#!/bin/sh

# irc; Deven Blake 2022; Public domain
# I stopped understanding this at 81 lines.

alias cat='cat -u'
alias sed='sed -u'

# defaults
DEFAULT_HOST="example.com"
PORT=6667
[ -n "$IRC_QUIT_MESSAGE" ] \
	|| IRC_QUIT_MESSAGE="Bye bye!"

# defaults (standard-defined)
URI_FRAGMENT_DELIMITER='#' # RFC 3986

argv0="$0"
URL="$1"

usage(){
	printf "Usage: %s [url]\n" "$argv0"
	exit 1
}

one_character_per_line(){
	sed 's/./&\n/g'
}

host_ex_url(){
	# filter out scheme URI subcomponent
	# filter out userinfo URI subcomponent
	# filter out port
	# filter out heirarchy path
	# filter out query
	# filter out fragment
	printf "%s\n" "$URL" \
		| sed 's/.*:\/\///' \
		| sed 's/.*@//' \
		| sed 's/:.*$//' \
		| sed 's/\/.*$//' \
		| sed 's/\?.*$//' \
		| sed 's/#.*$//'
}

port_ex_url(){
	# filter out scheme URI subcomponent
	# filter out userinfo URI subcomponent
	local_url="$(printf "%s\n" "$URL" \
		| sed 's/.*:\/\///' \
		| sed 's/.*@//')"

	# check to ensure there Is a port in the URL
	# this will also catch if we fucked up
	if ! [ "$(printf "%s\n" "$local_url" \
			| one_character_per_line \
			| grep ':' \
			| wc -l)" \
		= 1 ]
	then
		# give up, gracefully
		printf "%s\n" "$PORT"
		return 0
	fi

	# filter out query URI subcomponent
	# filter out heirarchy path
	# filter out everything preceding the port
	local_url="$(printf "%s\n" "$local_url" \
		| sed 's/\?.*$//' \
		| sed 's/\/.*$//' \
		| sed 's/.*://')"

	printf "%s\n" "$local_url"
}

username_ex_url(){
	# only go if there's actually userinfo in the URL
	# filter out scheme URI subcomponent
	# filter out everything after userinfo URI subcomponent
	# filter out password in userinfo, if present
	printf "%s\n" "$URL" \
		| grep '@' \
		| sed 's/.*:\/\///' \
		| sed 's/@.*$//' \
		| sed 's/:.*$//'
}

[ -n "$URL" ] \
	|| usage

[ -n "$IRC_NICK" ] \
	|| IRC_NICK="$USER"

# check if URL matches /^irc:\/\//
if ! printf "%s\n" "$URL" | grep "^irc://" >/dev/null 2>&1; then
	printf "%s: %s: URL incorrectly formatted or scheme not specified.\n" "$argv0" "$URL"
	exit 1
fi

# easy; the fragment is the last part of the URI
CHANNEL="#$(printf "%s\n" "$URL" \
	| sed 's/.*#//' )"

# not easy
PORT="$(port_ex_url)"

# slow, so don't rerun
a="$(username_ex_url)"
[ -z "$a" ] \
	|| IRC_NICK="$a"

HOST="$(host_ex_url)"

[ -n "$HOST" ] \
	|| HOST="$DEFAULT_HOST"

if ! TEMP="$(mktemp)" || ! TEMP_FIN="$(mktemp)"; then
	printf "%s: mktemp: Could not make temporary file.\n" "$argv0"
	exit 1
fi

# RFC 1459 section 4.1.2
printf "NICK %s\n" "$IRC_NICK" >"$TEMP"

# RFC 1459 section 4.1.3; USER <username> <hostname> <servername> <realname>
# not really important
printf "USER %s 0 0 :\n" "$IRC_NICK" >>"$TEMP"

# RFC 1459 section 4.2.1
printf "JOIN %s\n" "$CHANNEL" >>"$TEMP"

# RFC 1459 section 4.1.6
printf "QUIT :%s\n" "$IRC_QUIT_MESSAGE" >"$TEMP_FIN"

# RFC 1459 section 4.4.1
sed "s/^/PRIVMSG $CHANNEL :/g" \
	| cat "$TEMP" /dev/stdin "$TEMP_FIN" \
	| nc "$HOST" "$PORT"