From e827556c8446b8c770cb800e3dfa950a140f66b8 Mon Sep 17 00:00:00 2001
From: Joscha <joscha@plugh.de>
Date: Thu, 25 Nov 2021 02:32:08 +0100
Subject: [PATCH] Add eval representation of FormulaSpec

---
 src/eval.rs              | 26 ++++++++++++++-
 src/eval/delta.rs        | 55 ++++++++++++++++++++++++++++++--
 src/eval/entry.rs        |  2 +-
 src/eval/formula_spec.rs | 68 ++++++++++++++++++++++++++++++++++++++++
 src/files/commands.rs    | 24 +++++++++++---
 5 files changed, 165 insertions(+), 10 deletions(-)
 create mode 100644 src/eval/formula_spec.rs

diff --git a/src/eval.rs b/src/eval.rs
index 5731879..8ad87fa 100644
--- a/src/eval.rs
+++ b/src/eval.rs
@@ -3,15 +3,18 @@ use std::result;
 
 use chrono::{Datelike, NaiveDate};
 
+use crate::files::commands::DateSpec;
 use crate::files::commands::{Birthday, Command, DoneDate, Note, Spec, Task};
 use crate::files::{Files, Source, SourcedCommand};
 
 use self::entry::EntryMap;
 pub use self::entry::{Entry, EntryKind};
+use self::formula_spec::FormulaSpec;
 pub use self::range::DateRange;
 
 mod delta;
 mod entry;
+mod formula_spec;
 mod range;
 
 #[derive(Debug, thiserror::Error)]
@@ -28,13 +31,34 @@ struct Eval {
 }
 
 impl Eval {
+    fn eval_date_spec(
+        &mut self,
+        spec: &DateSpec,
+        last_done: Option<NaiveDate>,
+        new_entry: impl Fn(Source, Option<DoneDate>) -> Entry,
+    ) -> Result<()> {
+        todo!()
+    }
+
+    fn eval_formula_spec(
+        &mut self,
+        spec: FormulaSpec,
+        new_entry: impl Fn(Source, Option<DoneDate>) -> Entry,
+    ) -> Result<()> {
+        todo!()
+    }
+
     fn eval_spec(
         &mut self,
         spec: &Spec,
         last_done: Option<NaiveDate>,
         new_entry: impl Fn(Source, Option<DoneDate>) -> Entry,
     ) -> Result<()> {
-        todo!()
+        match spec {
+            Spec::Date(spec) => self.eval_date_spec(spec, last_done, new_entry),
+            Spec::Weekday(spec) => self.eval_formula_spec(spec.into(), new_entry),
+            Spec::Formula(spec) => self.eval_formula_spec(spec.into(), new_entry),
+        }
     }
 
     fn eval_dones(&mut self, task: &Task) {
diff --git a/src/eval/delta.rs b/src/eval/delta.rs
index f2d5095..f9ddc05 100644
--- a/src/eval/delta.rs
+++ b/src/eval/delta.rs
@@ -1,8 +1,41 @@
 use std::cmp::Ordering;
 
-use crate::files::commands::{Delta, DeltaStep};
+use crate::files::commands::{self, Time, Weekday};
+
+/// Like [`commands::DeltaStep`] but includes a new constructor,
+/// [`DeltaStep::Time`].
+#[derive(Debug, Clone, Copy)]
+pub enum DeltaStep {
+    Year(i32),
+    Month(i32),
+    MonthReverse(i32),
+    Day(i32),
+    Week(i32),
+    Hour(i32),
+    Minute(i32),
+    Weekday(i32, Weekday),
+    /// Set the time to the next occurrence of the specified time. Useful to
+    /// unify the end delta and end time for different specs.
+    Time(Time),
+}
+
+impl From<commands::DeltaStep> for DeltaStep {
+    fn from(step: commands::DeltaStep) -> Self {
+        match step {
+            commands::DeltaStep::Year(n) => Self::Year(n),
+            commands::DeltaStep::Month(n) => Self::Month(n),
+            commands::DeltaStep::MonthReverse(n) => Self::MonthReverse(n),
+            commands::DeltaStep::Day(n) => Self::Day(n),
+            commands::DeltaStep::Week(n) => Self::Week(n),
+            commands::DeltaStep::Hour(n) => Self::Hour(n),
+            commands::DeltaStep::Minute(n) => Self::Minute(n),
+            commands::DeltaStep::Weekday(n, wd) => Self::Weekday(n, wd),
+        }
+    }
+}
 
 impl DeltaStep {
+    /// A lower bound on days
     fn lower_bound(&self) -> i32 {
         match self {
             DeltaStep::Year(n) => {
@@ -40,9 +73,11 @@ impl DeltaStep {
                 Ordering::Equal => 0,
                 Ordering::Greater => *n * 7 - 7,
             },
+            DeltaStep::Time(_) => 0,
         }
     }
 
+    /// An upper bound on days
     fn upper_bound(&self) -> i32 {
         match self {
             DeltaStep::Year(n) => {
@@ -80,16 +115,30 @@ impl DeltaStep {
                 Ordering::Equal => 0,
                 Ordering::Greater => *n * 7 - 1,
             },
+            DeltaStep::Time(_) => 1,
+        }
+    }
+}
+
+#[derive(Debug, Default)]
+pub struct Delta {
+    pub steps: Vec<DeltaStep>,
+}
+
+impl From<&commands::Delta> for Delta {
+    fn from(delta: &commands::Delta) -> Self {
+        Self {
+            steps: delta.0.iter().map(|&step| step.into()).collect(),
         }
     }
 }
 
 impl Delta {
     pub fn lower_bound(&self) -> i32 {
-        self.0.iter().map(DeltaStep::lower_bound).sum()
+        self.steps.iter().map(DeltaStep::lower_bound).sum()
     }
 
     pub fn upper_bound(&self) -> i32 {
-        self.0.iter().map(DeltaStep::upper_bound).sum()
+        self.steps.iter().map(DeltaStep::upper_bound).sum()
     }
 }
diff --git a/src/eval/entry.rs b/src/eval/entry.rs
index 292a1df..98f8fb9 100644
--- a/src/eval/entry.rs
+++ b/src/eval/entry.rs
@@ -2,7 +2,7 @@ use std::collections::HashMap;
 
 use chrono::NaiveDate;
 
-use crate::files::commands::{DoneDate, Time};
+use crate::files::commands::DoneDate;
 use crate::files::Source;
 
 use super::range::DateRange;
diff --git a/src/eval/formula_spec.rs b/src/eval/formula_spec.rs
new file mode 100644
index 0000000..569c513
--- /dev/null
+++ b/src/eval/formula_spec.rs
@@ -0,0 +1,68 @@
+use crate::files::commands::{self, Expr, Time, Var};
+
+use super::delta::{Delta, DeltaStep};
+
+pub struct FormulaSpec {
+    // TODO Implement more efficient exprs and expr evaluation
+    pub start: Expr,
+    pub start_delta: Delta,
+    pub start_time: Option<Time>,
+    pub end_delta: Delta,
+}
+
+impl From<&commands::FormulaSpec> for FormulaSpec {
+    fn from(spec: &commands::FormulaSpec) -> Self {
+        let start: Expr = spec.start.as_ref().cloned().unwrap_or(Expr::Lit(1));
+
+        let start_delta: Delta = spec
+            .start_delta
+            .as_ref()
+            .map(|delta| delta.into())
+            .unwrap_or_default();
+
+        let mut end_delta: Delta = spec
+            .end_delta
+            .as_ref()
+            .map(|delta| delta.into())
+            .unwrap_or_default();
+        if let Some(time) = spec.end_time {
+            end_delta.steps.push(DeltaStep::Time(time));
+        }
+
+        Self {
+            start,
+            start_delta,
+            start_time: spec.start_time,
+            end_delta,
+        }
+    }
+}
+
+impl From<&commands::WeekdaySpec> for FormulaSpec {
+    fn from(spec: &commands::WeekdaySpec) -> Self {
+        let start = Expr::Eq(
+            Box::new(Expr::Var(Var::Weekday)),
+            Box::new(Expr::Var(spec.start.into())),
+        );
+
+        let mut end_delta = Delta::default();
+        if let Some(wd) = spec.end {
+            end_delta.steps.push(DeltaStep::Weekday(1, wd));
+        }
+        if let Some(delta) = &spec.end_delta {
+            for step in &delta.0 {
+                end_delta.steps.push((*step).into());
+            }
+        }
+        if let Some(time) = spec.end_time {
+            end_delta.steps.push(DeltaStep::Time(time));
+        }
+
+        Self {
+            start,
+            start_delta: Default::default(),
+            start_time: spec.start_time,
+            end_delta,
+        }
+    }
+}
diff --git a/src/files/commands.rs b/src/files/commands.rs
index f47cf60..178c106 100644
--- a/src/files/commands.rs
+++ b/src/files/commands.rs
@@ -1,6 +1,6 @@
 use chrono::NaiveDate;
 
-#[derive(Debug, Clone, Copy)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
 pub struct Time {
     pub hour: u8,
     pub min: u8,
@@ -44,7 +44,7 @@ impl Weekday {
     }
 }
 
-#[derive(Debug)]
+#[derive(Debug, Clone, Copy)]
 pub enum DeltaStep {
     /// `y`, move by a year, keeping the same month and day
     Year(i32),
@@ -94,7 +94,7 @@ impl DeltaStep {
     }
 }
 
-#[derive(Debug)]
+#[derive(Debug, Default)]
 pub struct Delta(pub Vec<DeltaStep>);
 
 #[derive(Debug)]
@@ -125,7 +125,7 @@ pub struct WeekdaySpec {
     pub end_time: Option<Time>,
 }
 
-#[derive(Debug)]
+#[derive(Debug, Clone, Copy)]
 pub enum Var {
     /// `true`, always 1
     True,
@@ -243,7 +243,21 @@ impl Var {
     }
 }
 
-#[derive(Debug)]
+impl From<Weekday> for Var {
+    fn from(wd: Weekday) -> Self {
+        match wd {
+            Weekday::Monday => Self::Monday,
+            Weekday::Tuesday => Self::Tuesday,
+            Weekday::Wednesday => Self::Wednesday,
+            Weekday::Thursday => Self::Thursday,
+            Weekday::Friday => Self::Friday,
+            Weekday::Saturday => Self::Saturday,
+            Weekday::Sunday => Self::Sunday,
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
 pub enum Expr {
     Lit(i64),
     Var(Var),