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//! Parse SQL "`LIKE`"-like filters.
/// matches % as a wildcard operator
pub struct Wildcard {
w: String,
}
impl Wildcard {
/// Parse a wildcard filter. All strings are valid, so never fails.
pub fn new(w: &str) -> Wildcard {
Wildcard { w: w.to_owned() }
}
/// Returns the shortest possible fixed prefix.
///
/// If no "%" is in the filter, then the entire string is returned,
/// Otherwise everything up to the "%" is returned, which may
/// be an empty string.
pub fn prefix(&self) -> &str {
if let Some(o) = self.w.find('%') {
&self.w[0..o]
} else {
&self.w[..]
}
}
/// returns true if this search can only match a single key.
///
/// This only happens when there is no "%" in the filter.
pub fn is_exact(&self) -> bool {
self.w.find('%').is_none()
}
/// Returns the regex that matches my wildcard.
///
/// Returns None if the prefix is all that's needed, even
/// if it's still a wildcard.
///
/// "prefix%suffix" returns `Some` but `prefix%` returns
/// `None`.
pub fn as_regex(&self) -> Option<regex::Regex> {
let mut re = String::with_capacity(self.w.len() + 4);
re += "^";
let mut haspct = false;
let mut needre = false;
for c in self.w.chars() {
if haspct {
needre = true;
}
match c {
'%' => {
re += ".*";
haspct = true;
}
a @ '.'
| a @ '('
| a @ ')'
| a @ '{'
| a @ '}'
| a @ '\\'
| a @ '|'
| a @ '^'
| a @ '$'
| a @ '['
| a @ ']' => {
re.push('\\');
re.push(a);
}
a => re.push(a),
}
}
re += "$";
if needre || !haspct {
Some(regex::Regex::new(&re).unwrap())
} else {
None
}
}
}