content: /*
   *  This file is part of AndroidIDE.
   *
   *  AndroidIDE is free software: you can redistribute it and/or modify
   *  it under the terms of the GNU General Public License as published by
   *  the Free Software Foundation, either version 3 of the License, or
   *  (at your option) any later version.
   *
   *  AndroidIDE is distributed in the hope that it will be useful,
   *  but WITHOUT ANY WARRANTY; without even the implied warranty of
   *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   *  GNU General Public License for more details.
   *
   *  You should have received a copy of the GNU General Public License
   *   along with AndroidIDE.  If not, see <https://www.gnu.org/licenses/>.
   */
  
  package com.itsaky.androidide.tooling.api.util;
  
  import com.google.gson.Gson;
  import com.google.gson.JsonElement;
  import com.google.gson.JsonObject;
  import com.google.gson.JsonParseException;
  import com.google.gson.JsonPrimitive;
  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.JsonWriter;
  
  import java.io.IOException;
  import java.util.LinkedHashMap;
  import java.util.Map;
  
  /**
   * Adapts values whose runtime type may differ from their declaration type. This is necessary when a
   * field's type is not the same type that GSON should create when deserializing that field. For
   * example, consider these types:
   *
   * <pre>{@code
   * abstract class Shape {
   *   int x;
   *   int y;
   * }
   * class Circle extends Shape {
   *   int radius;
   * }
   * class Rectangle extends Shape {
   *   int width;
   *   int height;
   * }
   * class Diamond extends Shape {
   *   int width;
   *   int height;
   * }
   * class Drawing {
   *   Shape bottomShape;
   *   Shape topShape;
   * }
   * }</pre>
   *
   * <p>Without additional type information, the serialized JSON is ambiguous. Is the bottom shape in
   * this drawing a rectangle or a diamond?
   *
   * <pre>{@code
   * {
   *   "bottomShape": {
   *     "width": 10,
   *     "height": 5,
   *     "x": 0,
   *     "y": 0
   *   },
   *   "topShape": {
   *     "radius": 2,
   *     "x": 4,
   *     "y": 1
   *   }
   * }
   * }</pre>
   *
   * This class addresses this problem by adding type information to the serialized JSON and honoring
   * that type information when the JSON is deserialized:
   *
   * <pre>{@code
   * {
   *   "bottomShape": {
   *     "type": "Diamond",
   *     "width": 10,
   *     "height": 5,
   *     "x": 0,
   *     "y": 0
   *   },
   *   "topShape": {
   *     "type": "Circle",
   *     "radius": 2,
   *     "x": 4,
   *     "y": 1
   *   }
   * }
   * }</pre>
   *
   * Both the type field name ({@code "type"}) and the type labels ({@code "Rectangle"}) are
   * configurable.
   *
   * <h3>Registering Types</h3>
   *
   * Create a {@code RuntimeTypeAdapterFactory} by passing the base type and type field name to the
   * {@link #of} factory method. If you don't supply an explicit type field name, {@code "type"} will
   * be used.
   *
   * <pre>{@code
   * RuntimeTypeAdapterFactory<Shape> shapeAdapterFactory
   *     = RuntimeTypeAdapterFactory.of(Shape.class, "type");
   * }</pre>
   *
   * Next register all of your subtypes. Every subtype must be explicitly registered. This protects
   * your application from injection attacks. If you don't supply an explicit type label, the type's
   * simple name will be used.
   *
   * <pre>{@code
   * shapeAdapterFactory.registerSubtype(Rectangle.class, "Rectangle");
   * shapeAdapterFactory.registerSubtype(Circle.class, "Circle");
   * shapeAdapterFactory.registerSubtype(Diamond.class, "Diamond");
   * }</pre>
   *
   * Finally, register the type adapter factory in your application's GSON builder:
   *
   * <pre>{@code
   * Gson gson = new GsonBuilder()
   *     .registerTypeAdapterFactory(shapeAdapterFactory)
   *     .create();
   * }</pre>
   *
   * Like {@code GsonBuilder}, this API supports chaining:
   *
   * <pre>{@code
   * RuntimeTypeAdapterFactory<Shape> shapeAdapterFactory = RuntimeTypeAdapterFactory.of(Shape.class)
   *     .registerSubtype(Rectangle.class)
   *     .registerSubtype(Circle.class)
   *     .registerSubtype(Diamond.class);
   * }</pre>
   *
   * <h3>Serialization and deserialization</h3>
   *
   * In order to serialize and deserialize a polymorphic object, you must specify the base type
   * explicitly.
   *
   * <pre>{@code
   * Diamond diamond = new Diamond();
   * String json = gson.toJson(diamond, Shape.class);
   * }</pre>
   *
   * And then:
   *
   * <pre>{@code
   * Shape shape = gson.fromJson(json, Shape.class);
   * }</pre>
   */
  public final class RuntimeTypeAdapterFactory<T> implements TypeAdapterFactory {
    private final Class<?> baseType;
    private final String typeFieldName;
    private final Map<String, Class<?>> labelToSubtype = new LinkedHashMap<>();
    private final Map<Class<?>, String> subtypeToLabel = new LinkedHashMap<>();
    private final boolean maintainType;
  
    private RuntimeTypeAdapterFactory(Class<?> baseType, String typeFieldName, boolean maintainType) {
      if (typeFieldName == null || baseType == null) {
        throw new NullPointerException();
      }
      this.baseType = baseType;
      this.typeFieldName = typeFieldName;
      this.maintainType = maintainType;
    }
  
    /**
     * Creates a new runtime type adapter using for {@code baseType} using {@code typeFieldName} as
     * the type field name. Type field names are case sensitive. {@code maintainType} flag decide if
     * the type will be stored in pojo or not.
     */
    public static <T> RuntimeTypeAdapterFactory<T> of(
        Class<T> baseType, String typeFieldName, boolean maintainType) {
      return new RuntimeTypeAdapterFactory<>(baseType, typeFieldName, maintainType);
    }
  
    /**
     * Creates a new runtime type adapter using for {@code baseType} using {@code typeFieldName} as
     * the type field name. Type field names are case sensitive.
     */
    public static <T> RuntimeTypeAdapterFactory<T> of(Class<T> baseType, String typeFieldName) {
      return new RuntimeTypeAdapterFactory<>(baseType, typeFieldName, false);
    }
  
    /**
     * Creates a new runtime type adapter for {@code baseType} using {@code "type"} as the type field
     * name.
     */
    public static <T> RuntimeTypeAdapterFactory<T> of(Class<T> baseType) {
      return new RuntimeTypeAdapterFactory<>(baseType, "type", false);
    }
  
    /**
     * Registers {@code type} identified by its {@link Class#getSimpleName simple name}. Labels are
     * case sensitive.
     *
     * @throws IllegalArgumentException if either {@code type} or its simple name have already been
     *     registered on this type adapter.
     */
    public RuntimeTypeAdapterFactory<T> registerSubtype(Class<? extends T> type) {
      return registerSubtype(type, type.getSimpleName());
    }
  
    /**
     * Registers {@code type} identified by {@code label}. Labels are case sensitive.
     *
     * @throws IllegalArgumentException if either {@code type} or {@code label} have already been
     *     registered on this type adapter.
     */
    public RuntimeTypeAdapterFactory<T> registerSubtype(Class<? extends T> type, String label) {
      if (type == null || label == null) {
        throw new NullPointerException();
      }
      if (subtypeToLabel.containsKey(type) || labelToSubtype.containsKey(label)) {
        throw new IllegalArgumentException("types and labels must be unique");
      }
      labelToSubtype.put(label, type);
      subtypeToLabel.put(type, label);
      return this;
    }
  
    @Override
    public <R> TypeAdapter<R> create(Gson gson, TypeToken<R> type) {
      if (type.getRawType() != baseType) {
        return null;
      }
  
      final TypeAdapter<JsonElement> jsonElementAdapter = gson.getAdapter(JsonElement.class);
      final Map<String, TypeAdapter<?>> labelToDelegate = new LinkedHashMap<>();
      final Map<Class<?>, TypeAdapter<?>> subtypeToDelegate = new LinkedHashMap<>();
      for (Map.Entry<String, Class<?>> entry : labelToSubtype.entrySet()) {
        TypeAdapter<?> delegate = gson.getDelegateAdapter(this, TypeToken.get(entry.getValue()));
        labelToDelegate.put(entry.getKey(), delegate);
        subtypeToDelegate.put(entry.getValue(), delegate);
      }
  
      return new TypeAdapter<R>() {
        @Override
        public void write(JsonWriter out, R value) throws IOException {
          Class<?> srcType = value.getClass();
          String label = subtypeToLabel.get(srcType);
          @SuppressWarnings("unchecked") // registration requires that subtype extends T
          TypeAdapter<R> delegate = (TypeAdapter<R>) subtypeToDelegate.get(srcType);
          if (delegate == null) {
            throw new JsonParseException(
                "cannot serialize " + srcType.getName() + "; did you forget to register a subtype?");
          }
          JsonObject jsonObject = delegate.toJsonTree(value).getAsJsonObject();
  
          if (maintainType) {
            jsonElementAdapter.write(out, jsonObject);
            return;
          }
  
          JsonObject clone = new JsonObject();
  
          if (jsonObject.has(typeFieldName)) {
            throw new JsonParseException(
                "cannot serialize "
                    + srcType.getName()
                    + " because it already defines a field named "
                    + typeFieldName);
          }
          clone.add(typeFieldName, new JsonPrimitive(label));
  
          for (Map.Entry<String, JsonElement> e : jsonObject.entrySet()) {
            clone.add(e.getKey(), e.getValue());
          }
          jsonElementAdapter.write(out, clone);
        }
  
        @Override
        public R read(JsonReader in) throws IOException {
          JsonElement jsonElement = jsonElementAdapter.read(in);
          JsonElement labelJsonElement;
          if (maintainType) {
            labelJsonElement = jsonElement.getAsJsonObject().get(typeFieldName);
          } else {
            labelJsonElement = jsonElement.getAsJsonObject().remove(typeFieldName);
          }
  
          if (labelJsonElement == null) {
            throw new JsonParseException(
                "cannot deserialize "
                    + baseType
                    + " because it does not define a field named "
                    + typeFieldName);
          }
          String label = labelJsonElement.getAsString();
          @SuppressWarnings("unchecked") // registration requires that subtype extends T
          TypeAdapter<R> delegate = (TypeAdapter<R>) labelToDelegate.get(label);
          if (delegate == null) {
            throw new JsonParseException(
                "cannot deserialize "
                    + baseType
                    + " subtype named "
                    + label
                    + "; did you forget to register a subtype?");
          }
          return delegate.fromJsonTree(jsonElement);
        }
      }.nullSafe();
    }
  }
  