Add timer

domain/src/commonMain/kotlin/ch/dissem/yaep/domain/Game.kt

@@ -7,6 +7,9 @@ class Game(
     val horizontalClues = clues.filterIsInstance<HorizontalClue>()
     val verticalClues = clues.filterIsInstance<SameColumnClue<ItemClass<*>, ItemClass<*>>>()
 
+    private val onStartListeners = mutableListOf<() -> Unit>()
+    private val onSolvedListeners = mutableListOf<() -> Unit>()
+
     init {
         for (position in clues.filterIsInstance<PositionClue<ItemClass<*>>>()) {
             val row = grid[position.item.itemType.companion]
@@ -18,6 +21,29 @@ class Game(
                 }
             }
         }
+        grid.forEach { row ->
+            row.forEach { cell ->
+                cell.optionsRemovedListeners.add {
+                    if (onStartListeners.isNotEmpty()) {
+                        onStartListeners.forEach { it() }
+                        onStartListeners.clear()
+                    }
+                }
+            }
+            row.onSolved {
+                if (onSolvedListeners.isNotEmpty() && isSolved) {
+                    onSolvedListeners.forEach { it() }
+                }
+            }
+        }
+    }
+
+    fun onStart(listener: () -> Unit) {
+        onStartListeners.add(listener)
+    }
+
+    fun onSolved(listener: () -> Unit) {
+        onSolvedListeners.add(listener)
     }
 
     /**

domain/src/commonMain/kotlin/ch/dissem/yaep/domain/GameRow.kt

@@ -6,13 +6,22 @@ class GameRow<C : ItemClass<C>>(
     val cells: List<GameCell<C>>
 ) : List<GameCell<C>> by cells {
     var isSolved = false
-        private set
+        private set(value) {
+            field = value
+            if (value) {
+                onSolvedListener()
+            }
+        }
+    var onSolvedListener = {}
+
+    fun onSolved(listener: () -> Unit) {
+        onSolvedListener = listener
+    }
 
     fun indexOf(element: C) = indexOfFirst { it.selection?.itemType == element }
 
     fun cleanupOptions() {
-        if (
-            isSolved && all {
+        if (isSolved && all {
                 it.solution != null
                         && it.options.size == 1
                         && it.options.single() == it.selection