Added text diff utilities

src/algorithms/capture.rs

@@ -0,0 +1,112 @@
+use crate::algorithms::hook::DiffHook;
+use std::convert::Infallible;
+
+/// Utility enum to capture a diff operation.
+///
+/// This is used by [`Capture`](crate::algorithms::Capture).
+#[derive(Debug, PartialEq, Eq, Hash, Clone, Copy)]
+pub enum DiffOp {
+    /// A segment is equal (see [`DiffHook::equal`])
+    Equal {
+        old_index: usize,
+        new_index: usize,
+        len: usize,
+    },
+    /// A segment was deleted (see [`DiffHook::delete`])
+    Delete {
+        old_index: usize,
+        old_len: usize,
+        new_index: usize,
+    },
+    /// A segment was inserted (see [`DiffHook::insert`])
+    Insert {
+        old_index: usize,
+        new_index: usize,
+        new_len: usize,
+    },
+    /// A segment was replaced (see [`DiffHook::replace`])
+    Replace {
+        old_index: usize,
+        old_len: usize,
+        new_index: usize,
+        new_len: usize,
+    },
+}
+
+/// A [`DiffHook`] that captures all diff operations.
+#[derive(Default, Clone)]
+pub struct Capture(Vec<DiffOp>);
+
+impl Capture {
+    /// Creates a new capture hook.
+    pub fn new() -> Capture {
+        Capture::default()
+    }
+
+    /// Converts the capture hook into a vector.
+    pub fn into_vec(self) -> Vec<DiffOp> {
+        self.0
+    }
+
+    /// Accesses the captured operations.
+    pub fn ops(&self) -> &[DiffOp] {
+        &self.0
+    }
+}
+
+impl DiffHook for Capture {
+    type Error = Infallible;
+
+    fn equal(&mut self, old_index: usize, new_index: usize, len: usize) -> Result<(), Self::Error> {
+        self.0.push(DiffOp::Equal {
+            old_index,
+            new_index,
+            len,
+        });
+        Ok(())
+    }
+
+    fn delete(
+        &mut self,
+        old_index: usize,
+        old_len: usize,
+        new_index: usize,
+    ) -> Result<(), Self::Error> {
+        self.0.push(DiffOp::Delete {
+            old_index,
+            old_len,
+            new_index,
+        });
+        Ok(())
+    }
+
+    fn insert(
+        &mut self,
+        old_index: usize,
+        new_index: usize,
+        new_len: usize,
+    ) -> Result<(), Self::Error> {
+        self.0.push(DiffOp::Insert {
+            old_index,
+            new_index,
+            new_len,
+        });
+        Ok(())
+    }
+
+    fn replace(
+        &mut self,
+        old_index: usize,
+        old_len: usize,
+        new_index: usize,
+        new_len: usize,
+    ) -> Result<(), Self::Error> {
+        self.0.push(DiffOp::Replace {
+            old_index,
+            old_len,
+            new_index,
+            new_len,
+        });
+        Ok(())
+    }
+}