More work towards implementing PCRE matching

regex/matching.go

@@ -314,13 +314,36 @@ func findAllSubmatchHelper(start *nfaState, str []rune, offset int, numGroups in
 			currentState.threadGroups = newMatch(numGroups + 1)
 			currentState.threadGroups[0].StartIdx = idx
 		}
+
 		if currentState.groupBegin {
 			currentState.threadGroups[currentState.groupNum].StartIdx = idx
-		} else if currentState.groupEnd {
+		}
+
+		if currentState.groupEnd {
 			currentState.threadGroups[currentState.groupNum].EndIdx = idx
-		} else if currentState.isKleene {
-			// Append the
-		} else if currentState.isAlternation {
+		}
+
+		//		if currentState.isKleene {
+		//			// Append the next-state (after the kleene), then append the kleene state
+		//			allMatches := make([]*nfaState, 0)
+		//			for _, v := range currentState.transitions {
+		//				allMatches = append(allMatches, v...)
+		//			}
+		//			slices.Reverse(allMatches)
+		//			for _, m := range allMatches {
+		//				m.threadGroups = currentState.threadGroups
+		//				m.threadSP = idx
+		//			}
+		//			currentStates = append(currentStates, allMatches...)
+		//
+		//			//	kleeneState := currentState.kleeneState
+		//			//	kleeneState.threadGroups = currentState.threadGroups
+		//			//	kleeneState.threadSP = currentState.threadSP
+		//			//	currentStates = append(currentStates, kleeneState)
+		//			continue
+		//		}
+
+		if currentState.isAlternation {
 			rightState := currentState.rightState
 			rightState.threadGroups = currentState.threadGroups
 			rightState.threadSP = currentState.threadSP
@@ -330,7 +353,22 @@ func findAllSubmatchHelper(start *nfaState, str []rune, offset int, numGroups in
 			leftState.threadSP = currentState.threadSP
 			currentStates = append(currentStates, currentState.leftState)
 			continue
-		} else if currentState.contentContains(str, idx) {
+		}
+
+		if currentState.isEmpty && currentState.assert == noneAssert {
+			allMatches := make([]*nfaState, 0)
+			for _, v := range currentState.transitions {
+				allMatches = append(allMatches, v...)
+			}
+			slices.Reverse(allMatches)
+			for _, m := range allMatches {
+				m.threadGroups = currentState.threadGroups
+				m.threadSP = idx
+			}
+			currentStates = append(currentStates, allMatches...)
+		}
+
+		if currentState.contentContains(str, idx) {
 			foundMatch = true
 			allMatches := make([]*nfaState, 0)
 			for _, v := range currentState.transitions {
@@ -348,9 +386,17 @@ func findAllSubmatchHelper(start *nfaState, str []rune, offset int, numGroups in
 			currentStates = append(currentStates, allMatches...)
 		}
 
-		if currentState.isLast && foundMatch { // Last state reached
+		if currentState.isLast { // Last state reached
+			if foundMatch {
 				currentState.threadGroups[0].EndIdx = idx + 1
 				return true, currentState.threadGroups, idx + 1
+			} else if currentState.isEmpty && currentState.assert == noneAssert {
+				currentState.threadGroups[0].EndIdx = idx
+				if idx == currentState.threadGroups[0].StartIdx {
+					idx++
+				}
+				return true, currentState.threadGroups, idx
+			}
 
 		}
 	}