Extract domain-specific Cell utilities from Util to CellUtilities

Refactors utility organization by separating domain model concerns:
- Creates CellUtilities object for Cell-specific operations (assertNodeCell, toClass)
- Keeps Util focused on type-agnostic utilities (assertInstanceOf)
- Updates 4 files to use CellUtilities for domain operations
- Simplifies RailwayNetGridCanvas context handling
- Improves code organization and separation of concerns

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: bedaHovorka

src/main/kotlin/cz/vutbr/fit/interlockSim/context/DefaultContext.kt

@@ -35,12 +35,13 @@ import cz.vutbr.fit.interlockSim.exceptions.requireValidState
 import cz.vutbr.fit.interlockSim.objects.cells.anti
 import cz.vutbr.fit.interlockSim.objects.cells.conflict
 import cz.vutbr.fit.interlockSim.objects.cells.segmentFor
+import cz.vutbr.fit.interlockSim.objects.cells.CellUtilities
 import cz.vutbr.fit.interlockSim.util.ExtendedUnorientedGraph
 import cz.vutbr.fit.interlockSim.util.HashMapGraph
 import cz.vutbr.fit.interlockSim.util.Point
+import cz.vutbr.fit.interlockSim.util.Util
 import cz.vutbr.fit.interlockSim.util.putMulti
 import cz.vutbr.fit.interlockSim.util.valuesMulti
-import cz.vutbr.fit.interlockSim.util.Util
 import io.github.oshai.kotlinlogging.KotlinLogging
 import jDisco.DiscoException
 import jDisco.Process
@@ -239,8 +240,8 @@ abstract class DefaultContext :
 
 		if (key1.distance(key2) <= SQRT2) return null
 
-		val nodecell1: NodeCell = Util.assertNodeCell(getGrid().get(key1)!!)
-		val nodecell2: NodeCell = Util.assertNodeCell(getGrid().get(key2)!!)
+		val nodecell1: NodeCell = CellUtilities.assertNodeCell(getGrid().get(key1)!!)
+		val nodecell2: NodeCell = CellUtilities.assertNodeCell(getGrid().get(key2)!!)
 
 		for (s1: Segment in nodecell1.joins()) {
 			val p1 = s1.transform(key1)
@@ -665,7 +666,7 @@ abstract class DefaultContext :
 			// Match Java 1:1: return directly (inner method should not return null here)
 			getSegment(separator, section) ?: throw IllegalStateException("getSegment returned null for TrackSection")
 		} else {
-			val nodeCell: NodeCell = Util.assertNodeCell(separator)
+			val nodeCell: NodeCell = CellUtilities.assertNodeCell(separator)
 			val trackBlock: TrackBlock = Util.assertInstanceOf(TrackBlock::class.java, track)
 			// Match Java 1:1: return directly (inner method should not return null here)
 			getSegment(nodeCell, trackBlock as TrackBlock?)
@@ -683,7 +684,7 @@ abstract class DefaultContext :
 		if (trackBlock.isInnerElement(separator)) {
 			return trackBlock.getJoin(separator, section)
 		}
-		val nodeCell: NodeCell = Util.assertNodeCell(separator)
+		val nodeCell: NodeCell = CellUtilities.assertNodeCell(separator)
 		return getSegment(nodeCell, trackBlock as TrackBlock?)
 	}
 
@@ -759,7 +760,7 @@ abstract class DefaultContext :
 		}
 
 		// z dalsi TrackBlock
-		val nodeCell = Util.assertNodeCell(separator)
+		val nodeCell = CellUtilities.assertNodeCell(separator)
 		val nextTrackBlock = getNextTrackBlock(nodeCell, trackBlock)
 
 		@Suppress("UNCHECKED_CAST")

src/main/kotlin/cz/vutbr/fit/interlockSim/gui/RailwayNetGridCanvas.kt

@@ -12,7 +12,6 @@ package cz.vutbr.fit.interlockSim.gui
 import cz.vutbr.fit.interlockSim.context.Context
 import cz.vutbr.fit.interlockSim.context.EditingContext
 import cz.vutbr.fit.interlockSim.context.EditingContextFactory
-import cz.vutbr.fit.interlockSim.context.SimulationContext
 import cz.vutbr.fit.interlockSim.exceptions.requireEditor
 import cz.vutbr.fit.interlockSim.gui.gridcanvas.CellRenderer
 import cz.vutbr.fit.interlockSim.gui.gridcanvas.EditorCellRenderer
@@ -202,11 +201,11 @@ class RailwayNetGridCanvas :
 				state = State.EDITING
 				changeListeners(simulationControlListener, editListener)
 			}
-		 is SimulationContext -> {
+			else -> {
+				// Covers SimulationContext and any future context types
 				state = State.SIMULATION
 				changeListeners(editListener, simulationControlListener)
 			}
-		 else -> error("Unknown context type: ${newContext.javaClass}")
 		}
 		changeContext(newContext)
 	}
@@ -333,8 +332,8 @@ class RailwayNetGridCanvas :
 	}
 
 	@Deprecated("Use setContext instead")
-	fun setSimulation(simulationContext: SimulationContext) {
-		setContext(simulationContext)
+	fun setSimulation(context: Context) {
+		setContext(context)
 	}
 
 	// Scrollable interface implementation

src/main/kotlin/cz/vutbr/fit/interlockSim/objects/cells/CellUtilities.kt

@@ -0,0 +1,69 @@
+/* Brno University of Technology
+ * Faculty of Information Technology
+ *
+ * BSc Thesis  2006/2007
+ *
+ * Railway Interlocking Simulator
+ *
+ * Bedrich Hovorka
+ */
+package cz.vutbr.fit.interlockSim.objects.cells
+
+import cz.vutbr.fit.interlockSim.context.SimulationContext
+import cz.vutbr.fit.interlockSim.exceptions.requireValidState
+
+/**
+ * Domain-specific utility functions for working with Cell objects.
+ *
+ * This object contains utilities that depend on domain model classes (NodeCell, SimulationContext).
+ * For type-agnostic utilities, see [cz.vutbr.fit.interlockSim.util.Util].
+ */
+object CellUtilities {
+	/**
+	 * Most used cast in program - asserts and casts to NodeCell
+	 * @param obj object to cast
+	 * @return casted NodeCell instance
+	 * @throws IllegalStateException if obj is not a NodeCell
+	 */
+	fun assertNodeCell(obj: Any): NodeCell {
+		requireValidState(obj is NodeCell) { "Expected instance of NodeCell but got ${obj.javaClass.name}: $obj" }
+		return obj as NodeCell
+	}
+
+	/**
+	 * Converts object to its class, with special handling for SimulationContext.
+	 *
+	 * This method is designed specifically for InterlockSim's reflection needs.
+	 * SimulationContext instances are always represented by the SimulationContext interface class,
+	 * not their concrete implementation class.
+	 *
+	 * @param o object to convert
+	 * @return Class representing the object's type
+	 */
+	fun toClass(o: Any): Class<*> {
+		val class1 = o.javaClass
+		return if (SimulationContext::class.java.isAssignableFrom(class1)) SimulationContext::class.java else class1
+	}
+
+	/**
+	 * Converts array of objects to array of classes, with special handling for domain types.
+	 *
+	 * This method is designed specifically for InterlockSim's reflection needs.
+	 * Uses [toClass] for individual object conversion, which applies special handling for SimulationContext.
+	 *
+	 * @param objects array of objects (null values allowed)
+	 * @return array of classes representing types of objects (null for null inputs)
+	 * @throws IllegalStateException if any object is an array (arrays not supported)
+	 */
+	fun toClass(objects: Array<out Any?>): Array<Class<*>?> {
+		val classes = arrayOfNulls<Class<*>>(objects.size)
+		for (i in objects.indices) {
+			val obj = objects[i]
+			if (obj != null) {
+				requireValidState(!obj.javaClass.isArray) { "Arrays are not supported as input objects" }
+				classes[i] = toClass(obj)
+			}
+		}
+		return classes
+	}
+}

src/main/kotlin/cz/vutbr/fit/interlockSim/util/AbstractUnorientedGraph.kt

@@ -10,6 +10,7 @@
 package cz.vutbr.fit.interlockSim.util
 
 import cz.vutbr.fit.interlockSim.exceptions.requireValidState
+import cz.vutbr.fit.interlockSim.objects.cells.CellUtilities
 import java.lang.reflect.InvocationTargetException
 import java.util.Collection
 import java.util.Map
@@ -48,7 +49,7 @@ abstract class AbstractUnorientedGraph<N, E> : UnorientedGraph<N, E> {
 		val methodName = e.methodName
 		try {
 			@Suppress("UNCHECKED_CAST")
-			val classArray = Util.toClass(args) as Array<Class<*>?>
+			val classArray = CellUtilities.toClass(args) as Array<Class<*>?>
 			val method = o.javaClass.getMethod(methodName, *classArray)
 			return method.invoke(o, *args)
 		} catch (ee: InvocationTargetException) {

src/main/kotlin/cz/vutbr/fit/interlockSim/util/Util.kt

@@ -9,50 +9,23 @@
  */
 package cz.vutbr.fit.interlockSim.util
 
-import cz.vutbr.fit.interlockSim.context.SimulationContext
 import cz.vutbr.fit.interlockSim.exceptions.requireValidState
-import cz.vutbr.fit.interlockSim.objects.cells.NodeCell
 
 /**
- * Collection of shared static methods
+ * Collection of type-agnostic utility methods.
  *
+ * For domain-specific utilities (e.g., working with Cell objects),
+ * see [cz.vutbr.fit.interlockSim.objects.cells.CellUtilities].
  */
 object Util {
-	private fun toClass(o: Any): Class<*> {
-		val class1 = o.javaClass
-		return if (SimulationContext::class.java.isAssignableFrom(class1)) SimulationContext::class.java else class1
-	}
-
-	/**
-	 * This method is designed specifically for InterlockSim
-	 * @param objects array of objects
-	 * @return array of classes which represent types of objects
-	 */
-	fun toClass(objects: Array<out Any?>): Array<Class<*>?> {
-		val classes = arrayOfNulls<Class<*>>(objects.size)
-		for (i in objects.indices) {
-			val obj = objects[i]
-			if (obj != null) {
-				requireValidState(!obj.javaClass.isArray) { "Arrays are not supported as input objects" }
-				classes[i] = toClass(obj)
-			}
-		}
-		return classes
-	}
-
-	/**
-	 * Most used cast in program
-	 * @param obj
-	 * @return casted instance
-	 */
-	fun assertNodeCell(obj: Any): NodeCell = assertInstanceOf(NodeCell::class.java, obj)
-
 	/**
-	 * assert and cast routine
-	 * @param <T>
-	 * @param clazz
-	 * @param obj
-	 * @return casted instance
+	 * Generic type assertion and cast utility.
+	 *
+	 * @param T target type
+	 * @param clazz target class to cast to
+	 * @param obj object to cast
+	 * @return casted instance of type T
+	 * @throws IllegalStateException if obj is not an instance of clazz
 	 */
 	fun <T> assertInstanceOf(
 		clazz: Class<T>,

src/main/kotlin/cz/vutbr/fit/interlockSim/xml/XMLContextFactory.kt

@@ -28,6 +28,7 @@ import cz.vutbr.fit.interlockSim.objects.paths.OrientedPathSeparator
 import cz.vutbr.fit.interlockSim.objects.paths.PathElement
 import cz.vutbr.fit.interlockSim.objects.tracks.SimpleTrackBlock
 import cz.vutbr.fit.interlockSim.objects.tracks.TrackBlock
+import cz.vutbr.fit.interlockSim.objects.cells.CellUtilities
 import cz.vutbr.fit.interlockSim.util.Doubleton
 import cz.vutbr.fit.interlockSim.util.Point
 import cz.vutbr.fit.interlockSim.util.Util
@@ -149,8 +150,8 @@ class XMLContextFactory :
 				check(from != to) { "from and to points must be different" }
 
 				val railwayNetGrid = ctx.getRailWayNetGrid()
-				val fromNode = Util.assertNodeCell(railwayNetGrid[from] as Any)
-				val toNode = Util.assertNodeCell(railwayNetGrid[to] as Any)
+				val fromNode = CellUtilities.assertNodeCell(railwayNetGrid[from] as Any)
+				val toNode = CellUtilities.assertNodeCell(railwayNetGrid[to] as Any)
 
 				val segmentFrom =
 					getEnum(uri, attributes, Segment::class.java, FROM)

src/test/kotlin/cz/vutbr/fit/interlockSim/util/UtilTest.kt

@@ -1,6 +1,7 @@
 package cz.vutbr.fit.interlockSim.util
 
 import cz.vutbr.fit.interlockSim.objects.cells.Cell
+import cz.vutbr.fit.interlockSim.objects.cells.CellUtilities
 import cz.vutbr.fit.interlockSim.objects.cells.NodeCell
 import assertk.assertThat
 import assertk.assertions.isEqualTo
@@ -15,7 +16,7 @@ class UtilTest {
 	@Test
 	fun `toClass array returns actual class for non-SimulationContext objects`() {
 		val dummy = RailSemaphore(false, Cell.SpatialType.HORIZONTAL)
-		val result = Util.toClass(arrayOf(dummy))
+		val result = CellUtilities.toClass(arrayOf(dummy))
 		assertThat(result.size).isEqualTo(1)
 		assertThat(result[0]).isEqualTo(RailSemaphore::class.java)
 	}
@@ -27,7 +28,7 @@ class UtilTest {
 		val obj3 = 42
 		val objects = arrayOf(obj1, obj2, obj3)
 
-		val result = Util.toClass(objects)
+		val result = CellUtilities.toClass(objects)
 
 		assertThat(result.size).isEqualTo(3)
 		assertThat(result[0]).isEqualTo(RailSemaphore::class.java)
@@ -40,7 +41,7 @@ class UtilTest {
 		val obj1 = RailSemaphore(false, Cell.SpatialType.HORIZONTAL)
 		val objects = arrayOf<Any?>(obj1, null, "test")
 
-		val result = Util.toClass(objects)
+		val result = CellUtilities.toClass(objects)
 
 		assertThat(result.size).isEqualTo(3)
 		assertThat(result[0]).isEqualTo(RailSemaphore::class.java)
@@ -51,21 +52,21 @@ class UtilTest {
 	@Test
 	fun `toClass array returns empty array for empty input`() {
 		val objects = emptyArray<Any>()
-		val result = Util.toClass(objects)
+		val result = CellUtilities.toClass(objects)
 		assertThat(result.size).isEqualTo(0)
 	}
 
 	@Test
 	fun `assertNodeCell returns NodeCell when correct type`() {
 		val dummy = RailSemaphore(false, Cell.SpatialType.HORIZONTAL)
-		val result = Util.assertNodeCell(dummy)
+		val result = CellUtilities.assertNodeCell(dummy)
 		assertThat(result).isSameInstanceAs(dummy)
 	}
 
 	@Test
 	fun `assertNodeCell throws AssertionError for wrong type`() {
 		val dummy = "String"
-		assertThrows<IllegalStateException> { Util.assertNodeCell(dummy) }
+		assertThrows<IllegalStateException> { CellUtilities.assertNodeCell(dummy) }
 	}
 
 	@Test