fix: Mixing flattened maps

lib/src/unflatten.dart

@@ -14,7 +14,12 @@ Map<String, dynamic> unflatten(
 
     for (int i = 0; i < keys.length; i++) {
       final k = keys[i];
-      if (i == keys.length - 1) {
+      if (value is Map) {
+        for (final entry in value.entries) {
+          current[k] ??= <String, dynamic>{};
+          current[k][entry.key] = entry.value;
+        }
+      } else if (i == keys.length - 1) {
         if (_isInteger(k)) {
           // This means that we have to do with a list instead
           (current as List).add(value);

test/flatten_test.dart

@@ -0,0 +1,165 @@
+import 'dart:convert';
+
+import 'package:flat/flat.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('Flatten', () {
+    test('Flattens nested Map', () {
+      const obj = {
+        "a": 1,
+        "b": {"c": 2}
+      };
+
+      const expected = {"a": 1, "b.c": 2};
+
+      final result = flatten(obj);
+
+      expect(result, expected);
+    });
+
+    test('Preserves empty Map', () {
+      const obj = {"a": {}};
+
+      const expected = {"a": {}};
+
+      final result = flatten(obj);
+
+      expect(result, expected);
+    });
+
+    test('Preserves null', () {
+      const obj = {"a": null};
+
+      const expected = {"a": null};
+
+      final result = flatten(obj);
+
+      expect(result, expected);
+    });
+
+    test('Preserves deep null', () {
+      const obj = {
+        "a": {"b": null}
+      };
+
+      const expected = {"a.b": null};
+
+      final result = flatten(obj);
+
+      expect(result, expected);
+    });
+
+    test('Flattens List', () {
+      const obj = {
+        "a": "item",
+        "b": [0, 1]
+      };
+
+      const expected = {"a": "item", "b.0": 0, "b.1": 1};
+
+      final result = flatten(obj);
+
+      expect(result, expected);
+    });
+
+    test('Flattens complex Map', () {
+      const obj = {
+        "a": 1,
+        "b": {
+          "c": 2,
+          "d": "asd",
+          "a": {
+            "a": [
+              {"where": "a"}
+            ]
+          }
+        }
+      };
+
+      const expected = {"a": 1, "b.c": 2, "b.d": "asd", "b.a.a.0.where": "a"};
+
+      final result = flatten(obj);
+
+      expect(result, expected);
+    });
+
+    test('Should delimit with optional delimiter parameter', () {
+      const obj = {
+        "a": 1,
+        "b": {"c": 2}
+      };
+
+      const expected = {"a": 1, "b_c": 2};
+
+      final result = flatten(obj, delimiter: "_");
+
+      expect(result, expected);
+    });
+
+    test('Should not flatten array when in safe mode', () {
+      const obj = {
+        "a": 1,
+        "b": {
+          "c": [
+            {"d": 2}
+          ]
+        }
+      };
+
+      const expected = {
+        "a": 1,
+        "b.c": [
+          {"d": 2}
+        ]
+      };
+
+      final result = flatten(obj, safe: true);
+
+      expect(result, expected);
+    });
+
+    test('Should limit depth by maxDepth', () {
+      const obj = {
+        "a": {
+          "b": {
+            "c": {
+              "d": {"e": 1}
+            }
+          }
+        }
+      };
+
+      const maxDepth = 3;
+
+      const expected = {
+        "a.b.c": {
+          "d": {"e": 1}
+        }
+      };
+
+      final result = flatten(obj, maxDepth: maxDepth);
+
+      expect(result, expected);
+    });
+
+    test('flattens decoded json with lists', () {
+      // https://github.com/danilofuchs/flat/pull/6
+      const obj = {
+        "mediaData": {
+          "resources": [
+            {"uri": "spotify://", "mimeType": "audio/unknown"}
+          ]
+        }
+      };
+
+      final result =
+          flatten(jsonDecode(jsonEncode(obj)) as Map<String, dynamic>);
+
+      expect(result, {
+        "mediaData.resources.0.uri": "spotify://",
+        "mediaData.resources.0.mimeType": "audio/unknown"
+      });
+    });
+  });
+}