/*
 * Copyright (C) 2021 Maneesh P M <manu.pm55@gmail.com>
 * Copyright (C) 2017-2021 Matthieu Gautier <mgautier@kymeria.fr>
 * Copyright (C) 2007 Tommi Maekitalo
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * is provided AS IS, WITHOUT ANY WARRANTY; without even the implied
 * warranty of MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, and
 * NON-INFRINGEMENT.  See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 *
 */

#ifndef ZIM_SUGGESTION_H
#define ZIM_SUGGESTION_H

#include "suggestion_iterator.h"
#include "archive.h"

#if defined( LIBZIM_WITH_XAPIAN )
namespace Xapian {
class Enquire;
class MSet;
}; // namespace Xapian
#endif

namespace zim {

class SuggestionSearcher;
class SuggestionSearch;
class SuggestionIterator;
class SuggestionDataBase;

/**
 * A SuggestionSearcher is a object suggesting over titles of an Archive
 *
 * A SuggestionSearcher is mainly used to create new `SuggestionSearch`
 * Internaly, this is a wrapper around a SuggestionDataBase with may or may not
 * include a Xapian index.
 *
 * You should consider that all search operations are NOT threadsafe.
 * It is up to you to protect your calls to avoid race competition.
 * However, SuggestionSearcher (and subsequent classes) do not maintain a global/
 * share state You can create several Searchers and use them in different threads.
 */
class LIBZIM_API SuggestionSearcher
{
public:
  /** SuggestionSearcher constructor.
     *
     * Construct a SuggestionSearcher on top of an archive.
     *
     * @param archive An archive to suggest on.
     */
  explicit SuggestionSearcher( const Archive & archive );

  SuggestionSearcher( const SuggestionSearcher & other );
  SuggestionSearcher & operator=( const SuggestionSearcher & other );
  SuggestionSearcher( SuggestionSearcher && other );
  SuggestionSearcher & operator=( SuggestionSearcher && other );
  ~SuggestionSearcher();

  /** Create a SuggestionSearch for a specific query.
     *
     * The search is made on the archive under the SuggestionSearcher.
     *
     * @param query The SuggestionQuery to search.
     */
  SuggestionSearch suggest( const std::string & query );

  /** Set the verbosity of search operations.
     *
     * @param verbose The verbose mode to set
     */
  void setVerbose( bool verbose );

private: // methods
  void initDatabase();

private: // data
  std::shared_ptr< SuggestionDataBase > mp_internalDb;
  Archive m_archive;
  bool m_verbose;
};

/**
 * A SuggestionSearch represent a particular suggestion search, based on a `SuggestionSearcher`.
 */
class LIBZIM_API SuggestionSearch
{
public:
  SuggestionSearch( SuggestionSearch && s );
  SuggestionSearch & operator=( SuggestionSearch && s );
  ~SuggestionSearch();

  /** Get a set of results for this search.
         *
         * @param start The begining of the range to get
         *              (offset of the first result).
         * @param maxResults The maximum number of results to return
         *                   (offset of last result from the start of range).
         */
  const SuggestionResultSet getResults( int start, int maxResults ) const;

  /** Get the number of estimated results for this suggestion search.
         *
         * As the name suggest, it is a estimation of the number of results.
         */
  int getEstimatedMatches() const;

private: // methods
  SuggestionSearch( std::shared_ptr< SuggestionDataBase > p_internalDb, const std::string & query );

private: // data
  std::shared_ptr< SuggestionDataBase > mp_internalDb;
  std::string m_query;

  friend class SuggestionSearcher;

#ifdef ZIM_PRIVATE

public:
  // Close Xapian db to force range based search
  const void forceRangeSuggestion();
#endif

// Xapian based methods and data
#if defined( LIBZIM_WITH_XAPIAN )

private: // Xapian based methods
  Xapian::Enquire & getEnquire() const;

private: // Xapian based data
  mutable std::unique_ptr< Xapian::Enquire > mp_enquire;
#endif // LIBZIM_WITH_XAPIAN
};

/**
 * The `SuggestionResultSet` represent a range of results corresponding to a `SuggestionSearch`.
 *
 * It mainly allows to get a iterator either based on an MSetIterator or a RangeIterator.
 */
class LIBZIM_API SuggestionResultSet
{
public:
  typedef SuggestionIterator iterator;
  typedef Archive::EntryRange< EntryOrder::titleOrder > EntryRange;

  /** The begin iterator on the result range. */
  iterator begin() const;

  /** The end iterator on the result range. */
  iterator end() const;

  /** The size of the SearchResult (end()-begin()) */
  int size() const;

private: // data
  std::shared_ptr< SuggestionDataBase > mp_internalDb;
  std::shared_ptr< EntryRange > mp_entryRange;

private:
  SuggestionResultSet( EntryRange entryRange );

  friend class SuggestionSearch;

// Xapian based methods and data
#if defined( LIBZIM_WITH_XAPIAN )

private: // Xapian based methods
  SuggestionResultSet( std::shared_ptr< SuggestionDataBase > p_internalDb, Xapian::MSet && mset );

private: // Xapian based data
  std::shared_ptr< Xapian::MSet > mp_mset;

#endif // LIBZIM_WITH_XAPIAN
};

} // namespace zim

#endif // ZIM_SUGGESTION_H