import eventlet
import datetime as dt

from queue import Queue
from threading import Lock
from time import sleep
# from time import time

from collections import namedtuple
from dataclasses import dataclass
from eventlet import spawn_n
from eventlet import tpool

from pycs import app
from pycs.database.Project import Project
from pycs.interfaces.Pipeline import Pipeline
from pycs.jobs.JobRunner import JobRunner
from pycs.util.PipelineUtil import load_from_root_folder
from pycs.util import GreenWorker


@dataclass
class PipelineEntry(object):
    last_used: int = -1
    pipeline: Pipeline = None
    pipeline_name: str = None
    project_id: int = -1

    def __post_init__(self):
        if self.pipeline is not None:
            self.pipeline_name = self.pipeline.__class__.__name__
        self.poke()

    def poke(self):
        self.last_used = dt.datetime.now()

    def __str__(self):
        return f"<Pipeline '{self.pipeline_name}' for project #{self.project_id} (last_used: {self.last_used})>"

class PipelineCache(GreenWorker):
    """
    Store initialized pipelines and call `close` after `CLOSE_TIMER` if they are not requested
    another time.
    """
    CLOSE_TIMER = dt.timedelta(seconds=120)

    def __init__(self):
        super().__init__()

        self.__pipelines: dict[PipelineEntry] = {}
        self.__lock = Lock()


    def load_from_root_folder(self, project: Project, no_cache: bool = False) -> Pipeline:
        """
        load configuration.json and create an instance from the included code object

        :param project: associated project
        :return: Pipeline instance
        """
        root_folder = project.model.root_folder

        # check if instance is cached
        with self.__lock:
            if root_folder in self.__pipelines:
                entry: PipelineEntry = self.__pipelines[root_folder]
                entry.poke()

                self.info(f"Using {entry}")

                return entry.pipeline

        # load pipeline
        pipeline = load_from_root_folder(root_folder)

        if no_cache:
            return pipeline

        # save instance to cache
        with self.__lock:
            entry = PipelineEntry(pipeline=pipeline, project_id=project.id)
            self.info(f"Cached {entry}")
            self.__pipelines[root_folder] = entry
            self.queue.put((root_folder,))

        # return
        return pipeline

    def free_instance(self, project: Project):
        """
        Change an instance's status to unused and start the timer to call it's `close` function
        after `CLOSE_TIMER` seconds. The next call to `load_from_root_folder` in this interval
        will disable this timer.

        :param project: associated project
        """
        root_folder = project.model.root_folder

        with self.__lock:
            if root_folder in self.__pipelines:
                # reset "last used" to now
                self.__pipelines[root_folder].poke()

            # abort if no pipeline with this root folder is loaded
            else:
                return


    # executed as coroutine in the main thread
    def __run__(self):
        while True:
            # get pipeline
            res = tpool.execute(self.work)

            if res is self.STOP_QUEUE:
                break

            pipeline, project_id = res

            if pipeline is None:
                # pipeline vanished from cache
                continue

            project = Project.query.get(project_id)
            if project is None:
                # project does not exist anymore
                continue

            # create job to close pipeline
            JobRunner.run(project,
                            'Model Interaction',
                            f'{project.name} (close pipeline)',
                            f'{project.name}/model-interaction',
                            pipeline.close
                        )
        self._finish()

    # executed in a separate thread
    def work(self):
        while True:
            res = self.check_queue()

            if res is self.STOP_QUEUE:
                return res

            elif res is self.CONTINUE_QUEUE:
                continue

            # an entry was found in the queue
            return self._check_cache_entry(*res)

    def _check_cache_entry(self, key):
        with self.__lock:
            entry = self.__pipelines.get(key)

        if entry is None:
            self.info(f"Entry for {key} already gone")
            return None, None

        self.info(f"Starting checks for {entry}...")
        while True:
            now = dt.datetime.now()

            with self.__lock:
                entry = self.__pipelines.get(key)

                if entry is None:
                    self.info(f"Entry for {key} already gone")
                    return None, None

                delay = entry.last_used + self.CLOSE_TIMER - now

            if delay.seconds > 0:
                sleep(delay.seconds)
                continue

            with self.__lock:
                entry = self.__pipelines.pop(key, None)
                if entry is None:
                    self.info(f"Entry for {key} already gone")
                    return None, None

            self.info(f"Removed {entry} from cache")
            return entry.pipeline, entry.project_id

    # def __get(self):
    #     while True:
    #         # get element from queue
    #         root_folder, timestamp = self.__queue.get()

    #         # sleep if needed
    #         delay = int(timestamp + self.CLOSE_TIMER - time())

    #         if delay > 0:
    #             eventlet.sleep(delay)

    #         # lock and access __pipelines
    #         with self.__lock:
    #             instance = self.__pipelines[root_folder]

    #             # reference counter greater than 1
    #             if instance.counter > 1:
    #                 # decrease reference counter
    #                 instance.counter -= 1

    #             # reference counter equals 1
    #             else:
    #                 # delete instance from __pipelines and return to call `close` function
    #                 del self.__pipelines[root_folder]
    #                 return instance.pipeline, instance.project_id

    # def __run(self):
    #     while True:
    #         # get pipeline
    #         pipeline, project_id = tpool.execute(self.__get)
    #         project = Project.query.get(project_id)

    #         # create job to close pipeline
    #         self.__jobs.run(project,
    #                         'Model Interaction',
    #                         f'{project.name} (close pipeline)',
    #                         f'{project.name}/model-interaction',
    #                         pipeline.close
    #                         )