from dataclasses import dataclass

from core.concept import Concept, ErrorConcept, Property
from parsers.PythonParser import PythonParser, PythonGetNamesVisitor, PythonNode
from sdp.sheerkaDataProvider import SheerkaDataProvider, Event
from parsers.DefaultParser import DefaultParser, DefConceptNode

import logging

log = logging.getLogger(__name__)


class Singleton(type):
    _instances = {}

    def __call__(cls, *args, **kwargs):
        if cls not in cls._instances:
            cls._instances[cls] = super(Singleton, cls).__call__(*args, **kwargs)
        return cls._instances[cls]


@dataclass
class ReturnValue:
    """
    Class that handle the return of a concept
    To avoid using the try/except pattern for each and every call
    To give context (ie return message) even when the call is successful
    """
    status: bool
    value: Concept
    message: str = None


@dataclass
class ExecutionContext:
    """
    To keep track of the execution of a request
    """
    event_digest: str


class Sheerka(Concept, metaclass=Singleton):
    """
    Main controller for the project
    """

    NAME = "Sheerka"
    UNKNOWN_CONCEPT_NAME = "Unknown Concept"
    ERROR_CONCEPT_NAME = "Error"
    SUCCESS_CONCEPT_NAME = "Success"

    CONCEPTS_ENTRY = "Concepts"
    BUILTIN_CONCEPTS_KEYS = "Builtins"
    USER_CONCEPTS_KEYS = "Concepts"

    def __init__(self):
        log.debug("Starting Sheerka.")
        super().__init__(Sheerka.NAME)

        # cache of the most used concepts
        self.concepts_cache = []

        # a concept can be instantiated
        # ex: File is a concept, but File('foo.txt') is an instance
        # TODO: manage contexts
        self.instances = []

        # List of the known rules by the system
        # ex: hello => say('hello')
        self.rules = []

        self.sdp = None
        self.parsers = []

        self.key = self.NAME

    def initialize(self, root_folder=None):
        """
        Starting Sheerka
        Loads the current configuration
        Notes that when it's the first time, it also create the needed working folders
        :param root_folder: root configuration folder
        :return: ReturnValue(Success or Error)
        """

        try:
            self.sdp = SheerkaDataProvider(root_folder)
            self.parsers.append(lambda text: DefaultParser(text, PythonParser))

            if self.sdp.first_time:
                self.sdp.set_key(self.USER_CONCEPTS_KEYS, 1000)

            self.create_builtin_concepts()
        except IOError as e:
            return ReturnValue(False, self.get_concept(Sheerka.ERROR_CONCEPT_NAME), e)

        return ReturnValue(True, self.get_concept(Sheerka.SUCCESS_CONCEPT_NAME))

    def set_id_if_needed(self, obj, is_builtin):
        """
        Set the key for the concept if needed
        :param obj:
        :param is_builtin:
        :return:
        """
        if obj.id is not None:
            return
        obj.id = self.sdp.get_next_key(self.BUILTIN_CONCEPTS_KEYS if is_builtin else self.USER_CONCEPTS_KEYS)
        log.debug(f"Setting id '{obj.id}' to concept '{obj.name}'.")

    def create_builtin_concepts(self):
        """
        Initializes the builtin concepts
        :return: None
        """
        log.debug("Initializing builtin concepts")
        builtins = [
            self,
            Concept(Sheerka.UNKNOWN_CONCEPT_NAME, key=Sheerka.UNKNOWN_CONCEPT_NAME),
            Concept(Sheerka.SUCCESS_CONCEPT_NAME, key=Sheerka.SUCCESS_CONCEPT_NAME),
            Concept(Sheerka.ERROR_CONCEPT_NAME, key=Sheerka.ERROR_CONCEPT_NAME),
        ]

        for concept in builtins:
            from_db = self.sdp.get_safe(self.CONCEPTS_ENTRY, concept.name)
            if from_db is None:
                log.debug(f"'{concept.name}' concept is not found. Adding.")
                self.set_id_if_needed(concept, True)
                self.sdp.add("init", self.CONCEPTS_ENTRY, concept, use_ref=True)
            else:
                log.debug(f"Found concept '{from_db}'. Updating.")
                concept.update_from(from_db)

    def eval(self, text):
        evt_digest = self.sdp.save_event(Event(text))
        exec_context = ExecutionContext(evt_digest)
        result = self.try_parse(text)

        return_values = []
        for parser_name, status, node in result:
            if not status:
                return_values.append(ReturnValue(False, ErrorConcept(body=node)))
            elif status and isinstance(node, DefConceptNode):
                return_values.append(self.add_concept(exec_context, node))

        return return_values

    def try_parse(self, text):
        result = []
        log.debug(f"Parsing '{text}'")
        for parser in self.parsers:
            p = parser(text)
            # try:
            #     tree = p.parse()
            #     result.append((p.name, tree))
            # except Exception as e:
            #     result.append((p.name, e))
            tree = p.parse()
            result.append((p.name, not p.has_error, p.error_sink if p.has_error else tree))
        return result

    def get_concept(self, name):
        """
        Given a concept name, tries to find it
        :param name: name of the concept to look for
        :param is_builtin: is it a builtin concept ?
        :return: concept if found, UNKNOWN_CONCEPT otherwise
        """
        for concept in self.concepts_cache:
            if concept.name == name:
                return concept
        return ErrorConcept()

    def add_concept(self, exec_context, def_concept_node: DefConceptNode):
        """
        Adds a new concept to the system
        :param exec_context:
        :param def_concept_node:  DefConceptNode
        :return: digest of the new concept
        """

        # validate the node
        get_names_visitor = PythonGetNamesVisitor()

        concept = Concept(def_concept_node.name)
        for prop in ("where", "pre", "post", "body"):
            # put back the sources
            concept_part_node = getattr(def_concept_node, prop)
            if isinstance(concept_part_node, PythonNode):
                get_names_visitor.visit(concept_part_node.ast)
            source = concept_part_node.source if hasattr(concept_part_node, "source") else ""
            setattr(concept, prop, source)

        # try to find variables (eg props)
        for token in def_concept_node.tokens["name"]:
            if token.value in get_names_visitor.names:
                concept.props.append(Property(token.value, None))

        concept.key = DefaultParser.get_concept_name(def_concept_node.tokens["name"], [p.name for p in concept.props])
        concept.add_codes(def_concept_node.get_codes())
        self.set_id_if_needed(concept, False)

        self.sdp.add(exec_context.event_digest, self.CONCEPTS_ENTRY, concept, use_ref=True)

        return ReturnValue(True, concept)

    @staticmethod
    def concept_equals(concept1, concept2):
        """True if the two concepts refer to the same concept"""
        if concept1 is None and concept2 is None:
            return True

        if concept1 is None or concept2 is None:
            return False

        return concept1.key == concept2.key