Implement DATE statement

src/eval/command.rs

@@ -66,6 +66,22 @@ impl<'a> CommandState<'a> {
         }
     }
 
+    fn limit_from_until(&self, range: DateRange) -> Option<DateRange> {
+        let range_from = range.from();
+        let from = self
+            .from
+            .filter(|&from| from > range_from)
+            .unwrap_or(range_from);
+
+        let range_until = range.until();
+        let until = self
+            .until
+            .filter(|&until| until < range_until)
+            .unwrap_or(range_until);
+
+        DateRange::new(from, until)
+    }
+
     /// Add an entry, respecting [`Self::from`] and [`Self::until`]. Does not
     /// overwrite existing entries if a root date is specified.
     fn add(&mut self, kind: EntryKind, dates: Option<Dates>) {

src/eval/command/date.rs

@@ -1,10 +1,12 @@
 use chrono::NaiveDate;
 
-use crate::files::commands::{self, Spanned, Time};
+use crate::eval::date::Dates;
+use crate::eval::DateRange;
+use crate::files::commands::{self, Command, Spanned, Time};
 
 use super::super::command::CommandState;
 use super::super::delta::{Delta, DeltaStep};
-use super::super::Result;
+use super::super::{Error, Result};
 
 pub struct DateSpec {
     pub start: NaiveDate,
@@ -52,8 +54,77 @@ impl From<&commands::DateSpec> for DateSpec {
     }
 }
 
-impl<'a> CommandState<'a> {
+impl DateSpec {
-    pub fn eval_date_spec(&mut self, spec: DateSpec) -> Result<()> {
+    fn start_and_range(&self, s: &CommandState<'_>) -> Option<(NaiveDate, DateRange)> {
-        todo!()
+        let (start, range) = match s.command.command {
+            Command::Task(_) => {
+                let last_done = s.last_done();
+                let start = last_done
+                    .filter(|_| self.start_at_done)
+                    .unwrap_or(self.start);
+                let range_from = last_done.map(|date| date.succ()).unwrap_or(self.start);
+                let range = s
+                    .range
+                    .expand_by(&self.end_delta)
+                    .move_by(&self.start_delta)
+                    .with_from(range_from)?;
+                (start, range)
+            }
+            Command::Note(_) => {
+                let start = self.start;
+                let range = s
+                    .range
+                    .expand_by(&self.end_delta)
+                    .move_by(&self.start_delta);
+                (start, range)
+            }
+        };
+        let range = s.limit_from_until(range)?;
+        Some((start, range))
+    }
+
+    fn step(from: NaiveDate, repeat: &Delta) -> Result<NaiveDate> {
+        let to = repeat.apply_date(from)?;
+        if to > from {
+            Ok(to)
+        } else {
+            Err(Error::RepeatDidNotMoveForwards {
+                span: todo!(),
+                from,
+                to,
+            })
+        }
+    }
+
+    fn dates(&self, start: NaiveDate) -> Result<Dates> {
+        let root = self.start_delta.apply_date(start)?;
+        Ok(if let Some(root_time) = self.start_time {
+            let (other, other_time) = self.end_delta.apply_date_time(root, root_time)?;
+            Dates::new_with_time(root, root_time, other, other_time)
+        } else {
+            let other = self.end_delta.apply_date(root)?;
+            Dates::new(root, other)
+        })
+    }
+}
+
+impl<'a> CommandState<'a> {
+    pub fn eval_date_spec(&mut self, spec: DateSpec) -> Result<()> {
+        if let Some(repeat) = &spec.repeat {
+            if let Some((mut start, range)) = spec.start_and_range(self) {
+                while start < range.from() {
+                    start = DateSpec::step(start, repeat)?;
+                }
+                while start <= range.until() {
+                    let dates = spec.dates(start)?;
+                    self.add(self.kind(), Some(dates));
+                    start = DateSpec::step(start, repeat)?;
+                }
+            }
+        } else {
+            let dates = spec.dates(spec.start)?;
+            self.add(self.kind(), Some(dates));
+        }
+        Ok(())
     }
 }

src/eval/delta.rs

@@ -266,11 +266,20 @@ impl Delta {
         self.steps.iter().map(|step| step.value.upper_bound()).sum()
     }
 
-    pub fn apply(&self, start: (NaiveDate, Option<Time>)) -> Result<(NaiveDate, Option<Time>)> {
+    fn apply(&self, start: (NaiveDate, Option<Time>)) -> Result<(NaiveDate, Option<Time>)> {
         let mut eval = DeltaEval::new(start.0, start.1);
         for step in &self.steps {
             eval.apply(step)?;
         }
         Ok((eval.curr, eval.curr_time))
     }
+
+    pub fn apply_date(&self, date: NaiveDate) -> Result<NaiveDate> {
+        Ok(self.apply((date, None))?.0)
+    }
+
+    pub fn apply_date_time(&self, date: NaiveDate, time: Time) -> Result<(NaiveDate, Time)> {
+        let (date, time) = self.apply((date, Some(time)))?;
+        Ok((date, time.expect("time was not preserved")))
+    }
 }

src/eval/error.rs

@@ -18,6 +18,14 @@ pub enum Error {
         start: NaiveDate,
         prev: NaiveDate,
     },
+    /// A `DATE`'s repeat delta did not move the date forwards in time. Instead,
+    /// it either remained at the current date (`to == from`) or moved backwards
+    /// in time (`to < from`).
+    RepeatDidNotMoveForwards {
+        span: Span,
+        from: NaiveDate,
+        to: NaiveDate,
+    },
     /// A `MOVE a TO b` statement was executed, but there was no entry at the
     /// date `a`.
     MoveWithoutSource { span: Span },

src/eval/range.rs

@@ -1,6 +1,9 @@
+use std::cmp;
 use std::ops::RangeInclusive;
 
-use chrono::{Datelike, NaiveDate};
+use chrono::{Datelike, Duration, NaiveDate};
+
+use super::delta::Delta;
 
 #[derive(Debug, Clone, Copy)]
 pub struct DateRange {
@@ -9,9 +12,20 @@ pub struct DateRange {
 }
 
 impl DateRange {
-    pub fn new(from: NaiveDate, until: NaiveDate) -> Self {
+    pub fn new(from: NaiveDate, until: NaiveDate) -> Option<Self> {
-        assert!(from <= until);
+        if from <= until {
-        Self { from, until }
+            Some(Self { from, until })
+        } else {
+            None
+        }
+    }
+
+    pub fn with_from(&self, from: NaiveDate) -> Option<Self> {
+        Self::new(from, self.until)
+    }
+
+    pub fn with_until(&self, until: NaiveDate) -> Option<Self> {
+        Self::new(self.from, until)
     }
 
     pub fn contains(&self, date: NaiveDate) -> bool {
@@ -29,4 +43,33 @@ impl DateRange {
     pub fn years(&self) -> RangeInclusive<i32> {
         self.from.year()..=self.until.year()
     }
+
+    /// Expand the range so that it contains at least all dates from which the
+    /// original range could be reached using `delta`. This new range will
+    /// always contain the old range.
+    pub fn expand_by(&self, delta: &Delta) -> Self {
+        let expand_lower = cmp::min(-delta.upper_bound(), 0);
+        let expand_upper = cmp::max(-delta.lower_bound(), 0);
+        Self::new(
+            self.from + Duration::days(expand_lower.into()),
+            self.until + Duration::days(expand_upper.into()),
+        )
+        // The range is never shrunk, so the new range should always be valid.
+        .expect("expanded range shrunk")
+    }
+
+    /// Return a new range that contains at least all dates from which the
+    /// original range could be reached using `delta`. This new range might not
+    /// contain the old range.
+    pub fn move_by(&self, delta: &Delta) -> Self {
+        let move_lower = -delta.upper_bound();
+        let move_upper = -delta.lower_bound();
+        Self::new(
+            self.from + Duration::days(move_lower.into()),
+            self.until + Duration::days(move_upper.into()),
+        )
+        // The delta's upper bound is greater or equal than its lower bound, so
+        // the range should never become smaller. It can only move and expand.
+        .expect("moved range shrunk")
+    }
 }

src/main.rs

@@ -29,7 +29,8 @@ fn main() -> anyhow::Result<()> {
     let range = DateRange::new(
         NaiveDate::from_ymd(2021, 1, 1),
         NaiveDate::from_ymd(2021, 12, 31),
-    );
+    )
+    .unwrap();
     println!("{:#?}", files.eval(EntryMode::Relevant, range));
 
     files.mark_all_dirty();