"""
This module uses ctypes to bind a whole bunch of functions and constants from
SecureTransport. The goal here is to provide the low-level API to
SecureTransport. These are essentially the C-level functions and constants, and
they're pretty gross to work with.

This code is a bastardised version of the code found in Will Bond's oscrypto
library. An enormous debt is owed to him for blazing this trail for us. For
that reason, this code should be considered to be covered both by urllib3's
license and by oscrypto's:

    Copyright (c) 2015-2016 Will Bond <will@wbond.net>

    Permission is hereby granted, free of charge, to any person obtaining a
    copy of this software and associated documentation files (the "Software"),
    to deal in the Software without restriction, including without limitation
    the rights to use, copy, modify, merge, publish, distribute, sublicense,
    and/or sell copies of the Software, and to permit persons to whom the
    Software is furnished to do so, subject to the following conditions:

    The above copyright notice and this permission notice shall be included in
    all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
    DEALINGS IN THE SOFTWARE.
"""
from __future__ import absolute_import

import platform
from ctypes import (
    CDLL,
    CFUNCTYPE,
    POINTER,
    c_bool,
    c_byte,
    c_char_p,
    c_int32,
    c_long,
    c_size_t,
    c_uint32,
    c_ulong,
    c_void_p,
)
from ctypes.util import find_library

from ...packages.six import raise_from

if platform.system() != "Darwin":
    raise ImportError("Only macOS is supported")

version = platform.mac_ver()[0]
version_info = tuple(map(int, version.split(".")))
if version_info < (10, 8):
    raise OSError(
        "Only OS X 10.8 and newer are supported, not %s.%s"
        % (version_info[0], version_info[1])
    )


def load_cdll(name, macos10_16_path):
    """Loads a CDLL by name, falling back to known path on 10.16+"""
    try:
        # Big Sur is technically 11 but we use 10.16 due to the Big Sur
        # beta being labeled as 10.16.
        if version_info >= (10, 16):
            path = macos10_16_path
        else:
            path = find_library(name)
        if not path:
            raise OSError  # Caught and reraised as 'ImportError'
        return CDLL(path, use_errno=True)
    except OSError:
        raise_from(ImportError("The library %s failed to load" % name), None)


Security = load_cdll(
    "Security", "/System/Library/Frameworks/Security.framework/Security"
)
CoreFoundation = load_cdll(
    "CoreFoundation",
    "/System/Library/Frameworks/CoreFoundation.framework/CoreFoundation",
)


Boolean = c_bool
CFIndex = c_long
CFStringEncoding = c_uint32
CFData = c_void_p
CFString = c_void_p
CFArray = c_void_p
CFMutableArray = c_void_p
CFDictionary = c_void_p
CFError = c_void_p
CFType = c_void_p
CFTypeID = c_ulong

CFTypeRef = POINTER(CFType)
CFAllocatorRef = c_void_p

OSStatus = c_int32

CFDataRef = POINTER(CFData)
CFStringRef = POINTER(CFString)
CFArrayRef = POINTER(CFArray)
CFMutableArrayRef = POINTER(CFMutableArray)
CFDictionaryRef = POINTER(CFDictionary)
CFArrayCallBacks = c_void_p
CFDictionaryKeyCallBacks = c_void_p
CFDictionaryValueCallBacks = c_void_p

SecCertificateRef = POINTER(c_void_p)
SecExternalFormat = c_uint32
SecExternalItemType = c_uint32
SecIdentityRef = POINTER(c_void_p)
SecItemImportExportFlags = c_uint32
SecItemImportExportKeyParameters = c_void_p
SecKeychainRef = POINTER(c_void_p)
SSLProtocol = c_uint32
SSLCipherSuite = c_uint32
SSLContextRef = POINTER(c_void_p)
SecTrustRef = POINTER(c_void_p)
SSLConnectionRef = c_uint32
SecTrustResultType = c_uint32
SecTrustOptionFlags = c_uint32
SSLProtocolSide = c_uint32
SSLConnectionType = c_uint32
SSLSessionOption = c_uint32


try:
    Security.SecItemImport.argtypes = [
        CFDataRef,
        CFStringRef,
        POINTER(SecExternalFormat),
        POINTER(SecExternalItemType),
        SecItemImportExportFlags,
        POINTER(SecItemImportExportKeyParameters),
        SecKeychainRef,
        POINTER(CFArrayRef),
    ]
    Security.SecItemImport.restype = OSStatus

    Security.SecCertificateGetTypeID.argtypes = []
    Security.SecCertificateGetTypeID.restype = CFTypeID

    Security.SecIdentityGetTypeID.argtypes = []
    Security.SecIdentityGetTypeID.restype = CFTypeID

    Security.SecKeyGetTypeID.argtypes = []
    Security.SecKeyGetTypeID.restype = CFTypeID

    Security.SecCertificateCreateWithData.argtypes = [CFAllocatorRef, CFDataRef]
    Security.SecCertificateCreateWithData.restype = SecCertificateRef

    Security.SecCertificateCopyData.argtypes = [SecCertificateRef]
    Security.SecCertificateCopyData.restype = CFDataRef

    Security.SecCopyErrorMessageString.argtypes = [OSStatus, c_void_p]
    Security.SecCopyErrorMessageString.restype = CFStringRef

    Security.SecIdentityCreateWithCertificate.argtypes = [
        CFTypeRef,
        SecCertificateRef,
        POINTER(SecIdentityRef),
    ]
    Security.SecIdentityCreateWithCertificate.restype = OSStatus

    Security.SecKeychainCreate.argtypes = [
        c_char_p,
        c_uint32,
        c_void_p,
        Boolean,
        c_void_p,
        POINTER(SecKeychainRef),
    ]
    Security.SecKeychainCreate.restype = OSStatus

    Security.SecKeychainDelete.argtypes = [SecKeychainRef]
    Security.SecKeychainDelete.restype = OSStatus

    Security.SecPKCS12Import.argtypes = [
        CFDataRef,
        CFDictionaryRef,
        POINTER(CFArrayRef),
    ]
    Security.SecPKCS12Import.restype = OSStatus

    SSLReadFunc = CFUNCTYPE(OSStatus, SSLConnectionRef, c_void_p, POINTER(c_size_t))
    SSLWriteFunc = CFUNCTYPE(
        OSStatus, SSLConnectionRef, POINTER(c_byte), POINTER(c_size_t)
    )

    Security.SSLSetIOFuncs.argtypes = [SSLContextRef, SSLReadFunc, SSLWriteFunc]
    Security.SSLSetIOFuncs.restype = OSStatus

    Security.SSLSetPeerID.argtypes = [SSLContextRef, c_char_p, c_size_t]
    Security.SSLSetPeerID.restype = OSStatus

    Security.SSLSetCertificate.argtypes = [SSLContextRef, CFArrayRef]
    Security.SSLSetCertificate.restype = OSStatus

    Security.SSLSetCertificateAuthorities.argtypes = [SSLContextRef, CFTypeRef, Boolean]
    Security.SSLSetCertificateAuthorities.restype = OSStatus

    Security.SSLSetConnection.argtypes = [SSLContextRef, SSLConnectionRef]
    Security.SSLSetConnection.restype = OSStatus

    Security.SSLSetPeerDomainName.argtypes = [SSLContextRef, c_char_p, c_size_t]
    Security.SSLSetPeerDomainName.restype = OSStatus

    Security.SSLHandshake.argtypes = [SSLContextRef]
    Security.SSLHandshake.restype = OSStatus

    Security.SSLRead.argtypes = [SSLContextRef, c_char_p, c_size_t, POINTER(c_size_t)]
    Security.SSLRead.restype = OSStatus

    Security.SSLWrite.argtypes = [SSLContextRef, c_char_p, c_size_t, POINTER(c_size_t)]
    Security.SSLWrite.restype = OSStatus

    Security.SSLClose.argtypes = [SSLContextRef]
    Security.SSLClose.restype = OSStatus

    Security.SSLGetNumberSupportedCiphers.argtypes = [SSLContextRef, POINTER(c_size_t)]
    Security.SSLGetNumberSupportedCiphers.restype = OSStatus

    Security.SSLGetSupportedCiphers.argtypes = [
        SSLContextRef,
        POINTER(SSLCipherSuite),
        POINTER(c_size_t),
    ]
    Security.SSLGetSupportedCiphers.restype = OSStatus

    Security.SSLSetEnabledCiphers.argtypes = [
        SSLContextRef,
        POINTER(SSLCipherSuite),
        c_size_t,
    ]
    Security.SSLSetEnabledCiphers.restype = OSStatus

    Security.SSLGetNumberEnabledCiphers.argtype = [SSLContextRef, POINTER(c_size_t)]
    Security.SSLGetNumberEnabledCiphers.restype = OSStatus

    Security.SSLGetEnabledCiphers.argtypes = [
        SSLContextRef,
        POINTER(SSLCipherSuite),
        POINTER(c_size_t),
    ]
    Security.SSLGetEnabledCiphers.restype = OSStatus

    Security.SSLGetNegotiatedCipher.argtypes = [SSLContextRef, POINTER(SSLCipherSuite)]
    Security.SSLGetNegotiatedCipher.restype = OSStatus

    Security.SSLGetNegotiatedProtocolVersion.argtypes = [
        SSLContextRef,
        POINTER(SSLProtocol),
    ]
    Security.SSLGetNegotiatedProtocolVersion.restype = OSStatus

    Security.SSLCopyPeerTrust.argtypes = [SSLContextRef, POINTER(SecTrustRef)]
    Security.SSLCopyPeerTrust.restype = OSStatus

    Security.SecTrustSetAnchorCertificates.argtypes = [SecTrustRef, CFArrayRef]
    Security.SecTrustSetAnchorCertificates.restype = OSStatus

    Security.SecTrustSetAnchorCertificatesOnly.argstypes = [SecTrustRef, Boolean]
    Security.SecTrustSetAnchorCertificatesOnly.restype = OSStatus

    Security.SecTrustEvaluate.argtypes = [SecTrustRef, POINTER(SecTrustResultType)]
    Security.SecTrustEvaluate.restype = OSStatus

    Security.SecTrustGetCertificateCount.argtypes = [SecTrustRef]
    Security.SecTrustGetCertificateCount.restype = CFIndex

    Security.SecTrustGetCertificateAtIndex.argtypes = [SecTrustRef, CFIndex]
    Security.SecTrustGetCertificateAtIndex.restype = SecCertificateRef

    Security.SSLCreateContext.argtypes = [
        CFAllocatorRef,
        SSLProtocolSide,
        SSLConnectionType,
    ]
    Security.SSLCreateContext.restype = SSLContextRef

    Security.SSLSetSessionOption.argtypes = [SSLContextRef, SSLSessionOption, Boolean]
    Security.SSLSetSessionOption.restype = OSStatus

    Security.SSLSetProtocolVersionMin.argtypes = [SSLContextRef, SSLProtocol]
    Security.SSLSetProtocolVersionMin.restype = OSStatus

    Security.SSLSetProtocolVersionMax.argtypes = [SSLContextRef, SSLProtocol]
    Security.SSLSetProtocolVersionMax.restype = OSStatus

    try:
        Security.SSLSetALPNProtocols.argtypes = [SSLContextRef, CFArrayRef]
        Security.SSLSetALPNProtocols.restype = OSStatus
    except AttributeError:
        # Supported only in 10.12+
        pass

    Security.SecCopyErrorMessageString.argtypes = [OSStatus, c_void_p]
    Security.SecCopyErrorMessageString.restype = CFStringRef

    Security.SSLReadFunc = SSLReadFunc
    Security.SSLWriteFunc = SSLWriteFunc
    Security.SSLContextRef = SSLContextRef
    Security.SSLProtocol = SSLProtocol
    Security.SSLCipherSuite = SSLCipherSuite
    Security.SecIdentityRef = SecIdentityRef
    Security.SecKeychainRef = SecKeychainRef
    Security.SecTrustRef = SecTrustRef
    Security.SecTrustResultType = SecTrustResultType
    Security.SecExternalFormat = SecExternalFormat
    Security.OSStatus = OSStatus

    Security.kSecImportExportPassphrase = CFStringRef.in_dll(
        Security, "kSecImportExportPassphrase"
    )
    Security.kSecImportItemIdentity = CFStringRef.in_dll(
        Security, "kSecImportItemIdentity"
    )

    # CoreFoundation time!
    CoreFoundation.CFRetain.argtypes = [CFTypeRef]
    CoreFoundation.CFRetain.restype = CFTypeRef

    CoreFoundation.CFRelease.argtypes = [CFTypeRef]
    CoreFoundation.CFRelease.restype = None

    CoreFoundation.CFGetTypeID.argtypes = [CFTypeRef]
    CoreFoundation.CFGetTypeID.restype = CFTypeID

    CoreFoundation.CFStringCreateWithCString.argtypes = [
        CFAllocatorRef,
        c_char_p,
        CFStringEncoding,
    ]
    CoreFoundation.CFStringCreateWithCString.restype = CFStringRef

    CoreFoundation.CFStringGetCStringPtr.argtypes = [CFStringRef, CFStringEncoding]
    CoreFoundation.CFStringGetCStringPtr.restype = c_char_p

    CoreFoundation.CFStringGetCString.argtypes = [
        CFStringRef,
        c_char_p,
        CFIndex,
        CFStringEncoding,
    ]
    CoreFoundation.CFStringGetCString.restype = c_bool

    CoreFoundation.CFDataCreate.argtypes = [CFAllocatorRef, c_char_p, CFIndex]
    CoreFoundation.CFDataCreate.restype = CFDataRef

    CoreFoundation.CFDataGetLength.argtypes = [CFDataRef]
    CoreFoundation.CFDataGetLength.restype = CFIndex

    CoreFoundation.CFDataGetBytePtr.argtypes = [CFDataRef]
    CoreFoundation.CFDataGetBytePtr.restype = c_void_p

    CoreFoundation.CFDictionaryCreate.argtypes = [
        CFAllocatorRef,
        POINTER(CFTypeRef),
        POINTER(CFTypeRef),
        CFIndex,
        CFDictionaryKeyCallBacks,
        CFDictionaryValueCallBacks,
    ]
    CoreFoundation.CFDictionaryCreate.restype = CFDictionaryRef

    CoreFoundation.CFDictionaryGetValue.argtypes = [CFDictionaryRef, CFTypeRef]
    CoreFoundation.CFDictionaryGetValue.restype = CFTypeRef

    CoreFoundation.CFArrayCreate.argtypes = [
        CFAllocatorRef,
        POINTER(CFTypeRef),
        CFIndex,
        CFArrayCallBacks,
    ]
    CoreFoundation.CFArrayCreate.restype = CFArrayRef

    CoreFoundation.CFArrayCreateMutable.argtypes = [
        CFAllocatorRef,
        CFIndex,
        CFArrayCallBacks,
    ]
    CoreFoundation.CFArrayCreateMutable.restype = CFMutableArrayRef

    CoreFoundation.CFArrayAppendValue.argtypes = [CFMutableArrayRef, c_void_p]
    CoreFoundation.CFArrayAppendValue.restype = None

    CoreFoundation.CFArrayGetCount.argtypes = [CFArrayRef]
    CoreFoundation.CFArrayGetCount.restype = CFIndex

    CoreFoundation.CFArrayGetValueAtIndex.argtypes = [CFArrayRef, CFIndex]
    CoreFoundation.CFArrayGetValueAtIndex.restype = c_void_p

    CoreFoundation.kCFAllocatorDefault = CFAllocatorRef.in_dll(
        CoreFoundation, "kCFAllocatorDefault"
    )
    CoreFoundation.kCFTypeArrayCallBacks = c_void_p.in_dll(
        CoreFoundation, "kCFTypeArrayCallBacks"
    )
    CoreFoundation.kCFTypeDictionaryKeyCallBacks = c_void_p.in_dll(
        CoreFoundation, "kCFTypeDictionaryKeyCallBacks"
    )
    CoreFoundation.kCFTypeDictionaryValueCallBacks = c_void_p.in_dll(
        CoreFoundation, "kCFTypeDictionaryValueCallBacks"
    )

    CoreFoundation.CFTypeRef = CFTypeRef
    CoreFoundation.CFArrayRef = CFArrayRef
    CoreFoundation.CFStringRef = CFStringRef
    CoreFoundation.CFDictionaryRef = CFDictionaryRef

except (AttributeError):
    raise ImportError("Error initializing ctypes")


class CFConst(object):
    """
    A class object that acts as essentially a namespace for CoreFoundation
    constants.
    """

    kCFStringEncodingUTF8 = CFStringEncoding(0x08000100)


class SecurityConst(object):
    """
    A class object that acts as essentially a namespace for Security constants.
    """

    kSSLSessionOptionBreakOnServerAuth = 0

    kSSLProtocol2 = 1
    kSSLProtocol3 = 2
    kTLSProtocol1 = 4
    kTLSProtocol11 = 7
    kTLSProtocol12 = 8
    # SecureTransport does not support TLS 1.3 even if there's a constant for it
    kTLSProtocol13 = 10
    kTLSProtocolMaxSupported = 999

    kSSLClientSide = 1
    kSSLStreamType = 0

    kSecFormatPEMSequence = 10

    kSecTrustResultInvalid = 0
    kSecTrustResultProceed = 1
    # This gap is present on purpose: this was kSecTrustResultConfirm, which
    # is deprecated.
    kSecTrustResultDeny = 3
    kSecTrustResultUnspecified = 4
    kSecTrustResultRecoverableTrustFailure = 5
    kSecTrustResultFatalTrustFailure = 6
    kSecTrustResultOtherError = 7

    errSSLProtocol = -9800
    errSSLWouldBlock = -9803
    errSSLClosedGraceful = -9805
    errSSLClosedNoNotify = -9816
    errSSLClosedAbort = -9806

    errSSLXCertChainInvalid = -9807
    errSSLCrypto = -9809
    errSSLInternal = -9810
    errSSLCertExpired = -9814
    errSSLCertNotYetValid = -9815
    errSSLUnknownRootCert = -9812
    errSSLNoRootCert = -9813
    errSSLHostNameMismatch = -9843
    errSSLPeerHandshakeFail = -9824
    errSSLPeerUserCancelled = -9839
    errSSLWeakPeerEphemeralDHKey = -9850
    errSSLServerAuthCompleted = -9841
    errSSLRecordOverflow = -9847

    errSecVerifyFailed = -67808
    errSecNoTrustSettings = -25263
    errSecItemNotFound = -25300
    errSecInvalidTrustSettings = -25262

    # Cipher suites. We only pick the ones our default cipher string allows.
    # Source: https://developer.apple.com/documentation/security/1550981-ssl_cipher_suite_values
    TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 = 0xC02C
    TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 = 0xC030
    TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 = 0xC02B
    TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 = 0xC02F
    TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256 = 0xCCA9
    TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256 = 0xCCA8
    TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 = 0x009F
    TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 = 0x009E
    TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384 = 0xC024
    TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384 = 0xC028
    TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA = 0xC00A
    TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA = 0xC014
    TLS_DHE_RSA_WITH_AES_256_CBC_SHA256 = 0x006B
    TLS_DHE_RSA_WITH_AES_256_CBC_SHA = 0x0039
    TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256 = 0xC023
    TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 = 0xC027
    TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA = 0xC009
    TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA = 0xC013
    TLS_DHE_RSA_WITH_AES_128_CBC_SHA256 = 0x0067
    TLS_DHE_RSA_WITH_AES_128_CBC_SHA = 0x0033
    TLS_RSA_WITH_AES_256_GCM_SHA384 = 0x009D
    TLS_RSA_WITH_AES_128_GCM_SHA256 = 0x009C
    TLS_RSA_WITH_AES_256_CBC_SHA256 = 0x003D
    TLS_RSA_WITH_AES_128_CBC_SHA256 = 0x003C
    TLS_RSA_WITH_AES_256_CBC_SHA = 0x0035
    TLS_RSA_WITH_AES_128_CBC_SHA = 0x002F
    TLS_AES_128_GCM_SHA256 = 0x1301
    TLS_AES_256_GCM_SHA384 = 0x1302
    TLS_AES_128_CCM_8_SHA256 = 0x1305
    TLS_AES_128_CCM_SHA256 = 0x1304

from __future__ import annotations

from typing import IO, Callable


def get_fileno(file_like: IO[str]) -> int | None:
    """Get fileno() from a file, accounting for poorly implemented file-like objects.

    Args:
        file_like (IO): A file-like object.

    Returns:
        int | None: The result of fileno if available, or None if operation failed.
    """
    fileno: Callable[[], int] | None = getattr(file_like, "fileno", None)
    if fileno is not None:
        try:
            return fileno()
        except Exception:
            # `fileno` is documented as potentially raising a OSError
            # Alas, from the issues, there are so many poorly implemented file-like objects,
            # that `fileno()` can raise just about anything.
            return None
    return None

import collections
import itertools
import operator

from .providers import AbstractResolver
from .structs import DirectedGraph, IteratorMapping, build_iter_view

RequirementInformation = collections.namedtuple(
    "RequirementInformation", ["requirement", "parent"]
)


class ResolverException(Exception):
    """A base class for all exceptions raised by this module.

    Exceptions derived by this class should all be handled in this module. Any
    bubbling pass the resolver should be treated as a bug.
    """


class RequirementsConflicted(ResolverException):
    def __init__(self, criterion):
        super(RequirementsConflicted, self).__init__(criterion)
        self.criterion = criterion

    def __str__(self):
        return "Requirements conflict: {}".format(
            ", ".join(repr(r) for r in self.criterion.iter_requirement()),
        )


class InconsistentCandidate(ResolverException):
    def __init__(self, candidate, criterion):
        super(InconsistentCandidate, self).__init__(candidate, criterion)
        self.candidate = candidate
        self.criterion = criterion

    def __str__(self):
        return "Provided candidate {!r} does not satisfy {}".format(
            self.candidate,
            ", ".join(repr(r) for r in self.criterion.iter_requirement()),
        )


class Criterion(object):
    """Representation of possible resolution results of a package.

    This holds three attributes:

    * `information` is a collection of `RequirementInformation` pairs.
      Each pair is a requirement contributing to this criterion, and the
      candidate that provides the requirement.
    * `incompatibilities` is a collection of all known not-to-work candidates
      to exclude from consideration.
    * `candidates` is a collection containing all possible candidates deducted
      from the union of contributing requirements and known incompatibilities.
      It should never be empty, except when the criterion is an attribute of a
      raised `RequirementsConflicted` (in which case it is always empty).

    .. note::
        This class is intended to be externally immutable. **Do not** mutate
        any of its attribute containers.
    """

    def __init__(self, candidates, information, incompatibilities):
        self.candidates = candidates
        self.information = information
        self.incompatibilities = incompatibilities

    def __repr__(self):
        requirements = ", ".join(
            "({!r}, via={!r})".format(req, parent)
            for req, parent in self.information
        )
        return "Criterion({})".format(requirements)

    def iter_requirement(self):
        return (i.requirement for i in self.information)

    def iter_parent(self):
        return (i.parent for i in self.information)


class ResolutionError(ResolverException):
    pass


class ResolutionImpossible(ResolutionError):
    def __init__(self, causes):
        super(ResolutionImpossible, self).__init__(causes)
        # causes is a list of RequirementInformation objects
        self.causes = causes


class ResolutionTooDeep(ResolutionError):
    def __init__(self, round_count):
        super(ResolutionTooDeep, self).__init__(round_count)
        self.round_count = round_count


# Resolution state in a round.
State = collections.namedtuple("State", "mapping criteria backtrack_causes")


class Resolution(object):
    """Stateful resolution object.

    This is designed as a one-off object that holds information to kick start
    the resolution process, and holds the results afterwards.
    """

    def __init__(self, provider, reporter):
        self._p = provider
        self._r = reporter
        self._states = []

    @property
    def state(self):
        try:
            return self._states[-1]
        except IndexError:
            raise AttributeError("state")

    def _push_new_state(self):
        """Push a new state into history.

        This new state will be used to hold resolution results of the next
        coming round.
        """
        base = self._states[-1]
        state = State(
            mapping=base.mapping.copy(),
            criteria=base.criteria.copy(),
            backtrack_causes=base.backtrack_causes[:],
        )
        self._states.append(state)

    def _add_to_criteria(self, criteria, requirement, parent):
        self._r.adding_requirement(requirement=requirement, parent=parent)

        identifier = self._p.identify(requirement_or_candidate=requirement)
        criterion = criteria.get(identifier)
        if criterion:
            incompatibilities = list(criterion.incompatibilities)
        else:
            incompatibilities = []

        matches = self._p.find_matches(
            identifier=identifier,
            requirements=IteratorMapping(
                criteria,
                operator.methodcaller("iter_requirement"),
                {identifier: [requirement]},
            ),
            incompatibilities=IteratorMapping(
                criteria,
                operator.attrgetter("incompatibilities"),
                {identifier: incompatibilities},
            ),
        )

        if criterion:
            information = list(criterion.information)
            information.append(RequirementInformation(requirement, parent))
        else:
            information = [RequirementInformation(requirement, parent)]

        criterion = Criterion(
            candidates=build_iter_view(matches),
            information=information,
            incompatibilities=incompatibilities,
        )
        if not criterion.candidates:
            raise RequirementsConflicted(criterion)
        criteria[identifier] = criterion

    def _remove_information_from_criteria(self, criteria, parents):
        """Remove information from parents of criteria.

        Concretely, removes all values from each criterion's ``information``
        field that have one of ``parents`` as provider of the requirement.

        :param criteria: The criteria to update.
        :param parents: Identifiers for which to remove information from all criteria.
        """
        if not parents:
            return
        for key, criterion in criteria.items():
            criteria[key] = Criterion(
                criterion.candidates,
                [
                    information
                    for information in criterion.information
                    if (
                        information.parent is None
                        or self._p.identify(information.parent) not in parents
                    )
                ],
                criterion.incompatibilities,
            )

    def _get_preference(self, name):
        return self._p.get_preference(
            identifier=name,
            resolutions=self.state.mapping,
            candidates=IteratorMapping(
                self.state.criteria,
                operator.attrgetter("candidates"),
            ),
            information=IteratorMapping(
                self.state.criteria,
                operator.attrgetter("information"),
            ),
            backtrack_causes=self.state.backtrack_causes,
        )

    def _is_current_pin_satisfying(self, name, criterion):
        try:
            current_pin = self.state.mapping[name]
        except KeyError:
            return False
        return all(
            self._p.is_satisfied_by(requirement=r, candidate=current_pin)
            for r in criterion.iter_requirement()
        )

    def _get_updated_criteria(self, candidate):
        criteria = self.state.criteria.copy()
        for requirement in self._p.get_dependencies(candidate=candidate):
            self._add_to_criteria(criteria, requirement, parent=candidate)
        return criteria

    def _attempt_to_pin_criterion(self, name):
        criterion = self.state.criteria[name]

        causes = []
        for candidate in criterion.candidates:
            try:
                criteria = self._get_updated_criteria(candidate)
            except RequirementsConflicted as e:
                self._r.rejecting_candidate(e.criterion, candidate)
                causes.append(e.criterion)
                continue

            # Check the newly-pinned candidate actually works. This should
            # always pass under normal circumstances, but in the case of a
            # faulty provider, we will raise an error to notify the implementer
            # to fix find_matches() and/or is_satisfied_by().
            satisfied = all(
                self._p.is_satisfied_by(requirement=r, candidate=candidate)
                for r in criterion.iter_requirement()
            )
            if not satisfied:
                raise InconsistentCandidate(candidate, criterion)

            self._r.pinning(candidate=candidate)
            self.state.criteria.update(criteria)

            # Put newly-pinned candidate at the end. This is essential because
            # backtracking looks at this mapping to get the last pin.
            self.state.mapping.pop(name, None)
            self.state.mapping[name] = candidate

            return []

        # All candidates tried, nothing works. This criterion is a dead
        # end, signal for backtracking.
        return causes

    def _backjump(self, causes):
        """Perform backjumping.

        When we enter here, the stack is like this::

            [ state Z ]
            [ state Y ]
            [ state X ]
            .... earlier states are irrelevant.

        1. No pins worked for Z, so it does not have a pin.
        2. We want to reset state Y to unpinned, and pin another candidate.
        3. State X holds what state Y was before the pin, but does not
           have the incompatibility information gathered in state Y.

        Each iteration of the loop will:

        1.  Identify Z. The incompatibility is not always caused by the latest
            state. For example, given three requirements A, B and C, with
            dependencies A1, B1 and C1, where A1 and B1 are incompatible: the
            last state might be related to C, so we want to discard the
            previous state.
        2.  Discard Z.
        3.  Discard Y but remember its incompatibility information gathered
            previously, and the failure we're dealing with right now.
        4.  Push a new state Y' based on X, and apply the incompatibility
            information from Y to Y'.
        5a. If this causes Y' to conflict, we need to backtrack again. Make Y'
            the new Z and go back to step 2.
        5b. If the incompatibilities apply cleanly, end backtracking.
        """
        incompatible_reqs = itertools.chain(
            (c.parent for c in causes if c.parent is not None),
            (c.requirement for c in causes),
        )
        incompatible_deps = {self._p.identify(r) for r in incompatible_reqs}
        while len(self._states) >= 3:
            # Remove the state that triggered backtracking.
            del self._states[-1]

            # Ensure to backtrack to a state that caused the incompatibility
            incompatible_state = False
            while not incompatible_state:
                # Retrieve the last candidate pin and known incompatibilities.
                try:
                    broken_state = self._states.pop()
                    name, candidate = broken_state.mapping.popitem()
                except (IndexError, KeyError):
                    raise ResolutionImpossible(causes)
                current_dependencies = {
                    self._p.identify(d)
                    for d in self._p.get_dependencies(candidate)
                }
                incompatible_state = not current_dependencies.isdisjoint(
                    incompatible_deps
                )

            incompatibilities_from_broken = [
                (k, list(v.incompatibilities))
                for k, v in broken_state.criteria.items()
            ]

            # Also mark the newly known incompatibility.
            incompatibilities_from_broken.append((name, [candidate]))

            # Create a new state from the last known-to-work one, and apply
            # the previously gathered incompatibility information.
            def _patch_criteria():
                for k, incompatibilities in incompatibilities_from_broken:
                    if not incompatibilities:
                        continue
                    try:
                        criterion = self.state.criteria[k]
                    except KeyError:
                        continue
                    matches = self._p.find_matches(
                        identifier=k,
                        requirements=IteratorMapping(
                            self.state.criteria,
                            operator.methodcaller("iter_requirement"),
                        ),
                        incompatibilities=IteratorMapping(
                            self.state.criteria,
                            operator.attrgetter("incompatibilities"),
                            {k: incompatibilities},
                        ),
                    )
                    candidates = build_iter_view(matches)
                    if not candidates:
                        return False
                    incompatibilities.extend(criterion.incompatibilities)
                    self.state.criteria[k] = Criterion(
                        candidates=candidates,
                        information=list(criterion.information),
                        incompatibilities=incompatibilities,
                    )
                return True

            self._push_new_state()
            success = _patch_criteria()

            # It works! Let's work on this new state.
            if success:
                return True

            # State does not work after applying known incompatibilities.
            # Try the still previous state.

        # No way to backtrack anymore.
        return False

    def resolve(self, requirements, max_rounds):
        if self._states:
            raise RuntimeError("already resolved")

        self._r.starting()

        # Initialize the root state.
        self._states = [
            State(
                mapping=collections.OrderedDict(),
                criteria={},
                backtrack_causes=[],
            )
        ]
        for r in requirements:
            try:
                self._add_to_criteria(self.state.criteria, r, parent=None)
            except RequirementsConflicted as e:
                raise ResolutionImpossible(e.criterion.information)

        # The root state is saved as a sentinel so the first ever pin can have
        # something to backtrack to if it fails. The root state is basically
        # pinning the virtual "root" package in the graph.
        self._push_new_state()

        for round_index in range(max_rounds):
            self._r.starting_round(index=round_index)

            unsatisfied_names = [
                key
                for key, criterion in self.state.criteria.items()
                if not self._is_current_pin_satisfying(key, criterion)
            ]

            # All criteria are accounted for. Nothing more to pin, we are done!
            if not unsatisfied_names:
                self._r.ending(state=self.state)
                return self.state

            # keep track of satisfied names to calculate diff after pinning
            satisfied_names = set(self.state.criteria.keys()) - set(
                unsatisfied_names
            )

            # Choose the most preferred unpinned criterion to try.
            name = min(unsatisfied_names, key=self._get_preference)
            failure_causes = self._attempt_to_pin_criterion(name)

            if failure_causes:
                causes = [i for c in failure_causes for i in c.information]
                # Backjump if pinning fails. The backjump process puts us in
                # an unpinned state, so we can work on it in the next round.
                self._r.resolving_conflicts(causes=causes)
                success = self._backjump(causes)
                self.state.backtrack_causes[:] = causes

                # Dead ends everywhere. Give up.
                if not success:
                    raise ResolutionImpossible(self.state.backtrack_causes)
            else:
                # discard as information sources any invalidated names
                # (unsatisfied names that were previously satisfied)
                newly_unsatisfied_names = {
                    key
                    for key, criterion in self.state.criteria.items()
                    if key in satisfied_names
                    and not self._is_current_pin_satisfying(key, criterion)
                }
                self._remove_information_from_criteria(
                    self.state.criteria, newly_unsatisfied_names
                )
                # Pinning was successful. Push a new state to do another pin.
                self._push_new_state()

            self._r.ending_round(index=round_index, state=self.state)

        raise ResolutionTooDeep(max_rounds)


def _has_route_to_root(criteria, key, all_keys, connected):
    if key in connected:
        return True
    if key not in criteria:
        return False
    for p in criteria[key].iter_parent():
        try:
            pkey = all_keys[id(p)]
        except KeyError:
            continue
        if pkey in connected:
            connected.add(key)
            return True
        if _has_route_to_root(criteria, pkey, all_keys, connected):
            connected.add(key)
            return True
    return False


Result = collections.namedtuple("Result", "mapping graph criteria")


def _build_result(state):
    mapping = state.mapping
    all_keys = {id(v): k for k, v in mapping.items()}
    all_keys[id(None)] = None

    graph = DirectedGraph()
    graph.add(None)  # Sentinel as root dependencies' parent.

    connected = {None}
    for key, criterion in state.criteria.items():
        if not _has_route_to_root(state.criteria, key, all_keys, connected):
            continue
        if key not in graph:
            graph.add(key)
        for p in criterion.iter_parent():
            try:
                pkey = all_keys[id(p)]
            except KeyError:
                continue
            if pkey not in graph:
                graph.add(pkey)
            graph.connect(pkey, key)

    return Result(
        mapping={k: v for k, v in mapping.items() if k in connected},
        graph=graph,
        criteria=state.criteria,
    )


class Resolver(AbstractResolver):
    """The thing that performs the actual resolution work."""

    base_exception = ResolverException

    def resolve(self, requirements, max_rounds=100):
        """Take a collection of constraints, spit out the resolution result.

        The return value is a representation to the final resolution result. It
        is a tuple subclass with three public members:

        * `mapping`: A dict of resolved candidates. Each key is an identifier
            of a requirement (as returned by the provider's `identify` method),
            and the value is the resolved candidate.
        * `graph`: A `DirectedGraph` instance representing the dependency tree.
            The vertices are keys of `mapping`, and each edge represents *why*
            a particular package is included. A special vertex `None` is
            included to represent parents of user-supplied requirements.
        * `criteria`: A dict of "criteria" that hold detailed information on
            how edges in the graph are derived. Each key is an identifier of a
            requirement, and the value is a `Criterion` instance.

        The following exceptions may be raised if a resolution cannot be found:

        * `ResolutionImpossible`: A resolution cannot be found for the given
            combination of requirements. The `causes` attribute of the
            exception is a list of (requirement, parent), giving the
            requirements that could not be satisfied.
        * `ResolutionTooDeep`: The dependency tree is too deeply nested and
            the resolver gave up. This is usually caused by a circular
            dependency, but you can try to resolve this by increasing the
            `max_rounds` argument.
        """
        resolution = Resolution(self.provider, self.reporter)
        state = resolution.resolve(requirements, max_rounds=max_rounds)
        return _build_result(state)

"""
SecureTranport support for urllib3 via ctypes.

This makes platform-native TLS available to urllib3 users on macOS without the
use of a compiler. This is an important feature because the Python Package
Index is moving to become a TLSv1.2-or-higher server, and the default OpenSSL
that ships with macOS is not capable of doing TLSv1.2. The only way to resolve
this is to give macOS users an alternative solution to the problem, and that
solution is to use SecureTransport.

We use ctypes here because this solution must not require a compiler. That's
because pip is not allowed to require a compiler either.

This is not intended to be a seriously long-term solution to this problem.
The hope is that PEP 543 will eventually solve this issue for us, at which
point we can retire this contrib module. But in the short term, we need to
solve the impending tire fire that is Python on Mac without this kind of
contrib module. So...here we are.

To use this module, simply import and inject it::

    import pip._vendor.urllib3.contrib.securetransport as securetransport
    securetransport.inject_into_urllib3()

Happy TLSing!

This code is a bastardised version of the code found in Will Bond's oscrypto
library. An enormous debt is owed to him for blazing this trail for us. For
that reason, this code should be considered to be covered both by urllib3's
license and by oscrypto's:

.. code-block::

    Copyright (c) 2015-2016 Will Bond <will@wbond.net>

    Permission is hereby granted, free of charge, to any person obtaining a
    copy of this software and associated documentation files (the "Software"),
    to deal in the Software without restriction, including without limitation
    the rights to use, copy, modify, merge, publish, distribute, sublicense,
    and/or sell copies of the Software, and to permit persons to whom the
    Software is furnished to do so, subject to the following conditions:

    The above copyright notice and this permission notice shall be included in
    all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
    DEALINGS IN THE SOFTWARE.
"""
from __future__ import absolute_import

import contextlib
import ctypes
import errno
import os.path
import shutil
import socket
import ssl
import struct
import threading
import weakref

from .. import util
from ..packages import six
from ..util.ssl_ import PROTOCOL_TLS_CLIENT
from ._securetransport.bindings import CoreFoundation, Security, SecurityConst
from ._securetransport.low_level import (
    _assert_no_error,
    _build_tls_unknown_ca_alert,
    _cert_array_from_pem,
    _create_cfstring_array,
    _load_client_cert_chain,
    _temporary_keychain,
)

try:  # Platform-specific: Python 2
    from socket import _fileobject
except ImportError:  # Platform-specific: Python 3
    _fileobject = None
    from ..packages.backports.makefile import backport_makefile

__all__ = ["inject_into_urllib3", "extract_from_urllib3"]

# SNI always works
HAS_SNI = True

orig_util_HAS_SNI = util.HAS_SNI
orig_util_SSLContext = util.ssl_.SSLContext

# This dictionary is used by the read callback to obtain a handle to the
# calling wrapped socket. This is a pretty silly approach, but for now it'll
# do. I feel like I should be able to smuggle a handle to the wrapped socket
# directly in the SSLConnectionRef, but for now this approach will work I
# guess.
#
# We need to lock around this structure for inserts, but we don't do it for
# reads/writes in the callbacks. The reasoning here goes as follows:
#
#    1. It is not possible to call into the callbacks before the dictionary is
#       populated, so once in the callback the id must be in the dictionary.
#    2. The callbacks don't mutate the dictionary, they only read from it, and
#       so cannot conflict with any of the insertions.
#
# This is good: if we had to lock in the callbacks we'd drastically slow down
# the performance of this code.
_connection_refs = weakref.WeakValueDictionary()
_connection_ref_lock = threading.Lock()

# Limit writes to 16kB. This is OpenSSL's limit, but we'll cargo-cult it over
# for no better reason than we need *a* limit, and this one is right there.
SSL_WRITE_BLOCKSIZE = 16384

# This is our equivalent of util.ssl_.DEFAULT_CIPHERS, but expanded out to
# individual cipher suites. We need to do this because this is how
# SecureTransport wants them.
CIPHER_SUITES = [
    SecurityConst.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
    SecurityConst.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
    SecurityConst.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
    SecurityConst.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
    SecurityConst.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256,
    SecurityConst.TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256,
    SecurityConst.TLS_DHE_RSA_WITH_AES_256_GCM_SHA384,
    SecurityConst.TLS_DHE_RSA_WITH_AES_128_GCM_SHA256,
    SecurityConst.TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384,
    SecurityConst.TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA,
    SecurityConst.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256,
    SecurityConst.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA,
    SecurityConst.TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384,
    SecurityConst.TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
    SecurityConst.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256,
    SecurityConst.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA,
    SecurityConst.TLS_DHE_RSA_WITH_AES_256_CBC_SHA256,
    SecurityConst.TLS_DHE_RSA_WITH_AES_256_CBC_SHA,
    SecurityConst.TLS_DHE_RSA_WITH_AES_128_CBC_SHA256,
    SecurityConst.TLS_DHE_RSA_WITH_AES_128_CBC_SHA,
    SecurityConst.TLS_AES_256_GCM_SHA384,
    SecurityConst.TLS_AES_128_GCM_SHA256,
    SecurityConst.TLS_RSA_WITH_AES_256_GCM_SHA384,
    SecurityConst.TLS_RSA_WITH_AES_128_GCM_SHA256,
    SecurityConst.TLS_AES_128_CCM_8_SHA256,
    SecurityConst.TLS_AES_128_CCM_SHA256,
    SecurityConst.TLS_RSA_WITH_AES_256_CBC_SHA256,
    SecurityConst.TLS_RSA_WITH_AES_128_CBC_SHA256,
    SecurityConst.TLS_RSA_WITH_AES_256_CBC_SHA,
    SecurityConst.TLS_RSA_WITH_AES_128_CBC_SHA,
]

# Basically this is simple: for PROTOCOL_SSLv23 we turn it into a low of
# TLSv1 and a high of TLSv1.2. For everything else, we pin to that version.
# TLSv1 to 1.2 are supported on macOS 10.8+
_protocol_to_min_max = {
    util.PROTOCOL_TLS: (SecurityConst.kTLSProtocol1, SecurityConst.kTLSProtocol12),
    PROTOCOL_TLS_CLIENT: (SecurityConst.kTLSProtocol1, SecurityConst.kTLSProtocol12),
}

if hasattr(ssl, "PROTOCOL_SSLv2"):
    _protocol_to_min_max[ssl.PROTOCOL_SSLv2] = (
        SecurityConst.kSSLProtocol2,
        SecurityConst.kSSLProtocol2,
    )
if hasattr(ssl, "PROTOCOL_SSLv3"):
    _protocol_to_min_max[ssl.PROTOCOL_SSLv3] = (
        SecurityConst.kSSLProtocol3,
        SecurityConst.kSSLProtocol3,
    )
if hasattr(ssl, "PROTOCOL_TLSv1"):
    _protocol_to_min_max[ssl.PROTOCOL_TLSv1] = (
        SecurityConst.kTLSProtocol1,
        SecurityConst.kTLSProtocol1,
    )
if hasattr(ssl, "PROTOCOL_TLSv1_1"):
    _protocol_to_min_max[ssl.PROTOCOL_TLSv1_1] = (
        SecurityConst.kTLSProtocol11,
        SecurityConst.kTLSProtocol11,
    )
if hasattr(ssl, "PROTOCOL_TLSv1_2"):
    _protocol_to_min_max[ssl.PROTOCOL_TLSv1_2] = (
        SecurityConst.kTLSProtocol12,
        SecurityConst.kTLSProtocol12,
    )


def inject_into_urllib3():
    """
    Monkey-patch urllib3 with SecureTransport-backed SSL-support.
    """
    util.SSLContext = SecureTransportContext
    util.ssl_.SSLContext = SecureTransportContext
    util.HAS_SNI = HAS_SNI
    util.ssl_.HAS_SNI = HAS_SNI
    util.IS_SECURETRANSPORT = True
    util.ssl_.IS_SECURETRANSPORT = True


def extract_from_urllib3():
    """
    Undo monkey-patching by :func:`inject_into_urllib3`.
    """
    util.SSLContext = orig_util_SSLContext
    util.ssl_.SSLContext = orig_util_SSLContext
    util.HAS_SNI = orig_util_HAS_SNI
    util.ssl_.HAS_SNI = orig_util_HAS_SNI
    util.IS_SECURETRANSPORT = False
    util.ssl_.IS_SECURETRANSPORT = False


def _read_callback(connection_id, data_buffer, data_length_pointer):
    """
    SecureTransport read callback. This is called by ST to request that data
    be returned from the socket.
    """
    wrapped_socket = None
    try:
        wrapped_socket = _connection_refs.get(connection_id)
        if wrapped_socket is None:
            return SecurityConst.errSSLInternal
        base_socket = wrapped_socket.socket

        requested_length = data_length_pointer[0]

        timeout = wrapped_socket.gettimeout()
        error = None
        read_count = 0

        try:
            while read_count < requested_length:
                if timeout is None or timeout >= 0:
                    if not util.wait_for_read(base_socket, timeout):
                        raise socket.error(errno.EAGAIN, "timed out")

                remaining = requested_length - read_count
                buffer = (ctypes.c_char * remaining).from_address(
                    data_buffer + read_count
                )
                chunk_size = base_socket.recv_into(buffer, remaining)
                read_count += chunk_size
                if not chunk_size:
                    if not read_count:
                        return SecurityConst.errSSLClosedGraceful
                    break
        except (socket.error) as e:
            error = e.errno

            if error is not None and error != errno.EAGAIN:
                data_length_pointer[0] = read_count
                if error == errno.ECONNRESET or error == errno.EPIPE:
                    return SecurityConst.errSSLClosedAbort
                raise

        data_length_pointer[0] = read_count

        if read_count != requested_length:
            return SecurityConst.errSSLWouldBlock

        return 0
    except Exception as e:
        if wrapped_socket is not None:
            wrapped_socket._exception = e
        return SecurityConst.errSSLInternal


def _write_callback(connection_id, data_buffer, data_length_pointer):
    """
    SecureTransport write callback. This is called by ST to request that data
    actually be sent on the network.
    """
    wrapped_socket = None
    try:
        wrapped_socket = _connection_refs.get(connection_id)
        if wrapped_socket is None:
            return SecurityConst.errSSLInternal
        base_socket = wrapped_socket.socket

        bytes_to_write = data_length_pointer[0]
        data = ctypes.string_at(data_buffer, bytes_to_write)

        timeout = wrapped_socket.gettimeout()
        error = None
        sent = 0

        try:
            while sent < bytes_to_write:
                if timeout is None or timeout >= 0:
                    if not util.wait_for_write(base_socket, timeout):
                        raise socket.error(errno.EAGAIN, "timed out")
                chunk_sent = base_socket.send(data)
                sent += chunk_sent

                # This has some needless copying here, but I'm not sure there's
                # much value in optimising this data path.
                data = data[chunk_sent:]
        except (socket.error) as e:
            error = e.errno

            if error is not None and error != errno.EAGAIN:
                data_length_pointer[0] = sent
                if error == errno.ECONNRESET or error == errno.EPIPE:
                    return SecurityConst.errSSLClosedAbort
                raise

        data_length_pointer[0] = sent

        if sent != bytes_to_write:
            return SecurityConst.errSSLWouldBlock

        return 0
    except Exception as e:
        if wrapped_socket is not None:
            wrapped_socket._exception = e
        return SecurityConst.errSSLInternal


# We need to keep these two objects references alive: if they get GC'd while
# in use then SecureTransport could attempt to call a function that is in freed
# memory. That would be...uh...bad. Yeah, that's the word. Bad.
_read_callback_pointer = Security.SSLReadFunc(_read_callback)
_write_callback_pointer = Security.SSLWriteFunc(_write_callback)


class WrappedSocket(object):
    """
    API-compatibility wrapper for Python's OpenSSL wrapped socket object.

    Note: _makefile_refs, _drop(), and _reuse() are needed for the garbage
    collector of PyPy.
    """

    def __init__(self, socket):
        self.socket = socket
        self.context = None
        self._makefile_refs = 0
        self._closed = False
        self._exception = None
        self._keychain = None
        self._keychain_dir = None
        self._client_cert_chain = None

        # We save off the previously-configured timeout and then set it to
        # zero. This is done because we use select and friends to handle the
        # timeouts, but if we leave the timeout set on the lower socket then
        # Python will "kindly" call select on that socket again for us. Avoid
        # that by forcing the timeout to zero.
        self._timeout = self.socket.gettimeout()
        self.socket.settimeout(0)

    @contextlib.contextmanager
    def _raise_on_error(self):
        """
        A context manager that can be used to wrap calls that do I/O from
        SecureTransport. If any of the I/O callbacks hit an exception, this
        context manager will correctly propagate the exception after the fact.
        This avoids silently swallowing those exceptions.

        It also correctly forces the socket closed.
        """
        self._exception = None

        # We explicitly don't catch around this yield because in the unlikely
        # event that an exception was hit in the block we don't want to swallow
        # it.
        yield
        if self._exception is not None:
            exception, self._exception = self._exception, None
            self.close()
            raise exception

    def _set_ciphers(self):
        """
        Sets up the allowed ciphers. By default this matches the set in
        util.ssl_.DEFAULT_CIPHERS, at least as supported by macOS. This is done
        custom and doesn't allow changing at this time, mostly because parsing
        OpenSSL cipher strings is going to be a freaking nightmare.
        """
        ciphers = (Security.SSLCipherSuite * len(CIPHER_SUITES))(*CIPHER_SUITES)
        result = Security.SSLSetEnabledCiphers(
            self.context, ciphers, len(CIPHER_SUITES)
        )
        _assert_no_error(result)

    def _set_alpn_protocols(self, protocols):
        """
        Sets up the ALPN protocols on the context.
        """
        if not protocols:
            return
        protocols_arr = _create_cfstring_array(protocols)
        try:
            result = Security.SSLSetALPNProtocols(self.context, protocols_arr)
            _assert_no_error(result)
        finally:
            CoreFoundation.CFRelease(protocols_arr)

    def _custom_validate(self, verify, trust_bundle):
        """
        Called when we have set custom validation. We do this in two cases:
        first, when cert validation is entirely disabled; and second, when
        using a custom trust DB.
        Raises an SSLError if the connection is not trusted.
        """
        # If we disabled cert validation, just say: cool.
        if not verify:
            return

        successes = (
            SecurityConst.kSecTrustResultUnspecified,
            SecurityConst.kSecTrustResultProceed,
        )
        try:
            trust_result = self._evaluate_trust(trust_bundle)
            if trust_result in successes:
                return
            reason = "error code: %d" % (trust_result,)
        except Exception as e:
            # Do not trust on error
            reason = "exception: %r" % (e,)

        # SecureTransport does not send an alert nor shuts down the connection.
        rec = _build_tls_unknown_ca_alert(self.version())
        self.socket.sendall(rec)
        # close the connection immediately
        # l_onoff = 1, activate linger
        # l_linger = 0, linger for 0 seoncds
        opts = struct.pack("ii", 1, 0)
        self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_LINGER, opts)
        self.close()
        raise ssl.SSLError("certificate verify failed, %s" % reason)

    def _evaluate_trust(self, trust_bundle):
        # We want data in memory, so load it up.
        if os.path.isfile(trust_bundle):
            with open(trust_bundle, "rb") as f:
                trust_bundle = f.read()

        cert_array = None
        trust = Security.SecTrustRef()

        try:
            # Get a CFArray that contains the certs we want.
            cert_array = _cert_array_from_pem(trust_bundle)

            # Ok, now the hard part. We want to get the SecTrustRef that ST has
            # created for this connection, shove our CAs into it, tell ST to
            # ignore everything else it knows, and then ask if it can build a
            # chain. This is a buuuunch of code.
            result = Security.SSLCopyPeerTrust(self.context, ctypes.byref(trust))
            _assert_no_error(result)
            if not trust:
                raise ssl.SSLError("Failed to copy trust reference")

            result = Security.SecTrustSetAnchorCertificates(trust, cert_array)
            _assert_no_error(result)

            result = Security.SecTrustSetAnchorCertificatesOnly(trust, True)
            _assert_no_error(result)

            trust_result = Security.SecTrustResultType()
            result = Security.SecTrustEvaluate(trust, ctypes.byref(trust_result))
            _assert_no_error(result)
        finally:
            if trust:
                CoreFoundation.CFRelease(trust)

            if cert_array is not None:
                CoreFoundation.CFRelease(cert_array)

        return trust_result.value

    def handshake(
        self,
        server_hostname,
        verify,
        trust_bundle,
        min_version,
        max_version,
        client_cert,
        client_key,
        client_key_passphrase,
        alpn_protocols,
    ):
        """
        Actually performs the TLS handshake. This is run automatically by
        wrapped socket, and shouldn't be needed in user code.
        """
        # First, we do the initial bits of connection setup. We need to create
        # a context, set its I/O funcs, and set the connection reference.
        self.context = Security.SSLCreateContext(
            None, SecurityConst.kSSLClientSide, SecurityConst.kSSLStreamType
        )
        result = Security.SSLSetIOFuncs(
            self.context, _read_callback_pointer, _write_callback_pointer
        )
        _assert_no_error(result)

        # Here we need to compute the handle to use. We do this by taking the
        # id of self modulo 2**31 - 1. If this is already in the dictionary, we
        # just keep incrementing by one until we find a free space.
        with _connection_ref_lock:
            handle = id(self) % 2147483647
            while handle in _connection_refs:
                handle = (handle + 1) % 2147483647
            _connection_refs[handle] = self

        result = Security.SSLSetConnection(self.context, handle)
        _assert_no_error(result)

        # If we have a server hostname, we should set that too.
        if server_hostname:
            if not isinstance(server_hostname, bytes):
                server_hostname = server_hostname.encode("utf-8")

            result = Security.SSLSetPeerDomainName(
                self.context, server_hostname, len(server_hostname)
            )
            _assert_no_error(result)

        # Setup the ciphers.
        self._set_ciphers()

        # Setup the ALPN protocols.
        self._set_alpn_protocols(alpn_protocols)

        # Set the minimum and maximum TLS versions.
        result = Security.SSLSetProtocolVersionMin(self.context, min_version)
        _assert_no_error(result)

        result = Security.SSLSetProtocolVersionMax(self.context, max_version)
        _assert_no_error(result)

        # If there's a trust DB, we need to use it. We do that by telling
        # SecureTransport to break on server auth. We also do that if we don't
        # want to validate the certs at all: we just won't actually do any
        # authing in that case.
        if not verify or trust_bundle is not None:
            result = Security.SSLSetSessionOption(
                self.context, SecurityConst.kSSLSessionOptionBreakOnServerAuth, True
            )
            _assert_no_error(result)

        # If there's a client cert, we need to use it.
        if client_cert:
            self._keychain, self._keychain_dir = _temporary_keychain()
            self._client_cert_chain = _load_client_cert_chain(
                self._keychain, client_cert, client_key
            )
            result = Security.SSLSetCertificate(self.context, self._client_cert_chain)
            _assert_no_error(result)

        while True:
            with self._raise_on_error():
                result = Security.SSLHandshake(self.context)

                if result == SecurityConst.errSSLWouldBlock:
                    raise socket.timeout("handshake timed out")
                elif result == SecurityConst.errSSLServerAuthCompleted:
                    self._custom_validate(verify, trust_bundle)
                    continue
                else:
                    _assert_no_error(result)
                    break

    def fileno(self):
        return self.socket.fileno()

    # Copy-pasted from Python 3.5 source code
    def _decref_socketios(self):
        if self._makefile_refs > 0:
            self._makefile_refs -= 1
        if self._closed:
            self.close()

    def recv(self, bufsiz):
        buffer = ctypes.create_string_buffer(bufsiz)
        bytes_read = self.recv_into(buffer, bufsiz)
        data = buffer[:bytes_read]
        return data

    def recv_into(self, buffer, nbytes=None):
        # Read short on EOF.
        if self._closed:
            return 0

        if nbytes is None:
            nbytes = len(buffer)

        buffer = (ctypes.c_char * nbytes).from_buffer(buffer)
        processed_bytes = ctypes.c_size_t(0)

        with self._raise_on_error():
            result = Security.SSLRead(
                self.context, buffer, nbytes, ctypes.byref(processed_bytes)
            )

        # There are some result codes that we want to treat as "not always
        # errors". Specifically, those are errSSLWouldBlock,
        # errSSLClosedGraceful, and errSSLClosedNoNotify.
        if result == SecurityConst.errSSLWouldBlock:
            # If we didn't process any bytes, then this was just a time out.
            # However, we can get errSSLWouldBlock in situations when we *did*
            # read some data, and in those cases we should just read "short"
            # and return.
            if processed_bytes.value == 0:
                # Timed out, no data read.
                raise socket.timeout("recv timed out")
        elif result in (
            SecurityConst.errSSLClosedGraceful,
            SecurityConst.errSSLClosedNoNotify,
        ):
            # The remote peer has closed this connection. We should do so as
            # well. Note that we don't actually return here because in
            # principle this could actually be fired along with return data.
            # It's unlikely though.
            self.close()
        else:
            _assert_no_error(result)

        # Ok, we read and probably succeeded. We should return whatever data
        # was actually read.
        return processed_bytes.value

    def settimeout(self, timeout):
        self._timeout = timeout

    def gettimeout(self):
        return self._timeout

    def send(self, data):
        processed_bytes = ctypes.c_size_t(0)

        with self._raise_on_error():
            result = Security.SSLWrite(
                self.context, data, len(data), ctypes.byref(processed_bytes)
            )

        if result == SecurityConst.errSSLWouldBlock and processed_bytes.value == 0:
            # Timed out
            raise socket.timeout("send timed out")
        else:
            _assert_no_error(result)

        # We sent, and probably succeeded. Tell them how much we sent.
        return processed_bytes.value

    def sendall(self, data):
        total_sent = 0
        while total_sent < len(data):
            sent = self.send(data[total_sent : total_sent + SSL_WRITE_BLOCKSIZE])
            total_sent += sent

    def shutdown(self):
        with self._raise_on_error():
            Security.SSLClose(self.context)

    def close(self):
        # TODO: should I do clean shutdown here? Do I have to?
        if self._makefile_refs < 1:
            self._closed = True
            if self.context:
                CoreFoundation.CFRelease(self.context)
                self.context = None
            if self._client_cert_chain:
                CoreFoundation.CFRelease(self._client_cert_chain)
                self._client_cert_chain = None
            if self._keychain:
                Security.SecKeychainDelete(self._keychain)
                CoreFoundation.CFRelease(self._keychain)
                shutil.rmtree(self._keychain_dir)
                self._keychain = self._keychain_dir = None
            return self.socket.close()
        else:
            self._makefile_refs -= 1

    def getpeercert(self, binary_form=False):
        # Urgh, annoying.
        #
        # Here's how we do this:
        #
        # 1. Call SSLCopyPeerTrust to get hold of the trust object for this
        #    connection.
        # 2. Call SecTrustGetCertificateAtIndex for index 0 to get the leaf.
        # 3. To get the CN, call SecCertificateCopyCommonName and process that
        #    string so that it's of the appropriate type.
        # 4. To get the SAN, we need to do something a bit more complex:
        #    a. Call SecCertificateCopyValues to get the data, requesting
        #       kSecOIDSubjectAltName.
        #    b. Mess about with this dictionary to try to get the SANs out.
        #
        # This is gross. Really gross. It's going to be a few hundred LoC extra
        # just to repeat something that SecureTransport can *already do*. So my
        # operating assumption at this time is that what we want to do is
        # instead to just flag to urllib3 that it shouldn't do its own hostname
        # validation when using SecureTransport.
        if not binary_form:
            raise ValueError("SecureTransport only supports dumping binary certs")
        trust = Security.SecTrustRef()
        certdata = None
        der_bytes = None

        try:
            # Grab the trust store.
            result = Security.SSLCopyPeerTrust(self.context, ctypes.byref(trust))
            _assert_no_error(result)
            if not trust:
                # Probably we haven't done the handshake yet. No biggie.
                return None

            cert_count = Security.SecTrustGetCertificateCount(trust)
            if not cert_count:
                # Also a case that might happen if we haven't handshaked.
                # Handshook? Handshaken?
                return None

            leaf = Security.SecTrustGetCertificateAtIndex(trust, 0)
            assert leaf

            # Ok, now we want the DER bytes.
            certdata = Security.SecCertificateCopyData(leaf)
            assert certdata

            data_length = CoreFoundation.CFDataGetLength(certdata)
            data_buffer = CoreFoundation.CFDataGetBytePtr(certdata)
            der_bytes = ctypes.string_at(data_buffer, data_length)
        finally:
            if certdata:
                CoreFoundation.CFRelease(certdata)
            if trust:
                CoreFoundation.CFRelease(trust)

        return der_bytes

    def version(self):
        protocol = Security.SSLProtocol()
        result = Security.SSLGetNegotiatedProtocolVersion(
            self.context, ctypes.byref(protocol)
        )
        _assert_no_error(result)
        if protocol.value == SecurityConst.kTLSProtocol13:
            raise ssl.SSLError("SecureTransport does not support TLS 1.3")
        elif protocol.value == SecurityConst.kTLSProtocol12:
            return "TLSv1.2"
        elif protocol.value == SecurityConst.kTLSProtocol11:
            return "TLSv1.1"
        elif protocol.value == SecurityConst.kTLSProtocol1:
            return "TLSv1"
        elif protocol.value == SecurityConst.kSSLProtocol3:
            return "SSLv3"
        elif protocol.value == SecurityConst.kSSLProtocol2:
            return "SSLv2"
        else:
            raise ssl.SSLError("Unknown TLS version: %r" % protocol)

    def _reuse(self):
        self._makefile_refs += 1

    def _drop(self):
        if self._makefile_refs < 1:
            self.close()
        else:
            self._makefile_refs -= 1


if _fileobject:  # Platform-specific: Python 2

    def makefile(self, mode, bufsize=-1):
        self._makefile_refs += 1
        return _fileobject(self, mode, bufsize, close=True)

else:  # Platform-specific: Python 3

    def makefile(self, mode="r", buffering=None, *args, **kwargs):
        # We disable buffering with SecureTransport because it conflicts with
        # the buffering that ST does internally (see issue #1153 for more).
        buffering = 0
        return backport_makefile(self, mode, buffering, *args, **kwargs)


WrappedSocket.makefile = makefile


class SecureTransportContext(object):
    """
    I am a wrapper class for the SecureTransport library, to translate the
    interface of the standard library ``SSLContext`` object to calls into
    SecureTransport.
    """

    def __init__(self, protocol):
        self._min_version, self._max_version = _protocol_to_min_max[protocol]
        self._options = 0
        self._verify = False
        self._trust_bundle = None
        self._client_cert = None
        self._client_key = None
        self._client_key_passphrase = None
        self._alpn_protocols = None

    @property
    def check_hostname(self):
        """
        SecureTransport cannot have its hostname checking disabled. For more,
        see the comment on getpeercert() in this file.
        """
        return True

    @check_hostname.setter
    def check_hostname(self, value):
        """
        SecureTransport cannot have its hostname checking disabled. For more,
        see the comment on getpeercert() in this file.
        """
        pass

    @property
    def options(self):
        # TODO: Well, crap.
        #
        # So this is the bit of the code that is the most likely to cause us
        # trouble. Essentially we need to enumerate all of the SSL options that
        # users might want to use and try to see if we can sensibly translate
        # them, or whether we should just ignore them.
        return self._options

    @options.setter
    def options(self, value):
        # TODO: Update in line with above.
        self._options = value

    @property
    def verify_mode(self):
        return ssl.CERT_REQUIRED if self._verify else ssl.CERT_NONE

    @verify_mode.setter
    def verify_mode(self, value):
        self._verify = True if value == ssl.CERT_REQUIRED else False

    def set_default_verify_paths(self):
        # So, this has to do something a bit weird. Specifically, what it does
        # is nothing.
        #
        # This means that, if we had previously had load_verify_locations
        # called, this does not undo that. We need to do that because it turns
        # out that the rest of the urllib3 code will attempt to load the
        # default verify paths if it hasn't been told about any paths, even if
        # the context itself was sometime earlier. We resolve that by just
        # ignoring it.
        pass

    def load_default_certs(self):
        return self.set_default_verify_paths()

    def set_ciphers(self, ciphers):
        # For now, we just require the default cipher string.
        if ciphers != util.ssl_.DEFAULT_CIPHERS:
            raise ValueError("SecureTransport doesn't support custom cipher strings")

    def load_verify_locations(self, cafile=None, capath=None, cadata=None):
        # OK, we only really support cadata and cafile.
        if capath is not None:
            raise ValueError("SecureTransport does not support cert directories")

        # Raise if cafile does not exist.
        if cafile is not None:
            with open(cafile):
                pass

        self._trust_bundle = cafile or cadata

    def load_cert_chain(self, certfile, keyfile=None, password=None):
        self._client_cert = certfile
        self._client_key = keyfile
        self._client_cert_passphrase = password

    def set_alpn_protocols(self, protocols):
        """
        Sets the ALPN protocols that will later be set on the context.

        Raises a NotImplementedError if ALPN is not supported.
        """
        if not hasattr(Security, "SSLSetALPNProtocols"):
            raise NotImplementedError(
                "SecureTransport supports ALPN only in macOS 10.12+"
            )
        self._alpn_protocols = [six.ensure_binary(p) for p in protocols]

    def wrap_socket(
        self,
        sock,
        server_side=False,
        do_handshake_on_connect=True,
        suppress_ragged_eofs=True,
        server_hostname=None,
    ):
        # So, what do we do here? Firstly, we assert some properties. This is a
        # stripped down shim, so there is some functionality we don't support.
        # See PEP 543 for the real deal.
        assert not server_side
        assert do_handshake_on_connect
        assert suppress_ragged_eofs

        # Ok, we're good to go. Now we want to create the wrapped socket object
        # and store it in the appropriate place.
        wrapped_socket = WrappedSocket(sock)

        # Now we can handshake
        wrapped_socket.handshake(
            server_hostname,
            self._verify,
            self._trust_bundle,
            self._min_version,
            self._max_version,
            self._client_cert,
            self._client_key,
            self._client_key_passphrase,
            self._alpn_protocols,
        )
        return wrapped_socket

# -*- coding: utf-8 -*-
"""
backports.makefile
~~~~~~~~~~~~~~~~~~

Backports the Python 3 ``socket.makefile`` method for use with anything that
wants to create a "fake" socket object.
"""
import io
from socket import SocketIO


def backport_makefile(
    self, mode="r", buffering=None, encoding=None, errors=None, newline=None
):
    """
    Backport of ``socket.makefile`` from Python 3.5.
    """
    if not set(mode) <= {"r", "w", "b"}:
        raise ValueError("invalid mode %r (only r, w, b allowed)" % (mode,))
    writing = "w" in mode
    reading = "r" in mode or not writing
    assert reading or writing
    binary = "b" in mode
    rawmode = ""
    if reading:
        rawmode += "r"
    if writing:
        rawmode += "w"
    raw = SocketIO(self, rawmode)
    self._makefile_refs += 1
    if buffering is None:
        buffering = -1
    if buffering < 0:
        buffering = io.DEFAULT_BUFFER_SIZE
    if buffering == 0:
        if not binary:
            raise ValueError("unbuffered streams must be binary")
        return raw
    if reading and writing:
        buffer = io.BufferedRWPair(raw, raw, buffering)
    elif reading:
        buffer = io.BufferedReader(raw, buffering)
    else:
        assert writing
        buffer = io.BufferedWriter(raw, buffering)
    if binary:
        return buffer
    text = io.TextIOWrapper(buffer, encoding, errors, newline)
    text.mode = mode
    return text