#!/bin/bash

# usage:
#  [[ $(host_reachable host.net) ]] && echo sure ||  echo nope
# or
# host_reachable &> /dev/null && echo sure || echo nope
# or

host_reachable () {
# usage:  host_reachable < -F configfile > host < port >    
# reachable returns yes and return 0 
# return 1 - not reachable
# return 2 no method available to try

local host; local config

function try( ) (    
        if [[ $(command -v nmap) ]] && [[ $2 ]]; then
        [[ $(nmap $1 -PN -p $2 | grep open) ]] && echo yes && return 0 || return 1
        fi
        if [[ $(command -v nc) ]] && [[ $2 ]]; then
        [[ $(nc -w 2 $1 $2) ]] && echo yes && return 0 || return 1
        fi
        if [[ $(command -v ping) ]]; then
        ping -c1 -W1 $1 &> /dev/null && echo yes && return 0 || return 1
        fi
        return 2  # return 2 to indicate no method was available
)

[[ $1 = "-F " ]] && { config=$2;shift 2; }
host=$(lookup_host $1 $config)
try $host $2
return $?
}

lookup_host () {
# usage:  lookup_host hostname < configfile >    
local config; local host; local lhost
config=$([[ $2 ]] && echo $2 || echo ${SSH_CONFIG:-$HOME/.ssh/config})
host=$(parse_host $1)
lhost=$(ssh -F $config -G $host | grep -w hostname | cut -d' ' -f2)
[[ $lhost ]] && echo $lhost || echo $host
}

parse_host () {
   # usage: parse_host <user/host> 
   # returns extracted host if passed user@host
   # otherwise return value passed
   [[ $1 =~ "@" ]] && { echo $(sed 's/.*@\(.*\)/\1/' <<< "$1");return 0; } 
  echo $1
  return 1
}

parse_user () {
   # usage: parse_user <user/host> 
   # returns extracted user if passed user@host
   # otherwise returns nothing
   # return 1 no user in string
   [[ $1 =~ "@" ]] && { echo $(sed 's/\(.*\)@.*/\1/' <<< "$1"); return 0; } || return 1
  }


valid_ip()
{
    # usage: valid_ip  ip
    # check so see if basic format is correct and all subs or numbers, no returns 2
    # then checks if they are 0 to 254, no returns 1
    # otherwise if good returns "true" and 0
    local  ip=$1
    local res

    if [[ $ip =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$ ]]; then
        OIFS=$IFS
        IFS='.'
        ip=($ip)
        IFS=$OIFS
        [[ ${ip[0]} -le 255 && ${ip[1]} -le 255 \
            && ${ip[2]} -le 255 && ${ip[3]} -le 255 ]]
          res=$([ $? == 0 ] && echo true)
          [[ $res ]] && { echo $res;return 0; }
          return 1
        fi
    return 2
}

get_domain() {
    # usage:  get_domain fulldomain
    # returns domain.tld
    # exampe:  get_domain  discuss.mydomain.com => returns mydomain.com
local domain
domain=$(echo $1 | awk -F\. '{print $(NF-1) FS $NF}')
echo "$domain"
}