from abc import ABC, abstractmethod
from dataclasses import dataclass


@dataclass
class Layer:
    thermal_coefficient: float
    thickness: float

    @property
    def R(self):
        return self.thickness / self.thermal_coefficient


@dataclass
class Interface(ABC):
    name: str
    area: float

    @property
    @abstractmethod
    def U(self) -> float: ...


@dataclass
class LayeredInterface(Interface):
    layers: list[Layer]
    r_surface_1: float
    r_surface_2: float

    @property
    def U(self) -> float:
        R_layers = sum(layer.R for layer in self.layers)
        R = self.r_surface_1 + R_layers + self.r_surface_2
        return 1 / R


@dataclass
class FixedUInterface(Interface):
    u_value: float

    @property
    def U(self) -> float:
        return self.u_value