#!/bin/sh

# The MIT License (MIT)
#
# Copyright © 2020-2025 pacman64
#
# 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.


# tcpecho [port] [words...]
#
# Start a TCP server which always replies with a plain-text line made from
# the arguments given after the port number, joined by single spaces.


case "$1" in
    -h|--h|-help|--help)
        awk '/^# +tcpecho /, /^$/ { gsub(/^# ?/, ""); print }' "$0"
        exit 0
    ;;
esac

if [ -z "$1" ]; then
    awk '/^# +tcpecho /, /^$/ { gsub(/^# ?/, ""); print }' "$0"
    exit 0
fi

port="$1"
[ $# -gt 0 ] && shift

gawk -v port="${port}" -v msg="$*" '
BEGIN {
    if (port < 1 || port > 65535) {
        fmt = "\x1b[31m%s is an invalid port number\x1b[0m\n"
        printf(fmt, port) > "/dev/stderr"
        exit 1
    }

    if (msg == "") {
        printf "\x1b[31myou forgot the reply message\x1b[0m\n" > "/dev/stderr"
        exit 1
    }

    gsub(/^ *| *$/, "", msg)

    server = sprintf("/inet/tcp/%d/0/0", port)
    PROCINFO[server, "READ_TIMEOUT"] = 200
    printf("listening on telnet://localhost:%d\n", port) > "/dev/stderr"

    while (1) {
        printf("%s\n", msg) |& server
        close(server)
    }

    exit
}
'