use std::io;

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

use super::{
    AttValue, AttValueData, CDEnd, CDSect, CDStart, CData, Char, CharData, Comment, DeclSep,
    DefaultAttName, DoctypeDecl, Document, Element, EntityValue, EntityValueData, Eq, ExtSubset,
    ExtSubsetDecl, IntSubset, LocalPart, MarkupDecl, Misc, NCName, NSAttName, Name, NameChar,
    NameStartChar, Names, Nmtoken, Nmtokens, PITarget, Prefix, PrefixedAttName, PrefixedName,
    Prolog, PubidChar, PubidLiteral, QName, SDDecl, SystemLiteral, UnprefixedName, VersionInfo,
    VersionNum, XMLDecl, PI, S,
};

/// Compact Composer trait, can create different trait later for pretty composition
pub trait Composer<'s> {
    async fn write<W>(&self, writer: &mut W) -> 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.0.write(writer).await?;
        self.1.write(writer).await?;
        for misc in &self.2 {
            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.0 {
            xml_decl.write(writer).await?;
        }
        for misc in &self.1 {
            misc.write(writer).await?;
        }
        if let Some((doctype_decl, miscs)) = &self.2 {
            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 {
            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 {
            match declaration {
                super::ExtSubsetDeclaration::MarkupDecl(markup_decl) => {
                    markup_decl.write(writer).await?
                }
                super::ExtSubsetDeclaration::ConditionalSect(conditional_sect) => {
                    conditional_sect.write(writer).await?
                }
                super::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(())
    }
}

/// [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,
    {
        todo!()
    }
}