from functools import partial
import os
from os import lstat
from importlib import import_module

from pkg_resources import parse_version

from conda import __version__ as CONDA_VERSION


def try_exports(module, attr):
    # this assumes conda.exports exists, so only use for conda 4.3 onward
    try:
        return getattr(import_module('conda.exports'), attr)
    except AttributeError:
        return getattr(import_module(module), attr)


try:
    # This monkey patch is addressed at #1825. The ensure_use_local is an outdated vestige
    #   and no longer has any relevant effect.
    import conda.cli.common
    conda.cli.common.ensure_use_local = lambda x: None
except ImportError:
    # no need to patch if it doesn't exist
    pass

conda_43 = parse_version(CONDA_VERSION) >= parse_version("4.3.0a0")
conda_44 = parse_version(CONDA_VERSION) >= parse_version("4.4.0a0")
conda_45 = parse_version(CONDA_VERSION) >= parse_version("4.5.0a0")
conda_46 = parse_version(CONDA_VERSION) >= parse_version("4.6.0a0")
conda_47 = parse_version(CONDA_VERSION) >= parse_version("4.7.0a0")
conda_48 = parse_version(CONDA_VERSION) >= parse_version("4.8.0a0")
conda_411 = parse_version(CONDA_VERSION) >= parse_version("4.11.0a0")

if conda_44:
    from conda.exports import display_actions, execute_actions, execute_plan, install_actions
else:
    from conda.plan import display_actions, execute_actions, execute_plan, install_actions

display_actions, execute_actions, execute_plan = display_actions, execute_actions, execute_plan
install_actions = install_actions

try:
    # Conda 4.4+
    from conda.exports import _toposort
except ImportError:
    from conda.toposort import _toposort
_toposort = _toposort

if conda_411:
    from conda.auxlib.packaging import _get_version_from_git_tag
else:
    from conda._vendor.auxlib.packaging import _get_version_from_git_tag
get_version_from_git_tag = _get_version_from_git_tag

from conda.exports import TmpDownload, download, handle_proxy_407  # NOQA
from conda.exports import untracked, walk_prefix  # NOQA
from conda.exports import MatchSpec, NoPackagesFound, Resolve, Unsatisfiable, normalized_version  # NOQA
from conda.exports import human_bytes, hashsum_file, md5_file, memoized, unix_path_to_win, win_path_to_unix, url_path  # NOQA
from conda.exports import get_index  # NOQA
from conda.exports import (Completer, InstalledPackages, add_parser_channels,  # NOQA
                           add_parser_prefix,  # NOQA
                           specs_from_args, spec_from_line, specs_from_url)  # NOQA
from conda.exports import ArgumentParser  # NOQA
from conda.exports import (is_linked, linked, linked_data, prefix_placeholder,  # NOQA
                           rm_rf, symlink_conda, package_cache)  # NOQA
from conda.exports import CondaSession  # NOQA
from conda.exports import (PY3,  StringIO, input, iteritems, lchmod, string_types,  # NOQA
                          text_type, TemporaryDirectory)  # NOQA
from conda.exports import VersionOrder  # NOQA


TmpDownload = TmpDownload
download, handle_proxy_407, untracked, walk_prefix = download, handle_proxy_407, untracked, walk_prefix  # NOQA
MatchSpec, Resolve, normalized_version = MatchSpec, Resolve, normalized_version
human_bytes, hashsum_file, md5_file, memoized = human_bytes, hashsum_file, md5_file, memoized
unix_path_to_win, win_path_to_unix, url_path = unix_path_to_win, win_path_to_unix, url_path
get_index, Completer, InstalledPackages = get_index, Completer, InstalledPackages
add_parser_channels, add_parser_prefix = add_parser_channels, add_parser_prefix
specs_from_args, spec_from_line, specs_from_url = specs_from_args, spec_from_line, specs_from_url
is_linked, linked, linked_data, prefix_placeholder = is_linked, linked, linked_data, prefix_placeholder # NOQA
rm_rf, symlink_conda, package_cache = rm_rf, symlink_conda, package_cache
PY3, input, iteritems, lchmod, string_types = PY3, input, iteritems, lchmod, string_types
text_type, TemporaryDirectory = text_type, TemporaryDirectory
ArgumentParser, CondaSession, VersionOrder = ArgumentParser, CondaSession, VersionOrder


from conda.core.package_cache import ProgressiveFetchExtract  # NOQA
from conda.models.dist import Dist, IndexRecord  # NOQA

ProgressiveFetchExtract = ProgressiveFetchExtract
Dist, IndexRecord = Dist, IndexRecord

if PY3:
    import configparser  # NOQA
else:
    import ConfigParser as configparser  # NOQA
configparser = configparser


from conda.exports import FileMode, PathType  # NOQA
FileMode, PathType = FileMode, PathType
from conda.exports import EntityEncoder  # NOQA

EntityEncoder, FileMode, PathType = EntityEncoder, FileMode, PathType


CondaError = try_exports("conda.exceptions", "CondaError")
CondaHTTPError = try_exports("conda.exceptions", "CondaHTTPError")
LinkError = try_exports("conda.exceptions", "LinkError")
LockError = try_exports("conda.exceptions", "LockError")
NoPackagesFoundError = try_exports("conda.exceptions", "NoPackagesFoundError")
PaddingError = try_exports("conda.exceptions", "PaddingError")
UnsatisfiableError = try_exports("conda.exceptions", "UnsatisfiableError")

non_x86_linux_machines = try_exports("conda.base.context", "non_x86_linux_machines")
context = try_exports("conda.base.context", "context")
context_get_prefix = try_exports("conda.base.context", "get_prefix")
reset_context = try_exports("conda.base.context", "reset_context")
get_conda_build_local_url = try_exports("conda.models.channel", "get_conda_build_local_url")

binstar_upload = context.binstar_upload
bits = context.bits
conda_private = context.conda_private
default_python = context.default_python
envs_dirs = context.envs_dirs
pkgs_dirs = list(context.pkgs_dirs)
cc_platform = context.platform
root_dir = context.root_dir
root_writable = context.root_writable
subdir = context.subdir
create_default_packages = context.create_default_packages

get_rc_urls = lambda: list(context.channels)
get_prefix = partial(context_get_prefix, context)
cc_conda_build = context.conda_build if hasattr(context, 'conda_build') else {}

try:
    from conda.exports import Channel
except:
    from conda.models.channel import Channel
get_conda_channel = Channel.from_value

# disallow softlinks.  This avoids a lot of dumb issues, at the potential cost of disk space.
os.environ['CONDA_ALLOW_SOFTLINKS'] = 'false'
reset_context()

get_local_urls = lambda: list(get_conda_build_local_url()) or []
arch_name = context.arch_name


CondaError, CondaHTTPError, get_prefix, LinkError = CondaError, CondaHTTPError, get_prefix, LinkError  # NOQA
LockError, non_x86_linux_machines, NoPackagesFoundError = LockError, non_x86_linux_machines, NoPackagesFoundError  # NOQA
PaddingError, UnsatisfiableError = PaddingError, UnsatisfiableError


# work-around for python bug on Windows prior to python 3.2
# https://bugs.python.org/issue10027
# Adapted from the ntfsutils package, Copyright (c) 2012, the Mozilla Foundation
class CrossPlatformStLink:
    _st_nlink = None

    def __call__(self, path):
        return self.st_nlink(path)

    @classmethod
    def st_nlink(cls, path):
        if cls._st_nlink is None:
            cls._initialize()
        return cls._st_nlink(path)

    @classmethod
    def _standard_st_nlink(cls, path):
        return lstat(path).st_nlink

    @classmethod
    def _windows_st_nlink(cls, path):
        st_nlink = cls._standard_st_nlink(path)
        if st_nlink != 0:
            return st_nlink
        else:
            # cannot trust python on Windows when st_nlink == 0
            # get value using windows libraries to be sure of its true value
            # Adapted from the ntfsutils package, Copyright (c) 2012, the Mozilla Foundation
            GENERIC_READ = 0x80000000
            FILE_SHARE_READ = 0x00000001
            OPEN_EXISTING = 3
            hfile = cls.CreateFile(path, GENERIC_READ, FILE_SHARE_READ, None,
                                   OPEN_EXISTING, 0, None)
            if hfile is None:
                from ctypes import WinError
                raise WinError(
                    "Could not determine determine number of hardlinks for %s" % path)
            info = cls.BY_HANDLE_FILE_INFORMATION()
            rv = cls.GetFileInformationByHandle(hfile, info)
            cls.CloseHandle(hfile)
            if rv == 0:
                from ctypes import WinError
                raise WinError("Could not determine file information for %s" % path)
            return info.nNumberOfLinks

    @classmethod
    def _initialize(cls):
        if os.name != 'nt':
            cls._st_nlink = cls._standard_st_nlink
        else:
            # http://msdn.microsoft.com/en-us/library/windows/desktop/aa363858
            import ctypes
            from ctypes import POINTER
            from ctypes.wintypes import DWORD, HANDLE, BOOL

            cls.CreateFile = ctypes.windll.kernel32.CreateFileW
            cls.CreateFile.argtypes = [ctypes.c_wchar_p, DWORD, DWORD, ctypes.c_void_p,
                                       DWORD, DWORD, HANDLE]
            cls.CreateFile.restype = HANDLE

            # http://msdn.microsoft.com/en-us/library/windows/desktop/ms724211
            cls.CloseHandle = ctypes.windll.kernel32.CloseHandle
            cls.CloseHandle.argtypes = [HANDLE]
            cls.CloseHandle.restype = BOOL

            class FILETIME(ctypes.Structure):
                _fields_ = [("dwLowDateTime", DWORD),
                            ("dwHighDateTime", DWORD)]

            class BY_HANDLE_FILE_INFORMATION(ctypes.Structure):
                _fields_ = [("dwFileAttributes", DWORD),
                            ("ftCreationTime", FILETIME),
                            ("ftLastAccessTime", FILETIME),
                            ("ftLastWriteTime", FILETIME),
                            ("dwVolumeSerialNumber", DWORD),
                            ("nFileSizeHigh", DWORD),
                            ("nFileSizeLow", DWORD),
                            ("nNumberOfLinks", DWORD),
                            ("nFileIndexHigh", DWORD),
                            ("nFileIndexLow", DWORD)]

            cls.BY_HANDLE_FILE_INFORMATION = BY_HANDLE_FILE_INFORMATION

            # http://msdn.microsoft.com/en-us/library/windows/desktop/aa364952
            cls.GetFileInformationByHandle = ctypes.windll.kernel32.GetFileInformationByHandle
            cls.GetFileInformationByHandle.argtypes = [HANDLE,
                                                       POINTER(BY_HANDLE_FILE_INFORMATION)]
            cls.GetFileInformationByHandle.restype = BOOL

            cls._st_nlink = cls._windows_st_nlink


class SignatureError(Exception):
    pass


def which_package(path):
    """
    given the path (of a (presumably) conda installed file) iterate over
    the conda packages the file came from.  Usually the iteration yields
    only one package.
    """
    from os.path import abspath, join
    path = abspath(path)
    prefix = which_prefix(path)
    if prefix is None:
        raise RuntimeError("could not determine conda prefix from: %s" % path)
    for dist in linked(prefix):
        meta = is_linked(prefix, dist)
        if any(abspath(join(prefix, f)) == path for f in meta['files']):
            yield dist


def which_prefix(path):
    """
    given the path (to a (presumably) conda installed file) return the
    environment prefix in which the file in located
    """
    from os.path import abspath, join, isdir, dirname
    prefix = abspath(path)
    iteration = 0
    while iteration < 20:
        if isdir(join(prefix, 'conda-meta')):
            # we found the it, so let's return it
            break
        if prefix == dirname(prefix):
            # we cannot chop off any more directories, so we didn't find it
            prefix = None
            break
        prefix = dirname(prefix)
        iteration += 1
    return prefix


def get_installed_version(prefix, pkgs):
    """Primarily used by conda-forge, but may be useful in general for checking when a package
    needs to be updated"""
    from conda_build.utils import ensure_list
    pkgs = ensure_list(pkgs)
    linked_pkgs = linked(prefix)
    versions = {}
    for pkg in pkgs:
        vers_inst = [dist.split('::', 1)[-1].rsplit('-', 2)[1] for dist in linked_pkgs
            if dist.split('::', 1)[-1].rsplit('-', 2)[0] == pkg]
        versions[pkg] = vers_inst[0] if len(vers_inst) == 1 else None
    return versions


# when deactivating envs (e.g. switching from root to build/test) this env var is used,
# except the PR that removed this has been reverted (for now) and Windows doesnt need it.
env_path_backup_var_exists = os.environ.get('CONDA_PATH_BACKUP', None)