nonymous 0.7.0

use core::fmt::{self, Formatter, Write};

use crate::core::r#const::{CLASS, OPCODE, RCODE, TYPE};
use crate::core::{Class, Opcode, Rcode, Serial, Ttl, Type};
use crate::rdata::view::{
    Aaaa, Caa, CaaTag, CaaValue, Cname, Malformed, Mx, Ns, Ptr, Soa, Txt, Unknown, A,
};
use crate::view::{
    BorrowedView, CharacterString, Extension, Header, Label, Message, Name, Question, Record,
};

pub trait Format {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result;
}

impl fmt::Write for Wrapper<'_, '_> {
    fn write_str(&mut self, s: &str) -> fmt::Result {
        (self.f)(self.i, &mut self.p, s)
    }
}

pub type Writer = dyn Fn(&mut dyn fmt::Write, &mut Position, &str) -> fmt::Result;

fn plain(w: &mut dyn fmt::Write, _: &mut Position, s: &str) -> fmt::Result {
    w.write_str(s)
}

pub struct Wrapper<'i, 'f> {
    i: &'i mut dyn fmt::Write,
    p: Position,
    f: &'f Writer,
}

impl<'i, 'f> Wrapper<'i, 'f> {
    pub fn plain(i: &'i mut dyn fmt::Write) -> Self {
        Self::with_writer(i, &plain)
    }
    pub fn with_writer(i: &'i mut dyn fmt::Write, f: &'f Writer) -> Self {
        Self {
            i,
            p: Position::default(),
            f,
        }
    }
}

use self::HeaderPosition::*;
use self::MainPosition::*;
use self::QuestionPosition::*;
use self::RecordPosition::*;
use self::SectionPosition::*;

#[derive(Debug, Clone, Default)]
pub struct Position {
    pub main: Option<MainPosition>,
    pub header: Option<HeaderPosition>,
    pub section: Option<SectionPosition>,
    pub question: Option<QuestionPosition>,
    pub record: Option<RecordPosition>,
}

struct ScopedPosition<'w, 'i, 'f> {
    w: &'w mut Wrapper<'i, 'f>,
    old_position: Position,
}

impl<'w, 'i, 'f> From<&'w mut Wrapper<'i, 'f>> for ScopedPosition<'w, 'i, 'f> {
    fn from(w: &'w mut Wrapper<'i, 'f>) -> Self {
        let old_position = w.p.clone();

        Self { w, old_position }
    }
}

impl Drop for ScopedPosition<'_, '_, '_> {
    fn drop(&mut self) {
        self.w.p = self.old_position.clone();
    }
}

impl ScopedPosition<'_, '_, '_> {
    pub fn main(&mut self, m: impl Into<Option<MainPosition>>) -> &mut Self {
        self.w.p.main = m.into();

        self
    }
    pub fn header(&mut self, h: impl Into<Option<HeaderPosition>>) -> &mut Self {
        self.w.p.header = h.into();

        self
    }
    pub fn section(&mut self, s: impl Into<Option<SectionPosition>>) -> &mut Self {
        self.w.p.section = s.into();

        self
    }
    pub fn question(&mut self, q: impl Into<Option<QuestionPosition>>) -> &mut Self {
        self.w.p.question = q.into();

        self
    }
    pub fn record(&mut self, r: impl Into<Option<RecordPosition>>) -> &mut Self {
        self.w.p.record = r.into();

        self
    }
}

#[derive(Debug, Clone)]
pub enum MainPosition {
    Header,
    EdnsHeader,
    Qd,
    An,
    Ns,
    Ar,
}

#[derive(Debug, Clone)]
pub enum HeaderPosition {
    Rcode,
    Id,
    Opcode,
    Qdcount,
    Ancount,
    Nscount,
    Arcount,
    Flag,
}

#[derive(Debug, Clone)]
pub enum SectionPosition {
    Heading,
    QuestionLine,
    RecordLine,
    EdnsPlaceholder,
}

#[derive(Debug, Clone)]
pub enum QuestionPosition {
    Qname,
    Qclass,
    Qtype,
}

#[derive(Debug, Clone)]
pub enum RecordPosition {
    Name,
    Ttl,
    Class,
    Type,
    Rdata,
}

pub struct Plain<'i>(pub &'i dyn Format);

impl core::fmt::Debug for Plain<'_> {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        let mut w = Wrapper::plain(f);

        Format::fmt(self.0, &mut w)
    }
}

impl core::fmt::Display for Plain<'_> {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        let mut w = Wrapper::plain(f);

        Format::fmt(self.0, &mut w)
    }
}

pub struct Pretty<'i, 'f>(pub &'i dyn Format, pub &'f Writer);

impl core::fmt::Debug for Pretty<'_, '_> {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        let mut w = Wrapper::with_writer(f, self.1);

        Format::fmt(self.0, &mut w)
    }
}

impl core::fmt::Display for Pretty<'_, '_> {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        let mut w = Wrapper::with_writer(f, self.1);

        Format::fmt(self.0, &mut w)
    }
}

impl Format for Message<'_> {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        let mut p = ScopedPosition::from(w);
        p.main(Header);

        write!(p.header(None).w, ";; ")?;
        self.rcode().fmt(p.header(Rcode).w)?;
        write!(p.header(None).w, " ")?;
        self.header().fmt(p.w)?;
        writeln!(p.w)?;

        let opt = self.opt();

        if let Some(extension) = opt {
            write!(p.main(EdnsHeader).w, ";; ")?;
            extension.fmt(p.w)?;
            writeln!(p.main(None).w)?;
        }

        writeln!(p.main(Qd).w)?;
        write!(p.section(Heading).w, ";; question section")?;
        writeln!(p.section(None).w)?;

        for question in self.qd() {
            question.fmt(p.section(QuestionLine).w)?;
            writeln!(p.section(None).w)?;
        }

        writeln!(p.main(An).w)?;
        write!(p.section(Heading).w, ";; answer section")?;
        writeln!(p.section(None).w)?;

        for record in self.an() {
            record.fmt(p.section(RecordLine).w)?;
            writeln!(p.section(None).w)?;
        }

        writeln!(p.main(Ns).w)?;
        write!(p.section(Heading).w, ";; authority section")?;
        writeln!(p.section(None).w)?;

        for record in self.ns() {
            record.fmt(p.section(RecordLine).w)?;
            writeln!(p.section(None).w)?;
        }

        writeln!(p.main(Ar).w)?;
        write!(p.section(Heading).w, ";; additional section")?;
        writeln!(p.section(None).w)?;

        for record in self.ar() {
            if opt.is_some_and(|opt| opt.offset() == record.offset()) {
                write!(p.section(EdnsPlaceholder).w, "; EDNS OPT RR was here")?;
            } else {
                record.fmt(p.section(RecordLine).w)?;
            }
            writeln!(p.section(None).w)?;
        }

        Ok(())
    }
}

impl Format for Header<'_> {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        let mut p = ScopedPosition::from(w);
        p.main(Header);

        write!(p.header(Id).w, "#{}", self.id())?;
        write!(p.header(None).w, " ")?;
        self.opcode().fmt(p.header(Opcode).w)?;

        write!(p.header(None).w, " ")?;
        write!(p.header(Qdcount).w, "{}", self.qdcount())?;
        write!(p.header(None).w, " ")?;
        write!(p.header(Ancount).w, "{}", self.ancount())?;
        write!(p.header(None).w, " ")?;
        write!(p.header(Nscount).w, "{}", self.nscount())?;
        write!(p.header(None).w, " ")?;
        write!(p.header(Arcount).w, "{}", self.arcount())?;
        write!(p.header(None).w, " flags")?;

        if self.qr() {
            write!(p.header(None).w, " ")?;
            write!(p.header(Flag).w, "qr")?;
        }
        if self.aa() {
            write!(p.header(None).w, " ")?;
            write!(p.header(Flag).w, "aa")?;
        }
        if self.tc() {
            write!(p.header(None).w, " ")?;
            write!(p.header(Flag).w, "tc")?;
        }
        if self.rd() {
            write!(p.header(None).w, " ")?;
            write!(p.header(Flag).w, "rd")?;
        }
        if self.ra() {
            write!(p.header(None).w, " ")?;
            write!(p.header(Flag).w, "ra")?;
        }

        Ok(())
    }
}

impl Format for Extension<'_> {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        write!(w, "EDNS({}) UDP {} flags", self.version(), self.udp())?;

        if self.r#do() {
            write!(w, " do")?;
        }

        Ok(())
    }
}

impl Format for Question<'_> {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        let mut p = ScopedPosition::from(w);

        // RFC 3597 § 5
        self.qname().fmt(p.question(Qname).w)?;
        write!(p.question(None).w, " ")?;
        self.qclass().fmt(p.question(Qclass).w)?;
        write!(p.question(None).w, " ")?;
        self.qtype().fmt(p.question(Qtype).w)?;

        Ok(())
    }
}

impl Format for Record<'_> {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        let mut p = ScopedPosition::from(w);

        self.name().fmt(p.record(Name).w)?;
        write!(p.record(None).w, " ")?;
        write!(p.record(Ttl).w, "{}", self.ttl().value())?;
        write!(p.record(None).w, " ")?;
        self.class().fmt(p.record(RecordPosition::Class).w)?;
        write!(p.record(None).w, " ")?;
        self.r#type().fmt(p.record(RecordPosition::Type).w)?;
        write!(p.record(None).w, " ")?;
        let rdata = self.rdata();
        let rdata: &dyn Format = rdata.as_ref();
        rdata.fmt(p.record(Rdata).w)?;

        Ok(())
    }
}

impl Format for Name<'_> {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        let mut first = true;

        for label in self.labels_with_null() {
            if !label.is_null() {
                label.fmt(w)?;
            }
            if !label.is_null() || first {
                write!(w, ".")?;
            }

            first = false;
        }

        Ok(())
    }
}

impl Format for Label<'_> {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        let value = self.value().expect("FIXME invalid label");
        for &octet in value {
            display_octet(w, octet, |x| match x {
                b' ' | b';' => OctetStyle::Decimal,
                b'-' | b'_' => OctetStyle::Identity,
                x if x.is_ascii_alphanumeric() => OctetStyle::Identity,
                x if x.is_ascii_graphic() => OctetStyle::PrefixBackslash,
                _ => OctetStyle::Decimal,
            })?;
        }

        Ok(())
    }
}

impl Format for Opcode {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        if let Some(name) = OPCODE.to_name(self.value().into()) {
            write!(w, "{}", name)
        } else {
            // FIXME canonical format?
            write!(w, "OPCODE?{}", self.value())
        }
    }
}

impl Format for Rcode {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        if let Some(name) = RCODE.to_name_opt(self.value()) {
            write!(w, "{}", name)
        } else {
            // FIXME canonical format?
            write!(w, "RCODE?{}", self.value())
        }
    }
}

impl Format for Type {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        if let Some(name) = TYPE.to_name(self.value()) {
            write!(w, "{}", name)
        } else {
            // RFC 3597 § 5
            write!(w, "TYPE{}", self.value())
        }
    }
}

impl Format for Class {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        if let Some(name) = CLASS.to_name(self.value()) {
            write!(w, "{}", name)
        } else {
            // RFC 3597 § 5
            write!(w, "CLASS{}", self.value())
        }
    }
}

impl Format for Ttl {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        write!(w, "{}", self.value())
    }
}

impl Format for Serial {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        write!(w, "{}", self.value())
    }
}

impl Format for CharacterString<'_> {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        write!(w, r#"""#)?;

        for &octet in self.value() {
            display_octet(w, octet, |x| match x {
                b'\\' | b'"' => OctetStyle::Decimal,
                b' ' => OctetStyle::Identity,
                x if x.is_ascii_graphic() => OctetStyle::Identity,
                _ => OctetStyle::Decimal,
            })?;
        }

        write!(w, r#"""#)?;

        Ok(())
    }
}

impl Format for Ns<'_> {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        self.name().fmt(w)
    }
}

impl Format for Cname<'_> {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        self.name().fmt(w)
    }
}

impl Format for Soa<'_> {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        self.mname().fmt(w)?;
        write!(w, " ")?;
        self.rname().fmt(w)?;
        write!(w, " ")?;
        self.serial().fmt(w)?;
        write!(w, " ")?;
        self.refresh().fmt(w)?;
        write!(w, " ")?;
        self.retry().fmt(w)?;
        write!(w, " ")?;
        self.expire().fmt(w)?;
        write!(w, " ")?;
        self.minimum().fmt(w)?;

        Ok(())
    }
}

impl Format for Ptr<'_> {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        self.name().fmt(w)
    }
}

impl Format for Mx<'_> {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        write!(w, "{} ", self.preference())?;
        self.exchange().fmt(w)?;

        Ok(())
    }
}

impl Format for Txt<'_> {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        for string in self.data() {
            string.fmt(w)?;
            write!(w, " ")?;
        }

        Ok(())
    }
}

impl Format for Caa<'_> {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        write!(w, "{} ", self.flags())?;
        self.tag().fmt(w)?;
        write!(w, " ")?;
        self.value().fmt(w)?;

        Ok(())
    }
}

impl Format for CaaTag<'_> {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        for octet in self.as_bytes() {
            display_octet(w, *octet, |x| {
                if x.is_ascii_alphanumeric() {
                    OctetStyle::Identity
                } else {
                    OctetStyle::Decimal
                }
            })?;
        }

        Ok(())
    }
}

impl Format for CaaValue<'_> {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        write!(w, r#"""#)?;

        for octet in self.as_bytes() {
            display_octet(w, *octet, |x| match x {
                b'\\' | b'"' => OctetStyle::Decimal,
                x if x.is_ascii_graphic() => OctetStyle::Identity,
                _ => OctetStyle::Decimal,
            })?;
        }

        write!(w, r#"""#)?;

        Ok(())
    }
}

impl Format for A<'_> {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        write!(
            w,
            "{}.{}.{}.{}",
            self.as_bytes()[0],
            self.as_bytes()[1],
            self.as_bytes()[2],
            self.as_bytes()[3],
        )
    }
}

impl Format for Aaaa<'_> {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        let x = self.to_ipv6_addr().segments();

        // The one at bit 8 (and hence the use of u16) ensures that we count
        // trailing zeros correctly if all ones have been shifted out.
        let zero = 0x100
            | u16::from(x[0] != 0) << 0
            | u16::from(x[1] != 0) << 1
            | u16::from(x[2] != 0) << 2
            | u16::from(x[3] != 0) << 3
            | u16::from(x[4] != 0) << 4
            | u16::from(x[5] != 0) << 5
            | u16::from(x[6] != 0) << 6
            | u16::from(x[7] != 0) << 7;

        // RFC 5952
        let (start, len) = (0..8)
            .map(|i| (zero >> i).trailing_zeros())
            .enumerate()
            .filter(|(_, n)| *n > 1) // § 4.2.2
            .rev() // § 4.2.3 (leftmost)
            .max_by_key(|(_, n)| *n) // § 4.2.3 (longest)
            .unwrap_or((0, 0));

        let len = usize::try_from(len).expect("len is always ≤ 8");

        for i in 0..start {
            write!(w, "{}{:x}", if i > 0 { ":" } else { "" }, x[i])?;
        }
        if len > 0 {
            write!(w, "::")?;
        }
        for i in (start + len)..8 {
            write!(w, "{:x}{}", x[i], if i < 7 { ":" } else { "" })?;
        }

        Ok(())
    }
}

impl Format for Malformed<'_> {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        self.as_unknown().fmt(w)
    }
}

impl Format for Unknown<'_> {
    fn fmt(&self, w: &mut Wrapper) -> fmt::Result {
        // RFC 3597 § 5
        write!(w, "\\# {}", self.len())?;

        for octet in self.as_bytes() {
            write!(w, " {:02X}", octet)?;
        }

        Ok(())
    }
}

pub enum OctetStyle {
    Identity,
    PrefixBackslash,
    Decimal,
}

pub fn display_octet(
    sink: &mut Wrapper,
    octet: u8,
    style: impl FnOnce(u8) -> OctetStyle,
) -> fmt::Result {
    // octet as char only makes sense below 80h
    if octet >= 0x80 {
        return write!(sink, "\\{:03}", octet);
    }

    match style(octet) {
        OctetStyle::Identity => write!(sink, "{}", octet as char),
        OctetStyle::PrefixBackslash => write!(sink, "\\{}", octet as char),
        OctetStyle::Decimal => write!(sink, "\\{:03}", octet),
    }
}

#[cfg(test)]
mod test {
    use core::fmt::Write;

    use arrayvec::ArrayString;
    use assert_matches::assert_matches;

    use crate::{fmt::Plain, view::View};

    declare_any_error!(AnyError);

    type S12 = ArrayString<4096>;

    macro_rules! assert {
        ($type:ident $source:literal yields $output:literal) => (
            assert_matches!(assert!(@write $type $source), (ref x, Ok(_)) if x == $output);
        );

        ($type:ident $source:literal fails) => (
            assert_matches!(assert!(@write $type $source), (_, Err(_)))
        );

        (@write $type:ident $source:literal) => ({
            let mut sink = S12::default();
            let result = super::$type::view($source, 0..$source.len())
                .map(|(view, _)| write!(&mut sink, "{}", Plain(&view)));

            (sink, result)
        });
    }

    #[test]
    fn record() -> Result<(), AnyError> {
        let mut sink = S12::default();
        let source = b"\0\x00\x02\x00\x01\x00\x00\x00\x00\x00\x00";
        let (record, _) = super::Record::view(source, ..)?;
        write!(&mut sink, "{}", Plain(&record))?;

        assert_eq!(&*sink, r#". 0 IN NS \# 0"#);

        Ok(())
    }

    #[test]
    fn soa() {
        assert!(Soa b"\x05daria\x03daz\x03cat\0\x05delan\x07azabani\x03com\0\x78\x57\xF7\xD8\x00\x00\x02\x58\x00\x00\x00\x3C\x00\x1B\xAF\x80\x00\x00\x00\x3C" yields "daria.daz.cat. delan.azabani.com. 2019031000 600 60 1814400 60");
    }

    #[test]
    fn mx() {
        assert!(Mx b"\x00\x0D\x05daria\x03daz\x03cat\0" yields "13 daria.daz.cat.");
    }

    #[test]
    fn txt() {
        assert!(Txt b"\x05hello\x01 \x05world" yields r#""hello" " " "world" "#);
    }

    #[test]
    fn caa() {
        assert!(Caa b"\x80\x05issueletsencrypt.org" yields r#"128 issue "letsencrypt.org""#);
    }

    #[test]
    fn in_address() {
        assert!(A b"\xC0\x00\x02\x00" yields "192.0.2.0");
        assert!(A b"\xC0\x00\x02" fails);
    }

    #[test]
    fn in_aaaa() {
        // RFC 5952 § 4 > RFC 4291 § 2.2
        // § 4.1 leading zeros MUST be suppressed
        assert!(Aaaa b"\0\x01\0\x01\0\x01\0\x01\0\x01\0\x01\0\x01\0\x01" yields "1:1:1:1:1:1:1:1");
        // § 4.2.1 double colon MUST consume all adjacent zeros
        assert!(Aaaa b"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\x01" yields "::1");
        assert!(Aaaa b"\0\x01\0\0\0\0\0\0\0\0\0\0\0\0\0\x01" yields "1::1");
        assert!(Aaaa b"\0\x01\0\0\0\0\0\0\0\0\0\0\0\0\0\0" yields "1::");
        // § 4.2.2 double colon MUST cover two or more words
        assert!(Aaaa b"\0\0\0\x01\0\x01\0\x01\0\x01\0\x01\0\x01\0\x01" yields "0:1:1:1:1:1:1:1");
        assert!(Aaaa b"\0\x01\0\0\0\x01\0\x01\0\x01\0\x01\0\x01\0\x01" yields "1:0:1:1:1:1:1:1");
        assert!(Aaaa b"\0\x01\0\x01\0\x01\0\x01\0\x01\0\x01\0\x01\0\0" yields "1:1:1:1:1:1:1:0");
        // § 4.2.3 double colon MUST cover leftmost longest run
        assert!(Aaaa b"\0\0\0\0\0\0\0\x01\0\x01\0\0\0\0\0\0" yields "::1:1:0:0:0");
        assert!(Aaaa b"\0\0\0\0\0\0\0\x01\0\0\0\0\0\0\0\x01" yields "::1:0:0:0:1");
        assert!(Aaaa b"\0\x01\0\0\0\0\0\0\0\x01\0\0\0\0\0\0" yields "1::1:0:0:0");
        assert!(Aaaa b"\0\x01\0\0\0\0\0\x01\0\x01\0\0\0\0\0\x01" yields "1::1:1:0:0:1");
        // § 4.3 hexadecimal digits MUST be in lowercase form
        assert!(Aaaa b"\0\xAA\0\xBB\0\xCC\0\xDD\0\xEE\0\xFF\0\0\0\0" yields "aa:bb:cc:dd:ee:ff::");
        // § 5 mixed notation for IPv4-in-lowest-32 is RECOMMENDED (well-known) or OPTIONAL (otherwise)
        assert!(Aaaa b"\0\0\0\0\0\0\0\0\0\0\xFF\xFF\x7F\0\0\x01" yields "::ffff:7f00:1");

        // nonymous test suite
        assert!(Aaaa b"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\x01" yields "::1"); // 7l
        assert!(Aaaa b"\x20\x01\x0D\xB8\xAA\xAA\0\0\0\0\0\0\0\0\0\0" yields "2001:db8:aaaa::"); // 5r
        assert!(Aaaa b"\x20\x01\x0D\xB8\0\0\xAA\xAA\0\0\0\0\0\0\0\0" yields "2001:db8:0:aaaa::"); // 1 4r
        assert!(Aaaa b"\x20\x01\x0D\xB8\0\0\0\0\xAA\xAA\0\0\0\0\0\0" yields "2001:db8:0:0:aaaa::"); // 2 3r
        assert!(Aaaa b"\x20\x01\x0D\xB8\0\0\0\0\xAA\xAA\xAA\xAA\0\0\0\0" yields "2001:db8::aaaa:aaaa:0:0"); // 2 2r
        assert!(Aaaa b"\x20\x01\x0D\xB8\0\0\0\0\0\0\xAA\xAA\0\0\0\0" yields "2001:db8::aaaa:0:0"); // 3 2r
        assert!(Aaaa b"\x20\x01\x0D\xB8\0\0\0\0\0\0\0\0\xAA\xAA\0\0" yields "2001:db8::aaaa:0"); // 4 1r
        assert!(Aaaa b"\x20\x01\x0D\xB8\0\0\0\0\0\0\0\0\0\0\xAA\xAA" yields "2001:db8::aaaa"); // 5
        assert!(Aaaa b"\x20\x01\x0D\xB8\0\0\0\0\0\0\0\0\0\0\0\0" yields "2001:db8::"); // 6r
        assert!(Aaaa b"\x20\x01\x0D\xB8\0\0\0\0\0\0\0\0\0\0\0" fails);
    }

    #[test]
    fn unknown() {
        assert!(Unknown b"" yields "\\# 0");
        assert!(Unknown b"\xFF" yields "\\# 1 FF");
    }
}

#[cfg(all(test, feature = "bench"))]
mod bench {
    extern crate test;

    use alloc::string::String;
    use core::fmt::Write;
    use test::bench::black_box as b;
    use test::Bencher;

    use crate::{
        fmt::Plain,
        view::{Message, View},
    };

    declare_any_error!(AnyError);

    #[bench]
    fn response(bencher: &mut Bencher) -> Result<(), AnyError> {
        let source = include_bytes!("../samples/daria.daz.cat.a.dns");
        let (message, _) = Message::view(source, ..)?;

        bencher.iter(|| -> Result<usize, AnyError> {
            let mut out = String::new();
            write!(out, "{}", Plain(b(&message)))?;

            Ok(out.len())
        });

        Ok(())
    }
}