/*
 * 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.cp;

import static org.apache.juneau.commons.utils.CollectionUtils.*;
import static org.apache.juneau.commons.utils.ResourceBundleUtils.*;
import static org.apache.juneau.commons.utils.StringUtils.*;
import static org.apache.juneau.commons.utils.ThrowableUtils.*;
import static org.apache.juneau.commons.utils.Utils.*;

import java.text.*;
import java.util.*;
import java.util.concurrent.*;

import org.apache.juneau.*;
import org.apache.juneau.collections.*;
import org.apache.juneau.commons.collections.*;
import org.apache.juneau.commons.function.*;
import org.apache.juneau.commons.utils.*;
import org.apache.juneau.marshaller.*;
import org.apache.juneau.parser.ParseException;

/**
 * An enhanced {@link ResourceBundle}.
 *
 * <p>
 * Wraps a ResourceBundle to provide some useful additional functionality.
 *
 * <ul>
 *    <li>
 *       Instead of throwing {@link MissingResourceException}, the {@link ResourceBundle#getString(String)} method
 *       will return <js>"{!key}"</js> if the message could not be found.
 *    <li>
 *       Supported hierarchical lookup of resources from parent parent classes.
 *    <li>
 *       Support for easy retrieval of localized bundles.
 *    <li>
 *       Support for generalized resource bundles (e.g. properties files containing keys for several classes).
 * </ul>
 *
 * <p>
 * The following example shows the basic usage of this class for retrieving localized messages:
 *
 * <p class='bini'>
 *    <cc># Contents of MyClass.properties</cc>
 *    <ck>foo</ck> = <cv>foo {0}</cv>
 *    <ck>MyClass.bar</ck> = <cv>bar {0}</cv>
 * </p>
 * <p class='bjava'>
 *    <jk>public class</jk> MyClass {
 *       <jk>private static final</jk> Messages <jsf>MESSAGES</jsf> = Messages.<jsm>of</jsm>(MyClass.<jk>class</jk>);
 *
 *       <jk>public void</jk> doFoo() {
 *
 *       <jc>// A normal property.</jc>
 *          String <jv>foo</jv> = <jsf>MESSAGES</jsf>.getString(<js>"foo"</js>,<js>"x"</js>);  <jc>// == "foo x"</jc>
 *
 *          <jc>// A property prefixed by class name.</jc>
 *          String <jv>bar</jv> = <jsf>MESSAGES</jsf>.getString(<js>"bar"</js>,<js>"x"</js>);  <jc>// == "bar x"</jc>
 *
 *          <jc>// A non-existent property.</jc>
 *          String <jv>baz</jv> = <jsf>MESSAGES</jsf>.getString(<js>"baz"</js>,<js>"x"</js>);  <jc>// == "{!baz}"</jc>
 *       }
 *    }
 * </p>
 *
 * <p>
 *    The ability to resolve keys prefixed by class name allows you to place all your messages in a single file such
 *    as a common <js>"Messages.properties"</js> file along with those for other classes.
 * <p>
 *    The following shows how to retrieve messages from a common bundle:
 *
 * <p class='bjava'>
 *    <jk>public class</jk> MyClass {
 *       <jk>private static final</jk> Messages <jsf>MESSAGES</jsf> = Messages.<jsm>of</jsm>(MyClass.<jk>class</jk>, <js>"Messages"</js>);
 *    }
 * </p>
 *
 * <p>
 *    Resource bundles are searched using the following base name patterns:
 *    <ul>
 *       <li><js>"{package}.{name}"</js>
 *       <li><js>"{package}.i18n.{name}"</js>
 *       <li><js>"{package}.nls.{name}"</js>
 *       <li><js>"{package}.messages.{name}"</js>
 *    </ul>
 *
 * <p>
 *    These patterns can be customized using the {@link Builder#baseNames(String...)} method.
 *
 * <p>
 *    Localized messages can be retrieved in the following way:
 *
 * <p class='bjava'>
 *    <jc>// Return value from Japan locale bundle.</jc>
 *    String <jv>foo</jv> = <jsf>MESSAGES</jsf>.forLocale(Locale.<jsf>JAPAN</jsf>).getString(<js>"foo"</js>);
 * </p>
 *
 */
public class Messages extends ResourceBundle {
   /**
    * Builder class.
    */
   public static class Builder extends BeanBuilder<Messages> {

      private static class MessagesString {
         public String name;
         public String[] baseNames;
         public String locale;
      }

      Class<?> forClass;
      Locale locale;
      String name;
      Messages parent;

      List<Tuple2<Class<?>,String>> locations;

      private String[] baseNames = { "{package}.{name}", "{package}.i18n.{name}", "{package}.nls.{name}", "{package}.messages.{name}" };

      /**
       * Constructor.
       *
       * @param forClass The base class.
       */
      protected Builder(Class<?> forClass) {
         super(Messages.class, BeanStore.INSTANCE);
         this.forClass = forClass;
         this.name = cns(forClass);
         locations = list();
         locale = Locale.getDefault();
      }

      /**
       * Specifies the base name patterns to use for finding the resource bundle.
       *
       * @param baseNames
       *    The bundle base names.
       *    <br>The default is the following:
       *    <ul>
       *       <li><js>"{package}.{name}"</js>
       *       <li><js>"{package}.i18n.{name}"</js>
       *       <li><js>"{package}.nls.{name}"</js>
       *       <li><js>"{package}.messages.{name}"</js>
       *    </ul>
       * @return This object.
       */
      public Builder baseNames(String...baseNames) {
         this.baseNames = baseNames == null ? a() : baseNames;
         return this;
      }

      @Override /* Overridden from BeanBuilder */
      public Builder impl(Object value) {
         super.impl(value);
         return this;
      }

      /**
       * Specifies the locale.
       *
       * @param value
       *    The locale.
       *    If <jk>null</jk>, the default locale is used.
       * @return This object.
       */
      public Builder locale(Locale value) {
         this.locale = value == null ? Locale.getDefault() : value;
         return this;
      }

      /**
       * Specifies the locale.
       *
       * @param value
       *    The locale.
       *    If <jk>null</jk>, the default locale is used.
       * @return This object.
       */
      public Builder locale(String value) {
         return locale(value == null ? null : Locale.forLanguageTag(value));
      }

      /**
       * Specifies a location of where to look for messages.
       *
       * @param baseClass The base class.
       * @param bundlePath The bundle path.
       * @return This object.
       */
      public Builder location(Class<?> baseClass, String bundlePath) {
         this.locations.add(0, Tuple2.of(baseClass, bundlePath));
         return this;
      }

      /**
       * Specifies a location of where to look for messages.
       *
       * @param bundlePath The bundle path.
       * @return This object.
       */
      public Builder location(String bundlePath) {
         this.locations.add(0, Tuple2.of(forClass, bundlePath));
         return this;
      }

      /**
       * Specifies the bundle name (e.g. <js>"Messages"</js>).
       *
       * @param value
       *    The bundle name.
       *    <br>If <jk>null</jk>, the forClass class name is used.
       * @return This object.
       */
      public Builder name(String value) {
         this.name = isEmpty(value) ? cns(forClass) : value;
         return this;
      }

      /**
       * Adds a parent bundle.
       *
       * @param value The parent bundle.  Can be <jk>null</jk>.
       * @return This object.
       */
      public Builder parent(Messages value) {
         parent = value;
         return this;
      }

      @Override /* Overridden from BeanBuilder */
      public Builder type(Class<?> value) {
         super.type(value);
         return this;
      }

      @SuppressWarnings("unchecked")
      @Override /* Overridden from BeanBuilder */
      protected Messages buildDefault() {

         if (! locations.isEmpty()) {
            Tuple2<Class<?>,String>[] mbl = locations.toArray(new Tuple2[0]);

            var x = (Builder)null;

            for (var i = mbl.length - 1; i >= 0; i--) {
               var c = firstNonNull(mbl[i].getA(), forClass);
               var value = mbl[i].getB();
               if (isProbablyJsonObject(value, true)) {
                  MessagesString ms;
                  try {
                     ms = Json5.DEFAULT.read(value, MessagesString.class);
                  } catch (ParseException e) {
                     throw toRex(e);
                  }
                  x = Messages.create(c).name(ms.name).baseNames(StringUtils.splita(ms.baseNames, ',')).locale(ms.locale).parent(x == null ? null : x.build());
               } else {
                  x = Messages.create(c).name(value).parent(x == null ? null : x.build());
               }
            }

            return x == null ? null : x.build();  // Shouldn't be null.
         }

         return new Messages(this);
      }

      ResourceBundle getBundle() {
         var cl = forClass.getClassLoader();
         var m = JsonMap.of("name", name, "package", forClass.getPackage().getName());
         for (var bn : baseNames) {
            bn = StringUtils.formatNamed(bn, m);
            var rb = findBundle(bn, locale, cl);
            if (nn(rb))
               return rb;
         }
         return null;
      }
   }

   /**
    * Static creator.
    *
    * @param forClass
    *    The class we're creating this object for.
    * @return A new builder.
    */
   public static final Builder create(Class<?> forClass) {
      return new Builder(forClass);
   }

   /**
    * Constructor.
    *
    * @param forClass
    *    The class we're creating this object for.
    * @return A new message bundle belonging to the class.
    */
   public static final Messages of(Class<?> forClass) {
      return create(forClass).build();
   }

   /**
    * Constructor.
    *
    * @param forClass
    *    The class we're creating this object for.
    * @param name
    *    The bundle name (e.g. <js>"Messages"</js>).
    *    <br>If <jk>null</jk>, uses the class name.
    * @return A new message bundle belonging to the class.
    */
   public static final Messages of(Class<?> forClass, String name) {
      return create(forClass).name(name).build();
   }

   private ResourceBundle rb;
   private Class<?> c;
   private Messages parent;
   private Locale locale;

   // Cache of message bundles per locale.
   private final ConcurrentHashMap<Locale,Messages> localizedMessages = new ConcurrentHashMap<>();

   // Cache of virtual keys to actual keys.
   private final Map<String,String> keyMap;

   private final Set<String> rbKeys;

   /**
    * Constructor.
    *
    * @param builder
    *    The builder for this object.
    */
   protected Messages(Builder builder) {
      this(builder.forClass, builder.getBundle(), builder.locale, builder.parent);
   }

   Messages(Class<?> forClass, ResourceBundle rb, Locale locale, Messages parent) {
      this.c = forClass;
      this.rb = rb;
      this.parent = parent;
      if (nn(parent))
         setParent(parent);
      this.locale = locale == null ? Locale.getDefault() : locale;

      var keyMap = new TreeMap<String,String>();

      var cn = cns(c) + '.';
      if (nn(rb)) {
         rb.keySet().forEach(x -> {
            keyMap.put(x, x);
            if (x.startsWith(cn)) {
               var shortKey = x.substring(cn.length());
               keyMap.put(shortKey, x);
            }
         });
      }
      if (nn(parent)) {
         parent.keySet().forEach(x -> {
            keyMap.put(x, x);
            if (x.startsWith(cn)) {
               var shortKey = x.substring(cn.length());
               keyMap.put(shortKey, x);
            }
         });
      }

      this.keyMap = u(copyOf(keyMap));
      this.rbKeys = rb == null ? Collections.emptySet() : rb.keySet();
   }

   @Override /* Overridden from ResourceBundle */
   public boolean containsKey(String key) {
      return keyMap.containsKey(key);
   }

   /**
    * Looks for all the specified keys in the resource bundle and returns the first value that exists.
    *
    * @param keys The list of possible keys.
    * @return The resolved value, or <jk>null</jk> if no value is found or the resource bundle is missing.
    */
   public String findFirstString(String...keys) {
      for (var k : keys) {
         if (containsKey(k))
            return getString(k);
      }
      return null;
   }

   /**
    * Returns this message bundle for the specified locale.
    *
    * @param locale The locale to get the messages for.
    * @return A new {@link Messages} object.  Never <jk>null</jk>.
    */
   public Messages forLocale(Locale locale) {
      if (locale == null)
         locale = Locale.getDefault();
      if (this.locale.equals(locale))
         return this;
      var mb = localizedMessages.get(locale);
      if (mb == null) {
         var parent = this.parent == null ? null : this.parent.forLocale(locale);
         var rb = this.rb == null ? null : findBundle(this.rb.getBaseBundleName(), locale, c.getClassLoader());
         mb = new Messages(c, rb, locale, parent);
         localizedMessages.put(locale, mb);
      }
      return mb;
   }

   @Override /* Overridden from ResourceBundle */
   public Enumeration<String> getKeys() { return Collections.enumeration(keySet()); }

   /**
    * Similar to {@link ResourceBundle#getString(String)} except allows you to pass in {@link MessageFormat} objects.
    *
    * @param key The resource bundle key.
    * @param args Optional {@link MessageFormat}-style arguments.
    * @return
    *    The resolved value.  Never <jk>null</jk>.
    *    <js>"{!key}"</js> if the key is missing.
    */
   public String getString(String key, Object...args) {
      var s = getString(key);
      if (s.startsWith("{!"))
         return s;
      return f(s, args);
   }

   @Override /* Overridden from ResourceBundle */
   public Set<String> keySet() {
      return keyMap.keySet();
   }

   /**
    * Returns all keys in this resource bundle with the specified prefix.
    *
    * <p>
    * Keys are returned in alphabetical order.
    *
    * @param prefix The prefix.
    * @return The set of all keys in the resource bundle with the prefix.
    */
   public Set<String> keySet(String prefix) {
      Set<String> set = set();
      keySet().forEach(x -> {
         if (x.equals(prefix) || (x.startsWith(prefix) && x.charAt(prefix.length()) == '.'))
            set.add(x);
      });
      return set;
   }

   protected FluentMap<String,Object> properties() {
      // @formatter:off
      var m = filteredBeanPropertyMap();
      keySet().stream().forEach(x -> m.a(x, getString(x)));
      return m;
      // @formatter:on
   }

   @Override /* Overridden from Object */
   public String toString() {
      return r(properties());
   }

   @Override /* Overridden from ResourceBundle */
   protected Object handleGetObject(String key) {
      var k = keyMap.get(key);
      if (k == null)
         return "{!" + key + "}";
      try {
         if (rbKeys.contains(k))
            return rb.getObject(k);
      } catch (@SuppressWarnings("unused") MissingResourceException e) { /* Shouldn't happen */ }
      return parent.handleGetObject(key);
   }
}