---

#!/usr/bin/env bash

set -uo pipefail

#
# Check numeric OIDs against an SNMP v2c agent.
#
# Usage:
#   ./validate-oids.sh <input-file> <agent-address> \
#                      <existing-output> <removed-output>
#
# Example:
#   ./validate-oids.sh \
#       aqnos_oids.txt \
#       192.168.100.100 \
#       existing_oids.txt \
#       removed_oids.txt
#
# SNMP settings:
#   Version:   v2c
#   Community: public
#

if [[ $# -ne 4 ]]; then
    echo "Usage: $0 <input-file> <agent-address> <existing-output> <removed-output>" >&2
    exit 1
fi

INPUT_FILE="$1"
AGENT="$2"
EXISTING_FILE="$3"
REMOVED_FILE="$4"

COMMUNITY="public"

if [[ ! -f "$INPUT_FILE" ]]; then
    echo "Error: input file does not exist: $INPUT_FILE" >&2
    exit 1
fi

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

# Clear/create output files.
: > "$EXISTING_FILE"
: > "$REMOVED_FILE"

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

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

    # Remove Windows CR.
    oid="${oid%$'\r'}"

    # Remove leading/trailing whitespace.
    oid="${oid#"${oid%%[![:space:]]*}"}"
    oid="${oid%"${oid##*[![:space:]]}"}"

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

    ((TOTAL += 1))

    echo "Checking: $oid" >&2

    #
    # Run snmpwalk and capture both output and exit status.
    #
    # Using "if" here prevents a non-zero snmpwalk exit code
    # from terminating the script.
    #
    if output=$(
        snmpwalk \
            -v2c \
            -c "$COMMUNITY" \
            -t 2 \
            -r 1 \
            "$AGENT" \
            "$oid" \
            2>&1
    ); then
        status=0
    else
        status=$?
    fi

    #
    # OID explicitly doesn't exist.
    #
    if grep -Eqi \
        'No Such Object|No Such Instance|NoSuchObject|NoSuchInstance' \
        <<< "$output"
    then
        echo "  REMOVED: no such object/instance" >&2
        echo "$oid" >> "$REMOVED_FILE"

        ((REMOVED += 1))
        continue
    fi

    #
    # Successful SNMP query.
    #
    if [[ $status -eq 0 ]]; then
        echo "  EXISTS" >&2
        echo "$oid" >> "$EXISTING_FILE"

        ((KEPT += 1))
        continue
    fi

    #
    # Unexpected error:
    # timeout, unreachable agent, authentication problem, etc.
    #
    # We do NOT classify the OID as missing because the failure
    # does not prove that the OID itself does not exist.
    #
    echo "  ERROR: could not determine OID status" >&2
    echo "         $output" >&2

    ((ERRORS += 1))

done < "$INPUT_FILE"

echo >&2
echo "========================================" >&2
echo "Validation finished" >&2
echo "========================================" >&2
echo "Agent:          $AGENT" >&2
echo "Input:          $INPUT_FILE" >&2
echo "Existing OIDs:  $EXISTING_FILE" >&2
echo "Removed OIDs:   $REMOVED_FILE" >&2
echo >&2
echo "Checked:        $TOTAL" >&2
echo "Existing:       $KEPT" >&2
echo "Removed:        $REMOVED" >&2
echo "Other errors:   $ERRORS" >&2