catalogsdb.h

/*
    SPDX-FileCopyrightText: 2021 Valentin Boettcher <hiro at protagon.space; @hiro98:tchncs.de>
 
    SPDX-License-Identifier: GPL-2.0-or-later
*/
 
#pragma once
 
#include <QSqlDatabase>
#include <QSqlError>
#include <exception>
#include <list>
#include <QString>
#include <QList>
#include <catalogsdb_debug.h>
#include <QSqlQuery>
#include <QMutex>
#include <QObject>
#include <QThread>
 
#include "polyfills/qstring_hash.h"
#include <unordered_map>
#include <queue>
 
#include <unordered_set>
#include <utility>
#include "catalogobject.h"
#include "nan.h"
#include "typedef.h"
 
namespace CatalogsDB
{
/**
 * A simple struct to hold information about catalogs.
 */
struct Catalog
{
    /**
     * The catalog id.
     */
    int id = -1;
 
    /**
     * The catalog mame.
     */
    QString name = "Unknown";
 
    /**
     * The precedence level of a catalog.
     *
     * If doublicate objects exist in the database, the one from the
     * catalog with the highest precedence winns.
     */
    double precedence = 0;
 
    /**
     * The author of the catalog.
     */
    QString author = "";
 
    /**
     * The catalog source.
     */
    QString source = "";
 
    /**
     * A (short) description for the catalog.
     * QT html is allowed.
     */
    QString description = "";
 
    /**
     * Wether the catalog is mutable.
     */
    bool mut = false;
 
    /**
     * Wether the catalog is enabled.
     */
    bool enabled = false;
 
    /**
     * The catalog version.
     */
    int version = -1;
 
    /**
     * The catalog color in the form `[default color];[scheme file
     * name];[color]...`.
     */
    QString color = "";
 
    /**
     * The catalog license.
     */
    QString license = "";
 
    /**
     * The catalog maintainer.
     */
    QString maintainer = "";
 
    /**
     * Build time of the catalog. Usually only catalogs with the same
     * timestamp can be considered dedublicated.
     *
     * A `null` timestamp indicates that the catalog has not been
     * built by the catalog repository.
     */
    QDateTime timestamp{};
};
 
const Catalog cat_defaults{};
 
/**
 * Holds statistical information about the objects in a catalog.
 */
struct CatalogStatistics
{
    std::map<SkyObject::TYPE, int> object_counts;
    int total_count = 0;
};
 
const QString db_file_extension = "kscat";
constexpr int application_id    = 0x4d515158;
constexpr int custom_cat_min_id = 1000;
constexpr int user_catalog_id   = 0;
constexpr float default_maglim  = 99;
const QString flux_unit         = "mag";
const QString flux_frequency    = "400 nm";
using CatalogColorMap           = std::map<QString, QColor>;
using ColorMap                  = std::map<int, CatalogColorMap>;
using CatalogObjectList         = std::list<CatalogObject>;
using CatalogObjectVector       = std::vector<CatalogObject>;
 
/**
 * \returns A hash table of the form `color scheme: color` by
 * parsing a string of the form `[default color];[scheme file
 * name];[color]...`.
 */
CatalogColorMap parse_color_string(const QString &str);
 
/**
 * \returns A color string of the form`[default color];[scheme file
 * name];[color]...`.
 *
 * The inverse of `CatalogsDB::parse_color_string`.
 */
QString to_color_string(CatalogColorMap colors);
 
/**
 * Manages the catalog database and provides an interface to provide an
 * interface to query and modify the database. For more information on
 * how the catalog database system works see the KStars Handbook.
 *
 * The class manages a database connection which is assumed to be
 * working (invariant). If the database can't be accessed a
 * DatabaseError is thrown upon construction. The manager is designed
 * to hold as little state as possible because the database should be
 * the single source of truth. Prepared statements are made class
 * members, only if they are performance critical.
 *
 * Most methods in this class are thread safe.
 *
 * The intention is that you access a/the catalogs database directly
 * locally in the code where objects from the database are required and
 * not through layers of references and pointers.
 *
 * The main DSO database can be accessed as follows:
 * ```cpp
 * CatalogsDB::DBManager manager{ CatalogsDB::dso_db_path() };
 * for(auto& o : manager.get_objects(10)) {
 *     // do something
 * }
 * ```
 *
 * To query the database, first check if the required query is already
 * hardcoded into the `DBManager`. If this is not the case you can either
 * add it (if it is performance critical and executed frequently) or use
 * `DBManager::general_master_query` to construct a custom `SQL` query.
 */
class DBManager
{
  public:
    /**
     * Constructs a database manager from the \p filename which is
     * resolved to a path in the kstars data directory.
     *
     * The constructor resolves the path to the database, opens it
     * (throws if that does not work), checks the database version
     * (throws if that does not match), initializes the database,
     * registers the user catalog and updates the all_catalog_view.
     */
    DBManager(const QString &filename);
    DBManager(const DBManager &other);
 
    DBManager &operator=(DBManager other)
    {
        using std::swap;
        DBManager tmp{ other };
 
        m_db_file = other.m_db_file;
        swap(m_db, other.m_db);
        swap(m_q_cat_by_id, other.m_q_cat_by_id);
        swap(m_q_obj_by_trixel, other.m_q_obj_by_trixel);
        swap(m_q_obj_by_trixel_no_nulls, other.m_q_obj_by_trixel_no_nulls);
        swap(m_q_obj_by_trixel_null_mag, other.m_q_obj_by_trixel_null_mag);
        swap(m_q_obj_by_name, other.m_q_obj_by_name);
        swap(m_q_obj_by_name_exact, other.m_q_obj_by_name_exact);
        swap(m_q_obj_by_lim, other.m_q_obj_by_lim);
        swap(m_q_obj_by_maglim, other.m_q_obj_by_maglim);
        swap(m_q_obj_by_maglim_and_type, other.m_q_obj_by_maglim_and_type);
        swap(m_q_obj_by_oid, other.m_q_obj_by_oid);
 
        return *this;
    };
 
    ~DBManager()
    {
        m_db.commit();
        m_db.close();
    }
 
    /**
     * @return the filename of the database
     */
    const QString &db_file_name() const { return m_db_file; };
 
    /**
     * @return wether the catalog with the \p id has been found and
     * the catalog.
     *
     * @todo use std::optional when transitioning to c++17
     */
    const std::pair<bool, Catalog> get_catalog(const int id);
 
    /**
     * \return a vector with all catalogs from the database. If \p
     * include_disabled is `true`, disabled catalogs will be included.
     */
    const std::vector<Catalog> get_catalogs(bool include_disabled = false);
 
    /**
     * @return true if the catalog with \p id exists
     *
     * @todo use std::optional when transitioning to c++17
     */
    bool catalog_exists(const int id);
 
    /**
     * @return return a vector of objects in the trixel with \p id.
     */
    inline CatalogObjectVector get_objects_in_trixel(const int trixel) {
        return _get_objects_in_trixel_generic(m_q_obj_by_trixel, trixel);
    }
 
    /**
     * @return return a vector of objects of known mag in the trixel with \p id.
     */
    inline CatalogObjectVector get_objects_in_trixel_no_nulls(const int trixel) {
        return _get_objects_in_trixel_generic(m_q_obj_by_trixel_no_nulls, trixel);
    }
 
    /**
     * @return return a vector of objects of unknown mag in the trixel with \p id.
     */
    inline CatalogObjectVector get_objects_in_trixel_null_mag(const int trixel) {
        return _get_objects_in_trixel_generic(m_q_obj_by_trixel_null_mag, trixel);
    }
 
    /**
     * \brief Find an objects by name.
     *
     * This will search the `name`, `long_name` and `catalog_identifier`
     * fields in all enabled catalogs for \p `name` and then return a new
     * instance of `CatalogObject` sourced from the master catalog.
     *
     * \param limit Upper limit to the quanitity of results. `-1` means "no
     * limit"
     * \param exactMatchOnly If true, the supplied name must match exactly
     *
     * \return a list of matching objects
     */
    CatalogObjectList find_objects_by_name(const QString &name, const int limit = -1,
                                           const bool exactMatchOnly = false);
 
    /**
     * \brief Find an objects by name in the catalog with \p `catalog_id`.
     *
     * \return a list of matching objects
     */
    CatalogObjectList find_objects_by_name(const int catalog_id, const QString &name,
                                           const int limit = -1);
 
    /**
     * \brief Find an objects by searching the name four wildcard. See
     * the LIKE sqlite statement.
     *
     * \return a list of matching objects
     */
    CatalogObjectList find_objects_by_wildcard(const QString &wildcard,
                                               const int limit = -1);
    /**
     * \brief Find an objects by searching the master catlog with a
     * query like `SELECT ... FROM master WHERE \p where ORDER BY \p
     * order_by ...`.
     *
     * To be used if performance does not matter (much).
     * \p order_by can be ommitted.
     *
     * \return wether the query was successful, an error message if
     * any and a list of matching objects
     */
    std::tuple<bool, const QString, CatalogObjectList>
    general_master_query(const QString &where, const QString &order_by = "",
                         const int limit = -1);
 
    /**
     * \brief Get an object by \p `oid`. Optinally a \p `catalog_id` can be speicfied.
     *
     * \returns if the object was found and the object itself
     */
    std::pair<bool, CatalogObject> get_object(const CatalogObject::oid &oid);
    std::pair<bool, CatalogObject> get_object(const CatalogObject::oid &oid,
                                              const int catalog_id);
 
    /**
     * Get \p limit objects with magnitude smaller than \p maglim (smaller =
     * brighter) from the database.
     */
    CatalogObjectList get_objects(float maglim = default_maglim, int limit = -1);
 
    /**
     * Get all objects from the database.
     */
    CatalogObjectList get_objects_all();
 
    /**
     * Get \p limit objects of \p type with magnitude smaller than \p
     * maglim (smaller = brighter) from the database. Optionally one
     * can filter by \p `catalog_id`.
     */
    CatalogObjectList get_objects(SkyObject::TYPE type, float maglim = default_maglim,
                                  int limit = -1);
    /**
     * Get \p limit objects from the catalog with \p `catalog_id` of
     * \p type with magnitude smaller than \p maglim (smaller =
     * brighter) from the database. Optionally one can filter by \p
     * `catalog_id`.
     */
    CatalogObjectList get_objects_in_catalog(SkyObject::TYPE type, const int catalog_id,
                                             float maglim = default_maglim,
                                             int limit    = -1);
 
    /**
     * @return return the htmesh level used by the catalog db
     */
    int htmesh_level() const { return m_htmesh_level; };
 
    /**
     * \brief Enable or disable a catalog.
     * \return `true` in case of succes, `false` and an error message in case
     * of an error
     *
     * This will recreate the master table.
     */
    std::pair<bool, QString> set_catalog_enabled(const int id, const bool enabled);
 
    /**
     * \brief remove a catalog
     * \return `true` in case of succes, `false` and an error message
     * in case of an error
     *
     * This will recreate the master table.
     */
    std::pair<bool, QString> remove_catalog(const int id);
 
    /**
     * Add a `CatalogObject` to a table with \p `catalog_id`. For the rest of
     * the arguments see `CatalogObject::CatalogObject`.
     *
     * \returns wether the operation was successful and if not, an error
     * message
     */
    std::pair<bool, QString> add_object(const int catalog_id, const SkyObject::TYPE t,
                                        const CachingDms &r, const CachingDms &d,
                                        const QString &n, const float m = NaN::f,
                                        const QString &lname              = QString(),
                                        const QString &catalog_identifier = QString(),
                                        const float a = 0.0, const float b = 0.0,
                                        const double pa = 0.0, const float flux = 0);
 
    /**
     * Add the \p `object` to a table with \p `catalog_id`. For the
     * rest of the arguments see `CatalogObject::CatalogObject`.
     *
     * \returns wether the operation was successful and if not, an
     * error message
     */
    std::pair<bool, QString> add_object(const int catalog_id, const CatalogObject &obj);
 
    /**
     * Add the \p `objects` to a table with \p `catalog_id`. For the
     * rest of the arguments see `CatalogObject::CatalogObject`.
     *
     * \returns wether the operation was successful and if not, an
     * error message
     */
    std::pair<bool, QString> add_objects(const int catalog_id,
                                         const CatalogObjectVector &objects);
 
    /**
     * Remove the catalog object with the \p `oid` from the catalog with the
     * \p `catalog_id`.
     *
     * Refreshes the master catalog.
     *
     * \returns wether the operation was successful and if not, an
     * error message
     */
    std::pair<bool, QString> remove_object(const int catalog_id,
                                           const CatalogObject::oid &id);
 
    /**
     * Dumps the catalog with \p `id` into the file under the path \p
     * `file_path`.  This file can then be imported with
     * `import_catalog`.  If the file already exists, it will be
     * overwritten.
     *
     * The `user_version` and `application_id` pragmas are set to special
     * values, but otherwise the dump format is equal to the internal
     * database format.
     *
     * \returns wether the operation was successful and if not, an error
     * message
     */
    std::pair<bool, QString> dump_catalog(int catalog_id, QString file_path);
 
    /**
     * Loads a dumped catalog from path \p `file_path`. Will overwrite
     * an existing catalog if \p `overwrite` is set to true. Immutable
     * catalogs are overwritten by default.
     *
     * Checks if the pragma `application_id` matches
     * `CatalogsDB::application_id` and the pragma `user_version` to match
     * the database format version.
     *
     * \returns wether the operation was successful and if not, an error
     * message
     */
    std::pair<bool, QString> import_catalog(const QString &file_path,
                                            const bool overwrite = false);
    /**
     * Registers a new catalog in the database.
     *
     * For the parameters \sa Catalog. The catalog gets inserted into
     * `m_catalogs`. The `all_catalog_view` is updated.
     *
     * \return true in case of success, false in case of an error
     * (along with the error)
     */
    std::pair<bool, QString>
    register_catalog(const int id, const QString &name, const bool mut,
                     const bool enabled, const double precedence,
                     const QString &author      = cat_defaults.author,
                     const QString &source      = cat_defaults.source,
                     const QString &description = cat_defaults.description,
                     const int version          = cat_defaults.version,
                     const QString &color       = cat_defaults.color,
                     const QString &license     = cat_defaults.license,
                     const QString &maintainer  = cat_defaults.maintainer,
                     const QDateTime &timestamp = cat_defaults.timestamp);
 
    std::pair<bool, QString> register_catalog(const Catalog &cat);
 
    /**
     * Update the metatadata \p `catalog`.
     *
     * The updated fields are: title, author, source, description.
     *
     * \return true in case of success, false in case of an error
     * (along with the error).
     */
    std::pair<bool, QString> update_catalog_meta(const Catalog &cat);
 
    /**
     * Clone objects from the catalog with \p `id_1` to another with `id_2`. Useful to create a
     * custom catalog from an immutable one.
     */
    std::pair<bool, QString> copy_objects(const int id_1, const int id_2);
 
    /**
     * Finds the smallest free id for a catalog.
     */
    int find_suitable_catalog_id();
 
    /**
     * \returns statistics about the master catalog.
     */
    const std::pair<bool, CatalogStatistics> get_master_statistics();
 
    /**
     * \returns statistics about the catalog with \p `catalog_id`.
     */
    const std::pair<bool, CatalogStatistics> get_catalog_statistics(const int catalog_id);
 
    /**
     * Compiles the master catalog by merging the individual catalogs based
     * on `oid` and precedence and creates an index by (trixel, magnitude) on
     * the master table. **Caution** you may want to call
     * `update_catalog_views` beforhand.
     *
     * @return true in case of success, false in case of an error
     */
    bool compile_master_catalog();
 
    /**
     * Updates the all_catalog_view so that it includes all known
     * catalogs.
     *
     * @return true in case of success, false in case of an error
     */
    bool update_catalog_views();
 
    /** \returns the catalog colors as a hash table of the form `catalog id:
     *  scheme: color`.
     *
     *  The colors are loaded from the `Catalog::color` field and the
     *  `SqlStatements::color_table` in that order.
     */
    ColorMap get_catalog_colors();
 
    /** \returns the catalog colors as a hash table of for the catalog
     * with \p id in the form `scheme: color`.
     *
     *  The colors are loaded from the `Catalog::color` field and the
     *  `SqlStatements::color_table` in that order.
     */
    CatalogColorMap get_catalog_colors(const int id);
 
    /** Saves the configures colors of the catalog with id \p id in \p
     * colors into the database.  \returns wether the insertion was
     * possible and an error message if not.
     */
    std::pair<bool, QString> insert_catalog_colors(const int id,
                                                   const CatalogColorMap &colors);
 
  private:
    /**
     * The backing catalog database.
     */
    QSqlDatabase m_db;
 
    /**
     * The filename of the database.
     *
     * Will be a reference to a member of `m_db_paths`.
     */
    std::reference_wrapper<const QString> m_db_file;
 
    //@{
    /**
     * Some performance criticall sql queries are prepared stored as memebers.
     * When using those queries `m_mutex` should be locked!
     *
     * \sa prepare_queries
     */
 
    QSqlQuery m_q_cat_by_id;
    QSqlQuery m_q_obj_by_trixel;
    QSqlQuery m_q_obj_by_trixel_null_mag;
    QSqlQuery m_q_obj_by_trixel_no_nulls;
    QSqlQuery m_q_obj_by_name;
    QSqlQuery m_q_obj_by_name_exact;
    QSqlQuery m_q_obj_by_lim;
    QSqlQuery m_q_obj_by_maglim;
    QSqlQuery m_q_obj_by_maglim_and_type;
    QSqlQuery m_q_obj_by_oid;
    //@}
 
    /**
     * The level of the htmesh used to index the catalog entries.
     *
     * If the htmesh level of a catalog is different, the catalog will
     * be reindexed upon importing it.
     *
     * A value of -1 means that the htmesh-level has not been
     * deterined yet.
     */
    int m_htmesh_level = -1;
 
    /**
     * The version of the database.
     *
     * A value of -1 means that the htmesh-level has not been
     * deterined yet.
     */
    int m_db_version = -1;
 
    /**
     * A simple mutex to be locked when using prepared statements,
     * that are stored in the class.
     */
    QMutex m_mutex;
 
    //@{
    /**
     * Helpers
     */
 
    /**
     * Initializes the database with the minimum viable tables.
     *
     * The catalog registry is created and the database version is set
     * to SqlStatements::current_db_version and the htmesh-level is
     * set to SqlStatements::default_htmesh_level if they don't exist.
     *
     * @return true in case of success, false in case of an error
     */
    bool initialize_db();
 
    /**
     * Reads the database version and the htmesh level from the
     * database. If the meta table does not exist, the default vaulues
     * SqlStatements::current_db_version and
     * SqlStatements::default_htmesh_level.
     *
     * @return [version, htmesh-level, is-init?]
     */
    std::tuple<int, int, bool> get_db_meta();
 
    /**
     * Gets a vector of catalog ids of catalogs. If \p include_disabled is
     * `true`, disabled catalogs will be included.
     */
    std::vector<int> get_catalog_ids(bool include_enabled = false);
 
    /**
     * Prepares performance critical sql queries.
     *
     * @return [success, error]
     */
    std::pair<bool, QSqlError> prepare_queries();
 
    /**
     * Read a `CatalogObject` from the tip of the \p query.
     */
    CatalogObject read_catalogobject(const QSqlQuery &query) const;
 
    /**
     * Read the first `CatalogObject` from the tip of the \p `query`
     * that hasn't been exec'd yet.
     */
    std::pair<bool, CatalogObject> read_first_object(QSqlQuery &query) const;
 
    /**
     * Read all `CatalogObject`s from the \p query.
     */
    CatalogObjectList fetch_objects(QSqlQuery &query) const;
 
    /**
     * Internal implementation to forcably remove a catalog (even the
     * user catalog, use with caution!)
     */
    std::pair<bool, QString> remove_catalog_force(const int id);
 
    /**
     *
     */
    CatalogObjectVector _get_objects_in_trixel_generic(QSqlQuery &query, const int trixel);
 
    /**
     * A list of database paths. The index gets stored in the
     * `CatalogObject` and can be used to retrieve the path to the
     * database.
     */
    static QSet<QString> m_db_paths;
    //@}
};
 
/**
 * Database related error, thrown when database access fails or an
 * action does not succeed.
 *
 * QSqlError is not used here to encapsulate the database further.
 */
class DatabaseError : std::exception
{
  public:
    enum class ErrorType
    {
        OPEN,
        VERSION,
        INIT,
        CREATE_CATALOG,
        CREATE_MASTER,
        NOT_FOUND,
        PREPARE,
        UNKNOWN
    };
 
    DatabaseError(QString message, ErrorType type = ErrorType::UNKNOWN,
                  const QSqlError &error = QSqlError())
        : m_message{ std::move(message) }, m_type{ type }, m_error{ error }, m_report{
              m_message.toStdString() +
              (error.text().length() > 0 ? "\nSQL ERROR: " + error.text().toStdString() :
                                           std::string(""))
          } {};
 
    const char *what() const noexcept override { return m_report.c_str(); }
    const QString &message() const noexcept { return m_message; }
    ErrorType type() const noexcept { return m_type; }
 
  private:
    const QString m_message;
    const ErrorType m_type;
    const QSqlError m_error;
    const std::string m_report;
};
 
/** \returns the path to the dso database */
QString dso_db_path();
 
/** \returns true and a catalog if the catalog metadata (name, author,
    ...) can be read */
std::pair<bool, Catalog> read_catalog_meta_from_file(const QString &path);
 
 
 
 
/**
 * A concurrent wrapper around \sa CatalogsDB::DBManager
 *
 * This wrapper can be instantiated from the main thread. It spawns
 * its own thread and moves itself to the thread, allowing the main
 * thread to call DB operations without blocking the user
 * interface. It provides a generic wrapper interface, \sa
 * AsyncDBManager::execute(), to call the methods of DBManager.
 *
 * Since it is hard to use signal-slot communication with a generic
 * wrapper like \sa AsyncDBManager::execute(), a wrapper is provided
 * for the two most likely overloads of \sa
 * DBManager::find_objects_by_name, which are time-consuming and
 * frequently used, and these can be directly invoked from
 * QMetaObject::invokeMethod or an appropriate signal
 *
 * The void override of \sa AsyncDBManager::init() does the most
 * commonly done thing, which is to open the DSO database
 *
 */
class AsyncDBManager : public QObject {
    // Note: Follows the active object pattern described here
    // https://youtu.be/SncJ3D-fO7g?list=PL6CJYn40gN6jgr-Rpl3J4XDQYhmUnxb-g&t=272
    Q_OBJECT
 
private:
    std::shared_ptr<DBManager> m_manager;
    std::queue<std::unique_ptr<CatalogObjectList>> m_result;
    std::shared_ptr<QThread> m_thread;
    QMutex m_resultMutex;
 
public:
    template <typename... Args>
    using DBManagerMethod = CatalogObjectList (DBManager::*)(Args...);
 
    /**
     * Constructor, does nothing. Call init() to do the actual setup after the QThread stars
     */
    template <typename... Args>
    AsyncDBManager(Args... args)
        : QObject(nullptr)
        , m_manager(nullptr)
        , m_thread(nullptr)
    {
        m_thread.reset(new QThread);
        moveToThread(m_thread.get());
        connect(m_thread.get(), &QThread::started, [&]() {
            init(args...);
        });
        m_thread->start();
 
        /*
         * This is an attempt to fix a bug introduced in 5a2ba9f8e8b275f44b7593a50ca66f09cb2f985d
         * where KStars Crashes on MacOS when launched by double clicking (NOT by Terminal or QT Creator)
         * and then the find dialog is accessed.  For some reason, this fixes it?
         */
        #ifdef Q_OS_OSX
            QThread::msleep(100);
        #endif
    }
 
    ~AsyncDBManager()
    {
        QMetaObject::invokeMethod(this, "cleanup");
        m_thread->wait();
    }
 
    /**
     * Return a pointer to the DBManager, for non-DB functionalities
     */
    inline std::shared_ptr<DBManager> manager() { return m_manager; }
 
    /**
     * Return a pointer to the QThread object
     */
    inline std::shared_ptr<QThread> thread() { return m_thread; }
 
    /**
     * Construct the DBManager object
     *
     * Should be done in the thread corresponding to this object
     */
    template <typename... Args> void init(Args&&... args)
    {
        m_manager = std::make_shared<DBManager>(std::forward<Args>(args)...);
    }
 
    /**
     * A generic wrapper to call any method on DBManager that returns a CatalogObjectList
     *
     * For practical use examples, see \sa
     * AsyncDBManager::find_objects_by_name below which uses this
     * wrapper
     */
    template <typename... Args>
    void execute(DBManagerMethod<Args...> dbManagerMethod, Args... args)
    {
        // c.f. https://stackoverflow.com/questions/25392935/wrap-a-function-pointer-in-c-with-variadic-template
 
        // N.B. The perfect forwarding idiom is not used because we
        // also want to be able to bind to lvalue references, whereas
        // the types deduced for the arguments has to match the type
        // deduced to identify the function overload to be used.
        QMutexLocker _{&m_resultMutex};
        m_result.emplace(
            std::make_unique<CatalogObjectList>((m_manager.get()->*dbManagerMethod)(args...))
            );
        emit resultReady();
    }
 
    /**
     * execute(), but specialized to find_objects_by_name
     *
     * @fixme Code duplication needed to support older compilers
     */
    void _find_objects_by_name(const QString& name, const int limit, const bool exactMatchOnly)
    {
        // FIXME: Remove this and use execute() once C++1x compilers
        // support variadic template type deduction properly
        QMutexLocker _{&m_resultMutex};
        m_result.emplace(
            std::make_unique<CatalogObjectList>((m_manager.get()->find_objects_by_name)(name, limit, exactMatchOnly))
            );
        emit resultReady();
    }
 
signals:
    void resultReady(void);
    void threadReady(void);
 
 
public slots:
 
    void init()
    {
        m_manager = std::make_shared<DBManager>(dso_db_path());
    }
 
    /**
     * Calls the given DBManager method, storing the result for later retrieval
     *
     * \p dbManagerMethod method to execute (must return a CatalogObjectList)
     * \p args arguments to supply to the method
     */
 
    void find_objects_by_name(const QString& name, const int limit = -1)
    {
        // N.B. One cannot have a function pointer to a function with
        // default arguments, so all arguments must be supplied here
 
        // FIXME: Uncomment to use generic wrapper execute() once
        // compilers gain proper type-deduction support
        // execute<const QString&, const int, const bool>(
        //     &DBManager::find_objects_by_name,
        //     name, limit, false);
 
        _find_objects_by_name(name, limit, false);
    }
 
    void find_objects_by_name_exact(const QString &name)
    {
        // FIXME: Uncomment to use generic wrapper execute() once
        // compilers gain proper type-deduction support
        // execute<const QString&, const int, const bool>(
        //     &DBManager::find_objects_by_name,
        //     name, 1, true);
 
        _find_objects_by_name(name, 1, true);
    }
 
    /**
     * Returns the result of the previous call, or a nullptr if none exists
     */
    std::unique_ptr<CatalogObjectList> result()
    {
        QMutexLocker _{&m_resultMutex};
        if (m_result.empty())
        {
            return std::unique_ptr<CatalogObjectList>();
        }
        std::unique_ptr<CatalogObjectList> result = std::move(m_result.front());
        m_result.pop();
        return result;
    }
 
private slots:
 
    void cleanup()
    {
        Q_ASSERT(m_manager.use_count() == 1);
        m_manager.reset();
        m_thread->quit();
    }
 
    void emitReady()
    {
        emit threadReady();
    }
 
};
 
} // namespace CatalogsDB