fn find_subject()

in components/suggest/src/yelp.rs [275:340]
57 lines of code
11 McCabe index (conditional complexity)

    fn find_subject<'a>(
        &self,
        query_words: &'a [&'a str],
    ) -> Result<Option<(String, bool, &'a [&'a str])>> {
        if query_words.is_empty() {
            return Ok(None);
        }

        let mut query_string = query_words.join(" ");

        // This checks if keyword is a substring of the query.
        if let Some(keyword_lowercase) = self.conn.try_query_one::<String, _>(
            "SELECT keyword
             FROM yelp_subjects
             WHERE :query BETWEEN keyword AND keyword || ' ' || x'FFFF'
             ORDER BY LENGTH(keyword) ASC, keyword ASC
             LIMIT 1",
            named_params! {
                ":query": query_string.to_lowercase(),
            },
            true,
        )? {
            // Preserve the query as the user typed it including its case.
            return Ok(query_string.get(0..keyword_lowercase.len()).map(|keyword| {
                let count = keyword.split_whitespace().count();
                (
                    keyword.to_string(),
                    true,
                    query_words.get(count..).unwrap_or_default(),
                )
            }));
        };

        if query_string.len() < SUBJECT_PREFIX_MATCH_THRESHOLD {
            return Ok(None);
        }

        // Oppositely, this checks if the query is a substring of keyword.
        if let Some(keyword_lowercase) = self.conn.try_query_one::<String, _>(
            "SELECT keyword
             FROM yelp_subjects
             WHERE keyword BETWEEN :query AND :query || x'FFFF'
             ORDER BY LENGTH(keyword) ASC, keyword ASC
             LIMIT 1",
            named_params! {
                ":query": query_string.to_lowercase(),
            },
            true,
        )? {
            // Preserve the query as the user typed it including its case.
            return Ok(keyword_lowercase
                .get(query_string.len()..)
                .map(|keyword_rest| {
                    query_string.push_str(keyword_rest);
                    let count =
                        std::cmp::min(query_words.len(), query_string.split_whitespace().count());
                    (
                        query_string,
                        false,
                        query_words.get(count..).unwrap_or_default(),
                    )
                }));
        };

        Ok(None)
    }