/*
    * Copyright 2012-2013 smartics, Kronseder & Reiner GmbH
    *
    * Licensed 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 de.smartics.maven.hibernate;
  
  import java.io.ByteArrayOutputStream;
  import java.io.File;
  import java.io.PrintStream;
  import java.net.URL;
  import java.net.URLClassLoader;
  import java.util.ArrayList;
  import java.util.List;
  
  import org.apache.maven.plugin.AbstractMojo;
  import org.apache.maven.plugin.MojoExecutionException;
  import org.apache.maven.plugin.MojoFailureException;
  import org.apache.maven.project.MavenProject;
  import org.hibernate.cfg.Configuration;
  import org.hibernate.cfg.NamingStrategy;
  import org.hibernate.ejb.Ejb3Configuration;
  import org.hibernate.tool.hbm2ddl.SchemaExport;
  
  /**
   * Plugin for schema export to DDL.
   *
   * @goal hbm2ddl
   * @phase process-classes
   * @threadSafe
   * @requiresProject
   * @requiresDependencyResolution compile+runtime
   * @since 1.0
   * @description Runs Hibernate 4' schema export to DDL.
   */
  @SuppressWarnings("deprecation")
  public class SchemaExportMojo extends AbstractMojo
  {
    // ********************************* Fields *********************************
  
    // --- constants ------------------------------------------------------------
  
    // --- members --------------------------------------------------------------
  
    /**
     * The Maven project.
     *
     * @parameter expression="${project}"
     * @required
     * @readonly
     * @since 1.0
     */
    private MavenProject project;
  
    /**
     * The name of the persistence unit to export.
     *
     * @parameter
     * @since 1.0
     */
    private String unitName;
  
    /**
     * The SQL statement delimiter to use.
     *
     * @parameter default-value=";"
     * @since 1.0
     */
    private String delimiter;
  
    /**
     * The file to write the drop schema script to.
     *
     * @parameter default-value="${project.build.directory}/hibernate/drop.sql"
     * @since 1.0
     */
    private String dropOutputFile;
  
    /**
     * The file to write the create schema script to.
     *
     * @parameter default-value="${project.build.directory}/hibernate/create.sql"
     * @since 1.0
     */
    private String createOutputFile;
  
    /**
     * The naming strategy to be used when generating physical column and table
     * names. This must be a complete class name that implements
    * <code>org.hibernate.cfg.NamingStrategy</code> interface (like for example
    * <code>org.hibernate.cfg.ImprovedNamingStrategy</code>).
    *
    * @parameter
    * @since 1.0
    */
   private String namingStrategy;
 
   // ... command ..............................................................
 
   // ... fixes ................................................................
 
   // ****************************** Initializer *******************************
 
   // ****************************** Constructors ******************************
 
   // ****************************** Inner Classes *****************************
 
   // ********************************* Methods ********************************
 
   // --- init -----------------------------------------------------------------
 
   // --- get&set --------------------------------------------------------------
 
   // --- business -------------------------------------------------------------
 
   // CHECKSTYLE:OFF
   /**
    * {@inheritDoc}
    *
    * @see org.apache.maven.plugin.Mojo#execute()
    */
   @Override
   public void execute() throws MojoExecutionException, MojoFailureException
   // CHECKSTYLE:ON
   {
     getLog().info("Exporting '" + unitName + "'.");
 
     ensureOutputFolder(dropOutputFile);
     ensureOutputFolder(createOutputFile);
 
     final Thread currentThread = Thread.currentThread();
     final PrintStream oldOut = System.out;
     final ClassLoader oldClassLoader = currentThread.getContextClassLoader();
     final ArrayList<String> errorMessages = new ArrayList<String>();
 
     try
     {
       // Can't log from here because we are setting a different output stream.
       System.setOut(new PrintStream(new ByteArrayOutputStream()));
 
       currentThread.setContextClassLoader(getClassLoader(oldClassLoader));
 
       final Ejb3Configuration jpaConfiguration =
           new Ejb3Configuration().configure(unitName, null);
 
       final Configuration cfg = jpaConfiguration.getHibernateConfiguration();
       checkNamingStrategy(cfg, errorMessages);
 
       final SchemaExport export = new SchemaExport(cfg);
       export.setDelimiter(delimiter);
       export.setOutputFile(dropOutputFile);
       export.execute(true, false, true, false);
       export.setOutputFile(createOutputFile);
       export.execute(true, false, false, true);
     }
     finally
     {
       System.setOut(oldOut);
       // Now we can log again.
 
       logErrors(errorMessages);
 
       currentThread.setContextClassLoader(oldClassLoader);
     }
   }
 
   private void ensureOutputFolder(final String fileName)
   {
     final File file = new File(fileName);
     final File dir = file.getParentFile();
     if (!dir.exists())
     {
       dir.mkdirs();
     }
   }
 
   @SuppressWarnings("unchecked")
   private ClassLoader getClassLoader(final ClassLoader delegate)
   {
     try
     {
       final List<String> classpathElements = new ArrayList<String>();
       classpathElements.addAll(project.getCompileClasspathElements());
       classpathElements.addAll(project.getRuntimeClasspathElements());
       classpathElements.add(project.getBuild().getOutputDirectory());
 
       final URL urls[] = new URL[classpathElements.size()];
       for (int i = 0; i < classpathElements.size(); ++i)
       {
         urls[i] = new File(classpathElements.get(i)).toURI().toURL();
       }
 
       return new URLClassLoader(urls, delegate);
     }
     catch (final Exception e)
     {
       getLog().debug("Couldn't get the classloader.");
       return this.getClass().getClassLoader();
     }
   }
 
   /**
    * Checks whether the user wants to use a Hibernate naming strategy and sets
    * it if yes.
    *
    * @param cfg The Hibernate configuration object.
    * @param errorMessages The list where error messages will be stored.
    */
   private void checkNamingStrategy(final Configuration cfg,
       final ArrayList<String> errorMessages)
   {
     try
     {
       if (namingStrategy != null && !namingStrategy.isEmpty())
       {
         cfg.setNamingStrategy((NamingStrategy) Class.forName(namingStrategy)
             .newInstance());
       }
     }
     catch (final InstantiationException e)
     {
       errorMessages
           .add("hibernate4-maven-plugin cannot find the informed Hibernate naming strategy. Be sure that you informed the correct class name (InstantiationException).");
       e.printStackTrace();
     }
     catch (final IllegalAccessException e)
     {
       errorMessages
           .add("hibernate4-maven-plugin cannot find the informed Hibernate naming strategy. Be sure that you informed the correct class name (IllegalAccessException).");
       e.printStackTrace();
     }
     catch (final ClassNotFoundException e)
     {
       errorMessages
           .add("hibernate4-maven-plugin cannot find the informed Hibernate naming strategy. Be sure that you informed the correct class name (ClassNotFoundException).");
       e.printStackTrace();
     }
   }
 
   /**
    * Iterates and logs an <code>java.util.ArrayList&lt;String&gt;</code> of
    * error messages using
    * <code>"The following errors were found while executing hibernate4-maven-plugin:"</code>
    * as introduction.
    *
    * @param errorMessages The error messages list.
    */
   private final void logErrors(final ArrayList<String> errorMessages)
   {
     if (errorMessages != null && !errorMessages.isEmpty())
     {
       getLog()
           .info(
               "### The following errors were found while executing hibernate4-maven-plugin:");
 
       for (final String errorMessage : errorMessages)
       {
         getLog().info(" - " + errorMessage);
       }
     }
   }
 
   // --- object basics --------------------------------------------------------
 
 }