# Source code for azure.core.async_paging

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    import collections.abc
    import logging
    from typing import (
        Iterable,
        AsyncIterator,
        TypeVar,
        Callable,
        Tuple,
        Optional,
        Awaitable,
    )

    _LOGGER = logging.getLogger(__name__)

    ReturnType = TypeVar("ReturnType")
    ResponseType = TypeVar("ResponseType")

    __all__ = [
        "AsyncPageIterator",
        "AsyncItemPaged"
    ]

    class AsyncList(AsyncIterator[ReturnType]):
        def __init__(self, iterable: Iterable[ReturnType]) -> None:
            """Change an iterable into a fake async iterator.

            Coul be useful to fill the async iterator contract when you get a list.

            :param iterable: A sync iterable of T
            """
            # Technically, if it's a real iterator, I don't need "iter"
            # but that will cover iterable and list as well with no troubles created.
            self._iterator = iter(iterable)

        async def __anext__(self) -> ReturnType:
            try:
                return next(self._iterator)
            except StopIteration as err:
                raise StopAsyncIteration() from err

    class AsyncPageIterator(AsyncIterator[AsyncIterator[ReturnType]]):
        def __init__(
            self,
            get_next: Callable[
                [Optional[str]], Awaitable[ResponseType]
            ],
            extract_data: Callable[
                [ResponseType], Awaitable[Tuple[str, AsyncIterator[ReturnType]]]
            ],
            continuation_token: Optional[str] = None,
        ) -> None:
            """Return an async iterator of pages.

            :param get_next: Callable that take the continuation token and return a HTTP response
            :param extract_data: Callable that take an HTTP response and return a tuple continuation token,
             list of ReturnType
            :param str continuation_token: The continuation token needed by get_next
            """
            self._get_next = get_next
            self._extract_data = extract_data
            self.continuation_token = continuation_token
            self._did_a_call_already = False
            self._response = None
            self._current_page = None

        async def __anext__(self):
            if self.continuation_token is None and self._did_a_call_already:
                raise StopAsyncIteration("End of paging")

            self._response = await self._get_next(self.continuation_token)
            self._did_a_call_already = True

            self.continuation_token, self._current_page = await self._extract_data(
                self._response
            )

            # If current_page was a sync list, wrap it async-like
            if isinstance(self._current_page, collections.abc.Iterable):
                self._current_page = AsyncList(self._current_page)

            return self._current_page

    class AsyncItemPaged(AsyncIterator[ReturnType]):
        def __init__(self, *args, **kwargs) -> None:
            """Return an async iterator of items.

            args and kwargs will be passed to the AsyncPageIterator constructor directly,
            except page_iterator_class
            """
            self._args = args
            self._kwargs = kwargs
            self._page_iterator = (
                None
            )  # type: Optional[AsyncIterator[AsyncIterator[ReturnType]]]
            self._page = None  # type: Optional[AsyncIterator[ReturnType]]
            self._page_iterator_class = self._kwargs.pop(
                "page_iterator_class", AsyncPageIterator
            )

        def by_page(
            self,
            continuation_token: Optional[str] = None,
        ) -> AsyncIterator[AsyncIterator[ReturnType]]:
            """Get an async iterator of pages of objects, instead of an async iterator of objects.

            :param str continuation_token:
                An opaque continuation token. This value can be retrieved from the
                continuation_token field of a previous generator object. If specified,
                this generator will begin returning results from this point.
            :returns: An async iterator of pages (themselves async iterator of objects)
            """
            return self._page_iterator_class(
                *self._args, **self._kwargs, continuation_token=continuation_token
            )

        async def __anext__(self) -> ReturnType:
            if self._page_iterator is None:
                self._page_iterator = self.by_page()
                return await self.__anext__()
            if self._page is None:
                # Let it raise StopAsyncIteration
                self._page = await self._page_iterator.__anext__()
                return await self.__anext__()
            try:
                return await self._page.__anext__()
            except StopAsyncIteration:
                self._page = None
                return await self.__anext__()