use std::io::Cursor;

use quick_xml::Error as QError;
use quick_xml::events::{Event, BytesEnd, BytesStart, BytesText};
use quick_xml::writer::{ElementWriter, Writer};
use quick_xml::name::PrefixDeclaration;
use tokio::io::AsyncWrite;
use super::types::*;


//-------------- TRAITS ----------------------

/// Basic encode trait to make a type encodable
pub trait QuickWritable<C: Context> {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError>; 
}

/// Encoding context
pub trait Context: Extension {
    fn child(&self) -> Self;
    fn create_dav_element(&self, name: &str) -> BytesStart;
    async fn hook_error(&self, err: &Self::Error, xml: &mut Writer<impl AsyncWrite+Unpin>) -> Result<(), QError>;
    async fn hook_property(&self, prop: &Self::Property, xml: &mut Writer<impl AsyncWrite+Unpin>) -> Result<(), QError>;
    async fn hook_propertyrequest(&self, prop: &Self::PropertyRequest, xml: &mut Writer<impl AsyncWrite+Unpin>) -> Result<(), QError>;
    async fn hook_resourcetype(&self, prop: &Self::ResourceType, xml: &mut Writer<impl AsyncWrite+Unpin>) -> Result<(), QError>;
}

/// -------------- NoExtension Encoding Context
impl Context for NoExtension {
    fn child(&self) -> Self {
        Self { root: false }
    }
    fn create_dav_element(&self, name: &str) -> BytesStart {
        let mut start = BytesStart::new(format!("D:{}", name));
        if self.root {
            start.push_attribute(("xmlns:D", "DAV:"));
        }
        start
    }
    async fn hook_error(&self, _err: &Disabled, _xml: &mut Writer<impl AsyncWrite+Unpin>) -> Result<(), QError> {
        unreachable!();
    }
    async fn hook_property(&self, _prop: &Disabled, _xml: &mut Writer<impl AsyncWrite+Unpin>) -> Result<(), QError> {
        unreachable!();
    }
    async fn hook_propertyrequest(&self, _prop: &Disabled, _xml: &mut Writer<impl AsyncWrite+Unpin>) -> Result<(), QError> {
        unreachable!();
    }
    async fn hook_resourcetype(&self, _restype: &Disabled, _xml: &mut Writer<impl AsyncWrite+Unpin>) -> Result<(), QError> {
        unreachable!();
    }
}


//--------------------- ENCODING --------------------

// --- XML ROOTS

/// PROPFIND REQUEST
impl<C: Context> QuickWritable<C> for PropFind<C> {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        let start = ctx.create_dav_element("propfind");
        let end = start.to_end();
        let ctx = ctx.child();

        xml.write_event_async(Event::Start(start.clone())).await?;
        match self {
            Self::PropName => xml.write_event_async(Event::Empty(ctx.create_dav_element("propname"))).await?,
            Self::AllProp(maybe_include) => {
                xml.write_event_async(Event::Empty(ctx.create_dav_element("allprop"))).await?;
                if let Some(include) = maybe_include {
                    include.write(xml, ctx.child()).await?;
                }
            },
            Self::Prop(propname) => propname.write(xml, ctx.child()).await?,
        }
        xml.write_event_async(Event::End(end)).await
    }
}

/// PROPPATCH REQUEST
impl<C: Context> QuickWritable<C> for PropertyUpdate<C> {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        let start = ctx.create_dav_element("propertyupdate");
        let end = start.to_end();

        xml.write_event_async(Event::Start(start.clone())).await?;
        for update in self.0.iter() {
            update.write(xml, ctx.child()).await?;
        }
        xml.write_event_async(Event::End(end)).await
    }
}


/// PROPFIND RESPONSE, PROPPATCH RESPONSE, COPY RESPONSE, MOVE RESPONSE
/// DELETE RESPONSE, 
impl<C: Context> QuickWritable<C> for Multistatus<C> {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        let start = ctx.create_dav_element("multistatus");
        let end = start.to_end();

        xml.write_event_async(Event::Start(start.clone())).await?;
        for response in self.responses.iter() {
            response.write(xml, ctx.child()).await?;
        }
        if let Some(description) = &self.responsedescription {
            description.write(xml, ctx.child()).await?;
        }

        xml.write_event_async(Event::End(end)).await?;
        Ok(())
    }
}

/// LOCK REQUEST
impl<C: Context> QuickWritable<C> for LockInfo {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        let start = ctx.create_dav_element("lockinfo");
        let end = start.to_end();

        xml.write_event_async(Event::Start(start.clone())).await?;
        self.lockscope.write(xml, ctx.child()).await?;
        self.locktype.write(xml, ctx.child()).await?;
        if let Some(owner) = &self.owner {
            owner.write(xml, ctx.child()).await?;
        }
        xml.write_event_async(Event::End(end)).await
    }
}

/// SOME LOCK RESPONSES
impl<C: Context> QuickWritable<C> for PropValue<C> {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        let start = ctx.create_dav_element("prop");
        let end = start.to_end();

        xml.write_event_async(Event::Start(start.clone())).await?;
        for propval in &self.0 {
            propval.write(xml, ctx.child()).await?;
        }
        xml.write_event_async(Event::End(end)).await
    }
}

// --- XML inner elements
impl<C: Context> QuickWritable<C> for PropertyUpdateItem<C> {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        match self {
            Self::Set(set) => set.write(xml, ctx).await,
            Self::Remove(rm) => rm.write(xml, ctx).await,
        }
    }
}

impl<C: Context> QuickWritable<C> for Set<C> {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        let start = ctx.create_dav_element("set");
        let end = start.to_end();
        xml.write_event_async(Event::Start(start.clone())).await?;
        self.0.write(xml, ctx.child()).await?;
        xml.write_event_async(Event::End(end)).await
    }
}

impl<C: Context> QuickWritable<C> for Remove<C> {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        let start = ctx.create_dav_element("remove");
        let end = start.to_end();
        xml.write_event_async(Event::Start(start.clone())).await?;
        self.0.write(xml, ctx.child()).await?;
        xml.write_event_async(Event::End(end)).await
    }
}


impl<C: Context> QuickWritable<C> for AnyProp<C> {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        match self {
            Self::Name(propname) => propname.write(xml, ctx).await,
            Self::Value(propval) => propval.write(xml, ctx).await,
        }
    }
}

impl<C: Context> QuickWritable<C> for PropName<C> {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        let start = ctx.create_dav_element("prop");
        let end = start.to_end();

        xml.write_event_async(Event::Start(start.clone())).await?;
        for propname in &self.0 {
            propname.write(xml, ctx.child()).await?;
        }
        xml.write_event_async(Event::End(end)).await
    }
}


impl<C: Context> QuickWritable<C> for Href {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        let start = ctx.create_dav_element("href");
        let end = start.to_end();

        xml.write_event_async(Event::Start(start.clone())).await?;
        xml.write_event_async(Event::Text(BytesText::new(&self.0))).await?;
        xml.write_event_async(Event::End(end)).await?;

        Ok(())
    }
}

impl<C: Context> QuickWritable<C> for Response<C> {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        let start = ctx.create_dav_element("response");
        let end = start.to_end();

        xml.write_event_async(Event::Start(start.clone())).await?;
        self.href.write(xml, ctx.child()).await?; 
        self.status_or_propstat.write(xml, ctx.child()).await?;
        if let Some(error) = &self.error {
            error.write(xml, ctx.child()).await?;
        }
        if let Some(responsedescription) = &self.responsedescription {
            responsedescription.write(xml, ctx.child()).await?;
        }
        if let Some(location) = &self.location {
            location.write(xml, ctx.child()).await?;
        }
        xml.write_event_async(Event::End(end)).await?;

        Ok(())
    }
}

impl<C: Context> QuickWritable<C> for StatusOrPropstat<C> {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        match self {
            Self::Status(status) => status.write(xml, ctx.child()).await,
            Self::PropStat(propstat_list) => {
                for propstat in propstat_list.iter() {
                    propstat.write(xml, ctx.child()).await?;
                }

                Ok(())
            }
        }
    }
}

impl<C: Context> QuickWritable<C> for Status {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        let start = ctx.create_dav_element("status");
        let end = start.to_end();

        xml.write_event_async(Event::Start(start.clone())).await?;

        let txt = format!("HTTP/1.1 {} {}", self.0.as_str(), self.0.canonical_reason().unwrap_or("No reason"));
        xml.write_event_async(Event::Text(BytesText::new(&txt))).await?;

        xml.write_event_async(Event::End(end)).await?;

        Ok(())
    }
}

impl<C: Context> QuickWritable<C> for ResponseDescription {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        let start = ctx.create_dav_element("responsedescription");
        let end = start.to_end();

        xml.write_event_async(Event::Start(start.clone())).await?;
        xml.write_event_async(Event::Text(BytesText::new(&self.0))).await?;
        xml.write_event_async(Event::End(end)).await?;

        Ok(())
    }
}

impl<C: Context> QuickWritable<C> for Location {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        let start = ctx.create_dav_element("location");
        let end = start.to_end();

        xml.write_event_async(Event::Start(start.clone())).await?;
        self.0.write(xml, ctx.child()).await?;
        xml.write_event_async(Event::End(end)).await?;

        Ok(())
    }
}

impl<C: Context> QuickWritable<C> for PropStat<C> {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        let start = ctx.create_dav_element("propstat");
        let end = start.to_end();

        xml.write_event_async(Event::Start(start.clone())).await?;
        self.prop.write(xml, ctx.child()).await?;
        self.status.write(xml, ctx.child()).await?;
        if let Some(error) = &self.error {
            error.write(xml, ctx.child()).await?;
        }
        if let Some(description) = &self.responsedescription {
            description.write(xml, ctx.child()).await?;
        }
        xml.write_event_async(Event::End(end)).await?;

        Ok(())
    }
}

impl<C: Context> QuickWritable<C> for Property<C> {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        use Property::*;
        match self {
            CreationDate(date) => {
                // <D:creationdate>1997-12-01T17:42:21-08:00</D:creationdate>
                let start = ctx.create_dav_element("creationdate");
                let end = start.to_end();

                xml.write_event_async(Event::Start(start.clone())).await?;
                xml.write_event_async(Event::Text(BytesText::new(&date.to_rfc3339()))).await?;
                xml.write_event_async(Event::End(end)).await?;
            },
            DisplayName(name) => {
                // <D:displayname>Example collection</D:displayname>
                let start = ctx.create_dav_element("displayname");
                let end = start.to_end();

                xml.write_event_async(Event::Start(start.clone())).await?;
                xml.write_event_async(Event::Text(BytesText::new(name))).await?;
                xml.write_event_async(Event::End(end)).await?;
            },
            GetContentLanguage(lang) => {
                let start = ctx.create_dav_element("getcontentlanguage");
                let end = start.to_end();

                xml.write_event_async(Event::Start(start.clone())).await?;
                xml.write_event_async(Event::Text(BytesText::new(lang))).await?;
                xml.write_event_async(Event::End(end)).await?;
            },
            GetContentLength(len) => {
                // <D:getcontentlength>4525</D:getcontentlength>
                let start = ctx.create_dav_element("getcontentlength");
                let end = start.to_end();

                xml.write_event_async(Event::Start(start.clone())).await?;
                xml.write_event_async(Event::Text(BytesText::new(&len.to_string()))).await?;
                xml.write_event_async(Event::End(end)).await?;
            },
            GetContentType(ct) => {
                // <D:getcontenttype>text/html</D:getcontenttype>
                let start = ctx.create_dav_element("getcontenttype");
                let end = start.to_end();

                xml.write_event_async(Event::Start(start.clone())).await?;
                xml.write_event_async(Event::Text(BytesText::new(&ct))).await?;
                xml.write_event_async(Event::End(end)).await?;
            },
            GetEtag(et) => {
                // <D:getetag>"zzyzx"</D:getetag>
                let start = ctx.create_dav_element("getetag");
                let end = start.to_end();

                xml.write_event_async(Event::Start(start.clone())).await?;
                xml.write_event_async(Event::Text(BytesText::new(et))).await?;
                xml.write_event_async(Event::End(end)).await?;
            },
            GetLastModified(date) => {
                // <D:getlastmodified>Mon, 12 Jan 1998 09:25:56 GMT</D:getlastmodified>
                let start = ctx.create_dav_element("getlastmodified");
                let end = start.to_end();

                xml.write_event_async(Event::Start(start.clone())).await?;
                xml.write_event_async(Event::Text(BytesText::new(&date.to_rfc2822()))).await?;
                xml.write_event_async(Event::End(end)).await?;
            },
            LockDiscovery(many_locks) => {
                // <D:lockdiscovery><D:activelock> ... </D:activelock></D:lockdiscovery>
                let start = ctx.create_dav_element("lockdiscovery");
                let end = start.to_end();

                xml.write_event_async(Event::Start(start.clone())).await?;
                for lock in many_locks.iter() {
                    lock.write(xml, ctx.child()).await?;
                }
                xml.write_event_async(Event::End(end)).await?;
            },
            ResourceType(many_types) => {
                // <D:resourcetype><D:collection/></D:resourcetype>
                
                // <D:resourcetype/>
                
                // <x:resourcetype xmlns:x="DAV:">
                //   <x:collection/>
                //   <f:search-results xmlns:f="http://www.example.com/ns"/>
                // </x:resourcetype>
    
                let start = ctx.create_dav_element("resourcetype");
                if many_types.is_empty() {
                    xml.write_event_async(Event::Empty(start)).await?;
                } else {
                    let end = start.to_end();
                    xml.write_event_async(Event::Start(start.clone())).await?;
                    for restype in many_types.iter() {
                        restype.write(xml, ctx.child()).await?;
                    }
                    xml.write_event_async(Event::End(end)).await?;
                }
            },
            SupportedLock(many_entries) => {
                // <D:supportedlock/>

                //  <D:supportedlock> <D:lockentry> ... </D:lockentry> </D:supportedlock>

                let start = ctx.create_dav_element("supportedlock");
                if many_entries.is_empty() {
                    xml.write_event_async(Event::Empty(start)).await?;
                } else {
                    let end = start.to_end();
                    xml.write_event_async(Event::Start(start.clone())).await?;
                    for entry in many_entries.iter() {
                        entry.write(xml, ctx.child()).await?;
                    }
                    xml.write_event_async(Event::End(end)).await?;
                }
            },
            Extension(inner) => {
                ctx.hook_property(inner, xml).await?;
            },
        };
        Ok(())
    }
}

impl<C: Context> QuickWritable<C> for ResourceType<C> {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        match self {
            Self::Collection => xml.write_event_async(Event::Empty(ctx.create_dav_element("collection"))).await,
            Self::Extension(inner) => ctx.hook_resourcetype(inner, xml).await,
        }
    }
}

impl<C: Context> QuickWritable<C> for Include<C> {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        let start = ctx.create_dav_element("include");
        let end = start.to_end();

        xml.write_event_async(Event::Start(start.clone())).await?;  
        for prop in self.0.iter() {
            prop.write(xml, ctx.child()).await?;
        }
        xml.write_event_async(Event::End(end)).await
    }
}

impl<C: Context> QuickWritable<C> for PropertyRequest<C> {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        use PropertyRequest::*;
        let mut atom = async |c| xml.write_event_async(Event::Empty(ctx.create_dav_element(c))).await;

        match self {
            CreationDate => atom("creationdate").await,
            DisplayName => atom("displayname").await,
            GetContentLanguage => atom("getcontentlanguage").await,
            GetContentLength => atom("getcontentlength").await,
            GetContentType => atom("getcontenttype").await,
            GetEtag => atom("getetag").await,
            GetLastModified => atom("getlastmodified").await,
            LockDiscovery => atom("lockdiscovery").await,
            ResourceType => atom("resourcetype").await,
            SupportedLock => atom("supportedlock").await,
            Extension(inner) => ctx.hook_propertyrequest(inner, xml).await,
        }
    }
}

impl<C: Context> QuickWritable<C> for ActiveLock {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        // <D:activelock>
        //   <D:locktype><D:write/></D:locktype>
        //   <D:lockscope><D:exclusive/></D:lockscope>
        //   <D:depth>infinity</D:depth>
        //   <D:owner>
        //     <D:href>http://example.org/~ejw/contact.html</D:href>
        //   </D:owner>
        //   <D:timeout>Second-604800</D:timeout>
        //   <D:locktoken>
        //     <D:href>urn:uuid:e71d4fae-5dec-22d6-fea5-00a0c91e6be4</D:href>
        //   </D:locktoken>
        //   <D:lockroot>
        //     <D:href>http://example.com/workspace/webdav/proposal.doc</D:href>
        //   </D:lockroot>
        // </D:activelock>
        let start = ctx.create_dav_element("activelock");
        let end = start.to_end();

        xml.write_event_async(Event::Start(start.clone())).await?;
        self.locktype.write(xml, ctx.child()).await?;
        self.lockscope.write(xml, ctx.child()).await?;
        self.depth.write(xml, ctx.child()).await?;
        if let Some(owner) = &self.owner {
            owner.write(xml, ctx.child()).await?;
        }
        if let Some(timeout) = &self.timeout {
            timeout.write(xml, ctx.child()).await?;
        }
        if let Some(locktoken) = &self.locktoken {
            locktoken.write(xml, ctx.child()).await?;
        }
        self.lockroot.write(xml, ctx.child()).await?;
        xml.write_event_async(Event::End(end)).await?;

        Ok(())
    }
}

impl<C: Context> QuickWritable<C> for LockType {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        let start = ctx.create_dav_element("locktype");
        let end = start.to_end();
        let ctx = ctx.child();

        xml.write_event_async(Event::Start(start.clone())).await?;
        match self {
            Self::Write => xml.write_event_async(Event::Empty(ctx.create_dav_element("write"))).await?,
        }; 
        xml.write_event_async(Event::End(end)).await
    }
}

impl<C: Context> QuickWritable<C> for LockScope {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        let start = ctx.create_dav_element("lockscope");
        let end = start.to_end();
        let ctx = ctx.child();

        xml.write_event_async(Event::Start(start.clone())).await?;
        match self {
            Self::Exclusive => xml.write_event_async(Event::Empty(ctx.create_dav_element("exclusive"))).await?,
            Self::Shared => xml.write_event_async(Event::Empty(ctx.create_dav_element("shared"))).await?,
        }; 
        xml.write_event_async(Event::End(end)).await
    }
}

impl<C: Context> QuickWritable<C> for Owner {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        let start = ctx.create_dav_element("owner");
        let end = start.to_end();

        xml.write_event_async(Event::Start(start.clone())).await?;
        match self {
            Self::Txt(txt) => xml.write_event_async(Event::Text(BytesText::new(&txt))).await?,
            Self::Href(href) => href.write(xml, ctx.child()).await?,
        }
        xml.write_event_async(Event::End(end)).await
    }
}

impl<C: Context> QuickWritable<C> for Depth {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        let start = ctx.create_dav_element("depth");
        let end = start.to_end();

        xml.write_event_async(Event::Start(start.clone())).await?;
        match self {
            Self::Zero => xml.write_event_async(Event::Text(BytesText::new("0"))).await?,
            Self::One => xml.write_event_async(Event::Text(BytesText::new("1"))).await?,
            Self::Infinity => xml.write_event_async(Event::Text(BytesText::new("infinity"))).await?,
        };
        xml.write_event_async(Event::End(end)).await
    }
}

impl<C: Context> QuickWritable<C> for Timeout {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        let start = ctx.create_dav_element("timeout");
        let end = start.to_end();

        xml.write_event_async(Event::Start(start.clone())).await?;
        match self {
            Self::Seconds(count) => {
                let txt = format!("Second-{}", count);
                xml.write_event_async(Event::Text(BytesText::new(&txt))).await?
            },
            Self::Infinite => xml.write_event_async(Event::Text(BytesText::new("Infinite"))).await?
        };
        xml.write_event_async(Event::End(end)).await
    }
}

impl<C: Context> QuickWritable<C> for LockToken {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        let start = ctx.create_dav_element("locktoken");
        let end = start.to_end();

        xml.write_event_async(Event::Start(start.clone())).await?;
        self.0.write(xml, ctx.child()).await?;
        xml.write_event_async(Event::End(end)).await
    }
}

impl<C: Context> QuickWritable<C> for LockRoot {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        let start = ctx.create_dav_element("lockroot");
        let end = start.to_end();

        xml.write_event_async(Event::Start(start.clone())).await?;
        self.0.write(xml, ctx.child()).await?;
        xml.write_event_async(Event::End(end)).await
    }
}

impl<C: Context> QuickWritable<C> for LockEntry {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        let start = ctx.create_dav_element("lockentry");
        let end = start.to_end();

        xml.write_event_async(Event::Start(start.clone())).await?;
        self.lockscope.write(xml, ctx.child()).await?;
        self.locktype.write(xml, ctx.child()).await?;
        xml.write_event_async(Event::End(end)).await
    }
}

impl<C: Context> QuickWritable<C> for Error<C> {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        let start = ctx.create_dav_element("error");
        let end = start.to_end();

        xml.write_event_async(Event::Start(start.clone())).await?;
        for violation in &self.0 {
            violation.write(xml, ctx.child()).await?;
        }
        xml.write_event_async(Event::End(end)).await?;

        Ok(())
    }
}

impl<C: Context> QuickWritable<C> for Violation<C> {
    async fn write(&self, xml: &mut Writer<impl AsyncWrite+Unpin>, ctx: C) -> Result<(), QError> {
        match self {
            Violation::LockTokenMatchesRequestUri => xml.write_event_async(Event::Empty(ctx.create_dav_element("lock-token-matches-request-uri"))).await?, 
            Violation::LockTokenSubmitted(hrefs) if hrefs.is_empty() => {
                xml.write_event_async(Event::Empty(ctx.create_dav_element("lock-token-submitted"))).await?
            },
            Violation::LockTokenSubmitted(hrefs) => {
                let start = ctx.create_dav_element("lock-token-submitted");
                let end = start.to_end();

                xml.write_event_async(Event::Start(start.clone())).await?;
                for href in hrefs {
                    href.write(xml, ctx.child()).await?;
                }
                xml.write_event_async(Event::End(end)).await?;
            },
            Violation::NoConflictingLock(hrefs) if hrefs.is_empty() => {
                xml.write_event_async(Event::Empty(ctx.create_dav_element("no-conflicting-lock"))).await?
            },
            Violation::NoConflictingLock(hrefs) => {
                let start = ctx.create_dav_element("no-conflicting-lock");
                let end = start.to_end();

                xml.write_event_async(Event::Start(start.clone())).await?;
                for href in hrefs {
                    href.write(xml, ctx.child()).await?;
                }
                xml.write_event_async(Event::End(end)).await?;
            },
            Violation::NoExternalEntities => xml.write_event_async(Event::Empty(ctx.create_dav_element("no-external-entities"))).await?,
            Violation::PreservedLiveProperties => xml.write_event_async(Event::Empty(ctx.create_dav_element("preserved-live-properties"))).await?,
            Violation::PropfindFiniteDepth => xml.write_event_async(Event::Empty(ctx.create_dav_element("propfind-finite-depth"))).await?,
            Violation::CannotModifyProtectedProperty => xml.write_event_async(Event::Empty(ctx.create_dav_element("cannot-modify-protected-property"))).await?,
            Violation::Extension(inner) => {
                ctx.hook_error(inner, xml).await?;
            },
        };
        Ok(())
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use tokio::io::AsyncWriteExt;

    /// To run only the unit tests and avoid the behavior ones:
    /// cargo test --bin aerogramme
    
    async fn serialize<C: Context, Q: QuickWritable<C>>(ctx: C, elem: &Q) -> String {
        let mut buffer = Vec::new();
        let mut tokio_buffer = tokio::io::BufWriter::new(&mut buffer);
        let mut writer = Writer::new_with_indent(&mut tokio_buffer, b' ', 4);
        elem.write(&mut writer, ctx).await.expect("xml serialization");
        tokio_buffer.flush().await.expect("tokio buffer flush");
        let got = std::str::from_utf8(buffer.as_slice()).unwrap();

        return got.into()
    }

    #[tokio::test]
    async fn basic_href() {

        let got = serialize(
            NoExtension { root: false },
            &Href("/SOGo/dav/so/".into())
        ).await;
        let expected = "<D:href>/SOGo/dav/so/</D:href>";

        assert_eq!(&got, expected);
    }


    #[tokio::test]
    async fn basic_multistatus() {
        let got = serialize(
            NoExtension { root: true },
            &Multistatus { 
                responses: vec![], 
                responsedescription: Some(ResponseDescription("Hello world".into())) 
            },
        ).await;

        let expected = r#"<D:multistatus xmlns:D="DAV:">
    <D:responsedescription>Hello world</D:responsedescription>
</D:multistatus>"#;

        assert_eq!(&got, expected);
    }


    #[tokio::test]
    async fn rfc_error_delete_locked() {
        let got = serialize(
            NoExtension { root: true },
            &Error(vec![
                Violation::LockTokenSubmitted(vec![
                    Href("/locked/".into())
                ])
            ]),
        ).await;

        let expected = r#"<D:error xmlns:D="DAV:">
    <D:lock-token-submitted>
        <D:href>/locked/</D:href>
    </D:lock-token-submitted>
</D:error>"#;

        assert_eq!(&got, expected);
    }

    #[tokio::test]
    async fn rfc_propname_req() {
        let got = serialize(
            NoExtension { root: true },
            &PropFind::PropName,
        ).await;

        let expected = r#"<D:propfind xmlns:D="DAV:">
    <D:propname/>
</D:propfind>"#;

        assert_eq!(&got, expected);
    }

    #[tokio::test]
    async fn rfc_propname_res() {
        let got = serialize(
            NoExtension { root: true },
            &Multistatus {
                responses: vec![
                    Response {
                        href: Href("http://www.example.com/container/".into()),
                        status_or_propstat: StatusOrPropstat::PropStat(vec![PropStat {
                            prop: AnyProp::Name(PropName(vec![
                                PropertyRequest::CreationDate,
                                PropertyRequest::DisplayName,
                                PropertyRequest::ResourceType,
                                PropertyRequest::SupportedLock,
                            ])),
                            status: Status(http::status::StatusCode::OK),
                            error: None,
                            responsedescription: None,
                        }]),
                        error: None,
                        responsedescription: None,
                        location: None,
                    },
                    Response {
                        href: Href("http://www.example.com/container/front.html".into()),
                        status_or_propstat: StatusOrPropstat::PropStat(vec![PropStat {
                            prop: AnyProp::Name(PropName(vec![
                                PropertyRequest::CreationDate,
                                PropertyRequest::DisplayName,
                                PropertyRequest::GetContentLength,
                                PropertyRequest::GetContentType,
                                PropertyRequest::GetEtag,
                                PropertyRequest::GetLastModified,
                                PropertyRequest::ResourceType,
                                PropertyRequest::SupportedLock,
                            ])),
                            status: Status(http::status::StatusCode::OK),
                            error: None,
                            responsedescription: None,
                        }]),
                        error: None,
                        responsedescription: None,
                        location: None,
                    },
                ],
                responsedescription: None,
            },
        ).await;

        let expected = r#"<D:multistatus xmlns:D="DAV:">
    <D:response>
        <D:href>http://www.example.com/container/</D:href>
        <D:propstat>
            <D:prop>
                <D:creationdate/>
                <D:displayname/>
                <D:resourcetype/>
                <D:supportedlock/>
            </D:prop>
            <D:status>HTTP/1.1 200 OK</D:status>
        </D:propstat>
    </D:response>
    <D:response>
        <D:href>http://www.example.com/container/front.html</D:href>
        <D:propstat>
            <D:prop>
                <D:creationdate/>
                <D:displayname/>
                <D:getcontentlength/>
                <D:getcontenttype/>
                <D:getetag/>
                <D:getlastmodified/>
                <D:resourcetype/>
                <D:supportedlock/>
            </D:prop>
            <D:status>HTTP/1.1 200 OK</D:status>
        </D:propstat>
    </D:response>
</D:multistatus>"#;


        assert_eq!(&got, expected, "\n---GOT---\n{got}\n---EXP---\n{expected}\n");
    }

    #[tokio::test]
    async fn rfc_allprop_req() {
        let got = serialize(
            NoExtension { root: true },
            &PropFind::AllProp(None),
        ).await;

    let expected = r#"<D:propfind xmlns:D="DAV:">
    <D:allprop/>
</D:propfind>"#;

        assert_eq!(&got, expected, "\n---GOT---\n{got}\n---EXP---\n{expected}\n");
    }

    #[tokio::test]
    async fn rfc_allprop_res() {
        use chrono::{DateTime,FixedOffset,TimeZone};
        let got = serialize(
            NoExtension { root: true },
            &Multistatus {
                responses: vec![
                    Response {
                        href: Href("/container/".into()),
                        status_or_propstat: StatusOrPropstat::PropStat(vec![PropStat {
                            prop: AnyProp::Value(PropValue(vec![
                                Property::CreationDate(FixedOffset::west_opt(8 * 3600)
                                                       .unwrap()
                                                       .with_ymd_and_hms(1997, 12, 1, 17, 42, 21)
                                                       .unwrap()),
                                Property::DisplayName("Example collection".into()),
                                Property::ResourceType(vec![ResourceType::Collection]),
                                Property::SupportedLock(vec![
                                    LockEntry {
                                        lockscope: LockScope::Exclusive,
                                        locktype: LockType::Write,
                                    },
                                    LockEntry {
                                        lockscope: LockScope::Shared,
                                        locktype: LockType::Write,
                                    },
                                ]),
                            ])),
                            status: Status(http::status::StatusCode::OK),
                            error: None,
                            responsedescription: None,
                        }]),
                        error: None,
                        responsedescription: None,
                        location: None,
                    },
                    Response {
                        href: Href("/container/front.html".into()),
                        status_or_propstat: StatusOrPropstat::PropStat(vec![PropStat {
                            prop: AnyProp::Value(PropValue(vec![
                                Property::CreationDate(FixedOffset::west_opt(8 * 3600)
                                    .unwrap()
                                    .with_ymd_and_hms(1997, 12, 1, 18, 27, 21)
                                    .unwrap()),
                                Property::DisplayName("Example HTML resource".into()),
                                Property::GetContentLength(4525),
                                Property::GetContentType("text/html".into()),
                                Property::GetEtag(r#""zzyzx""#.into()),
                                Property::GetLastModified(FixedOffset::east_opt(0)
                                    .unwrap()
                                    .with_ymd_and_hms(1998, 1, 12, 9, 25, 56)
                                    .unwrap()),
                                Property::ResourceType(vec![]),
                                Property::SupportedLock(vec![
                                    LockEntry {
                                        lockscope: LockScope::Exclusive,
                                        locktype: LockType::Write,
                                    },
                                    LockEntry {
                                        lockscope: LockScope::Shared,
                                        locktype: LockType::Write,
                                    },
                                ]),
                            ])),
                            status: Status(http::status::StatusCode::OK),
                            error: None,
                            responsedescription: None,
                        }]),
                        error: None,
                        responsedescription: None,
                        location: None,
                    },
                ],
                responsedescription: None,
            }
        ).await;

        let expected = r#"<D:multistatus xmlns:D="DAV:">
    <D:response>
        <D:href>/container/</D:href>
        <D:propstat>
            <D:prop>
                <D:creationdate>1997-12-01T17:42:21-08:00</D:creationdate>
                <D:displayname>Example collection</D:displayname>
                <D:resourcetype>
                    <D:collection/>
                </D:resourcetype>
                <D:supportedlock>
                    <D:lockentry>
                        <D:lockscope>
                            <D:exclusive/>
                        </D:lockscope>
                        <D:locktype>
                            <D:write/>
                        </D:locktype>
                    </D:lockentry>
                    <D:lockentry>
                        <D:lockscope>
                            <D:shared/>
                        </D:lockscope>
                        <D:locktype>
                            <D:write/>
                        </D:locktype>
                    </D:lockentry>
                </D:supportedlock>
            </D:prop>
            <D:status>HTTP/1.1 200 OK</D:status>
        </D:propstat>
    </D:response>
    <D:response>
        <D:href>/container/front.html</D:href>
        <D:propstat>
            <D:prop>
                <D:creationdate>1997-12-01T18:27:21-08:00</D:creationdate>
                <D:displayname>Example HTML resource</D:displayname>
                <D:getcontentlength>4525</D:getcontentlength>
                <D:getcontenttype>text/html</D:getcontenttype>
                <D:getetag>&quot;zzyzx&quot;</D:getetag>
                <D:getlastmodified>Mon, 12 Jan 1998 09:25:56 +0000</D:getlastmodified>
                <D:resourcetype/>
                <D:supportedlock>
                    <D:lockentry>
                        <D:lockscope>
                            <D:exclusive/>
                        </D:lockscope>
                        <D:locktype>
                            <D:write/>
                        </D:locktype>
                    </D:lockentry>
                    <D:lockentry>
                        <D:lockscope>
                            <D:shared/>
                        </D:lockscope>
                        <D:locktype>
                            <D:write/>
                        </D:locktype>
                    </D:lockentry>
                </D:supportedlock>
            </D:prop>
            <D:status>HTTP/1.1 200 OK</D:status>
        </D:propstat>
    </D:response>
</D:multistatus>"#;

        assert_eq!(&got, expected, "\n---GOT---\n{got}\n---EXP---\n{expected}\n");
    }


    #[tokio::test]
    async fn rfc_allprop_include() {
        let got = serialize(
            NoExtension { root: true },
            &PropFind::AllProp(Some(Include(vec![
               PropertyRequest::DisplayName,
               PropertyRequest::ResourceType,
            ]))),
        ).await;

        let expected = r#"<D:propfind xmlns:D="DAV:">
    <D:allprop/>
    <D:include>
        <D:displayname/>
        <D:resourcetype/>
    </D:include>
</D:propfind>"#;

        assert_eq!(&got, expected, "\n---GOT---\n{got}\n---EXP---\n{expected}\n");
    }

    #[tokio::test]
    async fn rfc_propertyupdate() {
        let got = serialize(
            NoExtension { root: true },
            &PropertyUpdate(vec![
                PropertyUpdateItem::Set(Set(PropValue(vec![
                    Property::GetContentLanguage("fr-FR".into()),
                ]))),
                PropertyUpdateItem::Remove(Remove(PropName(vec![
                    PropertyRequest::DisplayName,
                ]))),
            ]),
        ).await;

        let expected = r#"<D:propertyupdate xmlns:D="DAV:">
    <D:set>
        <D:prop>
            <D:getcontentlanguage>fr-FR</D:getcontentlanguage>
        </D:prop>
    </D:set>
    <D:remove>
        <D:prop>
            <D:displayname/>
        </D:prop>
    </D:remove>
</D:propertyupdate>"#;

        assert_eq!(&got, expected, "\n---GOT---\n{got}\n---EXP---\n{expected}\n");
    }

    #[tokio::test]
    async fn rfc_delete_locked2() {
        let got = serialize(
            NoExtension { root: true },
            &Multistatus {
                responses: vec![Response {
                    href: Href("http://www.example.com/container/resource3".into()),
                    status_or_propstat: StatusOrPropstat::Status(Status(http::status::StatusCode::from_u16(423).unwrap())),
                    error: Some(Error(vec![Violation::LockTokenSubmitted(vec![])])),
                    responsedescription: None,
                    location: None,
                }],
                responsedescription: None,
            },
        ).await;

        let expected = r#"<D:multistatus xmlns:D="DAV:">
    <D:response>
        <D:href>http://www.example.com/container/resource3</D:href>
        <D:status>HTTP/1.1 423 Locked</D:status>
        <D:error>
            <D:lock-token-submitted/>
        </D:error>
    </D:response>
</D:multistatus>"#;

        assert_eq!(&got, expected, "\n---GOT---\n{got}\n---EXP---\n{expected}\n");
    }

    #[tokio::test]
    async fn rfc_simple_lock_request() {
        let got = serialize(
            NoExtension { root: true },
            &LockInfo {
                lockscope: LockScope::Exclusive,
                locktype: LockType::Write,
                owner: Some(Owner::Href(Href("http://example.org/~ejw/contact.html".into()))),
            },
        ).await;

        let expected = r#"<D:lockinfo xmlns:D="DAV:">
    <D:lockscope>
        <D:exclusive/>
    </D:lockscope>
    <D:locktype>
        <D:write/>
    </D:locktype>
    <D:owner>
        <D:href>http://example.org/~ejw/contact.html</D:href>
    </D:owner>
</D:lockinfo>"#;

        assert_eq!(&got, expected, "\n---GOT---\n{got}\n---EXP---\n{expected}\n");
    }

    #[tokio::test]
    async fn rfc_simple_lock_response() {
        let got = serialize(
            NoExtension { root: true },
            &PropValue(vec![
                Property::LockDiscovery(vec![ActiveLock {
                    lockscope: LockScope::Exclusive,
                    locktype: LockType::Write,
                    depth: Depth::Infinity,
                    owner: Some(Owner::Href(Href("http://example.org/~ejw/contact.html".into()))),
                    timeout: Some(Timeout::Seconds(604800)),
                    locktoken: Some(LockToken(Href("urn:uuid:e71d4fae-5dec-22d6-fea5-00a0c91e6be4".into()))),
                    lockroot: LockRoot(Href("http://example.com/workspace/webdav/proposal.doc".into())),
                }]),
            ]),
        ).await;

        let expected = r#"<D:prop xmlns:D="DAV:">
    <D:lockdiscovery>
        <D:activelock>
            <D:locktype>
                <D:write/>
            </D:locktype>
            <D:lockscope>
                <D:exclusive/>
            </D:lockscope>
            <D:depth>infinity</D:depth>
            <D:owner>
                <D:href>http://example.org/~ejw/contact.html</D:href>
            </D:owner>
            <D:timeout>Second-604800</D:timeout>
            <D:locktoken>
                <D:href>urn:uuid:e71d4fae-5dec-22d6-fea5-00a0c91e6be4</D:href>
            </D:locktoken>
            <D:lockroot>
                <D:href>http://example.com/workspace/webdav/proposal.doc</D:href>
            </D:lockroot>
        </D:activelock>
    </D:lockdiscovery>
</D:prop>"#;

        assert_eq!(&got, expected, "\n---GOT---\n{got}\n---EXP---\n{expected}\n");
    }
}