package org.apache.maven.shared.incremental;
   
   /*
    * 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 org.apache.maven.execution.MavenSession;
  import org.apache.maven.plugin.MojoExecution;
  import org.apache.maven.plugin.MojoExecutionException;
  import org.apache.maven.project.MavenProject;
  import org.apache.maven.shared.utils.io.DirectoryScanResult;
  import org.apache.maven.shared.utils.io.DirectoryScanner;
  import org.apache.maven.shared.utils.io.FileUtils;
  
  import java.io.File;
  import java.io.IOException;
  import java.util.Set;
  
  /**
   * Various helper methods to support incremental builds
   *
   */
  public class IncrementalBuildHelper
  {
      /**
       * the root directory to store status information about maven executions in.
       */
      private static final String MAVEN_STATUS_ROOT = "maven-status";
      public static final String CREATED_FILES_LST_FILENAME = "createdFiles.lst";
      private static final String INPUT_FILES_LST_FILENAME = "inputFiles.lst";
  
      /**
       * Needed for storing the status for the incremental build support.
       */
      private MojoExecution mojoExecution;
  
      /**
       * Needed for storing the status for the incremental build support.
       */
      private MavenProject mavenProject;
  
      /**
       * Used for detecting changes between the Mojo execution.
       * @see #getDirectoryScanner();
       */
      private DirectoryScanner directoryScanner;
  
      /**
       * Once the {@link #beforeRebuildExecution(java.io.File)} gots called
       * this will contain the list of files in the build directory.
       */
      private String[] filesBeforeAction = new String[0];
  
      public IncrementalBuildHelper( MojoExecution mojoExecution, MavenSession mavenSession )
      {
          this( mojoExecution, getMavenProject( mavenSession ) );
      }
  
      public IncrementalBuildHelper( MojoExecution mojoExecution, MavenProject mavenProject )
      {
          if ( mavenProject == null )
          {
              throw new IllegalArgumentException( "MavenProject must not be null!" );
          }
          if ( mojoExecution == null )
          {
              throw new IllegalArgumentException( "MojoExecution must not be null!" );
          }
  
          this.mavenProject = mavenProject;
          this.mojoExecution = mojoExecution;
      }
  
      /**
       * small helper method to allow for the nullcheck in the ct invocation
       */
      private static MavenProject getMavenProject( MavenSession mavenSession )
      {
          if ( mavenSession == null )
          {
              throw new IllegalArgumentException( "MavenSession must not be null!" );
          }
  
         return mavenSession.getCurrentProject();
     }
 
     /**
      * Get the existing DirectoryScanner used by this helper,
      * or create new a DirectoryScanner if none is yet set.
      * The DirectoryScanner is used for detecting changes in a directory
      */
     public DirectoryScanner getDirectoryScanner()
     {
         if ( directoryScanner == null )
         {
             directoryScanner = new DirectoryScanner();
         }
 
         return directoryScanner;
     }
 
     /**
      * Set the DirectoryScanner which shall get used by this build helper.
      * @param directoryScanner
      */
     public void setDirectoryScanner( DirectoryScanner directoryScanner )
     {
         this.directoryScanner = directoryScanner;
     }
 
     /**
      * We use a specific status directory for each mojo execution to store state
      * which is needed during the next build invocation run.
      * @return the directory for storing status information of the current mojo execution.
      */
     public File getMojoStatusDirectory() throws MojoExecutionException
     {
         if ( mojoExecution == null )
         {
             throw new MojoExecutionException( "MojoExecution could not get resolved" );
         }
 
         File buildOutputDirectory = new File( mavenProject.getBuild().getDirectory() );
 
         //X TODO the executionId contains -cli and -mojoname
         //X we should remove those postfixes as it should not make
         //X any difference whether being run on the cli or via build
         String mojoStatusPath = MAVEN_STATUS_ROOT + File.separator
                                 + mojoExecution.getMojoDescriptor().getPluginDescriptor().getArtifactId() + File.separator
                                 + mojoExecution.getMojoDescriptor().getGoal() + File.separator
                                 + mojoExecution.getExecutionId();
 
         File mojoStatusDir = new File( buildOutputDirectory, mojoStatusPath );
 
         if ( !mojoStatusDir.exists() )
         {
             mojoStatusDir.mkdirs();
         }
 
         return mojoStatusDir;
     }
 
     /**
      * Detect whether the list of detected files has changed since the last build.
      * We simply load the list of files for the previous build from a status file
      * and compare it with the new list. Afterwards we store the new list in the status file.
      *
      * @param inputFiles
      * @return <code>true</code> if the set of inputFiles got changed since the last build.
      * @throws MojoExecutionException
      */
     public boolean inputFileTreeChanged( Set<File> inputFiles ) throws MojoExecutionException
     {
         File mojoConfigBase = getMojoStatusDirectory();
         File mojoConfigFile = new File( mojoConfigBase, INPUT_FILES_LST_FILENAME );
 
         String[] oldInputFiles = new String[0];
 
         if ( mojoConfigFile.exists() )
         {
             try
             {
                 oldInputFiles = FileUtils.fileReadArray( mojoConfigFile );
             }
             catch( IOException e )
             {
                 throw new MojoExecutionException( "Error reading old mojo status " + mojoConfigFile, e );
             }
         }
 
         String[] inputFileNames = new String[ inputFiles.size() ];
         int i = 0;
         for ( File inputFile : inputFiles )
         {
             inputFileNames[ i++ ] = inputFile.getAbsolutePath();
         }
 
         DirectoryScanResult dsr = DirectoryScanner.diffFiles( oldInputFiles, inputFileNames );
 
 
         try
         {
             FileUtils.fileWriteArray( mojoConfigFile, inputFileNames );
         }
         catch( IOException e )
         {
             throw new MojoExecutionException( "Error while storing the mojo status", e );
         }
 
         return ( dsr.getFilesAdded().length > 0 || dsr.getFilesRemoved().length > 0 );
     }
 
     /**
      * Detect whether the list of detected files picked up by the DirectoryScanner
      * has changed since the last build.
      * We simply load the list of files for the previous build from a status file
      * and compare it with the result of the new DirectoryScanner#scan().
      * Afterwards we store the new list in the status file.
      *
      * @param dirScanner
      * @return <code>true</code> if the set of inputFiles got changed since the last build.
      * @throws MojoExecutionException
      */
     public boolean inputFileTreeChanged( DirectoryScanner dirScanner ) throws MojoExecutionException
     {
         File mojoConfigBase = getMojoStatusDirectory();
         File mojoConfigFile = new File( mojoConfigBase, INPUT_FILES_LST_FILENAME );
 
         String[] oldInputFiles = new String[0];
 
         if ( mojoConfigFile.exists() )
         {
             try
             {
                 oldInputFiles = FileUtils.fileReadArray( mojoConfigFile );
             }
             catch( IOException e )
             {
                 throw new MojoExecutionException( "Error reading old mojo status " + mojoConfigFile, e );
             }
         }
 
         dirScanner.scan();
 
         try
         {
             // store away the list of input files
             FileUtils.fileWriteArray( mojoConfigFile, dirScanner.getIncludedFiles() );
         }
         catch( IOException e )
         {
             throw new MojoExecutionException( "Error while storing new mojo status" + mojoConfigFile, e );
         }
 
         DirectoryScanResult dsr = dirScanner.diffIncludedFiles( oldInputFiles );
 
         return ( dsr.getFilesAdded().length > 0 || dsr.getFilesRemoved().length > 0 );
     }
 
     /**
      * <p>This method shall get invoked before the actual mojo task gets triggered,
      * e.g. the actual compile in maven-compiler-plugin.</p>
      *
      * <p><b>Attention:</b> This method shall only get invoked if the plugin re-creates <b>all</b> the output.</p>
      *
      * <p>It first picks up the list of files created in the previous build and delete them.
      * This step is necessary to prevent left-overs. After that we take a 'directory snapshot'
      * (list of all files which exist in the outputDirectory after the clean). </p>
      *
      * <p>After the actual mojo task got executed you should invoke the method
      * {@link #afterRebuildExecution()} to collect the list of files which got changed
      * by this task.</p>
      *
      *
      * @param outputDirectory
      * @return all files which got created in the previous build and have been deleted now.
      * @throws MojoExecutionException
      */
     public String[] beforeRebuildExecution( File outputDirectory ) throws MojoExecutionException
     {
         File mojoConfigBase = getMojoStatusDirectory();
         File mojoConfigFile = new File( mojoConfigBase, CREATED_FILES_LST_FILENAME );
 
         String[] oldFiles;
 
         try
         {
             oldFiles = FileUtils.fileReadArray( mojoConfigFile );
             for ( String oldFileName : oldFiles )
             {
                 File oldFile = new File( outputDirectory, oldFileName );
                 oldFile.delete();
             }
         }
         catch( IOException e )
         {
             throw new MojoExecutionException( "Error reading old mojo status", e );
         }
 
         // we remember all files which currently exist in the output directory
         DirectoryScanner diffScanner = getDirectoryScanner();
         diffScanner.setBasedir( outputDirectory );
         if ( outputDirectory.exists() )
         {
             diffScanner.scan();
             filesBeforeAction = diffScanner.getIncludedFiles();
         }
 
         return oldFiles;
     }
 
     /**
      * <p>This method collects and stores all information about files changed since
      * the call to {@link #beforeRebuildExecution(java.io.File)}.</p>
      *
      * <p><b>Attention:</b> This method shall only get invoked if the plugin re-creates <b>all</b> the output.</p>
      *
      * @throws MojoExecutionException
      */
     public void afterRebuildExecution() throws MojoExecutionException
     {
         DirectoryScanner diffScanner = getDirectoryScanner();
         // now scan the same directory again and create a diff
         diffScanner.scan();
         DirectoryScanResult scanResult = diffScanner.diffIncludedFiles( filesBeforeAction );
 
         File mojoConfigBase = getMojoStatusDirectory();
         File mojoConfigFile = new File( mojoConfigBase, CREATED_FILES_LST_FILENAME );
 
         try
         {
             FileUtils.fileWriteArray( mojoConfigFile, scanResult.getFilesAdded() );
         }
         catch( IOException e )
         {
             throw new MojoExecutionException( "Error while storing the mojo status", e );
         }
 
     }
 }