/*
    * 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.maven.model.interpolation.reflection;
  
  import java.lang.ref.Reference;
  import java.lang.ref.WeakReference;
  import java.lang.reflect.Array;
  import java.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;
  import java.util.Arrays;
  import java.util.List;
  import java.util.Map;
  import java.util.Optional;
  import java.util.WeakHashMap;
  
  import org.apache.maven.api.annotations.Nonnull;
  import org.apache.maven.api.annotations.Nullable;
  import org.apache.maven.model.interpolation.reflection.MethodMap.AmbiguousException;
  
  /**
   * Using simple dotted expressions to extract the values from an Object instance using JSP-like expressions
   * such as {@code project.build.sourceDirectory}.
   * <p>
   * In addition to usual getters using {@code getXxx} or {@code isXxx} suffixes, accessors
   * using {@code asXxx} or {@code toXxx} prefixes are also supported.
   */
  public class ReflectionValueExtractor {
      private static final Object[] OBJECT_ARGS = new Object[0];
  
      /**
       * Use a WeakHashMap here, so the keys (Class objects) can be garbage collected.
       * This approach prevents permgen space overflows due to retention of discarded
       * classloaders.
       */
      private static final Map<Class<?>, WeakReference<ClassMap>> CLASS_MAPS = new WeakHashMap<>();
  
      static final int EOF = -1;
  
      static final char PROPERTY_START = '.';
  
      static final char INDEXED_START = '[';
  
      static final char INDEXED_END = ']';
  
      static final char MAPPED_START = '(';
  
      static final char MAPPED_END = ')';
  
      static class Tokenizer {
          final String expression;
  
          int idx;
  
          Tokenizer(String expression) {
              this.expression = expression;
          }
  
          public int peekChar() {
              return idx < expression.length() ? expression.charAt(idx) : EOF;
          }
  
          public int skipChar() {
              return idx < expression.length() ? expression.charAt(idx++) : EOF;
          }
  
          public String nextToken(char delimiter) {
              int start = idx;
  
              while (idx < expression.length() && delimiter != expression.charAt(idx)) {
                  idx++;
              }
  
              // delimiter MUST be present
              if (idx <= start || idx >= expression.length()) {
                  return null;
              }
  
              return expression.substring(start, idx++);
          }
  
          public String nextPropertyName() {
              final int start = idx;
  
             while (idx < expression.length() && Character.isJavaIdentifierPart(expression.charAt(idx))) {
                 idx++;
             }
 
             // property name does not require delimiter
             if (idx <= start || idx > expression.length()) {
                 return null;
             }
 
             return expression.substring(start, idx);
         }
 
         public int getPosition() {
             return idx < expression.length() ? idx : EOF;
         }
 
         // to make tokenizer look pretty in debugger
         @Override
         public String toString() {
             return idx < expression.length() ? expression.substring(idx) : "<EOF>";
         }
     }
 
     private ReflectionValueExtractor() {}
 
     /**
      * <p>The implementation supports indexed, nested and mapped properties.</p>
      * <ul>
      * <li>nested properties should be defined by a dot, i.e. "user.address.street"</li>
      * <li>indexed properties (java.util.List or array instance) should be contains <code>(\\w+)\\[(\\d+)\\]</code>
      * pattern, i.e. "user.addresses[1].street"</li>
      * <li>mapped properties should be contains <code>(\\w+)\\((.+)\\)</code> pattern,
      *  i.e. "user.addresses(myAddress).street"</li>
      * </ul>
      *
      * @param expression not null expression
      * @param root       not null object
      * @return the object defined by the expression
      * @throws IntrospectionException if any
      */
     public static Object evaluate(@Nonnull String expression, @Nullable Object root) throws IntrospectionException {
         return evaluate(expression, root, true);
     }
 
     /**
      * <p>
      * The implementation supports indexed, nested and mapped properties.
      * </p>
      * <ul>
      * <li>nested properties should be defined by a dot, i.e. "user.address.street"</li>
      * <li>indexed properties (java.util.List or array instance) should be contains <code>(\\w+)\\[(\\d+)\\]</code>
      * pattern, i.e. "user.addresses[1].street"</li>
      * <li>mapped properties should be contains <code>(\\w+)\\((.+)\\)</code> pattern, i.e.
      * "user.addresses(myAddress).street"</li>
      * </ul>
      *
      * @param expression not null expression
      * @param root not null object
      * @param trimRootToken trim root token yes/no.
      * @return the object defined by the expression
      * @throws IntrospectionException if any
      */
     public static Object evaluate(@Nonnull String expression, @Nullable Object root, boolean trimRootToken)
             throws IntrospectionException {
         Object value = root;
 
         // ----------------------------------------------------------------------
         // Walk the dots and retrieve the ultimate value desired from the
         // MavenProject instance.
         // ----------------------------------------------------------------------
 
         if (expression == null || expression.isEmpty() || !Character.isJavaIdentifierStart(expression.charAt(0))) {
             return null;
         }
 
         boolean hasDots = expression.indexOf(PROPERTY_START) >= 0;
 
         final Tokenizer tokenizer;
         if (trimRootToken && hasDots) {
             tokenizer = new Tokenizer(expression);
             tokenizer.nextPropertyName();
             if (tokenizer.getPosition() == EOF) {
                 return null;
             }
         } else {
             tokenizer = new Tokenizer("." + expression);
         }
 
         int propertyPosition = tokenizer.getPosition();
         while (value != null && tokenizer.peekChar() != EOF) {
             switch (tokenizer.skipChar()) {
                 case INDEXED_START:
                     value = getIndexedValue(
                             expression,
                             propertyPosition,
                             tokenizer.getPosition(),
                             value,
                             tokenizer.nextToken(INDEXED_END));
                     break;
                 case MAPPED_START:
                     value = getMappedValue(
                             expression,
                             propertyPosition,
                             tokenizer.getPosition(),
                             value,
                             tokenizer.nextToken(MAPPED_END));
                     break;
                 case PROPERTY_START:
                     propertyPosition = tokenizer.getPosition();
                     value = getPropertyValue(value, tokenizer.nextPropertyName());
                     break;
                 default:
                     // could not parse expression
                     return null;
             }
         }
 
         if (value instanceof Optional) {
             value = ((Optional<?>) value).orElse(null);
         }
         return value;
     }
 
     private static Object getMappedValue(
             final String expression, final int from, final int to, final Object value, final String key)
             throws IntrospectionException {
         if (value == null || key == null) {
             return null;
         }
 
         if (value instanceof Map) {
             return ((Map) value).get(key);
         }
 
         final String message = String.format(
                 "The token '%s' at position '%d' refers to a java.util.Map, but the value "
                         + "seems is an instance of '%s'",
                 expression.subSequence(from, to), from, value.getClass());
 
         throw new IntrospectionException(message);
     }
 
     private static Object getIndexedValue(
             final String expression, final int from, final int to, final Object value, final String indexStr)
             throws IntrospectionException {
         try {
             int index = Integer.parseInt(indexStr);
 
             if (value.getClass().isArray()) {
                 return Array.get(value, index);
             }
 
             if (value instanceof List) {
                 return ((List) value).get(index);
             }
         } catch (NumberFormatException | IndexOutOfBoundsException e) {
             return null;
         }
 
         final String message = String.format(
                 "The token '%s' at position '%d' refers to a java.util.List or an array, but the value "
                         + "seems is an instance of '%s'",
                 expression.subSequence(from, to), from, value.getClass());
 
         throw new IntrospectionException(message);
     }
 
     private static Object getPropertyValue(Object value, String property) throws IntrospectionException {
         if (value == null || property == null || property.isEmpty()) {
             return null;
         }
 
         ClassMap classMap = getClassMap(value.getClass());
         String methodBase = Character.toTitleCase(property.charAt(0)) + property.substring(1);
         try {
             for (String prefix : Arrays.asList("get", "is", "to", "as")) {
                 Method method = classMap.findMethod(prefix + methodBase);
                 if (method != null) {
                     return method.invoke(value, OBJECT_ARGS);
                 }
             }
             return null;
         } catch (InvocationTargetException e) {
             throw new IntrospectionException(e.getTargetException());
         } catch (AmbiguousException | IllegalAccessException e) {
             throw new IntrospectionException(e);
         }
     }
 
     private static ClassMap getClassMap(Class<?> clazz) {
         Reference<ClassMap> ref = CLASS_MAPS.get(clazz);
         ClassMap classMap = ref != null ? ref.get() : null;
 
         if (classMap == null) {
             classMap = new ClassMap(clazz);
 
             CLASS_MAPS.put(clazz, new WeakReference<>(classMap));
         }
 
         return classMap;
     }
 }