import os
import platform
import subprocess
import sys
import sysconfig
import warnings

from contextlib import contextmanager
from subprocess import CalledProcessError

from poetry.config import Config
from poetry.locations import CACHE_DIR
from poetry.utils._compat import Path
from poetry.utils._compat import decode


class VenvError(Exception):

    pass


class VenvCommandError(VenvError):

    def __init__(self, e):  # type: (CalledProcessError) -> None
        message = 'Command {} errored with the following output: \n{}'.format(
            e.cmd, e.output.decode()
        )

        super(VenvCommandError, self).__init__(message)


class Venv(object):

    def __init__(self, venv=None):
        self._venv = venv
        if self._venv:
            self._venv = Path(self._venv)

        self._windows = sys.platform == 'win32'

        self._bin_dir = None
        if venv:
            bin_dir = 'bin' if not self._windows else 'Scripts'
            self._bin_dir = self._venv / bin_dir

        self._version_info = None
        self._python_implementation = None

    @classmethod
    def create(cls, io, name=None):  # type: (...) -> Venv
        if 'VIRTUAL_ENV' not in os.environ:
            # Not in a virtualenv
            # Checking if we need to create one
            config = Config.create('config.toml')

            create_venv = config.setting('settings.virtualenvs.create')

            venv_path = config.setting('settings.virtualenvs.path')
            if venv_path is None:
                venv_path = Path(CACHE_DIR) / 'virtualenvs'
            else:
                venv_path = Path(venv_path)

            if not name:
                name = Path.cwd().name

            name = '{}-py{}'.format(
                name, '.'.join([str(v) for v in sys.version_info[:2]])
            )

            venv = venv_path / name
            if not venv.exists():
                if create_venv is False:
                    io.writeln(
                        '<fg=black;bg=yellow>'
                        'Skipping virtualenv creation, '
                        'as specified in config file.'
                        '</>'
                    )

                    return cls()

                io.writeln(
                    'Creating virtualenv <info>{}</> in {}'.format(
                        name, str(venv_path)
                    )
                )

                cls.build(str(venv))
            else:
                if io.is_very_verbose():
                    io.writeln(
                        'Virtualenv <info>{}</> already exists.'.format(name)
                    )

            os.environ['VIRTUAL_ENV'] = str(venv)

        # venv detection:
        # stdlib venv may symlink sys.executable, so we can't use realpath.
        # but others can symlink *to* the venv Python,
        # so we can't just use sys.executable.
        # So we just check every item in the symlink tree (generally <= 3)
        p = os.path.normcase(sys.executable)
        paths = [p]
        while os.path.islink(p):
            p = os.path.normcase(
                os.path.join(os.path.dirname(p), os.readlink(p)))
            paths.append(p)

        p_venv = os.path.normcase(os.environ['VIRTUAL_ENV'])
        if any(p.startswith(p_venv) for p in paths):
            # Running properly in the virtualenv, don't need to do anything
            return cls()

        venv = os.environ['VIRTUAL_ENV']

        return cls(venv)

    @classmethod
    def build(cls, path):
        try:
            from venv import EnvBuilder

            builder = EnvBuilder(with_pip=True)
            build = builder.create
        except ImportError:
            # We fallback on virtualenv for Python 2.7
            from virtualenv import create_environment

            build = create_environment

        build(path)

    @property
    def venv(self):
        return self._venv

    @property
    def python(self):  # type: () -> str
        """
        Path to current python executable
        """
        return self._bin('python')

    @property
    def pip(self):  # type: () -> str
        """
        Path to current pip executable
        """
        return self._bin('pip')

    @property
    def version_info(self):  # type: () -> tuple
        if self._version_info is not None:
            return self._version_info

        if not self.is_venv():
            self._version_info = sys.version_info
        else:
            output = self.run(
                'python', '-c',
                '"import sys; print(\'.\'.join([str(s) for s in sys.version_info[:3]]))"',
                shell=True
            )

            self._version_info = tuple([
                int(s) for s in output.strip().split('.')
            ])

        return self._version_info

    @property
    def python_implementation(self):
        if self._python_implementation is not None:
            return self._python_implementation

        if not self.is_venv():
            impl = platform.python_implementation()
        else:
            impl = self.run(
                'python', '-c',
                '"import platform; print(platform.python_implementation())"',
                shell=True
            ).strip()

        self._python_implementation = impl

        return self._python_implementation

    def config_var(self, var):
        if not self.is_venv():
            try:
                return sysconfig.get_config_var(var)
            except IOError as e:
                warnings.warn("{0}".format(e), RuntimeWarning)
                return None

        try:
            value = self.run(
                'python', '-c',
                '"import sysconfig; '
                'print(sysconfig.get_config_var(\'{}\'))"'.format(var),
                shell=True
            ).strip()
        except VenvCommandError as e:
            warnings.warn("{0}".format(e), RuntimeWarning)
            return None

        if value == 'None':
            value = None
        elif value == '1':
            value = 1
        elif value == '0':
            value = 0

        return value

    def run(self, bin, *args, **kwargs):
        """
        Run a command inside the virtual env.
        """
        cmd = [bin] + list(args)
        shell = kwargs.get('shell', False)
        call = kwargs.pop('call', False)

        if shell:
            cmd = ' '.join(cmd)

        try:
            if not self.is_venv():
                if call:
                    return subprocess.call(
                        cmd, stderr=subprocess.STDOUT,
                        **kwargs
                    )

                output = subprocess.check_output(
                    cmd, stderr=subprocess.STDOUT,
                    **kwargs
                )
            else:
                if self._windows:
                    kwargs['shell'] = True

                with self.temp_environ():
                    os.environ['PATH'] = self._path()
                    os.environ['VIRTUAL_ENV'] = str(self._venv)

                    self.unset_env('PYTHONHOME')
                    self.unset_env('__PYVENV_LAUNCHER__')

                    if call:
                        return subprocess.call(
                            cmd, stderr=subprocess.STDOUT,
                            **kwargs
                        )

                    output = subprocess.check_output(
                        cmd, stderr=subprocess.STDOUT,
                        **kwargs
                    )
        except CalledProcessError as e:
            raise VenvCommandError(e)

        return decode(output)

    def execute(self, bin, *args, **kwargs):
        if not self.is_venv():
            return subprocess.call([bin] + list(args))
        else:
            with self.temp_environ():
                os.environ['PATH'] = self._path()
                os.environ['VIRTUAL_ENV'] = str(self._venv)

                self.unset_env('PYTHONHOME')
                self.unset_env('__PYVENV_LAUNCHER__')

                return subprocess.call([bin] + list(args), **kwargs)

    @contextmanager
    def temp_environ(self):
        environ = dict(os.environ)
        try:
            yield
        finally:
            os.environ.clear()
            os.environ.update(environ)

    def _path(self):
        return os.pathsep.join([
            str(self._bin_dir),
            os.environ['PATH'],
        ])

    def unset_env(self, key):
        if key in os.environ:
            del os.environ[key]

    def get_shell(self):
        shell = Path(os.environ.get('SHELL', '')).stem
        if shell in ('bash', 'zsh', 'fish'):
            return shell

    def _bin(self, bin):  # type: (str) -> str
        """
        Return path to the given executable.
        """
        if not self.is_venv():
            return bin

        return str(self._bin_dir / bin) + ('.exe' if self._windows else '')

    def is_venv(self):  # type: () -> bool
        return self._venv is not None


class NullVenv(Venv):

    def __init__(self, execute=False):
        super(NullVenv, self).__init__()

        self.executed = []
        self._execute = execute

    def run(self, bin, *args):
        self.executed.append([bin] + list(args))

        if self._execute:
            return super(NullVenv, self).run(bin, *args)

    def _bin(self, bin):
        return bin
