#!/bin/sh

showHelp() {
    cat <<EOF
NAME
    spfgenerator generate SPF DNS entry

SYNOPSIS
    spfgenerator [-h] [-s] [-mx] [-a [domain]] [-i domain] [-p fail|soft|neutral] [-d domain]

DESCRIPTION
    spfgenerator generates SPF DNS entry

    -h, --help
        show this help.

    -mx
        Allow servers listed as MX to send email for the domain.

    -ip <ip>
        Allow IP to send email for the domain.
        Can be used several times.

    -i, --include <domain>
        Any domains that may deliver or relay mail for the domain.
        Can be used several times.

    -a <domain>
        Add any other server hostname that may deliver or relay mail for the domain.
        If domain is empty, it allow current IP address of the domain to send email for the domain.
        Can be used several times.

    -p, --policy <fail|soft|neutral
        How strict should be the servers treating the emails

        neutral:
            Mails will be probably accepted
            Default value.

        fail:
            Not compliant will be rejected

        soft:
            Not compliant will be accepted but marked

    -d,  --domain <domain>
        Default value: @

    -s, --short
        Only show the value
EOF
}

MX=0
IPv4s=
IPv6s=
INCLUDEs=
POLICY='?all'
DOMAIN=@
SHORT=0
As=

testData() {
    if [ -z "$1" ]; then
        (
            echo "Invalid parameter ($2)\n"
            showHelp
        ) >&2
        exit 1
    fi
}

addIp() {
    if [ -n "$1" ]; then
        if [ $(echo "$1" | egrep "^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+") ]; then
            IPv4s="$IPv4s ip4:$1"
        else
            IPv6s="$IPv6s ip6:$1"
        fi
    fi
}

addA() {
    if [ -z "$1" ]; then
        As="$As a"
    else
        As="$As a:$1"
    fi
}

addInclude() {
    if [ -n "$1" ]; then
        INCLUDEs="$INCLUDEs include:$1"
    fi
}

for i in $@; do
    case $1 in
        -h|--help)
            showHelp
            exit 0
            ;;
        -mx)
            MX=1
            shift
            ;;
        -s|--short)
            SHORT=1
            shift
            ;;
        -a)
            shift
            addA $1
            shift
            ;;
        -ip)
            shift
            addIp $1
            shift
            ;;
        -i|--include)
            shift
            addInclude $1
            shift
            ;;
        -p|--policy)
            shift
                case $1 in
                    neutral) POLICY='?all';;
                    soft) POLICY='~all';;
                    fail) POLICY='-all';;
                esac
            shift
            ;;
        -d|--domain)
            shift
            DOMAIN=$1
            shift
            ;;
    esac
done

testData "$DOMAIN" domain
testData "$IPv4s$IPv6s" ip

(
    if [ $MX -eq 1 ]; then
        MX=mx
    fi

    if [ $SHORT -eq 0 ]; then
        echo "$DOMAIN	IN	TXT	\"v=spf1 $MX $As $IPv4s $IPv6s $INCLUDEs $POLICY\""
    else
        echo "v=spf1 $MX $As $IPv4s $IPv6s $INCLUDEs $POLICY"
    fi
) | sed 's/  */ /g'