/*

  * 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.shade.mojo;

 import java.io.File;

 import java.util.ArrayList;

 import java.util.Collections;

 import java.util.List;

 /**

  *

  */

 public final class RelativizePath

 {

     private RelativizePath() {

         //

     }

     /**

      * relativize a pathname. 

      * @param thing Absolute File of something. (e.g., a parent pom)

      * @param relativeTo base to relativize it do. (e.g., a pom into which a relative pathname to the 'thing' is to be installed).

      * @return

      */

     static String convertToRelativePath(File thing, File relativeTo) {

         StringBuilder relativePath = null;

         if ( thing.getParentFile().equals( relativeTo.getParentFile() ))

         {

             return thing.getName(); // a very simple relative path.

         }

         List<String> thingDirectories = RelativizePath.parentDirs( thing );

         List<String> relativeToDirectories = RelativizePath.parentDirs( relativeTo );

         //Get the shortest of the two paths

         int length = thingDirectories.size() < relativeToDirectories.size() ? thingDirectories.size() : relativeToDirectories.size();

         int lastCommonRoot = -1; // index of the lowest directory down from the root that the two have in common.

         int index;

         //Find common root

         for ( index = 0; index < length; index++ ) 

         {

             if ( thingDirectories.get( index ).equals(relativeToDirectories.get( index )))

             {

                 lastCommonRoot = index;

             } else {

                 break;

             }

         }

         if (lastCommonRoot != -1) { // possible on Windows or other multi-root cases.

             //Build up the relative path

             relativePath = new StringBuilder();

             // add ..'s to get from the base up to the common point

             for ( index = lastCommonRoot + 1; index < relativeToDirectories.size(); index++ ) 

             {

                 relativePath.append( "../" );

             }

             // now add down from the common point to the actual 'thing' item. 

             for ( index = lastCommonRoot + 1; index < thingDirectories.size(); index++ ) 

             {

                 relativePath.append( thingDirectories.get( index ) + "/" );

             }

             relativePath.append( thing.getName() );

             return relativePath.toString();

         }

         return null;

     }

     static List<String> parentDirs( File of )

     {

         List<String> results = new ArrayList<String>();

         for ( File p = of.getParentFile() ; p != null ; p = p.getParentFile() )

         {

             if ( !"".equals(p.getName()) )

             {

                 results.add( p.getName() );

             }

         }

         Collections.reverse( results );

         return results;

     }

 }