"""Meter data model and rtlamr output parsing."""

import json
import logging
from dataclasses import dataclass
from datetime import datetime, timezone
from typing import Optional

from hameter.config import MeterConfig

logger = logging.getLogger(__name__)

# Map rtlamr message Type to the field containing the meter ID.
PROTOCOL_ID_FIELDS: dict[str, str] = {
    "SCM": "ID",
    "SCM+": "EndpointID",
    "IDM": "ERTSerialNumber",
    "NetIDM": "ERTSerialNumber",
    "R900": "ID",
    "R900BCD": "ID",
}

# Map rtlamr message Type to the field containing the consumption value.
PROTOCOL_CONSUMPTION_FIELDS: dict[str, str] = {
    "SCM": "Consumption",
    "SCM+": "Consumption",
    "IDM": "LastConsumptionCount",
    "NetIDM": "LastConsumptionCount",
    "R900": "Consumption",
    "R900BCD": "Consumption",
}


@dataclass
class MeterReading:
    meter_id: int
    protocol: str
    raw_consumption: int
    calibrated_consumption: float
    timestamp: str
    raw_message: dict


def parse_rtlamr_line(
    line: str,
    meters: dict[int, MeterConfig],
) -> Optional[MeterReading]:
    """Parse a single JSON line from rtlamr stdout.

    Args:
        line: Raw JSON string from rtlamr.
        meters: Dict mapping meter ID to config. If empty, accept all meters
                (discovery mode).

    Returns:
        MeterReading if the line matches a configured meter (or any meter in
        discovery mode), otherwise None.
    """
    data = json.loads(line)
    msg_type = data.get("Type", "")
    message = data.get("Message", {})

    id_field = PROTOCOL_ID_FIELDS.get(msg_type)
    consumption_field = PROTOCOL_CONSUMPTION_FIELDS.get(msg_type)

    if not id_field or not consumption_field:
        return None

    meter_id = int(message.get(id_field, 0))
    if meter_id == 0:
        return None

    raw_consumption = int(message.get(consumption_field, 0))

    # Filter: if meters dict is populated, only accept configured meters.
    if meters and meter_id not in meters:
        return None

    meter_cfg = meters.get(meter_id)
    multiplier = meter_cfg.multiplier if meter_cfg else 1.0
    calibrated = raw_consumption * multiplier

    timestamp = data.get("Time") or datetime.now(timezone.utc).isoformat()

    return MeterReading(
        meter_id=meter_id,
        protocol=msg_type,
        raw_consumption=raw_consumption,
        calibrated_consumption=round(calibrated, 4),
        timestamp=timestamp,
        raw_message=message,
    )