pub fn lookup_format(name: &str) -> Option<&str> {
let r = match name {
"date-time" => concat!(
r"^(?P<date>",
r"[0-9]{4}-(?:",
r"(?:0[13578]|1[02])-(?:0[1-9]|[12][0-9]|3[01])|", // 31-day months
r"(?:0[469]|11)-(?:0[1-9]|[12][0-9]|30)|", // 30-day months
r"(?:02)-(?:0[1-9]|1[0-9]|2[0-9])", // February up to 29 days
r"))",
r"[tT](?P<time>",
r"(?:[01][0-9]|2[0-3]):[0-5][0-9]:", // Hours, Minutes
r"(?:[0-5][0-9]|60)", // Seconds (including leap second 60)
r"(?P<time_fraction>\.[0-9]+)?", // Optional fractional seconds
r"(?P<time_zone>",
r"[zZ]|[+-](?:[01][0-9]|2[0-3]):[0-5][0-9]", // Time zone
r")",
r")$"
),
"time" => {
r"^(?:[01][0-9]|2[0-3]):[0-5][0-9]:(?:[0-5][0-9]|60)(?P<time_fraction>\.[0-9]+)?(?P<time_zone>[zZ]|[+-](?:[01][0-9]|2[0-3]):[0-5][0-9])$"
}
"date" => concat!(
r"^(?:",
r"(?:[0-9]{4}-(?:0[13578]|1[02])-(?:0[1-9]|[12][0-9]|3[01]))|", // Months with 31 days
r"(?:[0-9]{4}-(?:0[469]|11)-(?:0[1-9]|[12][0-9]|30))|", // Months with 30 days
r"(?:[0-9]{4}-02-(?:0[1-9]|1[0-9]|2[0-9]))", // February with up to 29 days
r")$"
),
"duration" => {
r"^P(?:(?P<dur_date>(?:(?P<dur_year>[0-9]+Y(?:[0-9]+M(?:[0-9]+D)?)?)|(?P<dur_month>[0-9]+M(?:[0-9]+D)?)|(?P<dur_day>[0-9]+D))(?:T(?:(?P<dur_hour>[0-9]+H(?:[0-9]+M(?:[0-9]+S)?)?)|(?P<dur_minute>[0-9]+M(?:[0-9]+S)?)|(?P<dur_second>[0-9]+S)))?)|(?P<dur_time>T(?:(?P<dur_hour2>[0-9]+H(?:[0-9]+M(?:[0-9]+S)?)?)|(?P<dur_minute2>[0-9]+M(?:[0-9]+S)?)|(?P<dur_second2>[0-9]+S)))|(?P<dur_week>[0-9]+W))$"
}
"email" => {
r"^(?P<local_part>(?P<dot_string>[^\s@\.]+(\.[^\s@\.]+)*))@((?P<domain>(?P<sub_domain>[a-zA-Z0-9]([a-zA-Z0-9-]*[a-zA-Z0-9])?)(\.(?P<sub_domain2>[a-zA-Z0-9]([a-zA-Z0-9-]*[a-zA-Z0-9])?))*)|\[(?P<ipv4>((([0-9])|(([1-9])[0-9]|(25[0-5]|(2[0-4]|(1)[0-9])[0-9])))\.){3}(([0-9])|(([1-9])[0-9]|(25[0-5]|(2[0-4]|(1)[0-9])[0-9]))))\])$"
}
"hostname" => {
r"^[a-zA-Z0-9]([a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(\.[a-zA-Z0-9]([a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$"
}
"ipv4" => {
r"^((([0-9])|(([1-9])[0-9]|(25[0-5]|(2[0-4]|(1)[0-9])[0-9])))\.){3}(([0-9])|(([1-9])[0-9]|(25[0-5]|(2[0-4]|(1)[0-9])[0-9])))$"
}
"ipv6" => {
r"^(?:(?P<full>(?:[0-9a-fA-F]{1,4}:){7}[0-9a-fA-F]{1,4}))|(?:::(?:[0-9a-fA-F]{1,4}:){0,5}(?P<ls32>[0-9a-fA-F]{1,4}:[0-9a-fA-F]{1,4}))|(?:(?P<h16_1>[0-9a-fA-F]{1,4})?::(?:[0-9a-fA-F]{1,4}:){0,4}(?P<ls32_1>[0-9a-fA-F]{1,4}:[0-9a-fA-F]{1,4}))|(?:((?:[0-9a-fA-F]{1,4}:){0,1}[0-9a-fA-F]{1,4})?::(?:[0-9a-fA-F]{1,4}:){0,3}(?P<ls32_2>[0-9a-fA-F]{1,4}:[0-9a-fA-F]{1,4}))|(?:((?:[0-9a-fA-F]{1,4}:){0,2}[0-9a-fA-F]{1,4})?::(?:[0-9a-fA-F]{1,4}:){0,2}(?P<ls32_3>[0-9a-fA-F]{1,4}:[0-9a-fA-F]{1,4}))|(?:((?:[0-9a-fA-F]{1,4}:){0,3}[0-9a-fA-F]{1,4})?::[0-9a-fA-F]{1,4}:(?P<ls32_4>[0-9a-fA-F]{1,4}:[0-9a-fA-F]{1,4}))|(?:((?:[0-9a-fA-F]{1,4}:){0,4}[0-9a-fA-F]{1,4})?::(?P<ls32_5>[0-9a-fA-F]{1,4}:[0-9a-fA-F]{1,4}))|(?:((?:[0-9a-fA-F]{1,4}:){0,5}[0-9a-fA-F]{1,4})?::(?P<h16_2>[0-9a-fA-F]{1,4}))|(?:((?:[0-9a-fA-F]{1,4}:){0,6}[0-9a-fA-F]{1,4})?::)$"
}
"uuid" => {
r"^(?P<time_low>[0-9a-fA-F]{8})-(?P<time_mid>[0-9a-fA-F]{4})-(?P<time_high_and_version>[0-9a-fA-F]{4})-(?P<clock_seq_and_reserved>[0-9a-fA-F]{2})(?P<clock_seq_low>[0-9a-fA-F]{2})-(?P<node>[0-9a-fA-F]{12})$"
}
"unknown" => r"^(?s:.*)$",
_ => return None,
};
Some(r)
}