pct 4.0.1

Percent-encoded strings for URL, URI, IRI, etc.
Documentation 
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use super::Encoder;

/// IRI-reserved characters encoder.
///
/// This [`Encoder`] encodes characters that are reserved in the syntax of IRI
/// according to [RFC 3987](https://tools.ietf.org/html/rfc3987).
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum IriReserved {
    /// Encode characters reserved in any IRI component.
    Any,

    /// Encode characters reserved in a path segment.
    Path,

    /// Encode characters reserved in a query.
    Query,

    /// Encode characters reserved in a fragment.
    Fragment,
}

impl IriReserved {
    fn is_reserved_but_safe(&self, c: char) -> bool {
        match self {
            Self::Any => false,
            Self::Path => is_sub_delim(c) || c == '@',
            Self::Query => is_sub_delim(c) || is_iprivate(c) || matches!(c, ':' | '@' | '/' | '?'),
            Self::Fragment => is_sub_delim(c) || matches!(c, ':' | '@' | '/' | '?'),
        }
    }
}

impl Encoder for IriReserved {
    fn encode(&self, c: char) -> bool {
        !is_iunreserved(c) && !self.is_reserved_but_safe(c)
    }

    #[inline]
    fn encode_ascii(&self, b: u8) -> Option<bool> {
        Some(self.keep_table()[b as usize] == 0)
    }

    #[inline]
    fn ascii_keep_table(&self) -> Option<&'static [u8; 128]> {
        Some(self.keep_table())
    }

    #[inline]
    fn ascii_keep_lo_shuf(&self) -> Option<&'static [u8; 16]> {
        Some(match self {
            Self::Any => &IRI_LO_SHUF_ANY,
            Self::Path => &IRI_LO_SHUF_PATH,
            Self::Query => &IRI_LO_SHUF_QUERY,
            Self::Fragment => &IRI_LO_SHUF_FRAGMENT,
        })
    }
}

impl IriReserved {
    #[inline]
    fn keep_table(&self) -> &'static [u8; 128] {
        // ASCII rules coincide with URI because ucschar / iprivate are
        // strictly non-ASCII.
        match self {
            Self::Any => &IRI_KEEP_ANY,
            Self::Path => &IRI_KEEP_PATH,
            Self::Query => &IRI_KEEP_QUERY,
            Self::Fragment => &IRI_KEEP_FRAGMENT,
        }
    }
}

fn is_sub_delim(c: char) -> bool {
    matches!(c, '!' | '$' | '&' | '\'' | '(' | ')' | '*' | '+' | ',' | ';' | '=')
}

fn is_iprivate(c: char) -> bool {
    matches!(c, '\u{E000}'..='\u{F8FF}' | '\u{F0000}'..='\u{FFFFD}' | '\u{100000}'..='\u{10FFFD}')
}

fn is_iunreserved(c: char) -> bool {
    c.is_ascii_alphanumeric() || matches!(c, '-' | '.' | '_' | '~') || is_ucschar(c)
}

fn is_ucschar(c: char) -> bool {
    matches!(c,
          '\u{00A0}'..='\u{0D7FF}'
        | '\u{F900}'..='\u{FDCF}'
        | '\u{FDF0}'..='\u{FFEF}'
        | '\u{10000}'..='\u{1FFFD}'
        | '\u{20000}'..='\u{2FFFD}'
        | '\u{30000}'..='\u{3FFFD}'
        | '\u{40000}'..='\u{4FFFD}'
        | '\u{50000}'..='\u{5FFFD}'
        | '\u{60000}'..='\u{6FFFD}'
        | '\u{70000}'..='\u{7FFFD}'
        | '\u{80000}'..='\u{8FFFD}'
        | '\u{90000}'..='\u{9FFFD}'
        | '\u{A0000}'..='\u{AFFFD}'
        | '\u{B0000}'..='\u{BFFFD}'
        | '\u{C0000}'..='\u{CFFFD}'
        | '\u{D0000}'..='\u{DFFFD}'
        | '\u{E1000}'..='\u{EFFFD}'
    )
}

const fn build_keep_table(variant: u8) -> [u8; 128] {
    let mut t = [0u8; 128];
    let mut i = 0u16;
    while i < 128 {
        let b = i as u8;
        let unreserved = matches!(
            b,
            b'A'..=b'Z'
            | b'a'..=b'z'
            | b'0'..=b'9'
            | b'-'
            | b'.'
            | b'_'
            | b'~'
        );
        let sub_delim = matches!(b, b'!' | b'$' | b'&' | b'\'' | b'(' | b')' | b'*' | b'+' | b',' | b';' | b'=');
        let safe = match variant {
            0 => false,                                                   // Any
            1 => sub_delim || b == b'@',                                  // Path
            2 | 3 => sub_delim || matches!(b, b':' | b'@' | b'/' | b'?'), // Query/Fragment
            _ => false,
        };
        let keep = unreserved || safe;
        t[i as usize] = if keep && b != b'%' { 1 } else { 0 };
        i += 1;
    }
    t
}

pub(crate) static IRI_KEEP_ANY: [u8; 128] = build_keep_table(0);
pub(crate) static IRI_KEEP_PATH: [u8; 128] = build_keep_table(1);
pub(crate) static IRI_KEEP_QUERY: [u8; 128] = build_keep_table(2);
pub(crate) static IRI_KEEP_FRAGMENT: [u8; 128] = build_keep_table(3);

pub(crate) static IRI_LO_SHUF_ANY: [u8; 16] = crate::scan::build_lo_shuf(&IRI_KEEP_ANY);
pub(crate) static IRI_LO_SHUF_PATH: [u8; 16] = crate::scan::build_lo_shuf(&IRI_KEEP_PATH);
pub(crate) static IRI_LO_SHUF_QUERY: [u8; 16] = crate::scan::build_lo_shuf(&IRI_KEEP_QUERY);
pub(crate) static IRI_LO_SHUF_FRAGMENT: [u8; 16] = crate::scan::build_lo_shuf(&IRI_KEEP_FRAGMENT);

#[cfg(test)]
mod tests {
    use crate::PctString;

    use super::*;

    #[test]
    fn iri_encode_cyrillic() {
        let encoder = IriReserved::Path;
        let pct_string = PctString::encode("традиционное польское блюдо".chars(), encoder);
        assert_eq!(&pct_string, &"традиционное польское блюдо");
        assert_eq!(&pct_string.as_str(), &"традиционное%20польское%20блюдо");
    }

    #[test]
    fn iri_encode_segment() {
        let encoder = IriReserved::Path;
        let pct_string = PctString::encode("?test=традиционное польское блюдо&cjk=真正&private=\u{10FFFD}".chars(), encoder);

        assert_eq!(&pct_string, &"?test=традиционное польское блюдо&cjk=真正&private=\u{10FFFD}");
        assert_eq!(&pct_string.as_str(), &"%3Ftest=традиционное%20польское%20блюдо&cjk=真正&private=%F4%8F%BF%BD");
    }

    #[test]
    fn iri_encode_segment_nocolon() {
        let encoder = IriReserved::Path;
        let pct_string = PctString::encode("?test=традиционное польское блюдо&cjk=真正&private=\u{10FFFD}".chars(), encoder);
        assert_eq!(&pct_string, &"?test=традиционное польское блюдо&cjk=真正&private=\u{10FFFD}");
        assert_eq!(&pct_string.as_str(), &"%3Ftest=традиционное%20польское%20блюдо&cjk=真正&private=%F4%8F%BF%BD");
    }

    #[test]
    fn iri_encode_fragment() {
        let encoder = IriReserved::Fragment;
        let pct_string = PctString::encode("?test=традиционное польское блюдо&cjk=真正&private=\u{10FFFD}".chars(), encoder);
        assert_eq!(&pct_string, &"?test=традиционное польское блюдо&cjk=真正&private=\u{10FFFD}");
        assert_eq!(&pct_string.as_str(), &"?test=традиционное%20польское%20блюдо&cjk=真正&private=%F4%8F%BF%BD");
    }

    #[test]
    fn iri_encode_query() {
        let encoder = IriReserved::Query;
        let pct_string = PctString::encode("?test=традиционное польское блюдо&cjk=真正&private=\u{10FFFD}".chars(), encoder);
        assert_eq!(&pct_string, &"?test=традиционное польское блюдо&cjk=真正&private=\u{10FFFD}");
        assert_eq!(&pct_string.as_str(), &"?test=традиционное%20польское%20блюдо&cjk=真正&private=\u{10FFFD}");
    }

    #[test]
    fn keep_table_matches_encode() {
        for variant in [IriReserved::Any, IriReserved::Path, IriReserved::Query, IriReserved::Fragment] {
            for b in 0u8..128 {
                let from_table = variant.ascii_keep_table().unwrap()[b as usize] != 0;
                let from_encode = !variant.encode(b as char);
                let expected = from_encode && b != b'%';
                assert_eq!(from_table, expected, "variant {:?} byte {:#x}", variant, b);
            }
        }
    }
}