package com.atlassian.sal.core.features;
   
   import com.atlassian.sal.api.features.DarkFeatureManager;
   import com.google.common.base.Functions;
   import com.google.common.base.Predicate;
   import com.google.common.collect.Collections2;
   import com.google.common.collect.ImmutableSet;
   import com.google.common.collect.Maps;
   import com.google.common.collect.Sets;
  
  import java.io.File;
  import java.io.FileReader;
  import java.io.IOException;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.Map;
  import java.util.Properties;
  import java.util.Set;
  
  public class SystemDarkFeatureInitializer {
      /**
       * Get the dark features enabled and disabled on startup. Reads from system properties and from a "atlassian-darkfeatures.properties" file.
       * File name can be overridden with darkfeatures.properties.file system property.
       *
       * @return A SystemDarkFeatures containing two sets of strings: one containing enabled dark feature keys and one containing those disabled.
       */
      public static SystemDarkFeatures getSystemStartupDarkFeatures() {
          final String propertiesFile = System.getProperty(DarkFeatureManager.DARKFEATURES_PROPERTIES_FILE_PROPERTY, DarkFeatureManager.DARKFEATURES_PROPERTIES_FILE_PROPERTY_DEFAULT);
  
          final String disableAllPropertiesFlag = System.getProperty(DarkFeatureManager.DISABLE_ALL_DARKFEATURES_PROPERTY);
          if (Boolean.parseBoolean(disableAllPropertiesFlag)) {
              return SystemDarkFeatures.disableAll();
          }
  
          final Set<String> enabledPropertyDarkFeatures = getPropertyDarkFeaturesWithValue(true);
          final Set<String> enabledPropertiesFileDarkFeatures = getPropertiesFileDarkFeatures(propertiesFile, true);
  
          final Set<String> disabledPropertyDarkFeatures = getPropertyDarkFeaturesWithValue(false);
          final Set<String> disabledPropertiesFileDarkFeatures = getPropertiesFileDarkFeatures(propertiesFile, false);
  
          // System properties override property file
          Set<String> enabled = Sets.union(Sets.difference(enabledPropertiesFileDarkFeatures, disabledPropertyDarkFeatures), enabledPropertyDarkFeatures);
          Set<String> disabled = Sets.union(Sets.difference(disabledPropertiesFileDarkFeatures, enabledPropertyDarkFeatures), disabledPropertyDarkFeatures);
  
          return SystemDarkFeatures.darkFeatures(enabled, disabled);
      }
  
      private static Set<String> getPropertiesFileDarkFeatures(String filename, boolean b) {
          final File propertiesFile = new File(filename);
  
          Properties properties = new Properties();
          try {
              properties.load(new FileReader(propertiesFile));
          } catch (IOException e) {
              return Collections.emptySet();
          }
  
          return new HashSet<String>(getKeysForBooleanValue(filterOnAndStripKeyPrefix(properties), b));
      }
  
      private static Set<String> getPropertyDarkFeaturesWithValue(boolean b) {
          return new HashSet<String>(getKeysForBooleanValue(filterOnAndStripKeyPrefix(System.getProperties()), b));
      }
  
      private static Collection<String> getKeysForBooleanValue(final Map<Object, Object> properties, final Boolean b) {
          return Collections2.transform(Maps.filterValues(properties, new Predicate<Object>() {
              @Override
              public boolean apply(Object input) {
                  // don't want to match things with neither true nor false - should be ignored
                  return input.toString().toLowerCase().matches(b.toString());
              }
          }).keySet(), Functions.toStringFunction());
      }
  
      private static Map<Object, Object> filterOnAndStripKeyPrefix(Map<Object, Object> properties) {
          final Set<Map.Entry<Object, Object>> entries = Maps.filterKeys(properties, new Predicate<Object>() {
              @Override
              public boolean apply(Object entry) {
                  return entry.toString().startsWith(DarkFeatureManager.ATLASSIAN_DARKFEATURE_PREFIX);
              }
          }).entrySet();
  
          Map<Object, Object> prefixStrippedEntries = new HashMap<Object, Object>();
          for (Map.Entry<Object, Object> entry : entries) {
              prefixStrippedEntries.put(entry.getKey().toString().substring(DarkFeatureManager.ATLASSIAN_DARKFEATURE_PREFIX.length()), entry.getValue());
          }
  
          return prefixStrippedEntries;
      }
  
      public static class SystemDarkFeatures {
          private final Set<String> enabled;
          private final Set<String> disabled;
          private final boolean disableAll;
  
          private SystemDarkFeatures(Set<String> enabled, Set<String> disabled, boolean disableAll) {
              this.enabled = ImmutableSet.copyOf(enabled);
             this.disabled = ImmutableSet.copyOf(disabled);
             this.disableAll = disableAll;
         }
 
         public static SystemDarkFeatures disableAll() {
             return new SystemDarkFeatures(Collections.<String>emptySet(), Collections.<String>emptySet(), true);
         }
 
         public static SystemDarkFeatures darkFeatures(Set<String> enabled, Set<String> disabled) {
             return new SystemDarkFeatures(enabled, disabled, false);
         }
 
         public Set<String> getEnabled() {
             return enabled;
         }
 
         public Set<String> getDisabled() {
             return disabled;
         }
 
         public boolean isDisableAll() {
             return disableAll;
         }
     }
 }