import datetime

from .. import TLObject
from ..functions.messages import SaveDraftRequest
from ..types import UpdateDraftMessage, DraftMessage
from ...errors import RPCError
from ...extensions import markdown
from ...utils import get_peer_id, get_input_peer


class Draft:
    """
    Custom class that encapsulates a draft on the Telegram servers, providing
    an abstraction to change the message conveniently. The library will return
    instances of this class when calling :meth:`get_drafts()`.

    Args:
        date (`datetime`):
            The date of the draft.

        link_preview (`bool`):
            Whether the link preview is enabled or not.

        reply_to_msg_id (`int`):
            The message ID that the draft will reply to.
    """
    def __init__(self, client, peer, draft, entity):
        self._client = client
        self._peer = peer
        self._entity = entity
        self._input_entity = get_input_peer(entity) if entity else None

        if not draft or not isinstance(draft, DraftMessage):
            draft = DraftMessage('', None, None, None, None)

        self._text = markdown.unparse(draft.message, draft.entities)
        self._raw_text = draft.message
        self.date = draft.date
        self.link_preview = not draft.no_webpage
        self.reply_to_msg_id = draft.reply_to_msg_id

    @classmethod
    def _from_dialog(cls, client, dialog):
        return cls(client=client, peer=dialog.dialog.peer,
                   draft=dialog.dialog.draft, entity=dialog.entity)

    @classmethod
    def _from_update(cls, client, update, entities=None):
        assert isinstance(update, UpdateDraftMessage)
        return cls(client=client, peer=update.peer, draft=update.draft,
                   entity=(entities or {}).get(get_peer_id(update.peer)))

    @property
    def entity(self):
        """
        The entity that belongs to this dialog (user, chat or channel).
        """
        return self._entity

    @property
    def input_entity(self):
        """
        Input version of the entity.
        """
        if not self._input_entity:
            try:
                self._input_entity = self._client._entity_cache[self._peer]
            except KeyError:
                pass

        return self._input_entity

    async def get_entity(self):
        """
        Returns `entity` but will make an API call if necessary.
        """
        if not self.entity and await self.get_input_entity():
            try:
                self._entity =\
                    await self._client.get_entity(self._input_entity)
            except ValueError:
                pass

        return self._entity

    async def get_input_entity(self):
        """
        Returns `input_entity` but will make an API call if necessary.
        """
        # We don't actually have an API call we can make yet
        # to get more info, but keep this method for consistency.
        return self.input_entity

    @property
    def text(self):
        """
        The markdown text contained in the draft. It will be
        empty if there is no text (and hence no draft is set).
        """
        return self._text

    @property
    def raw_text(self):
        """
        The raw (text without formatting) contained in the draft.
        It will be empty if there is no text (thus draft not set).
        """
        return self._raw_text

    @property
    def is_empty(self):
        """
        Convenience bool to determine if the draft is empty or not.
        """
        return not self._text

    async def set_message(
            self, text=None, reply_to=0, parse_mode=(),
            link_preview=None):
        """
        Changes the draft message on the Telegram servers. The changes are
        reflected in this object.

        :param str text: New text of the draft.
                         Preserved if left as None.

        :param int reply_to: Message ID to reply to.
                             Preserved if left as 0, erased if set to None.

        :param bool link_preview: Whether to attach a web page preview.
                                  Preserved if left as None.

        :param str parse_mode: The parse mode to be used for the text.
        :return bool: ``True`` on success.
        """
        if text is None:
            text = self._text

        if reply_to == 0:
            reply_to = self.reply_to_msg_id

        if link_preview is None:
            link_preview = self.link_preview

        raw_text, entities =\
            await self._client._parse_message_text(text, parse_mode)

        result = await self._client(SaveDraftRequest(
            peer=self._peer,
            message=raw_text,
            no_webpage=not link_preview,
            reply_to_msg_id=reply_to,
            entities=entities
        ))

        if result:
            self._text = text
            self._raw_text = raw_text
            self.link_preview = link_preview
            self.reply_to_msg_id = reply_to
            self.date = datetime.datetime.now(tz=datetime.timezone.utc)

        return result

    async def send(self, clear=True, parse_mode=()):
        """
        Sends the contents of this draft to the dialog. This is just a
        wrapper around ``send_message(dialog.input_entity, *args, **kwargs)``.
        """
        await self._client.send_message(
            self._peer, self.text, reply_to=self.reply_to_msg_id,
            link_preview=self.link_preview, parse_mode=parse_mode,
            clear_draft=clear
        )

    async def delete(self):
        """
        Deletes this draft, and returns ``True`` on success.
        """
        return await self.set_message(text='')

    def to_dict(self):
        try:
            entity = self.entity
        except RPCError as e:
            entity = e

        return {
            '_': 'Draft',
            'text': self.text,
            'entity': entity,
            'date': self.date,
            'link_preview': self.link_preview,
            'reply_to_msg_id': self.reply_to_msg_id
        }

    def __str__(self):
        return TLObject.pretty_format(self.to_dict())

    def stringify(self):
        return TLObject.pretty_format(self.to_dict(), indent=0)