package org.apache.maven.shared.dependency.graph.traversal;
   
   /*
    * 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.
   */
  
  import java.io.PrintWriter;
  import java.io.Writer;
  import java.util.List;
  
  import org.apache.maven.shared.dependency.graph.DependencyNode;
  
  /**
   * A dependency node visitor that serializes visited nodes to a writer.
   * 
   * @author <a href="mailto:markhobson@gmail.com">Mark Hobson</a>
   */
  public class SerializingDependencyNodeVisitor
      implements DependencyNodeVisitor
  {
      // classes ----------------------------------------------------------------
  
      /**
       * Provides tokens to use when serializing the dependency graph.
       */
      public static class GraphTokens
      {
          private final String nodeIndent;
  
          private final String lastNodeIndent;
  
          private final String fillIndent;
  
          private final String lastFillIndent;
  
          public GraphTokens( String nodeIndent, String lastNodeIndent, String fillIndent, String lastFillIndent )
          {
              this.nodeIndent = nodeIndent;
              this.lastNodeIndent = lastNodeIndent;
              this.fillIndent = fillIndent;
              this.lastFillIndent = lastFillIndent;
          }
  
          public String getNodeIndent( boolean last )
          {
              return last ? lastNodeIndent : nodeIndent;
          }
  
          public String getFillIndent( boolean last )
          {
              return last ? lastFillIndent : fillIndent;
          }
      }
  
      // constants --------------------------------------------------------------
  
      /**
       * Whitespace tokens to use when outputing the dependency graph.
       */
      public static final GraphTokens WHITESPACE_TOKENS = new GraphTokens( "   ", "   ", "   ", "   " );
  
      /**
       * The standard ASCII tokens to use when outputing the dependency graph.
       */
      public static final GraphTokens STANDARD_TOKENS = new GraphTokens( "+- ", "\\- ", "|  ", "   " );
  
      /**
       * The extended ASCII tokens to use when outputing the dependency graph.
       */
      public static final GraphTokens EXTENDED_TOKENS = new GraphTokens( "\u251C\u2500 ", "\u2514\u2500 ", "\u2502  ",
                                                                         "   " );
  
      // fields -----------------------------------------------------------------
  
      /**
       * The writer to serialize to.
       */
      private final PrintWriter writer;
  
      /**
       * The tokens to use when serializing the dependency graph.
       */
      private final GraphTokens tokens;
  
     /**
      * The depth of the currently visited dependency node.
      */
     private int depth;
 
     // constructors -----------------------------------------------------------
 
     /**
      * Creates a dependency node visitor that serializes visited nodes to the specified writer using whitespace tokens.
      * 
      * @param writer the writer to serialize to
      */
     public SerializingDependencyNodeVisitor( Writer writer )
     {
         this( writer, WHITESPACE_TOKENS );
     }
 
     /**
      * Creates a dependency node visitor that serializes visited nodes to the specified writer using the specified
      * tokens.
      * 
      * @param writer the writer to serialize to
      * @param tokens the tokens to use when serializing the dependency graph
      */
     public SerializingDependencyNodeVisitor( Writer writer, GraphTokens tokens )
     {
         if ( writer instanceof PrintWriter )
         {
             this.writer = (PrintWriter) writer;
         }
         else
         {
             this.writer = new PrintWriter( writer, true );
         }
 
         this.tokens = tokens;
 
         depth = 0;
     }
 
     // DependencyNodeVisitor methods ------------------------------------------
 
     /**
      * {@inheritDoc}
      */
     @Override
     public boolean visit( DependencyNode node )
     {
         indent( node );
 
         writer.println( node.toNodeString() );
 
         depth++;
 
         return true;
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     public boolean endVisit( DependencyNode node )
     {
         depth--;
 
         return true;
     }
 
     // private methods --------------------------------------------------------
 
     /**
      * Writes the necessary tokens to indent the specified dependency node to this visitor's writer.
      * 
      * @param node the dependency node to indent
      */
     private void indent( DependencyNode node )
     {
         for ( int i = 1; i < depth; i++ )
         {
             writer.write( tokens.getFillIndent( isLast( node, i ) ) );
         }
 
         if ( depth > 0 )
         {
             writer.write( tokens.getNodeIndent( isLast( node ) ) );
         }
     }
 
     /**
      * Gets whether the specified dependency node is the last of its siblings.
      * 
      * @param node the dependency node to check
      * @return <code>true</code> if the specified dependency node is the last of its last siblings
      */
     private boolean isLast( DependencyNode node )
     {
         // TODO: remove node argument and calculate from visitor calls only
 
         DependencyNode parent = node.getParent();
 
         boolean last;
 
         if ( parent == null )
         {
             last = true;
         }
         else
         {
             List<DependencyNode> siblings = parent.getChildren();
 
             last = ( siblings.indexOf( node ) == siblings.size() - 1 );
         }
 
         return last;
     }
 
     /**
      * Gets whether the specified dependency node ancestor is the last of its siblings.
      * 
      * @param node the dependency node whose ancestor to check
      * @param ancestorDepth the depth of the ancestor of the specified dependency node to check
      * @return <code>true</code> if the specified dependency node ancestor is the last of its siblings
      */
     private boolean isLast( DependencyNode node, int ancestorDepth )
     {
         // TODO: remove node argument and calculate from visitor calls only
 
         int distance = depth - ancestorDepth;
 
         while ( distance-- > 0 )
         {
             node = node.getParent();
         }
 
         return isLast( node );
     }
 }