# Copyright (c) 2015-2016 Cara Vinson <ceridwenv@gmail.com>
# Copyright (c) 2015-2016 Claudiu Popa <pcmanticore@gmail.com>

# Licensed under the LGPL: https://www.gnu.org/licenses/old-licenses/lgpl-2.1.en.html
# For details: https://github.com/PyCQA/astroid/blob/master/COPYING.LESSER


"""
Various helper utilities.
"""

import builtins as builtins_mod

from astroid import bases
from astroid import context as contextmod
from astroid import exceptions
from astroid import manager
from astroid import nodes
from astroid import raw_building
from astroid import scoped_nodes
from astroid import util


BUILTINS = builtins_mod.__name__


def _build_proxy_class(cls_name, builtins):
    proxy = raw_building.build_class(cls_name)
    proxy.parent = builtins
    return proxy


def _function_type(function, builtins):
    if isinstance(function, scoped_nodes.Lambda):
        if function.root().name == BUILTINS:
            cls_name = 'builtin_function_or_method'
        else:
            cls_name = 'function'
    elif isinstance(function, bases.BoundMethod):
        cls_name = 'method'
    elif isinstance(function, bases.UnboundMethod):
        cls_name = 'function'
    return _build_proxy_class(cls_name, builtins)


def _object_type(node, context=None):
    astroid_manager = manager.AstroidManager()
    builtins = astroid_manager.astroid_cache[BUILTINS]
    context = context or contextmod.InferenceContext()

    for inferred in node.infer(context=context):
        if isinstance(inferred, scoped_nodes.ClassDef):
            if inferred.newstyle:
                metaclass = inferred.metaclass()
                if metaclass:
                    yield metaclass
                    continue
            yield builtins.getattr('type')[0]
        elif isinstance(inferred, (scoped_nodes.Lambda, bases.UnboundMethod)):
            yield _function_type(inferred, builtins)
        elif isinstance(inferred, scoped_nodes.Module):
            yield _build_proxy_class('module', builtins)
        else:
            yield inferred._proxied


def object_type(node, context=None):
    """Obtain the type of the given node

    This is used to implement the ``type`` builtin, which means that it's
    used for inferring type calls, as well as used in a couple of other places
    in the inference.
    The node will be inferred first, so this function can support all
    sorts of objects, as long as they support inference.
    """

    try:
        types = set(_object_type(node, context))
    except exceptions.InferenceError:
        return util.Uninferable
    if len(types) > 1 or not types:
        return util.Uninferable
    return list(types)[0]


def object_isinstance(node, class_or_seq, context=None):
    """Check if a node 'isinstance' any node in class_or_seq

    :param node: A given node
    :param class_or_seq: Union[Nodes.NodeNG], Sequence[nodes.NodeNG]]
    :rtype: bool

    :raises AstroidTypeError: if the given ``classes_or_seq`` are not types
    :raises AstroidError: if the type of the given node cannot be inferred
        or its type's mro doesn't work
    """
    if not isinstance(class_or_seq, (tuple, list)):
        class_seq = (class_or_seq,)
    else:
        class_seq = class_or_seq
    obj_type = object_type(node, context)
    if obj_type is util.Uninferable:
        return util.Uninferable

    # Instances are not types
    class_seq = [item if not isinstance(item, bases.Instance)
                 else util.Uninferable for item in class_seq]
    # strict compatibility with isinstance
    # isinstance(1, (int, 1)) evaluates to true
    # isinstance(1, (1, int)) raises TypeError
    for klass in class_seq:
        if klass is util.Uninferable:
            raise exceptions.AstroidTypeError(
                "isinstance() arg 2 must be a type or tuple of types")
        for obj_subclass in obj_type.mro():
            if obj_subclass == klass:
                return True
    return False


def safe_infer(node, context=None):
    """Return the inferred value for the given node.

    Return None if inference failed or if there is some ambiguity (more than
    one node has been inferred).
    """
    try:
        inferit = node.infer(context=context)
        value = next(inferit)
    except exceptions.InferenceError:
        return None
    try:
        next(inferit)
        return None # None if there is ambiguity on the inferred node
    except exceptions.InferenceError:
        return None# there is some kind of ambiguity
    except StopIteration:
        return value


def has_known_bases(klass, context=None):
    """Return true if all base classes of a class could be inferred."""
    try:
        return klass._all_bases_known
    except AttributeError:
        pass
    for base in klass.bases:
        result = safe_infer(base, context=context)
        # TODO: check for A->B->A->B pattern in class structure too?
        if (not isinstance(result, scoped_nodes.ClassDef) or
                result is klass or
                not has_known_bases(result, context=context)):
            klass._all_bases_known = False
            return False
    klass._all_bases_known = True
    return True


def _type_check(type1, type2):
    if not all(map(has_known_bases, (type1, type2))):
        raise exceptions._NonDeducibleTypeHierarchy

    if not all([type1.newstyle, type2.newstyle]):
        return False
    try:
        return type1 in type2.mro()[:-1]
    except exceptions.MroError:
        # The MRO is invalid.
        raise exceptions._NonDeducibleTypeHierarchy


def is_subtype(type1, type2):
    """Check if *type1* is a subtype of *typ2*."""
    return _type_check(type2, type1)


def is_supertype(type1, type2):
    """Check if *type2* is a supertype of *type1*."""
    return _type_check(type1, type2)


def class_instance_as_index(node):
    """Get the value as an index for the given instance.

    If an instance provides an __index__ method, then it can
    be used in some scenarios where an integer is expected,
    for instance when multiplying or subscripting a list.
    """
    context = contextmod.InferenceContext()
    context.callcontext = contextmod.CallContext(args=[node])

    try:
        for inferred in node.igetattr('__index__', context=context):
            if not isinstance(inferred, bases.BoundMethod):
                continue

            for result in inferred.infer_call_result(node, context=context):
                if (isinstance(result, nodes.Const)
                        and isinstance(result.value, int)):
                    return result
    except exceptions.InferenceError:
        pass
    return None