Add regex extractor

crates/pile-value/src/extract/regex.rs

@@ -0,0 +1,104 @@
+use std::sync::Arc;
+
+use pile_config::Label;
+use regex::Regex;
+use smartstring::{LazyCompact, SmartString};
+
+use crate::{
+	extract::traits::{ExtractState, ListExtractor, ObjectExtractor},
+	value::PileValue,
+};
+
+struct RegexData {
+	regex: Arc<Regex>,
+	/// Captured substrings indexed by group index (0 = whole match).
+	captures: Vec<Option<Arc<SmartString<LazyCompact>>>>,
+}
+
+impl RegexData {
+	fn new(regex: Arc<Regex>, input: &str) -> Option<Self> {
+		let caps = regex.captures(input)?;
+		let captures = caps
+			.iter()
+			.map(|m| m.map(|m| Arc::new(m.as_str().into())))
+			.collect();
+		Some(Self { regex, captures })
+	}
+}
+
+/// Exposes named capture groups as object fields.
+pub struct RegexExtractor(Arc<RegexData>);
+
+impl RegexExtractor {
+	/// Run `regex` against `input`. Returns `None` if there is no match.
+	pub fn new(regex: Arc<Regex>, input: &str) -> Option<Self> {
+		Some(Self(Arc::new(RegexData::new(regex, input)?)))
+	}
+}
+
+#[async_trait::async_trait]
+impl ObjectExtractor for RegexExtractor {
+	async fn field(
+		&self,
+		_state: &ExtractState,
+		name: &Label,
+		args: Option<&str>,
+	) -> Result<Option<PileValue>, std::io::Error> {
+		if args.is_some() {
+			return Ok(None);
+		}
+
+		let Some(idx) = self
+			.0
+			.regex
+			.capture_names()
+			.position(|n| n == Some(name.as_str()))
+		else {
+			return Ok(None);
+		};
+
+		Ok(Some(
+			match self.0.captures.get(idx).and_then(|v| v.as_ref()) {
+				Some(s) => PileValue::String(s.clone()),
+				None => PileValue::Null,
+			},
+		))
+	}
+
+	async fn fields(&self) -> Result<Vec<Label>, std::io::Error> {
+		#[expect(clippy::unwrap_used)]
+		Ok(self
+			.0
+			.regex
+			.capture_names()
+			.flatten()
+			.map(|n| Label::new(n).unwrap())
+			.collect())
+	}
+
+	fn as_list(&self) -> Option<Arc<dyn ListExtractor>> {
+		Some(Arc::new(RegexExtractor(self.0.clone())))
+	}
+}
+
+#[async_trait::async_trait]
+impl ListExtractor for RegexExtractor {
+	async fn get(
+		&self,
+		_state: &ExtractState,
+		idx: usize,
+	) -> Result<Option<PileValue>, std::io::Error> {
+		let raw_idx = idx + 1;
+		let Some(slot) = self.0.captures.get(raw_idx) else {
+			return Ok(None);
+		};
+		Ok(Some(match slot {
+			Some(s) => PileValue::String(s.clone()),
+			None => PileValue::Null,
+		}))
+	}
+
+	async fn len(&self, _state: &ExtractState) -> Result<usize, std::io::Error> {
+		Ok(self.0.captures.len().saturating_sub(1))
+	}
+}