Merge crates

src/utils/find_longest_prefix_contained_within.rs

@@ -0,0 +1,103 @@
+use crate::Token;
+
+/// Given two lists of tokens, returns `length` where `old` list somewhere
+/// within contains the `length` prefix of the `new` list.
+///
+/// ## Example
+///
+/// ```not_rust
+/// old: [0, 1, 9, 0, 2, 5]
+/// new:       [9, 0, 2, 5, 1]
+/// ```
+/// > results in an length of 4
+///
+///
+/// ```not_rust
+/// old: [0, 1, 9, 0, 2, 5]
+/// new:          [0, 2]
+/// ```
+/// > results in an length of 2
+///
+/// ```not_rust
+/// old: [0, 1, 9, 0, 2, 5]
+/// new:          [0, 4]
+/// ```
+/// > results in an length of 1
+pub fn find_longest_prefix_contained_within<T>(old: &[Token<T>], new: &[Token<T>]) -> usize
+where
+    T: PartialEq + Clone + std::fmt::Debug,
+{
+    let max_possible = new.len().min(old.len());
+
+    for len in (1..=max_possible).rev() {
+        let prefix = &new[..len];
+        if old.windows(len).any(|window| window == prefix) {
+            return len;
+        }
+    }
+
+    0
+}
+
+#[cfg(test)]
+mod tests {
+    use pretty_assertions::assert_eq;
+
+    use super::*;
+
+    #[test]
+    fn test_common_overlap() {
+        assert_eq!(
+            find_longest_prefix_contained_within(&["".into()], &["".into()]),
+            1
+        );
+
+        assert_eq!(
+            find_longest_prefix_contained_within(
+                &["a".into(), "b".into(), "c".into()],
+                &["b".into(), "c".into(), "a".into()]
+            ),
+            2
+        );
+
+        assert_eq!(
+            find_longest_prefix_contained_within(
+                &["a".into(), "b".into(), "c".into()],
+                &["b".into(), "c".into()]
+            ),
+            2
+        );
+
+        assert_eq!(
+            find_longest_prefix_contained_within(
+                &["a".into(), "b".into(), "c".into()],
+                &["b".into()]
+            ),
+            1
+        );
+
+        assert_eq!(
+            find_longest_prefix_contained_within(
+                &["a".into(), "b".into(), "c".into(), "b".into(), "a".into()],
+                &["b".into(), "a".into()]
+            ),
+            2
+        );
+
+        assert_eq!(
+            find_longest_prefix_contained_within(
+                &["a".into(), "a".into(), "a".into()],
+                &["a".into(), "b".into(), "c".into()]
+            ),
+            1
+        );
+
+        assert_eq!(
+            find_longest_prefix_contained_within(
+                &["a".into(), "b".into(), "c".into()],
+                &["d".into(), "e".into(), "a".into()]
+            ),
+            0
+        );
+    }
+}