/*
    * 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
    *
    *      https://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.internal.introspection;
  import java.lang.reflect.InvocationTargetException;
  
  import org.apache.commons.jexl3.JexlException;
  
  /**
   * Specialized executor to get a property from an object.
   * @since 2.0
   */
  public final class PropertyGetExecutor extends AbstractExecutor.Get {
      /** A static signature for method(). */
      private static final Object[] EMPTY_PARAMS = {};
      /**
       * Discovers a PropertyGetExecutor.
       * <p>The method to be found should be named "get{P,p}property.</p>
       *
       * @param is the introspector
       * @param clazz the class to find the get method from
       * @param property the property name to find
       * @return the executor if found, null otherwise
       */
      public static PropertyGetExecutor discover(final Introspector is, final Class<?> clazz, final String property) {
          final java.lang.reflect.Method method = discoverGet(is, "get", clazz, property);
          return method == null ? null : new PropertyGetExecutor(clazz, method, property);
      }
  
      /**
       * Base method for boolean and object property get.
       * @param is the introspector
       * @param which "is" or "get" for boolean or object
       * @param clazz The class being examined.
       * @param property The property being addressed.
       * @return The {get,is}{p,P}roperty method if one exists, null otherwise.
       */
      static java.lang.reflect.Method discoverGet(final Introspector is,
                                                  final String which,
                                                  final Class<?> clazz,
                                                  final String property) {
          if (property == null || property.isEmpty()) {
              return null;
          }
          //  this is gross and linear, but it keeps it straightforward.
          java.lang.reflect.Method method;
          final int start = which.length(); // "get" or "is" so 3 or 2 for char case switch
          // start with get<Property>
          final StringBuilder sb = new StringBuilder(which);
          sb.append(property);
          // uppercase nth char
          final char c = sb.charAt(start);
          sb.setCharAt(start, Character.toUpperCase(c));
          method = is.getMethod(clazz, sb.toString(), EMPTY_PARAMS);
          //lowercase nth char
          if (method == null) {
              sb.setCharAt(start, Character.toLowerCase(c));
              method = is.getMethod(clazz, sb.toString(), EMPTY_PARAMS);
          }
          return method;
      }
  
      /** The property. */
      private final String property;
  
      /**
       * Creates an instance.
       * @param clazz he class the get method applies to
       * @param method the method held by this executor
       * @param identifier the property to get
       */
      private PropertyGetExecutor(final Class<?> clazz, final java.lang.reflect.Method method, final String identifier) {
          super(clazz, method);
          property = identifier;
      }
  
      @Override
      public Object getTargetProperty() {
          return property;
      }
  
      @Override
      public Object invoke(final Object o) throws IllegalAccessException, InvocationTargetException {
          return method == null ? null : method.invoke(o, (Object[]) null);
      }
 
     @Override
     public Object tryInvoke(final Object o, final Object identifier) {
         if (o != null && method != null
             && property.equals(castString(identifier))
             && objectClass.equals(o.getClass())) {
             try {
                 return method.invoke(o, (Object[]) null);
             } catch (IllegalAccessException | IllegalArgumentException xill) {
                 return TRY_FAILED; // fail
             } catch (final InvocationTargetException xinvoke) {
                 throw JexlException.tryFailed(xinvoke); // throw
             }
         }
         return TRY_FAILED;
     }
 }