Duration type, simple date-duration-calculations and comparisons (#1843)

8 files changed, 350 insertions, 23 deletions

diff --git a/crates/typst-library/src/compute/construct.rs b/crates/typst-library/src/compute/construct.rs
index 23f0c225..cee021bf 100644
--- a/crates/typst-library/src/compute/construct.rs
+++ b/crates/typst-library/src/compute/construct.rs
@@ -3,7 +3,7 @@ use std::str::FromStr;
 
 use time::{Month, PrimitiveDateTime};
 
-use typst::eval::{Bytes, Datetime, Module, Plugin, Reflect, Regex};
+use typst::eval::{Bytes, Datetime, Duration, Module, Plugin, Reflect, Regex};
 
 use crate::prelude::*;
 
@@ -334,6 +334,54 @@ pub fn datetime_today(
         .ok_or("unable to get the current date")?)
 }
 
+/// Creates a new duration.
+///
+/// You can specify the [duration]($type/duration) using weeks, days, hours,
+/// minutes and seconds. You can also get a duration by subtracting two
+/// [datetimes]($type/datetime).
+///
+/// ## Example
+/// ```example
+/// #duration(
+///   days: 3,
+///   hours: 12,
+/// ).hours()
+/// ```
+///
+/// Display: Duration
+/// Category: construct
+#[func]
+pub fn duration(
+    /// The number of seconds.
+    #[named]
+    #[default(0)]
+    seconds: i64,
+    /// The number of minutes.
+    #[named]
+    #[default(0)]
+    minutes: i64,
+    /// The number of hours.
+    #[named]
+    #[default(0)]
+    hours: i64,
+    /// The number of days.
+    #[named]
+    #[default(0)]
+    days: i64,
+    /// The number of weeks.
+    #[named]
+    #[default(0)]
+    weeks: i64,
+) -> Duration {
+    Duration::from(
+        time::Duration::seconds(seconds)
+            + time::Duration::minutes(minutes)
+            + time::Duration::hours(hours)
+            + time::Duration::days(days)
+            + time::Duration::weeks(weeks),
+    )
+}
+
 /// Creates a CMYK color.
 ///
 /// This is useful if you want to target a specific printer. The conversion
diff --git a/crates/typst-library/src/compute/mod.rs b/crates/typst-library/src/compute/mod.rs
index 5e7e8d46..599ac72f 100644
--- a/crates/typst-library/src/compute/mod.rs
+++ b/crates/typst-library/src/compute/mod.rs
@@ -25,6 +25,7 @@ pub(super) fn define(global: &mut Scope) {
     global.define("cmyk", cmyk_func());
     global.define("color", color_module());
     global.define("datetime", datetime_func());
+    global.define("duration", duration_func());
     global.define("symbol", symbol_func());
     global.define("str", str_func());
     global.define("bytes", bytes_func());
diff --git a/crates/typst/src/eval/datetime.rs b/crates/typst/src/eval/datetime.rs
index f3c4a5a1..96127e9d 100644
--- a/crates/typst/src/eval/datetime.rs
+++ b/crates/typst/src/eval/datetime.rs
@@ -1,17 +1,20 @@
+use std::cmp::Ordering;
 use std::fmt;
 use std::fmt::{Debug, Formatter};
 use std::hash::Hash;
+use std::ops::{Add, Sub};
 
 use ecow::{eco_format, EcoString, EcoVec};
 use time::error::{Format, InvalidFormatDescription};
 use time::{format_description, PrimitiveDateTime};
 
-use crate::eval::cast;
+use crate::diag::bail;
+use crate::eval::{Duration, StrResult};
 use crate::util::pretty_array_like;
 
 /// A datetime object that represents either a date, a time or a combination of
 /// both.
-#[derive(Clone, Copy, PartialEq, Hash)]
+#[derive(Copy, Clone, Eq, PartialEq, Hash)]
 pub enum Datetime {
     /// Representation as a date.
     Date(time::Date),
@@ -22,6 +25,15 @@ pub enum Datetime {
 }
 
 impl Datetime {
+    /// Which kind of variant this datetime stores.
+    pub fn kind(&self) -> &'static str {
+        match self {
+            Datetime::Datetime(_) => "datetime",
+            Datetime::Date(_) => "date",
+            Datetime::Time(_) => "time",
+        }
+    }
+
     /// Display the date and/or time in a certain format.
     pub fn display(&self, pattern: Option<EcoString>) -> Result<EcoString, EcoString> {
         let pattern = pattern.as_ref().map(EcoString::as_str).unwrap_or(match self {
@@ -106,6 +118,15 @@ impl Datetime {
         }
     }
 
+    /// Return the ordinal (day of the year), if existing.
+    pub fn ordinal(&self) -> Option<u16> {
+        match self {
+            Datetime::Datetime(datetime) => Some(datetime.ordinal()),
+            Datetime::Date(date) => Some(date.ordinal()),
+            Datetime::Time(_) => None,
+        }
+    }
+
     /// Create a datetime from year, month, and day.
     pub fn from_ymd(year: i32, month: u8, day: u8) -> Option<Self> {
         Some(Datetime::Date(
@@ -136,6 +157,56 @@ impl Datetime {
     }
 }
 
+impl PartialOrd for Datetime {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        match (self, other) {
+            (Datetime::Datetime(a), Datetime::Datetime(b)) => a.partial_cmp(b),
+            (Datetime::Date(a), Datetime::Date(b)) => a.partial_cmp(b),
+            (Datetime::Time(a), Datetime::Time(b)) => a.partial_cmp(b),
+            _ => None,
+        }
+    }
+}
+
+impl Add<Duration> for Datetime {
+    type Output = Datetime;
+
+    fn add(self, rhs: Duration) -> Self::Output {
+        let rhs: time::Duration = rhs.into();
+        match self {
+            Datetime::Datetime(datetime) => Self::Datetime(datetime + rhs),
+            Datetime::Date(date) => Self::Date(date + rhs),
+            Datetime::Time(time) => Self::Time(time + rhs),
+        }
+    }
+}
+
+impl Sub<Duration> for Datetime {
+    type Output = Datetime;
+
+    fn sub(self, rhs: Duration) -> Self::Output {
+        let rhs: time::Duration = rhs.into();
+        match self {
+            Datetime::Datetime(datetime) => Self::Datetime(datetime - rhs),
+            Datetime::Date(date) => Self::Date(date - rhs),
+            Datetime::Time(time) => Self::Time(time - rhs),
+        }
+    }
+}
+
+impl Sub for Datetime {
+    type Output = StrResult<Duration>;
+
+    fn sub(self, rhs: Self) -> Self::Output {
+        match (self, rhs) {
+            (Datetime::Datetime(a), Datetime::Datetime(b)) => Ok((a - b).into()),
+            (Datetime::Date(a), Datetime::Date(b)) => Ok((a - b).into()),
+            (Datetime::Time(a), Datetime::Time(b)) => Ok((a - b).into()),
+            (a, b) => bail!("cannot subtract {} from {}", b.kind(), a.kind()),
+        }
+    }
+}
+
 impl Debug for Datetime {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         let year = self.year().map(|y| eco_format!("year: {y}"));
@@ -153,10 +224,6 @@ impl Debug for Datetime {
     }
 }
 
-cast! {
-    type Datetime: "datetime",
-}
-
 /// Format the `Format` error of the time crate in an appropriate way.
 fn format_time_format_error(error: Format) -> EcoString {
     match error {
diff --git a/crates/typst/src/eval/duration.rs b/crates/typst/src/eval/duration.rs
new file mode 100644
index 00000000..500ce209
--- /dev/null
+++ b/crates/typst/src/eval/duration.rs
@@ -0,0 +1,140 @@
+use crate::util::pretty_array_like;
+use ecow::eco_format;
+use std::fmt;
+use std::fmt::{Debug, Formatter};
+use std::ops::{Add, Div, Mul, Neg, Sub};
+use time::ext::NumericalDuration;
+
+/// Represents a positive or negative span of time.
+#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
+pub struct Duration(time::Duration);
+
+impl Duration {
+    /// Whether the duration is empty / zero.
+    pub fn is_zero(&self) -> bool {
+        self.0.is_zero()
+    }
+
+    /// The duration expressed in seconds.
+    pub fn seconds(&self) -> f64 {
+        self.0.as_seconds_f64()
+    }
+
+    /// The duration expressed in minutes.
+    pub fn minutes(&self) -> f64 {
+        self.seconds() / 60.0
+    }
+
+    /// The duration expressed in hours.
+    pub fn hours(&self) -> f64 {
+        self.seconds() / 3_600.0
+    }
+
+    /// The duration expressed in days.
+    pub fn days(&self) -> f64 {
+        self.seconds() / 86_400.0
+    }
+
+    /// The duration expressed in weeks.
+    pub fn weeks(&self) -> f64 {
+        self.seconds() / 604_800.0
+    }
+}
+
+impl From<time::Duration> for Duration {
+    fn from(value: time::Duration) -> Self {
+        Self(value)
+    }
+}
+
+impl Debug for Duration {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        let mut tmp = self.0;
+        let mut vec = Vec::with_capacity(5);
+
+        let weeks = tmp.whole_seconds() / 604_800.0 as i64;
+        if weeks != 0 {
+            vec.push(eco_format!("weeks: {weeks}"));
+        }
+        tmp -= weeks.weeks();
+
+        let days = tmp.whole_days();
+        if days != 0 {
+            vec.push(eco_format!("days: {days}"));
+        }
+        tmp -= days.days();
+
+        let hours = tmp.whole_hours();
+        if hours != 0 {
+            vec.push(eco_format!("hours: {hours}"));
+        }
+        tmp -= hours.hours();
+
+        let minutes = tmp.whole_minutes();
+        if minutes != 0 {
+            vec.push(eco_format!("minutes: {minutes}"));
+        }
+        tmp -= minutes.minutes();
+
+        let seconds = tmp.whole_seconds();
+        if seconds != 0 {
+            vec.push(eco_format!("seconds: {seconds}"));
+        }
+
+        write!(f, "duration{}", &pretty_array_like(&vec, false))
+    }
+}
+
+impl From<Duration> for time::Duration {
+    fn from(value: Duration) -> Self {
+        value.0
+    }
+}
+
+impl Add for Duration {
+    type Output = Duration;
+
+    fn add(self, rhs: Self) -> Self::Output {
+        Duration(self.0 + rhs.0)
+    }
+}
+
+impl Sub for Duration {
+    type Output = Duration;
+
+    fn sub(self, rhs: Self) -> Self::Output {
+        Duration(self.0 - rhs.0)
+    }
+}
+
+impl Neg for Duration {
+    type Output = Duration;
+
+    fn neg(self) -> Self::Output {
+        Duration(-self.0)
+    }
+}
+
+impl Mul<f64> for Duration {
+    type Output = Duration;
+
+    fn mul(self, rhs: f64) -> Self::Output {
+        Duration(self.0 * rhs)
+    }
+}
+
+impl Div<f64> for Duration {
+    type Output = Duration;
+
+    fn div(self, rhs: f64) -> Self::Output {
+        Duration(self.0 / rhs)
+    }
+}
+
+impl Div for Duration {
+    type Output = f64;
+
+    fn div(self, rhs: Self) -> Self::Output {
+        self.0 / rhs.0
+    }
+}
diff --git a/crates/typst/src/eval/methods.rs b/crates/typst/src/eval/methods.rs
index ed11d8a7..018e80b0 100644
--- a/crates/typst/src/eval/methods.rs
+++ b/crates/typst/src/eval/methods.rs
@@ -4,7 +4,7 @@ use ecow::{eco_format, EcoString};
 
 use super::{Args, Bytes, IntoValue, Plugin, Str, Value, Vm};
 use crate::diag::{At, Hint, SourceResult};
-use crate::eval::{bail, Datetime};
+use crate::eval::bail;
 use crate::geom::{Align, Axes, Color, Dir, Em, GenAlign};
 use crate::model::{Location, Selector};
 use crate::syntax::Span;
@@ -107,6 +107,28 @@ pub fn call(
             _ => return missing(),
         },
 
+        Value::Datetime(datetime) => match method {
+            "display" => datetime.display(args.eat()?).at(args.span)?.into_value(),
+            "year" => datetime.year().into_value(),
+            "month" => datetime.month().into_value(),
+            "weekday" => datetime.weekday().into_value(),
+            "day" => datetime.day().into_value(),
+            "hour" => datetime.hour().into_value(),
+            "minute" => datetime.minute().into_value(),
+            "second" => datetime.second().into_value(),
+            "ordinal" => datetime.ordinal().into_value(),
+            _ => return missing(),
+        },
+
+        Value::Duration(duration) => match method {
+            "seconds" => duration.seconds().into_value(),
+            "minutes" => duration.minutes().into_value(),
+            "hours" => duration.hours().into_value(),
+            "days" => duration.days().into_value(),
+            "weeks" => duration.weeks().into_value(),
+            _ => return missing(),
+        },
+
         Value::Content(content) => match method {
             "func" => content.func().into_value(),
             "has" => content.has(&args.expect::<EcoString>("field")?).into_value(),
@@ -257,20 +279,6 @@ pub fn call(
                     }
                     _ => return missing(),
                 }
-            } else if let Some(&datetime) = dynamic.downcast::<Datetime>() {
-                match method {
-                    "display" => {
-                        datetime.display(args.eat()?).at(args.span)?.into_value()
-                    }
-                    "year" => datetime.year().into_value(),
-                    "month" => datetime.month().into_value(),
-                    "weekday" => datetime.weekday().into_value(),
-                    "day" => datetime.day().into_value(),
-                    "hour" => datetime.hour().into_value(),
-                    "minute" => datetime.minute().into_value(),
-                    "second" => datetime.second().into_value(),
-                    _ => return missing(),
-                }
             } else if let Some(direction) = dynamic.downcast::<Dir>() {
                 match method {
                     "axis" => direction.axis().description().into_value(),
@@ -426,6 +434,24 @@ pub fn methods_on(type_name: &str) -> &[(&'static str, bool)] {
             ("trim", true),
         ],
         "bytes" => &[("len", false), ("at", true), ("slice", true)],
+        "datetime" => &[
+            ("display", true),
+            ("year", false),
+            ("month", false),
+            ("weekday", false),
+            ("day", false),
+            ("hour", false),
+            ("minute", false),
+            ("second", false),
+            ("ordinal", false),
+        ],
+        "duration" => &[
+            ("seconds", false),
+            ("minutes", false),
+            ("hours", false),
+            ("days", false),
+            ("weeks", false),
+        ],
         "content" => &[
             ("func", false),
             ("has", true),
diff --git a/crates/typst/src/eval/mod.rs b/crates/typst/src/eval/mod.rs
index 63eed5ac..706f6b01 100644
--- a/crates/typst/src/eval/mod.rs
+++ b/crates/typst/src/eval/mod.rs
@@ -16,6 +16,7 @@ mod args;
 mod auto;
 mod bytes;
 mod datetime;
+mod duration;
 mod fields;
 mod func;
 mod int;
@@ -48,6 +49,7 @@ pub use self::cast::{
 };
 pub use self::datetime::Datetime;
 pub use self::dict::{dict, Dict};
+pub use self::duration::Duration;
 pub use self::fields::fields_on;
 pub use self::func::{Func, FuncInfo, NativeFunc, ParamInfo};
 pub use self::library::{set_lang_items, LangItems, Library};
diff --git a/crates/typst/src/eval/ops.rs b/crates/typst/src/eval/ops.rs
index f57f743f..2dc3c8f9 100644
--- a/crates/typst/src/eval/ops.rs
+++ b/crates/typst/src/eval/ops.rs
@@ -62,6 +62,7 @@ pub fn neg(value: Value) -> StrResult<Value> {
         Ratio(v) => Ratio(-v),
         Relative(v) => Relative(-v),
         Fraction(v) => Fraction(-v),
+        Duration(v) => Duration(-v),
         v => mismatch!("cannot apply '-' to {}", v),
     })
 }
@@ -115,6 +116,10 @@ pub fn add(lhs: Value, rhs: Value) -> StrResult<Value> {
             })
         }
 
+        (Duration(a), Duration(b)) => Duration(a + b),
+        (Datetime(a), Duration(b)) => Datetime(a + b),
+        (Duration(a), Datetime(b)) => Datetime(b + a),
+
         (Dyn(a), Dyn(b)) => {
             // 1D alignments can be summed into 2D alignments.
             if let (Some(&a), Some(&b)) =
@@ -161,6 +166,10 @@ pub fn sub(lhs: Value, rhs: Value) -> StrResult<Value> {
 
         (Fraction(a), Fraction(b)) => Fraction(a - b),
 
+        (Duration(a), Duration(b)) => Duration(a - b),
+        (Datetime(a), Duration(b)) => Datetime(a - b),
+        (Datetime(a), Datetime(b)) => Duration((a - b)?),
+
         (a, b) => mismatch!("cannot subtract {1} from {0}", a, b),
     })
 }
@@ -214,6 +223,11 @@ pub fn mul(lhs: Value, rhs: Value) -> StrResult<Value> {
         (Content(a), b @ Int(_)) => Content(a.repeat(b.cast()?)),
         (a @ Int(_), Content(b)) => Content(b.repeat(a.cast()?)),
 
+        (Int(a), Duration(b)) => Duration(b * (a as f64)),
+        (Float(a), Duration(b)) => Duration(b * a),
+        (Duration(a), Int(b)) => Duration(a * (b as f64)),
+        (Duration(a), Float(b)) => Duration(a * b),
+
         (a, b) => mismatch!("cannot multiply {} with {}", a, b),
     })
 }
@@ -254,6 +268,10 @@ pub fn div(lhs: Value, rhs: Value) -> StrResult<Value> {
         (Fraction(a), Float(b)) => Fraction(a / b),
         (Fraction(a), Fraction(b)) => Float(a / b),
 
+        (Duration(a), Int(b)) => Duration(a / (b as f64)),
+        (Duration(a), Float(b)) => Duration(a / b),
+        (Duration(a), Duration(b)) => Float(a / b),
+
         (a, b) => mismatch!("cannot divide {} by {}", a, b),
     })
 }
@@ -268,6 +286,7 @@ fn is_zero(v: &Value) -> bool {
         Ratio(v) => v.is_zero(),
         Relative(v) => v.is_zero(),
         Fraction(v) => v.is_zero(),
+        Duration(v) => v.is_zero(),
         _ => false,
     }
 }
@@ -357,6 +376,8 @@ pub fn equal(lhs: &Value, rhs: &Value) -> bool {
         (Func(a), Func(b)) => a == b,
         (Args(a), Args(b)) => a == b,
         (Module(a), Module(b)) => a == b,
+        (Datetime(a), Datetime(b)) => a == b,
+        (Duration(a), Duration(b)) => a == b,
         (Dyn(a), Dyn(b)) => a == b,
 
         // Some technically different things should compare equal.
@@ -392,6 +413,9 @@ pub fn compare(lhs: &Value, rhs: &Value) -> StrResult<Ordering> {
         (Relative(a), Length(b)) if a.rel.is_zero() => try_cmp_values(&a.abs, b)?,
         (Relative(a), Ratio(b)) if a.abs.is_zero() => a.rel.cmp(b),
 
+        (Duration(a), Duration(b)) => a.cmp(b),
+        (Datetime(a), Datetime(b)) => try_cmp_datetimes(a, b)?,
+
         _ => mismatch!("cannot compare {} and {}", lhs, rhs),
     })
 }
@@ -402,6 +426,12 @@ fn try_cmp_values<T: PartialOrd + Debug>(a: &T, b: &T) -> StrResult<Ordering> {
         .ok_or_else(|| eco_format!("cannot compare {:?} with {:?}", a, b))
 }
 
+/// Try to compare two datetimes.
+fn try_cmp_datetimes(a: &super::Datetime, b: &super::Datetime) -> StrResult<Ordering> {
+    a.partial_cmp(b)
+        .ok_or_else(|| eco_format!("cannot compare {} and {}", a.kind(), b.kind()))
+}
+
 /// Test whether one value is "in" another one.
 pub fn in_(lhs: Value, rhs: Value) -> StrResult<Value> {
     if let Some(b) = contains(&lhs, &rhs) {
diff --git a/crates/typst/src/eval/value.rs b/crates/typst/src/eval/value.rs
index 759f55f0..4e870ab4 100644
--- a/crates/typst/src/eval/value.rs
+++ b/crates/typst/src/eval/value.rs
@@ -10,6 +10,7 @@ use serde::de::{Error, MapAccess, SeqAccess, Visitor};
 use serde::{Deserialize, Deserializer, Serialize, Serializer};
 use siphasher::sip128::{Hasher128, SipHasher13};
 use time::macros::format_description;
+use typst::eval::Duration;
 
 use super::{
     cast, fields, format_str, ops, Args, Array, Bytes, CastInfo, Content, Dict,
@@ -55,6 +56,10 @@ pub enum Value {
     Bytes(Bytes),
     /// A label: `<intro>`.
     Label(Label),
+    /// A datetime
+    Datetime(Datetime),
+    /// A duration
+    Duration(Duration),
     /// A content value: `[*Hi* there]`.
     Content(Content),
     // Content styles.
@@ -116,6 +121,8 @@ impl Value {
             Self::Str(_) => Str::TYPE_NAME,
             Self::Bytes(_) => Bytes::TYPE_NAME,
             Self::Label(_) => Label::TYPE_NAME,
+            Self::Datetime(_) => Datetime::TYPE_NAME,
+            Self::Duration(_) => Duration::TYPE_NAME,
             Self::Content(_) => Content::TYPE_NAME,
             Self::Styles(_) => Styles::TYPE_NAME,
             Self::Array(_) => Array::TYPE_NAME,
@@ -200,6 +207,8 @@ impl Debug for Value {
             Self::Str(v) => Debug::fmt(v, f),
             Self::Bytes(v) => Debug::fmt(v, f),
             Self::Label(v) => Debug::fmt(v, f),
+            Self::Datetime(v) => Debug::fmt(v, f),
+            Self::Duration(v) => Debug::fmt(v, f),
             Self::Content(v) => Debug::fmt(v, f),
             Self::Styles(v) => Debug::fmt(v, f),
             Self::Array(v) => Debug::fmt(v, f),
@@ -245,6 +254,8 @@ impl Hash for Value {
             Self::Label(v) => v.hash(state),
             Self::Content(v) => v.hash(state),
             Self::Styles(v) => v.hash(state),
+            Self::Datetime(v) => v.hash(state),
+            Self::Duration(v) => v.hash(state),
             Self::Array(v) => v.hash(state),
             Self::Dict(v) => v.hash(state),
             Self::Func(v) => v.hash(state),
@@ -435,7 +446,7 @@ impl<'de> Visitor<'de> for ValueVisitor {
         let dict = Dict::deserialize(MapAccessDeserializer::new(map))?;
         Ok(match parse_toml_date(&dict) {
             None => dict.into_value(),
-            Some(dt) => Value::dynamic(dt),
+            Some(datetime) => datetime.into_value(),
         })
     }
 }
@@ -610,6 +621,8 @@ primitive! {
 }
 primitive! { Bytes: "bytes", Bytes }
 primitive! { Label: "label", Label }
+primitive! { Datetime: "datetime", Datetime }
+primitive! { Duration: "duration", Duration }
 primitive! { Content: "content",
     Content,
     None => Content::empty(),