refactoring

gpx-rs/engine/src/core/gpx/chunk.rs

@@ -2,6 +2,29 @@ use uuid::Uuid;
 
 use crate::{Trackpoint, Waypoint};
 
+/// A run of items, shared between the successive versions of a [`crate::Chunked`] list: a chunk
+/// that is not touched by an edit is not copied.
+///
+/// Chunks are equal when they have the same identity, which is cheap to compare and changes
+/// whenever the content does (a modified chunk is a new one).
+pub trait Chunk {
+    type Item: Clone;
+
+    /// Maximum number of items of a chunk.
+    const MAX_SIZE: usize;
+
+    /// A chunk with a new identity, holding `items`.
+    fn new(items: Vec<Self::Item>) -> Self;
+
+    fn items(&self) -> &Vec<Self::Item>;
+
+    fn items_mut(&mut self) -> &mut Vec<Self::Item>;
+
+    fn is_full(&self) -> bool {
+        self.items().len() >= Self::MAX_SIZE
+    }
+}
+
 const MAX_TRKPT_CHUNK_SIZE: usize = 4096;
 
 #[derive(Debug, PartialEq, Eq)]
@@ -25,9 +48,23 @@ impl PartialEq for TrackpointChunk {
     }
 }
 
-impl TrackpointChunk {
-    pub fn is_full(&self) -> bool {
-        self.trkpt.len() == MAX_TRKPT_CHUNK_SIZE
+impl Chunk for TrackpointChunk {
+    type Item = Trackpoint;
+    const MAX_SIZE: usize = MAX_TRKPT_CHUNK_SIZE;
+
+    fn new(trkpt: Vec<Trackpoint>) -> Self {
+        Self {
+            trkpt,
+            ..Default::default()
+        }
+    }
+
+    fn items(&self) -> &Vec<Trackpoint> {
+        &self.trkpt
+    }
+
+    fn items_mut(&mut self) -> &mut Vec<Trackpoint> {
+        &mut self.trkpt
     }
 }
 
@@ -54,9 +91,23 @@ impl PartialEq for WaypointChunk {
     }
 }
 
-impl WaypointChunk {
-    pub fn is_full(&self) -> bool {
-        self.wpt.len() == MAX_WPT_CHUNK_SIZE
+impl Chunk for WaypointChunk {
+    type Item = Waypoint;
+    const MAX_SIZE: usize = MAX_WPT_CHUNK_SIZE;
+
+    fn new(wpt: Vec<Waypoint>) -> Self {
+        Self {
+            wpt,
+            ..Default::default()
+        }
+    }
+
+    fn items(&self) -> &Vec<Waypoint> {
+        &self.wpt
+    }
+
+    fn items_mut(&mut self) -> &mut Vec<Waypoint> {
+        &mut self.wpt
     }
 }
 
@@ -86,6 +137,15 @@ mod tests {
         assert!(chunk.is_full());
     }
 
+    #[test]
+    fn test_new_chunks_have_their_own_identity() {
+        let a = TrackpointChunk::new(vec![Trackpoint::default()]);
+        let b = TrackpointChunk::new(vec![Trackpoint::default()]);
+        assert_ne!(a, b);
+        assert_eq!(a.items().len(), 1);
+        assert_ne!(WaypointChunk::new(vec![]), WaypointChunk::new(vec![]));
+    }
+
     #[test]
     fn test_chunk_equality_is_by_id() {
         let a = TrackpointChunk::default();