content: /*
   * Copyright (C) 2017 The Android Open Source Project
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package com.android.setupwizardlib.items;
  
  import android.content.Context;
  import androidx.annotation.NonNull;
  import androidx.annotation.Nullable;
  import android.util.AttributeSet;
  import android.view.InflateException;
  import java.lang.reflect.Constructor;
  import java.util.HashMap;
  
  /**
   * An XML inflater that creates items by reading the tag as a class name, and constructs said class
   * by invoking the 2-argument constructor {@code Constructor(Context, AttributeSet)} via reflection.
   *
   * <p>Optionally a "default package" can be specified so that for unqualified tag names (i.e. names
   * that do not contain "."), the default package will be prefixed onto the tag.
   *
   * @param <T> The class where all instances (including child elements) belong to. If parent and
   *     child elements belong to different class hierarchies, it's OK to set this to {@link Object}.
   */
  public abstract class ReflectionInflater<T> extends SimpleInflater<T> {
  
    /* static section */
  
    private static final Class<?>[] CONSTRUCTOR_SIGNATURE =
        new Class<?>[] {Context.class, AttributeSet.class};
  
    private static final HashMap<String, Constructor<?>> constructorMap = new HashMap<>();
  
    /* non-static section */
  
    // Array used to contain the constructor arguments (Context, AttributeSet), to avoid allocating
    // a new array for creation of every item.
    private final Object[] tempConstructorArgs = new Object[2];
  
    @Nullable private String defaultPackage;
  
    @NonNull private final Context context;
  
    /**
     * Create a new inflater instance associated with a particular Context.
     *
     * @param context The context used to resolve resource IDs. This context is also passed to the
     *     constructor of the items created as the first argument.
     */
    protected ReflectionInflater(@NonNull Context context) {
      super(context.getResources());
      this.context = context;
    }
  
    @NonNull
    public Context getContext() {
      return context;
    }
  
    /**
     * Instantiate the class by name. This attempts to instantiate class of the given {@code name}
     * found in this inflater's ClassLoader.
     *
     * @param tagName The full name of the class to be instantiated.
     * @param attrs The XML attributes supplied for this instance.
     * @return The newly instantiated item.
     */
    @NonNull
    public final T createItem(String tagName, String prefix, AttributeSet attrs) {
      String qualifiedName = tagName;
      if (prefix != null && qualifiedName.indexOf('.') == -1) {
        qualifiedName = prefix.concat(qualifiedName);
      }
      @SuppressWarnings("unchecked") // qualifiedName should correspond to a subclass of T
      Constructor<? extends T> constructor =
          (Constructor<? extends T>) constructorMap.get(qualifiedName);
  
      try {
        if (constructor == null) {
          // Class not found in the cache, see if it's real, and try to add it
          @SuppressWarnings("unchecked") // qualifiedName should correspond to a subclass of T
          Class<? extends T> clazz =
              (Class<? extends T>) context.getClassLoader().loadClass(qualifiedName);
          constructor = clazz.getConstructor(CONSTRUCTOR_SIGNATURE);
          constructor.setAccessible(true);
          constructorMap.put(tagName, constructor);
        }
  
        tempConstructorArgs[0] = context;
        tempConstructorArgs[1] = attrs;
        final T item = constructor.newInstance(tempConstructorArgs);
        tempConstructorArgs[0] = null;
        tempConstructorArgs[1] = null;
        return item;
      } catch (Exception e) {
        throw new InflateException(
            attrs.getPositionDescription() + ": Error inflating class " + qualifiedName, e);
      }
    }
  
    @Override
    protected T onCreateItem(String tagName, AttributeSet attrs) {
      return createItem(tagName, defaultPackage, attrs);
    }
  
    /**
     * Sets the default package that will be searched for classes to construct for tag names that have
     * no explicit package.
     *
     * @param defaultPackage The default package. This will be prepended to the tag name, so it should
     *     end with a period.
     */
    public void setDefaultPackage(@Nullable String defaultPackage) {
      this.defaultPackage = defaultPackage;
    }
  
    /**
     * Returns the default package, or null if it is not set.
     *
     * @see #setDefaultPackage(String)
     * @return The default package.
     */
    @Nullable
    public String getDefaultPackage() {
      return defaultPackage;
    }
  }
  