1 files changed, 47 insertions, 0 deletions
diff --git a/core/src/main/scala/forge/util/MultiBiMap.scala b/core/src/main/scala/forge/util/MultiBiMap.scala
new file mode 100644
index 00000000..cb6ff280
--- /dev/null
+++ b/core/src/main/scala/forge/util/MultiBiMap.scala
@@ -0,0 +1,47 @@
+package forge.util
+
+import scala.collection.mutable
+
+/**
+  * A map from keys to collections of values: you can assign multiple values
+  * to any particular key. Also allows lookups in both directions: what values
+  * are assigned to a key or what key a value is assigned ti.
+  */
+trait MultiBiMap[K, V]{
+  def containsValue(v: V): Boolean
+  def lookupKey(k: K): OSet[V]
+  def lookupValue(v: V): K
+  def lookupValueOpt(v: V): Option[K]
+  def add(k: K, v: V): Unit
+  def removeAll(k: K): OSet[V]
+  def addAll(k: K, vs: TraversableOnce[V]): Unit
+  def keys(): Iterator[K]
+  def values(): Iterator[OSet[V]]
+}
+object MultiBiMap{
+  class Mutable[K, V]() extends MultiBiMap[K, V]{
+    private[this] val valueToKey = mutable.LinkedHashMap.empty[V, K]
+    private[this] val keyToValues = mutable.LinkedHashMap.empty[K, OSet.Mutable[V]]
+    def containsValue(v: V) = valueToKey.contains(v)
+    def lookupKey(k: K) = keyToValues(k)
+    def lookupValue(v: V) = valueToKey(v)
+    def lookupValueOpt(v: V) = valueToKey.get(v)
+    def add(k: K, v: V): Unit = {
+      valueToKey(v) = k
+      keyToValues.getOrElseUpdate(k, new OSet.Mutable[V]()).append(v)
+    }
+    def removeAll(k: K): OSet[V] = keyToValues.get(k) match {
+      case None => OSet()
+      case Some(vs) =>
+        vs.foreach(valueToKey.remove)
+
+        keyToValues.remove(k)
+        vs
+    }
+    def addAll(k: K, vs: TraversableOnce[V]): Unit = vs.foreach(this.add(k, _))
+
+    def keys() = keyToValues.keysIterator
+
+    def values() = keyToValues.valuesIterator
+  }
+}