Support modded enums in gson using custom EnumTypeAdapter. Resolves carbon breaking materials in issue #90.

src/main/java/com/massivecraft/factions/util/EnumTypeAdapter.java

@@ -0,0 +1,66 @@
+package com.massivecraft.factions.util;
+
+import org.bukkit.craftbukkit.libs.com.google.gson.Gson;
+import org.bukkit.craftbukkit.libs.com.google.gson.TypeAdapter;
+import org.bukkit.craftbukkit.libs.com.google.gson.TypeAdapterFactory;
+import org.bukkit.craftbukkit.libs.com.google.gson.annotations.SerializedName;
+import org.bukkit.craftbukkit.libs.com.google.gson.reflect.TypeToken;
+import org.bukkit.craftbukkit.libs.com.google.gson.stream.JsonReader;
+import org.bukkit.craftbukkit.libs.com.google.gson.stream.JsonToken;
+import org.bukkit.craftbukkit.libs.com.google.gson.stream.JsonWriter;
+
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.Map;
+
+public final class EnumTypeAdapter<T extends Enum<T>> extends TypeAdapter<T> {
+
+    private final Map<String, T> nameToConstant = new HashMap<String, T>();
+    private final Map<T, String> constantToName = new HashMap<T, String>();
+
+    public EnumTypeAdapter(Class<T> classOfT) {
+        try {
+            for (T constant : classOfT.getEnumConstants()) {
+                String name = constant.name();
+                SerializedName annotation = classOfT.getField(name).getAnnotation(SerializedName.class);
+                if (annotation != null) {
+                    name = annotation.value();
+                }
+                nameToConstant.put(name, constant);
+                constantToName.put(constant, name);
+            }
+        } catch (NoSuchFieldException e) {
+            // ignore since it could be a modified enum
+        }
+    }
+    public T read(JsonReader in) throws IOException {
+        if (in.peek() == JsonToken.NULL) {
+            in.nextNull();
+            return null;
+        }
+        return nameToConstant.get(in.nextString());
+    }
+
+    public void write(JsonWriter out, T value) throws IOException {
+        out.value(value == null ? null : constantToName.get(value));
+    }
+
+    public static final TypeAdapterFactory ENUM_FACTORY = newEnumTypeHierarchyFactory();
+
+    public static <TT> TypeAdapterFactory newEnumTypeHierarchyFactory() {
+        return new TypeAdapterFactory() {
+            @SuppressWarnings({"rawtypes", "unchecked"})
+            public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> typeToken) {
+                Class<? super T> rawType = typeToken.getRawType();
+                if (!Enum.class.isAssignableFrom(rawType) || rawType == Enum.class) {
+                    return null;
+                }
+                if (!rawType.isEnum()) {
+                    rawType = rawType.getSuperclass(); // handle anonymous subclasses
+                }
+                return (TypeAdapter<T>) new EnumTypeAdapter(rawType);
+            }
+        };
+    }
+
+}