/*
    * 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.syncope.core.provisioning.api.utils;
  
  import java.util.Collection;
  import java.util.HashSet;
  import java.util.Optional;
  import java.util.Set;
  import java.util.function.Predicate;
  import java.util.stream.Collectors;
  import org.apache.commons.lang3.tuple.Pair;
  import org.apache.syncope.common.lib.SyncopeConstants;
  
  public final class RealmUtils {
  
      public static String getGroupOwnerRealm(final String realmPath, final String groupKey) {
          return realmPath + '@' + groupKey;
      }
  
      public static Optional<Pair<String, String>> parseGroupOwnerRealm(final String input) {
          String[] split = input.split("@");
          return split == null || split.length < 2
                  ? Optional.empty()
                  : Optional.of(Pair.of(split[0], split[1]));
      }
  
      public static boolean normalizingAddTo(final Set<String> realms, final String newRealm) {
          boolean dontAdd = false;
          Set<String> toRemove = new HashSet<>();
          for (String realm : realms) {
              if (newRealm.startsWith(realm)) {
                  dontAdd = true;
              } else if (realm.startsWith(newRealm)) {
                  toRemove.add(realm);
              }
          }
  
          realms.removeAll(toRemove);
          if (!dontAdd) {
              realms.add(newRealm);
          }
          return !dontAdd;
      }
  
      public static Pair<Set<String>, Set<String>> normalize(final Collection<String> realms) {
          Set<String> normalized = new HashSet<>();
          Set<String> groupOwnership = new HashSet<>();
          if (realms != null) {
              realms.forEach(realm -> {
                  if (realm.indexOf('@') == -1) {
                      normalizingAddTo(normalized, realm);
                  } else {
                      groupOwnership.add(realm);
                  }
              });
          }
  
          return Pair.of(normalized, groupOwnership);
      }
  
      private static class StartsWithPredicate implements Predicate<String> {
  
          private final Collection<String> targets;
  
          StartsWithPredicate(final Collection<String> targets) {
              this.targets = targets;
          }
  
          @Override
          public boolean test(final String realm) {
              return targets.stream().anyMatch(realm::startsWith);
          }
      }
  
      private static final Predicate<String> DYN_REALMS_PREDICATE = r -> !r.startsWith(SyncopeConstants.ROOT_REALM);
  
      public static Set<String> getEffective(final Set<String> allowedRealms, final String requestedRealm) {
          Pair<Set<String>, Set<String>> normalized = normalize(allowedRealms);
  
          Set<String> requested = Set.of(requestedRealm);
  
          StartsWithPredicate normalizedFilter = new StartsWithPredicate(normalized.getLeft());
          StartsWithPredicate requestedFilter = new StartsWithPredicate(requested);
 
         Set<String> effective = new HashSet<>();
         effective.addAll(requested.stream().filter(normalizedFilter).collect(Collectors.toSet()));
         effective.addAll(normalized.getLeft().stream().filter(requestedFilter).collect(Collectors.toSet()));
 
         // includes group ownership
         effective.addAll(normalized.getRight());
 
         // includes dynamic realms
         if (allowedRealms != null) {
             effective.addAll(allowedRealms.stream().filter(DYN_REALMS_PREDICATE).collect(Collectors.toSet()));
         }
 
         return effective;
     }
 
     private RealmUtils() {
         // empty constructor for static utility class 
     }
 }