/** @file
 * @brief BackendManager subclass for singlefile databases.
 */
/* Copyright (C) 2007,2008,2009,2011,2012,2013,2015,2018,2023 Olly Betts
 * Copyright (C) 2008 Lemur Consulting Ltd
 *
 * 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/>.
 */

#include <config.h>

#include "backendmanager_singlefile.h"

#include "filetests.h"
#include "index_utils.h"
#include "unixcmds.h"

#include <cstdio> // For rename().

using namespace std;

BackendManagerSingleFile::BackendManagerSingleFile(const string& datadir_,
                                                   BackendManager* sub_manager_)
    : BackendManager(datadir_, "singlefile_" + sub_manager_->get_dbtype()),
      sub_manager(sub_manager_),
      cachedir(".singlefile" + sub_manager_->get_dbtype())
{
    // Ensure the directory we store cached test databases in exists.
    (void)create_dir_if_needed(cachedir);
}

string
BackendManagerSingleFile::do_get_database_path(const vector<string> & files)
{
    string db_path = cachedir + "/db";
    for (const string& file : files) {
        db_path += "__";
        db_path += file;
    }

    if (!file_exists(db_path)) {
        // No cached DB exists.  Create at a temporary path and rename
        // so we don't leave a partial DB in place upon failure.
        string tmp_path = db_path + ".tmp";
        sub_manager->get_database(files).compact(tmp_path,
                                                 Xapian::DBCOMPACT_SINGLE_FILE |
                                                 Xapian::DBCOMPACT_NO_RENUMBER);
        if (rename(tmp_path.c_str(), db_path.c_str()) < 0) {
            throw Xapian::DatabaseError("rename failed", errno);
        }
    }

    return db_path;
}

Xapian::WritableDatabase
BackendManagerSingleFile::get_generated_database(const string& name)
{
    // Create generated database inside sub_manager's cache.
    return sub_manager->get_generated_database(name);
}

void
BackendManagerSingleFile::finalise_generated_database(const string& name)
{
    create_dir_if_needed(cachedir);

    // path to the temporary generated db
    string generated_db_path = sub_manager->get_generated_database_path(name);

    // path to final singlefile db
    string path = cachedir + "/" + name;

    // path to tmpfile
    string tmpfile = path + ".tmp";

    // Convert to singlefile db.
    {
        Xapian::Database db(generated_db_path);
        db.compact(tmpfile,
                   Xapian::DBCOMPACT_SINGLE_FILE |
                   Xapian::DBCOMPACT_NO_RENUMBER);
    }

    if (rename(tmpfile.c_str(), path.c_str()) < 0) {
        throw Xapian::DatabaseError("rename failed", errno);
    }
}

Xapian::WritableDatabase
BackendManagerSingleFile::get_writable_database(const string &, const string &)
{
    throw Xapian::UnimplementedError("Single-file databases don't support writing");
}

string
BackendManagerSingleFile::get_generated_database_path(const string& name)
{
    return cachedir + "/" + name;
}

string
BackendManagerSingleFile::get_compaction_output_path(const string& name)
{
    return cachedir + "/" + name;
}
