content: /*
   *  Licensed to the Apache Software Foundation (ASF) under one
   *  or more contributor license agreements.  See the NOTICE file
   *  distributed with this work for additional information
   *  regarding copyright ownership.  The ASF licenses this file
   *  to you 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.apache.causeway.applib.services.hint;
  
  import java.util.Set;
  
  import org.apache.causeway.applib.services.bookmark.Bookmark;
  
  /**
   * Defines a mechanism for viewers to store arbitrary UI hints on a per-object
   * basis.
   *
   * <p>
   * This store <i>is</i> used by the Wicket viewer.   For example, the viewer
   * remembers which tabs are selected, and for collections which view is
   * selected (eg table or hidden), which page of a table to render, or whether
   * "show all" (rows) is toggled.
   * </p>
   *
   * @since 1.x {@index}
   */
  public interface HintStore {
  
      /**
       * Obtain a hint (eg which tab to open) for a particular object.
       *
       * <p>
       * Object identity is represented by {@link Bookmark} so that alternative
       * implementations can easily serialize this state to a string.
       * </p>
       *
       * @apiNote Object identity is represented by {@link Bookmark} so that
       *          alternative implementations can easily serialize this state to a string.
       *
       * @param bookmark - representing the domain object
       * @param hintKey - the key of the hint
       *
       * @return - the value of the hint, or null.
       */
      String get(final Bookmark bookmark, String hintKey);
  
      /**
       * Set the state of a hint for the domain object
       *
       * @apiNote Object identity is represented by {@link Bookmark} so that
       *          alternative implementations can easily serialize this state to a string.
       *
       * @param bookmark - representing the domain object
       * @param hintKey - the key of the hint
       * @param value - the value of the hint
       */
      void set(final Bookmark bookmark, String hintKey, String value);
  
      /**
       * Removes hint for the domain object.
       *
       * @apiNote Object identity is represented by {@link Bookmark} so that
       *          alternative implementations can easily serialize this state to a string.
       *
       * @param bookmark - representing the domain object
       * @param hintKey - the key of the hint
       */
      void remove(final Bookmark bookmark, String hintKey);
  
      /**
       * Remotes all hints for the domain object.
       *
       * @apiNote Object identity is represented by {@link Bookmark} so that
       *          alternative implementations can easily serialize this state to a string.
       *
       * @param bookmark - representing the domain object
       */
      void removeAll(Bookmark bookmark);
  
      /**
       * The keys of all available hints for the domain object.
       *
       * @apiNote Object identity is represented by {@link Bookmark} so that
       *          alternative implementations can easily serialize this state to a string.
       *
       * @param bookmark - representing the domain object
       */
      Set<String> findHintKeys(Bookmark bookmark);
  
  }
  