From 858e535fba88846dc8ecda50010834c27762ce92 Mon Sep 17 00:00:00 2001
From: Aadhavan Srinivasan <aadhavan@twomorecents.org>
Date: Wed, 5 Feb 2025 18:01:36 -0500
Subject: [PATCH] Continued implementing Thompson's algorithm

---
 regex/matching.go | 43 ++++++++++++++++++++++++++++++++++++-------
 1 file changed, 36 insertions(+), 7 deletions(-)

diff --git a/regex/matching.go b/regex/matching.go
index 760f7c1..3252742 100644
--- a/regex/matching.go
+++ b/regex/matching.go
@@ -153,7 +153,7 @@ func pruneIndices(indices []Match) []Match {
 
 func copyThread(to *nfaState, from nfaState) {
 	to.threadSP = from.threadSP
-	to.threadGroups = from.threadGroups
+	to.threadGroups = append([]Group{}, from.threadGroups...)
 }
 
 // Find returns the 0-group of the leftmost match of the regex in the given string.
@@ -325,10 +325,33 @@ func findAllSubmatchHelper(start *nfaState, str []rune, offset int, numGroups in
 
 			if currentState.groupBegin {
 				currentState.threadGroups[currentState.groupNum].StartIdx = idx
+				//		allMatches := make([]nfaState, 0)
+				//		for _, v := range currentState.transitions {
+				//			dereferenced := funcMap(v, func(s *nfaState) nfaState {
+				//				return *s
+				//			})
+				//			allMatches = append(allMatches, dereferenced...)
+				//		}
+				//		slices.Reverse(allMatches)
+				//		for i := range allMatches {
+				//			copyThread(&allMatches[i], currentState)
+				//		}
+				//		currentStates = append(currentStates, allMatches...)
 			}
-
 			if currentState.groupEnd {
 				currentState.threadGroups[currentState.groupNum].EndIdx = idx
+				//			allMatches := make([]nfaState, 0)
+				//			for _, v := range currentState.transitions {
+				//				dereferenced := funcMap(v, func(s *nfaState) nfaState {
+				//					return *s
+				//				})
+				//				allMatches = append(allMatches, dereferenced...)
+				//			}
+				//			slices.Reverse(allMatches)
+				//			for i := range allMatches {
+				//				copyThread(&allMatches[i], currentState)
+				//			}
+				//			currentStates = append(currentStates, allMatches...)
 			}
 
 			//		if currentState.isKleene {
@@ -363,7 +386,7 @@ func findAllSubmatchHelper(start *nfaState, str []rune, offset int, numGroups in
 			}
 
 			// Empty state - enqueue next state, do _not_ increment the SP
-			if currentState.isEmpty && currentState.assert == noneAssert {
+			if currentState.isEmpty && currentState.assert == noneAssert { //&& currentState.groupBegin == false && currentState.groupEnd == false {
 				isEmptyAndNoAssertion = true
 			}
 
@@ -386,10 +409,16 @@ func findAllSubmatchHelper(start *nfaState, str []rune, offset int, numGroups in
 						allMatches[i].threadSP += 1
 					}
 				}
-				nextStates = append(nextStates, allMatches...)
+				if currentState.groupBegin {
+					currentStates = slices.Insert(currentStates, currentStateIdx+1, allMatches...)
+				} else if currentState.groupEnd {
+					currentStates = append(currentStates, allMatches...)
+				} else {
+					nextStates = append(nextStates, allMatches...)
+				}
 			}
 
-			if currentState.isLast { // Last state reached
+			if currentState.isLast && len(nextStates) == 0 { // Last state reached
 				if foundMatch {
 					if currentState.assert != noneAssert {
 						currentState.threadGroups[0].EndIdx = idx
@@ -400,7 +429,7 @@ func findAllSubmatchHelper(start *nfaState, str []rune, offset int, numGroups in
 						idx += 1
 					}
 					return true, currentState.threadGroups, idx
-				} else if currentState.isEmpty && currentState.assert == noneAssert {
+				} else if isEmptyAndNoAssertion {
 					currentState.threadGroups[0].EndIdx = idx
 					if idx == currentState.threadGroups[0].StartIdx {
 						idx++
@@ -410,7 +439,7 @@ func findAllSubmatchHelper(start *nfaState, str []rune, offset int, numGroups in
 
 			}
 		}
-		copy(currentStates, nextStates)
+		currentStates = append([]nfaState{}, nextStates...)
 		nextStates = nil
 	}
 	return false, []Group{}, i + 1