from ScEpTIC.emulator.energy import energy_utils
from ScEpTIC.exceptions import ConfigurationException
from ScEpTIC.emulator.energy.energy_source import EnergySourceModel


class EnergyHarvesterModel:
    """
    Base class of an energy harvester.
    """

    __DEFAULT_R = 30000.0

    def __init__(self, equivalent_resistance=None):
        """
        :param equivalent_resistance: Equivalent resistance of the energy harvester.
        """
        self.energy_source = None
        self.equivalent_resistance = self.__DEFAULT_R

        self.update_energy_source_load_resistance = False

        if equivalent_resistance is not None:
            self.set_equivalent_resistance(equivalent_resistance)

        # Proxy energy source method
        self.get_current_sample_remaining_time = lambda: exec('raise Exception("Energy source not attached!")')

    def set_equivalent_resistance(self, r):
        """
        Sets the energy harvester equivalent resistance
        :param r: the equivalent resistance (str)
        """
        self.equivalent_resistance = energy_utils.str_to_float(r)

        if self.update_energy_source_load_resistance and self.energy_source is not None:
            self.energy_source.set_load_resistance(self.equivalent_resistance)

    def get_equivalent_resistance(self):
        """
        :return: The equivalent resistance of the energy harvester.
        """
        return self.equivalent_resistance

    def attach_energy_source(self, energy_source):
        """
        :param energy_source: an energy source model
        """
        if not isinstance(energy_source, EnergySourceModel):
            raise ConfigurationException(f"{self.__class__.__name__}.attach_energy_source() requires a EnergySourceModel but {energy_source.__class__.__name__} was given")

        self.energy_source = energy_source
        self.get_current_sample_remaining_time = energy_source.get_current_sample_remaining_time

        if self.energy_source.load_resistance_unset():
            self.update_energy_source_load_resistance = True

        if self.update_energy_source_load_resistance:
            self.energy_source.set_load_resistance(self.equivalent_resistance)


    def get_voltage(self):
        """
        :return: energy harvester current voltage
        """
        raise NotImplementedError(f"{self.__class__.__name__} must implement get_voltage()")


    def get_voltage_intervals(self, t):
        """
        Returns voltage intervals of the energy source
        :param t: elapsed time
        :return: a list of (voltage, energy, elapsed_time)
        """
        raise NotImplementedError(f"{self.__class__.__name__} must implement get_voltage_intervals()")