Scrollable slash commands (#1830)

Scrollable slash commands. Part 1 of the multi PR.

codex-rs/common/src/fuzzy_match.rs

@@ -0,0 +1,177 @@
+/// Simple case-insensitive subsequence matcher used for fuzzy filtering.
+///
+/// Returns the indices (character positions) of the matched characters in the
+/// ORIGINAL `haystack` string and a score where smaller is better.
+///
+/// Unicode correctness: we perform the match on a lowercased copy of the
+/// haystack and needle but maintain a mapping from each character in the
+/// lowercased haystack back to the original character index in `haystack`.
+/// This ensures the returned indices can be safely used with
+/// `str::chars().enumerate()` consumers for highlighting, even when
+/// lowercasing expands certain characters (e.g., ß → ss, İ → i̇).
+pub fn fuzzy_match(haystack: &str, needle: &str) -> Option<(Vec<usize>, i32)> {
+    if needle.is_empty() {
+        return Some((Vec::new(), i32::MAX));
+    }
+
+    let mut lowered_chars: Vec<char> = Vec::new();
+    let mut lowered_to_orig_char_idx: Vec<usize> = Vec::new();
+    for (orig_idx, ch) in haystack.chars().enumerate() {
+        for lc in ch.to_lowercase() {
+            lowered_chars.push(lc);
+            lowered_to_orig_char_idx.push(orig_idx);
+        }
+    }
+
+    let lowered_needle: Vec<char> = needle.to_lowercase().chars().collect();
+
+    let mut result_orig_indices: Vec<usize> = Vec::with_capacity(lowered_needle.len());
+    let mut last_lower_pos: Option<usize> = None;
+    let mut cur = 0usize;
+    for &nc in lowered_needle.iter() {
+        let mut found_at: Option<usize> = None;
+        while cur < lowered_chars.len() {
+            if lowered_chars[cur] == nc {
+                found_at = Some(cur);
+                cur += 1;
+                break;
+            }
+            cur += 1;
+        }
+        let pos = found_at?;
+        result_orig_indices.push(lowered_to_orig_char_idx[pos]);
+        last_lower_pos = Some(pos);
+    }
+
+    let first_lower_pos = if result_orig_indices.is_empty() {
+        0usize
+    } else {
+        let target_orig = result_orig_indices[0];
+        lowered_to_orig_char_idx
+            .iter()
+            .position(|&oi| oi == target_orig)
+            .unwrap_or(0)
+    };
+    // last defaults to first for single-hit; score = extra span between first/last hit
+    // minus needle len (≥0).
+    // Strongly reward prefix matches by subtracting 100 when the first hit is at index 0.
+    let last_lower_pos = last_lower_pos.unwrap_or(first_lower_pos);
+    let window =
+        (last_lower_pos as i32 - first_lower_pos as i32 + 1) - (lowered_needle.len() as i32);
+    let mut score = window.max(0);
+    if first_lower_pos == 0 {
+        score -= 100;
+    }
+
+    result_orig_indices.sort_unstable();
+    result_orig_indices.dedup();
+    Some((result_orig_indices, score))
+}
+
+/// Convenience wrapper to get only the indices for a fuzzy match.
+pub fn fuzzy_indices(haystack: &str, needle: &str) -> Option<Vec<usize>> {
+    fuzzy_match(haystack, needle).map(|(mut idx, _)| {
+        idx.sort_unstable();
+        idx.dedup();
+        idx
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn ascii_basic_indices() {
+        let (idx, score) = match fuzzy_match("hello", "hl") {
+            Some(v) => v,
+            None => panic!("expected a match"),
+        };
+        assert_eq!(idx, vec![0, 2]);
+        // 'h' at 0, 'l' at 2 -> window 1; start-of-string bonus applies (-100)
+        assert_eq!(score, -99);
+    }
+
+    #[test]
+    fn unicode_dotted_i_istanbul_highlighting() {
+        let (idx, score) = match fuzzy_match("İstanbul", "is") {
+            Some(v) => v,
+            None => panic!("expected a match"),
+        };
+        assert_eq!(idx, vec![0, 1]);
+        // Matches at lowered positions 0 and 2 -> window 1; start-of-string bonus applies
+        assert_eq!(score, -99);
+    }
+
+    #[test]
+    fn unicode_german_sharp_s_casefold() {
+        assert!(fuzzy_match("straße", "strasse").is_none());
+    }
+
+    #[test]
+    fn prefer_contiguous_match_over_spread() {
+        let (_idx_a, score_a) = match fuzzy_match("abc", "abc") {
+            Some(v) => v,
+            None => panic!("expected a match"),
+        };
+        let (_idx_b, score_b) = match fuzzy_match("a-b-c", "abc") {
+            Some(v) => v,
+            None => panic!("expected a match"),
+        };
+        // Contiguous window -> 0; start-of-string bonus -> -100
+        assert_eq!(score_a, -100);
+        // Spread over 5 chars for 3-letter needle -> window 2; with bonus -> -98
+        assert_eq!(score_b, -98);
+        assert!(score_a < score_b);
+    }
+
+    #[test]
+    fn start_of_string_bonus_applies() {
+        let (_idx_a, score_a) = match fuzzy_match("file_name", "file") {
+            Some(v) => v,
+            None => panic!("expected a match"),
+        };
+        let (_idx_b, score_b) = match fuzzy_match("my_file_name", "file") {
+            Some(v) => v,
+            None => panic!("expected a match"),
+        };
+        // Start-of-string contiguous -> window 0; bonus -> -100
+        assert_eq!(score_a, -100);
+        // Non-prefix contiguous -> window 0; no bonus -> 0
+        assert_eq!(score_b, 0);
+        assert!(score_a < score_b);
+    }
+
+    #[test]
+    fn empty_needle_matches_with_max_score_and_no_indices() {
+        let (idx, score) = match fuzzy_match("anything", "") {
+            Some(v) => v,
+            None => panic!("empty needle should match"),
+        };
+        assert!(idx.is_empty());
+        assert_eq!(score, i32::MAX);
+    }
+
+    #[test]
+    fn case_insensitive_matching_basic() {
+        let (idx, score) = match fuzzy_match("FooBar", "foO") {
+            Some(v) => v,
+            None => panic!("expected a match"),
+        };
+        assert_eq!(idx, vec![0, 1, 2]);
+        // Contiguous prefix match (case-insensitive) -> window 0 with bonus
+        assert_eq!(score, -100);
+    }
+
+    #[test]
+    fn indices_are_deduped_for_multichar_lowercase_expansion() {
+        let needle = "\u{0069}\u{0307}"; // "i" + combining dot above
+        let (idx, score) = match fuzzy_match("İ", needle) {
+            Some(v) => v,
+            None => panic!("expected a match"),
+        };
+        assert_eq!(idx, vec![0]);
+        // Lowercasing 'İ' expands to two chars; contiguous prefix -> window 0 with bonus
+        assert_eq!(score, -100);
+    }
+}

codex-rs/common/src/lib.rs

@@ -27,3 +27,5 @@ pub use sandbox_summary::summarize_sandbox_policy;
 mod config_summary;
 
 pub use config_summary::create_config_summary_entries;
+// Shared fuzzy matcher (used by TUI selection popups and other UI filtering)
+pub mod fuzzy_match;