feat(core): Expand filtering into pipeline supporting multiple text search modes.

Modes include: exact match, smart-case, and regular expressions.

crates/pikl-core/src/query/strategy.rs

@@ -0,0 +1,231 @@
+//! Filter segment prefix parsing. Determines which filter
+//! strategy to use based on the query prefix.
+
+/// The type of filter to apply for a query segment.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum FilterKind {
+    Fuzzy,
+    Exact,
+    Regex,
+}
+
+/// A parsed filter segment with its kind, inversion flag,
+/// and the actual query text (prefix stripped).
+#[derive(Debug, PartialEq, Eq)]
+pub struct ParsedSegment<'a> {
+    pub kind: FilterKind,
+    pub inverse: bool,
+    pub query: &'a str,
+}
+
+/// Parse a single filter segment's prefix to determine
+/// the filter strategy and extract the query text.
+///
+/// Prefix rules (order matters):
+/// 1. `!/pattern/` -> Regex, inverse, inner pattern
+/// 2. `/pattern/`  -> Regex, inner pattern
+/// 3. `!'query`    -> Exact, inverse, after `!'`
+/// 4. `!query`     -> Fuzzy, inverse, after `!`
+/// 5. `'query`     -> Exact, after `'`
+/// 6. Everything else -> Fuzzy
+///
+/// A `/` with no closing slash is treated as fuzzy (user
+/// is still typing the regex delimiter).
+pub fn parse_segment(segment: &str) -> ParsedSegment<'_> {
+    // Check for inverse regex: !/pattern/
+    if let Some(rest) = segment.strip_prefix("!/") {
+        if let Some(inner) = rest.strip_suffix('/') {
+            return ParsedSegment {
+                kind: FilterKind::Regex,
+                inverse: true,
+                query: inner,
+            };
+        }
+        // No closing slash: treat the whole thing as fuzzy inverse
+        return ParsedSegment {
+            kind: FilterKind::Fuzzy,
+            inverse: true,
+            query: &segment[1..],
+        };
+    }
+
+    // Check for regex: /pattern/
+    if let Some(rest) = segment.strip_prefix('/') {
+        if let Some(inner) = rest.strip_suffix('/') {
+            return ParsedSegment {
+                kind: FilterKind::Regex,
+                inverse: false,
+                query: inner,
+            };
+        }
+        // No closing slash: treat as fuzzy (still typing)
+        return ParsedSegment {
+            kind: FilterKind::Fuzzy,
+            inverse: false,
+            query: segment,
+        };
+    }
+
+    // Check for inverse exact: !'query
+    if let Some(rest) = segment.strip_prefix("!'") {
+        return ParsedSegment {
+            kind: FilterKind::Exact,
+            inverse: true,
+            query: rest,
+        };
+    }
+
+    // Check for inverse fuzzy: !query
+    if let Some(rest) = segment.strip_prefix('!') {
+        return ParsedSegment {
+            kind: FilterKind::Fuzzy,
+            inverse: true,
+            query: rest,
+        };
+    }
+
+    // Check for exact: 'query
+    if let Some(rest) = segment.strip_prefix('\'') {
+        return ParsedSegment {
+            kind: FilterKind::Exact,
+            inverse: false,
+            query: rest,
+        };
+    }
+
+    // Default: fuzzy
+    ParsedSegment {
+        kind: FilterKind::Fuzzy,
+        inverse: false,
+        query: segment,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn plain_text_is_fuzzy() {
+        let p = parse_segment("hello");
+        assert_eq!(p.kind, FilterKind::Fuzzy);
+        assert!(!p.inverse);
+        assert_eq!(p.query, "hello");
+    }
+
+    #[test]
+    fn empty_is_fuzzy() {
+        let p = parse_segment("");
+        assert_eq!(p.kind, FilterKind::Fuzzy);
+        assert!(!p.inverse);
+        assert_eq!(p.query, "");
+    }
+
+    #[test]
+    fn exact_prefix() {
+        let p = parse_segment("'exact match");
+        assert_eq!(p.kind, FilterKind::Exact);
+        assert!(!p.inverse);
+        assert_eq!(p.query, "exact match");
+    }
+
+    #[test]
+    fn regex_delimiters() {
+        let p = parse_segment("/[0-9]+/");
+        assert_eq!(p.kind, FilterKind::Regex);
+        assert!(!p.inverse);
+        assert_eq!(p.query, "[0-9]+");
+    }
+
+    #[test]
+    fn inverse_fuzzy() {
+        let p = parse_segment("!temp");
+        assert_eq!(p.kind, FilterKind::Fuzzy);
+        assert!(p.inverse);
+        assert_eq!(p.query, "temp");
+    }
+
+    #[test]
+    fn inverse_exact() {
+        let p = parse_segment("!'temp");
+        assert_eq!(p.kind, FilterKind::Exact);
+        assert!(p.inverse);
+        assert_eq!(p.query, "temp");
+    }
+
+    #[test]
+    fn inverse_regex() {
+        let p = parse_segment("!/[0-9]+/");
+        assert_eq!(p.kind, FilterKind::Regex);
+        assert!(p.inverse);
+        assert_eq!(p.query, "[0-9]+");
+    }
+
+    #[test]
+    fn unclosed_regex_is_fuzzy() {
+        let p = parse_segment("/still typing");
+        assert_eq!(p.kind, FilterKind::Fuzzy);
+        assert!(!p.inverse);
+        assert_eq!(p.query, "/still typing");
+    }
+
+    #[test]
+    fn unclosed_inverse_regex_is_fuzzy_inverse() {
+        let p = parse_segment("!/still typing");
+        assert_eq!(p.kind, FilterKind::Fuzzy);
+        assert!(p.inverse);
+        assert_eq!(p.query, "/still typing");
+    }
+
+    #[test]
+    fn just_slash_is_fuzzy() {
+        let p = parse_segment("/");
+        assert_eq!(p.kind, FilterKind::Fuzzy);
+        assert!(!p.inverse);
+        assert_eq!(p.query, "/");
+    }
+
+    #[test]
+    fn empty_regex_pattern() {
+        let p = parse_segment("//");
+        assert_eq!(p.kind, FilterKind::Regex);
+        assert!(!p.inverse);
+        assert_eq!(p.query, "");
+    }
+
+    #[test]
+    fn just_exclamation() {
+        let p = parse_segment("!");
+        assert_eq!(p.kind, FilterKind::Fuzzy);
+        assert!(p.inverse);
+        assert_eq!(p.query, "");
+    }
+
+    #[test]
+    fn just_quote() {
+        let p = parse_segment("'");
+        assert_eq!(p.kind, FilterKind::Exact);
+        assert!(!p.inverse);
+        assert_eq!(p.query, "");
+    }
+
+    // -- Double-prefix edge cases --
+
+    #[test]
+    fn double_exclamation() {
+        // "!!query" -> first ! is inverse, rest is "!query" which is fuzzy inverse
+        let p = parse_segment("!!query");
+        assert_eq!(p.kind, FilterKind::Fuzzy);
+        assert!(p.inverse);
+        assert_eq!(p.query, "!query");
+    }
+
+    #[test]
+    fn inverse_exact_regex_like() {
+        // "!'[0-9]" -> exact inverse, query is "[0-9]" (not regex)
+        let p = parse_segment("!'[0-9]");
+        assert_eq!(p.kind, FilterKind::Exact);
+        assert!(p.inverse);
+        assert_eq!(p.query, "[0-9]");
+    }
+}