from dataclasses import dataclass
from enum import Enum, auto
from typing import TypeVar, List

T = TypeVar("T", int, float, str, bool)

# classes
class NebType(Enum):
    INT = auto()
    FLOAT = auto()
    STRING = auto()
    BOOL = auto()

@dataclass
class NebToken:
    pass

@dataclass
class NebLiteral(NebToken):
    type_: NebType
    value: T

class NebSeparator(NebToken):
    pass

class NebOpen(NebSeparator):
    pass

class NebClose(NebSeparator):
    pass

@dataclass
class NebSymbol(NebToken):
    name: str

@dataclass
class NebExpression(NebToken):
    symbol: NebSymbol
    args: List[NebToken]

    def maybe_sig(self):
        out = []
        for arg in self.args:
            if isinstance(arg, NebLiteral):
                out.append(":" + arg.type_.name.lower())
            else:
                raise Exception("expressions must have a list of literals") #TODO not true
        return " ".join(out)

@dataclass
class NebFunction(NebToken):
    name: str
    args: List[NebType]
    returns: NebType
    
    def in_sig(self):
        return " ".join(":" + x.name.lower() for x in self.args)
    
    def out_sig(self):
        return ":" + self.returns.lower()

    def sig(self):
        return (self.in_sig() + " > " + self.out_sig()).strip()