import asyncio
import collections
import io
import reprlib
import time
import weakref
import logging
from contextlib import suppress

from operator import attrgetter

from defence360agent.contracts.messages import Message, Reject
from defence360agent.contracts.plugins import BaseMessageProcessor
from defence360agent.utils.common import DAY, ServiceBase, rate_limit
from defence360agent.internals.global_scope import g

logger = logging.getLogger(__name__)

ProcessingMessage = collections.namedtuple(
    "ProcessingMessage", ["message", "start_time"]
)


class TheSink(BaseMessageProcessor):
    def __init__(self, sink_list, loop):
        self._sinks_ordered = sorted(
            sink_list, key=attrgetter("PROCESSING_ORDER")
        )
        self._loop = loop
        self._task_manager = TaskManager(
            loop, MessageProcessor(self._sinks_ordered)
        )
        g.sink = self

    def __repr__(self):
        return "%s.%s" % (self.__class__.__module__, self.__class__.__name__)

    def decompose(self, classobj):
        """
        introspection: decompose a specific role
        :return classobj: instance or None
        """
        options = [
            sink for sink in self._sinks_ordered if isinstance(sink, classobj)
        ]
        assert len(options) <= 1, "Ambiguous request"
        return next(iter(options), None)

    def start(self):
        """
        Make sure to run message processing bus only
        when every MessageSource (or MessageSource+MessageSink mix)
        got initialized
        """
        self._task_manager.start()

    async def shutdown(self):
        logger.info("shutdown the sink started")
        self._task_manager.should_stop()
        logger.info("wait for current tasks")
        await self._task_manager.wait_current_tasks(timeout=5)
        logger.info("finish wait task")
        await self._task_manager.wait()

    async def process_message(self, message):
        await self._task_manager.push_msg(message)


class TaskManager(ServiceBase):
    # max queue message size
    MAXSIZE = 100000
    # number of concurrently processed messages
    CONCURRENCY = 5
    # how long an individual message may be processed
    TIMEOUT = 3600  # seconds

    def __init__(self, loop, msg_processor):
        super().__init__(loop)
        self._queue = MessageQueue(maxsize=self.MAXSIZE)
        self._concurrency = self.CONCURRENCY
        self._process_message_timeout = self.TIMEOUT
        self._msg_processor = msg_processor
        self.tasks = weakref.WeakSet()
        self._throttled_logger = rate_limit(period=DAY, on_drop=logger.warning)
        self.throttled_log_error = self._throttled_logger(logger.error)

    async def push_msg(self, msg):
        """Push message unless the queue is full."""
        if not self._queue.full():
            await self._queue.put(MessageComparable(msg))
        else:
            if self._throttled_logger.should_be_called:  # send to Sentry
                args = (
                    (
                        "Message queue is full %s. "
                        "Current processing messages: %s. Message ignored: %s"
                    ),
                    self._queue,
                    self.current_processing_messages,
                    msg,
                )
            else:  # don't serialize the queue on each log warning entry
                args = (
                    (
                        "Message queue is full. Queue size: %s "
                        "Current processing messages: %s. Message ignored: %s"
                    ),
                    self._queue.qsize(),
                    self.current_processing_messages,
                    msg,
                )
            self.throttled_log_error(*args)

    @property
    def current_processing_messages(self):
        # the loop should be safe (no ref should be removed from the weak
        # set while iterating)
        # https://stackoverflow.com/questions/12428026/safely-iterating-over-weakkeydictionary-and-weakvaluedictionary  # noqa
        # the loop is constant time because
        # len(self.tasks) == self._concurrency (fixed & small)
        return tuple(
            (
                task.processing_msg.message,
                round(time.monotonic() - task.processing_msg.start_time, 4),
            )
            for task in self.tasks
            if not task.done()
        )

    async def wait_current_tasks(self, timeout=None):
        if self.tasks:
            msg_to_process = [
                (m.get("method"), m.get("message_id"), lasting)
                for m, lasting in self.current_processing_messages
            ]
            logger.info(
                "Waiting for %r processing to finish",
                msg_to_process,
            )
            await asyncio.wait(self.tasks, timeout=timeout)

    async def _run(self):
        semaphore = asyncio.BoundedSemaphore(self._concurrency)
        try:
            while not self._should_stop:
                logger.debug("Message queue size: %s", self._queue.qsize())
                try:
                    await self.__limit_concurrency(semaphore)
                    msg_comparable = await self._queue.get()
                except asyncio.CancelledError:
                    break
                t = self._loop.create_task(
                    self._msg_processor(msg_comparable.msg)
                )  # type: asyncio.Task
                t.processing_msg = ProcessingMessage(
                    msg_comparable.msg, time.monotonic()
                )
                t.add_done_callback(lambda _: semaphore.release())
                t.add_done_callback(self._on_msg_processed)
                self.tasks.add(t)
            unprocessed = self._queue.qsize()
            if unprocessed:
                logger.warning(
                    "There is still %s unprocessed messages in the queue",
                    self._queue.qsize(),
                )
        except:  # NOQA
            logger.exception("Error during message processing:")

    async def __limit_concurrency(self, semaphore):
        """Try to acquire *semaphore* in a loop, log error on timeout."""
        while True:
            try:
                return await asyncio.wait_for(
                    semaphore.acquire(),
                    timeout=self._process_message_timeout,
                )
            except asyncio.TimeoutError:
                self.throttled_log_error(
                    "Message hasn't been processed in %s seconds",
                    self._process_message_timeout,
                )

    @staticmethod
    def _on_msg_processed(future):
        e = future.exception()
        if e:
            logger.exception("Error during message processing:", exc_info=e)


async def cancel_task(task):
    if not task.done():
        task.cancel()
        with suppress(asyncio.CancelledError):
            await task


class MessageProcessor(object):
    TIMEOUT_TO_SINK_PROCESS = 3600

    def __init__(self, sinks):
        self.sinks = sinks
        self.locks = weakref.WeakValueDictionary()
        self.throttled_log_error = rate_limit(period=60 * 60)(
            logger.error
        )  # send event to Sentry once an hour

    async def __call__(self, msg):
        ip = msg.get("attackers_ip")
        if ip:
            lock = self.locks.setdefault(ip, asyncio.Lock())
            async with lock:
                await self._call_unlocked(msg)
        else:
            await self._call_unlocked(msg)

    async def _call_unlocked(self, msg):
        start = time.monotonic()
        for sink in self.sinks:
            try:
                process_message_task = asyncio.create_task(
                    sink.process_message(msg)
                )
                processed = await asyncio.wait_for(
                    # shielded only for debug DEF-18627,
                    # it should intercept `CancelledError` that
                    # `asyncio.wait_for` send to `process_message_task`
                    # in case timeout
                    asyncio.shield(process_message_task),
                    timeout=self.TIMEOUT_TO_SINK_PROCESS,
                )
            except asyncio.CancelledError:
                break
            except Reject as e:
                logger.info("Rejected: %s -> %r", str(e), msg)
                return
            except asyncio.TimeoutError:
                # debug for DEF-18627, it's supposed that during this exception
                # handling we will get call stack in logs and see last await
                # that hang out coroutine was made,
                # may be it's give us some hint about problem
                stack = io.StringIO()
                process_message_task.print_stack(file=stack)
                stack.seek(0)
                logger.error(
                    "Message %r was not processed in the %r plugin in %ss; "
                    "Traceback: %s",
                    msg,
                    sink,
                    self.TIMEOUT_TO_SINK_PROCESS,
                    stack.read(),
                )
                return
            except Exception:
                logger.exception("Error processing %r in %r", msg, sink)
                return
            else:
                if isinstance(processed, Message):
                    msg = processed
            finally:
                await cancel_task(process_message_task)
        processing_time = time.monotonic() - start
        logger.info("%s processed in %.4f seconds", msg, processing_time)
        if processing_time > msg.PROCESSING_TIME_THRESHOLD:
            # send to Sentry
            self.throttled_log_error(
                "%s message took longer to process than expected "
                "(%.4f sec > %.4f sec)",
                msg,
                processing_time,
                msg.PROCESSING_TIME_THRESHOLD,
            )


class MessageComparable(object):
    """Wrapper to make message comparable."""

    # needed to keep order
    index = -1

    @staticmethod
    def __new__(cls, msg):
        cls.index += 1
        rv = super().__new__(cls)
        rv.priority = msg.PRIORITY, cls.index
        rv.msg = msg
        return rv

    def __lt__(self, other):
        return self.priority.__lt__(other.priority)

    def __repr__(self):
        return "<{klass}({msg!r}), priority={priority}>".format(
            klass=self.__class__.__name__,
            msg=self.msg,
            priority=self.priority,
        )


class MessageQueue(asyncio.PriorityQueue):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self._repr = reprlib.Repr()
        self._repr.maxstring = 50
        self._repr.maxtuple = 2000

    async def put(self, item: MessageComparable):
        return await super().put(item)

    def __str__(self):
        # NOTE: do not flood console.log with full queue
        msg_counts = sorted(
            collections.Counter(
                [item.msg.__class__.__qualname__ for item in self._queue]
            ).items(),
            key=lambda item: item[1],  # sorted by number of messages
            reverse=True,
        )
        return (
            f"<PriorityQueue maxsize={self.maxsize}; "
            f"queue_size={self.qsize()} "
            f"queue_counter={self._repr.repr(msg_counts)}>"
        )