package com.atlassian.sal.api.page;
   
   import com.google.common.base.Function;
   import com.google.common.base.Joiner;
   import com.google.common.base.Predicates;
   import com.google.common.collect.Collections2;
   import com.google.common.collect.Lists;
   
   import javax.annotation.Nonnull;
  import javax.annotation.Nullable;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.EnumSet;
  
  /**
   * Util class for creating empty enum set, parsing string and valueOf function
   */
  public abstract class PageCapabilities {
  
      public static final String SEPARATOR = ",";
  
      /**
       * @return Empty EnumSet
       */
      public static EnumSet<PageCapability> empty() {
          return EnumSet.noneOf(PageCapability.class);
      }
  
      /**
       * @param values {@code String} page capability names separated with {@link #SEPARATOR}
       * @return {@link java.util.EnumSet} of {@link com.atlassian.sal.api.page.PageCapability}
       * @throws IllegalArgumentException if any of parsed values is invalid
       */
      public static EnumSet<PageCapability> valueOf(@Nullable String values) {
          if (values == null || values.length() == 0) {
              return empty();
          }
  
          final Collection<PageCapability> capabilities = Collections2.filter(Lists.transform(Arrays.asList(values.split(SEPARATOR)), new Function<String, PageCapability>() {
              @Override
              public PageCapability apply(final String value) {
                  try {
                      return PageCapability.valueOf(value);
                  } catch (IllegalArgumentException e) {
                      return null;
                  }
              }
          }), Predicates.notNull());
  
          if (capabilities.isEmpty()) {
              return empty();
          }
  
          return EnumSet.<PageCapability>copyOf(capabilities);
      }
  
      /**
       * @param pageCaps enum set
       * @return Page capabilities separated with {@link #SEPARATOR}
       */
      public static String toString(@Nonnull EnumSet<PageCapability> pageCaps) {
          return Joiner.on(SEPARATOR).join(pageCaps.iterator());
      }
  }