package org.apache.maven.doxia.macro.snippet;
   
   /*
    * 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.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.net.URL;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.regex.Pattern;
  
  import org.codehaus.plexus.util.StringUtils;
  import org.codehaus.plexus.util.IOUtil;
  
  /**
   * Utility class for reading snippets.
   */
  public class SnippetReader
  {
      /** System-dependent EOL. */
      private static final String EOL = System.getProperty( "line.separator" );
  
      /** The source. */
      private URL source;
  
      /** The encoding of the source. */
      private String encoding;
  
      /**
       * Constructor.
       *
       * @param src The source
       * @param encoding The file encoding
       */
      public SnippetReader( URL src, String encoding )
      {
          this.source = src;
          this.encoding = encoding;
      }
  
      /**
       * Constructor.
       *
       * @param src The source
       */
      public SnippetReader( URL src )
      {
          this( src, null ) ;
      }
  
      /**
       * Reads the snippet with given id.
       *
       * @param snippetId The id of the snippet.
       * @return The snippet.
       * @throws java.io.IOException if something goes wrong.
       */
      public StringBuffer readSnippet( String snippetId )
          throws IOException
      {
          List<String> lines = readLines( snippetId );
          int minIndent = minIndent( lines );
          StringBuffer result = new StringBuffer();
          for ( String line : lines )
          {
              result.append( line.substring( minIndent ) );
              result.append( EOL );
          }
          return result;
      }
  
      /**
       * Returns the minimal indent of all the lines in the given List.
       *
       * @param lines A List of lines.
       * @return the minimal indent.
       */
      int minIndent( List<String> lines )
      {
          int minIndent = Integer.MAX_VALUE;
          for ( String line : lines )
         {
             minIndent = Math.min( minIndent, indent( line ) );
         }
         return minIndent;
     }
 
     /**
      * Returns the indent of the given line.
      *
      * @param line A line.
      * @return the indent.
      */
     int indent( String line )
     {
         char[] chars = line.toCharArray();
         int indent = 0;
         for ( ; indent < chars.length; indent++ )
         {
             if ( chars[indent] != ' ' )
             {
                 break;
             }
         }
         return indent;
     }
 
     /**
      * Reads the snippet and returns the lines in a List.
      *
      * @param snippetId The id of the snippet.
      * @return A List of lines.
      * @throws IOException if something goes wrong.
      */
     private List<String> readLines( String snippetId )
         throws IOException
     {
         BufferedReader reader;
         if ( encoding == null || "".equals( encoding ) )
         {
             reader = new BufferedReader( new InputStreamReader( source.openStream() ) );
         }
         else
         {
             reader = new BufferedReader( new InputStreamReader( source.openStream(), encoding ) );
         }
 
         List<String> lines = new ArrayList<>();
         try
         {
             boolean capture = false;
             String line;
             boolean foundStart = false;
             boolean foundEnd = false;
             boolean hasSnippetId = StringUtils.isNotEmpty( snippetId );
             while ( ( line = reader.readLine() ) != null )
             {
                 if ( !hasSnippetId )
                 {
                     lines.add( line );
                 }
                 else
                 {
                     if ( isStart( snippetId, line ) )
                     {
                         capture = true;
                         foundStart = true;
                     }
                     else if ( isEnd( snippetId, line ) )
                     {
                         foundEnd = true;
                         break;
                     }
                     else if ( capture )
                     {
                         lines.add( line );
                     }
                 }
             }
 
             if ( hasSnippetId && !foundStart )
             {
                 throw new IOException( "Failed to find START of snippet " + snippetId + " in file at URL: " + source );
             }
             if ( hasSnippetId && !foundEnd )
             {
                 throw new IOException( "Failed to find END of snippet " + snippetId + " in file at URL: " + source );
             }
         }
         finally
         {
             IOUtil.close( reader );
         }
         return lines;
     }
 
     /**
      * Determines if the given line is a start demarcator.
      *
      * @param snippetId the id of the snippet.
      * @param line the line.
      * @return True, if the line is a start demarcator.
      */
     protected boolean isStart( String snippetId, String line )
     {
         return isDemarcator( snippetId, "START", line );
     }
 
     /**
      * Determines if the given line is a demarcator.
      *
      * @param snippetId the id of the snippet.
      * @param what Identifier for the demarcator.
      * @param line the line.
      * @return True, if the line is a start demarcator.
      */
     protected static boolean isDemarcator( String snippetId, String what, String line )
     {
         // SNIPPET and what are case insensitive
         // SNIPPET and what can switch order
         String snippetRegExp = "(^|\\W)(?i:SNIPPET)($|\\W)";
         String snippetIdRegExp = "(^|\\W)" + snippetId + "($|\\W)";
         String whatRegExp = "(^|\\W)(?i:" + what + ")($|\\W)";
         
         return Pattern.compile( snippetRegExp ).matcher( line ).find()
             && Pattern.compile( whatRegExp ).matcher( line ).find()
             && Pattern.compile( snippetIdRegExp ).matcher( line ).find();
     }
 
     /**
      * Determines if the given line is an end demarcator.
      *
      * @param snippetId the id of the snippet.
      * @param line the line.
      * @return True, if the line is an end demarcator.
      */
     protected boolean isEnd( String snippetId, String line )
     {
         return isDemarcator( snippetId, "END", line );
     }
 }