import argparse
import time
from datetime import datetime, timezone

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)
    parser.add_argument("--daemon", action="store_true", help="Run continuously until stopped (Ctrl+C)")
    parser.add_argument("--csv", default="hopi_readings.csv", help="CSV output path for daemon mode")
    parser.add_argument("--interval", type=float, default=1.0, help="Seconds between reads in daemon mode")
    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()

    if args.daemon:
        if args.timeout <= 0:
            raise ValueError("--timeout must be > 0")
        if args.interval <= 0:
            raise ValueError("--interval must be > 0")
        if args.interval <= args.timeout:
            raise ValueError("--interval must be > --timeout")

        next_deadline = time.monotonic()
        with client, handler.open_csv_logger(args.csv) as logger:
            try:
                while True:
                    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)

                    row = {"timestamp": datetime.now(timezone.utc).isoformat()}
                    row.update(handler.readings_to_flat_dict(readings))
                    logger.log(row)

                    next_deadline += args.interval
                    sleep_for = next_deadline - time.monotonic()
                    if sleep_for > 0:
                        time.sleep(sleep_for)
            except KeyboardInterrupt:
                return

    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()