/*
 Nutzerverwaltung - A Generic User Manager
 Copyright (c) 2016  Ulrich Hilger

 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU Affero General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU Affero General Public License for more details.

 You should have received a copy of the GNU Affero General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package de.uhilger.um.api;

import de.uhilger.baselink.GenericRecord;
import de.uhilger.baselink.PersistenceManager;
import de.uhilger.baselink.Record;
import de.uhilger.transit.web.WebKontext;
import de.uhilger.um.Digester;
import de.uhilger.um.daten.User;
import de.uhilger.um.daten.UserRole;
import java.sql.Connection;
import java.util.List;
import java.util.Properties;
import javax.servlet.ServletContext;

/**
 * <p>Die Methoden der Klasse UserMgr sind  
 * die 'Fassade', die &uuml;ber Transit als Programmschnittstelle 
 * (Application Programming Interface, API) 
 * nach au&szlig;en bereitgestellt wird. UserMgr dient weitgehend 
 * als 'Durchreiche' f&uuml;r die Funktionalit&auml;t anderer Klassen.</p>
 * 
 * <p>
 * Der UserMgr erh&auml;lt die ben&ouml;tigten Methoden aus dem ServletContext. 
 * Auf diese Weise sind keine statischen Abh&auml;ngigkeiten in den Code 
 * gewandert. Die folgenden Elemente werden vom UserMgr im ServletContext 
 * erwartet:
 * 
 * [noch auspraegen]
 * 
 * PersistenceManager
 * SQL-Properties
 * Digester
 * </p> 
 * 
 * @author Copyright (c) Ulrich Hilger, http://uhilger.de
 * @author Published under the terms and conditions of the
 * <a href="http://www.gnu.org/licenses/agpl-3.0" target="_blank">GNU Affero
 * General Public License</a>
 *
 * @version 2, December 27, 2016
 */
public class UserMgr implements WebKontext {
  
  private ServletContext ctx;
  
  private static final Record UserMapper = new GenericRecord(User.class);
  private static final Record UserRoleMapper = new GenericRecord(UserRole.class);
  
  /** Name, unter dem das Properties-Objekt mit den SQL-Befehlen im ServletContext hinterlegt ist */
  public static final String UM_SQL_PROPERTIES = "umSqlProperties";

  public static final String P_DIGESTER = "digester";

  /** Name, unter dem das Zugriffsobjekt zur Datenbank im ServletContext hinterlegt ist */
  public static final String UM_DB = "umDb";
  
  /** Boolean-Konstante zur Kennzeichnung von Datenbankergebnissen ohne Blobs */
  public static final boolean WITHOUT_BLOBS = false;

  public static final String SQL_GET_USER_LIST = "getUserList";
  public static final String SQL_GET_USER_NAME_LIST = "getUserNameList";
  public static final String SQL_GET_ROLE_LIST = "getRoleList";
  public static final String SQL_GET_USER_ROLES = "getUserRoles";
  public static final String SQL_DELETE_USER = "deleteUser";
  public static final String SQL_DELETE_USER_ROLES = "deleteUserRoles";
  
  /* ----------- Benutzer -------------- */
  
  public User createUser(User user) throws ClassNotFoundException, InstantiationException, IllegalAccessException {
    String kw = user.getPw();
    String digesterClassName = ctx.getInitParameter(P_DIGESTER);
    Digester digester = (Digester) Class.forName(digesterClassName).newInstance();
    String digestedPw = digester.digest(kw, Digester.MD5, null);
    user.setPw(digestedPw);
    getDb().insert(user, UserMapper);
    return user;
  }
  
  public List getUserNameList() {
    return getDb().select(getSql(SQL_GET_USER_NAME_LIST), WITHOUT_BLOBS);
  }
  
  public User deleteUser(User user) {
    PersistenceManager pm = getDb();
    Connection c = pm.getConnection();
    pm.startTransaction(c);
    pm.execute(c, getSql(SQL_DELETE_USER_ROLES), user.getId());
    User deletedUser = (User) pm.delete(c, user, UserMapper);
    pm.commit(c);
    return deletedUser;
  }
    
  /* ------------ Rollen ------------------ */
  
  public UserRole grantRole(String userId, String roleName) {
    UserRole ur = new UserRole();
    ur.setRole(roleName);
    ur.setUser(userId);
    getDb().insert(ur, UserRoleMapper);
    return ur;
  }
  
  public UserRole revokeRole(String userId, String roleName) {
    UserRole ur = new UserRole();
    ur.setRole(roleName);
    ur.setUser(userId);
    getDb().delete(ur, UserRoleMapper);
    return ur;
  }
  
  public List getRoleNamesGranted() {
    return getDb().select(getSql(SQL_GET_ROLE_LIST), WITHOUT_BLOBS);
  }
  
  public List getUserRoleNames(String userId) {
    return getDb().select(getSql(SQL_GET_USER_ROLES), WITHOUT_BLOBS, userId);
  }
  
  /* ----------- Helfer ---- */
  
  /**
   * Ein benanntes SQL-Kommando ermitteln 
   * @param id Name des gewuenschten SQL-Kommandos
   * @return das SQL-Kommando mit der in id angegebenen Bezeichnung 
   */
  private String getSql(String id) {
    Properties sql = (Properties) ctx.getAttribute(UserMgr.UM_SQL_PROPERTIES);
    return sql.getProperty(id);
  }
  
  private PersistenceManager getDb() {
    return (PersistenceManager) ctx.getAttribute(UM_DB);
  }
  
  /* ------------- Implementierung WebKontext ------------- */

  @Override
  public ServletContext getServletContext() {
    return ctx;
  }

  @Override
  public void setServletContext(ServletContext servletContext) {
    this.ctx = servletContext;
  }
  
  
}