import itertools
import typing

from .users import UserMethods
from .. import utils, hints
from ..requestiter import RequestIter
from ..tl import types, functions, custom

_MAX_CHUNK_SIZE = 100

if typing.TYPE_CHECKING:
    from .telegramclient import TelegramClient


class _DialogsIter(RequestIter):
    async def _init(
            self, offset_date, offset_id, offset_peer, ignore_migrated
    ):
        self.request = functions.messages.GetDialogsRequest(
            offset_date=offset_date,
            offset_id=offset_id,
            offset_peer=offset_peer,
            limit=1,
            hash=0
        )

        if self.limit <= 0:
            # Special case, get a single dialog and determine count
            dialogs = await self.client(self.request)
            self.total = getattr(dialogs, 'count', len(dialogs.dialogs))
            raise StopAsyncIteration

        self.seen = set()
        self.offset_date = offset_date
        self.ignore_migrated = ignore_migrated

    async def _load_next_chunk(self):
        self.request.limit = min(self.left, _MAX_CHUNK_SIZE)
        r = await self.client(self.request)

        self.total = getattr(r, 'count', len(r.dialogs))

        entities = {utils.get_peer_id(x): x
                    for x in itertools.chain(r.users, r.chats)}

        messages = {}
        for m in r.messages:
            m._finish_init(self.client, entities, None)
            messages[m.id] = m

        for d in r.dialogs:
            # We check the offset date here because Telegram may ignore it
            if self.offset_date:
                date = getattr(messages.get(
                    d.top_message, None), 'date', None)

                if not date or date.timestamp() > self.offset_date.timestamp():
                    continue

            peer_id = utils.get_peer_id(d.peer)
            if peer_id not in self.seen:
                self.seen.add(peer_id)
                cd = custom.Dialog(self.client, d, entities, messages)
                if cd.dialog.pts:
                    self.client._channel_pts[cd.id] = cd.dialog.pts

                if not self.ignore_migrated or getattr(
                        cd.entity, 'migrated_to', None) is None:
                    self.buffer.append(cd)

        if len(r.dialogs) < self.request.limit\
                or not isinstance(r, types.messages.DialogsSlice):
            # Less than we requested means we reached the end, or
            # we didn't get a DialogsSlice which means we got all.
            return True

        # Don't set `request.offset_id` to the last message ID.
        # Why? It seems to cause plenty of dialogs to be skipped.
        #
        # By leaving it to 0 after the first iteration, even if
        # the user originally passed another ID, we ensure that
        # it will work correctly.
        self.request.offset_id = 0
        self.request.exclude_pinned = True
        self.request.offset_date = r.messages[-1].date
        self.request.offset_peer =\
            entities[utils.get_peer_id(r.dialogs[-1].peer)]


class _DraftsIter(RequestIter):
    async def _init(self, **kwargs):
        r = await self.client(functions.messages.GetAllDraftsRequest())
        self.buffer.extend(custom.Draft._from_update(self.client, u)
                           for u in r.updates)

    async def _load_next_chunk(self):
        return []


class DialogMethods(UserMethods):

    # region Public methods

    def iter_dialogs(
            self: 'TelegramClient',
            limit: float = None,
            *,
            offset_date: hints.DateLike = None,
            offset_id: int = 0,
            offset_peer: hints.EntityLike = types.InputPeerEmpty(),
            ignore_migrated: bool = False
    ) -> _DialogsIter:
        """
        Iterator over the dialogs (open conversations/subscribed channels).

        Args:
            limit (`int` | `None`):
                How many dialogs to be retrieved as maximum. Can be set to
                ``None`` to retrieve all dialogs. Note that this may take
                whole minutes if you have hundreds of dialogs, as Telegram
                will tell the library to slow down through a
                ``FloodWaitError``.

            offset_date (`datetime`, optional):
                The offset date to be used.

            offset_id (`int`, optional):
                The message ID to be used as an offset.

            offset_peer (:tl:`InputPeer`, optional):
                The peer to be used as an offset.

            ignore_migrated (`bool`, optional):
                Whether :tl:`Chat` that have ``migrated_to`` a :tl:`Channel`
                should be included or not. By default all the chats in your
                dialogs are returned, but setting this to ``True`` will hide
                them in the same way official applications do.

        Yields:
            Instances of `telethon.tl.custom.dialog.Dialog`.
        """
        return _DialogsIter(
            self,
            limit,
            offset_date=offset_date,
            offset_id=offset_id,
            offset_peer=offset_peer,
            ignore_migrated=ignore_migrated
        )

    async def get_dialogs(self: 'TelegramClient', *args, **kwargs) -> hints.TotalList:
        """
        Same as `iter_dialogs`, but returns a
        `TotalList <telethon.helpers.TotalList>` instead.
        """
        return await self.iter_dialogs(*args, **kwargs).collect()

    def iter_drafts(self: 'TelegramClient') -> _DraftsIter:
        """
        Iterator over all open draft messages.

        Instances of `telethon.tl.custom.draft.Draft` are yielded.
        You can call `telethon.tl.custom.draft.Draft.set_message`
        to change the message or `telethon.tl.custom.draft.Draft.delete`
        among other things.
        """
        # TODO Passing a limit here makes no sense
        return _DraftsIter(self, None)

    async def get_drafts(self: 'TelegramClient') -> hints.TotalList:
        """
        Same as :meth:`iter_drafts`, but returns a list instead.
        """
        return await self.iter_drafts().collect()

    def conversation(
            self: 'TelegramClient',
            entity: hints.EntityLike,
            *,
            timeout: float = 60,
            total_timeout: float = None,
            max_messages: int = 100,
            exclusive: bool = True,
            replies_are_responses: bool = True) -> custom.Conversation:
        """
        Creates a `Conversation <telethon.tl.custom.conversation.Conversation>`
        with the given entity.

        This is not the same as just sending a message to create a "dialog"
        with them, but rather a way to easily send messages and await for
        responses or other reactions. Refer to its documentation for more.

        Args:
            entity (`entity`):
                The entity with which a new conversation should be opened.

            timeout (`int` | `float`, optional):
                The default timeout (in seconds) *per action* to be used. You
                may also override this timeout on a per-method basis. By
                default each action can take up to 60 seconds (the value of
                this timeout).

            total_timeout (`int` | `float`, optional):
                The total timeout (in seconds) to use for the whole
                conversation. This takes priority over per-action
                timeouts. After these many seconds pass, subsequent
                actions will result in ``asyncio.TimeoutError``.

            max_messages (`int`, optional):
                The maximum amount of messages this conversation will
                remember. After these many messages arrive in the
                specified chat, subsequent actions will result in
                ``ValueError``.

            exclusive (`bool`, optional):
                By default, conversations are exclusive within a single
                chat. That means that while a conversation is open in a
                chat, you can't open another one in the same chat, unless
                you disable this flag.

                If you try opening an exclusive conversation for
                a chat where it's already open, it will raise
                ``AlreadyInConversationError``.

            replies_are_responses (`bool`, optional):
                Whether replies should be treated as responses or not.

                If the setting is enabled, calls to `conv.get_response
                <telethon.tl.custom.conversation.Conversation.get_response>`
                and a subsequent call to `conv.get_reply
                <telethon.tl.custom.conversation.Conversation.get_reply>`
                will return different messages, otherwise they may return
                the same message.

                Consider the following scenario with one outgoing message,
                1, and two incoming messages, the second one replying::

                                        Hello! <1
                    2> (reply to 1) Hi!
                    3> (reply to 1) How are you?

                And the following code:

                .. code-block:: python

                    async with client.conversation(chat) as conv:
                        msg1 = await conv.send_message('Hello!')
                        msg2 = await conv.get_response()
                        msg3 = await conv.get_reply()

                With the setting enabled, ``msg2`` will be ``'Hi!'`` and
                ``msg3`` be ``'How are you?'`` since replies are also
                responses, and a response was already returned.

                With the setting disabled, both ``msg2`` and ``msg3`` will
                be ``'Hi!'`` since one is a response and also a reply.

        Returns:
            A `Conversation <telethon.tl.custom.conversation.Conversation>`.
        """
        return custom.Conversation(
            self,
            entity,
            timeout=timeout,
            total_timeout=total_timeout,
            max_messages=max_messages,
            exclusive=exclusive,
            replies_are_responses=replies_are_responses

        )

    # endregion