PaginatedList.py

############################ Copyrights and license ############################
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# Copyright 2012 Vincent Jacques <vincent@vincent-jacques.net>                 #
# Copyright 2012 Zearin <zearin@gonk.net>                                      #
# Copyright 2013 AKFish <akfish@gmail.com>                                     #
# Copyright 2013 Bill Mill <bill.mill@gmail.com>                               #
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# Copyright 2014 Thialfihar <thi@thialfihar.org>                               #
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################################################################################

from typing import Any, Callable, Dict, Generic, Iterator, List, Optional, Type, TypeVar, Union
from urllib.parse import parse_qs

from github.GithubObject import GithubObject
from github.Requester import Requester

T = TypeVar("T", bound=GithubObject)


class PaginatedListBase(Generic[T]):
    __elements: List[T]

    def _couldGrow(self) -> bool:
        raise NotImplementedError

    def _fetchNextPage(self) -> List[T]:
        raise NotImplementedError

    def __init__(self, elements: Optional[List[T]] = None) -> None:
        self.__elements = [] if elements is None else elements

    def __getitem__(self, index: Union[int, slice]) -> Any:
        assert isinstance(index, (int, slice))
        if isinstance(index, int):
            self.__fetchToIndex(index)
            return self.__elements[index]
        else:
            return self._Slice(self, index)

    def __iter__(self) -> Iterator[T]:
        yield from self.__elements
        while self._couldGrow():
            newElements = self._grow()
            yield from newElements

    def _isBiggerThan(self, index: int) -> bool:
        return len(self.__elements) > index or self._couldGrow()

    def __fetchToIndex(self, index: int) -> None:
        while len(self.__elements) <= index and self._couldGrow():
            self._grow()

    def _grow(self) -> List[T]:
        newElements = self._fetchNextPage()
        self.__elements += newElements
        return newElements

    class _Slice:
        def __init__(self, theList: "PaginatedListBase[T]", theSlice: slice):
            self.__list = theList
            self.__start = theSlice.start or 0
            self.__stop = theSlice.stop
            self.__step = theSlice.step or 1

        def __iter__(self) -> Iterator[T]:
            index = self.__start
            while not self.__finished(index):
                if self.__list._isBiggerThan(index):
                    yield self.__list[index]
                    index += self.__step
                else:
                    return

        def __finished(self, index: int) -> bool:
            return self.__stop is not None and index >= self.__stop


class PaginatedList(PaginatedListBase[T]):
    """
    This class abstracts the `pagination of the API <https://docs.github.com/en/rest/guides/traversing-with-pagination>`_.

    You can simply enumerate through instances of this class::

        for repo in user.get_repos():
            print(repo.name)

    If you want to know the total number of items in the list::

        print(user.get_repos().totalCount)

    You can also index them or take slices::

        second_repo = user.get_repos()[1]
        first_repos = user.get_repos()[:10]

    If you want to iterate in reversed order, just do::

        for repo in user.get_repos().reversed:
            print(repo.name)

    And if you really need it, you can explicitly access a specific page::

        some_repos = user.get_repos().get_page(0)
        some_other_repos = user.get_repos().get_page(3)
    """

    def __init__(
        self,
        contentClass: Type[T],
        requester: Requester,
        firstUrl: str,
        firstParams: Any,
        headers: Optional[Dict[str, str]] = None,
        list_item: str = "items",
        total_count_item: str = "total_count",
        firstData: Optional[Any] = None,
        firstHeaders: Optional[Dict[str, Union[str, int]]] = None,
        attributesTransformer: Optional[Callable[[Dict[str, Any]], Dict[str, Any]]] = None,
    ):
        self.__requester = requester
        self.__contentClass = contentClass
        self.__firstUrl = firstUrl
        self.__firstParams = firstParams or ()
        self.__nextUrl = firstUrl
        self.__nextParams = firstParams or {}
        self.__headers = headers
        self.__list_item = list_item
        self.__total_count_item = total_count_item
        if self.__requester.per_page != 30:
            self.__nextParams["per_page"] = self.__requester.per_page
        self._reversed = False
        self.__totalCount: Optional[int] = None
        self._attributesTransformer = attributesTransformer

        first_page = []
        if firstData is not None and firstHeaders is not None:
            first_page = self._getPage(firstData, firstHeaders)
        super().__init__(first_page)

    def _transformAttributes(self, element: Dict[str, Any]) -> Dict[str, Any]:
        if self._attributesTransformer is None:
            return element
        return self._attributesTransformer(element)

    @property
    def totalCount(self) -> int:
        if not self.__totalCount:
            params = {} if self.__nextParams is None else self.__nextParams.copy()
            # set per_page = 1 so the totalCount is just the number of pages
            params.update({"per_page": 1})
            headers, data = self.__requester.requestJsonAndCheck(
                "GET", self.__firstUrl, parameters=params, headers=self.__headers
            )
            if "link" not in headers:
                if data and "total_count" in data:
                    self.__totalCount = data["total_count"]
                elif data:
                    if isinstance(data, dict):
                        data = data[self.__list_item]
                    self.__totalCount = len(data)
                else:
                    self.__totalCount = 0
            else:
                links = self.__parseLinkHeader(headers)
                lastUrl = links.get("last")
                if lastUrl:
                    self.__totalCount = int(parse_qs(lastUrl)["page"][0])
                else:
                    self.__totalCount = 0
        return self.__totalCount  # type: ignore

    def _getLastPageUrl(self) -> Optional[str]:
        headers, data = self.__requester.requestJsonAndCheck(
            "GET", self.__firstUrl, parameters=self.__nextParams, headers=self.__headers
        )
        links = self.__parseLinkHeader(headers)
        return links.get("last")

    @property
    def reversed(self) -> "PaginatedList[T]":
        r = PaginatedList(
            self.__contentClass,
            self.__requester,
            self.__firstUrl,
            self.__firstParams,
            self.__headers,
            self.__list_item,
            attributesTransformer=self._attributesTransformer,
        )
        r.__reverse()
        return r

    def __reverse(self) -> None:
        self._reversed = True
        lastUrl = self._getLastPageUrl()
        if lastUrl:
            self.__nextUrl = lastUrl

    def _couldGrow(self) -> bool:
        return self.__nextUrl is not None

    def _fetchNextPage(self) -> List[T]:
        headers, data = self.__requester.requestJsonAndCheck(
            "GET", self.__nextUrl, parameters=self.__nextParams, headers=self.__headers
        )
        data = data if data else []
        return self._getPage(data, headers)

    def _getPage(self, data: Any, headers: Dict[str, Any]) -> List[T]:
        self.__nextUrl = None  # type: ignore
        if len(data) > 0:
            links = self.__parseLinkHeader(headers)
            if self._reversed:
                if "prev" in links:
                    self.__nextUrl = links["prev"]
            elif "next" in links:
                self.__nextUrl = links["next"]
        self.__nextParams = None
        if self.__list_item in data:
            self.__totalCount = data.get(self.__total_count_item)
            data = data[self.__list_item]
        content = [
            self.__contentClass(self.__requester, headers, self._transformAttributes(element), completed=False)
            for element in data
            if element is not None
        ]
        if self._reversed:
            return content[::-1]
        return content

    def __parseLinkHeader(self, headers: Dict[str, str]) -> Dict[str, str]:
        links = {}
        if "link" in headers:
            linkHeaders = headers["link"].split(", ")
            for linkHeader in linkHeaders:
                url, rel, *rest = linkHeader.split("; ")
                url = url[1:-1]
                rel = rel[5:-1]
                links[rel] = url
        return links

    def get_page(self, page: int) -> List[T]:
        params = dict(self.__firstParams)
        if page != 0:
            params["page"] = page + 1
        if self.__requester.per_page != 30:
            params["per_page"] = self.__requester.per_page
        headers, data = self.__requester.requestJsonAndCheck(
            "GET", self.__firstUrl, parameters=params, headers=self.__headers
        )

        if self.__list_item in data:
            self.__totalCount = data.get("total_count")
            data = data[self.__list_item]
        return [
            self.__contentClass(self.__requester, headers, self._transformAttributes(element), completed=False)
            for element in data
        ]

    @classmethod
    def override_attributes(cls, overrides: Dict[str, Any]) -> Callable[[Dict[str, Any]], Dict[str, Any]]:
        def attributes_transformer(element: Dict[str, Any]) -> Dict[str, Any]:
            # Recursively merge overrides with attributes, overriding attributes with overrides
            element = cls.merge_dicts(element, overrides)
            return element

        return attributes_transformer

    @classmethod
    def merge_dicts(cls, d1: Dict[str, Any], d2: Dict[str, Any]) -> Dict[str, Any]:
        # clone d1
        d1 = d1.copy()
        for k, v in d2.items():
            if isinstance(v, dict):
                d1[k] = cls.merge_dicts(d1.get(k, {}), v)
            else:
                d1[k] = v
        return d1