/*
 * 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.config;

import java.beans.*;
import java.lang.reflect.*;
import java.util.*;

import org.apache.juneau.collections.*;
import org.apache.juneau.common.utils.*;
import org.apache.juneau.config.internal.*;
import org.apache.juneau.parser.*;

/**
 * A single section in a config file.
 */
public class Section {

   final Config config;
   private final ConfigMap configMap;
   final String name;

   /**
    * Constructor.
    *
    * @param config The config that this entry belongs to.
    * @param configMap The map that this belongs to.
    * @param name The section name of this entry.
    */
   protected Section(Config config, ConfigMap configMap, String name) {
      this.config = config;
      this.configMap = configMap;
      this.name = name;
   }

   /**
    * Returns <jk>true</jk> if this section exists.
    *
    * @return <jk>true</jk> if this section exists.
    */
   public boolean isPresent() {
      return configMap.hasSection(name);
   }

   /**
    * Shortcut for calling <code>asBean(sectionName, c, <jk>false</jk>)</code>.
    *
    * @param <T> The bean class to create.
    * @param c The bean class to create.
    * @return A new bean instance, or {@link Optional#empty()} if this section does not exist.
    * @throws ParseException Malformed input encountered.
    */
   public <T> Optional<T> asBean(Class<T> c) throws ParseException {
      return asBean(c, false);
   }

   /**
    * Converts this config file section to the specified bean instance.
    *
    * <p>
    * Key/value pairs in the config file section get copied as bean property values to the specified bean class.
    *
    * <h5 class='figure'>Example config file</h5>
    * <p class='bini'>
    *    <cs>[MyAddress]</cs>
    *    <ck>name</ck> = <cv>John Smith</cv>
    *    <ck>street</ck> = <cv>123 Main Street</cv>
    *    <ck>city</ck> = <cv>Anywhere</cv>
    *    <ck>state</ck> = <cv>NY</cv>
    *    <ck>zip</ck> = <cv>12345</cv>
    * </p>
    *
    * <h5 class='figure'>Example bean</h5>
    * <p class='bjava'>
    *    <jk>public class</jk> Address {
    *       <jk>public</jk> String <jf>name</jf>, <jf>street</jf>, <jf>city</jf>;
    *       <jk>public</jk> StateEnum <jf>state</jf>;
    *       <jk>public int</jk> <jf>zip</jf>;
    *    }
    * </p>
    *
    * <h5 class='figure'>Example usage</h5>
    * <p class='bjava'>
    *    Config <jv>config</jv> = Config.<jsm>create</jsm>().name(<js>"MyConfig.cfg"</js>).build();
    *    Address <jv>address</jv> = <jv>config</jv>.getSection(<js>"MySection"</js>).asBean(Address.<jk>class</jk>).orElse(<jk>null</jk>);
    * </p>
    *
    * @param <T> The bean class to create.
    * @param c The bean class to create.
    * @param ignoreUnknownProperties
    *    If <jk>false</jk>, throws a {@link ParseException} if the section contains an entry that isn't a bean property
    *    name.
    * @return A new bean instance, or <jk>null</jk> if this section doesn't exist.
    * @throws ParseException Unknown property was encountered in section.
    */
   public <T> Optional<T> asBean(Class<T> c, boolean ignoreUnknownProperties) throws ParseException {
      Utils.assertArgNotNull("c", c);

      if (! isPresent())
         return Utils.opte();

      var keys = configMap.getKeys(name);

      var bm = config.beanSession.newBeanMap(c);
      for (var k : keys) {
         var bpm = bm.getPropertyMeta(k);
         if (bpm == null) {
            if (! ignoreUnknownProperties)
               throw new ParseException("Unknown property ''{0}'' encountered in configuration section ''{1}''.", k, name);
         } else {
            bm.put(k, config.get(name + '/' + k).as(bpm.getClassMeta().getInnerClass()).orElse(null));
         }
      }

      return Utils.opt(bm.getBean());
   }

   /**
    * Returns this section as a map.
    *
    * @return A new {@link JsonMap}, or {@link Optional#empty()} if this section doesn't exist.
    */
   public Optional<JsonMap> asMap() {
      if (! isPresent())
         return Utils.opte();

      var keys = configMap.getKeys(name);

      var m = new JsonMap();
      for (var k : keys)
         m.put(k, config.get(name + '/' + k).as(Object.class).orElse(null));
      return Utils.opt(m);
   }

   /**
    * Wraps this section inside a Java interface so that values in the section can be read and
    * write using getters and setters.
    *
    * <h5 class='figure'>Example config file</h5>
    * <p class='bini'>
    *    <cs>[MySection]</cs>
    *    <ck>string</ck> = <cv>foo</cv>
    *    <ck>int</ck> = <cv>123</cv>
    *    <ck>enum</ck> = <cv>ONE</cv>
    *    <ck>bean</ck> = <cv>{foo:'bar',baz:123}</cv>
    *    <ck>int3dArray</ck> = <cv>[[[123,null],null],null]</cv>
    *    <ck>bean1d3dListMap</ck> = <cv>{key:[[[[{foo:'bar',baz:123}]]]]}</cv>
    * </p>
    *
    * <h5 class='figure'>Example interface</h5>
    * <p class='bjava'>
    *    <jk>public interface</jk> MyConfigInterface {
    *
    *       String getString();
    *       <jk>void</jk> setString(String <jv>value</jv>);
    *
    *       <jk>int</jk> getInt();
    *       <jk>void</jk> setInt(<jk>int</jk> <jv>value</jv>);
    *
    *       MyEnum getEnum();
    *       <jk>void</jk> setEnum(MyEnum <jv>value</jv>);
    *
    *       MyBean getBean();
    *       <jk>void</jk> setBean(MyBean <jv>value</jv>);
    *
    *       <jk>int</jk>[][][] getInt3dArray();
    *       <jk>void</jk> setInt3dArray(<jk>int</jk>[][][] <jv>value</jv>);
    *
    *       Map&lt;String,List&lt;MyBean[][][]&gt;&gt; getBean1d3dListMap();
    *       <jk>void</jk> setBean1d3dListMap(Map&lt;String,List&lt;MyBean[][][]&gt;&gt; <jv>value</jv>);
    *    }
    * </p>
    *
    * <h5 class='figure'>Example usage</h5>
    * <p class='bjava'>
    *    Config <jv>config</jv> = Config.<jsm>create</jsm>().name(<js>"MyConfig.cfg"</js>).build();
    *
    *    MyConfigInterface <jv>ci</jv> = <jv>config</jv>.get(<js>"MySection"</js>).asInterface(MyConfigInterface.<jk>class</jk>).orElse(<jk>null</jk>);
    *
    *    <jk>int</jk> <jv>myInt</jv> = <jv>ci</jv>.getInt();
    *
    *    <jv>ci</jv>.setBean(<jk>new</jk> MyBean());
    *
    *    <jv>ci</jv>.save();
    * </p>
    *
    * <h5 class='section'>Notes:</h5><ul>
    *    <li class='note'>Calls to setters when the configuration is read-only will cause {@link UnsupportedOperationException} to be thrown.
    * </ul>
    *
    * @param <T> The proxy interface class.
    * @param c The proxy interface class.
    * @return The proxy interface.
    */
   @SuppressWarnings("unchecked")
   public <T> Optional<T> asInterface(final Class<T> c) {
      Utils.assertArgNotNull("c", c);

      if (!c.isInterface())
         throw new IllegalArgumentException("Class '" + c.getName() + "' passed to toInterface() is not an interface.");

      return Utils.opt((T) Proxy.newProxyInstance(c.getClassLoader(), new Class[] { c }, (InvocationHandler) (proxy, method, args) -> {
         var bi = Introspector.getBeanInfo(c, null);
         for (var pd : bi.getPropertyDescriptors()) {
            var rm = pd.getReadMethod();
            var wm = pd.getWriteMethod();
            if (method.equals(rm))
               return config.get(name + '/' + pd.getName()).as(rm.getGenericReturnType()).orElse(null);
            if (method.equals(wm))
               return config.set(name + '/' + pd.getName(), args[0]);
         }
         throw new UnsupportedOperationException("Unsupported interface method.  method='" + method + "'");
      }));
   }

   /**
    * Copies the entries in this section to the specified bean by calling the public setters on that bean.
    *
    * @param bean The bean to set the properties on.
    * @param ignoreUnknownProperties
    *    If <jk>true</jk>, don't throw an {@link IllegalArgumentException} if this section contains a key that doesn't
    *    correspond to a setter method.
    * @return An object map of the changes made to the bean.
    * @throws ParseException If parser was not set on this config file or invalid properties were found in the section.
    * @throws UnsupportedOperationException If configuration is read only.
    */
   public Section writeToBean(Object bean, boolean ignoreUnknownProperties) throws ParseException {
      Utils.assertArgNotNull("bean", bean);
      if (! isPresent()) throw new IllegalArgumentException("Section '"+name+"' not found in configuration.");

      var keys = configMap.getKeys(name);

      var bm = config.beanSession.toBeanMap(bean);
      for (var k : keys) {
         var bpm = bm.getPropertyMeta(k);
         if (bpm == null) {
            if (! ignoreUnknownProperties)
               throw new ParseException("Unknown property ''{0}'' encountered in configuration section ''{1}''.", k, name);
         } else {
            bm.put(k, config.get(name + '/' + k).as(bpm.getClassMeta().getInnerClass()).orElse(null));
         }
      }

      return this;
   }
}