1 files changed, 145 insertions, 7 deletions

diff --git a/src/model/repetition.rs b/src/model/repetition.rs
index 80387d9..ceb903b 100644
--- a/src/model/repetition.rs
+++ b/src/model/repetition.rs
@@ -1,21 +1,19 @@
-use chrono::Weekday;
+use chrono::{Datelike, Duration, NaiveDate, Weekday};
 use serde::{Deserialize, Serialize};
 
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
 pub enum Repetition {
-    Daily { frequency: u8 },
-    Monthly { frequency: MonthFrequency },
+    Daily { period: u8 },
+    Monthly { day: DayOfMonth },
     Yearly,
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
-pub enum MonthFrequency {
+pub enum DayOfMonth {
     Day { day: u8 },
-    FirstDay { day: Weekday },
+    Weekday { weekday: Weekday },
 }
 
-// Validation
-
 pub fn validate_day(str: &str) -> Option<u8> {
     let n = str.parse::<u8>().ok()?;
     if n >= 1 && n <= 31 {
@@ -24,3 +22,143 @@ pub fn validate_day(str: &str) -> Option<u8> {
         None
     }
 }
+
+impl Repetition {
+    pub fn between(&self, event: NaiveDate, start: NaiveDate, end: NaiveDate) -> Vec<NaiveDate> {
+        let repeat = |mut date, next: Box<dyn Fn(NaiveDate) -> NaiveDate>| {
+            let mut repetitions = vec![];
+            while date <= end {
+                if date >= event && date >= start {
+                    repetitions.push(date)
+                }
+                date = next(date)
+            }
+            repetitions
+        };
+
+        match self {
+            Repetition::Daily { period } => {
+                let n = start.signed_duration_since(event).num_days() % (*period as i64);
+                let duration = Duration::days(*period as i64);
+                repeat(start - Duration::days(n), Box::new(|d| d + duration))
+            }
+            Repetition::Monthly {
+                day: DayOfMonth::Day { day },
+            } => match start.with_day(*day as u32) {
+                Some(first_repetition) => repeat(first_repetition, Box::new(next_month)),
+                None => vec![],
+            },
+            Repetition::Monthly {
+                day: DayOfMonth::Weekday { weekday },
+            } => repeat(
+                first_weekday_of_month(start, *weekday),
+                Box::new(|d| first_weekday_of_month(next_month(d), *weekday)),
+            ),
+            Repetition::Yearly => repeat(
+                NaiveDate::from_ymd(start.year(), event.month(), event.day()),
+                Box::new(|d| NaiveDate::from_ymd(d.year() + 1, d.month(), d.day())),
+            ),
+        }
+    }
+}
+
+fn first_weekday_of_month(date: NaiveDate, weekday: Weekday) -> NaiveDate {
+    NaiveDate::from_weekday_of_month(date.year(), date.month(), weekday, 1)
+}
+
+fn next_month(date: NaiveDate) -> NaiveDate {
+    if date.month() == 12 {
+        NaiveDate::from_ymd(date.year() + 1, 1, date.day())
+    } else {
+        NaiveDate::from_ymd(date.year(), date.month() + 1, date.day())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn every_day_event_before() {
+        let repetition = Repetition::Daily { period: 1 };
+        assert_eq!(
+            repetition.between(d(2022, 6, 1), d(2022, 7, 1), d(2022, 8, 31)),
+            d(2022, 7, 1)
+                .iter_days()
+                .take(62)
+                .collect::<Vec<NaiveDate>>()
+        )
+    }
+
+    #[test]
+    fn every_day_event_between() {
+        let repetition = Repetition::Daily { period: 1 };
+        assert_eq!(
+            repetition.between(d(2022, 8, 10), d(2022, 7, 1), d(2022, 8, 31)),
+            d(2022, 8, 10)
+                .iter_days()
+                .take(22)
+                .collect::<Vec<NaiveDate>>()
+        )
+    }
+
+    #[test]
+    fn every_day_event_after() {
+        let repetition = Repetition::Daily { period: 1 };
+        assert!(repetition
+            .between(d(2022, 9, 1), d(2022, 7, 1), d(2022, 8, 31))
+            .is_empty())
+    }
+
+    #[test]
+    fn every_three_days() {
+        let repetition = Repetition::Daily { period: 3 };
+        assert_eq!(
+            repetition.between(d(2022, 2, 16), d(2022, 2, 21), d(2022, 3, 6)),
+            vec!(
+                d(2022, 2, 22),
+                d(2022, 2, 25),
+                d(2022, 2, 28),
+                d(2022, 3, 3),
+                d(2022, 3, 6)
+            )
+        )
+    }
+
+    #[test]
+    fn day_of_month() {
+        let repetition = Repetition::Monthly {
+            day: DayOfMonth::Day { day: 8 },
+        };
+        assert_eq!(
+            repetition.between(d(2022, 2, 7), d(2022, 1, 1), d(2022, 4, 7)),
+            vec!(d(2022, 2, 8), d(2022, 3, 8))
+        )
+    }
+
+    #[test]
+    fn weekday_of_month() {
+        let repetition = Repetition::Monthly {
+            day: DayOfMonth::Weekday {
+                weekday: Weekday::Tue,
+            },
+        };
+        assert_eq!(
+            repetition.between(d(2022, 1, 5), d(2022, 1, 1), d(2022, 4, 4)),
+            vec!(d(2022, 2, 1), d(2022, 3, 1))
+        )
+    }
+
+    #[test]
+    fn yearly() {
+        let repetition = Repetition::Yearly;
+        assert_eq!(
+            repetition.between(d(2020, 5, 5), d(2018, 1, 1), d(2022, 5, 5)),
+            vec!(d(2020, 5, 5), d(2021, 5, 5), d(2022, 5, 5))
+        )
+    }
+
+    fn d(y: i32, m: u32, d: u32) -> NaiveDate {
+        NaiveDate::from_ymd(y, m, d)
+    }
+}