/*
    * 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.internal.introspection;
  
  import java.lang.ref.Reference;
  import java.lang.ref.SoftReference;
  import java.lang.reflect.Field;
  import java.lang.reflect.Method;
  import java.util.Collections;
  import java.util.EnumSet;
  import java.util.Enumeration;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.atomic.AtomicInteger;
  
  import org.apache.commons.jexl3.JexlArithmetic;
  import org.apache.commons.jexl3.JexlEngine;
  import org.apache.commons.jexl3.JexlOperator;
  import org.apache.commons.jexl3.internal.Operator;
  import org.apache.commons.jexl3.introspection.JexlMethod;
  import org.apache.commons.jexl3.introspection.JexlPermissions;
  import org.apache.commons.jexl3.introspection.JexlPropertyGet;
  import org.apache.commons.jexl3.introspection.JexlPropertySet;
  import org.apache.commons.jexl3.introspection.JexlUberspect;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  /**
   * Implements Uberspect to provide the default introspective
   * functionality of JEXL.
   * <p>
   * This is the class to derive to customize introspection.</p>
   *
   * @since 1.0
   */
  public class Uberspect implements JexlUberspect {
      /** Publicly exposed special failure object returned by tryInvoke. */
      public static final Object TRY_FAILED = JexlEngine.TRY_FAILED;
      /** The logger to use for all warnings and errors. */
      protected final Log logger;
      /** The resolver strategy. */
      private final JexlUberspect.ResolverStrategy strategy;
      /** The permissions. */
      private final JexlPermissions permissions;
      /** The introspector version. */
      private final AtomicInteger version;
      /** The soft reference to the introspector currently in use. */
      private volatile Reference<Introspector> ref;
      /** The class loader reference; used to recreate the introspector when necessary. */
      private volatile Reference<ClassLoader> loader;
      /**
       * The map from arithmetic classes to overloaded operator sets.
       * <p>
       * This map keeps track of which operator methods are overloaded per JexlArithmetic classes
       * allowing a fail fast test during interpretation by avoiding seeking a method when there is none.
       */
      private final Map<Class<? extends JexlArithmetic>, Set<JexlOperator>> operatorMap;
  
      /**
       * Creates a new Uberspect.
       * @param runtimeLogger the logger used for all logging needs
       * @param sty the resolver strategy
       */
      public Uberspect(final Log runtimeLogger, final JexlUberspect.ResolverStrategy sty) {
          this(runtimeLogger, sty, null);
      }
  
      /**
       * Creates a new Uberspect.
       * @param runtimeLogger the logger used for all logging needs
       * @param sty the resolver strategy
       * @param perms the introspector permissions
       */
      public Uberspect(final Log runtimeLogger, final JexlUberspect.ResolverStrategy sty, final JexlPermissions perms) {
          logger = runtimeLogger == null ? LogFactory.getLog(JexlEngine.class) : runtimeLogger;
          strategy = sty == null ? JexlUberspect.JEXL_STRATEGY : sty;
          permissions = perms == null ? JexlPermissions.RESTRICTED : perms;
          ref = new SoftReference<>(null);
          loader = new SoftReference<>(getClass().getClassLoader());
          operatorMap = new ConcurrentHashMap<>();
          version = new AtomicInteger();
      }
 
     /**
      * Gets the current introspector base.
      * <p>
      * If the reference has been collected, this method will recreate the underlying introspector.</p>
      * @return the introspector
      */
     protected final Introspector base() {
         Introspector intro = ref.get();
         if (intro == null) {
             // double-checked locking is ok (fixed by Java 5 memory model).
             synchronized (this) {
                 intro = ref.get();
                 if (intro == null) {
                     intro = new Introspector(logger, loader.get(), permissions);
                     ref = new SoftReference<>(intro);
                     loader = new SoftReference<>(intro.getLoader());
                     version.incrementAndGet();
                 }
             }
         }
         return intro;
     }
 
     /**
      * Computes which operators have an overload implemented in the arithmetic.
      * <p>This is used to speed up resolution and avoid introspection when possible.</p>
      * @param arithmetic the arithmetic instance
      * @return the set of overloaded operators
      */
     Set<JexlOperator> getOverloads(final JexlArithmetic arithmetic) {
         final Class<? extends JexlArithmetic> aclass = arithmetic.getClass();
         return operatorMap.computeIfAbsent(aclass, k -> {
             final Set<JexlOperator> newOps = EnumSet.noneOf(JexlOperator.class);
             // deal only with derived classes
             if (!JexlArithmetic.class.equals(aclass)) {
                 for (final JexlOperator op : JexlOperator.values()) {
                     final Method[] methods = getMethods(arithmetic.getClass(), op.getMethodName());
                     if (methods != null) {
                         for (final Method method : methods) {
                             final Class<?>[] parms = method.getParameterTypes();
                             if (parms.length != op.getArity()) {
                                 continue;
                             }
                             // filter method that is an actual overload:
                             // - not inherited (not declared by base class)
                             // - nor overridden (not present in base class)
                             if (!JexlArithmetic.class.equals(method.getDeclaringClass())) {
                                 try {
                                     JexlArithmetic.class.getMethod(method.getName(), method.getParameterTypes());
                                 } catch (final NoSuchMethodException xmethod) {
                                     // method was not found in JexlArithmetic; this is an operator definition
                                     newOps.add(op);
                                 }
                             }
                         }
                     }
                 }
             }
             return newOps;
         });
     }
 
     @Override
     public JexlArithmetic.Uberspect getArithmetic(final JexlArithmetic arithmetic) {
         final Set<JexlOperator> operators = arithmetic == null ? Collections.emptySet() : getOverloads(arithmetic);
         return operators.isEmpty()? null : new Operator(this, arithmetic, operators);
     }
 
     @Override
     public Operator getOperator(final JexlArithmetic arithmetic) {
         final Set<JexlOperator> operators = arithmetic == null ? Collections.emptySet() : getOverloads(arithmetic);
         return new Operator(this, arithmetic, operators);
     }
 
     /**
      * Gets a class by name through this introspector class loader.
      * @param className the class name
      * @return the class instance or null if it could not be found
      */
     @Override
     public final Class<?> getClassByName(final String className) {
         return base().getClassByName(className);
     }
 
     @Override
     public ClassLoader getClassLoader() {
         synchronized (this) {
             return loader.get();
         }
     }
 
     @Override
     public JexlMethod getConstructor(final Object ctorHandle, final Object... args) {
         return ConstructorMethod.discover(base(), ctorHandle, args);
     }
 
     /**
      * Gets the field named by
      * {@code key} for the class
      * {@code c}.
      *
      * @param c   Class in which the field search is taking place
      * @param key Name of the field being searched for
      * @return a {@link java.lang.reflect.Field} or null if it does not exist or is not accessible
      */
     public final Field getField(final Class<?> c, final String key) {
         return base().getField(c, key);
     }
 
     /**
      * Gets the accessible field names known for a given class.
      * @param c the class
      * @return the class field names
      */
     public final String[] getFieldNames(final Class<?> c) {
         return base().getFieldNames(c);
     }
 
     @Override
     @SuppressWarnings("unchecked")
     public Iterator<?> getIterator(final Object obj) {
         if (!permissions.allow(obj.getClass())) {
             return null;
         }
         if (obj instanceof Iterator<?>) {
             return (Iterator<?>) obj;
         }
         if (obj.getClass().isArray()) {
             return new ArrayIterator(obj);
         }
         if (obj instanceof Map<?, ?>) {
             return ((Map<?, ?>) obj).values().iterator();
         }
         if (obj instanceof Enumeration<?>) {
             return new EnumerationIterator<>((Enumeration<Object>) obj);
         }
         if (obj instanceof Iterable<?>) {
             return ((Iterable<?>) obj).iterator();
         }
         try {
             // look for an iterator() method to support the JDK5 Iterable
             // interface or any user tools/DTOs that want to work in
             // foreach without implementing the Collection interface
             final JexlMethod it = getMethod(obj, "iterator", (Object[]) null);
             if (it != null && Iterator.class.isAssignableFrom(it.getReturnType())) {
                 return (Iterator<Object>) it.invoke(obj, (Object[]) null);
             }
         } catch (final Exception xany) {
             if (logger != null && logger.isDebugEnabled()) {
                 logger.info("unable to solve iterator()", xany);
             }
         }
         return null;
     }
 
     /**
      * Gets the method defined by
      * {@code key} and for the Class
      * {@code c}.
      *
      * @param c   Class in which the method search is taking place
      * @param key MethodKey of the method being searched for
      * @return a {@link java.lang.reflect.Method}
      *         or null if no unambiguous method could be found through introspection.
      */
     public final Method getMethod(final Class<?> c, final MethodKey key) {
         return base().getMethod(c, key);
     }
 
     /**
      * Gets the method defined by
      * {@code name} and
      * {@code params} for the Class
      * {@code c}.
      *
      * @param c      Class in which the method search is taking place
      * @param name   Name of the method being searched for
      * @param params An array of Objects (not Classes) that describe the parameters
      * @return a {@link java.lang.reflect.Method}
      *         or null if no unambiguous method could be found through introspection.
      */
     public final Method getMethod(final Class<?> c, final String name, final Object[] params) {
         return base().getMethod(c, new MethodKey(name, params));
     }
 
     @Override
     public JexlMethod getMethod(final Object obj, final String method, final Object... args) {
         return MethodExecutor.discover(base(), obj, method, args);
     }
 
     /**
      * Gets the accessible methods names known for a given class.
      * @param c the class
      * @return the class method names
      */
     public final String[] getMethodNames(final Class<?> c) {
         return base().getMethodNames(c);
     }
 
     /**
      * Gets all the methods with a given name from this map.
      * @param c          the class
      * @param methodName the seeked methods name
      * @return the array of methods
      */
     public final Method[] getMethods(final Class<?> c, final String methodName) {
         return base().getMethods(c, methodName);
     }
 
     @Override
     public JexlPropertyGet getPropertyGet(
             final List<PropertyResolver> resolvers, final Object obj, final Object identifier
     ) {
         final Class<?> clazz = obj.getClass();
         final String property = AbstractExecutor.castString(identifier);
         final Introspector is = base();
         final List<PropertyResolver> r = resolvers == null ? strategy.apply(null, obj) : resolvers;
         JexlPropertyGet executor = null;
         for (final PropertyResolver resolver : r) {
             if (resolver instanceof JexlResolver) {
                 switch ((JexlResolver) resolver) {
                     case PROPERTY:
                         // first try for a getFoo() type of property (also getfoo() )
                         executor = PropertyGetExecutor.discover(is, clazz, property);
                         if (executor == null) {
                             executor = BooleanGetExecutor.discover(is, clazz, property);
                         }
                         break;
                     case MAP:
                         // let's see if we are a map...
                         executor = MapGetExecutor.discover(is, clazz, identifier);
                         break;
                     case LIST:
                         // let's see if this is a list or array
                         final Integer index = AbstractExecutor.castInteger(identifier);
                         if (index != null) {
                             executor = ListGetExecutor.discover(is, clazz, index);
                         }
                         break;
                     case DUCK:
                         // if that didn't work, look for get(foo)
                         executor = DuckGetExecutor.discover(is, clazz, identifier);
                         if (executor == null && property != null && property != identifier) {
                             // look for get("foo") if we did not try yet (just above)
                             executor = DuckGetExecutor.discover(is, clazz, property);
                         }
                         break;
                     case FIELD:
                         // a field may be? (cannot be a number)
                         executor = FieldGetExecutor.discover(is, clazz, property);
                         // static class fields (enums included)
                         if (obj instanceof Class<?>) {
                             executor = FieldGetExecutor.discover(is, (Class<?>) obj, property);
                         }
                         break;
                     case CONTAINER:
                         // or an indexed property?
                         executor = IndexedType.discover(is, obj, property);
                         break;
                     default:
                         continue; // in case we add new ones in enum
                 }
             } else {
                 executor = resolver.getPropertyGet(this, obj, identifier);
             }
             if (executor != null) {
                 return executor;
             }
         }
         return null;
     }
 
     @Override
     public JexlPropertyGet getPropertyGet(final Object obj, final Object identifier) {
         return getPropertyGet(null, obj, identifier);
     }
 
     @Override
     public JexlPropertySet getPropertySet(
             final List<PropertyResolver> resolvers, final Object obj, final Object identifier, final Object arg
     ) {
         final Class<?> clazz = obj.getClass();
         final String property = AbstractExecutor.castString(identifier);
         final Introspector is = base();
         final List<PropertyResolver> actual = resolvers == null ? strategy.apply(null, obj) : resolvers;
         JexlPropertySet executor = null;
         for (final PropertyResolver resolver : actual) {
             if (resolver instanceof JexlResolver) {
                 switch ((JexlResolver) resolver) {
                     case PROPERTY:
                         // first try for a setFoo() type of property (also setfoo() )
                         executor = PropertySetExecutor.discover(is, clazz, property, arg);
                         break;
                     case MAP:
                         // let's see if we are a map...
                         executor = MapSetExecutor.discover(is, clazz, identifier, arg);
                         break;
                     case LIST:
                         // let's see if we can convert the identifier to an int,
                         // if obj is an array or a list, we can still do something
                         final Integer index = AbstractExecutor.castInteger(identifier);
                         if (index != null) {
                             executor = ListSetExecutor.discover(is, clazz, identifier, arg);
                         }
                         break;
                     case DUCK:
                         // if that didn't work, look for set(foo)
                         executor = DuckSetExecutor.discover(is, clazz, identifier, arg);
                         if (executor == null && property != null && property != identifier) {
                             executor = DuckSetExecutor.discover(is, clazz, property, arg);
                         }
                         break;
                     case FIELD:
                         // a field may be?
                         executor = FieldSetExecutor.discover(is, clazz, property, arg);
                         break;
                     case CONTAINER:
                     default:
                         continue; // in case we add new ones in enum
                 }
             } else {
                 executor = resolver.getPropertySet(this, obj, identifier, arg);
             }
             if (executor != null) {
                 return executor;
             }
         }
         return null;
     }
 
     @Override
     public JexlPropertySet getPropertySet(final Object obj, final Object identifier, final Object arg) {
         return getPropertySet(null, obj, identifier, arg);
     }
 
     @Override
     public List<PropertyResolver> getResolvers(final JexlOperator op, final Object obj) {
         return strategy.apply(op, obj);
     }
 
     @Override
     public int getVersion() {
         return version.intValue();
     }
 
     @Override
     public void setClassLoader(final ClassLoader nloader) {
         synchronized (this) {
             Introspector intro = ref.get();
             if (intro != null) {
                 intro.setLoader(nloader);
             } else {
                 intro = new Introspector(logger, nloader, permissions);
                 ref = new SoftReference<>(intro);
             }
             loader = new SoftReference<>(intro.getLoader());
             operatorMap.clear();
             version.incrementAndGet();
         }
     }
 }