standardrepository.hpp

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//==================================================================================================
/// \file
/// This header-file is part of module \alib_expressions of the \aliblong.
///
/// Copyright 2013-2026 A-Worx GmbH, Germany.
/// Published under #"mainpage_license".
//==================================================================================================
ALIB_EXPORT namespace alib {  namespace expressions {
 
//==================================================================================================
/// This is a default implementation of abstract interface #"ExpressionRepository"
/// which retrieves definitions of named expressions using core mechanics of \alib, namely:
/// 1. #"alib_mod_resources;Static resource data", and
/// 2. #"alib_mod_variables;Configuration data".
//==================================================================================================
class StandardRepository : public  ExpressionRepository {
  protected:
    /// The configuration object used to retrieve definitions of nested expressions.
    SharedConfiguration     config;
 
    /// The resource pool used to retrieve definitions of nested expressions, if not found
    /// with configuration data of field #".config".
    ResourcePool*           resources;
 
    /// The category within #".resources" to use for searching expression strings.
    NString                 resourceCategory;
 
  public:
    /// May be filled with paths in field #".config". A named expression's identifier will
    /// be first tried to be loaded using each path name added here.
    ///
    /// If this is left empty, with the first invocation of method #".Get", an empty string is
    /// added to enable to search an expression in the root of the #"%StringTree" of #".config".
    std::vector<AString>    ConfigPaths;
 
    /// Within this vector, all variables that have been loaded from #".config" are stored.
    ///
    /// The tuple elements provide:
    /// - the priority (configuration slot),
    /// - the variable name and
    /// - the name of the nested expression.
    ///
    /// The latter is needed, as it might differ from the combination of the "category" and
    /// variable name due to definitions in #"ConfigPaths".
    ///
    /// This vector might be used for various things, e.g., logging out status information.
    /// It is also used by method #"StoreLoadedExpressions".
    ///
    /// \note
    ///   This list is never cleared by this class. It might be cleared from outside
    ///   (e.g., to release memory) without causing any side effects, other than those occurring
    ///   to mechanics an application itself volunteers to implement using this information.
    std::vector<std::tuple<Priority,AString,String>>                            VariablesLoaded;
 
    /// Constructor.
    ///
    /// @param pConfig      The configuration data to use.
    ///                     May be set to \c nullptr to omit the use of configuration data.
    /// @param pResources   The resources to use.
    ///                     May be set to \c nullptr to omit the use of resource data.
    /// @param pResCategory The category within #".resources" to use for searching expression
    ///                     strings.
    inline
    StandardRepository( const SharedConfiguration& pConfig,
                        ResourcePool*              pResources,
                        NString                    pResCategory )
    : config          (pConfig)
    , resources       (pResources)
    , resourceCategory(pResCategory)                                                              {}
 
    /// Implementation of the central interface method. If invoked, the definition string is
    /// first searched in #".config" and if not found, secondly searched in field #".resources".
    ///
    /// @param      identifier  The name of the required expression.
    /// @param[out] target      The target to write the requested expression string to.
    /// @return This \c true, if the expression string could be retrieved, \c false otherwise.
    ///         If \c true is returned and \p{target} is still empty, then the string is defined
    ///         to be empty, which throws an exception on compilation.
    virtual ALIB_DLL
    bool                Get( const String& identifier, AString& target )                   override;
 
    /// Stores back all expression strings which had been automatically loaded from
    /// the plug-in of field #".config", specified by parameter \p{slot}.
    /// For storing, the normalized expression string is used. Thus, this method may be used to
    /// write a "clean" expression string, that does not use abbreviations for identifiers, has
    /// no unnecessary whitespaces, etc.
    ///
    /// Note the importance of parameter \p{slot}: Usually, only such expression variables
    /// should be stored that had been loaded from a configuration source that is manually edited
    /// by end-users, like INI-files.
    ///
    /// @param compiler  The compiler that this interface is attached to.
    /// @param slot      The slot of the configuration plug-in of which loaded variables are to
    ///                  be written back.
    /// @return The number of variables written.
    ALIB_DLL
    int             StoreLoadedExpressions( Compiler*  compiler,
                                            Priority slot = Priority::Standard  );
};
 
}} // namespace [alib::expressions]