From 5ce263b586c5047d16ee93cc53bc3bce6f7ff12c Mon Sep 17 00:00:00 2001
From: Jonas Maier <jonas@x77.dev>
Date: Tue, 2 Jun 2026 23:52:23 +0200
Subject: fix lookahead

---
 src/parse/regex/enfa.rs                        | 28 +++++++++++++++++---------
 test-cases/case2_positive_lookahead/script.sh  | 14 +++++++++++++
 test-cases/case2_positive_lookahead/stdout.txt |  2 ++
 3 files changed, 35 insertions(+), 9 deletions(-)

diff --git a/src/parse/regex/enfa.rs b/src/parse/regex/enfa.rs
index a407e9e..272c709 100644
--- a/src/parse/regex/enfa.rs
+++ b/src/parse/regex/enfa.rs
@@ -116,7 +116,7 @@ mod product_tests {
     }
 }
 
-#[derive(Clone, Hash, PartialEq, Eq, PartialOrd, Ord)]
+#[derive(Clone, Debug, Hash, PartialEq, Eq, PartialOrd, Ord)]
 struct Thread {
     state: StateId,
     positives: Vec<Thread>,
@@ -200,19 +200,28 @@ impl Thread {
 
         let Self {
             state,
-            mut positives,
-            mut negatives,
+            positives,
+            negatives,
         } = self;
+        let mut p = Vec::new();
+        let mut n = Vec::new();
         for assertion in new_assertions {
-            let mut threads = Self::new_simple(assertion.to).step_epsilon(enfa);
+            let threads = Self::new_simple(assertion.to).step_epsilon(enfa);
             let vec = match assertion.polarity {
-                LookPolarity::Positive => &mut positives,
-                LookPolarity::Negative => &mut negatives,
+                LookPolarity::Positive => &mut p,
+                LookPolarity::Negative => &mut n,
             };
-            vec.append(&mut threads);
+            vec.push(threads);
         }
-        if let Some(thread) = Self::new(enfa, state, positives, negatives) {
-            ret(thread);
+        let p = cartesian_product(p);
+        for mut p in p {
+            let mut positives = positives.clone();
+            let mut negatives = negatives.clone();
+            positives.append(&mut p);
+            negatives.append(&mut n.iter().cloned().flatten().collect());
+            if let Some(thread) = Self::new(enfa, state, positives, negatives) {
+                ret(thread);
+            }
         }
     }
 
@@ -230,6 +239,7 @@ impl Thread {
     fn step0(self, enfa: &ENFA, input: ByteRange, ret: &mut impl FnMut(Thread)) {
         let positives = self
             .positives
+            .clone()
             .into_iter()
             .map(|t| t.step(enfa, input))
             .collect();
diff --git a/test-cases/case2_positive_lookahead/script.sh b/test-cases/case2_positive_lookahead/script.sh
index f19441a..053461d 100644
--- a/test-cases/case2_positive_lookahead/script.sh
+++ b/test-cases/case2_positive_lookahead/script.sh
@@ -88,4 +88,18 @@ match x4 aaaaaaaaaaae no
 match x4 aaaaaaaaaaaae yes
 echo x4
 
+fun x5 {
+    case $1 {
+        (?=(a.)*e)(?=(a..)*e)(?=(a....)*e).*e { echo yes }
+        .* { echo no }
+    }
+}
+match x5 e yes
+match x5 aaaaaaaaaaaaaaaaaaaaaaaaaaaaae no
+match x5 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaae yes
+match x5 a.aaaaaaaaaaaaaaaaaaaaaaaaaaa.e yes
+match x5 .aaaaaaaaaaaaaaaaaaaaaaaaaaaaae no
+match x5 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaae no
+echo x5
+
 echo done
diff --git a/test-cases/case2_positive_lookahead/stdout.txt b/test-cases/case2_positive_lookahead/stdout.txt
index ffa387f..fa2c182 100644
--- a/test-cases/case2_positive_lookahead/stdout.txt
+++ b/test-cases/case2_positive_lookahead/stdout.txt
@@ -1,6 +1,8 @@
 begin
+x0
 x1
 x2
 x3
 x4
+x5
 done
-- 
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