use std::io::Write;

use quick_xml::events::attributes::Attribute;
use quick_xml::events::{BytesStart, Event};
use quick_xml::name::{Namespace, QName, ResolveResult};
use quick_xml::writer::Writer;
use quick_xml::{NsReader, Result};
use tokio::io::AsyncBufRead;

pub static XMLNS: &'static str = "http://etherx.jabber.org/streams";
pub static PREFIX: &'static str = "stream";
pub static XMLNS_XML: &'static str = "http://www.w3.org/XML/1998/namespace";

#[derive(Debug, PartialEq, Eq)]
pub struct ClientStreamStart {
    pub to: String,
    pub lang: String,
    pub version: String,
}
impl ClientStreamStart {
    pub async fn parse(
        reader: &mut NsReader<impl AsyncBufRead + Unpin>,
        buf: &mut Vec<u8>,
    ) -> Result<ClientStreamStart> {
        if let Event::Start(e) = reader.read_event_into_async(buf).await? {
            let (ns, local) = reader.resolve_element(e.name());
            if ns != ResolveResult::Bound(Namespace(XMLNS.as_bytes())) {
                return Err(panic!());
            }
            if local.into_inner() != b"stream" {
                return Err(panic!());
            }
            let mut to = None;
            let mut lang = None;
            let mut version = None;
            for attr in e.attributes() {
                let attr = attr?;
                let (ns, name) = reader.resolve_attribute(attr.key);
                match (ns, name.into_inner()) {
                    (ResolveResult::Unbound, b"to") => {
                        let value = attr.unescape_value()?;
                        to = Some(value.to_string());
                    }
                    (
                        ResolveResult::Bound(Namespace(b"http://www.w3.org/XML/1998/namespace")),
                        b"lang",
                    ) => {
                        let value = attr.unescape_value()?;
                        lang = Some(value.to_string());
                    }
                    (ResolveResult::Unbound, b"version") => {
                        let value = attr.unescape_value()?;
                        version = Some(value.to_string());
                    }
                    _ => {}
                }
            }
            Ok(ClientStreamStart {
                to: to.unwrap(),
                lang: lang.unwrap(),
                version: version.unwrap(),
            })
        } else {
            Err(panic!())
        }
    }
}

pub struct ServerStreamStart {
    pub from: String,
    pub lang: String,
    pub version: String,
}
impl ServerStreamStart {
    pub fn write(&self, writer: &mut Writer<impl Write>) -> Result<()> {
        let mut event = BytesStart::new("stream:stream");
        let attributes = [
            Attribute {
                key: QName(b"from"),
                value: self.from.as_bytes().into(),
            },
            Attribute {
                key: QName(b"version"),
                value: self.version.as_bytes().into(),
            },
            Attribute {
                key: QName(b"xmlns"),
                value: super::client::XMLNS.as_bytes().into(),
            },
            Attribute {
                key: QName(b"xmlns:stream"),
                value: XMLNS.as_bytes().into(),
            },
            Attribute {
                key: QName(b"xml:lang"),
                value: self.lang.as_bytes().into(),
            },
        ];
        event.extend_attributes(attributes.into_iter());
        writer.write_event(Event::Start(event))?;
        Ok(())
    }
}

#[cfg(test)]
mod test {
    use super::*;

    #[tokio::test]
    async fn client_stream_start_correct_parse() {
        let input = r###"<stream:stream xmlns:stream="http://etherx.jabber.org/streams" to="vlnv.dev" version="1.0" xmlns="jabber:client" xml:lang="en" xmlns:xml="http://www.w3.org/XML/1998/namespace">"###;
        let mut reader = NsReader::from_reader(input.as_bytes());
        let mut buf = vec![];
        let res = ClientStreamStart::parse(&mut reader, &mut buf)
            .await
            .unwrap();
        assert_eq!(
            res,
            ClientStreamStart {
                to: "vlnv.dev".to_owned(),
                lang: "en".to_owned(),
                version: "1.0".to_owned()
            }
        )
    }

    #[test]
    fn server_stream_start_write() {
        let input = ServerStreamStart {
            from: "vlnv.dev".to_owned(),
            lang: "en".to_owned(),
            version: "1.0".to_owned(),
        };
        let expected = r###"<stream:stream from="vlnv.dev" version="1.0" xmlns="jabber:client" xmlns:stream="http://etherx.jabber.org/streams" xml:lang="en">"###;
        let mut output: Vec<u8> = vec![];
        let mut writer = Writer::new(&mut output);
        input.write(&mut writer).unwrap();
        assert_eq!(std::str::from_utf8(&output).unwrap(), expected);
    }
}