/*
 * 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.annotation;

import static java.lang.annotation.ElementType.*;
import static java.lang.annotation.RetentionPolicy.*;

import java.lang.annotation.*;

/**
 * Identifies examples for POJOs.
 *
 * <p>
 * Can be used in the following locations:
 * <ul>
 *    <li>Static method that returns an example of the POJO.
 *    <li>Static field that contains an example of the POJO.
 *    <li>On a class.
 *    <li><ja>@Rest</ja>-annotated classes and <ja>@RestOp</ja>-annotated methods when an {@link #on()} value is specified.
 * </ul>
 *
 * <h5 class='figure'>Examples:</h5>
 * <p class='bjava'>
 *    <jc>// On a static method.</jc>
 *    <jk>public class</jk> A {
 *
 *       <ja>@Example</ja>
 *       <jk>public static</jk> A example() {
 *          <jk>return new</jk> A().foo(<js>"bar"</js>).baz(123);
 *       }
 *
 *       ...
 *    }
 *
 *    <jc>// On a static field.</jc>
 *    <jk>public class</jk> B {
 *
 *       <ja>@Example</ja>
 *       <jk>public static</jk> B EXAMPLE = <jk>new</jk> B().foo(<js>"bar"</js>).baz(123);
 *
 *       ...
 *    }
 *
 *    <jc>// On a class.</jc>
 *    <ja>@Example</ja>(<js>"{foo:'bar',baz:123}"</js>)
 *    <jk>public class</jk> C {...}
 * </p>
 *
 */
@Documented
@Target({ FIELD, METHOD, TYPE })
@Retention(RUNTIME)
@Inherited
@Repeatable(ExampleAnnotation.Array.class)
@ContextApply(ExampleAnnotation.Applier.class)
public @interface Example {

   /**
    * Optional description for the exposed API.
    *
    * @return The annotation value.
    * @since 9.2.0
    */
   String[] description() default {};

   /**
    * Dynamically apply this annotation to the specified classes/methods/fields.
    *
    * <p>
    * Used in conjunction with {@link org.apache.juneau.BeanContext.Builder#applyAnnotations(Class...)} to dynamically apply an annotation to an existing class/method/field.
    * It is ignored when the annotation is applied directly to classes/methods/fields.
    *
    * <h5 class='section'>Valid patterns:</h5>
    * <ul class='spaced-list'>
    *  <li>Classes:
    *       <ul>
    *          <li>Fully qualified:
    *             <ul>
    *                <li><js>"com.foo.MyClass"</js>
    *             </ul>
    *          <li>Fully qualified inner class:
    *             <ul>
    *                <li><js>"com.foo.MyClass$Inner1$Inner2"</js>
    *             </ul>
    *          <li>Simple:
    *             <ul>
    *                <li><js>"MyClass"</js>
    *             </ul>
    *          <li>Simple inner:
    *             <ul>
    *                <li><js>"MyClass$Inner1$Inner2"</js>
    *                <li><js>"Inner1$Inner2"</js>
    *                <li><js>"Inner2"</js>
    *             </ul>
    *       </ul>
    *    <li>Methods:
    *       <ul>
    *          <li>Fully qualified with args:
    *             <ul>
    *                <li><js>"com.foo.MyClass.myMethod(String,int)"</js>
    *                <li><js>"com.foo.MyClass.myMethod(java.lang.String,int)"</js>
    *                <li><js>"com.foo.MyClass.myMethod()"</js>
    *             </ul>
    *          <li>Fully qualified:
    *             <ul>
    *                <li><js>"com.foo.MyClass.myMethod"</js>
    *             </ul>
    *          <li>Simple with args:
    *             <ul>
    *                <li><js>"MyClass.myMethod(String,int)"</js>
    *                <li><js>"MyClass.myMethod(java.lang.String,int)"</js>
    *                <li><js>"MyClass.myMethod()"</js>
    *             </ul>
    *          <li>Simple:
    *             <ul>
    *                <li><js>"MyClass.myMethod"</js>
    *             </ul>
    *          <li>Simple inner class:
    *             <ul>
    *                <li><js>"MyClass$Inner1$Inner2.myMethod"</js>
    *                <li><js>"Inner1$Inner2.myMethod"</js>
    *                <li><js>"Inner2.myMethod"</js>
    *             </ul>
    *       </ul>
    *    <li>Fields:
    *       <ul>
    *          <li>Fully qualified:
    *             <ul>
    *                <li><js>"com.foo.MyClass.myField"</js>
    *             </ul>
    *          <li>Simple:
    *             <ul>
    *                <li><js>"MyClass.myField"</js>
    *             </ul>
    *          <li>Simple inner class:
    *             <ul>
    *                <li><js>"MyClass$Inner1$Inner2.myField"</js>
    *                <li><js>"Inner1$Inner2.myField"</js>
    *                <li><js>"Inner2.myField"</js>
    *             </ul>
    *       </ul>
    *    <li>A comma-delimited list of anything on this list.
    * </ul>
    *
    * <h5 class='section'>See Also:</h5><ul>
    *    <li class='link'><a class="doclink" href="https://juneau.apache.org/docs/topics/DynamicallyAppliedAnnotations">Dynamically Applied Annotations</a>
    * </ul>
    *
    * @return The annotation value.
    */
   String[] on() default {};

   /**
    * Dynamically apply this annotation to the specified classes.
    *
    * <p>
    * Identical to {@link #on()} except allows you to specify class objects instead of a strings.
    *
    * <h5 class='section'>See Also:</h5><ul>
    *    <li class='link'><a class="doclink" href="https://juneau.apache.org/docs/topics/DynamicallyAppliedAnnotations">Dynamically Applied Annotations</a>
    * </ul>
    *
    * @return The annotation value.
    */
   Class<?>[] onClass() default {};

   /**
    * An example of a POJO class.
    *
    * <p>
    * Format is Lax-JSON.
    *
    * <p>
    * This value is only used when the annotation is used on a type.
    *
    * @return The annotation value.
    */
   String value() default "";
}