/*
    * 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.maven.internal.xml;
  
  import java.io.IOException;
  import java.io.Serializable;
  import java.io.StringWriter;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.Iterator;
  import java.util.List;
  import java.util.ListIterator;
  import java.util.Map;
  import java.util.Objects;
  import java.util.Optional;
  import java.util.Set;
  import java.util.stream.Collectors;
  import java.util.stream.Stream;
  
  import org.apache.maven.api.xml.XmlNode;
  import org.codehaus.plexus.util.xml.PrettyPrintXMLWriter;
  import org.codehaus.plexus.util.xml.SerializerXMLWriter;
  import org.codehaus.plexus.util.xml.XMLWriter;
  import org.codehaus.plexus.util.xml.pull.XmlSerializer;
  
  /**
   *  NOTE: remove all the util code in here when separated, this class should be pure data.
   */
  public class XmlNodeImpl implements Serializable, XmlNode {
      private static final long serialVersionUID = 2567894443061173996L;
  
      protected final String name;
  
      protected final String value;
  
      protected final Map<String, String> attributes;
  
      protected final List<XmlNode> children;
  
      protected final Object location;
  
      public XmlNodeImpl(String name) {
          this(name, null, null, null, null);
      }
  
      public XmlNodeImpl(String name, String value) {
          this(name, value, null, null, null);
      }
  
      public XmlNodeImpl(XmlNode from, String name) {
          this(name, from.getValue(), from.getAttributes(), from.getChildren(), from.getInputLocation());
      }
  
      public XmlNodeImpl(
              String name, String value, Map<String, String> attributes, List<XmlNode> children, Object location) {
          this.name = Objects.requireNonNull(name);
          this.value = value;
          this.attributes =
                  attributes != null ? Collections.unmodifiableMap(new HashMap<>(attributes)) : Collections.emptyMap();
          this.children =
                  children != null ? Collections.unmodifiableList(new ArrayList<>(children)) : Collections.emptyList();
          this.location = location;
      }
  
      @Override
      public XmlNode merge(XmlNode source, Boolean childMergeOverride) {
          return merge(this, source, childMergeOverride);
      }
  
      public XmlNode clone() {
          return this;
      }
  
      // ----------------------------------------------------------------------
      // Name handling
      // ----------------------------------------------------------------------
  
      public String getName() {
          return name;
      }
  
      // ----------------------------------------------------------------------
     // Value handling
     // ----------------------------------------------------------------------
 
     public String getValue() {
         return value;
     }
 
     // ----------------------------------------------------------------------
     // Attribute handling
     // ----------------------------------------------------------------------
 
     @Override
     public Map<String, String> getAttributes() {
         return attributes;
     }
 
     public String getAttribute(String name) {
         return attributes.get(name);
     }
 
     // ----------------------------------------------------------------------
     // Child handling
     // ----------------------------------------------------------------------
 
     public XmlNode getChild(String name) {
         if (name != null) {
             ListIterator<XmlNode> it = children.listIterator(children.size());
             while (it.hasPrevious()) {
                 XmlNode child = it.previous();
                 if (name.equals(child.getName())) {
                     return child;
                 }
             }
         }
         return null;
     }
 
     public List<XmlNode> getChildren() {
         return children;
     }
 
     public int getChildCount() {
         return children.size();
     }
 
     // ----------------------------------------------------------------------
     // Input location handling
     // ----------------------------------------------------------------------
 
     /**
      * @since 3.2.0
      * @return input location
      */
     public Object getInputLocation() {
         return location;
     }
 
     // ----------------------------------------------------------------------
     // Helpers
     // ----------------------------------------------------------------------
 
     public void writeToSerializer(String namespace, XmlSerializer serializer) throws IOException {
         // TODO: WARNING! Later versions of plexus-utils psit out an <?xml ?> header due to thinking this is a new
         // document - not the desired behaviour!
         SerializerXMLWriter xmlWriter = new SerializerXMLWriter(namespace, serializer);
         XmlNodeWriter.write(xmlWriter, this);
         if (xmlWriter.getExceptions().size() > 0) {
             throw (IOException) xmlWriter.getExceptions().get(0);
         }
     }
 
     /**
      * Merges one DOM into another, given a specific algorithm and possible override points for that algorithm.<p>
      * The algorithm is as follows:
      * <ol>
      * <li> if the recessive DOM is null, there is nothing to do... return.</li>
      * <li> Determine whether the dominant node will suppress the recessive one (flag=mergeSelf).
      *   <ol type="A">
      *   <li> retrieve the 'combine.self' attribute on the dominant node, and try to match against 'override'...
      *        if it matches 'override', then set mergeSelf == false...the dominant node suppresses the recessive one
      *        completely.</li>
      *   <li> otherwise, use the default value for mergeSelf, which is true...this is the same as specifying
      *        'combine.self' == 'merge' as an attribute of the dominant root node.</li>
      *   </ol></li>
      * <li> If mergeSelf == true
      *   <ol type="A">
      *   <li> Determine whether children from the recessive DOM will be merged or appended to the dominant DOM as
      *        siblings (flag=mergeChildren).
      *     <ol type="i">
      *     <li> if childMergeOverride is set (non-null), use that value (true/false)</li>
      *     <li> retrieve the 'combine.children' attribute on the dominant node, and try to match against
      *          'append'...</li>
      *     <li> if it matches 'append', then set mergeChildren == false...the recessive children will be appended as
      *          siblings of the dominant children.</li>
      *     <li> otherwise, use the default value for mergeChildren, which is true...this is the same as specifying
      *         'combine.children' == 'merge' as an attribute on the dominant root node.</li>
      *     </ol></li>
      *   <li> Iterate through the recessive children, and:
      *     <ol type="i">
      *     <li> if mergeChildren == true and there is a corresponding dominant child (matched by element name),
      *          merge the two.</li>
      *     <li> otherwise, add the recessive child as a new child on the dominant root node.</li>
      *     </ol></li>
      *   </ol></li>
      * </ol>
      */
     @SuppressWarnings("checkstyle:MethodLength")
     public static XmlNode merge(XmlNode dominant, XmlNode recessive, Boolean childMergeOverride) {
         // TODO: share this as some sort of assembler, implement a walk interface?
         if (recessive == null) {
             return dominant;
         }
         if (dominant == null) {
             return recessive;
         }
 
         boolean mergeSelf = true;
 
         String selfMergeMode = dominant.getAttribute(SELF_COMBINATION_MODE_ATTRIBUTE);
 
         if (SELF_COMBINATION_OVERRIDE.equals(selfMergeMode)) {
             mergeSelf = false;
         }
 
         if (mergeSelf) {
 
             String value = dominant.getValue();
             Object location = dominant.getInputLocation();
             Map<String, String> attrs = null;
             List<XmlNode> children = null;
 
             for (Map.Entry<String, String> attr : recessive.getAttributes().entrySet()) {
                 String key = attr.getKey();
                 if (isEmpty(dominant.getAttribute(key))) {
                     if (attrs == null) {
                         attrs = new HashMap<>();
                     }
                     attrs.put(key, attr.getValue());
                 }
             }
 
             if (recessive.getChildren().size() > 0) {
                 boolean mergeChildren = true;
                 if (childMergeOverride != null) {
                     mergeChildren = childMergeOverride;
                 } else {
                     String childMergeMode = dominant.getAttribute(CHILDREN_COMBINATION_MODE_ATTRIBUTE);
                     if (CHILDREN_COMBINATION_APPEND.equals(childMergeMode)) {
                         mergeChildren = false;
                     }
                 }
 
                 Map<String, Iterator<XmlNode>> commonChildren = new HashMap<>();
                 Set<String> names =
                         recessive.getChildren().stream().map(XmlNode::getName).collect(Collectors.toSet());
                 for (String name : names) {
                     List<XmlNode> dominantChildren = dominant.getChildren().stream()
                             .filter(n -> n.getName().equals(name))
                             .collect(Collectors.toList());
                     if (dominantChildren.size() > 0) {
                         commonChildren.put(name, dominantChildren.iterator());
                     }
                 }
 
                 String keysValue = recessive.getAttribute(KEYS_COMBINATION_MODE_ATTRIBUTE);
 
                 for (XmlNode recessiveChild : recessive.getChildren()) {
                     String idValue = recessiveChild.getAttribute(ID_COMBINATION_MODE_ATTRIBUTE);
 
                     XmlNode childDom = null;
                     if (isNotEmpty(idValue)) {
                         for (XmlNode dominantChild : dominant.getChildren()) {
                             if (idValue.equals(dominantChild.getAttribute(ID_COMBINATION_MODE_ATTRIBUTE))) {
                                 childDom = dominantChild;
                                 // we have a match, so don't append but merge
                                 mergeChildren = true;
                             }
                         }
                     } else if (isNotEmpty(keysValue)) {
                         String[] keys = keysValue.split(",");
                         Map<String, Optional<String>> recessiveKeyValues = Stream.of(keys)
                                 .collect(Collectors.toMap(
                                         k -> k, k -> Optional.ofNullable(recessiveChild.getAttribute(k))));
 
                         for (XmlNode dominantChild : dominant.getChildren()) {
                             Map<String, Optional<String>> dominantKeyValues = Stream.of(keys)
                                     .collect(Collectors.toMap(
                                             k -> k, k -> Optional.ofNullable(dominantChild.getAttribute(k))));
 
                             if (recessiveKeyValues.equals(dominantKeyValues)) {
                                 childDom = dominantChild;
                                 // we have a match, so don't append but merge
                                 mergeChildren = true;
                             }
                         }
                     } else {
                         childDom = dominant.getChild(recessiveChild.getName());
                     }
 
                     if (mergeChildren && childDom != null) {
                         String name = recessiveChild.getName();
                         Iterator<XmlNode> it =
                                 commonChildren.computeIfAbsent(name, n1 -> Stream.of(dominant.getChildren().stream()
                                                 .filter(n2 -> n2.getName().equals(n1))
                                                 .collect(Collectors.toList()))
                                         .filter(l -> !l.isEmpty())
                                         .map(List::iterator)
                                         .findFirst()
                                         .orElse(null));
                         if (it == null) {
                             if (children == null) {
                                 children = new ArrayList<>(dominant.getChildren());
                             }
                             children.add(recessiveChild);
                         } else if (it.hasNext()) {
                             XmlNode dominantChild = it.next();
 
                             String dominantChildCombinationMode =
                                     dominantChild.getAttribute(SELF_COMBINATION_MODE_ATTRIBUTE);
                             if (SELF_COMBINATION_REMOVE.equals(dominantChildCombinationMode)) {
                                 if (children == null) {
                                     children = new ArrayList<>(dominant.getChildren());
                                 }
                                 children.remove(dominantChild);
                             } else {
                                 int idx = dominant.getChildren().indexOf(dominantChild);
                                 XmlNode merged = merge(dominantChild, recessiveChild, childMergeOverride);
                                 if (merged != dominantChild) {
                                     if (children == null) {
                                         children = new ArrayList<>(dominant.getChildren());
                                     }
                                     children.set(idx, merged);
                                 }
                             }
                         }
                     } else {
                         if (children == null) {
                             children = new ArrayList<>(dominant.getChildren());
                         }
                         int idx = mergeChildren
                                 ? children.size()
                                 : recessive.getChildren().indexOf(recessiveChild);
                         children.add(idx, recessiveChild);
                     }
                 }
             }
 
             if (value != null || attrs != null || children != null) {
                 if (attrs != null) {
                     Map<String, String> nattrs = attrs;
                     attrs = new HashMap<>(dominant.getAttributes());
                     attrs.putAll(nattrs);
                 } else {
                     attrs = dominant.getAttributes();
                 }
                 if (children == null) {
                     children = dominant.getChildren();
                 }
                 return new XmlNodeImpl(
                         dominant.getName(), value != null ? value : dominant.getValue(), attrs, children, location);
             }
         }
         return dominant;
     }
 
     /**
      * Merge two DOMs, with one having dominance in the case of collision. Merge mechanisms (vs. override for nodes, or
      * vs. append for children) is determined by attributes of the dominant root node.
      *
      * @see #CHILDREN_COMBINATION_MODE_ATTRIBUTE
      * @see #SELF_COMBINATION_MODE_ATTRIBUTE
      * @param dominant The dominant DOM into which the recessive value/attributes/children will be merged
      * @param recessive The recessive DOM, which will be merged into the dominant DOM
      * @return merged DOM
      */
     public static XmlNode merge(XmlNode dominant, XmlNode recessive) {
         return merge(dominant, recessive, null);
     }
 
     // ----------------------------------------------------------------------
     // Standard object handling
     // ----------------------------------------------------------------------
 
     @Override
     public boolean equals(Object o) {
         if (this == o) {
             return true;
         }
         if (o == null || getClass() != o.getClass()) {
             return false;
         }
         XmlNodeImpl that = (XmlNodeImpl) o;
         return Objects.equals(this.name, that.name)
                 && Objects.equals(this.value, that.value)
                 && Objects.equals(this.attributes, that.attributes)
                 && Objects.equals(this.children, that.children);
     }
 
     @Override
     public int hashCode() {
         return Objects.hash(name, value, attributes, children);
     }
 
     @Override
     public String toString() {
         StringWriter writer = new StringWriter();
         XmlNodeWriter.write(writer, this);
         return writer.toString();
     }
 
     public String toUnescapedString() {
         StringWriter writer = new StringWriter();
         XMLWriter xmlWriter = new PrettyPrintXMLWriter(writer);
         XmlNodeWriter.write(xmlWriter, this, false);
         return writer.toString();
     }
 
     private static boolean isNotEmpty(String str) {
         return ((str != null) && (str.length() > 0));
     }
 
     private static boolean isEmpty(String str) {
         return ((str == null) || (str.length() == 0));
     }
 }