sequence: add enumerate()

nested/src/sequence/enumerate.rs

@@ -0,0 +1,86 @@
+use {
+    crate::{
+        core::{Observer, ObserverBroadcast, ObserverExt, OuterViewPort, View, ViewPort},
+        sequence::SequenceView,
+    },
+    std::sync::Arc,
+    std::sync::RwLock,
+};
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+impl<Item: 'static> OuterViewPort<dyn SequenceView<Item = Item>> {
+    pub fn enumerate(&self) -> OuterViewPort<dyn SequenceView<Item = (usize, Item)>> {
+        let port = ViewPort::new();
+        port.add_update_hook(Arc::new(self.0.clone()));
+
+        let map = Arc::new(RwLock::new(EnumerateSequence {
+            src_view: None,
+            cast: port.inner().get_broadcast(),
+        }));
+
+        self.add_observer(map.clone());
+        port.inner().set_view(Some(map));
+        port.into_outer()
+    }
+}
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+pub struct EnumerateSequence<SrcView>
+where
+    SrcView: SequenceView + ?Sized,
+{
+    src_view: Option<Arc<SrcView>>,
+    cast: Arc<RwLock<ObserverBroadcast<dyn SequenceView<Item = (usize, SrcView::Item)>>>>,
+}
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+impl<SrcView> View for EnumerateSequence<SrcView>
+where
+    SrcView: SequenceView + ?Sized,
+{
+    type Msg = usize;
+}
+
+impl<SrcView> SequenceView for EnumerateSequence<SrcView>
+where
+    SrcView: SequenceView + ?Sized
+{
+    type Item = (usize, SrcView::Item);
+
+    fn len(&self) -> Option<usize> {
+        self.src_view.len()
+    }
+
+    fn get(&self, idx: &usize) -> Option<(usize, SrcView::Item)> {
+        self.src_view.get(idx).map(|item| (*idx, item))
+    }
+}
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+impl<SrcView> Observer<SrcView> for EnumerateSequence<SrcView>
+where
+    SrcView: SequenceView + ?Sized
+{
+    fn reset(&mut self, view: Option<Arc<SrcView>>) {
+        let old_len = self.len();
+        self.src_view = view;
+        let new_len = self.len();
+
+        if let Some(len) = old_len {
+            self.cast.notify_each(0..len);
+        }
+        if let Some(len) = new_len {
+            self.cast.notify_each(0..len);
+        }
+    }
+
+    fn notify(&mut self, msg: &usize) {
+        self.cast.notify(msg);
+    }
+}
+
+

nested/src/sequence/mod.rs

@@ -1,5 +1,6 @@
 pub mod filter;
 pub mod map;
+pub mod enumerate;
 pub mod seq2idx;
 pub mod flatten;
 pub mod decorator;