use linked_hash_map::LinkedHashMap;

pub fn parse_query_string(query_string: &str) -> LinkedHashMap<String, Vec<String>> {
    let mut map = LinkedHashMap::new();
    query_string.split('&').for_each(|kv| {
        let mut meet_equal = false;
        let mut k = String::new();
        let mut v = String::new();
        kv.chars().for_each(|c| {
            if meet_equal {
                v.push(c);
            } else if c == '=' {
                meet_equal = true;
            } else {
                k.push(c);
            }
        });
        let k = percent_encoding::percent_decode_str(&k).decode_utf8_lossy().into_owned();
        let v = percent_encoding::percent_decode_str(&v).decode_utf8_lossy().into_owned();
        match map.get_mut(&k) {
            None => { map.insert(k, vec![v]); },
            Some(values) => { values.push(v); },
        }
    });
    map
}

#[test]
fn test_parse_query_string() {
    let mut e = LinkedHashMap::new();
    e.insert("a".to_string(), vec!["b".to_string()]);
    let m = parse_query_string("a=b");
    assert_eq!(e, m);
    let mut e = LinkedHashMap::new();
    e.insert("a".to_string(), vec!["b".to_string(), "c".to_string()]);
    let m = parse_query_string("a=b&a=c");
    assert_eq!(e, m);
}