/*
 * 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.marshall.xml;

import static org.apache.juneau.commons.utils.Shorts.*;
import static org.apache.juneau.commons.utils.StringUtils.*;

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

import org.apache.juneau.marshall.*;

/**
 * Represents a simple namespace mapping between a simple name and URI.
 *
 * <p>
 * In general, the simple name will be used as the XML prefix mapping unless there are conflicts or prefix re-mappings
 * in the serializer.
 *
 * <h5 class='section'>See Also:</h5><ul>
 *    <li class='link'><a class="doclink" href="https://juneau.apache.org/docs/topics/XmlSupport">XML</a>
 * </ul>
 */
@SuppressWarnings({
   "java:S3740" // Raw Comparable type used intentionally for namespace ordering where the generic bound cannot be expressed
})
@Marshalled
public class Namespace {

   private static final ConcurrentHashMap<String,Namespace> CACHE = new ConcurrentHashMap<>();

   /**
    * Converts the specified object into a {@link Namespace} object.
    *
    * <p>
    * Can be any of following types:
    * <ul>
    *    <li>A {@link Namespace} object
    *    <li>A string containing a name/value pair of the form <js>"name:uri"</js>.
    * </ul>
    *
    * @param o The input.
    *    <br>Can be <jk>null</jk> (returns <jk>null</jk>).
    * @return The namespace object, or <jk>null</jk> if the input was <jk>null</jk>.
    */
   public static Namespace create(Object o) {
      if (o == null)
         return null;
      if (o instanceof Namespace o2)
         return o2;
      if (o instanceof CharSequence o3)
         return of(o3.toString());
      throw rex("Invalid object type passed to Namespace.create(Object):  '%s'", cn(o));
   }

   /**
    * Converts the specified object into an array of {@link Namespace} object.
    *
    * <p>
    * Can be any of following types:
    * <ul>
    *    <li>A {@link Namespace} array
    *    <li>A comma-delimited string with key/value pairs of the form <js>"name:uri"</js>.
    *    <li>A <c>Collection</c> containing any of object that can be passed to {@link #createArray(Object)}.
    * </ul>
    *
    * @param o The input.
    *    <br>Must not be <jk>null</jk>.
    * @return The namespace objects.
    */
   public static Namespace[] createArray(Object o) {

      if (o instanceof Namespace[] o2)
         return o2;

      if (o instanceof String[] o2) {
         var n = new Namespace[o2.length];
         for (var i = 0; i < o2.length; i++)
            n[i] = create(o2[i]);
         return n;
      }

      if (o instanceof CharSequence o2) {
         var ss = splita(o2.toString());
         var n = new Namespace[ss.length];
         for (var i = 0; i < ss.length; i++)
            n[i] = create(ss[i]);
         return n;
      }

      if (o instanceof Collection o2) {
         var n = new Namespace[o2.size()];
         var i = 0;
         for (var o3 : o2) {
            if (o3 instanceof Namespace o4)
               n[i++] = o4;
            else if (o3 instanceof CharSequence o4)
               n[i++] = create(o4.toString());
            else
               throw rex("Invalid type passed to NamespaceFactory.createArray: '%s'", cn(o));
         }
         return n;
      }

      throw rex("Invalid type passed to NamespaceFactory.createArray: '%s'", cn(o));
   }

   /**
    * Create a {@link Namespace} from a <js>"name:uri"</js> string pair.
    *
    * @param key The key/pair string.
    *    <br>Must not be <jk>null</jk>.
    * @return The namespace object.
    */
   public static Namespace of(String key) {
      var n = CACHE.get(key);
      if (nn(n))
         return n;
      var i = key.indexOf(':');
      if (i == -1)
         return of(key, null);
      if (key.startsWith("http://") || key.startsWith("https://"))
         return of(null, key);
      return of(key.substring(0, i).trim(), key.substring(i + 1).trim());
   }

   /**
    * Create a {@link Namespace} with the specified name and URI.
    *
    * <p>
    * Previously-encountered name/uri pairs return a cached copy.
    *
    * @param name The namespace name.  See {@link Namespace#getName()}.
    *    <br>Can be <jk>null</jk> (the namespace has no name).
    * @param uri The namespace URI.  See {@link Namespace#getUri()}.
    *    <br>Can be <jk>null</jk> (the namespace has no URI).
    * @return The namespace object.
    */
   public static Namespace of(String name, String uri) {
      var key = name + ":" + uri;
      var n = CACHE.get(key);
      if (n == null) {
         n = new Namespace(key, name, uri);
         var n2 = CACHE.putIfAbsent(key, n);
         return (n2 == null ? n : n2); // HTT: n2 != null branch requires concurrent first-load race
      }
      return n;
   }

   final String key;
   final String name;
   final String uri;

   /**
    * Constructor.
    *
    * @param name The short name of this schema.
    * @param uri The URI of this schema.
    */
   private Namespace(String key, String name, String uri) {
      this.key = key;
      this.name = name;
      this.uri = uri;
   }

   /**
    * Returns the namespace name.
    *
    * @return The namespace name, or <jk>null</jk> if it was not specified.
    */
   public String getName() { return name; }

   /**
    * Returns the namespace URI.
    *
    * @return The namespace URI, or <jk>null</jk> if it was not specified.
    */
   public String getUri() { return uri; }

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