#!/usr/bin/env bash
# SPDX-License-Identifier: MIT

# finger.bash
# A simple finger client written in pure Bash

# Copyright © 2025 Giuseppe Masino <self@qub1750ul.me>
#
# Permission is hereby granted, free of charge, to any person obtaining a
# copy of this software and associated documentation files (the “Software”),
# to deal in the Software without restriction, including without limitation 
# the rights to use, copy, modify, merge, publish, distribute, sublicense, 
# and/or sell copies of the Software, and to permit persons to whom the 
# Software is furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
# THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
# DEALINGS IN THE SOFTWARE.

set -o errexit
set -o nounset
set -o pipefail
shopt -s lastpipe

log() { builtin echo "finger.bash: $*" >&2 ;}
info() { log "INFO: $*" ;}
warn() { log "WARN: $*" ;}
error() { log "ERROR: $*" ; }

finger()
{
	if ! [[ "$*" =~ (^[^@ ]+)?(@([^\/: ]+)(:([0-9]+))?)? ]] ; then
		error "'$1'" is not a valid finger URI
		exit 1
	fi

	declare -g subject="${BASH_REMATCH[1]:-}"
	declare -g host="${BASH_REMATCH[3]:-${host:-localhost}}"
	declare -g port="${BASH_REMATCH[5]:-${port:-79}}"
	npCharWarned=false

	info "querying $host:$port"
	exec 3<>"/dev/tcp/${host}/${port}" 
	
	if ! [ -e /proc/$$/fd/3 ] ; then
		error "failed establishing connection"
		exit 1
	fi

	printf "%s\r\n" "$subject" >&3
	while read -r ; do

		if [[ "$REPLY" =~ "[^ -~]+" ]] && ! $npCharWarned ; then
			warn "server returned non printable data. Stripping it."
			npCharWarned=true
		fi
	
		echo "${REPLY//[^ -~]/}"
	done <&3 
	npCharWarned=false
}

if ! [ "$1" = "-i" ] ; then
	finger "$@" && exit 0 
else
	shift
	finger "$@"
	while read -p 'finger> ' -r query ; do case "$query" in
		('') ;;
		(\?) finger ;;
		('\?') finger ? ;;
		(*) finger "$query" ;;
	esac ; done
fi