---

#!/usr/bin/env bash

set -euo pipefail

#
# Validate OIDs against a remote SNMP agent.
#
# Usage:
#   ./validate-oids.sh <oid-file>
#
# Example:
#   ./validate-oids.sh aqnos_oids.txt
#
# The input file is replaced with a filtered version containing
# only OIDs that appear to exist on the remote SNMP agent.
#

if [[ $# -ne 1 ]]; then
    echo "Usage: $0 <oid-file>" >&2
    exit 1
fi

OID_FILE="$1"

AGENT="192.168.100.100"
COMMUNITY="public"

if [[ ! -f "$OID_FILE" ]]; then
    echo "Error: file not found: $OID_FILE" >&2
    exit 1
fi

if ! command -v snmpwalk >/dev/null 2>&1; then
    echo "Error: snmpwalk is not installed." >&2
    exit 1
fi

TMP_FILE="$(mktemp)"
trap 'rm -f "$TMP_FILE"' EXIT

TOTAL=0
KEPT=0
REMOVED=0
ERRORS=0

while IFS= read -r oid || [[ -n "$oid" ]]; do

    # Remove CR from Windows-style files.
    oid="${oid%$'\r'}"

    # Ignore blank lines.
    [[ -z "$oid" ]] && continue

    ((TOTAL += 1))

    echo "Checking $oid ..." >&2

    #
    # Capture both stdout and stderr because Net-SNMP may print
    # SNMP errors to either depending on the situation/version.
    #
    output="$(
        snmpwalk \
            -v2c \
            -c "$COMMUNITY" \
            -t 2 \
            -r 1 \
            "$AGENT" \
            "$oid" \
            2>&1
    )"
    status=$?

    #
    # Typical responses include:
    #
    #   No Such Object available on this agent at this OID
    #
    #   No Such Instance currently exists at this OID
    #
    # We treat both as "OID does not exist".
    #
    if grep -Eqi \
        'No Such Object|No Such Instance|NoSuchObject|NoSuchInstance' \
        <<< "$output"
    then
        echo "  REMOVE: object does not exist" >&2
        ((REMOVED += 1))
        continue
    fi

    #
    # If snmpwalk returned successfully, keep it.
    #
    if [[ $status -eq 0 ]]; then
        echo "$oid" >> "$TMP_FILE"

        echo "  KEEP" >&2
        ((KEPT += 1))
        continue
    fi

    #
    # Do NOT remove an OID because of timeout, authentication,
    # transport or other unexpected errors.
    #
    echo "  WARNING: SNMP error; keeping OID" >&2
    echo "           $output" >&2

    echo "$oid" >> "$TMP_FILE"

    ((KEPT += 1))
    ((ERRORS += 1))

done < "$OID_FILE"

#
# Replace original file only after all checks have completed.
#
mv "$TMP_FILE" "$OID_FILE"
trap - EXIT

echo >&2
echo "========================================" >&2
echo "Validation finished" >&2
echo "========================================" >&2
echo "Agent:   $AGENT" >&2
echo "File:    $OID_FILE" >&2
echo >&2
echo "Checked: $TOTAL" >&2
echo "Kept:    $KEPT" >&2
echo "Removed: $REMOVED" >&2
echo "Errors:  $ERRORS" >&2