Provide a paged pageable over paged

pagedpageable.py

class FakePagePaged:
    """ Iterable over pages of responses

    Only intended to show a straw-man for how it could be implemented
    """
    def __init__(self, item_paged):
        self._item_paged = item_paged

    def __iter__(self):
        return self

    def __next__(self):
        self._item_paged._fetch_more()
        self._item_paged._count -= len(self._item_paged.items)
        return self._item_paged.items


class FakeItemPaged:

    def __init__(self, *, diagnostics_response_hook=None, max_items=97):
        self._diagnostics_response_hook=diagnostics_response_hook
        self.items = []
        self._index = -1
        self._count = max_items

    def _fetch_more(self):
        self.items = list(range(20))
        if self._count < 0:
            # Added to make sure that the pagedpaged iterator will terminate.
            # Not correctly implemented - only here to allow showcasing how the
            # diagnostics hook can be used for pagedpaged...
            raise StopIteration()

        if self._diagnostics_response_hook:
            self._diagnostics_response_hook(self.items)

    def __next__(self):
        self._index += 1
        self._count -= 1

        if self._count < 0:
            raise StopIteration()

        if self._index >= len(self.items):
            self._fetch_more()
            self._index = 0
        return self.items[self._index]

    def __iter__(self):
        return self

    def by_page(self):
        return FakePagePaged(self)



class FakeService:

    def list_things(self, diagnostics_response_hook=None):
        return iter(FakeItemPaged(diagnostics_response_hook=diagnostics_response_hook))

class ItemCountHook:

    def __init__(self):
        self.page_count = 0
        self.count = 0

    def __call__(self, items):
        self.page_count += 1
        self.count += len(items)

svc = FakeService()
hook = ItemCountHook()

for thing in svc.list_things(diagnostics_response_hook=hook).by_page():
    print(thing)

print(hook.count)
print(hook.page_count)