# plugins/snmp/poller.py
"""
Synchronous SNMP GET helper, run via executor.

Requires pysnmp-lextudio (maintained pysnmp fork):
    pip install 'steward[snmp]'

If pysnmp is not installed, poll_device() returns an empty dict and logs a warning.
"""
from __future__ import annotations
import logging

logger = logging.getLogger(__name__)


def _pysnmp_available() -> bool:
    try:
        import pysnmp  # noqa: F401
        return True
    except ImportError:
        return False


def _mp_model(version: str) -> int:
    """Map version string to pysnmp mpModel integer."""
    return 0 if version == "1" else 1


def poll_device_sync(
    host: str,
    port: int,
    community: str,
    version: str,
    oids: list[dict],
) -> dict[str, float]:
    """
    Perform SNMP GET for each OID and return {label: float_value}.
    Non-numeric OIDs (strings, etc.) are skipped.
    Returns empty dict on any error.
    """
    if not _pysnmp_available():
        logger.warning("pysnmp not installed — SNMP polling disabled. "
                       "Install with: pip install 'steward[snmp]'")
        return {}

    from pysnmp.hlapi import (
        CommunityData,
        ContextData,
        ObjectIdentity,
        ObjectType,
        SnmpEngine,
        UdpTransportTarget,
        getCmd,
    )

    results: dict[str, float] = {}
    engine = SnmpEngine()

    for oid_cfg in oids:
        oid = oid_cfg["oid"]
        label = oid_cfg.get("label") or oid
        scale = float(oid_cfg.get("scale", 1.0))

        try:
            error_indication, error_status, error_index, var_binds = next(
                getCmd(
                    engine,
                    CommunityData(community, mpModel=_mp_model(version)),
                    UdpTransportTarget((host, port), timeout=5, retries=1),
                    ContextData(),
                    ObjectType(ObjectIdentity(oid)),
                )
            )
        except Exception as exc:
            logger.debug("SNMP GET %s@%s OID %s failed: %s", host, port, oid, exc)
            continue

        if error_indication:
            logger.debug("SNMP error %s@%s OID %s: %s", host, port, oid, error_indication)
            continue
        if error_status:
            logger.debug("SNMP status %s@%s OID %s: %s at %s",
                         host, port, oid, error_status.prettyPrint(),
                         error_index and var_binds[int(error_index) - 1][0] or "?")
            continue

        for _, val in var_binds:
            try:
                results[label] = float(val) * scale
            except (TypeError, ValueError):
                # Non-numeric type (e.g. OctetString description) — skip
                logger.debug("SNMP non-numeric value for %s label=%s: %r", oid, label, val)

    return results