#! /bin/bash
#
# tldfind
# Copyright (C) 2020 Vintage Salt <rehashedsalt@cock.li>
#
# Distributed under terms of the MIT license.
#
set -e

# Read-only set-once variables
declare -r _name="$(basename -- "$0")"
# Options
declare _optdict="/usr/share/dict/words"
declare -i _opthelp
declare -i _optverbose
# Working variables
declare -a _args
declare _return

# Helper functions
log() {
	# Print a line to the terminal if _optverbose is greater than $2
	# $2 defaults to 0
	# loglevel 0: Daily-use messages
	# loglevel 1: Detailed but not quite debugging
	# loglevel 2: Definitely debugging
	[ -z "$1" ] && return 1
	if (( _optverbose >= ${2:-0} )); then
		printf "%s\\n" "$1"
	fi
}
warn() {
	# Print a yellow line to the terminal, respecting _optverbose
	[ -z "$1" ] && return 1
	if (( _optverbose >= ${2:-0} )); then
		if [ -t 1 ]; then
			printf "\\e[33m%s\\e[0m\\n" "$1"
		else
			printf "WARN: %s\\n" "$1"
		fi
	fi
}
error() {
	# Print a red line to the terminal, exit if $2 is specified
	[ -z "$1" ] && return 1
	if [ -t 2 ]; then
		printf "\\e[31m%s\\e[0m\\n" "$1" 1>&2
	else
		printf "ERROR: %s\\n" "$1" 1>&2
	fi
	[ -z "$2" ] && return
	exit "${2:-1}"
}
has() {
	# Parse out all arguments and try to find them in path
	# If an argument cannot be found, set _return and fail
	for prog in "$@"; do
		if ! command -v "$prog" > /dev/null 2>&1; then
			_return="$prog"
			return 1
		fi
	done
	return 0
}

# Core program functions
printhelp() {
	cat << EOF
Usage: $_name [OPTION]... [TLD]...
Find available domain names in the dictionary that are whole words ending in
the given TLDs

  -d [FILE]		A dictionary to load. Defaults to /usr/share/dict/words
  -h			Print this help text
  -v			Print more status messages. Stacks

Copyright (c) 2020 rehashedsalt@cock.li
Licensed under the MIT license
EOF
}
checkavaildomains() {
	[ -z "$1" ] && return 1
	# Strip leading periods
	tld="${1#.}"
	tldstrip="${tld//\./}" # Looking at you, .co.in
	while read word; do
		! [[ $word == *$tldstrip ]] && continue
		[[ $word == $tldstrip ]] && continue # Ignore the tld itself
		log "Processing word: $word" 2
		prefix="${word%$tldstrip}"
		fqdn="$prefix.$tld"
		log "Looking for domain: $fqdn" 2
		# We wait here so a ^C kills our program, not nslookup
		nslookup "$fqdn" > /dev/null 2>&1 &
		if ! wait -n; then
			log "$fqdn"
		fi
	done < "$_optdict"
}

# Main
main() {
	# Parse out arguments
	while [ -n "$1" ]; do
		# Parse out flags
		while getopts ":d:hv" opt; do
			case $opt in
				d)
					_optdict="$OPTARG"
					;;
				h)
					_opthelp=1
					;;
				v)
					_optverbose+=1
					;;
				:)
					error "Option requires argument: -$OPTARG" 2
					;;
				*)
					error "Invalid option: -$OPTARG" 2
					;;
			esac
		done
		# Store arguments
		shift $((OPTIND - 1))
		if [ -n "$1" ]; then
			_args+=("$1")
			shift
		fi
		unset OPTIND
	done
	# Early hook for help
	[ -n "$_opthelp" ] && printhelp && exit 0
	# Validate critical options
	if ! [ -f "$_optdict" ]; then
		error "Failed to find dictionary: $_optdict" 1
	fi
	# Validate core program dependencies
	log "Validating dependencies" 2
	if ! has basename; then
		error "Failed to find program: $_return" 1
	fi

	# Do the do
	if [ -n "${_args[*]}" ]; then
		for arg in "${_args[@]}"; do
			if ! checkavaildomains "$arg"; then
				error "Error check domains for TLD: $arg"
			fi
		done
	else
		warn "Nothing to do"
		exit 0
	fi
}

main "$@"