#  Pyrogram - Telegram MTProto API Client Library for Python
#  Copyright (C) 2017-2020 Dan <https://github.com/delivrance>
#
#  This file is part of Pyrogram.
#
#  Pyrogram is free software: you can redistribute it and/or modify
#  it under the terms of the GNU Lesser General Public License as published
#  by the Free Software Foundation, either version 3 of the License, or
#  (at your option) any later version.
#
#  Pyrogram is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU Lesser General Public License for more details.
#
#  You should have received a copy of the GNU Lesser General Public License
#  along with Pyrogram.  If not, see <http://www.gnu.org/licenses/>.

from typing import AsyncGenerator, Optional

from pyrogram import types
from pyrogram.scaffold import Scaffold


class IterDialogs(Scaffold):
    async def iter_dialogs(
        self,
        limit: int = 0,
        offset_date: int = 0
    ) -> Optional[AsyncGenerator["types.Dialog", None]]:
        """Iterate through a user's dialogs sequentially.

        This convenience method does the same as repeatedly calling :meth:`~pyrogram.Client.get_dialogs` in a loop,
        thus saving you from the hassle of setting up boilerplate code. It is useful for getting the whole dialogs list
        with a single call.

        Parameters:
            limit (``int``, *optional*):
                Limits the number of dialogs to be retrieved.
                By default, no limit is applied and all dialogs are returned.

            offset_date (``int``):
                The offset date in Unix time taken from the top message of a :obj:`~pyrogram.types.Dialog`.
                Defaults to 0 (most recent dialog).

        Returns:
            ``Generator``: A generator yielding :obj:`~pyrogram.types.Dialog` objects.

        Example:
            .. code-block:: python

                # Iterate through all dialogs
                for dialog in app.iter_dialogs():
                    print(dialog.chat.first_name or dialog.chat.title)
        """
        current = 0
        total = limit or (1 << 31) - 1
        limit = min(100, total)

        pinned_dialogs = await self.get_dialogs(
            pinned_only=True
        )

        for dialog in pinned_dialogs:
            yield dialog

            current += 1

            if current >= total:
                return

        while True:
            dialogs = await self.get_dialogs(
                offset_date=offset_date,
                limit=limit
            )

            if not dialogs:
                return

            offset_date = dialogs[-1].top_message.date

            for dialog in dialogs:
                yield dialog

                current += 1

                if current >= total:
                    return