1 files changed, 94 insertions, 0 deletions
diff --git a/crates/typst-utils/src/duration.rs b/crates/typst-utils/src/duration.rs
new file mode 100644
index 00000000..88348248
--- /dev/null
+++ b/crates/typst-utils/src/duration.rs
@@ -0,0 +1,94 @@
+use std::fmt::{self, Display, Formatter, Write};
+use std::time::Duration;
+
+use super::round_with_precision;
+
+/// Formats a duration with a precision suitable for human display.
+pub fn format_duration(duration: Duration) -> impl Display {
+    DurationDisplay(duration)
+}
+
+/// Displays a `Duration`.
+struct DurationDisplay(Duration);
+
+impl Display for DurationDisplay {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        let mut space = false;
+        macro_rules! piece {
+            ($($tts:tt)*) => {
+                if std::mem::replace(&mut space, true) {
+                    f.write_char(' ')?;
+                }
+                write!(f, $($tts)*)?;
+            };
+        }
+
+        let secs = self.0.as_secs();
+        let (mins, secs) = (secs / 60, (secs % 60));
+        let (hours, mins) = (mins / 60, (mins % 60));
+        let (days, hours) = ((hours / 24), (hours % 24));
+
+        if days > 0 {
+            piece!("{days} d");
+        }
+
+        if hours > 0 {
+            piece!("{hours} h");
+        }
+
+        if mins > 0 {
+            piece!("{mins} min");
+        }
+
+        // No need to display anything more than minutes at this point.
+        if days > 0 || hours > 0 {
+            return Ok(());
+        }
+
+        let order = |exp| 1000u64.pow(exp);
+        let nanos = secs * order(3) + self.0.subsec_nanos() as u64;
+        let fract = |exp| round_with_precision(nanos as f64 / order(exp) as f64, 2);
+
+        if nanos == 0 || self.0 > Duration::from_secs(1) {
+            // For durations > 5 min, we drop the fractional part.
+            if self.0 > Duration::from_secs(300) {
+                piece!("{secs} s");
+            } else {
+                piece!("{} s", fract(3));
+            }
+        } else if self.0 > Duration::from_millis(1) {
+            piece!("{} ms", fract(2));
+        } else if self.0 > Duration::from_micros(1) {
+            piece!("{} µs", fract(1));
+        } else {
+            piece!("{} ns", fract(0));
+        }
+
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[track_caller]
+    fn test(duration: Duration, expected: &str) {
+        assert_eq!(format_duration(duration).to_string(), expected);
+    }
+
+    #[test]
+    fn test_format_duration() {
+        test(Duration::from_secs(1000000), "11 d 13 h 46 min");
+        test(Duration::from_secs(3600 * 24), "1 d");
+        test(Duration::from_secs(3600), "1 h");
+        test(Duration::from_secs(3600 + 240), "1 h 4 min");
+        test(Duration::from_secs_f64(364.77), "6 min 4 s");
+        test(Duration::from_secs_f64(264.776), "4 min 24.78 s");
+        test(Duration::from_secs(3), "3 s");
+        test(Duration::from_secs_f64(2.8492), "2.85 s");
+        test(Duration::from_micros(734), "734 µs");
+        test(Duration::from_micros(294816), "294.82 ms");
+        test(Duration::from_nanos(1), "1 ns");
+    }
+}