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.green_worker 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):
    CLOSE_TIMER = dt.timedelta(seconds=120)

    def __init__(self, jobs: JobRunner):
        super().__init__()
        self.__jobs = jobs

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


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

        :param projeventletect: associated project
        :param root_folder: path to model root folder
        :return: Pipeline instance
        """
        # check if instance is cached
        with self.__lock:
            if root_folder in self.__pipelines:
                entry: PipelineEntry = self.__pipelines[root_folder]
                entry.poke()

                app.logger.info(f"[{self.ident}] 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)
            app.logger.info(f"[{self.ident}] Cached {entry}")
            self.__pipelines[root_folder] = entry

        # return
        return pipeline

    def free_instance(self, root_folder: str):
        """
        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 root_folder: path to model root folder
        """
        # abort if no pipeline with this root folder is loaded
        with self.__lock:
            if root_folder not in self.__pipelines:
                return

        self.queue.put((root_folder,))

    # executed as coroutine in the main thread
    def start_work(self, *args):

        # delegate to work method in a separate thread
        res = super().start_work(*args)

        if res is None:
            # an error occured in the execution
            return

        pipeline, project_id = res

        if pipeline is None:
            # pipeline vanished
            return

        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
                    )

    # executed in a separate thread
    def work(self, root_folder):
        with self.__lock:
            entry = self.__pipelines.get(root_folder)

        if entry is None:
            app.logger.info(f"[{self.ident}] Entry for {root_folder} already gone")
            return

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

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

                if entry is None:
                    app.logger.info(f"[{self.ident}] Entry for {root_folder} 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(root_folder, None)
                app.logger.info(f"[{self.ident}] Entry for {root_folder} already gone")
                return None, None

            app.logger.info(f"[{self.ident}] 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
    #                         )