"""Various utilities that don't depend on other modules in mypyc.irbuild."""

from typing import Dict, Any, Union, Optional

from mypy.nodes import (
    ClassDef, FuncDef, Decorator, OverloadedFuncDef, StrExpr, CallExpr, RefExpr, Expression,
    IntExpr, FloatExpr, Var, NameExpr, TupleExpr, UnaryExpr, BytesExpr,
    ArgKind, ARG_NAMED, ARG_NAMED_OPT, ARG_POS, ARG_OPT, GDEF,
)


DATACLASS_DECORATORS = {
    'dataclasses.dataclass',
    'attr.s',
    'attr.attrs',
}


def is_trait_decorator(d: Expression) -> bool:
    return isinstance(d, RefExpr) and d.fullname == 'mypy_extensions.trait'


def is_trait(cdef: ClassDef) -> bool:
    return any(is_trait_decorator(d) for d in cdef.decorators) or cdef.info.is_protocol


def dataclass_decorator_type(d: Expression) -> Optional[str]:
    if isinstance(d, RefExpr) and d.fullname in DATACLASS_DECORATORS:
        return d.fullname.split('.')[0]
    elif (isinstance(d, CallExpr)
            and isinstance(d.callee, RefExpr)
            and d.callee.fullname in DATACLASS_DECORATORS):
        name = d.callee.fullname.split('.')[0]
        if name == 'attr' and 'auto_attribs' in d.arg_names:
            # Note: the mypy attrs plugin checks that the value of auto_attribs is
            # not computed at runtime, so we don't need to perform that check here
            auto = d.args[d.arg_names.index('auto_attribs')]
            if isinstance(auto, NameExpr) and auto.name == 'True':
                return 'attr-auto'
        return name
    else:
        return None


def is_dataclass_decorator(d: Expression) -> bool:
    return dataclass_decorator_type(d) is not None


def is_dataclass(cdef: ClassDef) -> bool:
    return any(is_dataclass_decorator(d) for d in cdef.decorators)


def dataclass_type(cdef: ClassDef) -> Optional[str]:
    for d in cdef.decorators:
        typ = dataclass_decorator_type(d)
        if typ is not None:
            return typ
    return None


def get_mypyc_attr_literal(e: Expression) -> Any:
    """Convert an expression from a mypyc_attr decorator to a value.

    Supports a pretty limited range."""
    if isinstance(e, (StrExpr, IntExpr, FloatExpr)):
        return e.value
    elif isinstance(e, RefExpr) and e.fullname == 'builtins.True':
        return True
    elif isinstance(e, RefExpr) and e.fullname == 'builtins.False':
        return False
    elif isinstance(e, RefExpr) and e.fullname == 'builtins.None':
        return None
    return NotImplemented


def get_mypyc_attr_call(d: Expression) -> Optional[CallExpr]:
    """Check if an expression is a call to mypyc_attr and return it if so."""
    if (
        isinstance(d, CallExpr)
        and isinstance(d.callee, RefExpr)
        and d.callee.fullname == 'mypy_extensions.mypyc_attr'
    ):
        return d
    return None


def get_mypyc_attrs(stmt: Union[ClassDef, Decorator]) -> Dict[str, Any]:
    """Collect all the mypyc_attr attributes on a class definition or a function."""
    attrs: Dict[str, Any] = {}
    for dec in stmt.decorators:
        d = get_mypyc_attr_call(dec)
        if d:
            for name, arg in zip(d.arg_names, d.args):
                if name is None:
                    if isinstance(arg, StrExpr):
                        attrs[arg.value] = True
                else:
                    attrs[name] = get_mypyc_attr_literal(arg)

    return attrs


def is_extension_class(cdef: ClassDef) -> bool:
    if any(
        not is_trait_decorator(d)
        and not is_dataclass_decorator(d)
        and not get_mypyc_attr_call(d)
        for d in cdef.decorators
    ):
        return False
    if cdef.info.typeddict_type:
        return False
    if cdef.info.is_named_tuple:
        return False
    if (cdef.info.metaclass_type and cdef.info.metaclass_type.type.fullname not in (
            'abc.ABCMeta', 'typing.TypingMeta', 'typing.GenericMeta')):
        return False
    return True


def get_func_def(op: Union[FuncDef, Decorator, OverloadedFuncDef]) -> FuncDef:
    if isinstance(op, OverloadedFuncDef):
        assert op.impl
        op = op.impl
    if isinstance(op, Decorator):
        op = op.func
    return op


def concrete_arg_kind(kind: ArgKind) -> ArgKind:
    """Find the concrete version of an arg kind that is being passed."""
    if kind == ARG_OPT:
        return ARG_POS
    elif kind == ARG_NAMED_OPT:
        return ARG_NAMED
    else:
        return kind


def is_constant(e: Expression) -> bool:
    """Check whether we allow an expression to appear as a default value.

    We don't currently properly support storing the evaluated
    values for default arguments and default attribute values, so
    we restrict what expressions we allow.  We allow literals of
    primitives types, None, and references to Final global
    variables.
    """
    return (isinstance(e, (StrExpr, BytesExpr, IntExpr, FloatExpr))
            or (isinstance(e, UnaryExpr) and e.op == '-'
                and isinstance(e.expr, (IntExpr, FloatExpr)))
            or (isinstance(e, TupleExpr)
                and all(is_constant(e) for e in e.items))
            or (isinstance(e, RefExpr) and e.kind == GDEF
                and (e.fullname in ('builtins.True', 'builtins.False', 'builtins.None')
                     or (isinstance(e.node, Var) and e.node.is_final))))