--- /dev/null
+//! Levenshtein distances.
+//!
+//! The [Levenshtein distance] is a metric for measuring the difference between two strings.
+//!
+//! [Levenshtein distance]: https://en.wikipedia.org/wiki/Levenshtein_distance
+
+use crate::symbol::Symbol;
+use std::cmp;
+
+#[cfg(test)]
+mod tests;
+
+/// Finds the Levenshtein distance between two strings.
+pub fn lev_distance(a: &str, b: &str) -> usize {
+ // cases which don't require further computation
+ if a.is_empty() {
+ return b.chars().count();
+ } else if b.is_empty() {
+ return a.chars().count();
+ }
+
+ let mut dcol: Vec<_> = (0..=b.len()).collect();
+ let mut t_last = 0;
+
+ for (i, sc) in a.chars().enumerate() {
+ let mut current = i;
+ dcol[0] = current + 1;
+
+ for (j, tc) in b.chars().enumerate() {
+ let next = dcol[j + 1];
+ if sc == tc {
+ dcol[j + 1] = current;
+ } else {
+ dcol[j + 1] = cmp::min(current, next);
+ dcol[j + 1] = cmp::min(dcol[j + 1], dcol[j]) + 1;
+ }
+ current = next;
+ t_last = j;
+ }
+ }
+ dcol[t_last + 1]
+}
+
+/// Finds the best match for a given word in the given iterator.
+///
+/// As a loose rule to avoid the obviously incorrect suggestions, it takes
+/// an optional limit for the maximum allowable edit distance, which defaults
+/// to one-third of the given word.
+///
+/// Besides Levenshtein, we use case insensitive comparison to improve accuracy
+/// on an edge case with a lower(upper)case letters mismatch.
+#[cold]
+pub fn find_best_match_for_name(
+ name_vec: &[Symbol],
+ lookup: Symbol,
+ dist: Option<usize>,
+) -> Option<Symbol> {
+ let lookup = &lookup.as_str();
+ let max_dist = dist.unwrap_or_else(|| cmp::max(lookup.len(), 3) / 3);
+
+ let (case_insensitive_match, levenshtein_match) = name_vec
+ .iter()
+ .filter_map(|&name| {
+ let dist = lev_distance(lookup, &name.as_str());
+ if dist <= max_dist { Some((name, dist)) } else { None }
+ })
+ // Here we are collecting the next structure:
+ // (case_insensitive_match, (levenshtein_match, levenshtein_distance))
+ .fold((None, None), |result, (candidate, dist)| {
+ (
+ if candidate.as_str().to_uppercase() == lookup.to_uppercase() {
+ Some(candidate)
+ } else {
+ result.0
+ },
+ match result.1 {
+ None => Some((candidate, dist)),
+ Some((c, d)) => Some(if dist < d { (candidate, dist) } else { (c, d) }),
+ },
+ )
+ });
+ // Priority of matches:
+ // 1. Exact case insensitive match
+ // 2. Levenshtein distance match
+ // 3. Sorted word match
+ if let Some(candidate) = case_insensitive_match {
+ Some(candidate)
+ } else if levenshtein_match.is_some() {
+ levenshtein_match.map(|(candidate, _)| candidate)
+ } else {
+ find_match_by_sorted_words(name_vec, lookup)
+ }
+}
+
+fn find_match_by_sorted_words(iter_names: &[Symbol], lookup: &str) -> Option<Symbol> {
+ iter_names.iter().fold(None, |result, candidate| {
+ if sort_by_words(&candidate.as_str()) == sort_by_words(lookup) {
+ Some(*candidate)
+ } else {
+ result
+ }
+ })
+}
+
+fn sort_by_words(name: &str) -> String {
+ let mut split_words: Vec<&str> = name.split('_').collect();
+ // We are sorting primitive &strs and can use unstable sort here.
+ split_words.sort_unstable();
+ split_words.join("_")
+}