"""
Processor/Extension framework
Adapated from https://github.com/gdiepen/python_processor_example
"""
import inspect
import pkgutil

from src.logger import logger


class Processor:
    """Base class that each processor must inherit from."""

    def __init__(
        self,
        options=None,
        relative_dir=None,
        image_instance_ops=None,
    ):
        self.options = options
        self.relative_dir = relative_dir
        self.image_instance_ops = image_instance_ops
        self.tuning_config = image_instance_ops.tuning_config
        self.description = "UNKNOWN"


class ProcessorManager:
    """Upon creation, this class will read the processors package for modules
    that contain a class definition that is inheriting from the Processor class
    """

    def __init__(self, processors_dir="src.processors"):
        """Constructor that initiates the reading of all available processors
        when an instance of the ProcessorCollection object is created
        """
        self.processors_dir = processors_dir
        self.reload_processors()

    @staticmethod
    def get_name_filter(processor_name):
        def filter_function(member):
            return inspect.isclass(member) and member.__module__ == processor_name

        return filter_function

    def reload_processors(self):
        """Reset the list of all processors and initiate the walk over the main
        provided processor package to load all available processors
        """
        self.processors = {}
        self.seen_paths = []

        logger.info(f'Loading processors from "{self.processors_dir}"...')
        self.walk_package(self.processors_dir)

    def walk_package(self, package):
        """walk the supplied package to retrieve all processors"""
        imported_package = __import__(package, fromlist=["blah"])
        loaded_packages = []
        for _, processor_name, ispkg in pkgutil.walk_packages(
            imported_package.__path__, imported_package.__name__ + "."
        ):
            if not ispkg and processor_name != __name__:
                processor_module = __import__(processor_name, fromlist=["blah"])
                # https://stackoverflow.com/a/46206754/6242649
                clsmembers = inspect.getmembers(
                    processor_module,
                    ProcessorManager.get_name_filter(processor_name),
                )
                for _, c in clsmembers:
                    # Only add classes that are a sub class of Processor, but NOT Processor itself
                    if issubclass(c, Processor) & (c is not Processor):
                        self.processors[c.__name__] = c
                        loaded_packages.append(c.__name__)

        logger.info(f"Loaded processors: {loaded_packages}")


# Singleton export
PROCESSOR_MANAGER = ProcessorManager()