Better split functionality between toplevel and algorithms

src/algorithms/hook.rs

@@ -0,0 +1,109 @@
+/// A trait for reacting to an edit script from the "old" version to
+/// the "new" version.
+pub trait DiffHook: Sized {
+    /// The error produced from the hook methods.
+    type Error;
+
+    /// Called when lines with indices `old_index` (in the old version) and
+    /// `new_index` (in the new version) start an section equal in both
+    /// versions, of length `len`.
+    fn equal(&mut self, old_index: usize, new_index: usize, len: usize) -> Result<(), Self::Error> {
+        let _ = old_index;
+        let _ = new_index;
+        let _ = len;
+        Ok(())
+    }
+
+    /// Called when a section of length `old_len`, starting at `old_index`,
+    /// needs to be deleted from the old version.
+    fn delete(
+        &mut self,
+        old_index: usize,
+        old_len: usize,
+        new_index: usize,
+    ) -> Result<(), Self::Error> {
+        let _ = old_index;
+        let _ = old_len;
+        let _ = new_index;
+        Ok(())
+    }
+
+    /// Called when a section of the new version, of length `new_len`
+    /// and starting at `new_index`, needs to be inserted at position `old_index'.
+    fn insert(
+        &mut self,
+        old_index: usize,
+        new_index: usize,
+        new_len: usize,
+    ) -> Result<(), Self::Error> {
+        let _ = old_index;
+        let _ = new_index;
+        let _ = new_len;
+        Ok(())
+    }
+
+    /// Called when a section of the old version, starting at index
+    /// `old_index` and of length `old_len`, needs to be replaced with a
+    /// section of length `new_len`, starting at `new_index`, of the new
+    /// version.
+    ///
+    /// The default implementations invokes `delete` and `insert`.
+    ///
+    /// You can use the [`Replace`](crate::algorithms::Replace) hook to
+    /// automatically generate these.
+    fn replace(
+        &mut self,
+        old_index: usize,
+        old_len: usize,
+        new_index: usize,
+        new_len: usize,
+    ) -> Result<(), Self::Error> {
+        self.delete(old_index, old_len, new_index)?;
+        self.insert(old_index, new_index, new_len)
+    }
+
+    /// Always called at the end of the algorithm.
+    fn finish(&mut self) -> Result<(), Self::Error> {
+        Ok(())
+    }
+}
+
+impl<'a, D: DiffHook + 'a> DiffHook for &'a mut D {
+    type Error = D::Error;
+
+    fn equal(&mut self, old_index: usize, new_index: usize, len: usize) -> Result<(), Self::Error> {
+        (*self).equal(old_index, new_index, len)
+    }
+
+    fn delete(
+        &mut self,
+        old_index: usize,
+        old_len: usize,
+        new_index: usize,
+    ) -> Result<(), Self::Error> {
+        (*self).delete(old_index, old_len, new_index)
+    }
+
+    fn insert(
+        &mut self,
+        old_index: usize,
+        new_index: usize,
+        new_len: usize,
+    ) -> Result<(), Self::Error> {
+        (*self).insert(old_index, new_index, new_len)
+    }
+
+    fn replace(
+        &mut self,
+        old: usize,
+        old_len: usize,
+        new: usize,
+        new_len: usize,
+    ) -> Result<(), Self::Error> {
+        (*self).replace(old, old_len, new, new_len)
+    }
+
+    fn finish(&mut self) -> Result<(), Self::Error> {
+        (*self).finish()
+    }
+}