From 6d6510c22372a048030e81082116f92bf80218a7 Mon Sep 17 00:00:00 2001
From: Darin Kelkhoff <darin.kelkhoff@gmail.com>
Date: Thu, 13 Jul 2023 17:09:18 -0500
Subject: [PATCH] Add swapMultiLevelMapKeys

---
 .../backend/core/utils/CollectionUtils.java   | 36 +++++++++++++++++++
 .../core/utils/CollectionUtilsTest.java       | 23 ++++++++++++
 2 files changed, 59 insertions(+)

diff --git a/qqq-backend-core/src/main/java/com/kingsrook/qqq/backend/core/utils/CollectionUtils.java b/qqq-backend-core/src/main/java/com/kingsrook/qqq/backend/core/utils/CollectionUtils.java
index f817b6b3..ecb5aca5 100755
--- a/qqq-backend-core/src/main/java/com/kingsrook/qqq/backend/core/utils/CollectionUtils.java
+++ b/qqq-backend-core/src/main/java/com/kingsrook/qqq/backend/core/utils/CollectionUtils.java
@@ -627,4 +627,40 @@ public class CollectionUtils
       }
    }
 
+
+
+   /*******************************************************************************
+    ** Take a multi-level map, e.g., Map{String, Map{Integer, BigDecimal}}
+    ** and invert it - e.g., to Map{Integer, Map{String, BigDecimal}}
+    *******************************************************************************/
+   public static <K1, K2, V> Map<K2, Map<K1, V>> swapMultiLevelMapKeys(Map<K1, Map<K2, V>> input)
+   {
+      if(input == null)
+      {
+         return (null);
+      }
+
+      Map<K2, Map<K1, V>> output = new HashMap<>();
+
+      for(Map.Entry<K1, Map<K2, V>> entry : input.entrySet())
+      {
+         K1         key1 = entry.getKey();
+         Map<K2, V> map1 = entry.getValue();
+
+         if(map1 != null)
+         {
+            for(Map.Entry<K2, V> entry2 : map1.entrySet())
+            {
+               K2 key2  = entry2.getKey();
+               V  value = entry2.getValue();
+
+               output.computeIfAbsent(key2, (k) -> new HashMap<>());
+               output.get(key2).put(key1, value);
+            }
+         }
+      }
+
+      return (output);
+   }
+
 }
diff --git a/qqq-backend-core/src/test/java/com/kingsrook/qqq/backend/core/utils/CollectionUtilsTest.java b/qqq-backend-core/src/test/java/com/kingsrook/qqq/backend/core/utils/CollectionUtilsTest.java
index 80425535..62c0573e 100644
--- a/qqq-backend-core/src/test/java/com/kingsrook/qqq/backend/core/utils/CollectionUtilsTest.java
+++ b/qqq-backend-core/src/test/java/com/kingsrook/qqq/backend/core/utils/CollectionUtilsTest.java
@@ -34,6 +34,7 @@ import java.util.TreeMap;
 import java.util.function.Function;
 import com.google.gson.reflect.TypeToken;
 import com.kingsrook.qqq.backend.core.BaseTest;
+import com.kingsrook.qqq.backend.core.utils.collections.MapBuilder;
 import org.junit.jupiter.api.Test;
 import static org.junit.jupiter.api.Assertions.assertArrayEquals;
 import static org.junit.jupiter.api.Assertions.assertEquals;
@@ -594,4 +595,26 @@ class CollectionUtilsTest extends BaseTest
 
    }
 
+
+
+   /*******************************************************************************
+    **
+    *******************************************************************************/
+   @Test
+   void testSwapMultiLevelMapKeys()
+   {
+      Map<String, Map<Integer, String>> input = MapBuilder.of(
+         "A", Map.of(1, "A1", 2, "A2", 3, "A3"),
+         "B", Map.of(1, "B1", 4, "B4"),
+         "C", null);
+
+      Map<Integer, Map<String, String>> output = CollectionUtils.swapMultiLevelMapKeys(input);
+
+      assertEquals(MapBuilder.of(
+         1, Map.of("A", "A1", "B", "B1"),
+         2, Map.of("A", "A2"),
+         3, Map.of("A", "A3"),
+         4, Map.of("B", "B4")), output);
+   }
+
 }