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#!/bin/bash -
# Print a country's IPv4 prefixes in CIDR notation to standard output
# Version 3.0
# Written by Bernard Lim <bernard.lim@sands.com>

AUTHOR="Bernard Lim <lim.yiok.kia@gmail.com>"
VERSION="3.0"
PROG=$(basename $0)

# default: CC to IP blocks
ACTION=cc2ip

# fanciful output
b="\033[1m"  # bold
u="\033[4m"  # underline
o="\033[0m"  # off

# clean up upon EXIT
clean() {
  rm /tmp/*.xargs &>/dev/null
}
trap "clean" EXIT

# dependency message
depends() {
  echo "$PROG: depends on \`$*'" >&2
  echo "Install \`$*' and try again." >&2
  exit 1
}

# die a graceful death!
die() {
  echo "$PROG: $*" >&2
  echo "Try \`$PROG -h' for more information" >&2
  exit 1
}

# shorter usage
short() {
  usage | sed 2q
  echo "Try \`$PROG -h' for more information"
}

# usage
usage() {
cat <<EOF
Usage: $PROG [OPTION]... [CC]... (2-letter country code)
Print CC's IPv4 prefixes in CIDR notation to standard output.

$(echo -e ${b}Options${o})
  -a            Print ASN's IPv4 prefixes and exit
  -c            Print CC's ASNs and exit
  -h            Display this help and exit
  -p n          Run n processes in parallel (default n=64)
  -v            Show version information and exit

$PROG uses ISO 3166-1 alpha-2 codes to represent country.
They are 2-letter country codes used widely to represent
countries, dependent territories and special areas of
geographical interest. Examples: SG for Singapore or
US for United States.

When CC is -, read standard input. This can be useful if you
$(echo -ne ${b}cat${o})(1) a list of country codes to $PROG for bulk operations.

$(echo -e ${b}Examples${o})
  $PROG SG          # Print Singapore's IPv4 prefixes (fast)
  $PROG US          # Print United States' IPv4 prefixes (slow)
  $PROG -p 100 SG   # Same but run 100 processes in parallel
  $PROG -a AS668    # Print IPv4 prefixes originating from AS668
  $PROG -c SG       # Print ASNs originating from SG

Report $PROG bugs to $AUTHOR
This software is distributed in the hope that it will be
useful but without any warranty. It is provided "as is".
EOF
}

# ASN to IP prefixes
asn2ip() {
  if which whois &>/dev/null; then
    local asn=$1
    validate_asn $asn

    if [[ -z "$asn" || "$asn" == "-" ]]; then
      cat -
    else
      cat - <<<"$asn"
    fi | \
    $PARALLEL sh -c 'whois -h whois.radb.net !g"{}" > /tmp/"{}".xargs' 2>/dev/null

    # awk to the rescue again
    cat /tmp/*.xargs |
    awk '\
      BEGIN { RS = "(A[0-9]+|[CD])\n?"; FS = " "; }
            { for (i = 1; i <= NF; i++) print $i  }' |
    tr -d "\n" |
    sed -r 's/(\/([0-9]|1[0-9]|2[0-9]|3[0-2]))/\1\n/g' |
    sort -t. -n -k1,1 -k2,2 -k3,3 -k4,4 |
    uniq -c |
    awk '{ print $NF }'
  else
    depends "whois"
  fi
}

# CC to ASN
cc2asn() {
  if which curl &>/dev/null; then
    local cc=$(tr 'a-z' 'A-Z' <<<"$1"); validate_cc $cc
    local ua="Mozilla/5.0"
    local url="https://bgp.he.net/country"

    if [[ -z "$cc" || "$cc" == "-" ]]; then
      cat -
    else
      cat - <<<"$cc"
    fi |
    ($PARALLEL curl -sk -A "$ua" "$url/{}" | grep -Eo 'AS[0-9]+' &) |
    uniq -c |
    awk '{ print $NF }' |
    tr -d 'AS' |
    sort -n |
    sed 's/^/AS/'
  else
    depends "curl"
  fi
}

# CC to IP prefixes
cc2ip() {
  if which curl &>/dev/null; then
    local cc=$(tr 'a-z' 'A-Z' <<<"$1")
    validate_cc $cc

    if [[ -z "$cc" || "$cc" == "-" ]]; then
      cc2asn -
    else
      cc2asn - <<<"$cc"
    fi | asn2ip -
  else
    depends "curl"
  fi
}

# validate ASN
validate_asn() {
  local asn=$1

  # sanity check
  if [ -z "$asn" ]; then
    die "missing argument: [ASN]"
  else
    # format check
    if grep -Ev '^(-?|[aA][sS][0-9]+)$' <<<"$asn" > /dev/null; then
      die "invalid ASN"
    fi
  fi
}

# validate CC
validate_cc() {
  local cc=$1

  # sanity check
  if [ -z "$cc" ]; then
    die "missing argument: [CC]"
  else
    # format check
    if grep -Ev '^(-?|[a-zA-Z]{2})$' <<<"$cc" >/dev/null; then
      die "invalid country code"
    fi
  fi
}

# parse short options
OPTIND=1
while getopts ":achp:v" opt; do
  case $opt in
  a)
    if [[ "$LASTOPT" == "$opt" ]]; then
      die "only one \`-$opt' may be specified"
    fi

    ACTION=asn2ip
    LASTOPT=$opt
    ;;
  c)
    if [[ "$LASTOPT" == "$opt" ]]; then
      die "only one \`$opt' may be specified"
    fi

    ACTION=cc2asn
    LASTOPT=$opt
    ;;
  h)
    if [[ $# -ne 1 || $OPTIND -eq 1 ]]; then short; exit 1; fi
    usage
    exit 0
    ;;
  p)
    if [[ "$LASTOPT" == "$opt" ]]; then
      die "only one \`$opt' may be specified"
    fi

    # validate option argument
    if grep -Ev '^[0-9]+$' &>/dev/null <<<"$OPTARG"; then
      die "invalid option argument -- '$OPTARG'"
      exit 1
    fi

    MAX=$((10#$OPTARG))
    LASTOPT=$opt
    ;;
  v)
    if [[ $# -ne 1 || $OPTIND -eq 1 ]]; then short; exit 1; fi
    echo "$PROG $VERSION"
    echo "Written by $AUTHOR"
    exit 0
    ;;
  :)
    die "option requires an argument -- '$OPTARG'"
    ;;
  \?)
    die "invalid option -- '$OPTARG'"
    ;;
  esac
done;
shift $((OPTIND-1))

# check for empty arguments
if [[ -n "$LASTOPT" && $# -eq 0 ]]; then
  case $LASTOPT in
    a) validate_asn; exit 1;;
    c) validate_cc; exit 1;;
    *) short; exit 1;;
  esac
elif [ $# -eq 0 ]; then
  short
  exit 1
fi

# main
# release the kraken!
PARALLEL="xargs -P${MAX:=64} -I{}"

if [[ -z "$1" || "$1" == "-" ]]; then
  $ACTION -
else
  for i in $*; do $ACTION $i; done
fi