Add fuzzy user search with levenshtein

Sources/src/main/kotlin/allin/data/postgres/PostgresDataSource.kt

@@ -25,6 +25,12 @@ class PostgresDataSource : AllInDataSource() {
             dialect = PostgreSqlDialect()
         )
 
+        database.execute(
+            """
+                CREATE EXTENSION IF not exists fuzzystrmatch;
+            """.trimIndent()
+        )
+
         database.execute(
             """
             CREATE TABLE IF not exists users ( 

Sources/src/main/kotlin/allin/data/postgres/PostgresFriendDataSource.kt

@@ -5,12 +5,12 @@ import allin.data.postgres.entities.FriendEntity
 import allin.data.postgres.entities.friends
 import allin.data.postgres.entities.users
 import allin.dto.UserDTO
+import allin.ext.levenshtein
 import allin.ext.toLowerCase
 import allin.model.FriendStatus
 import org.ktorm.database.Database
 import org.ktorm.dsl.and
 import org.ktorm.dsl.eq
-import org.ktorm.dsl.like
 import org.ktorm.dsl.notEq
 import org.ktorm.entity.*
 
@@ -48,6 +48,8 @@ class PostgresFriendDataSource(private val database: Database) : FriendDataSourc
 
     override fun filterUsersByUsername(fromUserId: String, search: String): List<UserDTO> =
         database.users
-            .filter { (it.username.toLowerCase() like "%$search%") and (it.id notEq fromUserId) }
+            .filter { it.id notEq fromUserId }
+            .sortedBy { it.username.toLowerCase().levenshtein(search.lowercase()) }
+            .take(10)
             .map { user -> user.toUserDTO(friendStatus = getFriendStatus(fromUserId, user.id)) }
 }

Sources/src/main/kotlin/allin/ext/DatabaseExt.kt

@@ -3,6 +3,7 @@ package allin.ext
 import org.ktorm.database.Database
 import org.ktorm.expression.FunctionExpression
 import org.ktorm.schema.ColumnDeclaring
+import org.ktorm.schema.IntSqlType
 import org.ktorm.schema.VarcharSqlType
 import java.sql.ResultSet
 
@@ -46,3 +47,14 @@ fun ColumnDeclaring<String>.toUpperCase(): FunctionExpression<String> {
         sqlType = VarcharSqlType
     )
 }
+
+fun ColumnDeclaring<String>.levenshtein(target: ColumnDeclaring<String>): FunctionExpression<Int> {
+    return FunctionExpression(
+        functionName = "levenshtein",
+        arguments = listOf(this.asExpression(), target.asExpression()),
+        sqlType = IntSqlType
+    )
+}
+
+fun ColumnDeclaring<String>.levenshtein(target: String): FunctionExpression<Int> =
+    levenshtein(wrapArgument(target))