"""
requests.exceptions
~~~~~~~~~~~~~~~~~~~

This module contains the set of Requests' exceptions.
"""
from pip._vendor.urllib3.exceptions import HTTPError as BaseHTTPError

from .compat import JSONDecodeError as CompatJSONDecodeError


class RequestException(IOError):
    """There was an ambiguous exception that occurred while handling your
    request.
    """

    def __init__(self, *args, **kwargs):
        """Initialize RequestException with `request` and `response` objects."""
        response = kwargs.pop("response", None)
        self.response = response
        self.request = kwargs.pop("request", None)
        if response is not None and not self.request and hasattr(response, "request"):
            self.request = self.response.request
        super().__init__(*args, **kwargs)


class InvalidJSONError(RequestException):
    """A JSON error occurred."""


class JSONDecodeError(InvalidJSONError, CompatJSONDecodeError):
    """Couldn't decode the text into json"""

    def __init__(self, *args, **kwargs):
        """
        Construct the JSONDecodeError instance first with all
        args. Then use it's args to construct the IOError so that
        the json specific args aren't used as IOError specific args
        and the error message from JSONDecodeError is preserved.
        """
        CompatJSONDecodeError.__init__(self, *args)
        InvalidJSONError.__init__(self, *self.args, **kwargs)

    def __reduce__(self):
        """
        The __reduce__ method called when pickling the object must
        be the one from the JSONDecodeError (be it json/simplejson)
        as it expects all the arguments for instantiation, not just
        one like the IOError, and the MRO would by default call the
        __reduce__ method from the IOError due to the inheritance order.
        """
        return CompatJSONDecodeError.__reduce__(self)


class HTTPError(RequestException):
    """An HTTP error occurred."""


class ConnectionError(RequestException):
    """A Connection error occurred."""


class ProxyError(ConnectionError):
    """A proxy error occurred."""


class SSLError(ConnectionError):
    """An SSL error occurred."""


class Timeout(RequestException):
    """The request timed out.

    Catching this error will catch both
    :exc:`~requests.exceptions.ConnectTimeout` and
    :exc:`~requests.exceptions.ReadTimeout` errors.
    """


class ConnectTimeout(ConnectionError, Timeout):
    """The request timed out while trying to connect to the remote server.

    Requests that produced this error are safe to retry.
    """


class ReadTimeout(Timeout):
    """The server did not send any data in the allotted amount of time."""


class URLRequired(RequestException):
    """A valid URL is required to make a request."""


class TooManyRedirects(RequestException):
    """Too many redirects."""


class MissingSchema(RequestException, ValueError):
    """The URL scheme (e.g. http or https) is missing."""


class InvalidSchema(RequestException, ValueError):
    """The URL scheme provided is either invalid or unsupported."""


class InvalidURL(RequestException, ValueError):
    """The URL provided was somehow invalid."""


class InvalidHeader(RequestException, ValueError):
    """The header value provided was somehow invalid."""


class InvalidProxyURL(InvalidURL):
    """The proxy URL provided is invalid."""


class ChunkedEncodingError(RequestException):
    """The server declared chunked encoding but sent an invalid chunk."""


class ContentDecodingError(RequestException, BaseHTTPError):
    """Failed to decode response content."""


class StreamConsumedError(RequestException, TypeError):
    """The content for this response was already consumed."""


class RetryError(RequestException):
    """Custom retries logic failed"""


class UnrewindableBodyError(RequestException):
    """Requests encountered an error when trying to rewind a body."""


# Warnings


class RequestsWarning(Warning):
    """Base warning for Requests."""


class FileModeWarning(RequestsWarning, DeprecationWarning):
    """A file was opened in text mode, but Requests determined its binary length."""


class RequestsDependencyWarning(RequestsWarning):
    """An imported dependency doesn't match the expected version range."""

from __future__ import annotations

import contextlib
import re
from dataclasses import dataclass
from typing import Iterator, NoReturn

from .specifiers import Specifier


@dataclass
class Token:
    name: str
    text: str
    position: int


class ParserSyntaxError(Exception):
    """The provided source text could not be parsed correctly."""

    def __init__(
        self,
        message: str,
        *,
        source: str,
        span: tuple[int, int],
    ) -> None:
        self.span = span
        self.message = message
        self.source = source

        super().__init__()

    def __str__(self) -> str:
        marker = " " * self.span[0] + "~" * (self.span[1] - self.span[0]) + "^"
        return "\n    ".join([self.message, self.source, marker])


DEFAULT_RULES: dict[str, str | re.Pattern[str]] = {
    "LEFT_PARENTHESIS": r"\(",
    "RIGHT_PARENTHESIS": r"\)",
    "LEFT_BRACKET": r"\[",
    "RIGHT_BRACKET": r"\]",
    "SEMICOLON": r";",
    "COMMA": r",",
    "QUOTED_STRING": re.compile(
        r"""
            (
                ('[^']*')
                |
                ("[^"]*")
            )
        """,
        re.VERBOSE,
    ),
    "OP": r"(===|==|~=|!=|<=|>=|<|>)",
    "BOOLOP": r"\b(or|and)\b",
    "IN": r"\bin\b",
    "NOT": r"\bnot\b",
    "VARIABLE": re.compile(
        r"""
            \b(
                python_version
                |python_full_version
                |os[._]name
                |sys[._]platform
                |platform_(release|system)
                |platform[._](version|machine|python_implementation)
                |python_implementation
                |implementation_(name|version)
                |extra
            )\b
        """,
        re.VERBOSE,
    ),
    "SPECIFIER": re.compile(
        Specifier._operator_regex_str + Specifier._version_regex_str,
        re.VERBOSE | re.IGNORECASE,
    ),
    "AT": r"\@",
    "URL": r"[^ \t]+",
    "IDENTIFIER": r"\b[a-zA-Z0-9][a-zA-Z0-9._-]*\b",
    "VERSION_PREFIX_TRAIL": r"\.\*",
    "VERSION_LOCAL_LABEL_TRAIL": r"\+[a-z0-9]+(?:[-_\.][a-z0-9]+)*",
    "WS": r"[ \t]+",
    "END": r"$",
}


class Tokenizer:
    """Context-sensitive token parsing.

    Provides methods to examine the input stream to check whether the next token
    matches.
    """

    def __init__(
        self,
        source: str,
        *,
        rules: dict[str, str | re.Pattern[str]],
    ) -> None:
        self.source = source
        self.rules: dict[str, re.Pattern[str]] = {
            name: re.compile(pattern) for name, pattern in rules.items()
        }
        self.next_token: Token | None = None
        self.position = 0

    def consume(self, name: str) -> None:
        """Move beyond provided token name, if at current position."""
        if self.check(name):
            self.read()

    def check(self, name: str, *, peek: bool = False) -> bool:
        """Check whether the next token has the provided name.

        By default, if the check succeeds, the token *must* be read before
        another check. If `peek` is set to `True`, the token is not loaded and
        would need to be checked again.
        """
        assert (
            self.next_token is None
        ), f"Cannot check for {name!r}, already have {self.next_token!r}"
        assert name in self.rules, f"Unknown token name: {name!r}"

        expression = self.rules[name]

        match = expression.match(self.source, self.position)
        if match is None:
            return False
        if not peek:
            self.next_token = Token(name, match[0], self.position)
        return True

    def expect(self, name: str, *, expected: str) -> Token:
        """Expect a certain token name next, failing with a syntax error otherwise.

        The token is *not* read.
        """
        if not self.check(name):
            raise self.raise_syntax_error(f"Expected {expected}")
        return self.read()

    def read(self) -> Token:
        """Consume the next token and return it."""
        token = self.next_token
        assert token is not None

        self.position += len(token.text)
        self.next_token = None

        return token

    def raise_syntax_error(
        self,
        message: str,
        *,
        span_start: int | None = None,
        span_end: int | None = None,
    ) -> NoReturn:
        """Raise ParserSyntaxError at the given position."""
        span = (
            self.position if span_start is None else span_start,
            self.position if span_end is None else span_end,
        )
        raise ParserSyntaxError(
            message,
            source=self.source,
            span=span,
        )

    @contextlib.contextmanager
    def enclosing_tokens(
        self, open_token: str, close_token: str, *, around: str
    ) -> Iterator[None]:
        if self.check(open_token):
            open_position = self.position
            self.read()
        else:
            open_position = None

        yield

        if open_position is None:
            return

        if not self.check(close_token):
            self.raise_syntax_error(
                f"Expected matching {close_token} for {open_token}, after {around}",
                span_start=open_position,
            )

        self.read()

# This file is dual licensed under the terms of the Apache License, Version
# 2.0, and the BSD License. See the LICENSE file in the root of this repository
# for complete details.
"""
.. testsetup::

    from pip._vendor.packaging.version import parse, Version
"""

from __future__ import annotations

import itertools
import re
from typing import Any, Callable, NamedTuple, SupportsInt, Tuple, Union

from ._structures import Infinity, InfinityType, NegativeInfinity, NegativeInfinityType

__all__ = ["VERSION_PATTERN", "parse", "Version", "InvalidVersion"]

LocalType = Tuple[Union[int, str], ...]

CmpPrePostDevType = Union[InfinityType, NegativeInfinityType, Tuple[str, int]]
CmpLocalType = Union[
    NegativeInfinityType,
    Tuple[Union[Tuple[int, str], Tuple[NegativeInfinityType, Union[int, str]]], ...],
]
CmpKey = Tuple[
    int,
    Tuple[int, ...],
    CmpPrePostDevType,
    CmpPrePostDevType,
    CmpPrePostDevType,
    CmpLocalType,
]
VersionComparisonMethod = Callable[[CmpKey, CmpKey], bool]


class _Version(NamedTuple):
    epoch: int
    release: tuple[int, ...]
    dev: tuple[str, int] | None
    pre: tuple[str, int] | None
    post: tuple[str, int] | None
    local: LocalType | None


def parse(version: str) -> Version:
    """Parse the given version string.

    >>> parse('1.0.dev1')
    <Version('1.0.dev1')>

    :param version: The version string to parse.
    :raises InvalidVersion: When the version string is not a valid version.
    """
    return Version(version)


class InvalidVersion(ValueError):
    """Raised when a version string is not a valid version.

    >>> Version("invalid")
    Traceback (most recent call last):
        ...
    packaging.version.InvalidVersion: Invalid version: 'invalid'
    """


class _BaseVersion:
    _key: tuple[Any, ...]

    def __hash__(self) -> int:
        return hash(self._key)

    # Please keep the duplicated `isinstance` check
    # in the six comparisons hereunder
    # unless you find a way to avoid adding overhead function calls.
    def __lt__(self, other: _BaseVersion) -> bool:
        if not isinstance(other, _BaseVersion):
            return NotImplemented

        return self._key < other._key

    def __le__(self, other: _BaseVersion) -> bool:
        if not isinstance(other, _BaseVersion):
            return NotImplemented

        return self._key <= other._key

    def __eq__(self, other: object) -> bool:
        if not isinstance(other, _BaseVersion):
            return NotImplemented

        return self._key == other._key

    def __ge__(self, other: _BaseVersion) -> bool:
        if not isinstance(other, _BaseVersion):
            return NotImplemented

        return self._key >= other._key

    def __gt__(self, other: _BaseVersion) -> bool:
        if not isinstance(other, _BaseVersion):
            return NotImplemented

        return self._key > other._key

    def __ne__(self, other: object) -> bool:
        if not isinstance(other, _BaseVersion):
            return NotImplemented

        return self._key != other._key


# Deliberately not anchored to the start and end of the string, to make it
# easier for 3rd party code to reuse
_VERSION_PATTERN = r"""
    v?
    (?:
        (?:(?P<epoch>[0-9]+)!)?                           # epoch
        (?P<release>[0-9]+(?:\.[0-9]+)*)                  # release segment
        (?P<pre>                                          # pre-release
            [-_\.]?
            (?P<pre_l>alpha|a|beta|b|preview|pre|c|rc)
            [-_\.]?
            (?P<pre_n>[0-9]+)?
        )?
        (?P<post>                                         # post release
            (?:-(?P<post_n1>[0-9]+))
            |
            (?:
                [-_\.]?
                (?P<post_l>post|rev|r)
                [-_\.]?
                (?P<post_n2>[0-9]+)?
            )
        )?
        (?P<dev>                                          # dev release
            [-_\.]?
            (?P<dev_l>dev)
            [-_\.]?
            (?P<dev_n>[0-9]+)?
        )?
    )
    (?:\+(?P<local>[a-z0-9]+(?:[-_\.][a-z0-9]+)*))?       # local version
"""

VERSION_PATTERN = _VERSION_PATTERN
"""
A string containing the regular expression used to match a valid version.

The pattern is not anchored at either end, and is intended for embedding in larger
expressions (for example, matching a version number as part of a file name). The
regular expression should be compiled with the ``re.VERBOSE`` and ``re.IGNORECASE``
flags set.

:meta hide-value:
"""


class Version(_BaseVersion):
    """This class abstracts handling of a project's versions.

    A :class:`Version` instance is comparison aware and can be compared and
    sorted using the standard Python interfaces.

    >>> v1 = Version("1.0a5")
    >>> v2 = Version("1.0")
    >>> v1
    <Version('1.0a5')>
    >>> v2
    <Version('1.0')>
    >>> v1 < v2
    True
    >>> v1 == v2
    False
    >>> v1 > v2
    False
    >>> v1 >= v2
    False
    >>> v1 <= v2
    True
    """

    _regex = re.compile(r"^\s*" + VERSION_PATTERN + r"\s*$", re.VERBOSE | re.IGNORECASE)
    _key: CmpKey

    def __init__(self, version: str) -> None:
        """Initialize a Version object.

        :param version:
            The string representation of a version which will be parsed and normalized
            before use.
        :raises InvalidVersion:
            If the ``version`` does not conform to PEP 440 in any way then this
            exception will be raised.
        """

        # Validate the version and parse it into pieces
        match = self._regex.search(version)
        if not match:
            raise InvalidVersion(f"Invalid version: '{version}'")

        # Store the parsed out pieces of the version
        self._version = _Version(
            epoch=int(match.group("epoch")) if match.group("epoch") else 0,
            release=tuple(int(i) for i in match.group("release").split(".")),
            pre=_parse_letter_version(match.group("pre_l"), match.group("pre_n")),
            post=_parse_letter_version(
                match.group("post_l"), match.group("post_n1") or match.group("post_n2")
            ),
            dev=_parse_letter_version(match.group("dev_l"), match.group("dev_n")),
            local=_parse_local_version(match.group("local")),
        )

        # Generate a key which will be used for sorting
        self._key = _cmpkey(
            self._version.epoch,
            self._version.release,
            self._version.pre,
            self._version.post,
            self._version.dev,
            self._version.local,
        )

    def __repr__(self) -> str:
        """A representation of the Version that shows all internal state.

        >>> Version('1.0.0')
        <Version('1.0.0')>
        """
        return f"<Version('{self}')>"

    def __str__(self) -> str:
        """A string representation of the version that can be rounded-tripped.

        >>> str(Version("1.0a5"))
        '1.0a5'
        """
        parts = []

        # Epoch
        if self.epoch != 0:
            parts.append(f"{self.epoch}!")

        # Release segment
        parts.append(".".join(str(x) for x in self.release))

        # Pre-release
        if self.pre is not None:
            parts.append("".join(str(x) for x in self.pre))

        # Post-release
        if self.post is not None:
            parts.append(f".post{self.post}")

        # Development release
        if self.dev is not None:
            parts.append(f".dev{self.dev}")

        # Local version segment
        if self.local is not None:
            parts.append(f"+{self.local}")

        return "".join(parts)

    @property
    def epoch(self) -> int:
        """The epoch of the version.

        >>> Version("2.0.0").epoch
        0
        >>> Version("1!2.0.0").epoch
        1
        """
        return self._version.epoch

    @property
    def release(self) -> tuple[int, ...]:
        """The components of the "release" segment of the version.

        >>> Version("1.2.3").release
        (1, 2, 3)
        >>> Version("2.0.0").release
        (2, 0, 0)
        >>> Version("1!2.0.0.post0").release
        (2, 0, 0)

        Includes trailing zeroes but not the epoch or any pre-release / development /
        post-release suffixes.
        """
        return self._version.release

    @property
    def pre(self) -> tuple[str, int] | None:
        """The pre-release segment of the version.

        >>> print(Version("1.2.3").pre)
        None
        >>> Version("1.2.3a1").pre
        ('a', 1)
        >>> Version("1.2.3b1").pre
        ('b', 1)
        >>> Version("1.2.3rc1").pre
        ('rc', 1)
        """
        return self._version.pre

    @property
    def post(self) -> int | None:
        """The post-release number of the version.

        >>> print(Version("1.2.3").post)
        None
        >>> Version("1.2.3.post1").post
        1
        """
        return self._version.post[1] if self._version.post else None

    @property
    def dev(self) -> int | None:
        """The development number of the version.

        >>> print(Version("1.2.3").dev)
        None
        >>> Version("1.2.3.dev1").dev
        1
        """
        return self._version.dev[1] if self._version.dev else None

    @property
    def local(self) -> str | None:
        """The local version segment of the version.

        >>> print(Version("1.2.3").local)
        None
        >>> Version("1.2.3+abc").local
        'abc'
        """
        if self._version.local:
            return ".".join(str(x) for x in self._version.local)
        else:
            return None

    @property
    def public(self) -> str:
        """The public portion of the version.

        >>> Version("1.2.3").public
        '1.2.3'
        >>> Version("1.2.3+abc").public
        '1.2.3'
        >>> Version("1.2.3+abc.dev1").public
        '1.2.3'
        """
        return str(self).split("+", 1)[0]

    @property
    def base_version(self) -> str:
        """The "base version" of the version.

        >>> Version("1.2.3").base_version
        '1.2.3'
        >>> Version("1.2.3+abc").base_version
        '1.2.3'
        >>> Version("1!1.2.3+abc.dev1").base_version
        '1!1.2.3'

        The "base version" is the public version of the project without any pre or post
        release markers.
        """
        parts = []

        # Epoch
        if self.epoch != 0:
            parts.append(f"{self.epoch}!")

        # Release segment
        parts.append(".".join(str(x) for x in self.release))

        return "".join(parts)

    @property
    def is_prerelease(self) -> bool:
        """Whether this version is a pre-release.

        >>> Version("1.2.3").is_prerelease
        False
        >>> Version("1.2.3a1").is_prerelease
        True
        >>> Version("1.2.3b1").is_prerelease
        True
        >>> Version("1.2.3rc1").is_prerelease
        True
        >>> Version("1.2.3dev1").is_prerelease
        True
        """
        return self.dev is not None or self.pre is not None

    @property
    def is_postrelease(self) -> bool:
        """Whether this version is a post-release.

        >>> Version("1.2.3").is_postrelease
        False
        >>> Version("1.2.3.post1").is_postrelease
        True
        """
        return self.post is not None

    @property
    def is_devrelease(self) -> bool:
        """Whether this version is a development release.

        >>> Version("1.2.3").is_devrelease
        False
        >>> Version("1.2.3.dev1").is_devrelease
        True
        """
        return self.dev is not None

    @property
    def major(self) -> int:
        """The first item of :attr:`release` or ``0`` if unavailable.

        >>> Version("1.2.3").major
        1
        """
        return self.release[0] if len(self.release) >= 1 else 0

    @property
    def minor(self) -> int:
        """The second item of :attr:`release` or ``0`` if unavailable.

        >>> Version("1.2.3").minor
        2
        >>> Version("1").minor
        0
        """
        return self.release[1] if len(self.release) >= 2 else 0

    @property
    def micro(self) -> int:
        """The third item of :attr:`release` or ``0`` if unavailable.

        >>> Version("1.2.3").micro
        3
        >>> Version("1").micro
        0
        """
        return self.release[2] if len(self.release) >= 3 else 0


def _parse_letter_version(
    letter: str | None, number: str | bytes | SupportsInt | None
) -> tuple[str, int] | None:
    if letter:
        # We consider there to be an implicit 0 in a pre-release if there is
        # not a numeral associated with it.
        if number is None:
            number = 0

        # We normalize any letters to their lower case form
        letter = letter.lower()

        # We consider some words to be alternate spellings of other words and
        # in those cases we want to normalize the spellings to our preferred
        # spelling.
        if letter == "alpha":
            letter = "a"
        elif letter == "beta":
            letter = "b"
        elif letter in ["c", "pre", "preview"]:
            letter = "rc"
        elif letter in ["rev", "r"]:
            letter = "post"

        return letter, int(number)
    if not letter and number:
        # We assume if we are given a number, but we are not given a letter
        # then this is using the implicit post release syntax (e.g. 1.0-1)
        letter = "post"

        return letter, int(number)

    return None


_local_version_separators = re.compile(r"[\._-]")


def _parse_local_version(local: str | None) -> LocalType | None:
    """
    Takes a string like abc.1.twelve and turns it into ("abc", 1, "twelve").
    """
    if local is not None:
        return tuple(
            part.lower() if not part.isdigit() else int(part)
            for part in _local_version_separators.split(local)
        )
    return None


def _cmpkey(
    epoch: int,
    release: tuple[int, ...],
    pre: tuple[str, int] | None,
    post: tuple[str, int] | None,
    dev: tuple[str, int] | None,
    local: LocalType | None,
) -> CmpKey:
    # When we compare a release version, we want to compare it with all of the
    # trailing zeros removed. So we'll use a reverse the list, drop all the now
    # leading zeros until we come to something non zero, then take the rest
    # re-reverse it back into the correct order and make it a tuple and use
    # that for our sorting key.
    _release = tuple(
        reversed(list(itertools.dropwhile(lambda x: x == 0, reversed(release))))
    )

    # We need to "trick" the sorting algorithm to put 1.0.dev0 before 1.0a0.
    # We'll do this by abusing the pre segment, but we _only_ want to do this
    # if there is not a pre or a post segment. If we have one of those then
    # the normal sorting rules will handle this case correctly.
    if pre is None and post is None and dev is not None:
        _pre: CmpPrePostDevType = NegativeInfinity
    # Versions without a pre-release (except as noted above) should sort after
    # those with one.
    elif pre is None:
        _pre = Infinity
    else:
        _pre = pre

    # Versions without a post segment should sort before those with one.
    if post is None:
        _post: CmpPrePostDevType = NegativeInfinity

    else:
        _post = post

    # Versions without a development segment should sort after those with one.
    if dev is None:
        _dev: CmpPrePostDevType = Infinity

    else:
        _dev = dev

    if local is None:
        # Versions without a local segment should sort before those with one.
        _local: CmpLocalType = NegativeInfinity
    else:
        # Versions with a local segment need that segment parsed to implement
        # the sorting rules in PEP440.
        # - Alpha numeric segments sort before numeric segments
        # - Alpha numeric segments sort lexicographically
        # - Numeric segments sort numerically
        # - Shorter versions sort before longer versions when the prefixes
        #   match exactly
        _local = tuple(
            (i, "") if isinstance(i, int) else (NegativeInfinity, i) for i in local
        )

    return epoch, _release, _pre, _post, _dev, _local

"""Legacy editable installation process, i.e. `setup.py develop`.
"""

import logging
from typing import Optional, Sequence

from pip._internal.build_env import BuildEnvironment
from pip._internal.utils.logging import indent_log
from pip._internal.utils.setuptools_build import make_setuptools_develop_args
from pip._internal.utils.subprocess import call_subprocess

logger = logging.getLogger(__name__)


def install_editable(
    *,
    global_options: Sequence[str],
    prefix: Optional[str],
    home: Optional[str],
    use_user_site: bool,
    name: str,
    setup_py_path: str,
    isolated: bool,
    build_env: BuildEnvironment,
    unpacked_source_directory: str,
) -> None:
    """Install a package in editable mode. Most arguments are pass-through
    to setuptools.
    """
    logger.info("Running setup.py develop for %s", name)

    args = make_setuptools_develop_args(
        setup_py_path,
        global_options=global_options,
        no_user_config=isolated,
        prefix=prefix,
        home=home,
        use_user_site=use_user_site,
    )

    with indent_log():
        with build_env:
            call_subprocess(
                args,
                command_desc="python setup.py develop",
                cwd=unpacked_source_directory,
            )

__version__ = '3.7'

from typing import Iterable, Tuple, TypeVar

T = TypeVar("T")


def loop_first(values: Iterable[T]) -> Iterable[Tuple[bool, T]]:
    """Iterate and generate a tuple with a flag for first value."""
    iter_values = iter(values)
    try:
        value = next(iter_values)
    except StopIteration:
        return
    yield True, value
    for value in iter_values:
        yield False, value


def loop_last(values: Iterable[T]) -> Iterable[Tuple[bool, T]]:
    """Iterate and generate a tuple with a flag for last value."""
    iter_values = iter(values)
    try:
        previous_value = next(iter_values)
    except StopIteration:
        return
    for value in iter_values:
        yield False, previous_value
        previous_value = value
    yield True, previous_value


def loop_first_last(values: Iterable[T]) -> Iterable[Tuple[bool, bool, T]]:
    """Iterate and generate a tuple with a flag for first and last value."""
    iter_values = iter(values)
    try:
        previous_value = next(iter_values)
    except StopIteration:
        return
    first = True
    for value in iter_values:
        yield first, False, previous_value
        first = False
        previous_value = value
    yield first, True, previous_value