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extern crate regex;
macro_rules! regex(
($s:expr) => (regex::Regex::new($s).unwrap());
);
fn convert_one_sort_str_field_to_sql(sort_str: &str) -> Option<String> {
let sort_str_format = regex!(
r"^(?P<order>[+-]?)(?P<field>[a-zA-Z0-9_\.]+)(?P<nulls>[-]?)$"
);
let fields = match sort_str_format.captures(sort_str) {
Some(captures) => captures,
None => return None,
};
let field = match fields.name("field") {
Some(f) => f,
None => return None,
};
let order = match fields.name("order") {
Some("-") => "DESC",
_ => "ASC",
};
let nulls = match fields.name("nulls") {
Some("-") => "NULLS FIRST",
_ => "NULLS LAST",
};
let sql = format!("{} {} {}", field, order, nulls);
return Some(sql);
}
pub fn sort_str_to_sql(sort_str: &str) -> Option<String> {
let sql_array: Vec<String> = sort_str.split(',')
.filter_map(convert_one_sort_str_field_to_sql)
.collect();
let sql = sql_array.connect(", ");
return if sql == "" { None } else { Some(sql) };
}