## @package lodel.plugin.interface Handles the Interface type plugins

from lodel.plugin.plugins import Plugin
from lodel.plugin.exceptions import PluginError, PluginTypeError, LodelScriptError, DatasourcePluginError
from lodel.validator.validator import Validator


## @brief Global type name used in the settings of Lodel for this type of plugins
_glob_typename = 'ui'


##@brief A plugin Interface
#@note It's a singleton class. Only 1 interface allowed by instance.
class InterfacePlugin(Plugin):
    
    ## @brief Singleton instance storage
    _instance = None

    ## @brief Settings description
    _plist_confspecs = {
        'section': 'lodel2',
        'key': 'interface',
        'default': None,
        'validator': Validator(
            'plugin', none_is_valid = True, ptype = _glob_typename)}

    ## @brief plugin type name
    _type_conf_name = _glob_typename
    
    ##
    # @param name str : Name of the interface plugin
    # @throw PluginError if there is already an interface plugin instanciated
    def __init__(self, name):
        if InterfacePlugin._instance is not None:
            raise PluginError("Maximum one interface allowed")
        super().__init__(name)
        self._instance = self

    ## @brief Clears the singleton from its active instance
    # @see plugins.Plugin::clear()
    @classmethod
    def clear_cls(cls):
        if cls._instance is not None:
            inst = cls._instance
            cls._instance = None
            del(inst)