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//! Defines helper functions for the Request query string

use std::collections::HashMap;

use crate::helpers::http::{form_url_decode, FormUrlDecoded};

/// Provides a mapping of keys from `Request` query string to their supplied values
pub(crate) type QueryStringMapping = HashMap<String, Vec<FormUrlDecoded>>;

/// Splits a query string into pairs and provides a mapping of keys to values.
///
/// For keys which are represented 1..n times in the query string the mapped `Vec` will be
/// populated with each value provided.
///
/// Keys that are provided but with no value associated are skipped.
pub(crate) fn split<'r>(query: Option<&'r str>) -> QueryStringMapping {
    let mut query_string_mapping = QueryStringMapping::new();

    if let Some(query) = query {
        let pairs = query.split(is_separator).filter(|pair| pair.contains('='));

        for p in pairs {
            let mut sp = p.splitn(2, '=');
            let (k, v) = (sp.next().unwrap(), sp.next().unwrap());

            if let Ok(k) = form_url_decode(k) {
                let vec = query_string_mapping.entry(k).or_insert_with(Vec::new);
                if let Some(dv) = FormUrlDecoded::new(v) {
                    vec.push(dv);
                }
            };
        }
    }

    query_string_mapping
}

fn is_separator(c: char) -> bool {
    c == '&' || c == ';'
}

#[cfg(test)]
mod tests {
    use super::*;

    fn to_pairs<'a>(qsm: &'a QueryStringMapping) -> Vec<(&'a str, Vec<&'a str>)> {
        let mut pairs: Vec<(&str, Vec<&str>)> = qsm
            .iter()
            .map(|(k, v)| {
                let mut values: Vec<&str> = v.iter().map(AsRef::as_ref).collect();
                values.sort_unstable();

                (k.as_str(), values)
            })
            .collect();

        pairs.sort_by(|&(ref a, ref _a_val), &(ref b, ref _b_val)| a.cmp(b));
        pairs
    }

    #[test]
    fn query_string_mapping_tests() {
        let qsm = split(Some("a=b&c=d&e=f"));
        assert_eq!(
            to_pairs(&qsm),
            vec![("a", vec!["b"]), ("c", vec!["d"]), ("e", vec!["f"])],
        );

        let qsm = split(Some("a=b&a=d&e=f"));
        assert_eq!(
            to_pairs(&qsm),
            vec![("a", vec!["b", "d"]), ("e", vec!["f"])],
        );

        let qsm = split(Some("a&b"));
        assert_eq!(to_pairs(&qsm), vec![],);

        let qsm = split(Some("a=b;c=d&e=f"));
        assert_eq!(
            to_pairs(&qsm),
            vec![("a", vec!["b"]), ("c", vec!["d"]), ("e", vec!["f"])],
        );

        let qsm = split(Some("a=b=c&d=e"));
        assert_eq!(to_pairs(&qsm), vec![("a", vec!["b=c"]), ("d", vec!["e"])],);
    }
}