Add support for loop.last

1 files changed, 48 insertions, 0 deletions

diff --git a/askama_shared/src/helpers/mod.rs b/askama_shared/src/helpers/mod.rs
new file mode 100644
index 0000000..1a3fd7b
--- /dev/null
+++ b/askama_shared/src/helpers/mod.rs
@@ -0,0 +1,48 @@
+use std::iter::Peekable;
+
+pub struct Enumerate<I>
+where
+    I: Iterator,
+{
+    iter: Peekable<I>,
+    count: usize,
+}
+
+impl<I> Iterator for Enumerate<I>
+where
+    I: Iterator,
+{
+    type Item = (usize, bool, <I as Iterator>::Item);
+
+    #[inline]
+    fn next(&mut self) -> Option<(usize, bool, <I as Iterator>::Item)> {
+        self.iter.next().map(|a| {
+            let last = self.iter.peek().is_none();
+            let ret = (self.count, last, a);
+            // Possible undefined overflow.
+            self.count += 1;
+            ret
+        })
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iter.size_hint()
+    }
+
+    #[inline]
+    fn count(self) -> usize {
+        self.iter.count()
+    }
+}
+
+#[inline]
+pub fn enumerate<I>(iter: I) -> Enumerate<I>
+where
+    I: Iterator,
+{
+    Enumerate {
+        iter: iter.peekable(),
+        count: 0,
+    }
+}