import argparse

from hopi.data_handler import PowerMeterDataHandler
from hopi.serial_client import ModbusRtuSerialClient, SerialConfig


SLAVE_ID = 1
START_REG = 0
NUM_WORDS = 20
READ_MAX_BYTES = 5 + (2 * NUM_WORDS)


def build_arg_parser() -> argparse.ArgumentParser:
    parser = argparse.ArgumentParser(description="Read and print power meter values over Modbus RTU.")
    parser.add_argument("--port", default="/dev/ttyUSB0")
    parser.add_argument("--baud", type=int, default=9600)
    parser.add_argument("--timeout", type=float, default=0.1)
    return parser


def main() -> None:
    args = build_arg_parser().parse_args()

    config = SerialConfig(port=args.port, baudrate=args.baud, timeout=args.timeout)
    client = ModbusRtuSerialClient(config)
    handler = PowerMeterDataHandler()

    with client:
        response = client.read_holding_registers(
            slave_id=SLAVE_ID,
            start_register=START_REG,
            register_count=NUM_WORDS,
            read_max_bytes=READ_MAX_BYTES,
            exact_response_length=True,
        )

    registers = handler.parse_read_holding_registers_response(response)
    readings = handler.decode_readings(registers)

    handler.print_readings_json(readings)


if __name__ == "__main__":
    main()