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// * 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  *
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// * specific language governing permissions and limitations under the License.                                              *
// ***************************************************************************************************************************
package org.apache.juneau.dto.swagger;

import static org.apache.juneau.internal.ArrayUtils.*;
import static org.apache.juneau.internal.StringUtils.*;
import static org.apache.juneau.internal.ConverterUtils.*;
import static org.apache.juneau.internal.CollectionUtils.*;

import java.util.*;

import org.apache.juneau.*;
import org.apache.juneau.annotation.*;
import org.apache.juneau.collections.*;
import org.apache.juneau.internal.*;
import org.apache.juneau.json.*;

/**
 * A limited subset of JSON-Schema's items object.
 *
 * <p>
 * It is used by parameter definitions that are not located in "body".
 *
 * <h5 class='section'>Example:</h5>
 * <p class='bcode w800'>
 *    <jc>// Construct using SwaggerBuilder.</jc>
 *    Items x = <jsm>items</jsm>(<js>"string"</js>).minLength(2);
 *
 *    <jc>// Serialize using JsonSerializer.</jc>
 *    String json = JsonSerializer.<jsf>DEFAULT</jsf>.toString(x);
 *
 *    <jc>// Or just use toString() which does the same as above.</jc>
 *    String json = x.toString();
 * </p>
 * <p class='bcode w800'>
 *    <jc>// Output</jc>
 *    {
 *       <js>"type"</js>: <js>"string"</js>,
 *       <js>"minLength"</js>: 2
 *    }
 * </p>
 *
 * <ul class='seealso'>
 *    <li class='link'>{@doc DtoSwagger}
 * </ul>
 */
@Bean(bpi="type,format,items,collectionFormat,default,maximum,exclusiveMaximum,minimum,exclusiveMinimum,maxLength,minLength,pattern,maxItems,minItems,uniqueItems,enum,multipleOf,$ref,*")
public class Items extends SwaggerElement {

   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,
      format,
      collectionFormat,
      pattern,
      ref;
   private Number
      maximum,
      minimum,
      multipleOf;
   private Integer
      maxLength,
      minLength,
      maxItems,
      minItems;
   private Boolean
      exclusiveMaximum,
      exclusiveMinimum,
      uniqueItems;
   private Items items;
   private Object _default;
   private List<Object> _enum;

   /**
    * 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 = copyFrom.items == null ? null : copyFrom.items.copy();
      this._default = copyFrom._default;
      this._enum = newList(copyFrom._enum);
      this.ref = copyFrom.ref;
   }

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


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

   /**
    * 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 setter:  <property>type</property>.
    *
    * <p>
    * The internal type of the array.
    *
    * <ul class='seealso'>
    *    <li class='extlink'>{@doc ExtSwaggerDataTypes}
    * </ul>
    *
    * @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.
    * @return This object (for method chaining).
    */
   public Items setType(String value) {
      if (isStrict() && ! contains(value, VALID_TYPES))
         throw new RuntimeException(
            "Invalid value passed in to setType(String).  Value='"+value+"', valid values="
            + SimpleJsonSerializer.DEFAULT.toString(VALID_TYPES));
      type = value;
      return this;
   }

   /**
    * Same as {@link #setType(String)}.
    *
    * @param value
    *    The new value for this property.
    *    <br>Non-String values will be converted to String using <c>toString()</c>.
    *    <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>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items type(Object value) {
      return setType(stringify(value));
   }

   /**
    * Bean property getter:  <property>format</property>.
    *
    * <p>
    * The extending format for the previously mentioned <c>type</c>.
    *
    * <ul class='seealso'>
    *    <li class='extlink'>{@doc ExtSwaggerDataTypeFormats}
    * </ul>
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public String getFormat() {
      return format;
   }

   /**
    * Bean property setter:  <property>format</property>.
    *
    * <p>
    * The extending format for the previously mentioned <c>type</c>.
    *
    * <ul class='seealso'>
    *    <li class='extlink'>{@doc ExtSwaggerDataTypeFormats}
    * </ul>
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items setFormat(String value) {
      format = value;
      return this;
   }

   /**
    * Same as {@link #setFormat(String)}.
    *
    * @param value
    *    The new value for this property.
    *    <br>Non-String values will be converted to String using <c>toString()</c>.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items format(Object value) {
      return setFormat(stringify(value));
   }

   /**
    * 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 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 <c>type</c> is <js>"array"</js>.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items setItems(Items value) {
      items = value;
      return this;
   }

   /**
    * Same as {@link #setItems(Items)}.
    *
    * @param value
    *    The new value for this property.
    *    <br>Property value is required if <c>type</c> is <js>"array"</js>.
    *    <br>Valid types:
    *    <ul>
    *       <li>{@link Items}
    *       <li><c>String</c> - JSON object representation of {@link Items}
    *          <p class='bcode w800'>
    *    <jc>// Example </jc>
    *    items(<js>"{type:'type',format:'format',...}"</js>);
    *          </p>
    *    </ul>
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items items(Object value) {
      return setItems(toType(value, Items.class));
   }

   /**
    * 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 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 <c>foo,bar</c>.
    *       <li><js>"ssv"</js> - space separated values <c>foo bar</c>.
    *       <li><js>"tsv"</js> - tab separated values <c>foo\tbar</c>.
    *       <li><js>"pipes"</js> - pipe separated values <c>foo|bar</c>.
    *    </ul>
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items setCollectionFormat(String value) {
      if (isStrict() && ! contains(value, VALID_COLLECTION_FORMATS))
         throw new BasicRuntimeException(
            "Invalid value passed in to setCollectionFormat(String).  Value=''{0}'', valid values={1}",
            value, VALID_COLLECTION_FORMATS
         );
      collectionFormat = value;
      return this;
   }

   /**
    * Same as {@link #setCollectionFormat(String)}.
    *
    * @param value
    *    The new value for this property.
    *    <br>Non-String values will be converted to String using <c>toString()</c>.
    *    <br>Valid values:
    *    <ul>
    *       <li><js>"csv"</js> (default) - comma separated values <c>foo,bar</c>.
    *       <li><js>"ssv"</js> - space separated values <c>foo bar</c>.
    *       <li><js>"tsv"</js> - tab separated values <c>foo\tbar</c>.
    *       <li><js>"pipes"</js> - pipe separated values <c>foo|bar</c>.
    *    </ul>
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items collectionFormat(Object value) {
      return setCollectionFormat(stringify(value));
   }

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

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

   /**
    * Same as {@link #setDefault(Object)}.
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items _default(Object value) {
      return setDefault(value);
   }

   /**
    * Bean property getter:  <property>maximum</property>.
    *
    * <ul class='seealso'>
    *    <li class='extlink'>{@doc ExtJsonSchemaValidation}
    * </ul>
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public Number getMaximum() {
      return maximum;
   }

   /**
    * Bean property setter:  <property>maximum</property>.
    *
    * <ul class='seealso'>
    *    <li class='extlink'>{@doc ExtJsonSchemaValidation}
    * </ul>
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items setMaximum(Number value) {
      maximum = value;
      return this;
   }

   /**
    * Same as {@link #setMaximum(Number)}.
    *
    * @param value
    *    The new value for this property.
    *    <br>Non-Number values will be converted to Number using <c>toString()</c> then best number match.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items maximum(Object value) {
      return setMaximum(toNumber(value));
   }

   /**
    * Bean property getter:  <property>exclusiveMaximum</property>.
    *
    * <ul class='seealso'>
    *    <li class='extlink'>{@doc ExtJsonSchemaValidation}
    * </ul>
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public Boolean getExclusiveMaximum() {
      return exclusiveMaximum;
   }

   /**
    * Bean property setter:  <property>exclusiveMaximum</property>.
    *
    * <ul class='seealso'>
    *    <li class='extlink'>{@doc ExtJsonSchemaValidation}
    * </ul>
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items setExclusiveMaximum(Boolean value) {
      exclusiveMaximum = value;
      return this;
   }

   /**
    * Same as {@link #setExclusiveMaximum(Boolean)}.
    *
    * @param value
    *    The new value for this property.
    *    <br>Non-boolean values will be converted to boolean using <code>Boolean.<jsm>valueOf</jsm>(value.toString())</code>.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items exclusiveMaximum(Object value) {
      return setExclusiveMaximum(toBoolean(value));
   }

   /**
    * Bean property getter:  <property>minimum</property>.
    *
    * <ul class='seealso'>
    *    <li class='extlink'>{@doc ExtJsonSchemaValidation}
    * </ul>
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public Number getMinimum() {
      return minimum;
   }

   /**
    * Bean property setter:  <property>minimum</property>.
    *
    * <ul class='seealso'>
    *    <li class='extlink'>{@doc ExtJsonSchemaValidation}
    * </ul>
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items setMinimum(Number value) {
      minimum = value;
      return this;
   }

   /**
    * Same as {@link #setMinimum(Number)}.
    *
    * @param value
    *    The new value for this property.
    *    <br>Non-Number values will be converted to Number using <c>toString()</c> then best number match.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items minimum(Object value) {
      return setMinimum(toNumber(value));
   }

   /**
    * Bean property getter:  <property>exclusiveMinimum</property>.
    *
    * <ul class='seealso'>
    *    <li class='extlink'>{@doc ExtJsonSchemaValidation}
    * </ul>
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public Boolean getExclusiveMinimum() {
      return exclusiveMinimum;
   }

   /**
    * Bean property setter:  <property>exclusiveMinimum</property>.
    *
    * <ul class='seealso'>
    *    <li class='extlink'>{@doc ExtJsonSchemaValidation}
    * </ul>
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items setExclusiveMinimum(Boolean value) {
      exclusiveMinimum = value;
      return this;
   }

   /**
    * Same as {@link #setExclusiveMinimum(Boolean)}.
    *
    * @param value
    *    The new value for this property.
    *    <br>Non-boolean values will be converted to boolean using <code>Boolean.<jsm>valueOf</jsm>(value.toString())</code>.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items exclusiveMinimum(Object value) {
      return setExclusiveMinimum(toBoolean(value));
   }

   /**
    * Bean property getter:  <property>maxLength</property>.
    *
    * <ul class='seealso'>
    *    <li class='extlink'>{@doc ExtJsonSchemaValidation}
    * </ul>
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public Integer getMaxLength() {
      return maxLength;
   }

   /**
    * Bean property setter:  <property>maxLength</property>.
    *
    * <ul class='seealso'>
    *    <li class='extlink'>{@doc ExtJsonSchemaValidation}
    * </ul>
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items setMaxLength(Integer value) {
      maxLength = value;
      return this;
   }

   /**
    * Same as {@link #setMaxLength(Integer)}.
    *
    * @param value
    *    The new value for this property.
    *    <br>Non-Integer values will be converted to Integer using <code>Integer.<jsm>valueOf</jsm>(value.toString())</code>.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items maxLength(Object value) {
      return setMaxLength(toInteger(value));
   }

   /**
    * Bean property getter:  <property>minLength</property>.
    *
    * <ul class='seealso'>
    *    <li class='extlink'>{@doc ExtJsonSchemaValidation}
    * </ul>
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public Integer getMinLength() {
      return minLength;
   }

   /**
    * Bean property setter:  <property>minLength</property>.
    *
    * <ul class='seealso'>
    *    <li class='extlink'>{@doc ExtJsonSchemaValidation}
    * </ul>
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items setMinLength(Integer value) {
      minLength = value;
      return this;
   }

   /**
    * Same as {@link #setMinLength(Integer)}.
    *
    * @param value
    *    The new value for this property.
    *    <br>Non-Integer values will be converted to Integer using <code>Integer.<jsm>valueOf</jsm>(value.toString())</code>.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items minLength(Object value) {
      return setMinLength(toInteger(value));
   }

   /**
    * Bean property getter:  <property>pattern</property>.
    *
    * <ul class='seealso'>
    *    <li class='extlink'>{@doc ExtJsonSchemaValidation}
    * </ul>
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public String getPattern() {
      return pattern;
   }

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

   /**
    * Same as {@link #setPattern(String)}.
    *
    * @param value
    *    The new value for this property.
    *    <br>Non-String values will be converted to String using <c>toString()</c>.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items pattern(Object value) {
      return setPattern(stringify(value));
   }

   /**
    * Bean property getter:  <property>maxItems</property>.
    *
    * <ul class='seealso'>
    *    <li class='extlink'>{@doc ExtJsonSchemaValidation}
    * </ul>
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public Integer getMaxItems() {
      return maxItems;
   }

   /**
    * Bean property setter:  <property>maxItems</property>.
    *
    * <ul class='seealso'>
    *    <li class='extlink'>{@doc ExtJsonSchemaValidation}
    * </ul>
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items setMaxItems(Integer value) {
      maxItems = value;
      return this;
   }

   /**
    * Same as {@link #setMaxItems(Integer)}.
    *
    * @param value
    *    The new value for this property.
    *    <br>Non-Integer values will be converted to Integer using <code>Integer.<jsm>valueOf</jsm>(value.toString())</code>.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items maxItems(Object value) {
      return setMaxItems(toInteger(value));
   }

   /**
    * Bean property getter:  <property>minItems</property>.
    *
    * <ul class='seealso'>
    *    <li class='extlink'>{@doc ExtJsonSchemaValidation}
    * </ul>
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public Integer getMinItems() {
      return minItems;
   }

   /**
    * Bean property setter:  <property>minItems</property>.
    *
    * <ul class='seealso'>
    *    <li class='extlink'>{@doc ExtJsonSchemaValidation}
    * </ul>
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items setMinItems(Integer value) {
      minItems = value;
      return this;
   }

   /**
    * Same as {@link #setMinItems(Integer)}.
    *
    * @param value
    *    The new value for this property.
    *    <br>Non-Integer values will be converted to Integer using <code>Integer.<jsm>valueOf</jsm>(value.toString())</code>.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items minItems(Object value) {
      return setMinItems(toInteger(value));
   }

   /**
    * Bean property getter:  <property>uniqueItems</property>.
    *
    * <ul class='seealso'>
    *    <li class='extlink'>{@doc ExtJsonSchemaValidation}
    * </ul>
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public Boolean getUniqueItems() {
      return uniqueItems;
   }

   /**
    * Bean property setter:  <property>uniqueItems</property>.
    *
    * <ul class='seealso'>
    *    <li class='extlink'>{@doc ExtJsonSchemaValidation}
    * </ul>
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items setUniqueItems(Boolean value) {
      uniqueItems = value;
      return this;
   }

   /**
    * Same as {@link #setUniqueItems(Boolean)}.
    *
    * @param value
    *    The new value for this property.
    *    <br>Non-boolean values will be converted to boolean using <code>Boolean.<jsm>valueOf</jsm>(value.toString())</code>.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items uniqueItems(Object value) {
      return setUniqueItems(toBoolean(value));
   }

   /**
    * Bean property getter:  <property>enum</property>.
    *
    * <ul class='seealso'>
    *    <li class='extlink'>{@doc ExtJsonSchemaValidation}
    * </ul>
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public List<Object> getEnum() {
      return _enum;
   }

   /**
    * Bean property setter:  <property>enum</property>.
    *
    * <ul class='seealso'>
    *    <li class='extlink'>{@doc ExtJsonSchemaValidation}
    * </ul>
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items setEnum(Collection<Object> value) {
      _enum = newList(value);
      return this;
   }

   /**
    * 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 (for method chaining).
    */
   public Items addEnum(Collection<Object> values) {
      _enum = addToList(_enum, values);
      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><c>Object</c>
    *       <li><c>Collection&lt;Object&gt;</c>
    *       <li><c>String</c> - JSON array representation of <c>Collection&lt;Object&gt;</c>
    *          <p class='bcode w800'>
    *    <jc>// Example </jc>
    *    _enum(<js>"['foo','bar']"</js>);
    *          </p>
    *       <li><c>String</c> - Individual values
    *          <p class='bcode w800'>
    *    <jc>// Example </jc>
    *    _enum(<js>"foo"</js>, <js>"bar"</js>);
    *          </p>
    *    </ul>
    *    <br>Ignored if <jk>null</jk>.
    * @return This object (for method chaining).
    */
   public Items _enum(Object...values) {
      _enum = addToList(_enum, values, Object.class);
      return this;
   }

   /**
    * Bean property getter:  <property>multipleOf</property>.
    *
    * <ul class='seealso'>
    *    <li class='extlink'>{@doc ExtJsonSchemaValidation}
    * </ul>
    *
    * @return The property value, or <jk>null</jk> if it is not set.
    */
   public Number getMultipleOf() {
      return multipleOf;
   }

   /**
    * Bean property setter:  <property>multipleOf</property>.
    *
    * <ul class='seealso'>
    *    <li class='extlink'>{@doc ExtJsonSchemaValidation}
    * </ul>
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items setMultipleOf(Number value) {
      multipleOf = value;
      return this;
   }

   /**
    * Same as {@link #setMultipleOf(Number)}.
    *
    * @param value
    *    The new value for this property.
    *    <br>Non-Number values will be converted to Number using <c>toString()</c> then best number match.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items multipleOf(Object value) {
      return setMultipleOf(toNumber(value));
   }

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

   /**
    * Returns <jk>true</jk> if this object has a <js>"$ref"</js> attribute.
    *
    * @return <jk>true</jk> if this object has a <js>"$ref"</js> attribute.
    */
   public boolean hasRef() {
      return ref != null;
   }

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

   /**
    * Same as {@link #setRef(Object)}.
    *
    * @param value
    *    The new value for this property.
    *    <br>Can be <jk>null</jk> to unset the property.
    * @return This object (for method chaining).
    */
   public Items ref(Object value) {
      return setRef(value);
   }

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

   @Override /* SwaggerElement */
   public Items set(String property, Object value) {
      if (property == null)
         return this;
      switch (property) {
         case "type": return type(value);
         case "format": return format(value);
         case "items": return items(value);
         case "collectionFormat": return collectionFormat(value);
         case "default": return _default(value);
         case "maximum": return maximum(value);
         case "exclusiveMaximum": return exclusiveMaximum(value);
         case "minimum": return minimum(value);
         case "exclusiveMinimum": return exclusiveMinimum(value);
         case "maxLength": return maxLength(value);
         case "minLength": return minLength(value);
         case "pattern": return pattern(value);
         case "maxItems": return maxItems(value);
         case "minItems": return minItems(value);
         case "uniqueItems": return uniqueItems(value);
         case "enum": return setEnum(null)._enum(value);
         case "multipleOf": return multipleOf(value);
         case "$ref": return ref(value);
         default:
            super.set(property, value);
            return this;
      }
   }

   @Override /* SwaggerElement */
   public Set<String> keySet() {
      ASet<String> s = ASet.<String>of()
         .aif(type != null, "type")
         .aif(format != null, "format")
         .aif(items != null, "items")
         .aif(collectionFormat != null, "collectionFormat")
         .aif(_default != null, "default")
         .aif(maximum != null, "maximum")
         .aif(exclusiveMaximum != null, "exclusiveMaximum")
         .aif(minimum != null, "minimum")
         .aif(exclusiveMinimum != null, "exclusiveMinimum")
         .aif(maxLength != null, "maxLength")
         .aif(minLength != null, "minLength")
         .aif(pattern != null, "pattern")
         .aif(maxItems != null, "maxItems")
         .aif(minItems != null, "minItems")
         .aif(uniqueItems != null, "uniqueItems")
         .aif(_enum != null, "enum")
         .aif(multipleOf != null, "multipleOf")
         .aif(ref != null, "$ref");
      return new MultiSet<>(s, super.keySet());
   }

   /**
    * Resolves any <js>"$ref"</js> attributes in this element.
    *
    * @param swagger The swagger document containing the definitions.
    * @param refStack Keeps track of previously-visited references so that we don't cause recursive loops.
    * @param maxDepth
    *    The maximum depth to resolve references.
    *    <br>After that level is reached, <c>$ref</c> 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(Swagger swagger, Deque<String> refStack, int maxDepth) {

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

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

      if (items != null)
         items = items.resolveRefs(swagger, refStack, maxDepth);

      set("example", null);

      return this;
   }

   /* Resolve references in extra attributes */
   private Object resolveRefs(Object o, Swagger swagger, Deque<String> refStack, int maxDepth) {
      if (o instanceof OMap) {
         OMap om = (OMap)o;
         Object ref = om.get("$ref");
         if (ref instanceof CharSequence) {
            String sref = ref.toString();
            if (refStack.contains(sref) || refStack.size() >= maxDepth)
               return o;
            refStack.addLast(sref);
            Object o2 = swagger.findRef(sref, Object.class);
            o2 = resolveRefs(o2, swagger, refStack, maxDepth);
            refStack.removeLast();
            return o2;
         }
         for (Map.Entry<String,Object> e : om.entrySet())
            e.setValue(resolveRefs(e.getValue(), swagger, refStack, maxDepth));
      }
      if (o instanceof OList)
         for (ListIterator<Object> li = ((OList)o).listIterator(); li.hasNext();)
            li.set(resolveRefs(li.next(), swagger, refStack, maxDepth));
      return o;
   }
}