def initialise_SoC(bess):
    """Initialise the state of charge (SoC) for the BESS."""
    for i in range(0, len(bess["units"])):  # initially fully charged
        bess["units"][i]["SoC"] = 1
    return bess


def initial_site_assignment(c, bess):
    """Initialise the site assignment for each BESS."""
    k = 0
    while k < len(c["site_info"]["sites"]):
        bess["units"][k]["site"] = c["site_info"]["sites"][k]["name"]
        k += 1

    if k < len(c["site_info"]["sites"]):
        bess["units"][k]["site"] = "Unassigned"
    return bess


def discharge_bess(bess, site_name, dt, discharge_power):
    # convert discharge power to discharge energy (kW to kWh)
    discharge_energy = discharge_power * dt / 3600

    """Discharge the BESS for a specific site."""
    for index, unit in enumerate(bess["units"]):
        if unit["site"] == site_name:
            new_soc = unit["SoC"] - (dt * discharge_energy) / unit["capacity_kWh"]
            new_soc = 0 if new_soc < 0 else new_soc
        else:
            new_soc = unit["SoC"]

        # update SoC
        bess["units"][index]["SoC"] = new_soc
    return bess


def predict_swap_time(bess_soc_for_cycle):
    """Predict the swap time for each BESS unit based on its SoC history."""
    swap_times = {}
    for unit_name, df in bess_soc_for_cycle.items():
        # Find the timestamp when SoC reaches 0
        swap_time = df[df["SoC"] == 0]["Timestamp"].min()
        swap_times[unit_name] = swap_time
    return swap_times