from collections import OrderedDict
from typing import Any, Dict, List, Optional, Set, TYPE_CHECKING, Union, cast

from mypy import checker
from mypy.checker import TypeChecker
from mypy.mro import calculate_mro
from mypy.nodes import (Block, ClassDef, Expression, GDEF, MDEF, MemberExpr, MypyFile, NameExpr, StrExpr, SymbolNode,
                        SymbolTable, SymbolTableNode, TypeInfo, Var)
from mypy.plugin import AttributeContext, CheckerPluginInterface, FunctionContext, MethodContext
from mypy.types import AnyType, Instance, NoneTyp, TupleType, Type as MypyType, TypeOfAny, TypedDictType, UnionType

if TYPE_CHECKING:
    from mypy_django_plugin.django.context import DjangoContext


def get_django_metadata(model_info: TypeInfo) -> Dict[str, Any]:
    return model_info.metadata.setdefault('django', {})


class IncompleteDefnException(Exception):
    pass


def lookup_fully_qualified_sym(fullname: str, all_modules: Dict[str, MypyFile]) -> Optional[SymbolTableNode]:
    if '.' not in fullname:
        return None
    module, cls_name = fullname.rsplit('.', 1)

    module_file = all_modules.get(module)
    if module_file is None:
        return None
    sym = module_file.names.get(cls_name)
    if sym is None:
        return None
    return sym


def lookup_fully_qualified_generic(name: str, all_modules: Dict[str, MypyFile]) -> Optional[SymbolNode]:
    sym = lookup_fully_qualified_sym(name, all_modules)
    if sym is None:
        return None
    return sym.node


def lookup_fully_qualified_typeinfo(api: TypeChecker, fullname: str) -> Optional[TypeInfo]:
    node = lookup_fully_qualified_generic(fullname, api.modules)
    if not isinstance(node, TypeInfo):
        return None
    return node


def lookup_class_typeinfo(api: TypeChecker, klass: type) -> Optional[TypeInfo]:
    fullname = get_class_fullname(klass)
    field_info = lookup_fully_qualified_typeinfo(api, fullname)
    return field_info


def reparametrize_instance(instance: Instance, new_args: List[MypyType]) -> Instance:
    return Instance(instance.type, args=new_args,
                    line=instance.line, column=instance.column)


def get_class_fullname(klass: type) -> str:
    return klass.__module__ + '.' + klass.__qualname__


def get_call_argument_by_name(ctx: Union[FunctionContext, MethodContext], name: str) -> Optional[Expression]:
    """
    Return the expression for the specific argument.
    This helper should only be used with non-star arguments.
    """
    if name not in ctx.callee_arg_names:
        return None
    idx = ctx.callee_arg_names.index(name)
    args = ctx.args[idx]
    if len(args) != 1:
        # Either an error or no value passed.
        return None
    return args[0]


def get_call_argument_type_by_name(ctx: Union[FunctionContext, MethodContext], name: str) -> Optional[MypyType]:
    """Return the type for the specific argument.

    This helper should only be used with non-star arguments.
    """
    if name not in ctx.callee_arg_names:
        return None
    idx = ctx.callee_arg_names.index(name)
    arg_types = ctx.arg_types[idx]
    if len(arg_types) != 1:
        # Either an error or no value passed.
        return None
    return arg_types[0]


def make_optional(typ: MypyType) -> MypyType:
    return UnionType.make_union([typ, NoneTyp()])


def parse_bool(expr: Expression) -> Optional[bool]:
    if isinstance(expr, NameExpr):
        if expr.fullname == 'builtins.True':
            return True
        if expr.fullname == 'builtins.False':
            return False
    return None


def has_any_of_bases(info: TypeInfo, bases: Set[str]) -> bool:
    for base_fullname in bases:
        if info.has_base(base_fullname):
            return True
    return False


def get_private_descriptor_type(type_info: TypeInfo, private_field_name: str, is_nullable: bool) -> MypyType:
    """ Return declared type of type_info's private_field_name (used for private Field attributes)"""
    sym = type_info.get(private_field_name)
    if sym is None:
        return AnyType(TypeOfAny.unannotated)

    node = sym.node
    if isinstance(node, Var):
        descriptor_type = node.type
        if descriptor_type is None:
            return AnyType(TypeOfAny.unannotated)

        if is_nullable:
            descriptor_type = make_optional(descriptor_type)
        return descriptor_type
    return AnyType(TypeOfAny.unannotated)


def get_nested_meta_node_for_current_class(info: TypeInfo) -> Optional[TypeInfo]:
    metaclass_sym = info.names.get('Meta')
    if metaclass_sym is not None and isinstance(metaclass_sym.node, TypeInfo):
        return metaclass_sym.node
    return None


def add_new_class_for_module(module: MypyFile, name: str, bases: List[Instance],
                             fields: 'OrderedDict[str, MypyType]') -> TypeInfo:
    new_class_unique_name = checker.gen_unique_name(name, module.names)

    # make new class expression
    classdef = ClassDef(new_class_unique_name, Block([]))
    classdef.fullname = module.fullname() + '.' + new_class_unique_name

    # make new TypeInfo
    new_typeinfo = TypeInfo(SymbolTable(), classdef, module.fullname())
    new_typeinfo.bases = bases
    calculate_mro(new_typeinfo)
    new_typeinfo.calculate_metaclass_type()

    def add_field_to_new_typeinfo(var: Var, is_initialized_in_class: bool = False,
                                  is_property: bool = False) -> None:
        var.info = new_typeinfo
        var.is_initialized_in_class = is_initialized_in_class
        var.is_property = is_property
        var._fullname = new_typeinfo.fullname() + '.' + var.name()
        new_typeinfo.names[var.name()] = SymbolTableNode(MDEF, var)

    # add fields
    var_items = [Var(item, typ) for item, typ in fields.items()]
    for var_item in var_items:
        add_field_to_new_typeinfo(var_item, is_property=True)

    classdef.info = new_typeinfo
    module.names[new_class_unique_name] = SymbolTableNode(GDEF, new_typeinfo, plugin_generated=True)
    return new_typeinfo


def get_current_module(api: TypeChecker) -> MypyFile:
    current_module = None
    for item in reversed(api.scope.stack):
        if isinstance(item, MypyFile):
            current_module = item
            break
    assert current_module is not None
    return current_module


def make_oneoff_named_tuple(api: TypeChecker, name: str, fields: 'OrderedDict[str, MypyType]') -> TupleType:
    current_module = get_current_module(api)
    namedtuple_info = add_new_class_for_module(current_module, name,
                                               bases=[api.named_generic_type('typing.NamedTuple', [])],
                                               fields=fields)
    return TupleType(list(fields.values()), fallback=Instance(namedtuple_info, []))


def make_tuple(api: 'TypeChecker', fields: List[MypyType]) -> TupleType:
    # fallback for tuples is any builtins.tuple instance
    fallback = api.named_generic_type('builtins.tuple',
                                      [AnyType(TypeOfAny.special_form)])
    return TupleType(fields, fallback=fallback)


def convert_any_to_type(typ: MypyType, referred_to_type: MypyType) -> MypyType:
    if isinstance(typ, UnionType):
        converted_items = []
        for item in typ.items:
            converted_items.append(convert_any_to_type(item, referred_to_type))
        return UnionType.make_union(converted_items,
                                    line=typ.line, column=typ.column)
    if isinstance(typ, Instance):
        args = []
        for default_arg in typ.args:
            if isinstance(default_arg, AnyType):
                args.append(referred_to_type)
            else:
                args.append(default_arg)
        return reparametrize_instance(typ, args)

    if isinstance(typ, AnyType):
        return referred_to_type

    return typ


def make_typeddict(api: CheckerPluginInterface, fields: 'OrderedDict[str, MypyType]',
                   required_keys: Set[str]) -> TypedDictType:
    object_type = api.named_generic_type('mypy_extensions._TypedDict', [])
    typed_dict_type = TypedDictType(fields, required_keys=required_keys, fallback=object_type)
    return typed_dict_type


def resolve_string_attribute_value(attr_expr: Expression, ctx: Union[FunctionContext, MethodContext],
                                   django_context: 'DjangoContext') -> Optional[str]:
    if isinstance(attr_expr, StrExpr):
        return attr_expr.value

    # support extracting from settings, in general case it's unresolvable yet
    if isinstance(attr_expr, MemberExpr):
        member_name = attr_expr.name
        if isinstance(attr_expr.expr, NameExpr) and attr_expr.expr.fullname == 'django.conf.settings':
            if hasattr(django_context.settings, member_name):
                return getattr(django_context.settings, member_name)

    ctx.api.fail(f'Expression of type {type(attr_expr).__name__!r} is not supported', ctx.context)
    return None


def get_typechecker_api(ctx: Union[AttributeContext, MethodContext, FunctionContext]) -> TypeChecker:
    if not isinstance(ctx.api, TypeChecker):
        raise ValueError('Not a TypeChecker')
    return cast(TypeChecker, ctx.api)