/*
 * 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.bean.openapi3;

import static org.apache.juneau.commons.utils.CollectionUtils.*;
import static org.apache.juneau.bean.openapi3.OpenApiCopyUtils.*;
import static org.apache.juneau.commons.utils.CollectionUtils.contains;
import static org.apache.juneau.commons.utils.Shorts.*;
import static org.apache.juneau.commons.utils.StringUtils.*;
import static org.apache.juneau.marshall.internal.ConverterUtils.*;

import java.util.*;

import org.apache.juneau.commons.bean.*;
import org.apache.juneau.commons.collections.*;
import org.apache.juneau.marshall.collections.*;
import org.apache.juneau.marshall.marshaller.*;

/**
 * A limited subset of JSON-Schema's items object.
 *
 * <p>
 * The Items Object is a limited subset of JSON-Schema's items object. It is used by parameter definitions that are
 * not located in "body" to describe the type of items in an array. This is particularly useful for query parameters,
 * path parameters, and header parameters that accept arrays.
 *
 * <h5 class='section'>OpenAPI Specification:</h5>
 * <p>
 * The Items Object supports the following fields from JSON Schema:
 * <ul class='spaced-list'>
 *    <li><c>type</c> (string, REQUIRED) - The data type. Values: <js>"string"</js>, <js>"number"</js>, <js>"integer"</js>, <js>"boolean"</js>, <js>"array"</js>
 *    <li><c>format</c> (string) - The format modifier (e.g., <js>"int32"</js>, <js>"int64"</js>, <js>"float"</js>, <js>"double"</js>, <js>"date"</js>, <js>"date-time"</js>)
 *    <li><c>items</c> ({@link Items}) - Required if type is <js>"array"</js>. Describes the type of items in the array
 *    <li><c>collectionFormat</c> (string) - How multiple values are formatted. Values: <js>"csv"</js>, <js>"ssv"</js>, <js>"tsv"</js>, <js>"pipes"</js>, <js>"multi"</js>
 *    <li><c>default</c> (any) - The default value
 *    <li><c>maximum</c> (number), <c>exclusiveMaximum</c> (boolean), <c>minimum</c> (number), <c>exclusiveMinimum</c> (boolean) - Numeric constraints
 *    <li><c>maxLength</c> (integer), <c>minLength</c> (integer), <c>pattern</c> (string) - String constraints
 *    <li><c>maxItems</c> (integer), <c>minItems</c> (integer), <c>uniqueItems</c> (boolean) - Array constraints
 *    <li><c>enum</c> (array) - Possible values for this item
 *    <li><c>multipleOf</c> (number) - Must be a multiple of this value
 * </ul>
 *
 * <h5 class='section'>Example:</h5>
 * <p class='bcode'>
 *    <jc>// Construct using SwaggerBuilder.</jc>
 *    Items <jv>x</jv> = <jsm>items</jsm>(<js>"string"</js>).minLength(2);
 *
 *    <jc>// Serialize using JsonSerializer.</jc>
 *    String <jv>json</jv> = Json.<jsm>from</jsm>(<jv>x</jv>);
 *
 *    <jc>// Or just use toString() which does the same as above.</jc>
 *    String <jv>json</jv> = <jv>x</jv>.toString();
 * </p>
 * <p class='bcode'>
 *    <jc>// Output</jc>
 *    {
 *       <js>"type"</js>: <js>"string"</js>,
 *       <js>"minLength"</js>: 2
 *    }
 * </p>
 *
 * <h5 class='section'>See Also:</h5><ul>
 *    <li class='link'><a class="doclink" href="https://spec.openapis.org/oas/v3.0.0#items-object">OpenAPI Specification &gt; Items Object</a>
 *    <li class='link'><a class="doclink" href="https://swagger.io/docs/specification/describing-parameters/">OpenAPI Describing Parameters</a>
 *    <li class='link'><a class="doclink" href="https://juneau.apache.org/docs/topics/JuneauBeanOpenApi3">juneau-bean-openapi-v3</a>
 * </ul>
 */
@SuppressWarnings({
   "java:S116", // Field name uses trailing underscore (default_) to avoid Java keyword conflict
   "java:S1192" // Duplicated literals (property names) read more clearly inline than as constants
})
public class Items extends OpenApiElement {

   private static final String[] VALID_TYPES = { "string", "number", "integer", "boolean", "array" };
   private static final String[] VALID_COLLECTION_FORMATS = { "csv", "ssv", "tsv", "pipes", "multi" };

   private String type;
   private String format;
   private String collectionFormat;
   private String pattern;
   private String ref;
   private Number maximum;
   private Number minimum;
   private Number multipleOf;
   private Integer maxLength;
   private Integer minLength;
   private Integer maxItems;
   private Integer minItems;
   private Boolean exclusiveMaximum;
   private Boolean exclusiveMinimum;
   private Boolean uniqueItems;
   @SuppressWarnings({
      "java:S1700"  // Field duplicates class name per OpenAPI spec
   })
   private Items items;
   private Object default_;
   private List<Object> enum_ = list();

   /**
    * Default constructor.
    */
   public Items() {}

   /**
    * Copy constructor.
    *
    * @param copyFrom The object to copy.
    */
   public Items(Items copyFrom) {
      super(copyFrom);

      this.type = copyFrom.type;
      this.format = copyFrom.format;
      this.collectionFormat = copyFrom.collectionFormat;
      this.pattern = copyFrom.pattern;
      this.maximum = copyFrom.maximum;
      this.minimum = copyFrom.minimum;
      this.multipleOf = copyFrom.multipleOf;
      this.maxLength = copyFrom.maxLength;
      this.minLength = copyFrom.minLength;
      this.maxItems = copyFrom.maxItems;
      this.minItems = copyFrom.minItems;
      this.exclusiveMaximum = copyFrom.exclusiveMaximum;
      this.exclusiveMinimum = copyFrom.exclusiveMinimum;
      this.uniqueItems = copyFrom.uniqueItems;
      this.items = copyOf(copyFrom.items);
      this.default_ = copyFrom.default_;
      this.enum_.addAll(copyOf(copyFrom.enum_));
      this.ref = copyFrom.ref;
   }

   /**
    * Adds one or more values to the <property>enum</property> property.
    *
    * @param values
    *    The values to add to this property.
    *    <br>Ignored if <jk>null</jk>.
    * @return This object
    */
   public Items addEnum(Object...values) {
      addAllNn(enum_, values);
      return this;
   }

   /**
    * Make a deep copy of this object.
    *
    * @return A deep copy of this object.
    */
   public Items copy() {
      return new Items(this);
   }

   @Override /* Overridden from SwaggerElement */
   public <T> T get(String property, Class<T> type) {
      reqnn("property", property);
      return switch (property) {
         case "type" -> toType(getType(), type);
         case "format" -> toType(getFormat(), type);
         case "items" -> toType(getItems(), type);
         case "collectionFormat" -> toType(getCollectionFormat(), type);
         case "default" -> toType(getDefault(), type);
         case "maximum" -> toType(getMaximum(), type);
         case "exclusiveMaximum" -> toType(getExclusiveMaximum(), type);
         case "minimum" -> toType(getMinimum(), type);
         case "exclusiveMinimum" -> toType(getExclusiveMinimum(), type);
         case "maxLength" -> toType(getMaxLength(), type);
         case "minLength" -> toType(getMinLength(), type);
         case "pattern" -> toType(getPattern(), type);
         case "maxItems" -> toType(getMaxItems(), type);
         case "minItems" -> toType(getMinItems(), type);
         case "uniqueItems" -> toType(getUniqueItems(), type);
         case "enum" -> toType(getEnum(), type);
         case "multipleOf" -> toType(getMultipleOf(), type);
         case "$ref" -> toType(getRef(), type);
         default -> super.get(property, type);
      };
   }

   /**
    * Bean property getter:  <property>collectionFormat</property>.
    *
    * <p>
    * Determines the format of the array if type array is used.
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public String getCollectionFormat() { return collectionFormat; }

   /**
    * Bean property getter:  <property>default</property>.
    *
    * <p>
    * Declares the value of the item that the server will use if none is provided.
    *
    * <h5 class='section'>Notes:</h5>
    * <ul class='spaced-list'>
    *    <li>
    *       <js>"default"</js> has no meaning for required items.
    *    <li>
    *       Unlike JSON Schema this value MUST conform to the defined <code>type</code> for the data type.
    * </ul>
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public Object getDefault() { return default_; }

   /**
    * Bean property getter:  <property>enum</property>.
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public List<Object> getEnum() { return nie(enum_); }

   /**
    * Bean property getter:  <property>exclusiveMaximum</property>.
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public Boolean getExclusiveMaximum() { return exclusiveMaximum; }

   /**
    * Bean property getter:  <property>exclusiveMinimum</property>.
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public Boolean getExclusiveMinimum() { return exclusiveMinimum; }

   /**
    * Bean property getter:  <property>format</property>.
    *
    * <p>
    * The extending format for the previously mentioned <code>type</code>.
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public String getFormat() { return format; }

   /**
    * Bean property getter:  <property>items</property>.
    *
    * <p>
    * Describes the type of items in the array.
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public Items getItems() { return items; }

   /**
    * Bean property getter:  <property>maximum</property>.
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public Number getMaximum() { return maximum; }

   /**
    * Bean property getter:  <property>maxItems</property>.
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public Integer getMaxItems() { return maxItems; }

   /**
    * Bean property getter:  <property>maxLength</property>.
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public Integer getMaxLength() { return maxLength; }

   /**
    * Bean property getter:  <property>minimum</property>.
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public Number getMinimum() { return minimum; }

   /**
    * Bean property getter:  <property>minItems</property>.
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public Integer getMinItems() { return minItems; }

   /**
    * Bean property getter:  <property>minLength</property>.
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public Integer getMinLength() { return minLength; }

   /**
    * Bean property getter:  <property>multipleOf</property>.
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public Number getMultipleOf() { return multipleOf; }

   /**
    * Bean property getter:  <property>pattern</property>.
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public String getPattern() { return pattern; }

   /**
    * Bean property getter:  <property>$ref</property>.
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   @BeanProp("$ref")
   public String getRef() { return ref; }

   /**
    * Bean property getter:  <property>type</property>.
    *
    * <p>
    * The internal type of the array.
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public String getType() { return type; }

   /**
    * Bean property getter:  <property>uniqueItems</property>.
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public Boolean getUniqueItems() { return uniqueItems; }

   @Override /* Overridden from SwaggerElement */
   public Set<String> keySet() {
      // @formatter:off
      var s = stb(String.class)
         .addIf(nn(ref), "$ref")
         .addIf(nn(collectionFormat), "collectionFormat")
         .addIf(nn(default_), "default")
         .addIf(ine(enum_), "enum")
         .addIf(nn(exclusiveMaximum), "exclusiveMaximum")
         .addIf(nn(exclusiveMinimum), "exclusiveMinimum")
         .addIf(nn(format), "format")
         .addIf(nn(items), "items")
         .addIf(nn(maxItems), "maxItems")
         .addIf(nn(maxLength), "maxLength")
         .addIf(nn(maximum), "maximum")
         .addIf(nn(minItems), "minItems")
         .addIf(nn(minLength), "minLength")
         .addIf(nn(minimum), "minimum")
         .addIf(nn(multipleOf), "multipleOf")
         .addIf(nn(pattern), "pattern")
         .addIf(nn(type), "type")
         .addIf(nn(uniqueItems), "uniqueItems")
         .build();
      // @formatter:on
      return new MultiSet<>(s, super.keySet());
   }

   /**
    * Resolves any <js>"$ref"</js> attributes in this element.
    *
    * @param openApi The swagger document containing the definitions.
    * @param refStack Keeps track of previously-visited references so that we don't cause recursive loops.
    * @param maxDepth
    *    The maximum depth to resolve references.
    *    <br>After that level is reached, <code>$ref</code> references will be left alone.
    *    <br>Useful if you have very complex models and you don't want your swagger page to be overly-complex.
    * @return
    *    This object with references resolved.
    *    <br>May or may not be the same object.
    */
   public Items resolveRefs(OpenApi openApi, Deque<String> refStack, int maxDepth) {

      if (nn(ref)) {
         if (refStack.contains(ref) || refStack.size() >= maxDepth)
            return this;
         refStack.addLast(ref);
         var r = openApi.findRef(ref, Items.class);
         r = r.resolveRefs(openApi, refStack, maxDepth);
         refStack.removeLast();
         return r;
      }

      set("properties", resolveRefs(get("properties"), openApi, refStack, maxDepth));

      if (nn(items))
         items = items.resolveRefs(openApi, refStack, maxDepth);

      set("example", null);

      return this;
   }

   @Override /* Overridden from SwaggerElement */
   public Items set(String property, Object value) {
      reqnn("property", property);
      return switch (property) {
         case "$ref" -> setRef(value);
         case "collectionFormat" -> setCollectionFormat(s(value));
         case "default" -> setDefault(value);
         case "enum" -> setEnum(value);
         case "exclusiveMaximum" -> setExclusiveMaximum(toBoolean(value));
         case "exclusiveMinimum" -> setExclusiveMinimum(toBoolean(value));
         case "format" -> setFormat(s(value));
         case "items" -> setItems(toType(value, Items.class));
         case "maxItems" -> setMaxItems(toInteger(value));
         case "maxLength" -> setMaxLength(toInteger(value));
         case "maximum" -> setMaximum(toNumber(value));
         case "minItems" -> setMinItems(toInteger(value));
         case "minLength" -> setMinLength(toInteger(value));
         case "minimum" -> setMinimum(toNumber(value));
         case "multipleOf" -> setMultipleOf(toNumber(value));
         case "pattern" -> setPattern(s(value));
         case "type" -> setType(s(value));
         case "uniqueItems" -> setUniqueItems(toBoolean(value));
         default -> {
            super.set(property, value);
            yield this;
         }
      };
   }

   /**
    * Bean property setter:  <property>collectionFormat</property>.
    *
    * <p>
    * Determines the format of the array if type array is used.
    *
    * @param value
    *    The new value for this property.
    *    <br>Valid values:
    *    <ul>
    *       <li><js>"csv"</js> (default) - comma separated values <code>foo,bar</code>.
    *       <li><js>"ssv"</js> - space separated values <code>foo bar</code>.
    *       <li><js>"tsv"</js> - tab separated values <code>foo\tbar</code>.
    *       <li><js>"pipes"</js> - pipe separated values <code>foo|bar</code>.
    *    </ul>
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object
    */
   public Items setCollectionFormat(String value) {
      if (isStrict() && ! contains(value, VALID_COLLECTION_FORMATS))
         throw rex("Invalid value passed in to setCollectionFormat(String).  Value='%s', valid values=[%s]", value, toCdl(VALID_COLLECTION_FORMATS));
      collectionFormat = value;
      return this;
   }

   /**
    * Bean property setter:  <property>default</property>.
    *
    * <p>
    * Declares the value of the item that the server will use if none is provided.
    *
    * <h5 class='section'>Notes:</h5>
    * <ul class='spaced-list'>
    *    <li>
    *       <js>"default"</js> has no meaning for required items.
    *    <li>
    *       Unlike JSON Schema this value MUST conform to the defined <code>type</code> for the data type.
    * </ul>
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object
    */
   public Items setDefault(Object value) {
      default_ = value;
      return this;
   }

   /**
    * Bean property setter:  <property>enum</property>.
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object
    */
   public Items setEnum(Collection<Object> value) {
      enum_.clear();
      if (nn(value))
         enum_.addAll(value);
      return this;
   }

   /**
    * Adds one or more values to the <property>enum</property> property.
    *
    * @param values
    *    The values to add to this property.
    *    <br>Valid types:
    *    <ul>
    *       <li><code>Object</code>
    *       <li><code>Collection&lt;Object&gt;</code>
    *       <li><code>String</code> - JSON array representation of <code>Collection&lt;Object&gt;</code>
    *          <h5 class='figure'>Example:</h5>
    *          <p class='bcode'>
    *    enum_(<js>"['foo','bar']"</js>);
    *          </p>
    *       <li><code>String</code> - Individual values
    *          <h5 class='figure'>Example:</h5>
    *          <p class='bcode'>
    *    enum_(<js>"foo"</js>, <js>"bar"</js>);
    *          </p>
    *    </ul>
    *    <br>Ignored if <jk>null</jk>.
    * @return This object
    */
   public Items setEnum(Object...values) {
      enum_ = lb(Object.class).sparse().addAny(enum_, values).build();
      return this;
   }

   /**
    * Bean property setter:  <property>exclusiveMaximum</property>.
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object
    */
   public Items setExclusiveMaximum(Boolean value) {
      exclusiveMaximum = value;
      return this;
   }

   /**
    * Bean property setter:  <property>exclusiveMinimum</property>.
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object
    */
   public Items setExclusiveMinimum(Boolean value) {
      exclusiveMinimum = value;
      return this;
   }

   /**
    * Bean property setter:  <property>format</property>.
    *
    * <p>
    * The extending format for the previously mentioned <code>type</code>.
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object
    */
   public Items setFormat(String value) {
      format = value;
      return this;
   }

   /**
    * Bean property setter:  <property>items</property>.
    *
    * <p>
    * Describes the type of items in the array.
    *
    * @param value
    *    The new value for this property.
    *    <br>Property value is required if <code>type</code> is <js>"array"</js>.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object
    */
   public Items setItems(Items value) {
      items = value;
      return this;
   }

   /**
    * Bean property setter:  <property>maximum</property>.
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object
    */
   public Items setMaximum(Number value) {
      maximum = value;
      return this;
   }

   /**
    * Bean property setter:  <property>maxItems</property>.
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object
    */
   public Items setMaxItems(Integer value) {
      maxItems = value;
      return this;
   }

   /**
    * Bean property setter:  <property>maxLength</property>.
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object
    */
   public Items setMaxLength(Integer value) {
      maxLength = value;
      return this;
   }

   /**
    * Bean property setter:  <property>minimum</property>.
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object
    */
   public Items setMinimum(Number value) {
      minimum = value;
      return this;
   }

   /**
    * Bean property setter:  <property>minItems</property>.
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object
    */
   public Items setMinItems(Integer value) {
      minItems = value;
      return this;
   }

   /**
    * Bean property setter:  <property>minLength</property>.
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object
    */
   public Items setMinLength(Integer value) {
      minLength = value;
      return this;
   }

   /**
    * Bean property setter:  <property>multipleOf</property>.
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object
    */
   public Items setMultipleOf(Number value) {
      multipleOf = value;
      return this;
   }

   /**
    * Bean property setter:  <property>pattern</property>.
    *
    * <p>
    * This string SHOULD be a valid regular expression.
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object
    */
   public Items setPattern(String value) {
      pattern = value;
      return this;
   }

   /**
    * Bean property setter:  <property>$ref</property>.
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object
    */
   @BeanProp("$ref")
   public Items setRef(Object value) {
      ref = s(value);
      return this;
   }

   /**
    * Bean property setter:  <property>type</property>.
    *
    * <p>
    * The internal type of the array.
    *
    * @param value
    *    The new value for this property.
    *    <br>Valid values:
    *    <ul>
    *       <li><js>"string"</js>
    *       <li><js>"number"</js>
    *       <li><js>"integer"</js>
    *       <li><js>"boolean"</js>
    *       <li><js>"array"</js>
    *    </ul>
    *    <br>Property value is required.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object
    */
   public Items setType(String value) {
      if (isStrict() && ! contains(value, VALID_TYPES))
         throw iaex("Invalid value passed in to setType(String).  Value='%s', valid values=%s", value, Json5.of(VALID_TYPES));
      type = value;
      return this;
   }

   /**
    * Bean property setter:  <property>uniqueItems</property>.
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object
    */
   public Items setUniqueItems(Boolean value) {
      uniqueItems = value;
      return this;
   }

   @Override /* Overridden from OpenApiElement */
   public Items strict(Object value) {
      super.strict(value);
      return this;
   }

   /* Resolve references in extra attributes */
   private Object resolveRefs(Object o, OpenApi openApi, Deque<String> refStack, int maxDepth) {
      if (o instanceof MarshalledMap o2) {
         var ref2 = o2.get("$ref");
         if (ref2 instanceof CharSequence) {
            var sref = ref2.toString();
            if (refStack.contains(sref) || refStack.size() >= maxDepth)
               return o;
            refStack.addLast(sref);
            var o3 = openApi.findRef(sref, Object.class);
            o3 = resolveRefs(o3, openApi, refStack, maxDepth);
            refStack.removeLast();
            return o3;
         }
         for (var e : o2.entrySet())
            e.setValue(resolveRefs(e.getValue(), openApi, refStack, maxDepth));
      }
      if (o instanceof MarshalledList o2)
         for (var li = o2.listIterator(); li.hasNext();)
            li.set(resolveRefs(li.next(), openApi, refStack, maxDepth));
      return o;
   }

   @Override /* Overridden from SwaggerElement */
   protected Items strict() {
      super.strict();
      return this;
   }
}