,
}

impl TimeUnit {
    /// All time units, in increasing order of duration.
    pub const VALUES: [TimeUnit; 7] = [
        TimeUnit::NanoSeconds,
        TimeUnit::MicroSeconds,
        TimeUnit::MilliSeconds,
        TimeUnit::Seconds,
        TimeUnit::Minutes,
        TimeUnit::Hours,
        TimeUnit::Days,
    ];

    /// Returns the label used to display this time unit (e.g., `s` for
    /// [`Seconds`](TimeUnit::Seconds)).
    pub const fn label(&self) -> &'static str {
        match self {
            TimeUnit::NanoSeconds => "ns",
            TimeUnit::MicroSeconds => "μs",
            TimeUnit::MilliSeconds => "ms",
            TimeUnit::Seconds => "s",
            TimeUnit::Minutes => "m",
            TimeUnit::Hours => "h",
            TimeUnit::Days => "d",
        }
    }

    /// Returns the length of this time unit in seconds.
    pub const fn as_seconds(&self) -> f64 {
        match self {
            TimeUnit::NanoSeconds => 1.0e-9,
            TimeUnit::MicroSeconds => 1.0e-6,
            TimeUnit::MilliSeconds => 1.0e-3,
            TimeUnit::Seconds => 1.0,
            TimeUnit::Minutes => 60.0,
            TimeUnit::Hours => 3600.0,
            TimeUnit::Days => 86400.0,
        }
    }

    /// Returns the largest time unit not exceeding the given duration in
    /// seconds; it is used to display per-item timings.
    ///
    /// For durations shorter than a nanosecond,
    /// [`NanoSeconds`](TimeUnit::NanoSeconds) is returned.
    pub const fn nice_time_unit(seconds: f64) -> Self {
        let mut i = TimeUnit::VALUES.len();
        while i > 0 {
            i -= 1;
            if seconds >= TimeUnit::VALUES[i].as_seconds() {
                return TimeUnit::VALUES[i];
            }
        }
        TimeUnit::NanoSeconds
    }

    /// Returns the smallest time unit, starting from
    /// [`Seconds`](TimeUnit::Seconds), in which an activity taking the given
    /// number of seconds per item progresses at a speed of at least one item
    /// per unit; it is used to display speeds.
    ///
    /// For activities slower than one item per day, [`Days`](TimeUnit::Days)
    /// is returned.
    pub const fn nice_speed_unit(seconds: f64) -> Self {
        let mut i = 3;
        while i < TimeUnit::VALUES.len() {
            if seconds <= TimeUnit::VALUES[i].as_seconds() {
                return TimeUnit::VALUES[i];
            }
            i += 1;
        }
        TimeUnit::Days
    }

    /// Pretty-prints a duration expressed in milliseconds.
    ///
    /// Durations of less than a second are displayed as `{}ms`; longer
    /// durations are displayed as days, hours, minutes, and seconds (e.g.,
    /// `1d 3h 10m 5s`), discarding the sub-second part.
    pub fn pretty_print(milliseconds: u128) -> String {
        let mut result = String::new();

        if milliseconds < 1000 {
            return format!("{}ms", milliseconds);
        }

        let mut seconds = milliseconds / 1000;

        for unit in [TimeUnit::Days, TimeUnit::Hours, TimeUnit::Minutes] {
            let to_seconds = unit.as_seconds() as u128;
            if seconds >= to_seconds {
                result.push_str(&format!("{}{} ", seconds / to_seconds, unit.label(),));
                seconds %= to_seconds;
            }
        }

        result.push_str(&format!("{}s", seconds));

        result
    }
}

/// Scales down a value by powers of 1000, returning the scaled value and the
/// associated SI prefix.
///
/// For example, `scale(1234.0)` returns `(1.234, "k")`. Values of a
/// septillion (10²⁴) or more are all scaled to yottas (`Y`).
pub const fn scale(mut val: f64) -> (f64, &'static str) {
    const UNITS: &[&str] = &["", "k", "M", "G", "T", "P", "E", "Z", "Y"];
    let mut i = 0;
    while i < UNITS.len() {
        if val < 1000.0 {
            return (val, UNITS[i]);
        }
        val /= 1000.0;
        i += 1;
    }

    (val, "Y")
}

/// Formats a value scaled with [`scale`] using two decimal digits (e.g.,
/// `1.23G`).
pub fn humanize(val: f64) -> String {
    let (val, unit) = scale(val);
    format!("{:.2}{}", val, unit)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_scale() {
        assert_eq!(scale(1000.0), (1.0, "k"));
        assert_eq!(scale(300_000.0), (300.0, "k"));
        assert_eq!(scale(1_000_000_000.0), (1.0, "G"));
    }

    #[test]
    fn test_humanize() {
        assert_eq!(humanize(1000.0), "1.00k");
        assert_eq!(humanize(12_345.0), "12.35k");
        assert_eq!(humanize(1_234_567_890.0), "1.23G");
    }

    #[test]
    fn test_pretty_print() {
        assert_eq!(TimeUnit::pretty_print(500), "500ms");
        assert_eq!(TimeUnit::pretty_print(1000), "1s");
        assert_eq!(TimeUnit::pretty_print(1500), "1s");
        assert_eq!(TimeUnit::pretty_print(90_061_000), "1d 1h 1m 1s");
    }

    #[test]
    fn test_nice_units() {
        assert_eq!(TimeUnit::nice_time_unit(0.5).label(), "ms");
        assert_eq!(TimeUnit::nice_time_unit(100.0).label(), "m");
        assert_eq!(TimeUnit::nice_speed_unit(0.5).label(), "s");
        assert_eq!(TimeUnit::nice_speed_unit(100.0).label(), "h");
    }
}