From 340e52019fae28f9b5ac30535dc12ca08c9f88a4 Mon Sep 17 00:00:00 2001
From: Humza Shahid <humzasaur@gmail.com>
Date: Sat, 7 Feb 2026 02:25:45 +0000
Subject: [PATCH] handle edge case when deleting from buffer: if the previous
 match is extended into a new match, then replace the old match in the search
 list with the extended match

---
 fcore/search-list/search-list.sml | 54 ++++++++++++-------------------
 todo.md                           |  3 --
 2 files changed, 21 insertions(+), 36 deletions(-)

diff --git a/fcore/search-list/search-list.sml b/fcore/search-list/search-list.sml
index a20c2cb..e4f396f 100644
--- a/fcore/search-list/search-list.sml
+++ b/fcore/search-list/search-list.sml
@@ -175,15 +175,19 @@ struct
       end
 
   fun tryExtendingPrevMatch
-    (idx, buffer, searchList, dfa, prevMatchFinish, finalPos, curState) =
+    (idx, buffer, searchList, dfa, finalPos, curState, start) =
     if idx = #textLength buffer then
-      if finalPos = prevMatchFinish then
-        (* call insertUntilMatch *)
-        0
-      else
-        (* update searchList, replacing prevMatchFinish with finalPos,
-         * and then call insertUntilMatch with new searchList *)
-        0
+      (* reached end of buffer without finding anything
+       * so return current buffer and searchList *)
+      (buffer, searchList)
+    else if Dfa.isDead curState then
+      let
+        val searchList =
+          PersistentVector.extendExistingMatch (start, finalPos, searchList)
+      in
+        insertUntilMatch
+          (finalPos + 1, buffer, searchList, dfa, 0, finalPos + 1, ~1)
+      end
     else
       let
         val buffer = LineGap.goToIdx (idx, buffer)
@@ -191,40 +195,24 @@ struct
         val newState = Dfa.nextState (dfa, curState, chr)
         val finalPos = if Dfa.isFinal (dfa, newState) then idx else finalPos
       in
-        if Dfa.isDead newState then
-          if finalPos = prevMatchFinish then
-            (* call insertUntilMatch *)
-            0
-          else
-            (* update searchList, replacing prevMatchFinish with finalPos,
-             * and then call insertUntilMatch with new searchList *)
-            0
-        else
-          (* continue *)
-          tryExtendingPrevMatch
-            ( idx + 1
-            , buffer
-            , searchList
-            , dfa
-            , prevMatchFinish
-            , finalPos
-            , newState
-            )
+        (* continue *)
+        tryExtendingPrevMatch
+          (idx + 1, buffer, searchList, dfa, finalPos, newState, start)
       end
 
   fun deleteBufferAndSearchList (start, length, buffer, searchList, dfa) =
     let
       val buffer = LineGap.delete (start, length, buffer)
       val searchList = PersistentVector.delete (start, length, searchList)
-
-      val {finish = searchStart, ...} =
-        PersistentVector.helpPrevMatch (start, searchList, 0)
-      val searchStart = searchStart + 1
+      val oldStart = PersistentVector.prevMatch (start, searchList, 1)
     in
       if Vector.length dfa = 0 then
         (buffer, searchList)
+      else if oldStart >= start orelse oldStart = ~1 then
+        (* no previous match, so try searching for a match from start of buffer *)
+        insertUntilMatch (0, buffer, searchList, dfa, 0, 0, ~1)
       else
-        insertUntilMatch
-          (searchStart, buffer, searchList, dfa, 0, searchStart, ~1)
+        tryExtendingPrevMatch
+          (oldStart, buffer, searchList, dfa, ~1, 0, oldStart)
     end
 end
diff --git a/todo.md b/todo.md
index eb3ca42..cc9773e 100644
--- a/todo.md
+++ b/todo.md
@@ -1,8 +1,5 @@
 # To-do list
 - Make sure that all delete function in make-normal-delete.sml also delete from searchList
-- Handle edge cases regarding deletion from searchList.
-  - Edge case 1: deletion causes a match to be extended
-  - Any other edge cases possible?
 - Add normal-delete tests for each motion, checking that searchList is as expected
 - Add tests for other yank motoins
   - Tests should be based on existing tests for delete-motions, and in the same order.