/*
    * 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.plugins.dependency.tree;
  
  import java.io.Writer;
  import org.apache.maven.shared.dependency.graph.DependencyNode;
  import org.apache.maven.shared.dependency.graph.traversal.DependencyNodeVisitor;
  
  /**
   * A dependency node visitor that serializes visited nodes to a writer using the
   * <a href="https://en.wikipedia.org/wiki/GraphML">graphml format</a>.
   *
   * @author <a href="mailto:jerome.creignou@gmail.com">Jerome Creignou</a>
   * @since 2.1
   */
  public class GraphmlDependencyNodeVisitor extends AbstractSerializingVisitor implements DependencyNodeVisitor {
  
      /**
       * Graphml xml file header. Define Schema and root element. We also define 2 key as meta data.
       */
      private static final String GRAPHML_HEADER = "<?xml version=\"1.0\" encoding=\"UTF-8\"?> "
              + "<graphml xmlns=\"http://graphml.graphdrawing.org/xmlns\" "
              + "xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" "
              + "xmlns:y=\"http://www.yworks.com/xml/graphml\" "
              + "xsi:schemaLocation=\"http://graphml.graphdrawing.org/xmlns "
              + "http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd\">" + System.lineSeparator()
              + "  <key for=\"node\" id=\"d0\" yfiles.type=\"nodegraphics\"/> " + System.lineSeparator()
              + "  <key for=\"edge\" id=\"d1\" yfiles.type=\"edgegraphics\"/> " + System.lineSeparator()
              + "<graph id=\"dependencies\" edgedefault=\"directed\">" + System.lineSeparator();
  
      /**
       * Graphml xml file footer.
       */
      private static final String GRAPHML_FOOTER = "</graph></graphml>";
  
      /**
       * Constructor.
       *
       * @param writer the writer to write to.
       */
      public GraphmlDependencyNodeVisitor(Writer writer) {
          super(writer);
      }
  
      /**
       * {@inheritDoc}
       */
      @Override
      public boolean endVisit(DependencyNode node) {
          if (node.getParent() == null || node.getParent() == node) {
              writer.write(GRAPHML_FOOTER);
          } else {
              DependencyNode p = node.getParent();
              writer.print("<edge source=\"" + generateId(p) + "\" target=\"" + generateId(node) + "\">");
              if (node.getArtifact().getScope() != null) {
                  // add Edge label
                  writer.print("<data key=\"d1\"><y:PolyLineEdge><y:EdgeLabel>"
                          + node.getArtifact().getScope() + "</y:EdgeLabel></y:PolyLineEdge></data>");
              }
              writer.println("</edge>");
          }
          return true;
      }
  
      /**
       * {@inheritDoc}
       */
      @Override
      public boolean visit(DependencyNode node) {
          if (node.getParent() == null || node.getParent() == node) {
              writer.write(GRAPHML_HEADER);
          }
          // write node
          writer.print("<node id=\"" + generateId(node) + "\">");
          // add node label
          writer.print("<data key=\"d0\"><y:ShapeNode><y:NodeLabel>" + node.toNodeString()
                  + "</y:NodeLabel></y:ShapeNode></data>");
          writer.println("</node>");
          return true;
      }
  
      /**
       * Generate a unique id from a DependencyNode.
      * <p>
      * Current implementation is rather simple and uses hashcode.
      * </p>
      *
      * @param node the DependencyNode to use.
      * @return the unique id.
      */
     private static String generateId(DependencyNode node) {
         return String.valueOf(node.hashCode());
     }
 }