make SequenceView a separate trait which can be converted into an IndexView with a projection

src/sequence/mod.rs

@@ -1,8 +1,52 @@
-use crate::index::IndexView;
+
+pub mod seq2idx;
+pub mod vec_buffer;
+
+pub use {
+    seq2idx::{Sequence2Index},
+    vec_buffer::{VecBuffer, VecSequence}
+};
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
 
-pub trait SequenceView = IndexView<usize>;
+use crate::core::View;
+
+pub trait SequenceView : View<Msg = usize> {
+    type Item;
+
+    fn get(&self, idx: usize) -> Self::Item;
+    fn len(&self) -> Option<usize>;
+}
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
 
+use std::{
+    sync::{Arc, RwLock},
+    ops::{Deref}
+};
+
+impl<V: SequenceView> SequenceView for RwLock<V> {
+    type Item = V::Item;
+
+    fn get(&self, idx: usize) -> Self::Item {
+        self.read().unwrap().get(idx)
+    }
+
+    fn len(&self) -> Option<usize> {
+        self.read().unwrap().len()
+    }
+}
+
+impl<V: SequenceView> SequenceView for Arc<V> {
+    type Item = V::Item;
+
+    fn get(&self, idx: usize) -> Self::Item {
+        self.deref().get(idx)
+    }
+
+    fn len(&self) -> Option<usize> {
+        self.deref().len()
+    }
+}
+
+

src/sequence/seq2idx.rs

@@ -0,0 +1,90 @@
+use {
+    std::{
+        sync::{Arc, RwLock},
+        boxed::Box
+    },
+    crate::{
+        core::{
+            View, Observer, ObserverExt, ObserverBroadcast,
+            ViewPort, InnerViewPort, OuterViewPort
+        },
+        sequence::SequenceView,
+        index::IndexView
+    }
+};
+
+/// Transforms a SequenceView into IndexView<usize>
+pub struct Sequence2Index<SrcView>
+where SrcView: SequenceView + ?Sized + 'static {
+    src_view: Option<Arc<SrcView>>,
+    cast: Arc<RwLock<ObserverBroadcast<dyn IndexView<usize, Item = Option<SrcView::Item>>>>>
+}
+
+impl<SrcView> Sequence2Index<SrcView>
+where SrcView: SequenceView + ?Sized + 'static {
+    pub fn new(
+        port: InnerViewPort<dyn IndexView<usize, Item = Option<SrcView::Item>>>
+    ) -> Arc<RwLock<Self>> {
+        let s2i = Arc::new(RwLock::new(
+            Sequence2Index {
+                src_view: None,
+                cast: port.get_broadcast()
+            }
+        ));
+        port.set_view(Some(s2i.clone()));
+        s2i
+    }
+}
+
+impl<Item: 'static> OuterViewPort<dyn SequenceView<Item = Item>> {
+    pub fn to_index(&self) -> OuterViewPort<dyn IndexView<usize, Item = Option<Item>>> {
+        let port = ViewPort::new();
+        self.add_observer(Sequence2Index::new(port.inner()));
+        port.into_outer()
+    }
+}
+
+impl<SrcView> View for Sequence2Index<SrcView>
+where SrcView: SequenceView + ?Sized + 'static {
+    type Msg = usize;
+}
+
+impl<SrcView> IndexView<usize> for Sequence2Index<SrcView>
+where SrcView: SequenceView + ?Sized + 'static {
+    type Item = Option<SrcView::Item>;
+
+    fn get(&self, key: &usize) -> Self::Item {
+        if let Some(v) = self.src_view.as_ref() {
+            if *key < v.len().unwrap_or(usize::MAX) {
+                return Some(v.get(*key));
+            }
+        }
+        None
+    }
+
+    fn area(&self) -> Option<Vec<usize>> {
+        if let Some(v) = self.src_view.as_ref() {
+            if let Some(len) = v.len() {
+                return Some((0 .. len).collect());
+            }
+        }
+        None
+    }
+}
+
+impl<SrcView> Observer<SrcView> for Sequence2Index<SrcView>
+where SrcView: SequenceView + ?Sized + 'static {
+    fn reset(&mut self, view: Option<Arc<SrcView>>) {
+        let old_area = self.area();
+        self.src_view = view;
+        let new_area = self.area();
+
+        if let Some(area) = old_area { self.cast.notify_each(area); }
+        if let Some(area) = new_area { self.cast.notify_each(area); }
+    }
+
+    fn notify(&self, msg: &usize) {
+        self.cast.notify(msg);
+    }
+}
+