#![allow(clippy::upper_case_acronyms)]

use std::convert::TryFrom;
use std::net::SocketAddr;

use trust_dns_resolver::error::ResolveError;
use trust_dns_resolver::lookup::{SrvLookup, TxtLookup};
use trust_dns_resolver::{IntoName, TokioAsyncResolver};

use anyhow::{bail, Result};
#[cfg(feature = "websocket")]
use tokio_tungstenite::tungstenite::http::Uri;

use crate::*;

lazy_static::lazy_static! {
    static ref RESOLVER: TokioAsyncResolver = make_resolver();
}

fn make_resolver() -> TokioAsyncResolver {
    let (config, mut options) = trust_dns_resolver::system_conf::read_system_conf().unwrap();
    options.ip_strategy = trust_dns_resolver::config::LookupIpStrategy::Ipv4AndIpv6;
    TokioAsyncResolver::tokio(config, options).unwrap()
}

#[derive(Clone, Debug, PartialEq)]
pub enum XmppConnectionType {
    StartTLS,
    DirectTLS,
    #[cfg(feature = "quic")]
    QUIC,
    #[cfg(feature = "websocket")]
    WebSocket(Uri, String, bool),
}

#[derive(Debug)]
pub struct XmppConnection {
    conn_type: XmppConnectionType,
    priority: u16,
    #[allow(dead_code)]
    weight: u16, // todo: use weight
    port: u16,
    target: String,
}

impl XmppConnection {
    pub async fn connect(
        &self,
        domain: &str,
        is_c2s: bool,
        stream_open: &[u8],
        in_filter: &mut crate::StanzaFilter,
        client_addr: &mut Context<'_>,
        config: OutgoingConfig,
    ) -> Result<(StanzaWrite, StanzaRead, SocketAddr, &'static str)> {
        debug!("{} attempting connection to SRV: {:?}", client_addr.log_from(), self);
        // todo: need to set options to Ipv4AndIpv6
        let ips = RESOLVER.lookup_ip(self.target.clone()).await?;
        for ip in ips.iter() {
            let to_addr = SocketAddr::new(ip, self.port);
            debug!("{} trying ip {}", client_addr.log_from(), to_addr);
            // todo: for DNSSEC we need to optionally allow target in addition to domain, but what for SNI
            match self.conn_type {
                XmppConnectionType::StartTLS => match crate::starttls_connect(to_addr, domain, is_c2s, stream_open, in_filter, config.clone()).await {
                    Ok((wr, rd)) => return Ok((wr, rd, to_addr, "starttls-out")),
                    Err(e) => error!("starttls connection failed to IP {} from SRV {}, error: {}", to_addr, self.target, e),
                },
                XmppConnectionType::DirectTLS => match crate::tls_connect(to_addr, domain, is_c2s, config.clone()).await {
                    Ok((wr, rd)) => return Ok((wr, rd, to_addr, "directtls-out")),
                    Err(e) => error!("direct tls connection failed to IP {} from SRV {}, error: {}", to_addr, self.target, e),
                },
                #[cfg(feature = "quic")]
                XmppConnectionType::QUIC => match crate::quic_connect(to_addr, domain, is_c2s, config.clone()).await {
                    Ok((wr, rd)) => return Ok((wr, rd, to_addr, "quic-out")),
                    Err(e) => error!("quic connection failed to IP {} from SRV {}, error: {}", to_addr, self.target, e),
                },
                #[cfg(feature = "websocket")]
                // todo: when websocket is found via DNS, we need to validate cert against domain, *not* target, this is a security problem with XEP-0156, we are doing it the secure but likely unexpected way here for now
                XmppConnectionType::WebSocket(ref url, ref origin, ref secure) => {
                    match crate::websocket_connect(to_addr, if *secure { &self.target } else { domain }, url, origin, is_c2s, config.clone()).await {
                        Ok((wr, rd)) => return Ok((wr, rd, to_addr, "websocket-out")),
                        Err(e) => error!("websocket connection failed to IP {} from TXT {}, error: {}", to_addr, url, e),
                    }
                }
            }
        }
        bail!("cannot connect to any IPs for SRV: {}", self.target)
    }
}

fn collect_srvs(ret: &mut Vec<XmppConnection>, srv_records: std::result::Result<SrvLookup, ResolveError>, conn_type: XmppConnectionType) {
    if let Ok(srv_records) = srv_records {
        for srv in srv_records.iter() {
            if !srv.target().is_root() {
                ret.push(XmppConnection {
                    conn_type: conn_type.clone(),
                    priority: srv.priority(),
                    weight: srv.weight(),
                    port: srv.port(),
                    target: srv.target().to_ascii(),
                });
            }
        }
    }
}

#[cfg(feature = "websocket")]
fn wss_to_srv(url: &str, secure: bool) -> Option<XmppConnection> {
    let url = match Uri::try_from(url) {
        Ok(url) => url,
        Err(e) => {
            debug!("invalid URL record '{}': {}", url, e);
            return None;
        }
    };
    let server_name = match url.host() {
        Some(server_name) => server_name.to_string(),
        None => {
            debug!("invalid URL record '{}'", url);
            return None;
        }
    };
    let target = server_name.to_string();

    let mut origin = "https://".to_string();
    origin.push_str(&server_name);
    let port = if let Some(port) = url.port() {
        origin.push(':');
        origin.push_str(port.as_str());
        port.as_u16()
    } else {
        443
    };
    Some(XmppConnection {
        conn_type: XmppConnectionType::WebSocket(url, origin, secure),
        priority: u16::MAX,
        weight: 0,
        port,
        target,
    })
}

#[cfg(feature = "websocket")]
fn collect_txts(ret: &mut Vec<XmppConnection>, secure_urls: Vec<String>, txt_records: std::result::Result<TxtLookup, ResolveError>, is_c2s: bool) {
    if let Ok(txt_records) = txt_records {
        for txt in txt_records.iter() {
            for txt in txt.iter() {
                // we only support wss and not ws (insecure) on purpose
                if txt.starts_with(if is_c2s { b"_xmpp-client-websocket=wss://" } else { b"_xmpp-server-websocket=wss://" }) {
                    // 23 is the length of "_xmpp-client-websocket=" and "_xmpp-server-websocket="
                    if let Ok(url) = String::from_utf8(txt[23..].to_vec()) {
                        if !secure_urls.contains(&url) {
                            if let Some(srv) = wss_to_srv(&url, false) {
                                ret.push(srv);
                            }
                        }
                    } else {
                        debug!("invalid TXT record '{}'", to_str(txt));
                    }
                }
            }
        }
    }
}

pub async fn get_xmpp_connections(domain: &str, is_c2s: bool) -> Result<Vec<XmppConnection>> {
    let (starttls, direct_tls, quic, websocket_txt, websocket_rel) = if is_c2s {
        ("_xmpp-client._tcp", "_xmpps-client._tcp", "_xmppq-client._udp", "_xmppconnect", "urn:xmpp:alt-connections:websocket")
    } else {
        (
            "_xmpp-server._tcp",
            "_xmpps-server._tcp",
            "_xmppq-server._udp",
            "_xmppconnect-server",
            "urn:xmpp:alt-connections:s2s-websocket",
        )
    };

    let starttls = format!("{}.{}.", starttls, domain).into_name()?;
    let direct_tls = format!("{}.{}.", direct_tls, domain).into_name()?;
    #[cfg(feature = "quic")]
    let quic = format!("{}.{}.", quic, domain).into_name()?;
    #[cfg(feature = "websocket")]
    let websocket_txt = format!("{}.{}.", websocket_txt, domain).into_name()?;

    // this lets them run concurrently but not in parallel, could spawn parallel tasks but... worth it ?
    // todo: don't look up websocket or quic records when they are disabled
    let (
        starttls,
        direct_tls,
        //#[cfg(feature = "quic")]
        quic,
        //#[cfg(feature = "websocket")]
        websocket_txt,
        websocket_host_meta,
        websocket_host_meta_json,
    ) = tokio::join!(
        RESOLVER.srv_lookup(starttls),
        RESOLVER.srv_lookup(direct_tls),
        //#[cfg(feature = "quic")]
        RESOLVER.srv_lookup(quic),
        //#[cfg(feature = "websocket")]
        RESOLVER.txt_lookup(websocket_txt),
        collect_host_meta(domain, websocket_rel),
        collect_host_meta_json(domain, websocket_rel),
    );

    let mut ret = Vec::new();
    collect_srvs(&mut ret, starttls, XmppConnectionType::StartTLS);
    collect_srvs(&mut ret, direct_tls, XmppConnectionType::DirectTLS);
    #[cfg(feature = "quic")]
    collect_srvs(&mut ret, quic, XmppConnectionType::QUIC);
    #[cfg(feature = "websocket")]
    {
        let mut urls = Vec::new();
        match websocket_host_meta {
            Ok(mut u) => urls.append(&mut u),
            Err(e) => debug!("websocket_host_meta error for domain {}: {}", domain, e),
        }
        match websocket_host_meta_json {
            Ok(mut u) => urls.append(&mut u),
            Err(e) => debug!("websocket_host_meta_json error for domain {}: {}", domain, e),
        }
        urls.sort();
        urls.dedup();
        for url in &urls {
            if let Some(url) = wss_to_srv(url, true) {
                ret.push(url);
            }
        }
        collect_txts(&mut ret, urls, websocket_txt, is_c2s);
    }
    ret.sort_by(|a, b| a.priority.cmp(&b.priority));
    // todo: do something with weight

    if ret.is_empty() {
        // default starttls ports
        ret.push(XmppConnection {
            priority: 0,
            weight: 0,
            target: domain.to_string(),
            conn_type: XmppConnectionType::StartTLS,
            port: if is_c2s { 5222 } else { 5269 },
        });
        // by spec there are no default direct/quic ports, but we are going 443
        ret.push(XmppConnection {
            priority: 0,
            weight: 0,
            target: domain.to_string(),
            conn_type: XmppConnectionType::DirectTLS,
            port: 443,
        });
        #[cfg(feature = "quic")]
        ret.push(XmppConnection {
            priority: 0,
            weight: 0,
            target: domain.to_string(),
            conn_type: XmppConnectionType::QUIC,
            port: 443,
        });
    }

    /*
    // manual target for testing
    ret.clear();
    ret.push(XmppConnection {
        priority: 0,
        weight: 0,
        target: "127.0.0.1".to_string(),
        conn_type: XmppConnectionType::QUIC,
        port: 4443,
    });
    */

    debug!("{} records for {}: {:?}", ret.len(), domain, ret);

    Ok(ret)
}

pub async fn srv_connect(
    domain: &str,
    is_c2s: bool,
    stream_open: &[u8],
    in_filter: &mut crate::StanzaFilter,
    client_addr: &mut Context<'_>,
    config: OutgoingConfig,
) -> Result<(StanzaWrite, StanzaRead, Vec<u8>)> {
    for srv in get_xmpp_connections(domain, is_c2s).await? {
        let connect = srv.connect(domain, is_c2s, stream_open, in_filter, client_addr, config.clone()).await;
        if connect.is_err() {
            continue;
        }
        let (mut out_wr, mut out_rd, to_addr, proto) = connect.unwrap();
        // if any of these ? returns early with an Err, these will stay set, I think that's ok though, the connection will be closed
        client_addr.set_proto(proto);
        client_addr.set_to_addr(to_addr);
        debug!("{} connected", client_addr.log_from());

        trace!("{} '{}'", client_addr.log_from(), to_str(stream_open));
        out_wr.write_all(is_c2s, stream_open, stream_open.len(), client_addr.log_from()).await?;
        out_wr.flush().await?;

        match stream_preamble(&mut out_rd, &mut out_wr, client_addr.log_to(), in_filter).await {
            Ok((server_response, _)) => return Ok((out_wr, out_rd, server_response)),
            Err(e) => {
                debug!("{} bad server response, going to next record, error: {}", client_addr.log_to(), e);
                client_addr.set_proto("unk-out");
                continue;
            }
        }
    }
    bail!("all connection attempts failed")
}

#[cfg(not(feature = "websocket"))]
async fn collect_host_meta_json(domain: &str, rel: &str) -> Result<Vec<String>> {
    bail!("websocket disabled")
}

#[cfg(not(feature = "websocket"))]
async fn collect_host_meta(domain: &str, rel: &str) -> Result<Vec<String>> {
    bail!("websocket disabled")
}

#[cfg(feature = "websocket")]
async fn collect_host_meta_json(domain: &str, rel: &str) -> Result<Vec<String>> {
    #[derive(Deserialize)]
    struct HostMeta {
        links: Vec<Link>,
    }
    #[derive(Deserialize)]
    struct Link {
        rel: String,
        href: String,
    }

    let url = format!("https://{}/.well-known/host-meta.json", domain);
    let resp = reqwest::get(&url).await?;
    if resp.status().is_success() {
        let resp = resp.json::<HostMeta>().await?;
        // we will only support wss:// (TLS) not ws:// (plain text)
        Ok(resp.links.iter().filter(|l| l.rel == rel && l.href.starts_with("wss://")).map(|l| l.href.clone()).collect())
    } else {
        bail!("failed with status code {} for url {}", resp.status(), url)
    }
}

#[cfg(feature = "websocket")]
async fn parse_host_meta(rel: &str, bytes: &[u8]) -> Result<Vec<String>> {
    let mut vec = Vec::new();
    let mut stanza_reader = StanzaReader(bytes);
    let mut filter = StanzaFilter::new(8192);
    while let Some((stanza, eoft)) = stanza_reader.next_eoft(&mut filter).await? {
        if stanza.starts_with(b"<XRD") || stanza.starts_with(b"<xrd") {
            // now we are to the Links
            let stanza = &stanza[eoft..];
            let mut stanza_reader = StanzaReader(stanza);
            let mut filter = StanzaFilter::new(4096);
            while let Ok(Some(stanza)) = stanza_reader.next(&mut filter).await {
                if stanza.contains_seq(rel.as_bytes()) {
                    for needle in [b"='wss://", b"=\"wss://"] {
                        if let Ok(idx) = stanza.first_index_of(needle) {
                            let stanza = &stanza[idx + 2..];
                            if let Ok(idx) = stanza.first_index_of(&needle[1..2]) {
                                vec.push(String::from_utf8(stanza[..idx].to_vec())?);
                            }
                        }
                    }
                }
            }
        }
    }
    Ok(vec)
}

#[cfg(feature = "websocket")]
async fn collect_host_meta(domain: &str, rel: &str) -> Result<Vec<String>> {
    let url = format!("https://{}/.well-known/host-meta", domain);
    let resp = reqwest::get(&url).await?;
    if resp.status().is_success() {
        parse_host_meta(rel, resp.bytes().await?.as_ref()).await
    } else {
        bail!("failed with status code {} for url {}", resp.status(), url)
    }
}

#[cfg(test)]
mod tests {
    use crate::srv::*;

    //#[tokio::test]
    async fn srv() -> Result<()> {
        let domain = "burtrum.org";
        let is_c2s = true;
        for srv in get_xmpp_connections(domain, is_c2s).await? {
            println!("trying 1 domain {}, SRV: {:?}", domain, srv);
            let ips = RESOLVER.lookup_ip(srv.target.clone()).await?;
            for ip in ips.iter() {
                println!("trying domain {}, ip {}, is_c2s: {}, SRV: {:?}", domain, ip, is_c2s, srv);
            }
        }
        Ok(())
    }

    #[cfg(feature = "websocket")]
    //#[tokio::test]
    async fn http() -> Result<()> {
        let hosts = collect_host_meta_json("burtrum.org", "urn:xmpp:alt-connections:websocket").await?;
        println!("{:?}", hosts);
        let hosts = collect_host_meta("burtrum.org", "urn:xmpp:alt-connections:websocket").await?;
        println!("{:?}", hosts);
        Ok(())
    }

    #[cfg(feature = "websocket")]
    #[tokio::test]
    async fn test_parse_host_meta() -> Result<()> {
        let xrd = br#"<XRD xmlns='http://docs.oasis-open.org/ns/xri/xrd-1.0'><Link rel='urn:xmpp:alt-connections:xbosh' href='https://burtrum.org/http-bind'/><Link rel='urn:xmpp:alt-connections:websocket' href='wss://burtrum.org/xmpp-websocket'/></XRD>"#;
        assert_eq!(parse_host_meta("urn:xmpp:alt-connections:websocket", xrd).await?, vec!["wss://burtrum.org/xmpp-websocket"]);

        let xrd = br#"<XRD xmlns="http://docs.oasis-open.org/ns/xri/xrd-1.0"><Link rel="urn:xmpp:alt-connections:xbosh" href="https://burtrum.org/http-bind"/><Link rel="urn:xmpp:alt-connections:websocket" href="wss://burtrum.org/xmpp-websocket"/></XRD>"#;
        assert_eq!(parse_host_meta("urn:xmpp:alt-connections:websocket", xrd).await?, vec!["wss://burtrum.org/xmpp-websocket"]);

        let xrd = br#"<xrd xmlns='http://docs.oasis-open.org/ns/xri/xrd-1.0'><link rel='urn:xmpp:alt-connections:xbosh' href='https://burtrum.org/http-bind'/><link rel='urn:xmpp:alt-connections:websocket' href='wss://burtrum.org/xmpp-websocket'/></xrd>"#;
        assert_eq!(parse_host_meta("urn:xmpp:alt-connections:websocket", xrd).await?, vec!["wss://burtrum.org/xmpp-websocket"]);

        let xrd = br#"<xrd xmlns="http://docs.oasis-open.org/ns/xri/xrd-1.0"><link rel="urn:xmpp:alt-connections:xbosh" href="https://burtrum.org/http-bind"/><link rel="urn:xmpp:alt-connections:websocket" href="wss://burtrum.org/xmpp-websocket"/></xrd>"#;
        assert_eq!(parse_host_meta("urn:xmpp:alt-connections:websocket", xrd).await?, vec!["wss://burtrum.org/xmpp-websocket"]);

        let xrd = br#"<xrd xmlns="http://docs.oasis-open.org/ns/xri/xrd-1.0"><link rel="urn:xmpp:alt-connections:xbosh" href="https://burtrum.org/http-bind"/><link rel="urn:xmpp:alt-connections:websocket" href="wss://burtrum.org/xmpp-websocket"/><link rel="urn:xmpp:alt-connections:s2s-websocket" href="wss://burtrum.org/xmpp-websocket-s2s"/></xrd>"#;
        assert_eq!(parse_host_meta("urn:xmpp:alt-connections:s2s-websocket", xrd).await?, vec!["wss://burtrum.org/xmpp-websocket-s2s"]);

        let xrd = br#"<xrd xmlns="http://docs.oasis-open.org/ns/xri/xrd-1.0"><link rel="urn:xmpp:alt-connections:xbosh" href="https://burtrum.org/http-bind"/><link rel="urn:xmpp:alt-connections:websocket" href="wss://burtrum.org/xmpp-websocket"/><link rel="urn:xmpp:alt-connections:s2s-websocket" href="wss://burtrum.org/xmpp-websocket-s2s"/></xrd>"#;
        assert_eq!(parse_host_meta("urn:xmpp:alt-connections:websocket", xrd).await?, vec!["wss://burtrum.org/xmpp-websocket"]);

        Ok(())
    }
}