From ea7a59808a46bc54a85c43f8e2a59b9def428036 Mon Sep 17 00:00:00 2001
From: Michael Vetter <jubalh@iodoru.org>
Date: Wed, 25 Feb 2026 11:41:30 +0100
Subject: [PATCH] refactor: optimize prof_occurrences()

Optimize prof_occurrences by using pointer arithmetic and
g_utf8_next_char instead of calls to g_utf8_offset_to_pointer.

Improve list construction efficiency in prof_occurrences by
using g_slist_prepend and g_slist_reverse instead of appends.

Also fix a slight oversight that could lead to trouble:
When empty search strings (e.g. empty nicks) are passed
it caused matches at every position.

Update the test case to test for empty nicks.
---
 src/common.c                  | 32 ++++++++++++++++++++++----------
 tests/unittests/test_common.c |  5 +++++
 2 files changed, 27 insertions(+), 10 deletions(-)

diff --git a/src/common.c b/src/common.c
index d5acb211..96f5cac6 100644
--- a/src/common.c
+++ b/src/common.c
@@ -578,36 +578,48 @@ is_notify_enabled(void)
 GSList*
 prof_occurrences(const char* const needle, const char* const haystack, int offset, gboolean whole_word, GSList** result)
 {
-    if (needle == NULL || haystack == NULL) {
+    if (needle == NULL || haystack == NULL || *needle == '\0') {
         return *result;
     }
 
-    do {
-        gchar* haystack_curr = g_utf8_offset_to_pointer(haystack, offset);
-        if (g_str_has_prefix(haystack_curr, needle)) {
+    size_t needle_len = strlen(needle);
+    gchar* p = g_utf8_offset_to_pointer(haystack, offset);
+    GSList* matches = NULL;
+
+    while (p) {
+        if (g_str_has_prefix(p, needle)) {
             if (whole_word) {
                 gunichar before = 0;
-                gchar* haystack_before_ch = g_utf8_find_prev_char(haystack, haystack_curr);
+                gchar* haystack_before_ch = g_utf8_find_prev_char(haystack, p);
                 if (haystack_before_ch) {
                     before = g_utf8_get_char(haystack_before_ch);
                 }
 
                 gunichar after = 0;
-                gchar* haystack_after_ch = haystack_curr + strlen(needle);
-                if (haystack_after_ch[0] != '\0') {
+                gchar* haystack_after_ch = p + needle_len;
+                if (*haystack_after_ch != '\0') {
                     after = g_utf8_get_char(haystack_after_ch);
                 }
 
                 if (!g_unichar_isalnum(before) && !g_unichar_isalnum(after)) {
-                    *result = g_slist_append(*result, GINT_TO_POINTER(offset));
+                    matches = g_slist_prepend(matches, GINT_TO_POINTER(offset));
                 }
             } else {
-                *result = g_slist_append(*result, GINT_TO_POINTER(offset));
+                matches = g_slist_prepend(matches, GINT_TO_POINTER(offset));
             }
         }
 
+        if (*p == '\0') {
+            break;
+        }
+
+        p = g_utf8_next_char(p);
         offset++;
-    } while (g_strcmp0(g_utf8_offset_to_pointer(haystack, offset), "\0") != 0);
+    }
+
+    if (matches) {
+        *result = g_slist_concat(*result, g_slist_reverse(matches));
+    }
 
     return *result;
 }
diff --git a/tests/unittests/test_common.c b/tests/unittests/test_common.c
index 6e96ef18..40912679 100644
--- a/tests/unittests/test_common.c
+++ b/tests/unittests/test_common.c
@@ -923,6 +923,11 @@ get_mentions_tests(void** state)
     assert_true(_lists_equal(actual, expected)); // expected is NULL
     g_slist_free(actual); actual = NULL;
 
+    // Empty nick
+    actual = get_mentions(FALSE, TRUE, "hello", "");
+    assert_true(_lists_equal(actual, expected)); // expected is NULL
+    g_slist_free(actual); actual = NULL;
+
     // UTF-8 characters
     expected = g_slist_append(expected, GINT_TO_POINTER(0));
     actual = get_mentions(TRUE, TRUE, "我能 hello", "我能");