Simplify up BiMap/CharacterMap

core/src/commonMain/kotlin/de/haukesomm/sokoban/core/BiMap.kt

@@ -9,25 +9,31 @@ interface BiMap<K, V> : Map<K, V> {
 
     /**
      * The inverse of the [map].
-     *
-     * @throws IllegalStateException if the [map] is not bijective.
      */
     val inverse: BiMap<V, K>
 }
 
 /**
  * This class implements a [BiMap].
  *
- * The provided [map] _must be bijective_, meaning that every key must be mapped to exactly one value and vice versa.
- * Otherwise, an [IllegalStateException] will be thrown when trying to access the [inverse] map.
+ * The provided [map] _should not_ contain duplicate keys as they will get lost when the map's inverse is computed.
+ * In case a key is provided multiple times, the last one will be kept.
  */
-class BiMapImpl<K, V>(val map: Map<K, V>) : Map<K, V> by map, BiMap<K, V> {
+internal class BiMapImpl<K, V>(val map: Map<K, V>) : Map<K, V> by map, BiMap<K, V> {
 
     override val inverse: BiMap<V, K>
         get() = map.entries
             .associate { (k, v) -> v to k }
-            .let { inverse ->
-                if (inverse.size == map.size) BiMapImpl(inverse)
-                else throw IllegalStateException("Map is not bijective!")
-            }
-}
+            .let(::BiMapImpl)
+}
+
+/**
+ * Creates an _immutable_ [BiMap] from the given [entries].
+ *
+ * The provided [map] _should not_ contain duplicate keys as they will get lost when the map's inverse is computed.
+ * In case a key is provided multiple times, the last one will be kept.
+ */
+fun biMapOf(vararg entries: Pair<Char, TileProperties>): BiMap<Char, TileProperties> =
+    BiMapImpl(
+        mapOf(*entries)
+    )

core/src/commonMain/kotlin/de/haukesomm/sokoban/core/CharacterMap.kt

@@ -1,43 +1,25 @@
 package de.haukesomm.sokoban.core
 
-import de.haukesomm.sokoban.core.CharacterMap.Companion.default
-import kotlin.jvm.JvmInline
-import kotlin.jvm.JvmStatic
-
 /**
- * This class represents a character map.
+ * Convenience Type alias for Character maps
  *
  * A character map is a map that maps [Char]s to [TileProperties], which in turn contain the [TileType] and the
  * [EntityType] of the resulting [TileType] on the game board.
  *
- * All [CharacterMap]s should orient themselves on the default character map, which is defined in the companion object's
- * [default] property.
+ * All [CharacterMap]s should orient themselves on the default character map, which is defined in the globally
+ * available [DefaultCharacterMap].
  */
-class CharacterMap(map: BiMap<Char, TileProperties>) : BiMap<Char, TileProperties> by map {
-
-    companion object {
-
-        /**
-         * Default character map based on the original Sokoban game.
-         */
-        val default: CharacterMap = characterMapOf(
-            '_' to TileProperties(TileType.Empty),
-            '.' to TileProperties(TileType.Target),
-            '#' to TileProperties(TileType.Wall),
-            '$' to TileProperties(TileType.Empty, EntityType.Box),
-            '@' to TileProperties(TileType.Empty, EntityType.Player),
-            '*' to TileProperties(TileType.Target, EntityType.Box),
-            '+' to TileProperties(TileType.Target, EntityType.Player)
-        )
-    }
-}
+typealias CharacterMap = BiMap<Char, TileProperties>
 
 /**
- * Creates a [CharacterMap] from the given [entries].
+ * Default [CharacterMap] as used in the original Sokoban game.
  */
-fun characterMapOf(vararg entries: Pair<Char, TileProperties>): CharacterMap =
-    CharacterMap(
-        BiMapImpl(
-            mapOf(*entries)
-        )
-    )
+val DefaultCharacterMap: CharacterMap = biMapOf(
+    '_' to TileProperties(TileType.Empty),
+    '.' to TileProperties(TileType.Target),
+    '#' to TileProperties(TileType.Wall),
+    '$' to TileProperties(TileType.Empty, EntityType.Box),
+    '@' to TileProperties(TileType.Empty, EntityType.Player),
+    '*' to TileProperties(TileType.Target, EntityType.Box),
+    '+' to TileProperties(TileType.Target, EntityType.Player)
+)

core/src/commonMain/kotlin/de/haukesomm/sokoban/core/Level.kt

@@ -34,7 +34,7 @@ data class Level(
     val id: String,
     val name: String,
     val layoutString: String,
-    val characterMap: CharacterMap = CharacterMap.default
+    val characterMap: CharacterMap = DefaultCharacterMap
 ) {
     private val lines by lazy {
         layoutString.lines()