/*
    * 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.shiro.subject;
  
  import org.apache.shiro.util.CollectionUtils;
  import org.apache.shiro.lang.util.StringUtils;
  
  import java.io.IOException;
  import java.io.ObjectInputStream;
  import java.io.ObjectOutputStream;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.LinkedHashMap;
  import java.util.LinkedHashSet;
  import java.util.List;
  import java.util.Map;
  import java.util.Objects;
  import java.util.Set;
  
  /**
   * A simple implementation of the {@link MutablePrincipalCollection} interface that tracks principals internally
   * by storing them in a {@link LinkedHashMap}.
   *
   * @since 0.9
   */
  @SuppressWarnings({"unchecked"})
  public class SimplePrincipalCollection implements MutablePrincipalCollection {
  
      // Serialization reminder:
      // You _MUST_ change this number if you introduce a change to this class
      // that is NOT serialization backwards compatible.  Serialization-compatible
      // changes do not require a change to this number.  If you need to generate
      // a new number in this case, use the JDK's 'serialver' program to generate it.
      private static final long serialVersionUID = -6305224034025797558L;
  
      //TODO - complete JavaDoc
      private Map<String, Set> realmPrincipals;
  
      //cached toString() result, as this can be printed many times in logging
      private transient String cachedToString;
  
      public SimplePrincipalCollection() {
      }
  
      public SimplePrincipalCollection(Object principal, String realmName) {
          if (principal instanceof Collection) {
              addAll((Collection) principal, realmName);
          } else {
              add(principal, realmName);
          }
      }
  
      public SimplePrincipalCollection(Collection principals, String realmName) {
          addAll(principals, realmName);
      }
  
      public SimplePrincipalCollection(PrincipalCollection principals) {
          addAll(principals);
      }
  
      protected Collection getPrincipalsLazy(String realmName) {
          if (realmPrincipals == null) {
              realmPrincipals = new LinkedHashMap<String, Set>();
          }
          Set principals = realmPrincipals.get(realmName);
          if (principals == null) {
              principals = new LinkedHashSet();
              realmPrincipals.put(realmName, principals);
          }
          return principals;
      }
  
      /**
       * Returns the first available principal from any of the {@code Realm} principals, or {@code null} if there are
       * no principals yet.
       * <p/>
       * The 'first available principal' is interpreted as the principal that would be returned by
       * <code>{@link #iterator() iterator()}.{@link java.util.Iterator#next() next()}.</code>
       *
       * @inheritDoc
       */
     public Object getPrimaryPrincipal() {
         if (isEmpty()) {
             return null;
         }
         return iterator().next();
     }
 
     public void add(Object principal, String realmName) {
         if (realmName == null) {
             throw new NullPointerException("realmName argument cannot be null.");
         }
         if (principal == null) {
             throw new NullPointerException("principal argument cannot be null.");
         }
         this.cachedToString = null;
         getPrincipalsLazy(realmName).add(principal);
     }
 
     public void addAll(Collection principals, String realmName) {
         if (realmName == null) {
             throw new NullPointerException("realmName argument cannot be null.");
         }
         if (principals == null) {
             throw new NullPointerException("principals argument cannot be null.");
         }
         if (principals.isEmpty()) {
             throw new IllegalArgumentException("principals argument cannot be an empty collection.");
         }
         this.cachedToString = null;
         getPrincipalsLazy(realmName).addAll(principals);
     }
 
     public void addAll(PrincipalCollection principals) {
         if (principals.getRealmNames() != null) {
             for (String realmName : principals.getRealmNames()) {
                 for (Object principal : principals.fromRealm(realmName)) {
                     add(principal, realmName);
                 }
             }
         }
     }
 
     public <T> T oneByType(Class<T> type) {
         if (realmPrincipals == null || realmPrincipals.isEmpty()) {
             return null;
         }
         Collection<Set> values = realmPrincipals.values();
         for (Set set : values) {
             for (Object o : set) {
                 if (type.isAssignableFrom(o.getClass())) {
                     return (T) o;
                 }
             }
         }
         return null;
     }
 
     public <T> Collection<T> byType(Class<T> type) {
         if (realmPrincipals == null || realmPrincipals.isEmpty()) {
             return Collections.EMPTY_SET;
         }
         Set<T> typed = new LinkedHashSet<T>();
         Collection<Set> values = realmPrincipals.values();
         for (Set set : values) {
             for (Object o : set) {
                 if (type.isAssignableFrom(o.getClass())) {
                     typed.add((T) o);
                 }
             }
         }
         if (typed.isEmpty()) {
             return Collections.EMPTY_SET;
         }
         return Collections.unmodifiableSet(typed);
     }
 
     public List asList() {
         Set all = asSet();
         if (all.isEmpty()) {
             return Collections.EMPTY_LIST;
         }
         return Collections.unmodifiableList(new ArrayList(all));
     }
 
     public Set asSet() {
         if (realmPrincipals == null || realmPrincipals.isEmpty()) {
             return Collections.EMPTY_SET;
         }
         Set aggregated = new LinkedHashSet();
         Collection<Set> values = realmPrincipals.values();
         for (Set set : values) {
             aggregated.addAll(set);
         }
         if (aggregated.isEmpty()) {
             return Collections.EMPTY_SET;
         }
         return Collections.unmodifiableSet(aggregated);
     }
 
     public Collection fromRealm(String realmName) {
         if (realmPrincipals == null || realmPrincipals.isEmpty()) {
             return Collections.EMPTY_SET;
         }
         Set principals = realmPrincipals.get(realmName);
         if (principals == null || principals.isEmpty()) {
             principals = Collections.EMPTY_SET;
         }
         return Collections.unmodifiableSet(principals);
     }
 
     public Set<String> getRealmNames() {
         if (realmPrincipals == null) {
             return null;
         } else {
             return realmPrincipals.keySet();
         }
     }
 
     public boolean isEmpty() {
         return realmPrincipals == null || realmPrincipals.isEmpty();
     }
 
     public void clear() {
         this.cachedToString = null;
         if (realmPrincipals != null) {
             realmPrincipals.clear();
             realmPrincipals = null;
         }
     }
 
     public Iterator iterator() {
         return asSet().iterator();
     }
 
     public boolean equals(Object o) {
         if (o == this) {
             return true;
         }
         if (o instanceof SimplePrincipalCollection) {
             SimplePrincipalCollection other = (SimplePrincipalCollection) o;
             return Objects.equals(this.realmPrincipals, other.realmPrincipals);
         }
         return false;
     }
 
     public int hashCode() {
         if (this.realmPrincipals != null && !realmPrincipals.isEmpty()) {
             return realmPrincipals.hashCode();
         }
         return super.hashCode();
     }
 
     /**
      * Returns a simple string representation suitable for printing.
      *
      * @return a simple string representation suitable for printing.
      * @since 1.0
      */
     public String toString() {
         if (this.cachedToString == null) {
             Set<Object> principals = asSet();
             if (!CollectionUtils.isEmpty(principals)) {
                 this.cachedToString = StringUtils.toString(principals.toArray());
             } else {
                 this.cachedToString = "empty";
             }
         }
         return this.cachedToString;
     }
 
 
     /**
      * Serialization write support.
      * <p/>
      * NOTE: Don't forget to change the serialVersionUID constant at the top of this class
      * if you make any backwards-incompatible serialization changes!!!
      * (use the JDK 'serialver' program for this)
      *
      * @param out output stream provided by Java serialization
      * @throws IOException if there is a stream error
      */
     private void writeObject(ObjectOutputStream out) throws IOException {
         out.defaultWriteObject();
         boolean principalsExist = !CollectionUtils.isEmpty(realmPrincipals);
         out.writeBoolean(principalsExist);
         if (principalsExist) {
             out.writeObject(realmPrincipals);
         }
     }
 
     /**
      * Serialization read support - reads in the Map principals collection if it exists in the
      * input stream.
      * <p/>
      * NOTE: Don't forget to change the serialVersionUID constant at the top of this class
      * if you make any backwards-incompatible serialization changes!!!
      * (use the JDK 'serialver' program for this)
      *
      * @param in input stream provided by
      * @throws IOException            if there is an input/output problem
      * @throws ClassNotFoundException if the underlying Map implementation class is not available to the classloader.
      */
     private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
         in.defaultReadObject();
         boolean principalsExist = in.readBoolean();
         if (principalsExist) {
             this.realmPrincipals = (Map<String, Set>) in.readObject();
         }
     }
 }