Replace assert() with typed exception functions for better error handling

Converts assert() calls throughout the codebase to use typed exception functions (requireEditor, requireSimulation, requireValidArgument, requireValidState). This improves error messages by providing specific context and enables runtime validation even when assertions are disabled.

Changes:
- Replace assert() with requireEditor/requireSimulation in domain model and GUI
- Add descriptive error messages for all validation failures
- Improve debugging by identifying exact validation failure points
- Standardize exception handling patterns across the codebase

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

Author: bedaHovorka

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

@@ -28,6 +28,12 @@ import cz.vutbr.fit.interlockSim.sim.InOutWorker
 import cz.vutbr.fit.interlockSim.sim.LoopProcess
 import cz.vutbr.fit.interlockSim.sim.ShuntingLoop
 import cz.vutbr.fit.interlockSim.exceptions.SimulationException
+import cz.vutbr.fit.interlockSim.exceptions.requireEditor
+import cz.vutbr.fit.interlockSim.exceptions.requireEditorNotNull
+import cz.vutbr.fit.interlockSim.exceptions.requireSimulation
+import cz.vutbr.fit.interlockSim.exceptions.requireSimulationNotNull
+import cz.vutbr.fit.interlockSim.exceptions.requireValidArgument
+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
@@ -211,11 +217,11 @@ abstract class DefaultContext :
 		val nodecell2: NodeCell = Util.assertNodeCell(getGrid().get(key2)!!)
 
 		for (s1: Segment in nodecell1.joins()) {
-			assert(s1 != null) { nodecell1 }
+			requireEditorNotNull(s1) { "Segment s1 cannot be null for nodecell $nodecell1" }
 			val p1 = s1.transform(key1)
 			if (used(p1)) continue
 			for (s2: Segment in nodecell2.joins()) {
-				assert(s2 != null) { nodecell2 }
+				requireEditorNotNull(s2) { "Segment s2 cannot be null for nodecell $nodecell2" }
 				if (s1 == s2) continue // stejne segmenty se nepropoji
 				val p2 = s2.transform(key2)
 				if (used(p2)) continue
@@ -250,7 +256,7 @@ abstract class DefaultContext :
 		key2: Point,
 		trackBlock: TrackBlock
 	): Boolean {
-		assert(key1 != null && key2 != null)
+		requireEditor(key1 != null && key2 != null) { "Keys cannot be null in hardJoin" }
 		if (key1.distance(key2) > SQRT2) {
 			val blockEndFrom = s1.transform(key1)
 			val blockEndTo = s2.transform(key2)
@@ -309,7 +315,9 @@ abstract class DefaultContext :
 			@Suppress("UNCHECKED_CAST")
 			val mapKeys: Set<Point> = mapToAdd.keySet() as Set<Point>
 			linesKeys[trackBlock] = mapKeys
-			assert(!extendedUnorientedGraph.contains(key1, key2))
+			requireValidState(!extendedUnorientedGraph.contains(key1, key2)) {
+				"Graph already contains edge between ($key1, $key2)"
+			}
 			extendedUnorientedGraph.put(key1, s1, key2, s2, trackBlock)
 			return mapToAdd
 		}
@@ -325,7 +333,9 @@ abstract class DefaultContext :
 		key2: Point,
 		trackBlock: TrackBlock
 	): MutableMap<Point, TrackBlockPart>? {
-		assert(bresenham != null && bresenham.isNotEmpty())
+		requireValidArgument(bresenham != null && bresenham.isNotEmpty()) {
+			"Bresenham path list cannot be null or empty"
+		}
 		val map: MutableMap<Point, TrackBlockPart> = LinkedHashMap()
 		var from = key1
 		var middle = bresenham[0]
@@ -358,7 +368,7 @@ abstract class DefaultContext :
 		to: Point,
 		block: TrackBlock
 	): TrackBlockPart? {
-		assert(block != null)
+		requireEditorNotNull(block) { "TrackBlock cannot be null in createPart" }
 		if (used(middle)) return null
 		if (from == to || from == middle || middle == to) return null
 
@@ -390,8 +400,12 @@ abstract class DefaultContext :
 		p2: Point,
 		points: MutableList<Point>
 	): Boolean {
-		assert(key1 != null && key2 != null && p1 != null && p2 != null)
-		assert(key1 != p1 && key2 != p2 && key1 != p2 && key2 != p1)
+		requireValidArgument(key1 != null && key2 != null && p1 != null && p2 != null) {
+			"All points must be non-null in bresenham algorithm"
+		}
+		requireValidArgument(key1 != p1 && key2 != p2 && key1 != p2 && key2 != p1) {
+			"Keys and intermediate points must be distinct in bresenham algorithm"
+		}
 
 		// Make mutable copies since we need to modify them for the algorithm
 		var p1Mut = p1
@@ -508,7 +522,7 @@ abstract class DefaultContext :
 		key: Point,
 		nodeCell: NodeCell
 	) {
-		assert(key != null)
+		requireEditorNotNull(key) { "Cell key cannot be null in putCell" }
 		// Validate coordinates are within grid bounds
 		if (key.x < 0 || key.y < 0 || key.x >= railwayNetGrid.getCols() || key.y >= railwayNetGrid.getRows()) {
 			throw ContextCreationException(
@@ -520,7 +534,7 @@ abstract class DefaultContext :
 
 		// vedlejsi Nody (sousedni bunky)
 		for (s1: Segment in nodeCell.joins()) {
-			assert(s1 != null) { nodeCell }
+			requireEditorNotNull(s1) { "Segment s1 cannot be null for nodeCell $nodeCell" }
 			val p = s1.transform(key)
 			// Skip neighbor if it's outside grid bounds (boundary cells)
 			if (p.x < 0 || p.y < 0 || p.x >= railwayNetGrid.getCols() || p.y >= railwayNetGrid.getRows()) {
@@ -533,7 +547,9 @@ abstract class DefaultContext :
 			// vzit proti-segment
 			val s2 = anti(s1)
 			if (nodeCell2.joins().contains(s2)) {
-				assert(s2.transform(p) == key)
+				requireValidState(s2.transform(p) == key) {
+					"Segment transformation inconsistency: s2.transform($p) != $key"
+				}
 				extendedUnorientedGraph.putIfNotExists(
 					key,
 					s1,
@@ -577,7 +593,7 @@ abstract class DefaultContext :
 	 * Remove a track line from the railway network
 	 */
 	override fun removeLine(line: TrackBlock) {
-		assert(line != null)
+		requireEditorNotNull(line) { "TrackBlock line cannot be null in removeLine" }
 		extendedUnorientedGraph.remove(line)
 		getGrid().keySet().removeAll(linesKeys.remove(line) ?: emptySet())
 		changeSupport.firePropertyChange(
@@ -614,9 +630,11 @@ abstract class DefaultContext :
 	): Segment? {
 		// If track is not null, use it; otherwise use secondEndTrack
 		if (track != null) return getSegment(separator, track)
-		assert(separator != null)
-		assert(secondEndTrack != null) { separator }
-		assert(separator is OrientedPathSeparator) // Util
+		requireValidArgument(separator != null) { "PathSeparator cannot be null" }
+		requireValidArgument(secondEndTrack != null) { "secondEndTrack cannot be null for separator $separator" }
+		requireValidArgument(separator is OrientedPathSeparator) {
+			"PathSeparator must be OrientedPathSeparator, got ${separator.javaClass.simpleName}"
+		}
 		val segment = getSegment(separator, secondEndTrack!!)
 		// Match Java 1:1: return null when segment doesn't exist
 		return separator.getFollowingSegment(segment)
@@ -682,7 +700,9 @@ abstract class DefaultContext :
 		current: TrackBlock?
 	): Segment? {
 		if (current != null) {
-			assert(getGraph().get(location).contains(current)) { current }
+			requireValidState(getGraph().get(location).contains(current)) {
+				"Current track block $current not found in graph at location $location"
+			}
 		}
 		return if (current == null) null else getGraph().extensionalObject(location, current)
 	}
@@ -692,7 +712,7 @@ abstract class DefaultContext :
 	 */
 	private fun getLocation(node: NodeCell): Point {
 		val location = getRailWayNetGrid().getLocation(node)
-		assert(location != null) { this }
+		requireValidState(location != null) { "Location not found for nodeCell $node in grid" }
 		return location!!
 	}
 
@@ -724,7 +744,7 @@ abstract class DefaultContext :
 		var trackBlock: TrackBlock? = null
 		if (current != null) {
 			trackBlock = current.getTrackBlock()
-			assert(trackBlock != null)
+			requireValidState(trackBlock != null) { "TrackBlock cannot be null for current track section" }
 			val nextTrackSection = trackBlock?.getNextTrackSection(separator, current)
 			if (nextTrackSection != null) {
 				if (logger.isTraceEnabled()) {
@@ -785,7 +805,7 @@ abstract class DefaultContext :
 	 * Stop the simulation
 	 */
 	override fun stop() {
-		assert(mainProcess != null)
+		requireSimulationNotNull(mainProcess) { "Main process must be initialized before stopping simulation" }
 		for (worker in workers.values) {
 			worker.terminate()
 		}
@@ -819,12 +839,12 @@ abstract class DefaultContext :
 		next: Track?,
 		previous: Track?
 	): Boolean {
-		assert(separator != null)
+		requireSimulation(separator != null) { "Separator cannot be null in isSeparatorInDirection" }
 		val segment = getSegment(separator, next, previous)
 		if (segment == null && separator is InOut) return true
-		assert(segment != null) { separator }
+		requireSimulation(segment != null) { "Segment cannot be null for separator $separator" }
 		val direction = separator.direction()
-		assert(direction != null)
+		requireSimulation(direction != null) { "Direction cannot be null for oriented separator" }
 		val inDirection = segment === direction
 		if (logger.isDebugEnabled()) {
 			logger.debug(

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

@@ -9,6 +9,7 @@
  */
 package cz.vutbr.fit.interlockSim.context
 
+import cz.vutbr.fit.interlockSim.exceptions.requireValidState
 import cz.vutbr.fit.interlockSim.objects.cells.Cell
 import cz.vutbr.fit.interlockSim.objects.cells.TrackBlockPart
 import cz.vutbr.fit.interlockSim.util.Point
@@ -131,10 +132,14 @@ class DefaultRailWayNetGrid(
 	@Synchronized
 	fun containsKey(newPoint: Point): Boolean {
 		if (getCells().containsKey(newPoint)) {
-			assert(getReverseTable().containsValue(newPoint))
+			requireValidState(getReverseTable().containsValue(newPoint)) {
+				"Inconsistent grid state: point $newPoint in cells but not in reverse table"
+			}
 			return true
 		}
-		assert(!getReverseTable().containsValue(newPoint)) { newPoint }
+		requireValidState(!getReverseTable().containsValue(newPoint)) {
+			"Inconsistent grid state: point $newPoint in reverse table but not in cells: $newPoint"
+		}
 		return false
 	}
 
@@ -144,17 +149,21 @@ class DefaultRailWayNetGrid(
 	 */
 	@Synchronized
 	fun remove(key: Point) {
-		assert(key != null)
+		requireValidState(key != null) { "Key cannot be null" }
 		val removed: Cell? = getCells().remove(key)
 		val remove2: Point? = getReverseTable().remove(removed)
-		assert(key == remove2)
+		requireValidState(key == remove2) {
+			"Inconsistent grid state: expected key $key but got $remove2 from reverse table"
+		}
 	}
 
 	/**
 	 * @return true if grid is empty
 	 */
 	fun isEmpty(): Boolean {
-		assert(getReverseTable().isEmpty() == getCells().isEmpty())
+		requireValidState(getReverseTable().isEmpty() == getCells().isEmpty()) {
+			"Inconsistent grid state: reverse table and cells have different empty states"
+		}
 		return getCells().isEmpty()
 	}
 

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

@@ -13,6 +13,9 @@ 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.exceptions.requireEditorNotNull
+import cz.vutbr.fit.interlockSim.exceptions.requireValidState
 import cz.vutbr.fit.interlockSim.gui.gridcanvas.CellRenderer
 import cz.vutbr.fit.interlockSim.gui.gridcanvas.EditorCellRenderer
 import cz.vutbr.fit.interlockSim.gui.gridcanvas.GridCanvasEditingPopupMenu
@@ -75,7 +78,7 @@ class RailwayNetGridCanvas :
 				MouseEvent.BUTTON1 -> leftMouseClicked(e)
 				MouseEvent.BUTTON2 -> middleMouseClicked(e)
 				MouseEvent.BUTTON3 -> rightMouseClicked(e)
-				else -> assert(false) { "Unknown mouse button: ${e.button}" }
+				else -> error("Unknown mouse button: ${e.button}")
 			}
 		}
 
@@ -126,8 +129,7 @@ class RailwayNetGridCanvas :
 						// Clear selection after creating a cell to prevent auto-joining
 						selectedKey = null
 					} catch (e1: Exception) {
-						assert(false) { "Failed to create cell: $e1" }
-						e1.printStackTrace()
+						error("Failed to create cell: $e1")
 					}
 				}
 				selectedKey != null -> {
@@ -206,7 +208,7 @@ class RailwayNetGridCanvas :
 				state = State.SIMULATION
 				changeListeners(editListener, simulationControlListener)
 			}
-		 else -> assert(false) { "Unknown context type: ${newContext.javaClass}" }
+		 else -> error("Unknown context type: ${newContext.javaClass}")
 		}
 		changeContext(newContext)
 	}
@@ -232,7 +234,7 @@ class RailwayNetGridCanvas :
 
 	// Update context and recalculate display
 	private fun changeContext(cont: Context) {
-		assert(cont != null) { "Context cannot be null" }
+		requireEditorNotNull(cont) { "Context cannot be null" }
 		if (context != null) {
 			context!!.removePropertyChangeListener(this)
 		}
@@ -246,7 +248,7 @@ class RailwayNetGridCanvas :
 
 	// Painting methods
 	override fun paintComponent(g: Graphics) {
-		assert(g is Graphics2D) { "Graphics context must be Graphics2D" }
+		requireEditor(g is Graphics2D) { "Graphics context must be Graphics2D" }
 		paint(g as Graphics2D)
 	}
 
@@ -261,7 +263,7 @@ class RailwayNetGridCanvas :
 		for (entry in grid) {
 			val key = entry.key
 			val cell = entry.value
-			assert(key != null && cell != null) { "Grid entry has null key or value: ($key, $cell)" }
+			requireValidState(key != null && cell != null) { "Grid entry has null key or value: ($key, $cell)" }
 
 			val x = key.x * CELL_WIDTH
 			val y = key.y * CELL_HEIGHT

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

@@ -11,6 +11,7 @@ package cz.vutbr.fit.interlockSim.gui
 
 import cz.vutbr.fit.interlockSim.PROGRAM_NAME
 import cz.vutbr.fit.interlockSim.context.ContextChangeListener
+import cz.vutbr.fit.interlockSim.exceptions.requireValidState
 import java.awt.Component
 import java.awt.Dimension
 import java.awt.event.MouseEvent
@@ -32,7 +33,7 @@ class StatusBar :
 
 			override fun mouseMoved(e: MouseEvent) {
 				val source = e.source
-				assert(source is StatusProducer) { "Source must be a StatusProducer" }
+				requireValidState(source is StatusProducer) { "Source must be a StatusProducer" }
 				val status = (source as StatusProducer).getStatus(e)
 				if (status != null) {
 					text = status
@@ -46,7 +47,7 @@ class StatusBar :
 	}
 
 	private fun checkComponent(producer: StatusProducer): Component {
-		assert(producer is Component) { "StatusProducer must be a Component" }
+		requireValidState(producer is Component) { "StatusProducer must be a Component" }
 		return producer as Component
 	}
 

src/main/kotlin/cz/vutbr/fit/interlockSim/gui/action/NodeCellAction.kt

@@ -59,8 +59,7 @@ class NodeCellAction(
 				val f = getKoin().get<EditingContextFactory>()
 				cell = f.createNew(context, cellClass, *args) as Cell
 			} catch (e: Exception) {
-				assert(false) { e }
-				e.printStackTrace()
+				error("Failed to create cell icon: $e")
 			}
 			val img = BufferedImage(iconSize, iconSize, BufferedImage.TYPE_INT_RGB)
 			val g = img.createGraphics()

src/main/kotlin/cz/vutbr/fit/interlockSim/gui/gridcanvas/CellRenderer.kt

@@ -9,6 +9,7 @@
  */
 package cz.vutbr.fit.interlockSim.gui.gridcanvas
 
+import cz.vutbr.fit.interlockSim.exceptions.requireValidState
 import cz.vutbr.fit.interlockSim.objects.cells.Cell
 import cz.vutbr.fit.interlockSim.objects.cells.Cell.Segment
 import cz.vutbr.fit.interlockSim.objects.cells.InOut
@@ -94,7 +95,7 @@ abstract class CellRenderer(
 		cell: OrientedPathSeparator
 	) {
 		val thetaObj = ANGLES[cell.getSpatialType()]
-		assert(thetaObj != null) { "No angle defined for spatial type: ${cell.getSpatialType()}" }
+		requireValidState(thetaObj != null) { "No angle defined for spatial type: ${cell.getSpatialType()}" }
 
 		val theta = if (cell.getOrientation()) thetaObj!! + Math.PI else thetaObj!!
 		val xs = intArrayOf(cellWidth / 4, cellWidth / 4, 3 * cellWidth / 4)
@@ -112,14 +113,14 @@ abstract class CellRenderer(
 		g: Graphics2D,
 		cell: Cell
 	) {
-		assert(cell != null) { "Cell cannot be null" }
+		requireValidState(cell != null) { "Cell cannot be null" }
 
 		try {
 			// Use reflection to find and invoke the specific draw method for this cell type
 			val method = javaClass.getMethod("draw", Graphics2D::class.java, cell.javaClass)
 			method.invoke(this, g, cell)
 		} catch (e: Exception) {
-			assert(false) { "Failed to draw cell: $e" }
+			error("Failed to draw cell: $e")
 		}
 	}