use std::{
    fmt::{self, Display, Formatter, Write},
    io,
};

use tokio::io::{AsyncWrite, AsyncWriteExt};

use super::{
    AttDef, AttDefName, AttType, AttValue, AttValueData, AttlistDecl, Attribute, CDEnd, CDSect,
    CDStart, CData, Char, CharData, CharRef, Children, ChildrenKind, Choice, Comment,
    ConditionalSect, Content, ContentItem, Contentspec, Cp, CpKind, DeclSep, DefaultAttName,
    DefaultDecl, DoctypeDecl, Document, ETag, Element, Elementdecl, EmptyElemTag, EncName,
    EncodingDecl, EntityDecl, EntityDef, EntityRef, EntityValue, EntityValueData, EnumeratedType,
    Enumeration, Eq, ExtParsedEnt, ExtSubset, ExtSubsetDecl, ExtSubsetDeclaration, ExternalID,
    GEDecl, Ignore, IgnoreSect, IgnoreSectContents, IncludeSect, IntSubset, LocalPart, MarkupDecl,
    Misc, Mixed, NCName, NDataDecl, NSAttName, Name, NameChar, NameStartChar, Names, Nmtoken,
    Nmtokens, NotationDecl, NotationDeclID, NotationType, Occurence, PEDecl, PEDef, PEReference,
    PITarget, Prefix, PrefixedAttName, PrefixedName, Prolog, PubidChar, PubidLiteral, PublicID,
    QName, Reference, SDDecl, STag, Seq, StringType, SystemLiteral, TextDecl, TokenizedType,
    UnprefixedName, VersionInfo, VersionNum, XMLDecl, PI, S,
};

/// Compact Composer trait, can create different trait later for pretty composition
pub trait Composer<'s> {
    fn write<W>(&self, writer: &mut W) -> impl std::future::Future<Output = io::Result<()>>
    where
        W: Unpin + AsyncWrite;
}

// namespaces in xml

/// [1]   	NSAttName	   ::=   	PrefixedAttName | DefaultAttName
impl<'s> Composer<'s> for NSAttName<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: AsyncWrite + Unpin,
    {
        match self {
            NSAttName::PrefixedAttName(prefixed_att_name) => {
                prefixed_att_name.write(writer).await?
            }
            NSAttName::DefaultAttName => DefaultAttName.write(writer).await?,
        }
        Ok(())
    }
}

/// [2]   	PrefixedAttName	   ::=   	'xmlns:' NCName
impl<'s> Composer<'s> for PrefixedAttName<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: AsyncWrite + Unpin,
    {
        writer.write_all("xmlns:".as_bytes()).await?;
        self.0.write(writer).await?;
        Ok(())
    }
}

/// [3]   	DefaultAttName	   ::=   	'xmlns';
impl Composer<'_> for DefaultAttName {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: AsyncWrite + Unpin,
    {
        writer.write_all("xmlns".as_bytes()).await?;
        Ok(())
    }
}

/// [4]   	NCName	   ::=   	Name - (Char* ':' Char*)
impl<'s> Composer<'s> for NCName<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: AsyncWrite + Unpin,
    {
        writer.write_all(self.0.as_bytes()).await?;
        Ok(())
    }
}

/// [7]   	QName	   ::=   	PrefixedName | UnprefixedName
impl<'s> Composer<'s> for QName<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: AsyncWrite + Unpin,
    {
        match self {
            QName::PrefixedName(prefixed_name) => prefixed_name.write(writer).await?,
            QName::UnprefixedName(unprefixed_name) => unprefixed_name.write(writer).await?,
        }
        Ok(())
    }
}

/// [8]   	PrefixedName	   ::=   	Prefix ':' LocalPart
impl<'s> Composer<'s> for PrefixedName<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: AsyncWrite + Unpin,
    {
        self.prefix.write(writer).await?;
        writer.write_all(":".as_bytes()).await?;
        self.local_part.write(writer).await?;
        Ok(())
    }
}

/// [9]   	UnprefixedName	   ::=   	LocalPart
impl<'s> Composer<'s> for UnprefixedName<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        self.0.write(writer).await?;
        Ok(())
    }
}

/// [10]   	Prefix	   ::=   	NCName
impl<'s> Composer<'s> for Prefix<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        self.0.write(writer).await?;
        Ok(())
    }
}

/// [11]   	LocalPart	   ::=   	NCName
impl<'s> Composer<'s> for LocalPart<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        self.0.write(writer).await?;
        Ok(())
    }
}

// xml spec

/// [1]   	document	   ::=   	prolog element Misc*
impl<'s> Composer<'s> for Document<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        self.prolog.write(writer).await?;
        self.element.write(writer).await?;
        for misc in &self.miscs {
            misc.write(writer).await?
        }
        Ok(())
    }
}

/// [2]   	Char	   ::=   	#x9 | #xA | #xD | [#x20-#xD7FF] | [#xE000-#xFFFD] | [#x10000-#x10FFFF]	/* any Unicode character, excluding the surrogate blocks, FFFE, and FFFF. */
impl Composer<'_> for Char {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all(self.0.to_string().as_bytes()).await?;
        Ok(())
    }
}

/// [3]   	S	   ::=   	(#x20 | #x9 | #xD | #xA)+
impl<'s> Composer<'s> for S {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("\u{20}".as_bytes()).await?;
        Ok(())
    }
}

/// [4]   	NameStartChar	   ::=   	":" | [A-Z] | "_" | [a-z] | [#xC0-#xD6] | [#xD8-#xF6] | [#xF8-#x2FF] | [#x370-#x37D] | [#x37F-#x1FFF] | [#x200C-#x200D] | [#x2070-#x218F] | [#x2C00-#x2FEF] | [#x3001-#xD7FF] | [#xF900-#xFDCF] | [#xFDF0-#xFFFD] | [#x10000-#xEFFFF]
impl Composer<'_> for NameStartChar {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all(self.0.to_string().as_bytes()).await?;
        Ok(())
    }
}

/// [4a]   	NameChar	   ::=   	NameStartChar | "-" | "." | [0-9] | #xB7 | [#x0300-#x036F] | [#x203F-#x2040]
impl Composer<'_> for NameChar {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all(self.0.to_string().as_bytes()).await?;
        Ok(())
    }
}

/// [5]   	Name	   ::=   	NameStartChar (NameChar)*
impl<'s> Composer<'s> for Name<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all(self.0.as_bytes()).await?;
        Ok(())
    }
}

/// [6]   	Names	   ::=   	Name (#x20 Name)*
impl<'s> Composer<'s> for Names<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        let mut first = true;
        for name in &self.0 {
            if !first {
                writer.write_all("\u{20}".as_bytes()).await?;
            }
            name.write(writer).await?;
            if first {
                first = false
            }
        }
        Ok(())
    }
}

/// [7]   	Nmtoken	   ::=   	(NameChar)+
impl<'s> Composer<'s> for Nmtoken<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all(self.0.as_bytes()).await?;
        Ok(())
    }
}

/// [8]   	Nmtokens	   ::=   	Nmtoken (#x20 Nmtoken)*
impl<'s> Composer<'s> for Nmtokens<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        let mut first = true;
        for nmtoken in &self.0 {
            if !first {
                writer.write_all("\u{20}".as_bytes()).await?;
            }
            nmtoken.write(writer).await?;
            if first {
                first = false
            }
        }
        Ok(())
    }
}

/// [9]   	EntityValue	   ::=   	'"' ([^%&"] | PEReference | Reference)* '"'
///			|  "'" ([^%&'] | PEReference | Reference)* "'"
impl<'s> Composer<'s> for EntityValue<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        match self {
            EntityValue::DoubleQuoted(entity_value_data) => {
                writer.write_all("\"".as_bytes()).await?;
                for entity_value_data in entity_value_data {
                    match entity_value_data {
                        EntityValueData::String(s) => writer.write_all(s.as_bytes()).await?,
                        EntityValueData::PEReference(pe_reference) => {
                            pe_reference.write(writer).await?
                        }
                        EntityValueData::Reference(reference) => reference.write(writer).await?,
                    }
                }
                writer.write_all("\"".as_bytes()).await?;
            }
            EntityValue::SingleQuoted(entity_value_data) => {
                writer.write_all("'".as_bytes()).await?;
                for entity_value_data in entity_value_data {
                    match entity_value_data {
                        EntityValueData::String(s) => writer.write_all(s.as_bytes()).await?,
                        EntityValueData::PEReference(pe_reference) => {
                            pe_reference.write(writer).await?
                        }
                        EntityValueData::Reference(reference) => reference.write(writer).await?,
                    }
                }
                writer.write_all("'".as_bytes()).await?;
            }
        }
        Ok(())
    }
}

/// [10]   	AttValue	   ::=   	'"' ([^<&"] | Reference)* '"'
/// 			|  "'" ([^<&'] | Reference)* "'"
impl<'s> Composer<'s> for AttValue<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        match self {
            AttValue::DoubleQuoted(att_value_data) => {
                writer.write_all("\"".as_bytes()).await?;
                for att_value_data in att_value_data {
                    match att_value_data {
                        AttValueData::String(s) => writer.write_all(s.as_bytes()).await?,
                        AttValueData::Reference(reference) => reference.write(writer).await?,
                    }
                }
                writer.write_all("\"".as_bytes()).await?;
            }
            AttValue::SingleQuoted(att_value_data) => {
                writer.write_all("'".as_bytes()).await?;
                for att_value_data in att_value_data {
                    match att_value_data {
                        AttValueData::String(s) => writer.write_all(s.as_bytes()).await?,
                        AttValueData::Reference(reference) => reference.write(writer).await?,
                    }
                }
                writer.write_all("'".as_bytes()).await?;
            }
        }
        Ok(())
    }
}

/// [11]   	SystemLiteral	   ::=   	('"' [^"]* '"') | ("'" [^']* "'")
impl<'s> Composer<'s> for SystemLiteral<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        match self {
            SystemLiteral::DoubleQuoted(s) => {
                writer.write_all("\"".as_bytes()).await?;
                writer.write_all(s.as_bytes()).await?;
                writer.write_all("\"".as_bytes()).await?;
            }
            SystemLiteral::SingleQuoted(s) => {
                writer.write_all("'".as_bytes()).await?;
                writer.write_all(s.as_bytes()).await?;
                writer.write_all("'".as_bytes()).await?;
            }
        }
        Ok(())
    }
}

/// [12]   	PubidLiteral	   ::=   	'"' PubidChar* '"' | "'" (PubidChar - "'")* "'"
impl<'s> Composer<'s> for PubidLiteral<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        match self {
            PubidLiteral::DoubleQuoted(s) => {
                writer.write_all("\"".as_bytes()).await?;
                writer.write_all(s.as_bytes()).await?;
                writer.write_all("\"".as_bytes()).await?;
            }
            PubidLiteral::SingleQuoted(s) => {
                writer.write_all("'".as_bytes()).await?;
                writer.write_all(s.as_bytes()).await?;
                writer.write_all("'".as_bytes()).await?;
            }
        }
        Ok(())
    }
}

/// [13]   	PubidChar	   ::=   	#x20 | #xD | #xA | [a-zA-Z0-9] | [-'()+,./:=?;!*#@$_%]
impl Composer<'_> for PubidChar {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all(self.0.to_string().as_bytes()).await?;
        Ok(())
    }
}

/// [14]   	CharData	   ::=   	[^<&]* - ([^<&]* ']]>' [^<&]*)
impl<'s> Composer<'s> for CharData<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all(self.0.as_bytes()).await?;
        Ok(())
    }
}

/// [15]    Comment	   ::=   	'<!--' ((Char - '-') | ('-' (Char - '-')))* '-->'
impl<'s> Composer<'s> for Comment<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("<!--".as_bytes()).await?;
        writer.write_all(self.0.as_bytes()).await?;
        writer.write_all("-->".as_bytes()).await?;
        Ok(())
    }
}

/// [16]   	PI	   ::=   	'<?' PITarget (S (Char* - (Char* '?>' Char*)))? '?>'
impl<'s> Composer<'s> for PI<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("<?".as_bytes()).await?;
        self.target.write(writer).await?;
        if let Some(instruction) = self.instruction {
            S.write(writer).await?;
            writer.write_all(instruction.as_bytes()).await?;
        }
        writer.write_all("?>".as_bytes()).await?;
        Ok(())
    }
}

/// [17]   	PITarget	   ::=   	Name - (('X' | 'x') ('M' | 'm') ('L' | 'l'))
impl<'s> Composer<'s> for PITarget<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        self.0.write(writer).await?;
        Ok(())
    }
}

/// [18]   	CDSect	   ::=   	CDStart CData CDEnd
impl<'s> Composer<'s> for CDSect<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        CDStart.write(writer).await?;
        self.0.write(writer).await?;
        CDEnd.write(writer).await?;
        Ok(())
    }
}

/// [19]   	CDStart	   ::=   	'<![CDATA['
impl Composer<'_> for CDStart {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("<![CDATA[".as_bytes()).await?;
        Ok(())
    }
}

/// [20]   	CData	   ::=   	(Char* - (Char* ']]>' Char*))
impl<'s> Composer<'s> for CData<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all(self.0.as_bytes()).await?;
        Ok(())
    }
}

/// [21]   	CDEnd	   ::=   	']]>'
impl Composer<'_> for CDEnd {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("]]>".as_bytes()).await?;
        Ok(())
    }
}

/// [22]   	prolog	   ::=   	XMLDecl? Misc* (doctypedecl Misc*)?
impl<'s> Composer<'s> for Prolog<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        if let Some(xml_decl) = &self.xml_decl {
            xml_decl.write(writer).await?;
        }
        for misc in &self.miscs {
            misc.write(writer).await?;
        }
        if let Some((doctype_decl, miscs)) = &self.doctype_decl {
            doctype_decl.write(writer).await?;
            for misc in miscs {
                misc.write(writer).await?;
            }
        }
        Ok(())
    }
}

/// [23]   	XMLDecl	   ::=   	'<?xml' VersionInfo EncodingDecl? SDDecl? S? '?>'
impl<'s> Composer<'s> for XMLDecl<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("<?xml".as_bytes()).await?;
        self.version_info.write(writer).await?;
        if let Some(encoding_decl) = &self.encoding_decl {
            encoding_decl.write(writer).await?
        }
        if let Some(sd_decl) = &self.sd_decl {
            sd_decl.write(writer).await?
        }
        writer.write_all("?>".as_bytes()).await?;
        Ok(())
    }
}

/// [24]   	VersionInfo	   ::=   	S 'version' Eq ("'" VersionNum "'" | '"' VersionNum '"')
impl Composer<'_> for VersionInfo {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        S.write(writer).await?;
        writer.write_all("version".as_bytes()).await?;
        Eq.write(writer).await?;
        match self {
            VersionInfo::SingleQuoted(version_num) => {
                writer.write_all("'".as_bytes()).await?;
                version_num.write(writer).await?;
                writer.write_all("'".as_bytes()).await?;
            }
            VersionInfo::DoubleQuoted(version_num) => {
                writer.write_all("\"".as_bytes()).await?;
                version_num.write(writer).await?;
                writer.write_all("\"".as_bytes()).await?;
            }
        }
        Ok(())
    }
}

/// [25]   	Eq	   ::=   	S? '=' S?
impl Composer<'_> for Eq {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("=".as_bytes()).await?;
        Ok(())
    }
}

/// [26]   	VersionNum	   ::=   	'1.' [0-9]+
impl Composer<'_> for VersionNum {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        match self {
            VersionNum::One => writer.write_all("1.0".as_bytes()).await?,
            VersionNum::OneDotOne => writer.write_all("1.1".as_bytes()).await?,
        }
        Ok(())
    }
}

/// [27]   	Misc	   ::=   	Comment | PI | S
impl<'s> Composer<'s> for Misc<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        match self {
            Misc::Comment(comment) => comment.write(writer).await?,
            Misc::PI(pi) => pi.write(writer).await?,
            Misc::S => {}
        }
        Ok(())
    }
}

/// [16]   	doctypedecl	   ::=   	'<!DOCTYPE' S QName (S ExternalID)? S? ('[' (markupdecl | PEReference | S)* ']' S?)? '>'
/// [28]   	doctypedecl	   ::=   	'<!DOCTYPE' S Name (S ExternalID)? S? ('[' intSubset ']' S?)? '>'
impl<'s> Composer<'s> for DoctypeDecl<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("<!DOCTYPE".as_bytes()).await?;
        S.write(writer).await?;
        self.name.write(writer).await?;
        if let Some(external_id) = &self.external_id {
            S.write(writer).await?;
            external_id.write(writer).await?;
        }
        if let Some(int_subset) = &self.int_subset {
            writer.write_all("[".as_bytes()).await?;
            int_subset.write(writer).await?;
            writer.write_all("]".as_bytes()).await?;
        }
        writer.write_all(">".as_bytes()).await?;
        Ok(())
    }
}

/// [28a]   	DeclSep	   ::=   	PEReference | S
impl<'s> Composer<'s> for DeclSep<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        match self {
            DeclSep::PEReference(pe_reference) => pe_reference.write(writer).await?,
            DeclSep::S => S.write(writer).await?,
        }
        Ok(())
    }
}

/// [28b]   	intSubset	   ::=   	(markupdecl | DeclSep)*
impl<'s> Composer<'s> for IntSubset<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        for declaration in &self.0 {
            match declaration {
                super::IntSubsetDeclaration::MarkupDecl(markup_decl) => {
                    markup_decl.write(writer).await?
                }
                super::IntSubsetDeclaration::DeclSep(decl_sep) => decl_sep.write(writer).await?,
            }
        }
        Ok(())
    }
}

/// [29]   	markupdecl	   ::=   	elementdecl | AttlistDecl | EntityDecl | NotationDecl | PI | Comment
impl<'s> Composer<'s> for MarkupDecl<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        match self {
            MarkupDecl::Elementdecl(elementdecl) => elementdecl.write(writer).await?,
            MarkupDecl::AttlistDecl(attlist_decl) => attlist_decl.write(writer).await?,
            MarkupDecl::EntityDecl(entity_decl) => entity_decl.write(writer).await?,
            MarkupDecl::NotationDecl(notation_decl) => notation_decl.write(writer).await?,
            MarkupDecl::PI(pi) => pi.write(writer).await?,
            MarkupDecl::Comment(comment) => comment.write(writer).await?,
        }
        Ok(())
    }
}

/// [30]   	extSubset	   ::=   	TextDecl? extSubsetDecl
impl<'s> Composer<'s> for ExtSubset<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        if let Some(text_decl) = &self.text_decl {
            text_decl.write(writer).await?
        }
        self.ext_subset_decl.write(writer).await?;
        Ok(())
    }
}

/// [31]   	extSubsetDecl	   ::=   	( markupdecl | conditionalSect | DeclSep)*
impl<'s> Composer<'s> for ExtSubsetDecl<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        for declaration in &self.0 {
            match declaration {
                ExtSubsetDeclaration::MarkupDecl(markup_decl) => markup_decl.write(writer).await?,
                ExtSubsetDeclaration::ConditionalSect(conditional_sect) => {
                    Box::pin(conditional_sect.write(writer)).await?
                }
                ExtSubsetDeclaration::DeclSep(decl_sep) => decl_sep.write(writer).await?,
            }
        }
        Ok(())
    }
}

/// [32]   	SDDecl	   ::=   	S 'standalone' Eq (("'" ('yes' | 'no') "'") | ('"' ('yes' | 'no') '"'))
impl Composer<'_> for SDDecl {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        S.write(writer).await?;
        writer.write_all("standalone".as_bytes()).await?;
        Eq.write(writer).await?;
        match self {
            SDDecl::SingleQuoted(sd_decl) => {
                writer.write_all("'".as_bytes()).await?;
                match sd_decl {
                    true => writer.write_all("yes".as_bytes()).await?,
                    false => writer.write_all("no".as_bytes()).await?,
                }
                writer.write_all("'".as_bytes()).await?;
            }
            SDDecl::DoubleQuoted(sd_decl) => {
                writer.write_all("\"".as_bytes()).await?;
                match sd_decl {
                    true => writer.write_all("yes".as_bytes()).await?,
                    false => writer.write_all("no".as_bytes()).await?,
                }
                writer.write_all("\"".as_bytes()).await?;
            }
        }
        Ok(())
    }
}

// (Productions 33 through 38 have been removed.)

/// [39]   	element	   ::=   	EmptyElemTag | STag content ETag
impl<'s> Composer<'s> for Element<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        match self {
            Element::Empty(empty_elem_tag) => empty_elem_tag.write(writer).await?,
            Element::NotEmpty(s_tag, content, e_tag) => {
                s_tag.write(writer).await?;
                content.write(writer).await?;
                e_tag.write(writer).await?;
            }
        }
        Ok(())
    }
}

/// [12]   	STag	   ::=   	'<' QName (S Attribute)* S? '>'
/// [40]   	STag	   ::=   	'<' Name (S Attribute)* S? '>'
impl<'s> Composer<'s> for STag<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("<".as_bytes()).await?;
        self.name.write(writer).await?;
        for attribute in &self.attributes {
            S.write(writer).await?;
            attribute.write(writer).await?;
        }
        writer.write_all(">".as_bytes()).await?;
        Ok(())
    }
}

/// [15]   	Attribute	   ::=   	NSAttName Eq AttValue | QName Eq AttValue
impl<'s> Composer<'s> for Attribute<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        match self {
            Attribute::NamespaceDeclaration { ns_name, value } => {
                ns_name.write(writer).await?;
                Eq.write(writer).await?;
                value.write(writer).await?;
            }
            Attribute::Attribute { name, value } => {
                name.write(writer).await?;
                Eq.write(writer).await?;
                value.write(writer).await?;
            }
        }
        Ok(())
    }
}

/// [13]   	ETag	   ::=   	'</' QName S? '>'
impl<'s> Composer<'s> for ETag<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("</".as_bytes()).await?;
        self.name.write(writer).await?;
        writer.write_all(">".as_bytes()).await?;
        Ok(())
    }
}

/// [43]   	content	   ::=   	CharData? ((element | Reference | CDSect | PI | Comment) CharData?)*
impl<'s> Composer<'s> for Content<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        if let Some(char_data) = &self.char_data {
            char_data.write(writer).await?;
        }
        for (content, char_data) in &self.content {
            match content {
                ContentItem::Element(element) => Box::pin(element.write(writer)).await?,
                ContentItem::Reference(reference) => reference.write(writer).await?,
                ContentItem::CDSect(cd_sect) => cd_sect.write(writer).await?,
                ContentItem::PI(pi) => pi.write(writer).await?,
                ContentItem::Comment(comment) => comment.write(writer).await?,
                // TODO: verify no split chardata
                // _ => todo!("verify no split chardata"),
            }
            if let Some(char_data) = char_data {
                char_data.write(writer).await?;
            }
        }
        Ok(())
    }
}

/// [14]   	EmptyElemTag	   ::=   	'<' QName (S Attribute)* S? '/>'
impl<'s> Composer<'s> for EmptyElemTag<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("<".as_bytes()).await?;
        self.name.write(writer).await?;
        for attribute in &self.attributes {
            S.write(writer).await?;
            attribute.write(writer).await?;
        }
        writer.write_all("/>".as_bytes()).await?;
        Ok(())
    }
}

/// [17]   	elementdecl	   ::=   	'<!ELEMENT' S QName S contentspec S? '>'
impl<'s> Composer<'s> for Elementdecl<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("<!ELEMENT".as_bytes()).await?;
        S.write(writer).await?;
        self.name.write(writer).await?;
        S.write(writer).await?;
        self.contentspec.write(writer).await?;
        writer.write_all(">".as_bytes()).await?;
        Ok(())
    }
}

/// [46]   	contentspec	   ::=   	'EMPTY' | 'ANY' | Mixed | children
impl<'s> Composer<'s> for Contentspec<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        match self {
            Contentspec::Empty => writer.write_all("EMPTY".as_bytes()).await?,
            Contentspec::Any => writer.write_all("ANY".as_bytes()).await?,
            Contentspec::Mixed(mixed) => mixed.write(writer).await?,
            Contentspec::Children(children) => children.write(writer).await?,
        }
        Ok(())
    }
}

/// Occurence ::= ('?' | '*' | '+')?
impl Composer<'_> for Occurence {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        match self {
            Occurence::Once => {}
            Occurence::Optional => writer.write_all("?".as_bytes()).await?,
            Occurence::Many0 => writer.write_all("*".as_bytes()).await?,
            Occurence::Many1 => writer.write_all("+".as_bytes()).await?,
        }
        Ok(())
    }
}

/// [47]   	children	   ::=   	(choice | seq) ('?' | '*' | '+')?
impl<'s> Composer<'s> for Children<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        match &self.kind {
            ChildrenKind::Choice(choice) => choice.write(writer).await?,
            ChildrenKind::Seq(seq) => seq.write(writer).await?,
        }
        self.occurence.write(writer).await?;
        Ok(())
    }
}

/// [18]   	cp	   ::=   	(QName | choice | seq) ('?' | '*' | '+')?
impl<'s> Composer<'s> for Cp<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        match &self.kind {
            CpKind::Name(q_name) => q_name.write(writer).await?,
            CpKind::Choice(choice) => Box::pin(choice.write(writer)).await?,
            CpKind::Seq(seq) => Box::pin(seq.write(writer)).await?,
        }
        self.occurence.write(writer).await?;
        Ok(())
    }
}

/// [49]   	choice	   ::=   	'(' S? cp ( S? '|' S? cp )+ S? ')'
impl<'s> Composer<'s> for Choice<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("(".as_bytes()).await?;
        let mut first = true;
        for cp in &self.0 {
            if !first {
                writer.write_all("|".as_bytes()).await?;
            }
            cp.write(writer).await?;
            if first {
                first = false
            }
        }
        writer.write_all(")".as_bytes()).await?;
        Ok(())
    }
}

/// [50]   	seq	   ::=   	'(' S? cp ( S? ',' S? cp )* S? ')'
impl<'s> Composer<'s> for Seq<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("(".as_bytes()).await?;
        let mut first = true;
        for cp in &self.0 {
            if !first {
                writer.write_all(",".as_bytes()).await?;
            }
            cp.write(writer).await?;
            if first {
                first = false
            }
        }
        writer.write_all(")".as_bytes()).await?;
        Ok(())
    }
}

/// [19]   	Mixed	   ::=   	'(' S? '#PCDATA' (S? '|' S? QName)* S? ')*' | '(' S? '#PCDATA' S? ')'
impl<'s> Composer<'s> for Mixed<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("(#PCDATA".as_bytes()).await?;
        if !self.0.is_empty() {
            for q_name in &self.0 {
                writer.write_all("|".as_bytes()).await?;
                q_name.write(writer).await?;
            }
            writer.write_all(")*".as_bytes()).await?;
        } else {
            writer.write_all(")".as_bytes()).await?;
        }
        Ok(())
    }
}

/// [20]   	AttlistDecl	   ::=   	'<!ATTLIST' S QName AttDef* S? '>'
impl<'s> Composer<'s> for AttlistDecl<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("<!ATTLIST".as_bytes()).await?;
        S.write(writer).await?;
        self.element_type.write(writer).await?;
        for att_def in &self.att_defs {
            att_def.write(writer).await?;
        }
        writer.write_all(">".as_bytes()).await?;
        Ok(())
    }
}

/// [21]   	AttDef	   ::=   	S (QName | NSAttName) S AttType S DefaultDecl
impl<'s> Composer<'s> for AttDef<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        S.write(writer).await?;
        match &self.name {
            AttDefName::QName(q_name) => q_name.write(writer).await?,
            AttDefName::NSAttName(ns_att_name) => ns_att_name.write(writer).await?,
        }
        S.write(writer).await?;
        self.att_type.write(writer).await?;
        S.write(writer).await?;
        self.default_decl.write(writer).await?;
        Ok(())
    }
}

/// [54]   	AttType	   ::=   	StringType | TokenizedType | EnumeratedType
impl<'s> Composer<'s> for AttType<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        match self {
            AttType::StringType => StringType.write(writer).await?,
            AttType::TokenizedType(tokenized_type) => tokenized_type.write(writer).await?,
            AttType::EnumeratedType(enumerated_type) => enumerated_type.write(writer).await?,
        }
        Ok(())
    }
}

/// [55]   	StringType	   ::=   	'CDATA'
impl Composer<'_> for StringType {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("CDATA".as_bytes()).await?;
        Ok(())
    }
}

/// [56]   	TokenizedType	   ::=   	'ID' | 'IDREF' | 'IDREFS' | 'ENTITY' | 'ENTITIES' | 'NMTOKEN' | 'NMTOKENS'
impl Composer<'_> for TokenizedType {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        match self {
            TokenizedType::ID => writer.write_all("ID".as_bytes()).await?,
            TokenizedType::IDRef => writer.write_all("IDREF".as_bytes()).await?,
            TokenizedType::IDRefs => writer.write_all("IDREFS".as_bytes()).await?,
            TokenizedType::Entity => writer.write_all("ENTITY".as_bytes()).await?,
            TokenizedType::Entities => writer.write_all("ENTITIES".as_bytes()).await?,
            TokenizedType::NMToken => writer.write_all("NMTOKEN".as_bytes()).await?,
            TokenizedType::NMTokens => writer.write_all("NMTOKENS".as_bytes()).await?,
        }
        Ok(())
    }
}

/// [57]   	EnumeratedType	   ::=   	NotationType | Enumeration
impl<'s> Composer<'s> for EnumeratedType<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        match self {
            EnumeratedType::NotationType(notation_type) => notation_type.write(writer).await?,
            EnumeratedType::Enumeration(enumeration) => enumeration.write(writer).await?,
        }
        Ok(())
    }
}

/// [58]   	NotationType	   ::=   	'NOTATION' S '(' S? Name (S? '|' S? Name)* S? ')'
impl<'s> Composer<'s> for NotationType<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("NOTATION".as_bytes()).await?;
        S.write(writer).await?;
        writer.write_all("(".as_bytes()).await?;
        let mut first = true;
        for name in &self.0 {
            if !first {
                writer.write_all("|".as_bytes()).await?;
            }
            name.write(writer).await?;
            if first {
                first = false
            }
        }
        writer.write_all(")".as_bytes()).await?;
        Ok(())
    }
}

/// [59]   	Enumeration	   ::=   	'(' S? Nmtoken (S? '|' S? Nmtoken)* S? ')'
impl<'s> Composer<'s> for Enumeration<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("(".as_bytes()).await?;
        let mut first = true;
        for nm_token in &self.0 {
            if !first {
                writer.write_all("|".as_bytes()).await?;
            }
            nm_token.write(writer).await?;
            if first {
                first = false
            }
        }
        writer.write_all(")".as_bytes()).await?;
        Ok(())
    }
}

/// [60]   	DefaultDecl	   ::=   	'#REQUIRED' | '#IMPLIED' | (('#FIXED' S)? AttValue)
impl<'s> Composer<'s> for DefaultDecl<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        match self {
            DefaultDecl::Required => writer.write_all("#REQUIRED".as_bytes()).await?,
            DefaultDecl::Implied => writer.write_all("#IMPLIED".as_bytes()).await?,
            DefaultDecl::Fixed(fixed, att_value) => {
                if *fixed {
                    writer.write_all("#FIXED".as_bytes()).await?;
                    S.write(writer).await?;
                }
                att_value.write(writer).await?
            }
        }
        Ok(())
    }
}

/// [61]   	conditionalSect	   ::=   	includeSect | ignoreSect
impl<'s> Composer<'s> for ConditionalSect<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        match self {
            ConditionalSect::IncludeSect(include_sect) => include_sect.write(writer).await?,
            ConditionalSect::IgnoreSect(ignore_sect) => ignore_sect.write(writer).await?,
        }
        Ok(())
    }
}

/// [62]   	includeSect	   ::=   	'<![' S? 'INCLUDE' S? '[' extSubsetDecl ']]>'
impl<'s> Composer<'s> for IncludeSect<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("<![INCLUDE[".as_bytes()).await?;
        self.0.write(writer).await?;
        writer.write_all("]]>".as_bytes()).await?;
        Ok(())
    }
}

/// [63]   	ignoreSect	   ::=   	'<![' S? 'IGNORE' S? '[' ignoreSectContents* ']]>'
impl<'s> Composer<'s> for IgnoreSect<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("<![IGNORE[".as_bytes()).await?;
        for ignore_sect_contents in &self.0 {
            ignore_sect_contents.write(writer).await?;
        }
        writer.write_all("]]>".as_bytes()).await?;
        Ok(())
    }
}

/// [64]   	ignoreSectContents	   ::=   	Ignore ('<![' ignoreSectContents ']]>' Ignore)*
impl<'s> Composer<'s> for IgnoreSectContents<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        self.ignore.write(writer).await?;
        for (ignore_sect_contents, ignore) in &self.ignore_list {
            writer.write_all("<![".as_bytes()).await?;
            Box::pin(ignore_sect_contents.write(writer)).await?;
            writer.write_all("]]>".as_bytes()).await?;
            ignore.write(writer).await?;
        }
        Ok(())
    }
}

/// [65]   	Ignore	   ::=   	Char* - (Char* ('<![' | ']]>') Char*)
impl<'s> Composer<'s> for Ignore<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all(self.0.as_bytes()).await?;
        Ok(())
    }
}

/// [66]   	CharRef	   ::=   	'&#' [0-9]+ ';' | '&#x' [0-9a-fA-F]+ ';'
impl<'s> Composer<'s> for CharRef<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        match self {
            CharRef::Decimal(decimal) => {
                writer.write_all("&#".as_bytes()).await?;
                writer.write_all(decimal.as_bytes()).await?;
                writer.write_all(";".as_bytes()).await?;
            }
            CharRef::Hexadecimal(hexadecimal) => {
                writer.write_all("&#x".as_bytes()).await?;
                writer.write_all(hexadecimal.as_bytes()).await?;
                writer.write_all(";".as_bytes()).await?;
            }
        }
        Ok(())
    }
}

/// [67]   	Reference	   ::=   	EntityRef | CharRef
impl<'s> Composer<'s> for Reference<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        match self {
            Reference::EntityRef(entity_ref) => entity_ref.write(writer).await?,
            Reference::CharRef(char_ref) => char_ref.write(writer).await?,
        }
        Ok(())
    }
}

/// [68]   	EntityRef	   ::=   	'&' Name ';'
impl<'s> Composer<'s> for EntityRef<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("&".as_bytes()).await?;
        self.0.write(writer).await?;
        writer.write_all(";".as_bytes()).await?;
        Ok(())
    }
}

/// [69]   	PEReference	   ::=   	'%' Name ';'
impl<'s> Composer<'s> for PEReference<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("%".as_bytes()).await?;
        self.0.write(writer).await?;
        writer.write_all(";".as_bytes()).await?;
        Ok(())
    }
}

/// [70]   	EntityDecl	   ::=   	GEDecl | PEDecl
impl<'s> Composer<'s> for EntityDecl<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        match self {
            EntityDecl::GEDecl(ge_decl) => ge_decl.write(writer).await?,
            EntityDecl::PEDecl(pe_decl) => pe_decl.write(writer).await?,
        }
        Ok(())
    }
}

/// [71]   	GEDecl	   ::=   	'<!ENTITY' S Name S EntityDef S? '>'
impl<'s> Composer<'s> for GEDecl<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("<!ENTITY".as_bytes()).await?;
        S.write(writer).await?;
        self.name.write(writer).await?;
        S.write(writer).await?;
        self.entity_def.write(writer).await?;
        writer.write_all(">".as_bytes()).await?;
        Ok(())
    }
}

/// [72]   	PEDecl	   ::=   	'<!ENTITY' S '%' S Name S PEDef S? '>'
impl<'s> Composer<'s> for PEDecl<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("<!ENTITY".as_bytes()).await?;
        S.write(writer).await?;
        writer.write_all("%".as_bytes()).await?;
        S.write(writer).await?;
        self.name.write(writer).await?;
        S.write(writer).await?;
        self.pe_def.write(writer).await?;
        writer.write_all(">".as_bytes()).await?;
        Ok(())
    }
}

/// [73]   	EntityDef	   ::=   	EntityValue | (ExternalID NDataDecl?)
impl<'s> Composer<'s> for EntityDef<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        match self {
            EntityDef::EntityValue(entity_value) => entity_value.write(writer).await?,
            EntityDef::ExternalID {
                external_id,
                n_data_decl,
            } => {
                external_id.write(writer).await?;
                if let Some(n_data_decl) = n_data_decl {
                    n_data_decl.write(writer).await?;
                }
            }
        }
        Ok(())
    }
}

/// [74]   	PEDef	   ::=   	EntityValue | ExternalID
impl<'s> Composer<'s> for PEDef<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        match self {
            PEDef::EntityValue(entity_value) => entity_value.write(writer).await?,
            PEDef::ExternalID(external_id) => external_id.write(writer).await?,
        }
        Ok(())
    }
}

/// [75]   	ExternalID	   ::=   	'SYSTEM' S SystemLiteral | 'PUBLIC' S PubidLiteral S SystemLiteral
impl<'s> Composer<'s> for ExternalID<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        match self {
            ExternalID::SYSTEM { system_identifier } => {
                writer.write_all("SYSTEM".as_bytes()).await?;
                S.write(writer).await?;
                system_identifier.write(writer).await?;
            }
            ExternalID::PUBLIC {
                public_identifier,
                system_identifier,
            } => {
                writer.write_all("PUBLIC".as_bytes()).await?;
                S.write(writer).await?;
                public_identifier.write(writer).await?;
                S.write(writer).await?;
                system_identifier.write(writer).await?;
            }
        }
        Ok(())
    }
}

/// [76]   	NDataDecl	   ::=   	S 'NDATA' S Name
impl<'s> Composer<'s> for NDataDecl<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        S.write(writer).await?;
        writer.write_all("NDATA".as_bytes()).await?;
        S.write(writer).await?;
        self.0.write(writer).await?;
        Ok(())
    }
}

/// [77]   	TextDecl	   ::=   	'<?xml' VersionInfo? EncodingDecl S? '?>'
impl<'s> Composer<'s> for TextDecl<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("<?xml".as_bytes()).await?;
        if let Some(version_info) = &self.version_info {
            version_info.write(writer).await?;
        }
        self.encoding_decl.write(writer).await?;
        writer.write_all("?>".as_bytes()).await?;
        Ok(())
    }
}

/// [78]   	extParsedEnt	   ::=   	TextDecl? content
impl<'s> Composer<'s> for ExtParsedEnt<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        if let Some(text_decl) = &self.text_decl {
            text_decl.write(writer).await?;
        }
        self.content.write(writer).await?;
        Ok(())
    }
}

/// [80]   	EncodingDecl	   ::=   	S 'encoding' Eq ('"' EncName '"' | "'" EncName
impl<'s> Composer<'s> for EncodingDecl<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        S.write(writer).await?;
        writer.write_all("encoding".as_bytes()).await?;
        Eq.write(writer).await?;
        writer.write_all("\"".as_bytes()).await?;
        self.0.write(writer).await?;
        writer.write_all("\"".as_bytes()).await?;
        Ok(())
    }
}

/// [81]   	EncName	   ::=   	[A-Za-z] ([A-Za-z0-9._] | '-')*
impl<'s> Composer<'s> for EncName<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all(self.0.as_bytes()).await?;
        Ok(())
    }
}

/// [82]   	NotationDecl	   ::=   	'<!NOTATION' S Name S (ExternalID | PublicID) S? '>'
impl<'s> Composer<'s> for NotationDecl<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("<!NOTATION".as_bytes()).await?;
        S.write(writer).await?;
        self.name.write(writer).await?;
        S.write(writer).await?;
        match &self.id {
            NotationDeclID::External(external_id) => external_id.write(writer).await?,
            NotationDeclID::Public(public_id) => public_id.write(writer).await?,
        }
        writer.write_all(">".as_bytes()).await?;
        Ok(())
    }
}

/// [83]   	PublicID	   ::=   	'PUBLIC' S PubidLiteral
impl<'s> Composer<'s> for PublicID<'s> {
    async fn write<W>(&self, writer: &mut W) -> io::Result<()>
    where
        W: Unpin + AsyncWrite,
    {
        writer.write_all("PUBLIC".as_bytes()).await?;
        S.write(writer).await?;
        self.0.write(writer).await?;
        Ok(())
    }
}

/// [1]   	NSAttName	   ::=   	PrefixedAttName | DefaultAttName
impl<'s> Display for NSAttName<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match self {
            NSAttName::PrefixedAttName(prefixed_att_name) => prefixed_att_name.fmt(f)?,
            NSAttName::DefaultAttName => DefaultAttName.fmt(f)?,
        }
        Ok(())
    }
}

/// [2]   	PrefixedAttName	   ::=   	'xmlns:' NCName
impl<'s> Display for PrefixedAttName<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("xmlns:")?;
        self.0.fmt(f)?;
        Ok(())
    }
}

/// [3]   	DefaultAttName	   ::=   	'xmlns';
impl Display for DefaultAttName {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("xmlns")?;
        Ok(())
    }
}

/// [4]   	NCName	   ::=   	Name - (Char* ':' Char*)
impl<'s> Display for NCName<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str(self.0)?;
        Ok(())
    }
}

/// [7]   	QName	   ::=   	PrefixedName | UnprefixedName
impl<'s> Display for QName<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match self {
            QName::PrefixedName(prefixed_name) => prefixed_name.fmt(f)?,
            QName::UnprefixedName(unprefixed_name) => unprefixed_name.fmt(f)?,
        }
        Ok(())
    }
}

/// [8]   	PrefixedName	   ::=   	Prefix ':' LocalPart
impl<'s> Display for PrefixedName<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        self.prefix.fmt(f)?;
        f.write_str(":")?;
        self.local_part.fmt(f)?;
        Ok(())
    }
}

/// [9]   	UnprefixedName	   ::=   	LocalPart
impl<'s> Display for UnprefixedName<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        self.0.fmt(f)?;
        Ok(())
    }
}

/// [10]   	Prefix	   ::=   	NCName
impl<'s> Display for Prefix<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        self.0.fmt(f)?;
        Ok(())
    }
}

/// [11]   	LocalPart	   ::=   	NCName
impl<'s> Display for LocalPart<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        self.0.fmt(f)?;
        Ok(())
    }
}

// xml spec

/// [1]   	document	   ::=   	prolog element Misc*
impl<'s> Display for Document<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        self.prolog.fmt(f)?;
        self.element.fmt(f)?;
        for misc in &self.miscs {
            misc.fmt(f)?
        }
        Ok(())
    }
}

/// [2]   	Char	   ::=   	#x9 | #xA | #xD | [#x20-#xD7FF] | [#xE000-#xFFFD] | [#x10000-#x10FFFF]	/* any Unicode character, excluding the surrogate blocks, FFFE, and FFFF. */
impl Display for Char {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_char(self.0)?;
        Ok(())
    }
}

/// [3]   	S	   ::=   	(#x20 | #x9 | #xD | #xA)+
impl<'s> Display for S {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("\u{20}")?;
        Ok(())
    }
}

/// [4]   	NameStartChar	   ::=   	":" | [A-Z] | "_" | [a-z] | [#xC0-#xD6] | [#xD8-#xF6] | [#xF8-#x2FF] | [#x370-#x37D] | [#x37F-#x1FFF] | [#x200C-#x200D] | [#x2070-#x218F] | [#x2C00-#x2FEF] | [#x3001-#xD7FF] | [#xF900-#xFDCF] | [#xFDF0-#xFFFD] | [#x10000-#xEFFFF]
impl Display for NameStartChar {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_char(self.0)?;
        Ok(())
    }
}

/// [4a]   	NameChar	   ::=   	NameStartChar | "-" | "." | [0-9] | #xB7 | [#x0300-#x036F] | [#x203F-#x2040]
impl Display for NameChar {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_char(self.0)?;
        Ok(())
    }
}

/// [5]   	Name	   ::=   	NameStartChar (NameChar)*
impl<'s> Display for Name<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str(self.0)?;
        Ok(())
    }
}

/// [6]   	Names	   ::=   	Name (#x20 Name)*
impl<'s> Display for Names<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        let mut first = true;
        for name in &self.0 {
            if !first {
                f.write_str("\u{20}")?;
            }
            name.fmt(f)?;
            if first {
                first = false
            }
        }
        Ok(())
    }
}

/// [7]   	Nmtoken	   ::=   	(NameChar)+
impl<'s> Display for Nmtoken<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str(self.0)?;
        Ok(())
    }
}

/// [8]   	Nmtokens	   ::=   	Nmtoken (#x20 Nmtoken)*
impl<'s> Display for Nmtokens<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        let mut first = true;
        for nmtoken in &self.0 {
            if !first {
                f.write_str("\u{20}")?;
            }
            nmtoken.fmt(f)?;
            if first {
                first = false
            }
        }
        Ok(())
    }
}

/// [9]   	EntityValue	   ::=   	'"' ([^%&"] | PEReference | Reference)* '"'
///			|  "'" ([^%&'] | PEReference | Reference)* "'"
impl<'s> Display for EntityValue<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match self {
            EntityValue::DoubleQuoted(entity_value_data) => {
                f.write_str("\"")?;
                for entity_value_data in entity_value_data {
                    match entity_value_data {
                        EntityValueData::String(s) => f.write_str(s)?,
                        EntityValueData::PEReference(pe_reference) => pe_reference.fmt(f)?,
                        EntityValueData::Reference(reference) => reference.fmt(f)?,
                    }
                }
                f.write_str("\"")?;
            }
            EntityValue::SingleQuoted(entity_value_data) => {
                f.write_str("'")?;
                for entity_value_data in entity_value_data {
                    match entity_value_data {
                        EntityValueData::String(s) => f.write_str(s)?,
                        EntityValueData::PEReference(pe_reference) => pe_reference.fmt(f)?,
                        EntityValueData::Reference(reference) => reference.fmt(f)?,
                    }
                }
                f.write_str("'")?;
            }
        }
        Ok(())
    }
}

/// [10]   	AttValue	   ::=   	'"' ([^<&"] | Reference)* '"'
/// 			|  "'" ([^<&'] | Reference)* "'"
impl<'s> Display for AttValue<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match self {
            AttValue::DoubleQuoted(att_value_data) => {
                f.write_str("\"")?;
                for att_value_data in att_value_data {
                    match att_value_data {
                        AttValueData::String(s) => f.write_str(s)?,
                        AttValueData::Reference(reference) => reference.fmt(f)?,
                    }
                }
                f.write_str("\"")?;
            }
            AttValue::SingleQuoted(att_value_data) => {
                f.write_str("'")?;
                for att_value_data in att_value_data {
                    match att_value_data {
                        AttValueData::String(s) => f.write_str(s)?,
                        AttValueData::Reference(reference) => reference.fmt(f)?,
                    }
                }
                f.write_str("'")?;
            }
        }
        Ok(())
    }
}

/// [11]   	SystemLiteral	   ::=   	('"' [^"]* '"') | ("'" [^']* "'")
impl<'s> Display for SystemLiteral<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match self {
            SystemLiteral::DoubleQuoted(s) => {
                f.write_str("\"")?;
                f.write_str(s)?;
                f.write_str("\"")?;
            }
            SystemLiteral::SingleQuoted(s) => {
                f.write_str("'")?;
                f.write_str(s)?;
                f.write_str("'")?;
            }
        }
        Ok(())
    }
}

/// [12]   	PubidLiteral	   ::=   	'"' PubidChar* '"' | "'" (PubidChar - "'")* "'"
impl<'s> Display for PubidLiteral<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match self {
            PubidLiteral::DoubleQuoted(s) => {
                f.write_str("\"")?;
                f.write_str(s)?;
                f.write_str("\"")?;
            }
            PubidLiteral::SingleQuoted(s) => {
                f.write_str("'")?;
                f.write_str(s)?;
                f.write_str("'")?;
            }
        }
        Ok(())
    }
}

/// [13]   	PubidChar	   ::=   	#x20 | #xD | #xA | [a-zA-Z0-9] | [-'()+,./:=?;!*#@$_%]
impl Display for PubidChar {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_char(self.0)?;
        Ok(())
    }
}

/// [14]   	CharData	   ::=   	[^<&]* - ([^<&]* ']]>' [^<&]*)
impl<'s> Display for CharData<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str(self.0)?;
        Ok(())
    }
}

/// [15]    Comment	   ::=   	'<!--' ((Char - '-') | ('-' (Char - '-')))* '-->'
impl<'s> Display for Comment<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("<!--")?;
        f.write_str(self.0)?;
        f.write_str("-->")?;
        Ok(())
    }
}

/// [16]   	PI	   ::=   	'<?' PITarget (S (Char* - (Char* '?>' Char*)))? '?>'
impl<'s> Display for PI<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("<?")?;
        self.target.fmt(f)?;
        if let Some(instruction) = self.instruction {
            S.fmt(f)?;
            f.write_str(instruction)?;
        }
        f.write_str("?>")?;
        Ok(())
    }
}

/// [17]   	PITarget	   ::=   	Name - (('X' | 'x') ('M' | 'm') ('L' | 'l'))
impl<'s> Display for PITarget<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        self.0.fmt(f)?;
        Ok(())
    }
}

/// [18]   	CDSect	   ::=   	CDStart CData CDEnd
impl<'s> Display for CDSect<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        CDStart.fmt(f)?;
        self.0.fmt(f)?;
        CDEnd.fmt(f)?;
        Ok(())
    }
}

/// [19]   	CDStart	   ::=   	'<![CDATA['
impl Display for CDStart {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("<![CDATA[")?;
        Ok(())
    }
}

/// [20]   	CData	   ::=   	(Char* - (Char* ']]>' Char*))
impl<'s> Display for CData<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str(self.0)?;
        Ok(())
    }
}

/// [21]   	CDEnd	   ::=   	']]>'
impl Display for CDEnd {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("]]>")?;
        Ok(())
    }
}

/// [22]   	prolog	   ::=   	XMLDecl? Misc* (doctypedecl Misc*)?
impl<'s> Display for Prolog<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        if let Some(xml_decl) = &self.xml_decl {
            xml_decl.fmt(f)?;
        }
        for misc in &self.miscs {
            misc.fmt(f)?;
        }
        if let Some((doctype_decl, miscs)) = &self.doctype_decl {
            doctype_decl.fmt(f)?;
            for misc in miscs {
                misc.fmt(f)?;
            }
        }
        Ok(())
    }
}

/// [23]   	XMLDecl	   ::=   	'<?xml' VersionInfo EncodingDecl? SDDecl? S? '?>'
impl<'s> Display for XMLDecl<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("<?xml")?;
        self.version_info.fmt(f)?;
        if let Some(encoding_decl) = &self.encoding_decl {
            encoding_decl.fmt(f)?
        }
        if let Some(sd_decl) = &self.sd_decl {
            sd_decl.fmt(f)?
        }
        f.write_str("?>")?;
        Ok(())
    }
}

/// [24]   	VersionInfo	   ::=   	S 'version' Eq ("'" VersionNum "'" | '"' VersionNum '"')
impl Display for VersionInfo {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        S.fmt(f)?;
        f.write_str("version")?;
        Eq.fmt(f)?;
        match self {
            VersionInfo::SingleQuoted(version_num) => {
                f.write_str("'")?;
                version_num.fmt(f)?;
                f.write_str("'")?;
            }
            VersionInfo::DoubleQuoted(version_num) => {
                f.write_str("\"")?;
                version_num.fmt(f)?;
                f.write_str("\"")?;
            }
        }
        Ok(())
    }
}

/// [25]   	Eq	   ::=   	S? '=' S?
impl Display for Eq {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("=")?;
        Ok(())
    }
}

/// [26]   	VersionNum	   ::=   	'1.' [0-9]+
impl Display for VersionNum {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match self {
            VersionNum::One => f.write_str("1.0")?,
            VersionNum::OneDotOne => f.write_str("1.1")?,
        }
        Ok(())
    }
}

/// [27]   	Misc	   ::=   	Comment | PI | S
impl<'s> Display for Misc<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match self {
            Misc::Comment(comment) => comment.fmt(f)?,
            Misc::PI(pi) => pi.fmt(f)?,
            Misc::S => {}
        }
        Ok(())
    }
}

/// [16]   	doctypedecl	   ::=   	'<!DOCTYPE' S QName (S ExternalID)? S? ('[' (markupdecl | PEReference | S)* ']' S?)? '>'
/// [28]   	doctypedecl	   ::=   	'<!DOCTYPE' S Name (S ExternalID)? S? ('[' intSubset ']' S?)? '>'
impl<'s> Display for DoctypeDecl<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("<!DOCTYPE")?;
        S.fmt(f)?;
        self.name.fmt(f)?;
        if let Some(external_id) = &self.external_id {
            S.fmt(f)?;
            external_id.fmt(f)?;
        }
        if let Some(int_subset) = &self.int_subset {
            f.write_str("[")?;
            int_subset.fmt(f)?;
            f.write_str("]")?;
        }
        f.write_str(">")?;
        Ok(())
    }
}

/// [28a]   	DeclSep	   ::=   	PEReference | S
impl<'s> Display for DeclSep<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match self {
            DeclSep::PEReference(pe_reference) => pe_reference.fmt(f)?,
            DeclSep::S => S.fmt(f)?,
        }
        Ok(())
    }
}

/// [28b]   	intSubset	   ::=   	(markupdecl | DeclSep)*
impl<'s> Display for IntSubset<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        for declaration in &self.0 {
            match declaration {
                super::IntSubsetDeclaration::MarkupDecl(markup_decl) => markup_decl.fmt(f)?,
                super::IntSubsetDeclaration::DeclSep(decl_sep) => decl_sep.fmt(f)?,
            }
        }
        Ok(())
    }
}

/// [29]   	markupdecl	   ::=   	elementdecl | AttlistDecl | EntityDecl | NotationDecl | PI | Comment
impl<'s> Display for MarkupDecl<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match self {
            MarkupDecl::Elementdecl(elementdecl) => elementdecl.fmt(f)?,
            MarkupDecl::AttlistDecl(attlist_decl) => attlist_decl.fmt(f)?,
            MarkupDecl::EntityDecl(entity_decl) => entity_decl.fmt(f)?,
            MarkupDecl::NotationDecl(notation_decl) => notation_decl.fmt(f)?,
            MarkupDecl::PI(pi) => pi.fmt(f)?,
            MarkupDecl::Comment(comment) => comment.fmt(f)?,
        }
        Ok(())
    }
}

/// [30]   	extSubset	   ::=   	TextDecl? extSubsetDecl
impl<'s> Display for ExtSubset<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        if let Some(text_decl) = &self.text_decl {
            text_decl.fmt(f)?
        }
        self.ext_subset_decl.fmt(f)?;
        Ok(())
    }
}

/// [31]   	extSubsetDecl	   ::=   	( markupdecl | conditionalSect | DeclSep)*
impl<'s> Display for ExtSubsetDecl<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        for declaration in &self.0 {
            match declaration {
                ExtSubsetDeclaration::MarkupDecl(markup_decl) => markup_decl.fmt(f)?,
                ExtSubsetDeclaration::ConditionalSect(conditional_sect) => {
                    conditional_sect.fmt(f)?
                }
                ExtSubsetDeclaration::DeclSep(decl_sep) => decl_sep.fmt(f)?,
            }
        }
        Ok(())
    }
}

/// [32]   	SDDecl	   ::=   	S 'standalone' Eq (("'" ('yes' | 'no') "'") | ('"' ('yes' | 'no') '"'))
impl Display for SDDecl {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        S.fmt(f)?;
        f.write_str("standalone")?;
        Eq.fmt(f)?;
        match self {
            SDDecl::SingleQuoted(sd_decl) => {
                f.write_str("'")?;
                match sd_decl {
                    true => f.write_str("yes")?,
                    false => f.write_str("no")?,
                }
                f.write_str("'")?;
            }
            SDDecl::DoubleQuoted(sd_decl) => {
                f.write_str("\"")?;
                match sd_decl {
                    true => f.write_str("yes")?,
                    false => f.write_str("no")?,
                }
                f.write_str("\"")?;
            }
        }
        Ok(())
    }
}

// (Productions 33 through 38 have been removed.)

/// [39]   	element	   ::=   	EmptyElemTag | STag content ETag
impl<'s> Display for Element<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match self {
            Element::Empty(empty_elem_tag) => empty_elem_tag.fmt(f)?,
            Element::NotEmpty(s_tag, content, e_tag) => {
                s_tag.fmt(f)?;
                content.fmt(f)?;
                e_tag.fmt(f)?;
            }
        }
        Ok(())
    }
}

/// [12]   	STag	   ::=   	'<' QName (S Attribute)* S? '>'
/// [40]   	STag	   ::=   	'<' Name (S Attribute)* S? '>'
impl<'s> Display for STag<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("<")?;
        self.name.fmt(f)?;
        for attribute in &self.attributes {
            S.fmt(f)?;
            attribute.fmt(f)?;
        }
        f.write_str(">")?;
        Ok(())
    }
}

/// [15]   	Attribute	   ::=   	NSAttName Eq AttValue | QName Eq AttValue
impl<'s> Display for Attribute<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match self {
            Attribute::NamespaceDeclaration { ns_name, value } => {
                ns_name.fmt(f)?;
                Eq.fmt(f)?;
                value.fmt(f)?;
            }
            Attribute::Attribute { name, value } => {
                name.fmt(f)?;
                Eq.fmt(f)?;
                value.fmt(f)?;
            }
        }
        Ok(())
    }
}

/// [13]   	ETag	   ::=   	'</' QName S? '>'
impl<'s> Display for ETag<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("</")?;
        self.name.fmt(f)?;
        f.write_str(">")?;
        Ok(())
    }
}

/// [43]   	content	   ::=   	CharData? ((element | Reference | CDSect | PI | Comment) CharData?)*
impl<'s> Display for Content<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        if let Some(char_data) = &self.char_data {
            char_data.fmt(f)?;
        }
        for (content, char_data) in &self.content {
            match content {
                ContentItem::Element(element) => element.fmt(f)?,
                ContentItem::Reference(reference) => reference.fmt(f)?,
                ContentItem::CDSect(cd_sect) => cd_sect.fmt(f)?,
                ContentItem::PI(pi) => pi.fmt(f)?,
                ContentItem::Comment(comment) => comment.fmt(f)?,
                // TODO: verify no split chardata
                // _ => todo!("verify no split chardata"),
            }
            if let Some(char_data) = char_data {
                char_data.fmt(f)?;
            }
        }
        Ok(())
    }
}

/// [14]   	EmptyElemTag	   ::=   	'<' QName (S Attribute)* S? '/>'
impl<'s> Display for EmptyElemTag<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("<")?;
        self.name.fmt(f)?;
        for attribute in &self.attributes {
            S.fmt(f)?;
            attribute.fmt(f)?;
        }
        f.write_str("/>")?;
        Ok(())
    }
}

/// [17]   	elementdecl	   ::=   	'<!ELEMENT' S QName S contentspec S? '>'
impl<'s> Display for Elementdecl<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("<!ELEMENT")?;
        S.fmt(f)?;
        self.name.fmt(f)?;
        S.fmt(f)?;
        self.contentspec.fmt(f)?;
        f.write_str(">")?;
        Ok(())
    }
}

/// [46]   	contentspec	   ::=   	'EMPTY' | 'ANY' | Mixed | children
impl<'s> Display for Contentspec<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match self {
            Contentspec::Empty => f.write_str("EMPTY")?,
            Contentspec::Any => f.write_str("ANY")?,
            Contentspec::Mixed(mixed) => mixed.fmt(f)?,
            Contentspec::Children(children) => children.fmt(f)?,
        }
        Ok(())
    }
}

/// Occurence ::= ('?' | '*' | '+')?
impl Display for Occurence {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match self {
            Occurence::Once => {}
            Occurence::Optional => f.write_str("?")?,
            Occurence::Many0 => f.write_str("*")?,
            Occurence::Many1 => f.write_str("+")?,
        }
        Ok(())
    }
}

/// [47]   	children	   ::=   	(choice | seq) ('?' | '*' | '+')?
impl<'s> Display for Children<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match &self.kind {
            ChildrenKind::Choice(choice) => choice.fmt(f)?,
            ChildrenKind::Seq(seq) => seq.fmt(f)?,
        }
        self.occurence.fmt(f)?;
        Ok(())
    }
}

/// [18]   	cp	   ::=   	(QName | choice | seq) ('?' | '*' | '+')?
impl<'s> Display for Cp<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match &self.kind {
            CpKind::Name(q_name) => q_name.fmt(f)?,
            CpKind::Choice(choice) => choice.fmt(f)?,
            CpKind::Seq(seq) => seq.fmt(f)?,
        }
        self.occurence.fmt(f)?;
        Ok(())
    }
}

/// [49]   	choice	   ::=   	'(' S? cp ( S? '|' S? cp )+ S? ')'
impl<'s> Display for Choice<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("(")?;
        let mut first = true;
        for cp in &self.0 {
            if !first {
                f.write_str("|")?;
            }
            cp.fmt(f)?;
            if first {
                first = false
            }
        }
        f.write_str(")")?;
        Ok(())
    }
}

/// [50]   	seq	   ::=   	'(' S? cp ( S? ',' S? cp )* S? ')'
impl<'s> Display for Seq<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("(")?;
        let mut first = true;
        for cp in &self.0 {
            if !first {
                f.write_str(",")?;
            }
            cp.fmt(f)?;
            if first {
                first = false
            }
        }
        f.write_str(")")?;
        Ok(())
    }
}

/// [19]   	Mixed	   ::=   	'(' S? '#PCDATA' (S? '|' S? QName)* S? ')*' | '(' S? '#PCDATA' S? ')'
impl<'s> Display for Mixed<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("(#PCDATA")?;
        if !self.0.is_empty() {
            for q_name in &self.0 {
                f.write_str("|")?;
                q_name.fmt(f)?;
            }
            f.write_str(")*")?;
        } else {
            f.write_str(")")?;
        }
        Ok(())
    }
}

/// [20]   	AttlistDecl	   ::=   	'<!ATTLIST' S QName AttDef* S? '>'
impl<'s> Display for AttlistDecl<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("<!ATTLIST")?;
        S.fmt(f)?;
        self.element_type.fmt(f)?;
        for att_def in &self.att_defs {
            att_def.fmt(f)?;
        }
        f.write_str(">")?;
        Ok(())
    }
}

/// [21]   	AttDef	   ::=   	S (QName | NSAttName) S AttType S DefaultDecl
impl<'s> Display for AttDef<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        S.fmt(f)?;
        match &self.name {
            AttDefName::QName(q_name) => q_name.fmt(f)?,
            AttDefName::NSAttName(ns_att_name) => ns_att_name.fmt(f)?,
        }
        S.fmt(f)?;
        self.att_type.fmt(f)?;
        S.fmt(f)?;
        self.default_decl.fmt(f)?;
        Ok(())
    }
}

/// [54]   	AttType	   ::=   	StringType | TokenizedType | EnumeratedType
impl<'s> Display for AttType<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match self {
            AttType::StringType => StringType.fmt(f)?,
            AttType::TokenizedType(tokenized_type) => tokenized_type.fmt(f)?,
            AttType::EnumeratedType(enumerated_type) => enumerated_type.fmt(f)?,
        }
        Ok(())
    }
}

/// [55]   	StringType	   ::=   	'CDATA'
impl Display for StringType {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("CDATA")?;
        Ok(())
    }
}

/// [56]   	TokenizedType	   ::=   	'ID' | 'IDREF' | 'IDREFS' | 'ENTITY' | 'ENTITIES' | 'NMTOKEN' | 'NMTOKENS'
impl Display for TokenizedType {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match self {
            TokenizedType::ID => f.write_str("ID")?,
            TokenizedType::IDRef => f.write_str("IDREF")?,
            TokenizedType::IDRefs => f.write_str("IDREFS")?,
            TokenizedType::Entity => f.write_str("ENTITY")?,
            TokenizedType::Entities => f.write_str("ENTITIES")?,
            TokenizedType::NMToken => f.write_str("NMTOKEN")?,
            TokenizedType::NMTokens => f.write_str("NMTOKENS")?,
        }
        Ok(())
    }
}

/// [57]   	EnumeratedType	   ::=   	NotationType | Enumeration
impl<'s> Display for EnumeratedType<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match self {
            EnumeratedType::NotationType(notation_type) => notation_type.fmt(f)?,
            EnumeratedType::Enumeration(enumeration) => enumeration.fmt(f)?,
        }
        Ok(())
    }
}

/// [58]   	NotationType	   ::=   	'NOTATION' S '(' S? Name (S? '|' S? Name)* S? ')'
impl<'s> Display for NotationType<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("NOTATION")?;
        S.fmt(f)?;
        f.write_str("(")?;
        let mut first = true;
        for name in &self.0 {
            if !first {
                f.write_str("|")?;
            }
            name.fmt(f)?;
            if first {
                first = false
            }
        }
        f.write_str(")")?;
        Ok(())
    }
}

/// [59]   	Enumeration	   ::=   	'(' S? Nmtoken (S? '|' S? Nmtoken)* S? ')'
impl<'s> Display for Enumeration<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("(")?;
        let mut first = true;
        for nm_token in &self.0 {
            if !first {
                f.write_str("|")?;
            }
            nm_token.fmt(f)?;
            if first {
                first = false
            }
        }
        f.write_str(")")?;
        Ok(())
    }
}

/// [60]   	DefaultDecl	   ::=   	'#REQUIRED' | '#IMPLIED' | (('#FIXED' S)? AttValue)
impl<'s> Display for DefaultDecl<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match self {
            DefaultDecl::Required => f.write_str("#REQUIRED")?,
            DefaultDecl::Implied => f.write_str("#IMPLIED")?,
            DefaultDecl::Fixed(fixed, att_value) => {
                if *fixed {
                    f.write_str("#FIXED")?;
                    S.fmt(f)?;
                }
                att_value.fmt(f)?
            }
        }
        Ok(())
    }
}

/// [61]   	conditionalSect	   ::=   	includeSect | ignoreSect
impl<'s> Display for ConditionalSect<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match self {
            ConditionalSect::IncludeSect(include_sect) => include_sect.fmt(f)?,
            ConditionalSect::IgnoreSect(ignore_sect) => ignore_sect.fmt(f)?,
        }
        Ok(())
    }
}

/// [62]   	includeSect	   ::=   	'<![' S? 'INCLUDE' S? '[' extSubsetDecl ']]>'
impl<'s> Display for IncludeSect<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("<![INCLUDE[")?;
        self.0.fmt(f)?;
        f.write_str("]]>")?;
        Ok(())
    }
}

/// [63]   	ignoreSect	   ::=   	'<![' S? 'IGNORE' S? '[' ignoreSectContents* ']]>'
impl<'s> Display for IgnoreSect<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("<![IGNORE[")?;
        for ignore_sect_contents in &self.0 {
            ignore_sect_contents.fmt(f)?;
        }
        f.write_str("]]>")?;
        Ok(())
    }
}

/// [64]   	ignoreSectContents	   ::=   	Ignore ('<![' ignoreSectContents ']]>' Ignore)*
impl<'s> Display for IgnoreSectContents<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        self.ignore.fmt(f)?;
        for (ignore_sect_contents, ignore) in &self.ignore_list {
            f.write_str("<![")?;
            ignore_sect_contents.fmt(f)?;
            f.write_str("]]>")?;
            ignore.fmt(f)?;
        }
        Ok(())
    }
}

/// [65]   	Ignore	   ::=   	Char* - (Char* ('<![' | ']]>') Char*)
impl<'s> Display for Ignore<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str(self.0)?;
        Ok(())
    }
}

/// [66]   	CharRef	   ::=   	'&#' [0-9]+ ';' | '&#x' [0-9a-fA-F]+ ';'
impl<'s> Display for CharRef<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match self {
            CharRef::Decimal(decimal) => {
                f.write_str("&#")?;
                f.write_str(decimal)?;
                f.write_str(";")?;
            }
            CharRef::Hexadecimal(hexadecimal) => {
                f.write_str("&#x")?;
                f.write_str(hexadecimal)?;
                f.write_str(";")?;
            }
        }
        Ok(())
    }
}

/// [67]   	Reference	   ::=   	EntityRef | CharRef
impl<'s> Display for Reference<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match self {
            Reference::EntityRef(entity_ref) => entity_ref.fmt(f)?,
            Reference::CharRef(char_ref) => char_ref.fmt(f)?,
        }
        Ok(())
    }
}

/// [68]   	EntityRef	   ::=   	'&' Name ';'
impl<'s> Display for EntityRef<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("&")?;
        self.0.fmt(f)?;
        f.write_str(";")?;
        Ok(())
    }
}

/// [69]   	PEReference	   ::=   	'%' Name ';'
impl<'s> Display for PEReference<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("%")?;
        self.0.fmt(f)?;
        f.write_str(";")?;
        Ok(())
    }
}

/// [70]   	EntityDecl	   ::=   	GEDecl | PEDecl
impl<'s> Display for EntityDecl<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match self {
            EntityDecl::GEDecl(ge_decl) => ge_decl.fmt(f)?,
            EntityDecl::PEDecl(pe_decl) => pe_decl.fmt(f)?,
        }
        Ok(())
    }
}

/// [71]   	GEDecl	   ::=   	'<!ENTITY' S Name S EntityDef S? '>'
impl<'s> Display for GEDecl<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("<!ENTITY")?;
        S.fmt(f)?;
        self.name.fmt(f)?;
        S.fmt(f)?;
        self.entity_def.fmt(f)?;
        f.write_str(">")?;
        Ok(())
    }
}

/// [72]   	PEDecl	   ::=   	'<!ENTITY' S '%' S Name S PEDef S? '>'
impl<'s> Display for PEDecl<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("<!ENTITY")?;
        S.fmt(f)?;
        f.write_str("%")?;
        S.fmt(f)?;
        self.name.fmt(f)?;
        S.fmt(f)?;
        self.pe_def.fmt(f)?;
        f.write_str(">")?;
        Ok(())
    }
}

/// [73]   	EntityDef	   ::=   	EntityValue | (ExternalID NDataDecl?)
impl<'s> Display for EntityDef<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match self {
            EntityDef::EntityValue(entity_value) => entity_value.fmt(f)?,
            EntityDef::ExternalID {
                external_id,
                n_data_decl,
            } => {
                external_id.fmt(f)?;
                if let Some(n_data_decl) = n_data_decl {
                    n_data_decl.fmt(f)?;
                }
            }
        }
        Ok(())
    }
}

/// [74]   	PEDef	   ::=   	EntityValue | ExternalID
impl<'s> Display for PEDef<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match self {
            PEDef::EntityValue(entity_value) => entity_value.fmt(f)?,
            PEDef::ExternalID(external_id) => external_id.fmt(f)?,
        }
        Ok(())
    }
}

/// [75]   	ExternalID	   ::=   	'SYSTEM' S SystemLiteral | 'PUBLIC' S PubidLiteral S SystemLiteral
impl<'s> Display for ExternalID<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        match self {
            ExternalID::SYSTEM { system_identifier } => {
                f.write_str("SYSTEM")?;
                S.fmt(f)?;
                system_identifier.fmt(f)?;
            }
            ExternalID::PUBLIC {
                public_identifier,
                system_identifier,
            } => {
                f.write_str("PUBLIC")?;
                S.fmt(f)?;
                public_identifier.fmt(f)?;
                S.fmt(f)?;
                system_identifier.fmt(f)?;
            }
        }
        Ok(())
    }
}

/// [76]   	NDataDecl	   ::=   	S 'NDATA' S Name
impl<'s> Display for NDataDecl<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        S.fmt(f)?;
        f.write_str("NDATA")?;
        S.fmt(f)?;
        self.0.fmt(f)?;
        Ok(())
    }
}

/// [77]   	TextDecl	   ::=   	'<?xml' VersionInfo? EncodingDecl S? '?>'
impl<'s> Display for TextDecl<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("<?xml")?;
        if let Some(version_info) = &self.version_info {
            version_info.fmt(f)?;
        }
        self.encoding_decl.fmt(f)?;
        f.write_str("?>")?;
        Ok(())
    }
}

/// [78]   	extParsedEnt	   ::=   	TextDecl? content
impl<'s> Display for ExtParsedEnt<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        if let Some(text_decl) = &self.text_decl {
            text_decl.fmt(f)?;
        }
        self.content.fmt(f)?;
        Ok(())
    }
}

/// [80]   	EncodingDecl	   ::=   	S 'encoding' Eq ('"' EncName '"' | "'" EncName
impl<'s> Display for EncodingDecl<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        S.fmt(f)?;
        f.write_str("encoding")?;
        Eq.fmt(f)?;
        f.write_str("\"")?;
        self.0.fmt(f)?;
        f.write_str("\"")?;
        Ok(())
    }
}

/// [81]   	EncName	   ::=   	[A-Za-z] ([A-Za-z0-9._] | '-')*
impl<'s> Display for EncName<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str(self.0)?;
        Ok(())
    }
}

/// [82]   	NotationDecl	   ::=   	'<!NOTATION' S Name S (ExternalID | PublicID) S? '>'
impl<'s> Display for NotationDecl<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("<!NOTATION")?;
        S.fmt(f)?;
        self.name.fmt(f)?;
        S.fmt(f)?;
        match &self.id {
            NotationDeclID::External(external_id) => external_id.fmt(f)?,
            NotationDeclID::Public(public_id) => public_id.fmt(f)?,
        }
        f.write_str(">")?;
        Ok(())
    }
}

/// [83]   	PublicID	   ::=   	'PUBLIC' S PubidLiteral
impl<'s> Display for PublicID<'s> {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str("PUBLIC")?;
        S.fmt(f)?;
        self.0.fmt(f)?;
        Ok(())
    }
}