/** @file
 * @brief Synonym data for a glass database.
 */
/* Copyright (C) 2005,2007,2008,2009,2011,2014,2016,2017,2024 Olly Betts
 *
 * 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 WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  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, see
 * <https://www.gnu.org/licenses/>.
 */

#ifndef XAPIAN_INCLUDED_GLASS_SYNONYM_H
#define XAPIAN_INCLUDED_GLASS_SYNONYM_H

#include <xapian/types.h>

#include "backends/alltermslist.h"
#include "glass_lazytable.h"
#include "api/termlist.h"

#include <functional>
#include <set>
#include <string>
#include <string_view>

class GlassDatabase;

namespace Glass {
    class RootInfo;
}
using Glass::RootInfo;

class GlassSynonymTable : public GlassLazyTable {
    /// The last term which was updated.
    mutable std::string last_term;

    /// The synonyms for the last term which was updated.
    mutable std::set<std::string, std::less<>> last_synonyms;

  public:
    /** Create a new GlassSynonymTable object.
     *
     *  This method does not create or open the table on disk - you
     *  must call the create() or open() methods respectively!
     *
     *  @param dbdir            The directory the glass database is stored in.
     *  @param readonly         true if we're opening read-only, else false.
     */
    GlassSynonymTable(const std::string & dbdir, bool readonly)
        : GlassLazyTable("synonym", dbdir + "/synonym.", readonly) { }

    GlassSynonymTable(int fd, off_t offset_, bool readonly)
        : GlassLazyTable("synonym", fd, offset_, readonly) { }

    // Merge in batched-up changes.
    void merge_changes();

    // Discard batched-up changes.
    void discard_changes() {
        last_term.resize(0);
        last_synonyms.clear();
    }

    /** Add a synonym for @a term.
     *
     *  If the synonym has already been added, no action is taken.
     */
    void add_synonym(std::string_view term, std::string_view synonym);

    /** Remove a synonym for @a term.
     *
     *  If the synonym doesn't exist, no action is taken.
     */
    void remove_synonym(std::string_view term, std::string_view synonym);

    /** Remove all synonyms for @a term.
     *
     *  If @a term has no synonyms, no action is taken.
     */
    void clear_synonyms(std::string_view term);

    /** Open synonym termlist for a term.
     *
     *  If @a term has no synonyms, NULL is returned.
     */
    TermList* open_termlist(std::string_view term);

    /** Override methods of GlassTable.
     *
     *  NB: these aren't virtual, but we always call them on the subclass in
     *  cases where it matters.
     *  @{
     */

    bool is_modified() const {
        return !last_term.empty() || GlassTable::is_modified();
    }

    void flush_db() {
        merge_changes();
        GlassTable::flush_db();
    }

    void cancel(const RootInfo & root_info, glass_revision_number_t rev) {
        discard_changes();
        GlassTable::cancel(root_info, rev);
    }

    // @}
};

class GlassCursor;

class GlassSynonymTermList : public AllTermsList {
    /// Copying is not allowed.
    GlassSynonymTermList(const GlassSynonymTermList &);

    /// Assignment is not allowed.
    void operator=(const GlassSynonymTermList &);

    /// Keep a reference to our database to stop it being deleted.
    Xapian::Internal::intrusive_ptr<const GlassDatabase> database;

    /** A cursor which runs through the synonym table reading termnames from
     *  the keys.
     */
    GlassCursor * cursor;

    /// The prefix to restrict the terms to.
    string prefix;

  public:
    GlassSynonymTermList(Xapian::Internal::intrusive_ptr<const GlassDatabase> database_,
                         GlassCursor * cursor_,
                         std::string_view prefix_)
            : database(database_), cursor(cursor_), prefix(prefix_)
    {
        // Position the cursor on the highest key before the first key we want,
        // so that the first call to next() will put us on the first key we
        // want.
        if (prefix.empty()) {
            cursor->rewind();
        } else {
            // Seek to the first key before one with the desired prefix.
            cursor->find_entry_lt(prefix);
        }
    }

    /// Destructor.
    ~GlassSynonymTermList();

    Xapian::termcount get_approx_size() const;

    /// Return the term frequency for the term at the current position.
    Xapian::doccount get_termfreq() const;

    /// Advance to the next term in the list.
    TermList * next();

    /// Advance to the first term which is >= @a term.
    TermList* skip_to(std::string_view term);
};

#endif // XAPIAN_INCLUDED_GLASS_SYNONYM_H
