#!/usr/bin/env bash

# Bash Finger client (RFC 1288) using /dev/tcp
# Supports 8-bit chars, long files, ASCII art

# License: Blue Oak Model License 1.0.0

# Install: chmod +x bfinger && sudo cp bfinger /usr/local/bin/
# uninstall: sudo rm /usr/local/bin/bfinger

# v2.2 (2025-11-14): fixed help flags
# v2.1 (2025-10-11): 128k Transfer limit as default, minor other edits
# v2.0 (2025-05-30): Added Transfer limit (BFINGER_MAX_BYTES) & timeouts
# v1.0 (2025-05-01): Initial release

# ------------------------------ Start Script -------------------------------

set -eo pipefail

[ -n "${DEBUG:-}" ] && set -xu  

VERSION="2.2 (Nov 14, 2025)"

export LC_ALL=C

cleanup() {
  exec 3<&- 3>&- 2>/dev/null || true
  exit 130
}
trap cleanup INT

# Transfer limit: default is ~128KB. Adjust as needed.
MAX_BYTES=${BFINGER_MAX_BYTES:-128000}

if [ $# -eq 0 ] || [[ "$1" =~ ^(-h|--help|/\?)$ ]]; then
  echo ""
  echo "bfinger $VERSION - A Bash-based Finger Client (RFC 1288)"
  echo ""
  echo "Uses Bash's /dev/tcp for socket connections to query remote Finger"
  echo "servers. Full support for 8-bit characters, long files and ASCII art."
  echo ""
  echo "Usage:"
  echo "  bfinger @domain.com         # Queries host"
  echo "  bfinger user@domain.com     # Specific user"
  echo "  bfinger user domain.com     # Alternative"
  echo "  bfinger @localhost          # fingerd must be installed locally"
  echo ""
  echo "Options:"
  echo "  -v, --version               Show version info"
  echo "  -h, --help, /?              Show this help message"
  echo ""
  echo "Examples:"
  echo "  bfinger fingerverse@happynetbox.com | less"
  echo "  bfinger @plan.cat | head -n 20"
  echo ""
  echo "install:   chmod +x bfinger && sudo cp bfinger /usr/local/bin"
  echo "uninstall: sudo rm /usr/local/bin/bfinger"
  echo ""
  exit 0
fi

if [[ "${1:-}" == "--version" || "${1:-}" == "-v" ]]; then
  echo
  echo "bfinger $VERSION - A Bash-based finger client"
  echo
  exit 0
fi

if [[ "$1" == @* ]]; then
  USER=""
  HOST="${1#@}"
elif [[ "$1" =~ @ ]]; then
  USER="${1%%@*}"
  HOST="${1##*@}"
else
  USER="${1:-}"
  HOST="${2:-}"
fi

PORT=79

if [ -z "$HOST" ]; then
  echo "Error: No host specified" >&2
  exit 1
fi

if [[ ! "$HOST" =~ ^[a-zA-Z0-9._-]+$ ]]; then
  echo "Error: Hostname contains invalid characters" >&2
  exit 1
fi

if ! getent hosts "$HOST" >/dev/null; then
  echo "Error: Host '$HOST' could not be resolved" >&2
  exit 1
fi

if ! timeout 5 bash -c "exec 3<>/dev/tcp/$HOST/$PORT"; then
  echo "Error: Connection to $HOST:$PORT timed out or failed" >&2
  echo "Tip: Try 'telnet $HOST $PORT' to debug" >&2
  exit 1
fi
exec 3<>/dev/tcp/"$HOST"/"$PORT"

printf "%s\r\n" "$USER" >&3

bytes_read=0
while IFS= read -r -t 5 -N 1 char <&3 && (( bytes_read++ < MAX_BYTES )); do
  printf "%s" "$char"
done
(( bytes_read >= MAX_BYTES )) && echo >&2
(( bytes_read >= MAX_BYTES )) && echo "Output truncated after $MAX_BYTES bytes." >&2

exec 3<&- 3>&-