/*
    * Copyright 2008-2010 Digital Enterprise Research Institute (DERI)
    *
    * 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 org.deri.any23.configuration;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.IOException;
  import java.util.Properties;
  
  /**
   * Default implementation of {@link Configuration}.
   * The default property values are read from the
   * <i>/default-configuration.properties</i> properties file
   * in classpath.
   *
   * @author Michele Mostarda (michele.mostarda@gmail.com)
   */
  public class DefaultConfiguration implements Configuration {
  
      /**
       * Default configuration file.
       */
      public static final String DEFAULT_CONFIG_FILE = "/default-configuration.properties";
  
      public static final String FLAG_PROPERTY_ON  = "on";
  
      public static final String FLAG_PROPERTY_OFF = "off";
  
      protected static final Logger logger = LoggerFactory.getLogger(DefaultConfiguration.class);
  
      protected static final DefaultConfiguration singleton = new DefaultConfiguration();
  
      protected final Properties properties;
  
      /**
       * @return the singleton configuration instance.
       *         Such instance is unmodifiable.
       */
      public static synchronized DefaultConfiguration singleton() {
          return singleton;
      }
  
      /**
       * @return a copy of the singleton instance. such instance is modifiable.
       */
      public static synchronized ModifiableConfiguration copy() {
          final Properties propertiesCopy = (Properties) singleton.properties.clone();
          return new DefaultModifiableConfiguration(propertiesCopy);
      }
  
      private static Properties loadDefaultProperties() {
          final Properties properties = new Properties();
          try {
              properties.load( DefaultConfiguration.class.getResourceAsStream(DEFAULT_CONFIG_FILE) );
          } catch (IOException ioe) {
              throw new IllegalStateException("Error while loading default configuration.", ioe);
          }
          return properties;
      }
  
      protected DefaultConfiguration(Properties properties) {
          this.properties = properties;
      }
  
      private DefaultConfiguration() {
          this( loadDefaultProperties() );
      }
  
      public synchronized String[] getProperties() {
          return properties.keySet().toArray( new String[properties.size()] );
      }
  
      public synchronized boolean defineProperty(String propertyName) {
          return properties.containsKey(propertyName);
      }
  
      public synchronized String getProperty(String propertyName, String defaultValue) {
          final String value = getPropertyValue(propertyName);
          if(value == null) {
              return defaultValue;
          }
          return value;
      }
  
     public synchronized String getPropertyOrFail(String propertyName) {
         final String propertyValue = getPropertyValue(propertyName);
         if(propertyValue == null) {
             throw new IllegalArgumentException("The property '" + propertyName + "' is expected to be declared.");
         }
         if(  propertyValue.trim().length() == 0) {
             throw new IllegalArgumentException(
                     "Invalid value '" + propertyValue + "' for property '" + propertyName + "'"
             );
         }
         return propertyValue;
     }
 
     public synchronized int getPropertyIntOrFail(String propertyName) {
         final String value = getPropertyOrFail(propertyName);
         final String trimValue = value.trim();
         try {
             return Integer.parseInt(trimValue);
         } catch (NumberFormatException nfe) {
             throw new NumberFormatException("The retrieved property is not a valid Integer: '" + trimValue + "'");
         }
     }
 
     public synchronized boolean getFlagProperty(final String propertyName) {
         final String value = getPropertyOrFail(propertyName);
         if(value == null) {
             return false;
         }
         if(FLAG_PROPERTY_ON.equals(value)) {
             return true;
         }
         if(FLAG_PROPERTY_OFF.equals(value)) {
             return false;
         }
         throw new IllegalArgumentException(
                 String.format(
                     "Invalid value [%s] for flag property [%s]. Supported values are %s|%s",
                     value, propertyName, FLAG_PROPERTY_ON, FLAG_PROPERTY_OFF
                 )
         );
     }
 
     public synchronized String getConfigurationDump() {
         final String[] defaultProperties = getProperties();
         final StringBuilder sb = new StringBuilder();
         sb.append("\n======================= Configuration Properties =======================\n");
         for (String defaultProperty : defaultProperties) {
             sb.append(defaultProperty).append('=').append(getPropertyValue(defaultProperty)).append('\n');
         }
         sb.append("========================================================================\n");
         return sb.toString();
     }
 
     private String getPropertyValue(String propertyName) {
         if( ! defineProperty(propertyName) ) {
             if(logger.isDebugEnabled()) {
                 logger.debug(
                         String.format(
                                 "Property '%s' is not declared in default configuration file [%s]",
                                 propertyName,
                                 DEFAULT_CONFIG_FILE
                         )
                 );
             }
             return null;
         }
         final String systemValue = System.getProperties().getProperty(propertyName);
         if(systemValue == null) {
             return properties.getProperty(propertyName);
         }
         return systemValue;
     }
 
 }