From ff727ea02ce5019d22f407ee872ead26479ffc2a Mon Sep 17 00:00:00 2001
From: Ruben Pollan
Date: Tue, 27 Nov 2018 10:26:54 -0600
Subject: Convert periodic into iterator

---
 src/calendar.rs |  6 +++++-
 src/periodic.rs | 57 ++++++++++++++++++++++++++++++++++++---------------------
 2 files changed, 41 insertions(+), 22 deletions(-)

diff --git a/src/calendar.rs b/src/calendar.rs
index ab465ea..a835480 100644
--- a/src/calendar.rs
+++ b/src/calendar.rs
@@ -65,7 +65,11 @@ impl Calendar {
     pub fn get(&self, first: &Date, last: &Date) -> Vec<Event> {
         let mut events = event::get(&self.single, first, last).to_vec();
         for p in &self.periodic {
-            events.append(&mut p.get(first, last));
+            let mut p_events = p.iter()
+                .skip_while(|e| e.end_date() < *first)
+                .take_while(|e| e.start <= *last)
+                .collect();
+            events.append(&mut p_events);
         }
         events.sort_by_key(|k| k.start);
         events
diff --git a/src/periodic.rs b/src/periodic.rs
index 0c52a9b..d69b817 100644
--- a/src/periodic.rs
+++ b/src/periodic.rs
@@ -49,29 +49,44 @@ impl Periodic {
         Ok(())
     }
 
-    pub fn get(&self, first: &Date, last: &Date) -> Vec<Event> {
-        let mut start = self.event.start;
-        let mut end = self.event.end_date();
-        let mut events = Vec::new();
-        let mut count = 0;
-        while start <= *last {
-            if (self.until.is_some() && start <= self.until.unwrap()) ||
-                (self.count.is_some() && count >= self.count.unwrap())
-            {
-                break;
-            }
+    pub fn iter<'a>(&'a self) -> Iter<'a> {
+        Iter {
+            periodic: self,
+            start: self.event.start,
+            end: self.event.end_date(),
+            count: 0,
+        }
+    }
+}
 
-            if start >= *first {
-                let mut e = self.event.clone();
-                e.start = start;
-                e.end = End::Date(end);
-                events.push(e);
-                count += count;
-            }
-            start = self.freq.next_date(start, self.interval);
-            end = self.freq.next_date(end, self.interval);
+pub struct Iter<'a> {
+    periodic: &'a Periodic,
+    start: Date,
+    end: Date,
+    count: i64,
+}
+
+impl<'a> Iterator for Iter<'a> {
+    type Item = Event;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let p = self.periodic;
+
+        if (p.until.is_some() && self.start <= p.until.unwrap()) ||
+            (p.count.is_some() && self.count >= p.count.unwrap())
+        {
+            return None;
         }
-        events
+
+        let mut event = p.event.clone();
+        event.start = self.start;
+        event.end = End::Date(self.end);
+
+        self.count += 1;
+        self.start = p.freq.next_date(self.start, p.interval);
+        self.end = p.freq.next_date(self.end, p.interval);
+
+        Some(event)
     }
 }
 
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