afire 2.2.1

//! Utilities for encoding and decoding strings.
//! Currently only supports url encoding.

/// Decode a url encoded string.
/// Supports `+` and `%` encoding.
/// If the decode fails for any reason, [`None`] is returned.
pub fn decode(url: &str) -> Option<String> {
    let mut chars = url.chars();
    let mut out = String::with_capacity(url.len());

    while let Some(i) = chars.next() {
        match i {
            '+' => out.push(' '),
            '%' => {
                let mut hex = String::new();
                hex.push(chars.next()?);
                hex.push(chars.next()?);
                out.push(u8::from_str_radix(&hex, 16).ok()? as char);
            }
            _ => out.push(i),
        }
    }

    Some(out)
}

/// Encodes a string with url encoding.
/// Uses `%20` for spaces not `+`.
/// Allowed characters are `A-Z`, `a-z`, `0-9`, `-`, `.`, `_` and `~`.
pub fn encode(url: &str) -> String {
    const ALLOWED_CHARS: &[u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZ\
                                   abcdefghijklmnopqrstuvwxyz\
                                   0123456789-._~";

    let mut out = String::with_capacity(url.len());

    for i in url.chars() {
        if i.is_ascii() && ALLOWED_CHARS.contains(&(i as u8)) {
            out.push(i);
            continue;
        }
        out.push_str(&format!("%{:02X}", i as u8));
    }

    out
}

#[cfg(test)]
mod test {
    use super::{decode, encode};

    #[test]
    fn test_url_decode() {
        assert_eq!(decode("hello+world").unwrap(), "hello world");
        assert_eq!(decode("hello%20world").unwrap(), "hello world");
        assert_eq!(
            decode("%3C%3E%22%23%25%7B%7D%7C%5C%5E~%5B%5D%60").unwrap(),
            "<>\"#%{}|\\^~[]`"
        );
    }

    #[test]
    fn test_url_decode_fail() {
        assert_eq!(decode("hello%20world%"), None);
        assert_eq!(decode("hello%20world%2"), None);
        assert_eq!(decode("hello%20world%2G"), None);
    }

    #[test]
    fn test_url_encode() {
        assert_eq!(encode("hello world"), "hello%20world");
        assert_eq!(encode("hello%20world"), "hello%2520world");
        assert_eq!(
            encode("<>\"#%{}|\\^~[]`"),
            "%3C%3E%22%23%25%7B%7D%7C%5C%5E~%5B%5D%60"
        );
    }
}