/*
 * 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.juneau.serializer;

import static org.apache.juneau.commons.reflect.ReflectionUtils.*;
import static org.apache.juneau.commons.utils.AssertionUtils.*;
import static org.apache.juneau.commons.utils.CollectionUtils.*;
import static org.apache.juneau.commons.utils.ThrowableUtils.*;
import static org.apache.juneau.commons.utils.Utils.*;

import java.io.*;
import java.lang.reflect.*;
import java.text.*;
import java.util.*;
import java.util.function.*;
import java.util.stream.*;

import org.apache.juneau.*;
import org.apache.juneau.commons.collections.FluentMap;
import org.apache.juneau.commons.reflect.*;
import org.apache.juneau.cp.*;
import org.apache.juneau.httppart.*;
import org.apache.juneau.parser.*;
import org.apache.juneau.soap.*;
import org.apache.juneau.svl.*;
import org.apache.juneau.swap.*;

/**
 * Serializer session that lives for the duration of a single use of {@link Serializer}.
 *
 * <p>
 * Used by serializers for the following purposes:
 * <ul class='spaced-list'>
 *    <li>
 *       Keeping track of how deep it is in a model for indentation purposes.
 *    <li>
 *       Ensuring infinite loops don't occur by setting a limit on how deep to traverse a model.
 *    <li>
 *       Ensuring infinite loops don't occur from loops in the model (when detectRecursions is enabled.
 *    <li>
 *       Allowing serializer properties to be overridden on method calls.
 * </ul>
 *
 * <h5 class='section'>Notes:</h5><ul>
 *    <li class='warn'>This class is not thread safe and is typically discarded after one use.
 * </ul>
 *
 * <h5 class='section'>See Also:</h5><ul>
 *    <li class='link'><a class="doclink" href="https://juneau.apache.org/docs/topics/SerializersAndParsers">Serializers and Parsers</a>

 * </ul>
 */
public class SerializerSession extends BeanTraverseSession {
   /**
    * Builder class.
    */
   public static class Builder extends BeanTraverseSession.Builder {

      private HttpPartSchema schema;
      private Method javaMethod;
      private Serializer ctx;
      private UriContext uriContext;
      private VarResolverSession resolver;

      /**
       * Constructor
       *
       * @param ctx The context creating this session.
       *    <br>Cannot be <jk>null</jk>.
       */
      protected Builder(Serializer ctx) {
         super(assertArgNotNull("ctx", ctx));
         this.ctx = ctx;
         mediaTypeDefault(ctx.getResponseContentType());
         uriContext = ctx.getUriContext();
      }

      @Override /* Overridden from Builder */
      public <T> Builder apply(Class<T> type, Consumer<T> apply) {
         super.apply(type, apply);
         return this;
      }

      @Override
      public SerializerSession build() {
         return new SerializerSession(this);
      }

      @Override /* Overridden from Builder */
      public Builder debug(Boolean value) {
         super.debug(value);
         return this;
      }

      /**
       * The java method that called this serializer, usually the method in a REST servlet.
       *
       * @param value
       *    The new property value.
       *    <br>Can be <jk>null</jk> (value will not be set, existing value will be kept).
       * @return This object.
       */
      public Builder javaMethod(Method value) {
         if (nn(value))
            javaMethod = value;
         return this;
      }

      @Override /* Overridden from Builder */
      public Builder locale(Locale value) {
         super.locale(value);
         return this;
      }

      @Override /* Overridden from Builder */
      public Builder mediaType(MediaType value) {
         super.mediaType(value);
         return this;
      }

      @Override /* Overridden from Builder */
      public Builder mediaTypeDefault(MediaType value) {
         super.mediaTypeDefault(value);
         return this;
      }

      @Override /* Overridden from Builder */
      public Builder properties(Map<String,Object> value) {
         super.properties(value);
         return this;
      }

      @Override /* Overridden from Builder */
      public Builder property(String key, Object value) {
         super.property(key, value);
         return this;
      }

      /**
       * String variable resolver.
       *
       * <p>
       * If not specified, defaults to session created by {@link VarResolver#DEFAULT}.
       *
       * @param value
       *    The new property value.
       *    <br>Can be <jk>null</jk> (value will not be set, defaults to session created by {@link VarResolver#DEFAULT} when accessed).
       * @return This object.
       */
      public Builder resolver(VarResolverSession value) {
         if (nn(value))
            resolver = value;
         return this;
      }

      /**
       * HTTP-part schema.
       *
       * <p>
       * Used for schema-based serializers and parsers to define additional formatting.
       *
       * @param value
       *    The new value for this property.
       *    <br>Can be <jk>null</jk> (value will not be set, existing value will be kept).
       * @return This object.
       */
      public Builder schema(HttpPartSchema value) {
         if (nn(value))
            schema = value;
         return this;
      }

      /**
       * Same as {@link #schema(HttpPartSchema)} but doesn't overwrite the value if it is already set.
       *
       * @param value
       *    The new value for this property.
       *    <br>If <jk>null</jk>, then the locale defined on the context is used.
       * @return This object.
       */
      public Builder schemaDefault(HttpPartSchema value) {
         if (nn(value) && schema == null)
            schema = value;
         return this;
      }

      @Override /* Overridden from Builder */
      public Builder timeZone(TimeZone value) {
         super.timeZone(value);
         return this;
      }

      @Override /* Overridden from Builder */
      public Builder timeZoneDefault(TimeZone value) {
         super.timeZoneDefault(value);
         return this;
      }

      @Override /* Overridden from Builder */
      public Builder unmodifiable() {
         super.unmodifiable();
         return this;
      }

      /**
       * URI context bean.
       *
       * <p>
       * Bean used for resolution of URIs to absolute or root-relative form.
       *
       * <p>
       * If not specified, defaults to {@link Serializer.Builder#uriContext(UriContext)}.
       *
       * @param value
       *    The new property value.
       *    <br>Can be <jk>null</jk> (value will not be set, defaults to {@link Serializer.Builder#uriContext(UriContext)} from context).
       * @return This object.
       */
      public Builder uriContext(UriContext value) {
         if (nn(value))
            uriContext = value;
         return this;
      }
   }

   /**
    * Creates a new builder for this object.
    *
    * @param ctx The context creating this session.
    *    <br>Cannot be <jk>null</jk>.
    * @return A new builder.
    */
   public static Builder create(Serializer ctx) {
      return new Builder(assertArgNotNull("ctx", ctx));
   }

   /**
    * Create a "_type" property that contains the dictionary name of the bean.
    *
    * @param m The bean map to create a class property on.
    * @param typeName The type name of the bean.
    * @return A new bean property value.
    */
   protected static final BeanPropertyValue createBeanTypeNameProperty(BeanMap<?> m, String typeName) {
      BeanMeta<?> bm = m.getMeta();
      return new BeanPropertyValue(bm.getTypeProperty(), bm.getTypeProperty().getName(), typeName, null);
   }

   /**
    * Converts the specified throwable to either a {@link RuntimeException} or {@link SerializeException}.
    *
    * @param <T> The throwable type.
    * @param causedBy The exception to cast or wrap.
    */
   protected static <T extends Throwable> void handleThrown(T causedBy) {
      if (causedBy instanceof Error)
         throw (Error)causedBy;
      if (causedBy instanceof RuntimeException)
         throw (RuntimeException)causedBy;
      if (causedBy instanceof StackOverflowError)
         throw new SerializeException(
            "Stack overflow occurred.  This can occur when trying to serialize models containing loops.  It's recommended you use the BeanTraverseContext.BEANTRAVERSE_detectRecursions setting to help locate the loop.");
      if (causedBy instanceof SerializeException)
         throw (SerializeException)causedBy;
      throw new SerializeException(causedBy);
   }

   /**
    * Converts the contents of the specified object array to a list.
    *
    * <p>
    * Works on both object and primitive arrays.
    *
    * <p>
    * In the case of multi-dimensional arrays, the outgoing list will contain elements of type n-1 dimension.
    * i.e. if {@code type} is <code><jk>int</jk>[][]</code> then {@code list} will have entries of type
    * <code><jk>int</jk>[]</code>.
    *
    * @param type The type of array.
    * @param array The array being converted.
    * @return The array as a list.
    */
   protected static final List<Object> toList(Class<?> type, Object array) {
      var componentType = type.getComponentType();
      if (componentType.isPrimitive()) {
         var l = Array.getLength(array);
         var list = new ArrayList<>(l);
         for (var i = 0; i < l; i++)
            list.add(Array.get(array, i));
         return list;
      }
      return l((Object[])array);
   }

   private final HttpPartSchema schema;
   private final Method javaMethod;                                                // Java method that invoked this serializer.
   private final Serializer ctx;
   private final SerializerListener listener;
   private final UriResolver uriResolver;
   private VarResolverSession vrs;

   /**
    * Constructor.
    *
    * @param builder The builder for this object.
    */
   protected SerializerSession(Builder builder) {
      super(builder);
      ctx = builder.ctx;
      javaMethod = builder.javaMethod;
      schema = builder.schema;
      UriContext uriContext = builder.uriContext;
      uriResolver = UriResolver.of(ctx.getUriResolution(), ctx.getUriRelativity(), uriContext);
      vrs = builder.resolver;
      listener = BeanCreator.of(SerializerListener.class).type(ctx.getListener()).orElse(null);
   }

   /**
    * Adds a session object to the {@link VarResolverSession} in this session.
    *
    * @param <T> The bean type.
    * @param c The bean type being added.
    * @param value The bean being added.
    * @return This object.
    */
   public <T> SerializerSession addVarBean(Class<T> c, T value) {
      getVarResolver().bean(c, value);
      return this;
   }

   /**
    * Returns <jk>true</jk> if the specified value should not be serialized.
    *
    * @param cm The class type of the object being serialized.
    * @param attrName The bean attribute name, or <jk>null</jk> if this isn't a bean attribute.
    * @param value The object being serialized.
    * @return <jk>true</jk> if the specified value should not be serialized.
    * @throws SerializeException If recursion occurred.
    */
   public final boolean canIgnoreValue(ClassMeta<?> cm, String attrName, Object value) throws SerializeException {

      if (value == null && ! isKeepNullProperties())
         return true;

      if (value == null)
         return false;

      if (cm == null)
         cm = object();

      if (isTrimEmptyCollections()) {
         if (cm.isArray() || (cm.isObject() && isArray(value))) {
            if (((Object[])value).length == 0)
               return true;
         }
         if (cm.isCollection() || (cm.isObject() && info(value).isChildOf(Collection.class))) {
            if (((Collection<?>)value).isEmpty())
               return true;
         }
      }

      if (isTrimEmptyMaps()) {
         if (cm.isMap() || (cm.isObject() && info(value).isChildOf(Map.class))) {
            if (((Map<?,?>)value).isEmpty())
               return true;
         }
      }

      try {
         if ((! isKeepNullProperties()) && (willRecurse(attrName, value, cm) || willExceedDepth()))
            return true;
      } catch (BeanRecursionException e) {
         throw new SerializeException(e);
      }

      return false;
   }

   /**
    * Consumes each entry in the list.
    *
    * @param <E> The element type.
    * @param c The collection being sorted.
    * @param consumer The entry consumer.
    */
   public final <E> void forEachEntry(Collection<E> c, Consumer<E> consumer) {
      if (c == null || c.isEmpty())
         return;
      if (isSortCollections() && ! SortedSet.class.isInstance(c) && isSortable(c))
         c.stream().sorted().forEach(consumer);
      else
         c.forEach(consumer);
   }

   /**
    * Consumes each map entry in the map.
    *
    * @param <K> The key type.
    * @param <V> The value type.
    * @param m The map being consumed.
    * @param consumer The map entry consumer.
    */
   @SuppressWarnings({ "unchecked", "rawtypes", "cast" })
   public final <K,V> void forEachEntry(Map<K,V> m, Consumer<Map.Entry<K,V>> consumer) {
      if (m == null || m.isEmpty())
         return;
      if (isSortMaps() && ! SortedMap.class.isInstance(m) && isSortable(m.keySet()))
         ((Map)m).entrySet().stream().sorted(Map.Entry.comparingByKey()).forEach(x -> consumer.accept((Map.Entry<K,V>)x));
      else
         m.entrySet().forEach(consumer);
   }

   /**
    * Returns the listener associated with this session.
    *
    * @return The listener associated with this session, or <jk>null</jk> if there is no listener.
    */
   public SerializerListener getListener() { return listener; }

   /**
    * Returns the listener associated with this session.
    *
    * @param <T> The listener type.
    * @param c The listener class to cast to.
    * @return The listener associated with this session, or <jk>null</jk> if there is no listener.
    */
   @SuppressWarnings("unchecked")
   public <T extends SerializerListener> T getListener(Class<T> c) {
      return (T)listener;
   }

   /**
    * Optional method that specifies HTTP request headers for this serializer.
    *
    * <p>
    * For example, {@link SoapXmlSerializer} needs to set a <c>SOAPAction</c> header.
    *
    * <p>
    * This method is typically meaningless if the serializer is being used stand-alone (i.e. outside of a REST server
    * or client).
    *
    * <p>
    * The default implementation of this method simply calls {@link Serializer#getResponseHeaders(SerializerSession)}.
    *
    * @return
    *    The HTTP headers to set on HTTP requests.
    *    Never <jk>null</jk>.
    */
   public Map<String,String> getResponseHeaders() { return ctx.getResponseHeaders(this); }

   /**
    * HTTP part schema of object being serialized.
    *
    * @return HTTP part schema of object being serialized, or <jk>null</jk> if not specified.
    */
   public final HttpPartSchema getSchema() { return schema; }

   /**
    * Returns the variable resolver session.
    *
    * @return The variable resolver session.
    */
   public VarResolverSession getVarResolver() {
      if (vrs == null)
         vrs = createDefaultVarResolverSession();
      return vrs;
   }

   /**
    * Returns <jk>true</jk> if this serializer subclasses from {@link WriterSerializer}.
    *
    * @return <jk>true</jk> if this serializer subclasses from {@link WriterSerializer}.
    */
   public boolean isWriterSerializer() { return false; }

   /**
    * Resolves any variables in the specified string.
    *
    * @param string The string to resolve values in.
    * @return The string with variables resolved.
    */
   public String resolve(String string) {
      return getVarResolver().resolve(string);
   }

   /**
    * Converts a String to an absolute URI based on the {@link UriContext} on this session.
    *
    * @param uri
    *    The input URI.
    *    Can be any of the following:
    *    <ul>
    *       <li>{@link java.net.URI}
    *       <li>{@link java.net.URL}
    *       <li>{@link CharSequence}
    *    </ul>
    *    URI can be any of the following forms:
    *    <ul>
    *       <li><js>"foo://foo"</js> - Absolute URI.
    *       <li><js>"/foo"</js> - Root-relative URI.
    *       <li><js>"/"</js> - Root URI.
    *       <li><js>"context:/foo"</js> - Context-root-relative URI.
    *       <li><js>"context:/"</js> - Context-root URI.
    *       <li><js>"servlet:/foo"</js> - Servlet-path-relative URI.
    *       <li><js>"servlet:/"</js> - Servlet-path URI.
    *       <li><js>"request:/foo"</js> - Request-path-relative URI.
    *       <li><js>"request:/"</js> - Request-path URI.
    *       <li><js>"foo"</js> - Path-info-relative URI.
    *       <li><js>""</js> - Path-info URI.
    *    </ul>
    * @return The resolved URI.
    */
   public final String resolveUri(Object uri) {
      return uriResolver.resolve(uri);
   }

   /**
    * Shortcut method for serializing objects directly to either a <c>String</c> or <code><jk>byte</jk>[]</code>
    * depending on the serializer type.
    *
    * @param o The object to serialize.
    * @return
    *    The serialized object.
    *    <br>Character-based serializers will return a <c>String</c>.
    *    <br>Stream-based serializers will return a <code><jk>byte</jk>[]</code>.
    * @throws SerializeException If a problem occurred trying to convert the output.
    */
   public Object serialize(Object o) throws SerializeException {
      throw unsupportedOp();
   }

   /**
    * Serialize the specified object using the specified session.
    *
    * @param out Where to send the output from the serializer.
    * @param o The object to serialize.
    * @throws SerializeException If a problem occurred trying to convert the output.
    * @throws IOException Thrown by the underlying stream.
    */
   public final void serialize(Object o, Object out) throws SerializeException, IOException {
      try (SerializerPipe pipe = createPipe(out)) {
         doSerialize(pipe, o);
      } catch (SerializeException | IOException e) {
         throw e;
      } catch (@SuppressWarnings("unused") StackOverflowError e) {
         throw new SerializeException(this,
            "Stack overflow occurred.  This can occur when trying to serialize models containing loops.  It's recommended you use the BeanTraverseContext.BEANTRAVERSE_detectRecursions setting to help locate the loop.");
      } catch (Exception e) {
         throw new SerializeException(this, e);
      } finally {
         checkForWarnings();
      }
   }

   /**
    * Shortcut method for serializing an object to a String.
    *
    * @param o The object to serialize.
    * @return
    *    The serialized object.
    *    <br>Character-based serializers will return a <c>String</c>
    *    <br>Stream-based serializers will return a <code><jk>byte</jk>[]</code> converted to a string based on the {@link OutputStreamSerializer.Builder#binaryFormat(BinaryFormat)} setting.
    * @throws SerializeException If a problem occurred trying to convert the output.
    */
   public String serializeToString(Object o) throws SerializeException {
      throw unsupportedOp();
   }

   /**
    * Sorts the specified collection if {@link SerializerSession#isSortCollections()} returns <jk>true</jk>.
    *
    * @param <E> The element type.
    * @param c The collection being sorted.
    * @return A new sorted {@link TreeSet}.
    */
   public final <E> Collection<E> sort(Collection<E> c) {
      if (c == null || c.isEmpty() || SortedSet.class.isInstance(c))
         return c;
      if (isSortCollections() && isSortable(c))
         return c.stream().sorted().collect(Collectors.toList());
      return c;
   }

   /**
    * Sorts the specified collection if {@link SerializerSession#isSortCollections()} returns <jk>true</jk>.
    *
    * @param <E> The element type.
    * @param c The collection being sorted.
    * @return A new sorted {@link TreeSet}.
    */
   public final <E> List<E> sort(List<E> c) {
      if (c == null || c.isEmpty())
         return c;
      if (isSortCollections() && isSortable(c))
         return c.stream().sorted().collect(Collectors.toList());
      return c;
   }

   /**
    * Sorts the specified map if {@link SerializerSession#isSortMaps()} returns <jk>true</jk>.
    *
    * @param <K> The key type.
    * @param <V> The value type.
    * @param m The map being sorted.
    * @return A new sorted {@link TreeMap}.
    */
   public final <K,V> Map<K,V> sort(Map<K,V> m) {
      if (m == null || m.isEmpty() || SortedMap.class.isInstance(m))
         return m;
      if (isSortMaps() && isSortable(m.keySet()))
         return new TreeMap<>(m);
      return m;
   }

   /**
    * Converts the specified object to a <c>String</c>.
    *
    * <p>
    * Also has the following effects:
    * <ul>
    *    <li><c>Class</c> object is converted to a readable name.  See {@link ClassInfo#getNameFull()}.
    *    <li>Whitespace is trimmed if the trim-strings setting is enabled.
    * </ul>
    *
    * @param o The object to convert to a <c>String</c>.
    * @return The object converted to a String, or <jk>null</jk> if the input was <jk>null</jk>.
    */
   public final String toString(Object o) {
      if (o == null)
         return null;
      if (o.getClass() == Class.class)
         return info((Class<?>)o).getNameFull();
      if (o.getClass() == ClassInfo.class)
         return ((ClassInfo)o).getNameFull();
      if (o.getClass().isEnum())
         return getClassMetaForObject(o).toString(o);
      var s = o.toString();
      if (isTrimStrings())
         s = s.trim();
      return s;
   }

   /**
    * Trims the specified string if {@link SerializerSession#isTrimStrings()} returns <jk>true</jk>.
    *
    * @param o The input string to trim.
    * @return The trimmed string, or <jk>null</jk> if the input was <jk>null</jk>.
    */
   public final String trim(Object o) {
      if (o == null)
         return null;
      var s = o.toString();
      if (isTrimStrings())
         s = s.trim();
      return s;
   }

   private static boolean isSortable(Collection<?> c) {
      if (c == null)
         return false;
      for (var o : c)
         if (! (o instanceof Comparable))
            return false;
      return true;
   }

   /**
    * Adds a session object to the {@link VarResolverSession} in this session.
    *
    * @return This object.
    */
   protected VarResolverSession createDefaultVarResolverSession() {
      return VarResolver.DEFAULT.createSession();
   }

   /**
    * Wraps the specified input object into a {@link ParserPipe} object so that it can be easily converted into
    * a stream or reader.
    *
    * @param output
    *    The output location.
    *    <br>For character-based serializers, this can be any of the following types:
    *    <ul>
    *       <li>{@link Writer}
    *       <li>{@link OutputStream} - Output will be written as UTF-8 encoded stream.
    *       <li>{@link File} - Output will be written as system-default encoded stream.
    *       <li>{@link StringBuilder}
    *    </ul>
    *    <br>For byte-based serializers, this can be any of the following types:
    *    <ul>
    *       <li>{@link OutputStream}
    *       <li>{@link File}
    *    </ul>
    * @return
    *    A new {@link ParserPipe} wrapper around the specified input object.
    */
   protected SerializerPipe createPipe(Object output) {
      return new SerializerPipe(output);
   }

   /**
    * Serializes a POJO to the specified pipe.
    *
    * <p>
    * This method should NOT close the context object.
    *
    * <p>
    * The default implementation of this method simply calls {@link Serializer#doSerialize(SerializerSession,SerializerPipe,Object)}.
    *
    * @param pipe Where to send the output from the serializer.
    * @param o The object to serialize.
    * @throws IOException Thrown by underlying stream.
    * @throws SerializeException Problem occurred trying to serialize object.
    */
   protected void doSerialize(SerializerPipe pipe, Object o) throws IOException, SerializeException {
      ctx.doSerialize(this, pipe, o);
   }

   /**
    * Generalize the specified object if a POJO swap is associated with it.
    *
    * @param o The object to generalize.
    * @param type The type of object.
    * @return The generalized object, or <jk>null</jk> if the object is <jk>null</jk>.
    * @throws SerializeException If a problem occurred trying to convert the output.
    */
   @SuppressWarnings({ "rawtypes", "unchecked" })
   protected final Object generalize(Object o, ClassMeta<?> type) throws SerializeException {
      try {
         if (o == null)
            return null;
         ObjectSwap f = (type == null || type.isObject() || type.isString() ? getClassMeta(o.getClass()).getSwap(this) : type.getSwap(this));
         if (f == null)
            return o;
         return f.swap(this, o);
      } catch (SerializeException e) {
         throw e;
      } catch (Exception e) {
         throw new SerializeException(e);
      }
   }

   /**
    * Resolves the dictionary name for the actual type.
    *
    * @param session The current serializer session.
    * @param eType The expected type of the bean property.
    * @param aType The actual type of the bean property.
    * @param pMeta The current bean property being serialized.
    * @return The bean dictionary name, or <jk>null</jk> if a name could not be found.
    */
   @SuppressWarnings("null")
   protected final String getBeanTypeName(SerializerSession session, ClassMeta<?> eType, ClassMeta<?> aType, BeanPropertyMeta pMeta) {
      if (eType == aType || ! (isAddBeanTypes() || (session.isRoot() && isAddRootType())))
         return null;

      String eTypeTn = eType.getBeanDictionaryName();

      // First see if it's defined on the actual type.
      String tn = aType.getBeanDictionaryName();
      if (nn(tn) && ! tn.equals(eTypeTn)) {
         return tn;
      }

      // Then see if it's defined on the expected type.
      // The expected type might be an interface with mappings for implementation classes.
      BeanRegistry br = eType.getBeanRegistry();
      if (nn(br)) {
         tn = br.getTypeName(aType);
         if (nn(tn) && ! tn.equals(eTypeTn))
            return tn;
      }

      // Then look on the bean property.
      br = pMeta == null ? null : pMeta.getBeanRegistry();
      if (nn(br)) {
         tn = br.getTypeName(aType);
         if (nn(tn) && ! tn.equals(eTypeTn))
            return tn;
      }

      // Finally look in the session.
      br = getBeanRegistry();
      if (nn(br)) {
         tn = br.getTypeName(aType);
         if (nn(tn) && ! tn.equals(eTypeTn))
            return tn;
      }

      return null;
   }

   /**
    * Returns the parser-side expected type for the object.
    *
    * <p>
    * The return value depends on the {@link Serializer.Builder#addRootType()} setting.
    * When disabled, the parser already knows the Java POJO type being parsed, so there is
    * no reason to add <js>"_type"</js> attributes to the root-level object.
    *
    * @param o The object to get the expected type on.
    * @return The expected type.
    */
   protected final ClassMeta<?> getExpectedRootType(Object o) {
      if (isAddRootType())
         return object();
      var cm = getClassMetaForObject(o);
      if (nn(cm) && cm.isOptional())
         return cm.getElementType();
      return cm;
   }

   /**
    * Returns the Java method that invoked this serializer.
    *
    * <p>
    * When using the REST API, this is the Java method invoked by the REST call.
    * Can be used to access annotations defined on the method or class.
    *
    * @return The Java method that invoked this serializer.
   */
   protected final Method getJavaMethod() { return javaMethod; }

   /**
    * URI context bean.
    *
    * @see Serializer.Builder#uriContext(UriContext)
    * @return
    *    Bean used for resolution of URIs to absolute or root-relative form.
    */
   protected final UriContext getUriContext() { return ctx.getUriContext(); }

   /**
    * URI relativity.
    *
    * @see Serializer.Builder#uriRelativity(UriRelativity)
    * @return
    *    Defines what relative URIs are relative to when serializing any of the following:
    */
   protected final UriRelativity getUriRelativity() { return ctx.getUriRelativity(); }

   /**
    * URI resolution.
    *
    * @see Serializer.Builder#uriResolution(UriResolution)
    * @return
    *    Defines the resolution level for URIs when serializing URIs.
    */
   protected final UriResolution getUriResolution() { return ctx.getUriResolution(); }

   /**
    * Returns the URI resolver.
    *
    * @return The URI resolver.
    */
   protected final UriResolver getUriResolver() { return uriResolver; }

   /**
    * Add <js>"_type"</js> properties when needed.
    *
    * @see Serializer.Builder#addBeanTypes()
    * @return
    *    <jk>true</jk> if <js>"_type"</js> properties added to beans if their type cannot be inferred
    *    through reflection.
    */
   protected boolean isAddBeanTypes() { return ctx.isAddBeanTypes(); }

   /**
    * Add type attribute to root nodes.
    *
    * @see Serializer.Builder#addRootType()
    * @return
    *    <jk>true</jk> if type property should be added to root node.
    */
   protected final boolean isAddRootType() { return ctx.isAddRootType(); }

   /**
    * Don't trim null bean property values.
    *
    * @see Serializer.Builder#keepNullProperties()
    * @return
    *    <jk>true</jk> if null bean values are serialized to the output.
    */
   protected final boolean isKeepNullProperties() { return ctx.isKeepNullProperties(); }

   /**
    * Sort arrays and collections alphabetically.
    *
    * @see Serializer.Builder#sortCollections()
    * @return
    *    <jk>true</jk> if arrays and collections are copied and sorted before serialization.
    */
   protected final boolean isSortCollections() { return ctx.isSortCollections(); }

   /**
    * Sort maps alphabetically.
    *
    * @see Serializer.Builder#sortMaps()
    * @return
    *    <jk>true</jk> if maps are copied and sorted before serialization.
    */
   protected final boolean isSortMaps() { return ctx.isSortMaps(); }

   /**
    * Trim empty lists and arrays.
    *
    * @see Serializer.Builder#trimEmptyCollections()
    * @return
    *    <jk>true</jk> if empty lists and arrays are not serialized to the output.
    */
   protected final boolean isTrimEmptyCollections() { return ctx.isTrimEmptyCollections(); }

   /**
    * Trim empty maps.
    *
    * @see Serializer.Builder#trimEmptyMaps()
    * @return
    *    <jk>true</jk> if empty map values are not serialized to the output.
    */
   protected final boolean isTrimEmptyMaps() { return ctx.isTrimEmptyMaps(); }

   /**
    * Trim strings.
    *
    * @see Serializer.Builder#trimStrings()
    * @return
    *    <jk>true</jk> if string values will be trimmed of whitespace using {@link String#trim()} before being serialized.
    */
   protected boolean isTrimStrings() { return ctx.isTrimStrings(); }

   /**
    * Specialized warning when an exception is thrown while executing a bean getter.
    *
    * @param p The bean map entry representing the bean property.
    * @param t The throwable that the bean getter threw.
    * @throws SerializeException Thrown if ignoreInvocationExceptionOnGetters is false.
    */
   protected final void onBeanGetterException(BeanPropertyMeta p, Throwable t) throws SerializeException {
      if (nn(listener))
         listener.onBeanGetterException(this, t, p);
      String prefix = (isDebug() ? getStack(false) + ": " : "");
      addWarning("{0}Could not call getValue() on property ''{1}'' of class ''{2}'', exception = {3}", prefix, p.getName(), p.getBeanMeta().getClassMeta(), lm(t));
      if (! isIgnoreInvocationExceptionsOnGetters())
         throw new SerializeException(this, "{0}Could not call getValue() on property ''{1}'' of class ''{2}'', exception = {3}", prefix, p.getName(), p.getBeanMeta().getClassMeta(), lm(t))
            .initCause(t);
   }

   /**
    * Logs a warning message.
    *
    * @param t The throwable that was thrown (if there was one).
    * @param msg The warning message.
    * @param args Optional {@link MessageFormat}-style arguments.
    */
   @Override
   protected void onError(Throwable t, String msg, Object...args) {
      if (nn(listener))
         listener.onError(this, t, f(msg, args));
      super.onError(t, msg, args);
   }

   @Override /* Overridden from BeanTraverseSession */
   protected FluentMap<String,Object> properties() {
      return super.properties()
         .a("uriResolver", uriResolver);
   }

   /**
    * Same as {@link #push(String, Object, ClassMeta)} but wraps {@link BeanRecursionException} inside {@link SerializeException}.
    *
    * @param attrName The attribute name.
    * @param o The current object being traversed.
    * @param eType The expected class type.
    * @return
    *    The {@link ClassMeta} of the object so that <c>instanceof</c> operations only need to be performed
    *    once (since they can be expensive).
    * @throws SerializeException If recursion occurred.
    */
   protected final ClassMeta<?> push2(String attrName, Object o, ClassMeta<?> eType) throws SerializeException {
      try {
         return super.push(attrName, o, eType);
      } catch (BeanRecursionException e) {
         throw new SerializeException(e);
      }
   }

   /**
    * Opposite of {@link #resolveUri(Object)}.
    *
    * <p>
    * Converts the URI to a value relative to the specified <c>relativeTo</c> parameter.
    *
    * <p>
    * Both parameters can be any of the following:
    * <ul>
    *    <li>{@link java.net.URI}
    *    <li>{@link java.net.URL}
    *    <li>{@link CharSequence}
    * </ul>
    *
    * <p>
    * Both URIs can be any of the following forms:
    * <ul>
    *    <li><js>"foo://foo"</js> - Absolute URI.
    *    <li><js>"/foo"</js> - Root-relative URI.
    *    <li><js>"/"</js> - Root URI.
    *    <li><js>"context:/foo"</js> - Context-root-relative URI.
    *    <li><js>"context:/"</js> - Context-root URI.
    *    <li><js>"servlet:/foo"</js> - Servlet-path-relative URI.
    *    <li><js>"servlet:/"</js> - Servlet-path URI.
    *    <li><js>"request:/foo"</js> - Request-path-relative URI.
    *    <li><js>"request:/"</js> - Request-path URI.
    *    <li><js>"foo"</js> - Path-info-relative URI.
    *    <li><js>""</js> - Path-info URI.
    * </ul>
    *
    * @param relativeTo The URI to relativize against.
    * @param uri The URI to relativize.
    * @return The relativized URI.
    */
   protected final String relativizeUri(Object relativeTo, Object uri) {
      return uriResolver.relativize(relativeTo, uri);
   }

   /**
    * Invokes the specified swap on the specified object if the swap is not null.
    *
    * @param swap The swap to invoke.  Can be <jk>null</jk>.
    * @param o The input object.
    * @return The swapped object.
    * @throws SerializeException If swap method threw an exception.
    */
   @SuppressWarnings({ "rawtypes", "unchecked" })
   protected Object swap(ObjectSwap swap, Object o) throws SerializeException {
      try {
         if (swap == null)
            return o;
         return swap.swap(this, o);
      } catch (Exception e) {
         throw new SerializeException(e);
      }
   }
}