# Copyright 2017 Alethea Katherine Flowers
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import argparse
import collections.abc
import itertools
from collections import OrderedDict
from typing import Any, Iterable, Iterator, List, Mapping, Sequence, Set, Tuple, Union

from nox._decorators import Call, Func
from nox.sessions import Session, SessionRunner

WARN_PYTHONS_IGNORED = "python_ignored"


def _unique_list(*args: str) -> List[str]:
    """Return a list without duplicates, while preserving order."""
    return list(OrderedDict.fromkeys(args))


class Manifest:
    """Session manifest.

    The session manifest provides the source of truth for the sequence of
    sessions that should be run by nox.

    It is possible for this to be mutated during execution. This allows for
    useful use cases, such as for one session to "notify" another or
    "chain" to another.

    Args:
        session_functions (Mapping[str, function]): The registry of discovered
            session functions.
        global_config (.nox.main.GlobalConfig): The global configuration.
    """

    def __init__(
        self, session_functions: Mapping[str, "Func"], global_config: argparse.Namespace
    ) -> None:
        self._all_sessions = []  # type: List[SessionRunner]
        self._queue = []  # type: List[SessionRunner]
        self._consumed = []  # type: List[SessionRunner]
        self._config = global_config  # type: argparse.Namespace

        # Create the sessions based on the provided session functions.
        for name, func in session_functions.items():
            for session in self.make_session(name, func):
                self.add_session(session)

    def __contains__(self, needle: Union[str, SessionRunner]) -> bool:
        if needle in self._queue or needle in self._consumed:
            return True
        for session in self._queue + self._consumed:
            if session.name == needle or needle in session.signatures:
                return True
        return False

    def __iter__(self) -> "Manifest":
        return self

    def __getitem__(self, key: str) -> SessionRunner:
        for session in self._queue + self._consumed:
            if session.name == key or key in session.signatures:
                return session
        raise KeyError(key)

    def __next__(self) -> SessionRunner:
        """Return the next item in the queue.

        Raises:
            StopIteration: If the queue has been entirely consumed.
        """
        if not len(self._queue):
            raise StopIteration
        session = self._queue.pop(0)
        self._consumed.append(session)
        return session

    def __len__(self) -> int:
        return len(self._queue) + len(self._consumed)

    def list_all_sessions(self) -> Iterator[Tuple[SessionRunner, bool]]:
        """Yields all sessions and whether or not they're selected."""
        for session in self._all_sessions:
            yield session, session in self._queue

    def add_session(self, session: SessionRunner) -> None:
        """Add the given session to the manifest.

        Args:
            session (~nox.sessions.Session): A session object, such as
                one returned from ``make_session``.
        """
        if session not in self._all_sessions:
            self._all_sessions.append(session)
        if session not in self._queue:
            self._queue.append(session)

    def filter_by_name(self, specified_sessions: Iterable[str]) -> None:
        """Filter sessions in the queue based on the user-specified names.

        Args:
            specified_sessions (Sequence[str]): A list of specified
                session names.

        Raises:
            KeyError: If any explicitly listed sessions are not found.
        """
        # Filter the sessions remaining in the queue based on
        # whether they are individually specified.
        queue = []
        for session_name in specified_sessions:
            for session in self._queue:
                if session_name == session.name or session_name in set(
                    session.signatures
                ):
                    queue.append(session)

        self._queue = queue

        # If a session was requested and was not found, complain loudly.
        all_sessions = set(
            itertools.chain(
                [x.name for x in self._all_sessions if x.name],
                *[x.signatures for x in self._all_sessions],
            )
        )
        missing_sessions = set(specified_sessions) - all_sessions
        if missing_sessions:
            raise KeyError("Sessions not found: {}".format(", ".join(missing_sessions)))

    def filter_by_python_interpreter(self, specified_pythons: Sequence[str]) -> None:
        """Filter sessions in the queue based on the user-specified
        python interpreter versions.

        Args:
            specified_pythons (Sequence[str]): A list of specified
                python interpreter versions.
        """
        self._queue = [x for x in self._queue if x.func.python in specified_pythons]

    def filter_by_keywords(self, keywords: str) -> None:
        """Filter sessions using pytest-like keyword expressions.

        Args:
            keywords (str): A Python expression of keywords which
                session names are checked against.
        """
        self._queue = [
            x for x in self._queue if keyword_match(keywords, x.signatures + [x.name])
        ]

    def make_session(
        self, name: str, func: "Func", multi: bool = False
    ) -> List[SessionRunner]:
        """Create a session object from the session function.

        Args:
            name (str): The name of the session.
            func (function): The session function.
            multi (bool): Whether the function is a member of a set of sessions
                with different interpreters.

        Returns:
            Sequence[~nox.session.Session]: A sequence of Session objects
                bound to this manifest and configuration.
        """
        sessions = []

        # if backend is none we wont parametrize the pythons
        backend = (
            self._config.force_venv_backend
            or func.venv_backend
            or self._config.default_venv_backend
        )
        if backend == "none" and isinstance(func.python, (list, tuple, set)):
            # we can not log a warning here since the session is maybe deselected.
            # instead let's set a flag, to warn later when session is actually run.
            func.should_warn[WARN_PYTHONS_IGNORED] = func.python
            func.python = False

        if self._config.extra_pythons:
            # If extra python is provided, expand the func.python list to
            # include additional python interpreters
            extra_pythons = self._config.extra_pythons  # type: List[str]
            if isinstance(func.python, (list, tuple, set)):
                func.python = _unique_list(*func.python, *extra_pythons)
            elif not multi and func.python:
                # If this is multi, but there is only a single interpreter, it
                # is the reentrant case. The extra_python interpreter shouldn't
                # be added in that case. If func.python is False, the session
                # has no backend; if None, it uses the same interpreter as Nox.
                # Otherwise, add the extra specified python.
                assert isinstance(func.python, str)
                func.python = _unique_list(func.python, *extra_pythons)

        # If the func has the python attribute set to a list, we'll need
        # to expand them.
        if isinstance(func.python, (list, tuple, set)):

            for python in func.python:
                single_func = func.copy()
                single_func.python = python
                sessions.extend(self.make_session(name, single_func, multi=True))

            return sessions

        # Simple case: If this function is not parametrized, then make
        # a simple session
        if not hasattr(func, "parametrize"):
            long_names = []
            if not multi:
                long_names.append(name)
            if func.python:
                long_names.append("{}-{}".format(name, func.python))

            return [SessionRunner(name, long_names, func, self._config, self)]

        # Since this function is parametrized, we need to add a distinct
        # session for each permutation.
        parametrize = func.parametrize  # type: ignore
        calls = Call.generate_calls(func, parametrize)
        for call in calls:
            long_names = []
            if not multi:
                long_names.append("{}{}".format(name, call.session_signature))
            if func.python:
                long_names.append(
                    "{}-{}{}".format(name, func.python, call.session_signature)
                )
                # Ensure that specifying session-python will run all parameterizations.
                long_names.append("{}-{}".format(name, func.python))

            sessions.append(SessionRunner(name, long_names, call, self._config, self))

        # Edge case: If the parameters made it such that there were no valid
        # calls, add an empty, do-nothing session.
        if not calls:
            sessions.append(
                SessionRunner(name, [], _null_session_func, self._config, self)
            )

        # Return the list of sessions.
        return sessions

    def next(self) -> SessionRunner:
        return self.__next__()

    def notify(self, session: Union[str, SessionRunner]) -> bool:
        """Enqueue the specified session in the queue.

        If the session is already in the queue, or has been run already,
        then this is a no-op.

        Args:
            session (Union[str, ~nox.session.Session]): The session to be
                enqueued.

        Returns:
            bool: Whether the session was added to the queue.

        Raises:
            ValueError: If the session was not found.
        """
        # Sanity check: If this session is already in the queue, this is
        # a no-op.
        if session in self:
            return False

        # Locate the session in the list of all sessions, and place it at
        # the end of the queue.
        for s in self._all_sessions:
            if s == session or s.name == session or session in s.signatures:
                self._queue.append(s)
                return True

        # The session was not found in the list of sessions.
        raise ValueError("Session {} not found.".format(session))


class KeywordLocals(collections.abc.Mapping):
    """Eval locals using keywords.

    When looking up a local variable the variable name is compared against
    the set of keywords. If the local variable name matches any *substring* of
    any keyword, then the name lookup returns True. Otherwise, the name lookup
    returns False.
    """

    def __init__(self, keywords: Set[str]) -> None:
        self._keywords = keywords

    def __getitem__(self, variable_name: str) -> bool:
        for keyword in self._keywords:
            if variable_name in keyword:
                return True
        return False

    def __iter__(self) -> Iterator[str]:
        return iter(self._keywords)

    def __len__(self) -> int:
        return len(self._keywords)


def keyword_match(expression: str, keywords: Iterable[str]) -> Any:
    """See if an expression matches the given set of keywords."""
    locals = KeywordLocals(set(keywords))
    return eval(expression, {}, locals)


def _null_session_func_(session: Session) -> None:
    """A no-op session for patemetrized sessions with no available params."""
    session.skip("This session had no parameters available.")


_null_session_func = Func(_null_session_func_, python=False)
