Add helper methods for the regex and fuzzy automatons (#22)

- Add MatchAndDistance API to DFA automaton for fuzzy matching using
Levenshtein distance.
- Add MatchesRegex API to regex automaton for validating input against
the pattern.

automaton.go

@@ -87,4 +87,5 @@ var alwaysMatchAutomaton = &AlwaysMatch{}
 type FuzzyAutomaton interface {
 	Automaton
 	EditDistance(int) uint8
+	MatchAndDistance(input string) (bool, uint8)
 }

levenshtein/dfa.go

@@ -43,6 +43,24 @@ func (d *DFA) EditDistance(stateId int) uint8 {
 	return d.distances[stateId].distance()
 }
 
+func (d *DFA) MatchAndDistance(input string) (bool, uint8) {
+	currentState := d.Start()
+	index := 0
+	// Traverse the DFA while characters can still match
+	for d.CanMatch(currentState) && index < len(input) {
+		currentState = d.Accept(currentState, input[index])
+		if currentState == int(SinkState) {
+			break
+		}
+		index++
+	}
+	// Ensure we've processed the entire input and check if the current state is a match
+	if index == len(input) && d.IsMatch(currentState) {
+		return true, d.EditDistance(currentState)
+	}
+	return false, 0
+}
+
 // Returns the number of states in the `DFA`.
 func (d *DFA) numStates() int {
 	return len(d.transitions)

regexp/regexp.go

@@ -117,3 +117,14 @@ func (r *Regexp) Accept(s int, b byte) int {
 	}
 	return 0
 }
+
+func (r *Regexp) MatchesRegex(input string) bool {
+	currentState := r.Start()
+	index := 0
+	// Traverse the DFA while characters can still match
+	for r.CanMatch(currentState) && index < len(input) {
+		currentState = r.Accept(currentState, input[index])
+		index++
+	}
+	return index == len(input) && r.IsMatch(currentState)
+}