#!/bin/sh
set -e
set -u

g_csv="${1:-}"
g_dir=$(dirname "${g_csv}")
g_rnd="${g_csv}"
g_rnd=$(basename "${g_rnd}" ".csv")
g_rnd="${g_dir}/${g_rnd}.rnd.csv"

fn_help() {
   echo "USAGE"
   echo "   # sort -R ./list.csv > ./list.rnd.csv"
   echo "   ./randomize-csv ./list.csv"
}

main() {
   if test -z "${g_csv}" || ! test -s "${g_csv}"; then
      >&2 fn_help
      return 1
   fi

   if test -s "${g_rnd}"; then
      {
         echo "${g_rnd} already exists"
      } >&2
      return 1
   fi

   head -n 1 "${g_csv}" > "${g_rnd}"
   tail -n +2 "${g_csv}" | sort -R >> "${g_rnd}"
   {
      echo "wrote ${g_rnd}"
   } >&2
}

main