/*
    * Copyright 2006-2012 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.plugin.buildmetadata.maven;
  
  import java.lang.reflect.InvocationTargetException;
  import java.util.Properties;
  
  import org.apache.commons.beanutils.PropertyUtils;
  import org.apache.maven.project.MavenProject;
  
  /**
   * Fetches properties from a Maven project. This includes properties of the
   * Maven project instance as well as properties from its properties section.
   * <p>
   * It is allowed to change the project passed to the helper instance after
   * creation of the instance as long as the caller makes sure that it is not
   * changed within a call of this instance. No synchronization is cared for by
   * this instance.
   * </p>
   *
   * @author <a href="mailto:robert.reiner@smartics.de">Robert Reiner</a>
   * @version $Revision:591 $
   */
  public final class MavenPropertyHelper
  {
    // ********************************* Fields *********************************
  
    // --- constants ------------------------------------------------------------
  
    /**
     * All properties referring to the Maven project instance start with this
     * prefix.
     * <p>
     * The value of this constant is {@value}.
     * </p>
     */
    private static final String PROJECT_PROPERTY_NAME_PREFIX = "project.";
  
    /**
     * The length of the {@link #PROJECT_PROPERTY_NAME_PREFIX project property
     * prefix}.
     * <p>
     * The value of this constant is {@value}.
     * </p>
     */
    private static final int PROJECT_PROPERTY_NAME_PREFIX_LENGTH =
        PROJECT_PROPERTY_NAME_PREFIX.length();
  
    // --- members --------------------------------------------------------------
  
    /**
     * The project to fetch properties from.
     */
    private final MavenProject project;
  
    // ****************************** Initializer *******************************
  
    // ****************************** Constructors ******************************
  
    /**
     * Default constructor.
     *
     * @param project the project to fetch properties from.
     */
    public MavenPropertyHelper(final MavenProject project)
    {
      if (project == null)
      {
        throw new NullPointerException(
            "The property helper requires the project reference to be not 'null'.");
      }
      this.project = project;
    }
  
    // ****************************** Inner Classes *****************************
  
    // ********************************* Methods ********************************
  
    // --- init -----------------------------------------------------------------
  
    // --- get&set --------------------------------------------------------------
  
    // --- business -------------------------------------------------------------
  
    /**
     * Returns the property value specified by the given name.
    *
    * @param name the name of the property to return.
    * @return the property value for the given {@code name}.
    */
   public String getProperty(final String name)
   {
     if (name == null)
     {
       throw new NullPointerException(
           "Name of requested property must not be 'null'");
     }
 
     String value = null;
     if (isProjectProperty(name))
     {
       value = getProjectProperty(name);
     }
     if (value == null)
     {
       value = getPropertiesProperty(name);
     }
     return value;
   }
 
   private boolean isProjectProperty(final String name)
   {
     return name != null && name.length() >= PROJECT_PROPERTY_NAME_PREFIX_LENGTH
            && name.startsWith(PROJECT_PROPERTY_NAME_PREFIX);
   }
 
   /**
    * Returns a property from the project instance.
    */
   private String getProjectProperty(final String name)
   {
     final String projectName =
         name.substring(PROJECT_PROPERTY_NAME_PREFIX_LENGTH);
     if (PropertyUtils.isReadable(project, projectName))
     {
       try
       {
         return getProjectProperty(project, projectName);
       }
       catch (final Exception e)
       {
         throw new IllegalStateException("Cannot access project property '"
                                         + name + "'.");
       }
     }
 
     return null;
   }
 
   private static String getProjectProperty(final MavenProject project,
       final String projectName) throws IllegalAccessException,
     InvocationTargetException, NoSuchMethodException
   {
     if (project != null)
     {
       final Object value = PropertyUtils.getProperty(project, projectName);
       if (value != null)
       {
         return String.valueOf(value);
       }
       else
       {
         return getProjectProperty(project.getParent(), projectName);
       }
     }
     return null;
   }
 
   /**
    * Returns a property from the <code>properties</code> section.
    */
   private String getPropertiesProperty(final String name)
   {
     return getPropertiesProperty(project, name);
   }
 
   private static String getPropertiesProperty(final MavenProject project,
       final String name)
   {
     String value = null;
     final Properties properties = project.getProperties();
     if (properties != null)
     {
       value = properties.getProperty(name);
     }
 
     if (value == null)
     {
       value = getPropertiesPropertyFromParent(project, name);
     }
 
     return value;
   }
 
   private static String getPropertiesPropertyFromParent(
       final MavenProject project, final String name)
   {
     final String value;
     final MavenProject parentProject = project.getParent();
     if (parentProject != null)
     {
       value = getPropertiesProperty(parentProject, name);
     }
     else
     {
       value = null;
     }
     return value;
   }
 
   // --- object basics --------------------------------------------------------
 
 }