#!/usr/bin/env bash

isDateInvalid()
{
    DATE="${1}"

    # Autorized separator char ['space', '/', '.', '_', '-']
    SEPAR="([ \/._-])?"

    # Date format day[01..31], month[01,03,05,07,08,10,12], year[1900..2099]
    DATE_1="((([123][0]|[012][1-9])|3[1])${SEPAR}(0[13578]|1[02])${SEPAR}(19|20)[0-9][0-9])"

    # Date format day[01..30], month[04,06,09,11], year[1900..2099]
    DATE_2="(([123][0]|[012][1-9])${SEPAR}(0[469]|11)${SEPAR}(19|20)[0-9][0-9])"

    # Date format day[01..28], month[02], year[1900..2099]
    DATE_3="(([12][0]|[01][1-9]|2[1-8])${SEPAR}02${SEPAR}(19|20)[0-9][0-9])"

    # Date format day[29], month[02], year[1904..2096]
    DATE_4="(29${SEPAR}02${SEPAR}(19|20(0[48]|[2468][048]|[13579][26])))"

    # Date 29.02.2000
    DATE_5="(29${SEPAR}02${SEPAR}2000)"

    # Match the date in the Regex

    #if ! [[ "${DATE}" =~ ^(${DATE_1}|${DATE_2}|${DATE_3}|${DATE_4})$ ]]
    #then
    #    echo -e "ERROR - '${DATE}' invalid!"
    #else
    #    echo "${DATE} is valid"
    #fi

    if [[ "${DATE}" =~ ^(${DATE_1}|${DATE_2}|${DATE_3}|${DATE_4}|${DATE_5})$ ]] ; then
      return 1
    else
      return 0
   fi
}

echo
if  isDateInvalid "${1}" ; then
   echo "inavalid Date: ${1}"
else
   echo "${1} is valid."
fi
echo

exit 0