/*
    * Copyright 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.issue.command;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.Serializable;
  import java.util.List;
  
  import org.apache.commons.httpclient.Header;
  import org.apache.commons.httpclient.HttpMethod;
  import org.apache.commons.httpclient.methods.PostMethod;
  import org.apache.commons.io.IOUtils;
  
  import de.smartics.maven.issue.command.CommandResult.HttpStatus;
  import de.smartics.maven.issue.command.CommandResult.Page;
  import de.smartics.maven.issue.util.Grabber;
  
  /**
   * Base implementation of the {@link Command} interface.
   *
   * @param <T> the concrete type of the command.
   */
  public abstract class AbstractCommand<T extends Command<T>> implements
      Command<T>
  {
    // ********************************* Fields *********************************
  
    // --- constants ------------------------------------------------------------
  
    /**
     * The class version identifier.
     * <p>
     * The value of this constant is {@value}.
     * </p>
     */
    private static final long serialVersionUID = 1L;
  
    // --- members --------------------------------------------------------------
  
    /**
     * The name of the service on the target server.
     *
     * @serial
     */
    protected final String service;
  
    /**
     * The arguments to the command.
     *
     * @serial
     */
    protected final List<CommandArgument<T>> arguments;
  
    /**
     * The result of the command execution. May be <code>null</code> if the
     * command has not been executed yet or if the execution of the command failed
     * without a result.
     *
     * @serial
     */
    protected CommandResult<T> result;
  
    /**
     * The URL to the service that has been called. The value is <code>null</code>
     * if the command was not yet executed.
     *
     * @serial
     */
    protected String url;
  
    // ****************************** Initializer *******************************
  
    // ****************************** Constructors ******************************
  
    /**
     * Default constructor.
     *
     * @param service the name of the service on the target server.
     * @param arguments the arguments to the command.
     */
    protected AbstractCommand(final String service,
        final List<CommandArgument<T>> arguments)
    {
      this.service = service;
      this.arguments = arguments;
   }
 
   // ****************************** Inner Classes *****************************
 
   /**
    * Contains information about the expectations and how they have been met.
    */
   public static final class Expectation implements Serializable
   {
     // ******************************** Fields ********************************
 
     // --- constants ----------------------------------------------------------
 
     /**
      * The class version identifier.
      * <p>
      * The value of this constant is {@value}.
      * </p>
      */
     private static final long serialVersionUID = 1L;
 
     /**
      * Constant for commands that do not check expectations.
      */
     public static final Expectation NO_EXPECTATION = new Expectation(true,
         null, null);
 
     /**
      * Signals that the result is not known to the command. Therefore it is a
      * kind of unexpected result.
      * <p>
      * The value of this constant is {@value}.
      * </p>
      */
     public static final String UNKNOWN_FLAG = "UNEXPECTED";
 
     // --- members ------------------------------------------------------------
 
     /**
      * The flag informs about the fact that the expectations have been met (
      * <code>true</code>) or not (<code>false</code>).
      *
      * @serial
      */
     private final boolean expected;
 
     /**
      * The expected page title.
      *
      * @serial
      */
     private final String expectedPageTitle;
 
     /**
      * The expectation flag that signals the effective result that has been
      * evaluated on the check if the result is as expected. If there is more
      * than one expected result (e.g. to add a component may result in the
      * component being added, recognizing that the component was already added
      * or in some kind of failure) the result of the analysis is stored here for
      * further reference by the command itself.
      *
      * @serial.
      */
     private final String flag;
 
     // ***************************** Initializer ******************************
 
     // ***************************** Constructors *****************************
 
     /**
      * Default constructor.
      *
      * @param expected the flag informs about the fact that the expectations
      *          have been met ( <code>true</code>) or not (<code>false</code>).
      * @param expectedPageTitle the expected page title.
      * @param flag the expectation flag that signals the effective result that
      *          has been evaluated on the check if the result is as expected.
      */
     public Expectation(final boolean expected, final String expectedPageTitle,
         final String flag)
     {
       this.expected = expected;
       this.expectedPageTitle = expectedPageTitle;
       this.flag = flag;
     }
 
     // ***************************** Inner Classes ****************************
 
     // ******************************** Methods *******************************
 
     // --- init ---------------------------------------------------------------
 
     // --- get&set ------------------------------------------------------------
 
     /**
      * Returns the flag informs about the fact that the expectations have been
      * met ( <code>true</code>) or not (<code>false</code>).
      *
      * @return the flag informs about the fact that the expectations have been
      *         met ( <code>true</code>) or not (<code>false</code>).
      */
     public boolean isExpected()
     {
       return expected;
     }
 
     /**
      * Returns the expected page title.
      *
      * @return the expected page title.
      */
     public String getExpectedPageTitle()
     {
       return expectedPageTitle;
     }
 
     /**
      * Returns the expectation flag that signals the effective result that has
      * been evaluated on the check if the result is as expected. If there is
      * more than one expected result (e.g. to add a component may result in the
      * component being added, recognizing that the component was already added
      * or in some kind of failure) the result of the analysis is stored here for
      * further reference by the command itself.
      *
      * @return the expectation flag that signals the effective result that has
      *         been evaluated on the check if the result is as expected.
      */
     public String getFlag()
     {
       return flag;
     }
 
     // --- business -----------------------------------------------------------
 
     // --- object basics ------------------------------------------------------
   }
 
   // ********************************* Methods ********************************
 
   // --- init -----------------------------------------------------------------
 
   /**
    * Helper to construct an URL to call a service on the target.
    *
    * @return the created URL.
    */
   private String createUrl(final CommandTarget target)
   {
     final String targetUrl = target.getUrl();
     final StringBuilder buffer = new StringBuilder(128);
     buffer.append(targetUrl).append('/').append(service);
     return buffer.toString();
   }
 
   // --- get&set --------------------------------------------------------------
 
   /**
    * Returns the result of the command execution. May be <code>null</code> if
    * the command has not been executed yet or if the execution of the command
    * failed without a result.
    *
    * @return the result of the command execution.
    */
   @Override
   public final CommandResult<T> getResult()
   {
     return result;
   }
 
   // --- business -------------------------------------------------------------
 
   /**
    * Creates the method to be executed with a HTTP client.
    *
    * @return the method to be executed with a HTTP client.
    */
   private HttpMethod createMethod()
   {
     final PostMethod method = new PostMethod(url);
 
     for (final CommandArgument<?> argument : arguments)
     {
       // FIXME: Ugly API argument.getName().getName()
       final String name = argument.getName().getName();
       final String value = argument.getValue();
       if (value != null)
       {
         method.addParameter(name, value);
       }
     }
 
     return method;
   }
 
   /**
    * {@inheritDoc}
    *
    * @see de.smartics.maven.issue.command.AddVersionCommand#execute()
    */
   @Override
   public final CommandResult<T> execute(final CommandTarget target)
     throws CommandException
   {
     if (url != null)
     {
       throw new CommandException("Command has already been executed: " + url);
     }
 
     url = createUrl(target);
     final HttpMethod method = createMethod();
     final int code = target.execute(method);
 
     final String pageContent = readPageContent(method);
 
     final HttpStatus httpStatus = createStatus(method);
 
     result = createResult(code, pageContent, httpStatus);
     return result;
   }
 
   /**
    * Returns the command argument with the specified name.
    *
    * @param parameter the paramter that defines the name of the requested
    *          argument.
    * @return the requested argument.
    */
   protected final CommandArgument<T> getArgument(
       final CommandParameter<T> parameter)
   {
     for (final CommandArgument<T> argument : arguments)
     {
       if (parameter.equals(argument.getName()))
       {
         return argument;
       }
     }
 
     throw new IllegalArgumentException("Command '" + this.url
                                        + "' does not know parameter '"
                                        + parameter + "'.");
   }
 
   // --- object basics --------------------------------------------------------
 
   private HttpStatus createStatus(final HttpMethod method)
   {
     final int code = method.getStatusCode();
     final String text = method.getStatusText();
     final HttpStatus httpStatus = new HttpStatus(code, text);
     return httpStatus;
   }
 
   // CHECKSTYLE:OFF
   /**
    * Override if token should be read.
    *
    * @return <code>true</code> if token is required to be read from response,
    *         <code>false</code> (the default) otherwise.
    */
   protected boolean isTokenRequiredToRead() // CHECKSTYLE:ON
   {
     return false;
   }
 
   private CommandResult<T> createResult(final int code,
       final String pageContent, final HttpStatus httpStatus)
   {
     final Grabber grabber = new Grabber(pageContent);
     final String title = grabber.grabTitle();
     final String token = grabber.grabToken();
 
     final CommandResult.Page page =
         new CommandResult.Page(token, title, pageContent);
     final Expectation expectation = checkExpectation(page);
     final String description = getCommandResultDescription(page, expectation);
     return new CommandResult<T>(code, httpStatus, description, page,
         expectation);
   }
 
   /**
    * Returns the description to the result. This description explains what
    * happened in a short sentence. This is the essence of the command's result.
    * The description of a command result may be <code>null</code>, if the
    * command has no substantial result. A non-substantial result, which
    * justifies a value of <code>null</code>, would be a navigation command to a
    * certain page.
    *
    * @param page the resulting page to be analyzed to create the correct
    *          description.
    * @param expecation information about the analyzed result.
    * @return the description to the result.
    */
   protected abstract String getCommandResultDescription(final Page page,
       final Expectation expecation);
 
   /**
    * Analyzes the returned page and returns the expectation report.
    *
    * @param page the returned page to check.
    * @return the report on the check.
    */
   protected abstract Expectation checkExpectation(final Page page);
 
   private String readPageContent(final HttpMethod method)
   {
     InputStream input = null;
     try
     {
       input = method.getResponseBodyAsStream();
       final String encoding = getEncoding(method);
       final String page = IOUtils.toString(input, encoding);
       return page;
     }
     catch (final IOException e)
     {
       throw new CommandException("Problems reading page.", e);
     }
     finally
     {
       IOUtils.closeQuietly(input);
     }
   }
 
   private String getEncoding(final HttpMethod method)
   {
     final Header header = method.getResponseHeader("Content-Type");
     if (header != null)
     {
       final String pattern = "; charset=";
       final String value = header.getValue();
       final int delimiterIndex = value.lastIndexOf(pattern);
       if (delimiterIndex != -1)
       {
         final int start = delimiterIndex + pattern.length();
         if (start < value.length() - 1) // NOPMD
         {
           final String encoding = value.substring(start).trim();
           return encoding;
         }
       }
     }
     return null;
   }
 
   // CHECKSTYLE:OFF
   /**
    * {@inheritDoc}
    *
    * @see java.lang.Object#toString()
    */
   @Override
   public String toString() // CHECKSTYLE:ON
   {
     final StringBuilder buffer = new StringBuilder(128);
 
     if (url != null)
     {
       buffer.append(url);
     }
 
     for (final CommandArgument<?> argument : arguments)
     {
       buffer.append("\n  ").append(argument);
     }
 
     return buffer.toString();
   }
 }