class Battery:
    def __init__(self, e_max_mwh, p_ch_max, p_dis_max, eta_ch, eta_dis):
        self.e_max = e_max_mwh
        self.p_ch_max = p_ch_max
        self.p_dis_max = p_dis_max
        self.eta_ch = eta_ch
        self.eta_dis = eta_dis
        self.soc = 0.5 * self.e_max  # Start at 50% (10 MWh)

    def reset(self):
        self.soc = 0.5 * self.e_max
        return self.soc

    def step(self, action_fraction, dt_hours):
        """
        action_fraction: -1 (Full Charge) to 1 (Full Discharge)
        """
        if action_fraction < 0:  # Charging
            p_mw = max(action_fraction * self.p_ch_max, -self.p_ch_max)
            # SoC increases by (Power * Time * Efficiency)
            self.soc += abs(p_mw) * dt_hours * self.eta_ch
        else:  # Discharging
            p_mw = min(action_fraction * self.p_dis_max, self.p_dis_max)
            # SoC decreases by (Power * Time / Efficiency)
            self.soc -= (p_mw * dt_hours) / self.eta_dis
            
        self.soc = max(0.0, min(self.e_max, self.soc))
        return self.soc