"""
The functions within are designed to load external files and apply functions against the data
The plugins are applied as 
    - post-processing if we are reading data 
    - and pre-processing if we are writing data

The plugin will use a decorator to identify meaningful functions
@TODO: This should work in tandem with loggin (otherwise we don't have visibility into what is going on)
"""
import importlib as IL
import importlib.util
import sys
import os

class Plugin :
    """
    Implementing function decorator for data-transport plugins (post-pre)-processing
    """
    def __init__(self,**_args):
        """
        :name   name of the plugin
        :mode   restrict to reader/writer
        :about  tell what the function is about    
        """
        self._name = _args['name'] if 'name' in _args else None
        self._version = _args['version'] if 'version' in _args else '0.1'
        self._doc = _args['doc'] if 'doc' in _args else "N/A"
        self._mode = _args['mode'] if 'mode' in _args else 'rw'
    def __call__(self,pointer,**kwargs):
        def wrapper(_args,**kwargs):
            return pointer(_args,**kwargs)
        #
        # @TODO:
        # add attributes to the wrapper object
        #
        self._name = pointer.__name__ if not self._name else self._name
        setattr(wrapper,'transport',True)
        setattr(wrapper,'name',self._name)
        setattr(wrapper,'version',self._version)
        setattr(wrapper,'doc',self._doc)
        return wrapper

class PluginLoader :
    """
    This class is intended to load a plugin and make it available and assess the quality of the developed plugin
    """
   
    def __init__(self,**_args):
        """
        """
        # _names = _args['names'] if 'names' in _args else None
        # path = _args['path'] if 'path' in _args else None
        # self._names = _names if type(_names) == list else [_names]
        self._modules = {}
        self._names = []
        self._registry = _args['registry']
        # if path and os.path.exists(path) and _names:
        #     for _name in self._names :
                
        #         spec = importlib.util.spec_from_file_location('private', path)
        #         module = importlib.util.module_from_spec(spec)
        #         spec.loader.exec_module(module) #--loads it into sys.modules
        #         if hasattr(module,_name) :
        #             if self.isplugin(module,_name) :
        #                 self._modules[_name] = getattr(module,_name)
        #             else:
        #                 print ([f'Found {_name}', 'not plugin'])
        #         else:
        #             #
        #             # @TODO: We should log this somewhere some how
        #             print (['skipping ',_name, hasattr(module,_name)])
        #             pass
        # else:
        #     #
        #     # Initialization is empty
        #     self._names = []
        pass
    def load (self,**_args):
        self._modules = {}
        self._names = []
        path = _args ['path']
        if os.path.exists(path) :
            _alias = path.split(os.sep)[-1]
            spec = importlib.util.spec_from_file_location(_alias, path)
            module = importlib.util.module_from_spec(spec)
            spec.loader.exec_module(module) #--loads it into sys.modules
            # self._names = [_name for _name in dir(module) if type(getattr(module,_name)).__name__ == 'function']
            for _name in dir(module) :
                if self.isplugin(module,_name) :
                    self._module[_name] = getattr(module,_name)
                    # self._names [_name]
    def format (self,**_args):
        uri = _args['alias'],_args['name']
    # def set(self,_pointer) :
    def set(self,_key) :
        """
        This function will set a pointer to the list of modules to be called
        This should be used within the context of using the framework as a library
        """
        # _name = _pointer.__name__ if type(_pointer).__name__ == 'function' else {}
        
        # self._modules[_name] = _pointer
        # self._names.append(_name)
        
        _pointer = self._registry.get(key=_key)
        if _pointer  :
            self._modules[_key] = _pointer
            self._names.append(_key)
        elif type(_key).__name__ == 'function':
            #
            # The pointer is in the code provided by the user and loaded in memory
            #
            _pointer = _key
            self._names.append(_key.__name__)
        
    def isplugin(self,module,name):
        """
        This function determines if a module is a recognized plugin
        :module     module object loaded from importlib
        :name       name of the functiion of interest
        """
        
        p = type(getattr(module,name)).__name__ =='function'
        q = hasattr(getattr(module,name),'transport')
        #
        # @TODO: add a generated key, and more indepth validation
        return p and q
    def has(self,_name):
        """
        This will determine if the module name is loaded or not
        """
        return _name in self._modules 
    def ratio (self):
        """
        This functiion determines how many modules loaded vs unloaded given the list of names
        """

        _n = len(self._names)
        return len(set(self._modules.keys()) & set (self._names)) / _n
    def apply(self,_data):
        for _name in self._modules :
            _pointer = self._modules[_name]
            #
            # @TODO: add exception handling
            _data = _pointer(_data)
        return _data
    # def apply(self,_data,_name):
    #     """
    #     This function applies an external module function against the data.
    #     The responsibility is on the plugin to properly return data, thus responsibility is offloaded
    #     """
    #     try:
            
    #         _pointer = self._modules[_name]
    #         _data = _pointer(_data)

    #     except Exception as e:
    #         pass
    #     return _data