From e2c8ea8441b0cf1bbeddb73f1c9fff577ec4d2ea Mon Sep 17 00:00:00 2001
From: Michael Sippel <micha@fragmental.art>
Date: Sun, 2 Jun 2024 17:24:32 +0200
Subject: [PATCH] list reverse projection

---
 src/projection/filter_sequence.rs |   5 +-
 src/projection/mod.rs             |   1 +
 src/projection/reverse_list.rs    | 153 ++++++++++++++++++++++++++++++
 3 files changed, 158 insertions(+), 1 deletion(-)
 create mode 100644 src/projection/reverse_list.rs

diff --git a/src/projection/filter_sequence.rs b/src/projection/filter_sequence.rs
index a6e2b45..6819e3d 100644
--- a/src/projection/filter_sequence.rs
+++ b/src/projection/filter_sequence.rs
@@ -135,7 +135,10 @@ where
 
         opds.resize_with(1 + *idx, || false);
         let op = opds.get(*idx).cloned().unwrap_or(false);
-        *opds.get_mut(*idx).unwrap() = np;
+        // if let Some(o) = opds.get_mut(*idx) {
+            // *o = np;
+        // }
+       *opds.get_mut(*idx).unwrap() = np;
 
         drop(opds);
 
diff --git a/src/projection/mod.rs b/src/projection/mod.rs
index b3ae110..d6d3875 100644
--- a/src/projection/mod.rs
+++ b/src/projection/mod.rs
@@ -23,4 +23,5 @@ pub mod map_index_key;
 pub mod grid_offset;
 pub mod decorate_sequence;
 pub mod reverse_sequence;
+pub mod reverse_list;
 
diff --git a/src/projection/reverse_list.rs b/src/projection/reverse_list.rs
new file mode 100644
index 0000000..c020233
--- /dev/null
+++ b/src/projection/reverse_list.rs
@@ -0,0 +1,153 @@
+use {
+    crate::{
+        view::{
+            Observer, ObserverBroadcast, ObserverExt, OuterViewPort, View, ViewPort,
+            list::{ListDiff, ListView, ListViewExt},
+        },
+    },
+    std::sync::Arc,
+    std::sync::RwLock,
+};
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+impl<Item: Clone + Send + Sync + 'static> OuterViewPort<dyn ListView<Item>> {
+    pub fn reverse(&self) -> OuterViewPort<dyn ListView<Item>> {
+        let port = ViewPort::new();
+        port.add_update_hook(Arc::new(self.0.clone()));
+
+        let map = Arc::new(RwLock::new(ReverseList {
+            src_view: None,
+            end: 0,
+            cast: port.inner().get_broadcast(),
+        }));
+
+        self.add_observer(map.clone());
+        port.inner().set_view(Some(map));
+        port.into_outer()
+    }
+}
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+pub struct ReverseList<SrcView, Item>
+where Item: Clone + Send + Sync + 'static,
+    SrcView: ListView<Item> + ?Sized
+{
+    src_view: Option<Arc<SrcView>>,
+    end: usize,
+    cast: Arc<RwLock<ObserverBroadcast<dyn ListView<Item>>>>
+}
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+impl<SrcView, Item> View for ReverseList<SrcView, Item>
+where Item: Clone + Send + Sync + 'static,
+    SrcView: ListView<Item> + ?Sized
+{
+    type Msg = ListDiff<Item>;
+}
+
+impl<SrcView, Item> ListView<Item> for ReverseList<SrcView, Item>
+where Item: Clone + Send + Sync + 'static,
+    SrcView: ListView<Item> + ?Sized
+{
+    fn len(&self) -> Option<usize> {
+        Some(self.end)
+    }
+
+    fn get(&self, idx: &usize) -> Option<Item> {
+        if *idx < self.end {
+            self.src_view.get( &(self.end - idx - 1) )
+        } else {
+            None
+        }
+    }
+}
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+impl<Item, SrcView> Observer<SrcView> for ReverseList<SrcView, Item>
+where Item: Clone + Send + Sync + 'static,
+    SrcView: ListView<Item> + ?Sized
+{
+    fn reset(&mut self, view: Option<Arc<SrcView>>) {
+        self.src_view = view;
+
+        self.cast.notify(&ListDiff::Clear);
+        if let Some(v) = self.src_view.as_ref() {
+            self.end = v.len().unwrap();
+            for idx in 0 .. self.end {
+                if idx < self.end {
+                    let val = v.get( &(self.end - idx - 1) ).unwrap();
+                    self.cast.notify(&ListDiff::Insert{ idx: idx, val });
+                }
+            }
+        }
+    }
+
+    fn notify(&mut self, msg: &ListDiff<Item>) {
+        /* todo optimize
+         */
+        //let len = self.src_view.len().unwrap();
+
+        self.cast.notify(&match msg {
+            ListDiff::Clear => {
+                self.end = 0;
+                ListDiff::Clear
+            },
+            ListDiff::Remove(mut idx) => {
+                self.end -= 1;
+                idx = self.end - idx;
+                ListDiff::Remove(idx)
+            }
+            ListDiff::Insert{ mut idx, val } => {
+                idx = self.end - idx;
+                self.end += 1;
+                ListDiff::Insert{ idx, val:val.clone() }
+            }
+            ListDiff::Update{ mut idx, val } => {
+                idx = self.end - idx - 1;
+                ListDiff::Update{ idx, val:val.clone() }
+            }
+        });
+    }
+}
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+#[cfg(test)]
+mod tests {
+    use crate::buffer::vec::*;
+    use crate::view::{port::UpdateTask, list::ListView};
+
+    #[test]
+    fn rev_list1() {
+        let mut buffer = VecBuffer::new();
+
+        let target_port = buffer.get_port().to_list().reverse();
+        let target_view = target_port.get_view();
+
+        buffer.push(0);
+        buffer.push(7);
+        buffer.push(9);
+
+        target_port.0.update();
+
+        assert_eq!(target_view.len(), Some(3));
+
+        assert_eq!(target_view.get(&0), Some(9));
+        assert_eq!(target_view.get(&1), Some(7));
+        assert_eq!(target_view.get(&2), Some(0));
+        assert_eq!(target_view.get(&3), None);
+
+        buffer.remove(0);
+
+        target_port.0.update();
+        assert_eq!(target_view.len(), Some(2));
+        assert_eq!(target_view.get(&0), Some(9));
+        assert_eq!(target_view.get(&1), Some(7));
+        assert_eq!(target_view.get(&2), None);
+     }
+}
+