fix: tolerate duplicate flag keys in data sync payload

src/main/java/co/featbit/server/DataModel.java

@@ -13,6 +13,7 @@
 import java.util.Collections;
 import java.util.Date;
 import java.util.HashSet;
+import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -151,18 +152,20 @@ public Long getTimestamp() {
             return timestamp;
         }
 
+        // Duplicate keys (e.g. an archived copy of a re-created flag): the last entry wins.
         Map<DataStorageTypes.Category, Map<String, DataStorageTypes.Item>> toStorageType() {
-            ImmutableMap.Builder<String, DataStorageTypes.Item> flags = ImmutableMap.builder();
+            Map<String, DataStorageTypes.Item> flags = new LinkedHashMap<>();
             for (FeatureFlag flag : getFeatureFlags()) {
                 DataStorageTypes.Item item = flag.isArchived ? flag.toArchivedItem() : flag;
                 flags.put(item.getId(), item);
             }
-            ImmutableMap.Builder<String, DataStorageTypes.Item> segments = ImmutableMap.builder();
+            Map<String, DataStorageTypes.Item> segments = new LinkedHashMap<>();
             for (Segment segment : getSegments()) {
                 DataStorageTypes.Item item = segment.isArchived() ? segment.toArchivedItem() : segment;
                 segments.put(item.getId(), item);
             }
-            return ImmutableMap.of(DataStorageTypes.FEATURES, flags.build(), DataStorageTypes.SEGMENTS, segments.build());
+            return ImmutableMap.of(DataStorageTypes.FEATURES, ImmutableMap.copyOf(flags),
+                    DataStorageTypes.SEGMENTS, ImmutableMap.copyOf(segments));
         }
     }
 

src/test/java/co/featbit/server/DataModelTest.java

@@ -0,0 +1,82 @@
+package co.featbit.server;
+
+import co.featbit.commons.json.JsonHelper;
+import co.featbit.server.exterior.DataStorageTypes;
+import com.google.common.base.Charsets;
+import com.google.common.io.Resources;
+import com.google.gson.JsonArray;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParser;
+import org.junit.jupiter.api.Test;
+
+import java.util.Map;
+import java.util.UUID;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class DataModelTest {
+
+    @Test
+    void toStorageTypeKeepsLiveFlagWhenItFollowsArchivedCopyWithSameKey() throws Exception {
+        // featbit-agent order: archived copy first, re-created flag last
+        JsonObject envelope = envelope();
+        JsonArray flags = featureFlags(envelope);
+        JsonObject live = flags.get(0).getAsJsonObject();
+        flags.set(0, copyWithNewId(live, true));
+        flags.add(live);
+        String key = live.get("key").getAsString();
+
+        Map<String, DataStorageTypes.Item> items =
+                assertDoesNotThrow(data(envelope)::toStorageType).get(DataStorageTypes.FEATURES);
+
+        assertFalse(items.get(key).isArchived());
+    }
+
+    @Test
+    void toStorageTypeKeepsLastEntryWhenTwoArchivedCopiesHaveSameKey() throws Exception {
+        JsonObject envelope = envelope();
+        JsonArray flags = featureFlags(envelope);
+        JsonObject first = flags.get(0).getAsJsonObject();
+        first.addProperty("isArchived", true);
+        JsonObject last = copyWithNewId(first, true);
+        last.addProperty("updatedAt", "2030-01-01T00:00:00.000Z");
+        flags.add(last);
+        String key = first.get("key").getAsString();
+
+        DataModel.Data data = data(envelope);
+        long lastTimestamp = data.getFeatureFlags().get(flags.size() - 1).getTimestamp();
+        Map<String, DataStorageTypes.Item> items =
+                assertDoesNotThrow(data::toStorageType).get(DataStorageTypes.FEATURES);
+
+        assertTrue(items.get(key).isArchived());
+        assertEquals(lastTimestamp, items.get(key).getTimestamp().longValue());
+    }
+
+    @Test
+    void toStorageTypeKeepsFlagsWithDistinctKeys() throws Exception {
+        JsonObject envelope = envelope();
+        int count = featureFlags(envelope).size();
+
+        assertEquals(count, data(envelope).toStorageType().get(DataStorageTypes.FEATURES).size());
+    }
+
+    private static JsonObject copyWithNewId(JsonObject flag, boolean archived) {
+        JsonObject copy = flag.deepCopy();
+        copy.addProperty("id", UUID.randomUUID().toString());
+        copy.addProperty("isArchived", archived);
+        return copy;
+    }
+
+    private static JsonArray featureFlags(JsonObject envelope) {
+        return envelope.getAsJsonObject("data").getAsJsonArray("featureFlags");
+    }
+
+    private static DataModel.Data data(JsonObject envelope) {
+        return JsonHelper.deserialize(envelope.toString(), DataModel.All.class).data();
+    }
+
+    private static JsonObject envelope() throws Exception {
+        String json = Resources.toString(Resources.getResource("fbclient_test_data.json"), Charsets.UTF_8);
+        return JsonParser.parseString(json).getAsJsonObject();
+    }
+}