import argparse
import struct


def get_argparser():
    parser = argparse.ArgumentParser(description="MQTT-controlled 4-channel DDS signal generator")

    parser.add_argument("cidr", nargs=1,
                        metavar=("Client_CIDR"),
                        help="IPv4 Address of Humpback-DDS in CIDR notation")
    parser.add_argument("mac_addr", nargs=1,
                        metavar=("Client_MAC"),
                        help="MAC Address of Humpback-DDS")
    parser.add_argument("broker_ip", nargs=1,
                        metavar=("Broker_IP"),
                        help="IP address of MQTT broker")
    parser.add_argument("name", nargs=1,
                        metavar=("Name"),
                        help="Device name of Humpback-DDS")

    return parser


def write_record(f, key, value):
    key_size = len(key) + 1
    value_size = len(value)
    record_size = key_size + value_size + 4
    f.write(struct.pack("<l", record_size))
    f.write(key.encode())
    f.write(b"\x00")
    f.write(value)


def write_end_marker(f):
    f.write(b"\xff\xff\xff\xff")


def main():
    args = get_argparser().parse_args()
    with open("flash_config.bin", "wb") as fo:
        write_record(fo, "CIDR", args.cidr[0].encode())
        write_record(fo, "MAC", args.mac_addr[0].encode())
        write_record(fo, "BrokerIP", args.broker_ip[0].encode())
        write_record(fo, "Name", args.name[0].encode())
        write_end_marker(fo)


if __name__ == "__main__":
    main()