"""SyncFlowExecutor that will run continuously until stop is called."""
import logging
import time
from concurrent.futures.thread import ThreadPoolExecutor
from dataclasses import dataclass
from typing import Callable, Optional

from samcli.lib.sync.exceptions import SyncFlowException
from samcli.lib.sync.sync_flow import SyncFlow
from samcli.lib.sync.sync_flow_executor import SyncFlowExecutor, SyncFlowFuture, SyncFlowTask, default_exception_handler

LOG = logging.getLogger(__name__)


@dataclass(frozen=True, eq=True)
class DelayedSyncFlowTask(SyncFlowTask):
    """Data struct for individual SyncFlow execution tasks"""

    # Time in seconds of when the task was initially queued
    queue_time: float

    # Number of seconds this task should stay in queue before being executed
    wait_time: float


class ContinuousSyncFlowExecutor(SyncFlowExecutor):
    """SyncFlowExecutor that continuously runs and executes SyncFlows.
    Call stop() to stop the executor"""

    # Flag for whether the executor should be stopped at the next available time
    _stop_flag: bool

    def __init__(self) -> None:
        super().__init__()
        self._stop_flag = False

    def stop(self, should_stop=True) -> None:
        """Stop executor after all current SyncFlows are finished."""
        with self._flow_queue_lock:
            self._stop_flag = should_stop
            if should_stop:
                self._flow_queue.queue.clear()

    def should_stop(self) -> bool:
        """
        Returns
        -------
        bool
            Should executor stop execution on the next available time.
        """
        return self._stop_flag

    def _can_exit(self):
        return self.should_stop() and super()._can_exit()

    def _submit_sync_flow_task(
        self, executor: ThreadPoolExecutor, sync_flow_task: SyncFlowTask
    ) -> Optional[SyncFlowFuture]:
        """Submit SyncFlowTask to be executed by ThreadPoolExecutor
        and return its future
        Adds additional time checks for DelayedSyncFlowTask

        Parameters
        ----------
        executor : ThreadPoolExecutor
            THreadPoolExecutor to be used for execution
        sync_flow_task : SyncFlowTask
            SyncFlowTask to be executed.

        Returns
        -------
        Optional[SyncFlowFuture]
            Returns SyncFlowFuture generated by the SyncFlowTask.
            Can be None if the task cannot be executed yet.
        """
        if (
            isinstance(sync_flow_task, DelayedSyncFlowTask)
            and sync_flow_task.wait_time + sync_flow_task.queue_time > time.time()
        ):
            return None

        return super()._submit_sync_flow_task(executor, sync_flow_task)

    def _add_sync_flow_task(self, task: SyncFlowTask) -> None:
        """Add SyncFlowTask to the queue
        Skips if the executor is in the state of being shut down.

        Parameters
        ----------
        task : SyncFlowTask
            SyncFlowTask to be added.
        """
        if self.should_stop():
            LOG.debug(
                "%s is skipped from queueing as executor is in the process of stopping.", task.sync_flow.log_prefix
            )
            return

        super()._add_sync_flow_task(task)

    def add_delayed_sync_flow(self, sync_flow: SyncFlow, dedup: bool = True, wait_time: float = 0) -> None:
        """Add a SyncFlow to queue to be executed
        Locks will be set with LockDistributor

        Parameters
        ----------
        sync_flow : SyncFlow
            SyncFlow to be executed
        dedup : bool
            SyncFlow will not be added if this flag is True and has a duplicate in the queue
        wait_time : float
            Minimum number of seconds before SyncFlow executes
        """
        self._add_sync_flow_task(DelayedSyncFlowTask(sync_flow, dedup, time.time(), wait_time))

    def execute(
        self, exception_handler: Optional[Callable[[SyncFlowException], None]] = default_exception_handler
    ) -> None:
        """Blocking continuous execution of the SyncFlows

        Parameters
        ----------
        exception_handler : Optional[Callable[[Exception], None]], optional
            Function to be called if an exception is raised during the execution of a SyncFlow,
            by default default_exception_handler.__func__
        """
        super().execute(exception_handler=exception_handler)
        self.stop(should_stop=False)