Add Lyng DB contract and SQLite provider skeleton

lyngio/src/commonTest/kotlin/net/sergeych/lyng/io/db/LyngDbModuleTest.kt

@@ -0,0 +1,134 @@
+/*
+ * Copyright 2026 Sergey S. Chernov real.sergeych@gmail.com
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package net.sergeych.lyng.io.db
+
+import kotlinx.coroutines.test.runTest
+import net.sergeych.lyng.Compiler
+import net.sergeych.lyng.ExecutionError
+import net.sergeych.lyng.pacman.ImportManager
+import net.sergeych.lyng.Pos
+import net.sergeych.lyng.Script
+import net.sergeych.lyng.Source
+import net.sergeych.lyng.obj.Obj
+import net.sergeych.lyng.obj.ObjExternCallable
+import net.sergeych.lyng.obj.ObjInt
+import net.sergeych.lyng.obj.ObjNull
+import net.sergeych.lyng.obj.ObjString
+import net.sergeych.lyng.obj.requiredArg
+import net.sergeych.lyng.requireScope
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertFailsWith
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
+
+class LyngDbModuleTest {
+
+    @Test
+    fun testModuleRegistrationIsIdempotent() = runTest {
+        val importManager = ImportManager()
+        assertTrue(createDbModule(importManager))
+        assertFalse(createDbModule(importManager))
+    }
+
+    @Test
+    fun testOpenDatabaseDispatchesByNormalizedScheme() = runTest {
+        val scope = Script.newScope()
+        createDbModule(scope.importManager)
+        val module = scope.importManager.createModuleScope(Pos.builtIn, "lyng.io.db")
+
+        module.callFn(
+            "registerDatabaseProvider",
+            ObjString("TeSt"),
+            ObjExternCallable.fromBridge {
+                val url = requiredArg<ObjString>(0).value
+                val params = requiredArg<Obj>(1)
+                val size = (params.invokeInstanceMethod(requireScope(), "size") as ObjInt).value
+                ObjString("$url|$size")
+            }
+        )
+
+        val code = """
+            import lyng.io.db
+            openDatabase("TEST:demo", Map("a" => 1, "b" => 2))
+        """.trimIndent()
+
+        val result = Compiler.compile(Source("<db-test>", code), scope.importManager).execute(scope) as ObjString
+        assertEquals("TEST:demo|2", result.value)
+    }
+
+    @Test
+    fun testDuplicateSchemeRegistrationFailsCaseInsensitively() = runTest {
+        val importManager = Script.defaultImportManager.copy()
+        createDbModule(importManager)
+        val module = importManager.createModuleScope(Pos.builtIn, "lyng.io.db")
+
+        module.callFn("registerDatabaseProvider", ObjString("sqlite"), trivialOpener())
+        val error = try {
+            module.callFn("registerDatabaseProvider", ObjString("SQLITE"), trivialOpener())
+            kotlin.test.fail("expected duplicate registration to fail")
+        } catch (e: ExecutionError) {
+            e
+        }
+
+        assertTrue(error.errorMessage.contains("already registered"), error.errorMessage)
+    }
+
+    @Test
+    fun testMalformedUrlFailsWithIllegalArgument() = runTest {
+        val scope = Script.newScope()
+        createDbModule(scope.importManager)
+
+        val code = """
+            import lyng.io.db
+            openDatabase("not-a-url", Map())
+        """.trimIndent()
+
+        val error = assertFailsWith<ExecutionError> {
+            Compiler.compile(Source("<db-test>", code), scope.importManager).execute(scope)
+        }
+
+        assertEquals("IllegalArgumentException", error.errorObject.objClass.className)
+        assertTrue(error.errorMessage.contains("Malformed database connection URL"), error.errorMessage)
+    }
+
+    @Test
+    fun testUnknownSchemeFailsWithDatabaseException() = runTest {
+        val scope = Script.newScope()
+        createDbModule(scope.importManager)
+
+        val code = """
+            import lyng.io.db
+            openDatabase("unknown:demo", Map())
+        """.trimIndent()
+
+        val error = assertFailsWith<ExecutionError> {
+            Compiler.compile(Source("<db-test>", code), scope.importManager).execute(scope)
+        }
+
+        assertEquals("DatabaseException", error.errorObject.objClass.className)
+        assertTrue(error.errorMessage.contains("No database provider registered"), error.errorMessage)
+    }
+
+    private suspend fun net.sergeych.lyng.ModuleScope.callFn(name: String, vararg args: Obj): Obj {
+        val callee = get(name)?.value ?: error("Missing $name in module")
+        return callee.invoke(this, ObjNull, *args)
+    }
+
+    private fun trivialOpener(): Obj = ObjExternCallable.fromBridge { ObjInt.One }
+}