/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You 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 org.apache.commons.jexl3.jexl342;
  
  import org.apache.commons.jexl3.JexlEngine;
  import org.apache.commons.jexl3.JexlException;
  import org.apache.commons.jexl3.JexlInfo;
  import org.apache.commons.jexl3.introspection.JexlMethod;
  import org.apache.commons.jexl3.introspection.JexlUberspect;
  
  /**
   * JexlMethod on a reference that pointed null.
   * <p>Performs a late discovery of the actual method.</p>
   */
  public class OptionalNullMethod implements JexlMethod {
      /** The Uberspect to discover the method. */
      private final JexlUberspect uberspect;
      /** The method we are trying to discover. */
      private final String methodName;
      /** The result when we solve it. */
      private JexlMethod delegate;
  
      OptionalNullMethod(final JexlUberspect jexlUberspect, final String name) {
          uberspect = jexlUberspect;
          methodName = name;
      }
  
      @Override
      public Class<?> getReturnType() {
          return delegate != null ? delegate.getReturnType() : null;
      }
  
      @Override
      public Object invoke(final Object obj, final Object... params) throws Exception {
          if (obj == null) {
              return null;
          }
          if (delegate == null) {
              delegate = uberspect.getMethod(obj, methodName, params);
              if (delegate == null) {
                  throw new JexlException.Method((JexlInfo) null, methodName, params);
              }
          }
          return delegate.invoke(obj, params);
      }
  
      @Override
      public boolean isCacheable() {
          return false;
      }
  
      @Override
      public boolean tryFailed(final Object rval) {
          return delegate != null ? delegate.tryFailed(rval) : JexlEngine.TRY_FAILED == rval;
      }
  
      @Override
      public Object tryInvoke(final String name, final Object obj, final Object... params) throws JexlException.TryFailed {
          if (obj == null) {
              return null;
          }
          return delegate != null ? delegate.tryInvoke(name, obj, params) : JexlEngine.TRY_FAILED;
      }
  }