#!/bin/bash


# (1) Init.
#--------------------------------------------------------#
# (1) Get current absolute dir
ROOT=$(dirname `realpath $0`);

# (2) Check argc
test $# -lt 2 && echo -e "error: too fewarguments\n\n\e[1mUSAGE\e[0m\n\tpool <id> <port>\n\n\e[1mARGUMENTS\e[0m\n\t<id>\tThe identifier of the pool (client must match it)\n\t<port>\tTo port to listen to\n" && exit 1;

# (3) Check @PORT range #
MIN_PORT=49152;
MAX_PORT=65535;
test "$2" -gt "$MAX_PORT" -o "$2" -lt "$MIN_PORT" && echo "error: <port> must be between $MIN_PORT and $MAX_PORT" && exit 1;

# (4) Set argument explicit names #
POOL_ID="$1";
POOL_PT="$2";


# (2) Launch pool listener
#--------------------------------------------------------#
# (1) Start the script in background
listfail=0;

# infinite listener
while true; do

	# Listen on port @2
	echo "(.) listen $POOL_PT";
	MSG=`nc -lp $POOL_PT`;

	# Do nothing if empty msg
	test -z "$MSG" && continue;

	# Extract ID - PORT
	CLI_ID="`echo -ne \"$MSG\" | sed 's/^\(.\+\):\(.\+\)$/\1/'`";
	CLI_PT="`echo -ne \"$MSG\" | sed 's/^\(.\+\):\(.\+\)$/\2/'`";

	# if ID does not match
	test "$CLI_ID" != "$POOL_ID" && echo "    /!\\ wrong id" && continue;

	# create new listening socket
	echo "    [x] creating socket";

	# Find an available port
	PORT="$MIN_PORT";

	while true; do

		test "$PORT" = "$POOL_PT" && PORT="`expr $PORT + 1`" && continue;

		echo -n "    ?? port $PORT -> ";
		ss -tl4 "( sport = :$PORT )" | grep "$PORT" >/dev/null 2>&1 || (echo "free"; exit 1) || break;

		echo "used";
		PORT="`expr $PORT + 1`";

	done;

	echo "    > listen $PORT";

done;