import logging

from dataclasses import dataclass, field
from os import path
from pathlib import Path
from pprint import pformat
from shutil import rmtree
from typing import Callable

from .notifier import DoneNote, ErrorNote
from .package import Package, PackageManager
from .queuethread import QueueThread


@dataclass
class PendingItem:
    queueitem: dict
    handlers: list
    jobid: str = field(init=False)
    jobspec: dict = field(init=False)
    package: Package = field(init=False)

    def __post_init__(self):
        self.jobid = self.queueitem['jobid']
        self.jobspec = self.queueitem['jobspec']
        self.package = self.queueitem['existing']


@dataclass
class DoneItem:
    jobid: str
    handler: object  # Handler, but circular import prevents it
    apply_func: Callable


@dataclass
class ErrorItem:
    jobid: str
    handler: object # Handler, but circular import prevents it
    exception: Exception


@QueueThread.register
class Collector(QueueThread):
    """
    This class keeps track of pending actions and is responsible
    for cleaning up once all pending actions are done.
    """
    def __init__(self, notifier, packagedir, cachedir):
        super().__init__()
        self.packages = Path(packagedir)
        self.pkgid_cache = Path(cachedir)
        self.notifier = notifier
        self.trackers = {}

        self.actions = {PendingItem: self._process_pending,
                        DoneItem: self._process_done,
                        ErrorItem: self._process_error}

    def _process_pending(self, item):
        """
        Handle a pending notice.

        Throws an exception if the jobid is already known.
        """
        jobid = item.jobid
        if jobid in self.trackers:
            raise Exception(f"Job {jobid} has already been submitted")
        self.logger.info("%s - registering pending handlers %s",
                         jobid, pformat(item.handlers))
        self.trackers[jobid] = Tracker(item)

    def _process_done(self, item):
        """
        Handle a done notice. Submits a notification to the notifier. Discards
        the pending object if no more actions are pending.

        Throws an exception on unknown jobids.
        """
        jobid = item.jobid
        if jobid not in self.trackers:
            raise Exception(f"Job {jobid} not found in tracker")
        pending = self.trackers[jobid]
        if pending.failed:
            self.logger.info("%s - job has been marked as failed, "
                             "will not apply %s",
                             jobid,
                             pformat(item.handler))
            all_done = pending.finish(item.handler)
        else:
            if any(item.handler.apply_after(handler)
                   for handler in pending.handlers):
                # Defer processing if there are pending handlers that must
                # finish before this one
                # Not logging this due to unbelieveable spam
                return self.put(item)

            self.logger.info("%s - applying %s",
                             jobid,
                             item.handler.__class__.__name__)
            package_id = pending.jobspec['pkg_id']
            try:
                with (PackageManager(package_id,
                                     self.packages / package_id)
                      as package):
                    item.apply_func(package)
            except Exception as e:
                url = pending.jobspec.get('notification_url', None)
                self.notifier.put(ErrorNote(jobid,
                                            url,
                                            self.__class__.__name__,
                                            e))
                pending.failed = True
            else:
                all_done = pending.finish(item.handler)
                url = pending.jobspec.get('notification_url', None)
                pending_handlers = [handlerclass.__name__
                                    for handlerclass in pending.handlers]
                notification = DoneNote(jobid,
                                        url,
                                        item.handler.__class__.__name__,
                                        package.asdict(),
                                        pending_handlers)
                self.notifier.put(notification)
                if all_done:
                    self.trackers.pop(jobid)
                    (self.pkgid_cache / jobid).unlink(missing_ok=True)
                    self.logger.info("%s - all done", jobid)

    def _process_error(self, item):
        jobid = item.jobid
        origin = item.handler
        exception = item.exception
        if jobid not in self.trackers:
            raise Exception(f"Job {jobid} not found in tracker")
        pending = self.trackers[jobid]
        pending.failed = True
        url = pending.jobspec.get('notification_url', None)
        self.notifier.put(ErrorNote(jobid,
                                    url,
                                    origin.__class__.__name__,
                                    exception))

    def _process(self, item):
        """
        Work through the queue.

        Throws an exception on invalid action values.
        """
        if type(item) not in self.actions:
            raise Exception(f"Invalid action {type(item)}")
        # Call the appropriate handler method
        self.actions[type(item)](item)


class Tracker:
    """
    Utility class to represent pending actions.
    """
    def __init__(self, pending_item):
        self.logger = self.logger = logging.getLogger(
            f'play-daemon.{self.__class__.__name__}')
        self.jobid = pending_item.jobid
        self.jobspec = pending_item.jobspec
        self.temp_copy = pending_item.package
        self.handlers = pending_item.handlers
        self.failed = False

    def finish(self, handler):
        """
        Finish a pending action. Returns True if no more actions are pending,
        otherwise False.

        If no more actions are pending, cleans up files uploaded for the job
        before returning.

        Throws an exception if the given action is missing from the
        pending list.
        """
        handlerclass = handler.__class__
        if handlerclass not in self.handlers:
            raise Exception(f"{handler} missing from {self.handlers}")
        self.handlers.remove(handlerclass)
        if not self.handlers:
            # Clean up uploaded files once all handlers are done with the job
            # Failed jobs get cleaned manually for safety
            if 'upload_dir' in self.jobspec and not self.failed:
                self.logger.info("Deleting incoming files for job %s (%s)",
                                 self.jobid, self.jobspec['upload_dir'])
                rmtree(self.jobspec['upload_dir'])
            # Also remove the temporary copy of the previous package state
            if path.exists(self.temp_copy.basedir):
                self.logger.info("Deleting temporary files for job %s (%s)",
                                 self.jobid, self.temp_copy.basedir)
                rmtree(self.temp_copy.basedir)
            return True
        else:
            return False