Replace the Levenshtein sort with indexOf

Author: andremion

stream-chat-android-ui-common/src/main/kotlin/io/getstream/chat/android/ui/common/feature/messages/composer/query/filter/DefaultUserQueryFilter.kt

@@ -24,14 +24,13 @@ import io.getstream.chat.android.ui.common.feature.messages.composer.query.forma
 import io.getstream.chat.android.ui.common.feature.messages.composer.transliteration.DefaultStreamTransliterator
 import io.getstream.chat.android.ui.common.feature.messages.composer.transliteration.StreamTransliterator
 import io.getstream.log.taggedLogger
-import kotlin.math.min
 
 /**
  * Default [QueryFilter] for [User] objects used in mention suggestions.
  *
  * Keeps only users whose normalized name (or id) contains the normalized query as a substring,
- * then sorts results by Levenshtein distance so the closest matches appear first. Normalization
- * applies lowercasing, diacritics removal, and optional transliteration.
+ * then sorts results by match position so prefix matches appear first. Normalization applies
+ * lowercasing, diacritics removal, and optional transliteration.
  *
  * @param transliterator The transliterator to use for normalizing strings.
  */
@@ -54,47 +53,10 @@ public class DefaultUserQueryFilter(
         return items
             .mapNotNull { user ->
                 val formattedName = queryFormatter.format(query = user.name.ifBlank(user::id))
-                if (formattedName.contains(formattedQuery)) {
-                    user to levenshteinDistance(formattedQuery, formattedName)
-                } else {
-                    null
-                }
+                val index = formattedName.indexOf(formattedQuery)
+                if (index >= 0) user to index else null
             }
-            .sortedBy { (_, distance) -> distance }
+            .sortedBy { (_, index) -> index }
             .map { (user, _) -> user }
     }
-
-    private fun levenshteinDistance(search: String, target: String): Int {
-        when {
-            search == target -> return 0
-            search.isEmpty() -> return target.length
-            target.isEmpty() -> return search.length
-        }
-
-        val searchLength = search.length + 1
-        val targetLength = target.length + 1
-
-        var cost = Array(searchLength) { it }
-        var newCost = Array(searchLength) { 0 }
-
-        for (i in 1 until targetLength) {
-            newCost[0] = i
-
-            for (j in 1 until searchLength) {
-                val match = if (search[j - 1] == target[i - 1]) 0 else 1
-
-                val costReplace = cost[j - 1] + match
-                val costInsert = cost[j] + 1
-                val costDelete = newCost[j - 1] + 1
-
-                newCost[j] = min(min(costInsert, costDelete), costReplace)
-            }
-
-            val swap = cost
-            cost = newCost
-            newCost = swap
-        }
-
-        return cost[searchLength - 1]
-    }
 }

stream-chat-android-ui-common/src/test/kotlin/io/getstream/chat/android/ui/common/feature/messages/composer/query/filter/DefaultUserQueryFilterTest.kt

@@ -74,10 +74,10 @@ internal class DefaultUserQueryFilterTest {
     }
 
     @Test
-    fun `results are sorted by levenshtein distance`() {
-        val users = listOf(user("Charlie Alice"), user("Alice"), user("Bob Alice Smith"))
+    fun `results are sorted by match position`() {
+        val users = listOf(user("Johann"), user("Anne"), user("Marianne"))
 
-        assertEquals(listOf("Alice", "Charlie Alice", "Bob Alice Smith"), filter.filter(users, "alice").names())
+        assertEquals(listOf("Anne", "Johann", "Marianne"), filter.filter(users, "ann").names())
     }
 
     @Test