import warnings
from datetime import datetime, timedelta, timezone
from functools import singledispatch
from pprint import pformat
from types import TracebackType
from typing import Any, Callable, Iterator, Optional, Type, TypeVar, Union

import aiormq
from aiormq.abc import DeliveredMessage
from pamqp.common import FieldValue

from .abc import (
    MILLISECONDS, AbstractChannel, AbstractIncomingMessage, AbstractMessage,
    AbstractProcessContext, DateType, DeliveryMode, HeadersType, MessageInfo,
    NoneType,
)
from .exceptions import ChannelInvalidStateError, MessageProcessError
from .log import get_logger


log = get_logger(__name__)


def to_milliseconds(seconds: Union[float, int]) -> int:
    return int(seconds * MILLISECONDS)


@singledispatch
def encode_expiration(value: Any) -> Optional[str]:
    raise ValueError("Invalid timestamp type: %r" % type(value), value)


@encode_expiration.register(datetime)
def encode_expiration_datetime(value: datetime) -> str:
    now = datetime.now(tz=value.tzinfo)
    return str(to_milliseconds((value - now).total_seconds()))


@encode_expiration.register(int)
@encode_expiration.register(float)
def encode_expiration_number(value: Union[int, float]) -> str:
    return str(to_milliseconds(value))


@encode_expiration.register(timedelta)
def encode_expiration_timedelta(value: timedelta) -> str:
    return str(int(value.total_seconds() * MILLISECONDS))


@encode_expiration.register(NoneType)
def encode_expiration_none(_: Any) -> None:
    return None


@singledispatch
def decode_expiration(t: Any) -> Optional[float]:
    raise ValueError("Invalid expiration type: %r" % type(t), t)


@decode_expiration.register(str)
def decode_expiration_str(t: str) -> float:
    return float(t) / MILLISECONDS


@decode_expiration.register(NoneType)
def decode_expiration_none(_: Any) -> None:
    return None


@singledispatch
def encode_timestamp(value: Any) -> Optional[datetime]:
    raise ValueError("Invalid timestamp type: %r" % type(value), value)


@encode_timestamp.register(datetime)
def encode_timestamp_datetime(value: datetime) -> datetime:
    return value


@encode_timestamp.register(float)
@encode_timestamp.register(int)
def encode_timestamp_number(value: Union[int, float]) -> datetime:
    return datetime.fromtimestamp(value, tz=timezone.utc)


@encode_timestamp.register(timedelta)
def encode_timestamp_timedelta(value: timedelta) -> datetime:
    return datetime.now(tz=timezone.utc) + value


@encode_timestamp.register(NoneType)
def encode_timestamp_none(_: Any) -> None:
    return None


@singledispatch
def decode_timestamp(value: Any) -> Optional[datetime]:
    raise ValueError("Invalid timestamp type: %r" % type(value), value)


@decode_timestamp.register(datetime)
def decode_timestamp_datetime(value: datetime) -> datetime:
    return value


@decode_timestamp.register(NoneType)
def decode_timestamp_none(_: Any) -> None:
    return None


V = TypeVar("V")
D = TypeVar("D")
T = TypeVar("T")


def optional(
    value: V,
    func: Union[Callable[[V], T], Type[T]],
    default: Optional[D] = None,
) -> Union[T, D]:
    return func(value) if value else default    # type: ignore


class Message(AbstractMessage):
    """ AMQP message abstraction """

    __slots__ = (
        "app_id",
        "body",
        "body_size",
        "content_encoding",
        "content_type",
        "correlation_id",
        "delivery_mode",
        "expiration",
        "_headers",
        "headers",
        "message_id",
        "priority",
        "reply_to",
        "timestamp",
        "type",
        "user_id",
        "__lock",
    )

    def __init__(
        self,
        body: bytes,
        *,
        headers: Optional[HeadersType] = None,
        content_type: Optional[str] = None,
        content_encoding: Optional[str] = None,
        delivery_mode: Union[DeliveryMode, int, None] = None,
        priority: Optional[int] = None,
        correlation_id: Optional[str] = None,
        reply_to: Optional[str] = None,
        expiration: Optional[DateType] = None,
        message_id: Optional[str] = None,
        timestamp: Optional[DateType] = None,
        type: Optional[str] = None,
        user_id: Optional[str] = None,
        app_id: Optional[str] = None,
    ):

        """ Creates a new instance of Message

        :param body: message body
        :param headers: message headers
        :param content_type: content type
        :param content_encoding: content encoding
        :param delivery_mode: delivery mode
        :param priority: priority
        :param correlation_id: correlation id
        :param reply_to: reply to
        :param expiration: expiration in seconds (or datetime or timedelta)
        :param message_id: message id
        :param timestamp: timestamp
        :param type: type
        :param user_id: user id
        :param app_id: app id
        """

        self.__lock = False
        self.body = body if isinstance(body, bytes) else bytes(body)
        self.body_size = len(self.body) if self.body else 0
        self.headers: HeadersType = headers or {}
        self.content_type = content_type
        self.content_encoding = content_encoding
        self.delivery_mode: DeliveryMode = DeliveryMode(
            optional(
                delivery_mode, int, DeliveryMode.NOT_PERSISTENT,
            ),
        )
        self.priority = optional(priority, int, 0)
        self.correlation_id = optional(correlation_id, str)
        self.reply_to = optional(reply_to, str)
        self.expiration = expiration
        self.message_id = optional(message_id, str)
        self.timestamp = encode_timestamp(timestamp)
        self.type = optional(type, str)
        self.user_id = optional(user_id, str)
        self.app_id = optional(app_id, str)

    @property
    def headers_raw(self) -> HeadersType:
        warnings.warn(
            f"{self.__class__.__name__}.headers_raw deprecated, please use "
            f"{self.__class__.__name__}.headers instead.",
            DeprecationWarning,
        )
        return self.headers

    @staticmethod
    def _as_bytes(value: Any) -> bytes:
        if isinstance(value, bytes):
            return value
        elif isinstance(value, str):
            return value.encode()
        elif value is None:
            return b""
        else:
            return str(value).encode()

    def info(self) -> MessageInfo:
        return MessageInfo(
            app_id=self.app_id,
            body_size=self.body_size,
            cluster_id=None,
            consumer_tag=None,
            content_encoding=self.content_encoding,
            content_type=self.content_type,
            correlation_id=self.correlation_id,
            delivery_mode=self.delivery_mode,
            delivery_tag=None,
            exchange=None,
            expiration=self.expiration,
            headers=self.headers,
            message_id=self.message_id,
            priority=self.priority,
            redelivered=None,
            reply_to=self.reply_to,
            routing_key=None,
            timestamp=decode_timestamp(self.timestamp),
            type=str(self.type),
            user_id=self.user_id,
        )

    @property
    def locked(self) -> bool:
        """ is message locked

        :return: :class:`bool`
        """
        return bool(self.__lock)

    @property
    def properties(self) -> aiormq.spec.Basic.Properties:
        """ Build :class:`aiormq.spec.Basic.Properties` object """
        return aiormq.spec.Basic.Properties(
            app_id=self.app_id,
            content_encoding=self.content_encoding,
            content_type=self.content_type,
            correlation_id=self.correlation_id,
            delivery_mode=self.delivery_mode,
            expiration=encode_expiration(self.expiration),
            headers=self.headers,
            message_id=self.message_id,
            message_type=self.type,
            priority=self.priority,
            reply_to=self.reply_to,
            timestamp=self.timestamp,
            user_id=self.user_id,
        )

    def __repr__(self) -> str:
        return "{name}:{repr}".format(
            name=self.__class__.__name__, repr=pformat(self.info()),
        )

    def __setattr__(self, key: str, value: FieldValue) -> None:
        if not key.startswith("_") and self.locked:
            raise ValueError("Message is locked")

        return super().__setattr__(key, value)

    def __iter__(self) -> Iterator[int]:
        return iter(self.body)

    def lock(self) -> None:
        """ Set lock flag to `True`"""
        self.__lock = True

    def __copy__(self) -> "Message":
        return Message(
            body=self.body,
            headers=self.headers,
            content_encoding=self.content_encoding,
            content_type=self.content_type,
            delivery_mode=self.delivery_mode,
            priority=self.priority,
            correlation_id=self.correlation_id,
            reply_to=self.reply_to,
            expiration=self.expiration,
            message_id=self.message_id,
            timestamp=self.timestamp,
            type=self.type,
            user_id=self.user_id,
            app_id=self.app_id,
        )


class IncomingMessage(Message, AbstractIncomingMessage):
    """ Incoming message is seems like Message but has additional methods for
    message acknowledgement.

    Depending on the acknowledgement mode used, RabbitMQ can consider a
    message to be successfully delivered either immediately after it is sent
    out (written to a TCP socket) or when an explicit ("manual") client
    acknowledgement is received. Manually sent acknowledgements can be
    positive or negative and use one of the following protocol methods:

    * basic.ack is used for positive acknowledgements
    * basic.nack is used for negative acknowledgements (note: this is a RabbitMQ
      extension to AMQP 0-9-1)
    * basic.reject is used for negative acknowledgements but has one limitation
      compared to basic.nack

    Positive acknowledgements simply instruct RabbitMQ to record a message as
    delivered. Negative acknowledgements with basic.reject have the same effect.
    The difference is primarily in the semantics: positive acknowledgements
    assume a message was successfully processed while their negative
    counterpart suggests that a delivery wasn't processed but still should
    be deleted.

    """

    __slots__ = (
        "_loop",
        "__channel",
        "cluster_id",
        "consumer_tag",
        "delivery_tag",
        "exchange",
        "routing_key",
        "redelivered",
        "__no_ack",
        "__processed",
        "message_count",
    )

    def __init__(self, message: DeliveredMessage, no_ack: bool = False):
        """ Create an instance of :class:`IncomingMessage` """

        self.__channel = message.channel
        self.__no_ack = no_ack
        self.__processed = False

        super().__init__(
            body=message.body,
            content_type=message.header.properties.content_type,
            content_encoding=message.header.properties.content_encoding,
            headers=message.header.properties.headers,
            delivery_mode=message.header.properties.delivery_mode,
            priority=message.header.properties.priority,
            correlation_id=message.header.properties.correlation_id,
            reply_to=message.header.properties.reply_to,
            expiration=decode_expiration(message.header.properties.expiration),
            message_id=message.header.properties.message_id,
            timestamp=decode_timestamp(message.header.properties.timestamp),
            type=message.header.properties.message_type,
            user_id=message.header.properties.user_id,
            app_id=message.header.properties.app_id,
        )

        self.cluster_id = message.header.properties.cluster_id
        self.consumer_tag = message.consumer_tag
        self.delivery_tag = message.delivery_tag
        self.exchange = message.exchange
        self.message_count = message.message_count
        self.redelivered = message.redelivered
        self.routing_key = message.routing_key

        if no_ack or not self.delivery_tag:
            self.lock()
            self.__processed = True

    @property
    def channel(self) -> aiormq.abc.AbstractChannel:
        if self.__channel.is_closed:
            raise ChannelInvalidStateError
        return self.__channel

    def process(
        self,
        requeue: bool = False,
        reject_on_redelivered: bool = False,
        ignore_processed: bool = False,
    ) -> AbstractProcessContext:
        """ Context manager for processing the message

            >>> async def on_message_received(message: IncomingMessage):
            ...    async with message.process():
            ...        # When exception will be raised
            ...        # the message will be rejected
            ...        print(message.body)

        Example with ignore_processed=True

            >>> async def on_message_received(message: IncomingMessage):
            ...    async with message.process(ignore_processed=True):
            ...        # Now (with ignore_processed=True) you may reject
            ...        # (or ack) message manually too
            ...        if True:  # some reasonable condition here
            ...            await message.reject()
            ...        print(message.body)

        :param requeue: Requeue message when exception.
        :param reject_on_redelivered:
            When True message will be rejected only when
            message was redelivered.
        :param ignore_processed: Do nothing if message already processed

        """
        return ProcessContext(
            self,
            requeue=requeue,
            reject_on_redelivered=reject_on_redelivered,
            ignore_processed=ignore_processed,
        )

    async def ack(self, multiple: bool = False) -> None:
        """ Send basic.ack is used for positive acknowledgements

        .. note::
            This method looks like a blocking-method, but actually it just
            sends bytes to the socket and doesn't require any responses from
            the broker.

        :param multiple: If set to True, the message's delivery tag is
                         treated as "up to and including", so that multiple
                         messages can be acknowledged with a single method.
                         If set to False, the ack refers to a single message.
        :return: None
        """
        if self.__no_ack:
            raise TypeError('Can\'t ack message with "no_ack" flag')

        if self.__processed:
            raise MessageProcessError("Message already processed", self)

        if self.delivery_tag is not None:
            await self.channel.basic_ack(
                delivery_tag=self.delivery_tag, multiple=multiple,
            )

        self.__processed = True

        if not self.locked:
            self.lock()

    async def reject(self, requeue: bool = False) -> None:
        """ When `requeue=True` the message will be returned to queue.
        Otherwise, message will be dropped.

        .. note::
            This method looks like a blocking-method, but actually it just
            sends bytes to the socket and doesn't require any responses from
            the broker.

        :param requeue: bool
        """
        if self.__no_ack:
            raise TypeError('This message has "no_ack" flag.')

        if self.__processed:
            raise MessageProcessError("Message already processed", self)

        if self.delivery_tag is not None:
            await self.channel.basic_reject(
                delivery_tag=self.delivery_tag,
                requeue=requeue,
            )

        self.__processed = True
        if not self.locked:
            self.lock()

    async def nack(
        self, multiple: bool = False, requeue: bool = True,
    ) -> None:

        if not self.channel.connection.basic_nack:
            raise RuntimeError("Method not supported on server")

        if self.__no_ack:
            raise TypeError('Can\'t nack message with "no_ack" flag')

        if self.__processed:
            raise MessageProcessError("Message already processed", self)

        if self.delivery_tag is not None:
            await self.channel.basic_nack(
                delivery_tag=self.delivery_tag,
                multiple=multiple,
                requeue=requeue,
            )

        self.__processed = True

        if not self.locked:
            self.lock()

    def info(self) -> MessageInfo:
        """ Method returns dict representation of the message """

        info = super().info()
        info["cluster_id"] = self.cluster_id
        info["consumer_tag"] = self.consumer_tag
        info["delivery_tag"] = self.delivery_tag
        info["exchange"] = self.exchange
        info["redelivered"] = self.redelivered
        info["routing_key"] = self.routing_key
        return info

    @property
    def processed(self) -> bool:
        return self.__processed


class ReturnedMessage(IncomingMessage):
    pass


ReturnCallback = Callable[[AbstractChannel, ReturnedMessage], Any]


class ProcessContext(AbstractProcessContext):
    def __init__(
        self,
        message: IncomingMessage,
        *,
        requeue: bool,
        reject_on_redelivered: bool,
        ignore_processed: bool,
    ):
        self.message = message
        self.requeue = requeue
        self.reject_on_redelivered = reject_on_redelivered
        self.ignore_processed = ignore_processed

    async def __aenter__(self) -> IncomingMessage:
        return self.message

    async def __aexit__(
        self,
        exc_type: Optional[Type[BaseException]],
        exc_val: Optional[BaseException],
        exc_tb: Optional[TracebackType],
    ) -> None:
        if not exc_type:
            if not self.ignore_processed or not self.message.processed:
                await self.message.ack()

            return

        if not self.ignore_processed or not self.message.processed:
            if self.reject_on_redelivered and self.message.redelivered:
                if not self.message.channel.is_closed:
                    log.info(
                        "Message %r was redelivered and will be rejected",
                        self.message,
                    )
                    await self.message.reject(requeue=False)
                    return
                log.warning(
                    "Message %r was redelivered and reject is not sent "
                    "since channel is closed",
                    self.message,
                )
            else:
                if not self.message.channel.is_closed:
                    await self.message.reject(requeue=self.requeue)
                    return
                log.warning("Reject is not sent since channel is closed")


__all__ = "Message", "IncomingMessage", "ReturnedMessage",