From 37ffabc291f00ef0bba2b91446dc14205d7cd4b8 Mon Sep 17 00:00:00 2001
From: Zak Shearman <34372536+ZakShearman@users.noreply.github.com>
Date: Sun, 1 Oct 2023 15:39:55 +0100
Subject: [PATCH] Parse null lists as empty lists instead

---
 .../adapter/NullListToEmptyFactory.java       | 53 +++++++++++++++++++
 .../configs/common/ConfigItem.java            |  3 +-
 .../configs/gamemode/GameModeCollection.java  |  2 +
 3 files changed, 57 insertions(+), 1 deletion(-)
 create mode 100644 java/src/main/java/dev/emortal/api/liveconfigparser/adapter/NullListToEmptyFactory.java

diff --git a/java/src/main/java/dev/emortal/api/liveconfigparser/adapter/NullListToEmptyFactory.java b/java/src/main/java/dev/emortal/api/liveconfigparser/adapter/NullListToEmptyFactory.java
new file mode 100644
index 0000000..0548fac
--- /dev/null
+++ b/java/src/main/java/dev/emortal/api/liveconfigparser/adapter/NullListToEmptyFactory.java
@@ -0,0 +1,53 @@
+package dev.emortal.api.liveconfigparser.adapter;
+
+import com.google.gson.Gson;
+import com.google.gson.TypeAdapter;
+import com.google.gson.TypeAdapterFactory;
+import com.google.gson.reflect.TypeToken;
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonToken;
+import com.google.gson.stream.JsonWriter;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+
+public final class NullListToEmptyFactory implements TypeAdapterFactory {
+    public static final NullListToEmptyFactory INSTANCE = new NullListToEmptyFactory();
+
+    private NullListToEmptyFactory() {
+    }
+
+    @Override
+    public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
+        Class<?> rawType = type.getRawType();
+
+        // Only handle List and ArrayList; let other factories handle different types
+        if (rawType != List.class && rawType != ArrayList.class) {
+            return null;
+        }
+
+        // Delegate which handles deserialization of non-null values, and serialization
+        TypeAdapter<T> delegate = gson.getDelegateAdapter(this, type);
+        return new TypeAdapter<>() {
+            @Override
+            public void write(JsonWriter out, T value) throws IOException {
+                delegate.write(out, value);
+            }
+
+            @Override
+            public T read(JsonReader in) throws IOException {
+                if (in.peek() == JsonToken.NULL) {
+                    in.nextNull();
+
+                    // Safe due to check at beginning of `create` method
+                    @SuppressWarnings("unchecked")
+                    T t = (T) new ArrayList<>();
+                    return t;
+                } else {
+                    return delegate.read(in);
+                }
+            }
+        };
+    }
+}
diff --git a/java/src/main/java/dev/emortal/api/liveconfigparser/configs/common/ConfigItem.java b/java/src/main/java/dev/emortal/api/liveconfigparser/configs/common/ConfigItem.java
index 97cdbb3..566328f 100644
--- a/java/src/main/java/dev/emortal/api/liveconfigparser/configs/common/ConfigItem.java
+++ b/java/src/main/java/dev/emortal/api/liveconfigparser/configs/common/ConfigItem.java
@@ -1,7 +1,8 @@
 package dev.emortal.api.liveconfigparser.configs.common;
 
-import java.util.List;
 import org.jetbrains.annotations.NotNull;
 
+import java.util.List;
+
 public record ConfigItem(@NotNull String material, int slot, @NotNull String name, @NotNull List<String> lore) {
 }
diff --git a/java/src/main/java/dev/emortal/api/liveconfigparser/configs/gamemode/GameModeCollection.java b/java/src/main/java/dev/emortal/api/liveconfigparser/configs/gamemode/GameModeCollection.java
index e08c350..9e95ae2 100644
--- a/java/src/main/java/dev/emortal/api/liveconfigparser/configs/gamemode/GameModeCollection.java
+++ b/java/src/main/java/dev/emortal/api/liveconfigparser/configs/gamemode/GameModeCollection.java
@@ -3,6 +3,7 @@
 import com.google.gson.Gson;
 import com.google.gson.GsonBuilder;
 import dev.emortal.api.liveconfigparser.adapter.DurationAdapter;
+import dev.emortal.api.liveconfigparser.adapter.NullListToEmptyFactory;
 import dev.emortal.api.liveconfigparser.configs.ConfigCollection;
 import dev.emortal.api.liveconfigparser.parser.ConfigParser;
 import io.kubernetes.client.openapi.ApiClient;
@@ -41,6 +42,7 @@ private GameModeCollection(@NotNull Path localPath) throws IOException {
     private static final class Parser implements ConfigParser<GameModeConfig> {
         private static final Gson GSON = new GsonBuilder()
                 .registerTypeAdapter(Duration.class, new DurationAdapter().nullSafe())
+                .registerTypeAdapterFactory(NullListToEmptyFactory.INSTANCE)
                 .create();
 
         @Override