rsiprtp 0.4.1

//! DNS resolver for SIP URI resolution per RFC 3263.
//!
//! Implements the SIP URI resolution procedures using:
//! - NAPTR records to discover transport protocols
//! - SRV records to discover servers
//! - A/AAAA records as fallback
//!
//! # Example
//!
//! ```rust,ignore
//! use rsiprtp::transport::{SipResolver, ResolvedTarget};
//!
//! #[tokio::main]
//! async fn main() -> Result<(), Box<dyn std::error::Error>> {
//!     let resolver = SipResolver::new().await?;
//!
//!     // Resolve a SIP URI
//!     let targets = resolver.resolve("example.com", None).await?;
//!
//!     for target in targets {
//!         println!("{}:{} via {:?}", target.host, target.port, target.transport);
//!     }
//!
//!     Ok(())
//! }
//! ```

use hickory_resolver::config::{ResolverConfig, ResolverOpts};
use hickory_resolver::proto::rr::RecordType;
use hickory_resolver::TokioAsyncResolver;
use std::future::Future;
use std::net::{IpAddr, SocketAddr};
use std::pin::Pin;
use thiserror::Error;
use tracing::{debug, trace};

use crate::transport::TransportProtocol;

type BoxFuture<'a, T> = Pin<Box<dyn Future<Output = T> + 'a>>;
type LookupNaptrFn<'a> =
    dyn FnMut(String) -> BoxFuture<'a, Result<Vec<(String, TransportProtocol)>>> + 'a;
type LookupTargetsFn<'a> =
    dyn FnMut(String, TransportProtocol) -> BoxFuture<'a, Result<Vec<ResolvedTarget>>> + 'a;

fn boxed<'a, T>(fut: impl Future<Output = T> + 'a) -> BoxFuture<'a, T> {
    Box::pin(fut)
}

/// DNS resolution errors.
#[derive(Debug, Error)]
pub enum ResolverError {
    /// DNS lookup failed.
    #[error("DNS lookup failed: {0}")]
    LookupFailed(#[from] hickory_resolver::error::ResolveError),

    /// No records found.
    #[error("no DNS records found for {0}")]
    NoRecords(String),

    /// Invalid domain name.
    #[error("invalid domain: {0}")]
    InvalidDomain(String),
}

/// Result type for resolver operations.
pub type Result<T> = std::result::Result<T, ResolverError>;

/// A resolved SIP target (server + port + transport).
#[derive(Debug, Clone)]
pub struct ResolvedTarget {
    /// Server hostname or IP address.
    pub host: String,
    /// Server port.
    pub port: u16,
    /// Transport protocol.
    pub transport: TransportProtocol,
    /// Priority (lower is better).
    pub priority: u16,
    /// Weight for load balancing.
    pub weight: u16,
    /// Resolved IP addresses (if available).
    pub addresses: Vec<IpAddr>,
}

impl ResolvedTarget {
    /// Get socket addresses for this target.
    pub fn socket_addrs(&self) -> Vec<SocketAddr> {
        self.addresses
            .iter()
            .map(|ip| SocketAddr::new(*ip, self.port))
            .collect()
    }
}

/// SIP DNS resolver per RFC 3263.
pub struct SipResolver {
    resolver: TokioAsyncResolver,
}

impl SipResolver {
    /// Create a new resolver with system DNS configuration.
    pub async fn new() -> Result<Self> {
        let resolver =
            TokioAsyncResolver::tokio(ResolverConfig::default(), ResolverOpts::default());

        Ok(Self { resolver })
    }

    /// Create a resolver with custom configuration.
    pub fn with_config(config: ResolverConfig, opts: ResolverOpts) -> Self {
        let resolver = TokioAsyncResolver::tokio(config, opts);
        Self { resolver }
    }

    /// Resolve a SIP domain to target servers.
    ///
    /// # Arguments
    /// * `domain` - Domain to resolve (e.g., "example.com")
    /// * `preferred_transport` - Optional preferred transport protocol
    ///
    /// # Returns
    /// List of resolved targets, sorted by priority and weight.
    pub async fn resolve(
        &self,
        domain: &str,
        preferred_transport: Option<TransportProtocol>,
    ) -> Result<Vec<ResolvedTarget>> {
        let mut lookup_naptr =
            |lookup_domain: String| -> BoxFuture<'_, Result<Vec<(String, TransportProtocol)>>> {
                let resolver = self;
                boxed(async move { resolver.lookup_naptr(&lookup_domain).await })
            };
        let mut lookup_srv = |srv_name: String,

                              transport: TransportProtocol|

         -> BoxFuture<'_, Result<Vec<ResolvedTarget>>> {
            let resolver = self;
            boxed(async move { resolver.lookup_srv(&srv_name, transport).await })
        };
        let mut lookup_address = |addr_domain: String,

                                  transport: TransportProtocol|

         -> BoxFuture<'_, Result<Vec<ResolvedTarget>>> {
            let resolver = self;
            boxed(async move { resolver.lookup_address(&addr_domain, transport).await })
        };

        resolve_with(
            domain,
            preferred_transport,
            &mut lookup_naptr,
            &mut lookup_srv,
            &mut lookup_address,
        )
        .await
    }

    /// Lookup NAPTR records for a domain.
    async fn lookup_naptr(&self, domain: &str) -> Result<Vec<(String, TransportProtocol)>> {
        let lookup = self.resolver.lookup(domain, RecordType::NAPTR).await?;
        Ok(collect_naptr_records(lookup.record_iter()))
    }

    /// Lookup SRV records.
    async fn lookup_srv(
        &self,
        srv_name: &str,
        transport: TransportProtocol,
    ) -> Result<Vec<ResolvedTarget>> {
        let lookup = self.resolver.srv_lookup(srv_name).await?;

        let mut targets: Vec<ResolvedTarget> = Vec::new();

        for record in lookup.iter() {
            let host = record
                .target()
                .to_string()
                .trim_end_matches('.')
                .to_string();
            let port = record.port();
            let priority = record.priority();
            let weight = record.weight();

            trace!(
                "SRV: {} -> {}:{} (pri={}, wt={})",
                srv_name,
                host,
                port,
                priority,
                weight
            );

            // Resolve A/AAAA for the target
            let addresses = self.resolve_addresses(&host).await.unwrap_or_default();

            targets.push(ResolvedTarget {
                host,
                port,
                transport,
                priority,
                weight,
                addresses,
            });
        }

        // Sort by priority (lower first), then by weight (higher first)
        targets.sort_by(|a, b| a.priority.cmp(&b.priority).then(b.weight.cmp(&a.weight)));

        Ok(targets)
    }

    /// Fallback to A/AAAA lookup.
    async fn lookup_address(
        &self,
        domain: &str,
        transport: TransportProtocol,
    ) -> Result<Vec<ResolvedTarget>> {
        let addresses = self.resolve_addresses(domain).await?;
        build_address_targets(domain, transport, addresses)
    }

    /// Resolve A and AAAA records.
    async fn resolve_addresses(&self, host: &str) -> Result<Vec<IpAddr>> {
        // First check if it's already an IP address
        if let Ok(ip) = host.parse::<IpAddr>() {
            return Ok(vec![ip]);
        }

        let lookup = self.resolver.lookup_ip(host).await?;
        Ok(lookup.iter().collect())
    }

    /// Resolve a full SIP URI.
    ///
    /// # Arguments
    /// * `uri` - SIP URI (e.g., "sip:user@example.com:5060;transport=tcp")
    ///
    /// # Returns
    /// Resolved target or error.
    pub async fn resolve_uri(&self, uri: &str) -> Result<Vec<ResolvedTarget>> {
        let (host, port, transport) = parse_sip_uri_internal(uri);

        // If explicit port, skip SRV lookup
        if let Some(port) = port {
            let transport = transport.unwrap_or(TransportProtocol::Udp);
            let lookup_host = host
                .strip_prefix('[')
                .and_then(|value| value.strip_suffix(']'))
                .unwrap_or(host.as_str());
            let addresses = self
                .resolve_addresses(lookup_host)
                .await
                .unwrap_or_default();

            return Ok(vec![ResolvedTarget {
                host: host.to_string(),
                port,
                transport,
                priority: 0,
                weight: 0,
                addresses,
            }]);
        }

        // Use standard resolution
        self.resolve(&host, transport).await
    }
}

/// Parse NAPTR service string.
fn parse_naptr_transport(service: &str) -> Option<TransportProtocol> {
    match service {
        "SIP+D2U" | "sip+d2u" => Some(TransportProtocol::Udp),
        "SIP+D2T" | "sip+d2t" => Some(TransportProtocol::Tcp),
        "SIPS+D2T" | "sips+d2t" => Some(TransportProtocol::Tls),
        _ => None,
    }
}

fn collect_naptr_services(
    entries: Vec<(u16, u16, String, String)>,
) -> Vec<(String, TransportProtocol)> {
    let mut services: Vec<(u16, u16, String, TransportProtocol)> = Vec::new();

    for (order, preference, replacement, service) in entries {
        let transport = parse_naptr_transport(&service);
        if let Some(t) = transport {
            trace!("NAPTR: {} -> {} ({:?})", service, replacement, t);
            services.push((order, preference, replacement, t));
        }
    }

    services.sort_by(|a, b| a.0.cmp(&b.0).then(a.1.cmp(&b.1)));

    services.into_iter().map(|(_, _, r, t)| (r, t)).collect()
}

fn collect_naptr_records<'a, I>(records: I) -> Vec<(String, TransportProtocol)>
where
    I: IntoIterator<Item = &'a hickory_resolver::proto::rr::Record>,
{
    use hickory_resolver::proto::rr::RData;

    let mut entries: Vec<(u16, u16, String, String)> = Vec::new();

    for record in records {
        if let Some(RData::NAPTR(naptr)) = record.data() {
            let service = String::from_utf8_lossy(naptr.services()).to_string();
            let replacement = naptr.replacement().to_string();

            trace!("NAPTR: {} -> {}", service, replacement);
            entries.push((naptr.order(), naptr.preference(), replacement, service));
        }
    }

    collect_naptr_services(entries)
}

fn build_address_targets(
    domain: &str,
    transport: TransportProtocol,
    addresses: Vec<IpAddr>,
) -> Result<Vec<ResolvedTarget>> {
    if addresses.is_empty() {
        return Err(ResolverError::NoRecords(domain.to_string()));
    }

    let port = match transport {
        TransportProtocol::Udp | TransportProtocol::Tcp => 5060,
        TransportProtocol::Tls => 5061,
    };

    Ok(vec![ResolvedTarget {
        host: domain.to_string(),
        port,
        transport,
        priority: 0,
        weight: 0,
        addresses,
    }])
}

async fn resolve_with<'a>(
    domain: &str,
    preferred_transport: Option<TransportProtocol>,
    lookup_naptr: &mut LookupNaptrFn<'a>,
    lookup_srv: &mut LookupTargetsFn<'a>,
    lookup_address: &mut LookupTargetsFn<'a>,
) -> Result<Vec<ResolvedTarget>> {
    debug!("Resolving SIP domain: {}", domain);

    let naptr_results = lookup_naptr(domain.to_string()).await;
    if let Ok(services) = naptr_results {
        if !services.is_empty() {
            debug!("Found {} NAPTR records", services.len());
            return resolve_from_naptr_inner(services, preferred_transport, lookup_srv).await;
        }
    }

    let transports = match preferred_transport {
        Some(t) => vec![t],
        None => vec![
            TransportProtocol::Tls,
            TransportProtocol::Tcp,
            TransportProtocol::Udp,
        ],
    };

    for transport in transports {
        let srv_name = match transport {
            TransportProtocol::Udp => format!("_sip._udp.{}", domain),
            TransportProtocol::Tcp => format!("_sip._tcp.{}", domain),
            TransportProtocol::Tls => format!("_sips._tcp.{}", domain),
        };

        let srv_name_for_log = srv_name.clone();
        if let Ok(targets) = lookup_srv(srv_name, transport).await {
            if !targets.is_empty() {
                debug!(
                    "Found {} SRV records for {}",
                    targets.len(),
                    srv_name_for_log
                );
                return Ok(targets);
            }
        }
    }

    debug!("Falling back to A/AAAA lookup for {}", domain);
    lookup_address(
        domain.to_string(),
        preferred_transport.unwrap_or(TransportProtocol::Udp),
    )
    .await
}

async fn resolve_from_naptr_inner<'a>(
    naptr_results: Vec<(String, TransportProtocol)>,
    preferred_transport: Option<TransportProtocol>,
    lookup_srv: &mut dyn FnMut(
        String,
        TransportProtocol,
    ) -> BoxFuture<'a, Result<Vec<ResolvedTarget>>>,
) -> Result<Vec<ResolvedTarget>> {
    let mut all_targets = Vec::new();

    for (srv_name, transport) in naptr_results {
        if let Some(pref) = preferred_transport {
            if transport != pref {
                continue;
            }
        }

        if let Ok(mut targets) = lookup_srv(srv_name, transport).await {
            all_targets.append(&mut targets);
        }
    }

    if all_targets.is_empty() {
        return Err(ResolverError::NoRecords("NAPTR targets".to_string()));
    }

    Ok(all_targets)
}

/// Internal URI parsing helper.
fn parse_sip_uri_internal(uri: &str) -> (String, Option<u16>, Option<TransportProtocol>) {
    // Lightweight host/port/transport extractor — for full SIP URI
    // parsing use `crate::sip::uri::SipUri`.
    let uri = uri
        .trim_start_matches("sip:")
        .trim_start_matches("sips:")
        .trim_start_matches("SIP:")
        .trim_start_matches("SIPS:");

    // Extract domain (after @ if present)
    let domain_part = uri.split('@').next_back().unwrap_or(uri);

    // Parse host:port and parameters
    let (host_port, params) = domain_part
        .split_once(';')
        .map(|(h, p)| (h, Some(p)))
        .unwrap_or((domain_part, None));

    let (host, explicit_port) = if host_port.starts_with('[') {
        // Try to find closing bracket
        if let Some(end_bracket) = host_port.find(']') {
            if host_port.len() > end_bracket + 1 && host_port.as_bytes()[end_bracket + 1] == b':' {
                // [IPv6]:port
                let h = &host_port[..=end_bracket];
                let p = &host_port[end_bracket + 2..];
                (h, p.parse().ok())
            } else {
                // [IPv6]
                (host_port, None)
            }
        } else {
            // Malformed
            (host_port, None)
        }
    } else {
        host_port
            .split_once(':')
            .map(|(h, p)| (h, p.parse().ok()))
            .unwrap_or((host_port, None))
    };

    // Parse transport parameter
    let transport = params.and_then(|p| {
        p.split(';').find_map(|param| {
            let (k, v) = param.split_once('=')?;
            if k.eq_ignore_ascii_case("transport") {
                match v.to_lowercase().as_str() {
                    "udp" => Some(TransportProtocol::Udp),
                    "tcp" => Some(TransportProtocol::Tcp),
                    "tls" => Some(TransportProtocol::Tls),
                    _ => None,
                }
            } else {
                None
            }
        })
    });

    (host.to_string(), explicit_port, transport)
}

#[cfg(test)]
mod tests {
    use super::*;
    use hickory_resolver::config::{LookupIpStrategy, NameServerConfigGroup};
    use hickory_resolver::proto::op::{Message, MessageType, OpCode, ResponseCode};
    use hickory_resolver::proto::rr::rdata::{A, NAPTR, SRV};
    use hickory_resolver::proto::rr::{Name, RData, Record, RecordType};
    use std::net::Ipv4Addr;
    use std::sync::Once;
    use std::time::Duration;
    use tokio::net::UdpSocket;
    use tokio::sync::oneshot;

    fn init_tracing() {
        static INIT: Once = Once::new();
        INIT.call_once(|| {
            let _ = tracing_subscriber::fmt()
                .with_max_level(tracing::Level::TRACE)
                .with_test_writer()
                .try_init();
        });
    }

    fn build_test_dns_response(request: &Message) -> Message {
        let mut response = Message::new();
        response.set_id(request.id());
        response.set_message_type(MessageType::Response);
        response.set_op_code(OpCode::Query);
        response.set_response_code(ResponseCode::NoError);
        response.set_authoritative(true);
        response.add_queries(request.queries().to_vec());

        for query in request.queries() {
            let name = query.name().to_ascii().to_lowercase();
            match query.query_type() {
                RecordType::NAPTR if name == "example.test." => {
                    let replacement = Name::from_ascii("_sip._udp.example.test.").unwrap();
                    let naptr = NAPTR::new(
                        10,
                        10,
                        b"S".to_vec().into_boxed_slice(),
                        b"SIP+D2U".to_vec().into_boxed_slice(),
                        Vec::<u8>::new().into_boxed_slice(),
                        replacement,
                    );
                    let record = Record::from_rdata(query.name().clone(), 60, RData::NAPTR(naptr));
                    response.add_answer(record);
                }
                RecordType::SRV if name == "_sip._udp.example.test." => {
                    let target = Name::from_ascii("srv.example.test.").unwrap();
                    let srv = SRV::new(10, 5, 5060, target);
                    let record = Record::from_rdata(query.name().clone(), 60, RData::SRV(srv));
                    response.add_answer(record);
                }
                RecordType::SRV if name == "_sip._udp.multi.test." => {
                    let target1 = Name::from_ascii("srv1.multi.test.").unwrap();
                    let target2 = Name::from_ascii("srv2.multi.test.").unwrap();
                    let srv1 = SRV::new(10, 5, 5060, target1);
                    let srv2 = SRV::new(10, 20, 5070, target2);
                    response.add_answer(Record::from_rdata(
                        query.name().clone(),
                        60,
                        RData::SRV(srv1),
                    ));
                    response.add_answer(Record::from_rdata(
                        query.name().clone(),
                        60,
                        RData::SRV(srv2),
                    ));
                }
                RecordType::A if name == "srv.example.test." => {
                    let record = Record::from_rdata(
                        query.name().clone(),
                        60,
                        RData::A(A(Ipv4Addr::new(203, 0, 113, 10))),
                    );
                    response.add_answer(record);
                }
                RecordType::A if name == "srv1.multi.test." => {
                    let record = Record::from_rdata(
                        query.name().clone(),
                        60,
                        RData::A(A(Ipv4Addr::new(203, 0, 113, 11))),
                    );
                    response.add_answer(record);
                }
                RecordType::A if name == "srv2.multi.test." => {
                    let record = Record::from_rdata(
                        query.name().clone(),
                        60,
                        RData::A(A(Ipv4Addr::new(203, 0, 113, 12))),
                    );
                    response.add_answer(record);
                }
                _ => {}
            }
        }

        response
    }

    async fn spawn_test_dns_server(simulate_recv_error: bool) -> (SocketAddr, oneshot::Sender<()>) {
        let socket = UdpSocket::bind("127.0.0.1:0").await.unwrap();
        let addr = socket.local_addr().unwrap();
        let (shutdown_tx, mut shutdown_rx) = oneshot::channel();

        tokio::spawn(async move {
            let mut simulate_recv_error = simulate_recv_error;
            let mut buf = [0u8; 512];
            loop {
                tokio::select! {
                    _ = &mut shutdown_rx => break,
                    result = async {
                        if simulate_recv_error {
                            simulate_recv_error = false;
                            Err(std::io::Error::other("simulated recv error"))
                        } else {
                            socket.recv_from(&mut buf).await
                        }
                    } => {
                        let (len, peer) = match result {
                            Ok(value) => value,
                            Err(_) => break,
                        };
                        let request = match Message::from_vec(&buf[..len]) {
                            Ok(msg) => msg,
                            Err(_) => continue,
                        };
                        let response = build_test_dns_response(&request);
                        let bytes = response.to_vec().unwrap();
                        let _ = socket.send_to(&bytes, peer).await;
                    }
                }
            }
        });

        (addr, shutdown_tx)
    }

    #[test]
    fn test_build_test_dns_response_matching_queries() {
        let mut request = Message::new();
        request.add_query(hickory_resolver::proto::op::Query::query(
            Name::from_ascii("example.test.").unwrap(),
            RecordType::NAPTR,
        ));
        request.add_query(hickory_resolver::proto::op::Query::query(
            Name::from_ascii("_sip._udp.example.test.").unwrap(),
            RecordType::SRV,
        ));
        request.add_query(hickory_resolver::proto::op::Query::query(
            Name::from_ascii("srv.example.test.").unwrap(),
            RecordType::A,
        ));

        let response = build_test_dns_response(&request);
        assert_eq!(response.answers().len(), 3);
    }

    #[test]
    fn test_build_test_dns_response_non_matching_queries() {
        let mut request = Message::new();
        request.add_query(hickory_resolver::proto::op::Query::query(
            Name::from_ascii("other.test.").unwrap(),
            RecordType::NAPTR,
        ));
        request.add_query(hickory_resolver::proto::op::Query::query(
            Name::from_ascii("_sip._tcp.other.test.").unwrap(),
            RecordType::SRV,
        ));
        request.add_query(hickory_resolver::proto::op::Query::query(
            Name::from_ascii("host.other.test.").unwrap(),
            RecordType::A,
        ));
        request.add_query(hickory_resolver::proto::op::Query::query(
            Name::from_ascii("other.test.").unwrap(),
            RecordType::TXT,
        ));

        let response = build_test_dns_response(&request);
        assert!(response.answers().is_empty());
    }

    #[tokio::test]
    async fn test_spawn_test_dns_server_simulated_recv_error() {
        let (_dns_addr, shutdown_tx) = spawn_test_dns_server(true).await;
        tokio::time::sleep(Duration::from_millis(10)).await;
        let _ = shutdown_tx.send(());
    }

    #[tokio::test]
    async fn test_spawn_test_dns_server_ignores_invalid_message() {
        let (dns_addr, shutdown_tx) = spawn_test_dns_server(false).await;
        let socket = UdpSocket::bind("127.0.0.1:0").await.unwrap();
        let _ = socket.send_to(&[0xde, 0xad, 0xbe, 0xef], dns_addr).await;
        tokio::time::sleep(Duration::from_millis(10)).await;
        let _ = shutdown_tx.send(());
    }

    #[tokio::test]
    async fn test_spawn_test_dns_server_shutdown_breaks_loop() {
        let (_dns_addr, shutdown_tx) = spawn_test_dns_server(false).await;
        tokio::time::sleep(Duration::from_millis(10)).await;
        let _ = shutdown_tx.send(());
        tokio::time::sleep(Duration::from_millis(10)).await;
    }

    // ResolvedTarget tests
    #[test]
    fn test_resolved_target_socket_addrs() {
        let target = ResolvedTarget {
            host: "sip.example.com".to_string(),
            port: 5060,
            transport: TransportProtocol::Udp,
            priority: 10,
            weight: 100,
            addresses: vec![
                "192.168.1.1".parse().unwrap(),
                "192.168.1.2".parse().unwrap(),
            ],
        };

        let addrs = target.socket_addrs();
        assert_eq!(addrs.len(), 2);
        assert_eq!(addrs[0], "192.168.1.1:5060".parse().unwrap());
        assert_eq!(addrs[1], "192.168.1.2:5060".parse().unwrap());
    }

    #[test]
    fn test_resolved_target_socket_addrs_ipv6() {
        let target = ResolvedTarget {
            host: "sip.example.com".to_string(),
            port: 5061,
            transport: TransportProtocol::Tls,
            priority: 5,
            weight: 50,
            addresses: vec!["2001:db8::1".parse().unwrap(), "::1".parse().unwrap()],
        };

        let addrs = target.socket_addrs();
        assert_eq!(addrs.len(), 2);
        assert_eq!(addrs[0], "[2001:db8::1]:5061".parse().unwrap());
        assert_eq!(addrs[1], "[::1]:5061".parse().unwrap());
    }

    #[test]
    fn test_resolved_target_socket_addrs_mixed() {
        let target = ResolvedTarget {
            host: "dual.example.com".to_string(),
            port: 5060,
            transport: TransportProtocol::Tcp,
            priority: 0,
            weight: 100,
            addresses: vec![
                "192.168.1.100".parse().unwrap(),
                "2001:db8::100".parse().unwrap(),
            ],
        };

        let addrs = target.socket_addrs();
        assert_eq!(addrs.len(), 2);
        assert!(addrs[0].is_ipv4());
        assert!(addrs[1].is_ipv6());
    }

    #[test]
    fn test_resolved_target_socket_addrs_empty() {
        let target = ResolvedTarget {
            host: "unresolved.example.com".to_string(),
            port: 5060,
            transport: TransportProtocol::Udp,
            priority: 0,
            weight: 0,
            addresses: vec![],
        };

        let addrs = target.socket_addrs();
        assert!(addrs.is_empty());
    }

    #[test]
    fn test_resolved_target_clone() {
        let target = ResolvedTarget {
            host: "sip.example.com".to_string(),
            port: 5060,
            transport: TransportProtocol::Udp,
            priority: 10,
            weight: 100,
            addresses: vec!["192.168.1.1".parse().unwrap()],
        };

        let cloned = target.clone();
        assert_eq!(cloned.host, target.host);
        assert_eq!(cloned.port, target.port);
        assert_eq!(cloned.transport, target.transport);
        assert_eq!(cloned.priority, target.priority);
        assert_eq!(cloned.weight, target.weight);
        assert_eq!(cloned.addresses.len(), target.addresses.len());
    }

    #[test]
    fn test_resolved_target_debug() {
        let target = ResolvedTarget {
            host: "test.com".to_string(),
            port: 5060,
            transport: TransportProtocol::Udp,
            priority: 0,
            weight: 0,
            addresses: vec![],
        };

        let debug = format!("{:?}", target);
        assert!(debug.contains("ResolvedTarget"));
        assert!(debug.contains("test.com"));
    }

    #[test]
    fn test_transport_protocol_priority() {
        // TLS should be preferred over TCP over UDP
        let transports = [
            TransportProtocol::Tls,
            TransportProtocol::Tcp,
            TransportProtocol::Udp,
        ];
        assert_eq!(transports[0], TransportProtocol::Tls);
    }

    // ResolverError tests
    #[test]
    fn test_resolver_error_no_records() {
        let err = ResolverError::NoRecords("example.com".to_string());
        let msg = err.to_string();
        assert!(msg.contains("no DNS records found"));
        assert!(msg.contains("example.com"));
    }

    #[test]
    fn test_resolver_error_invalid_domain() {
        let err = ResolverError::InvalidDomain("bad..domain".to_string());
        let msg = err.to_string();
        assert!(msg.contains("invalid domain"));
        assert!(msg.contains("bad..domain"));
    }

    #[test]
    fn test_resolver_error_debug() {
        let err = ResolverError::NoRecords("test.com".to_string());
        let debug = format!("{:?}", err);
        assert!(debug.contains("NoRecords"));
    }

    // Async tests that use IP addresses (skip DNS)
    #[tokio::test]
    async fn test_resolve_uri_with_ip_address() {
        let resolver = SipResolver::new().await.unwrap();

        // Using an IP address should skip DNS lookup
        let targets = resolver.resolve_uri("sip:user@192.168.1.1:5060").await;
        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets.len(), 1);
        assert_eq!(targets[0].host, "192.168.1.1");
        assert_eq!(targets[0].port, 5060);
        assert_eq!(targets[0].transport, TransportProtocol::Udp);
    }

    #[tokio::test]
    async fn test_resolve_uri_with_explicit_port_and_transport() {
        let resolver = SipResolver::new().await.unwrap();

        let targets = resolver
            .resolve_uri("sip:user@10.0.0.1:5080;transport=tcp")
            .await;
        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets.len(), 1);
        assert_eq!(targets[0].host, "10.0.0.1");
        assert_eq!(targets[0].port, 5080);
        assert_eq!(targets[0].transport, TransportProtocol::Tcp);
    }

    #[tokio::test]
    async fn test_resolve_uri_with_tls_transport() {
        let resolver = SipResolver::new().await.unwrap();

        let targets = resolver
            .resolve_uri("sips:user@172.16.0.1:5061;transport=tls")
            .await;
        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].port, 5061);
        assert_eq!(targets[0].transport, TransportProtocol::Tls);
    }

    #[tokio::test]
    async fn test_resolve_uri_ip_without_port() {
        let resolver = SipResolver::new().await.unwrap();

        // IP address without port - should still work as it skips SRV
        // but goes through resolve() -> lookup_address()
        let targets = resolver.resolve_uri("sip:user@127.0.0.1").await;
        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].host, "127.0.0.1");
        // Default port for UDP
        assert_eq!(targets[0].port, 5060);
    }

    #[tokio::test]
    async fn test_resolve_uri_sips_scheme() {
        let resolver = SipResolver::new().await.unwrap();

        let targets = resolver.resolve_uri("sips:user@10.10.10.10:5061").await;
        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].host, "10.10.10.10");
        assert_eq!(targets[0].port, 5061);
    }

    #[tokio::test]
    async fn test_resolve_uri_no_user_part() {
        let resolver = SipResolver::new().await.unwrap();

        let targets = resolver.resolve_uri("sip:192.168.0.1:5060").await;
        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].host, "192.168.0.1");
    }

    #[tokio::test]
    async fn test_resolver_new() {
        let resolver = SipResolver::new().await;
        assert!(resolver.is_ok());
    }

    #[tokio::test]
    async fn test_resolver_with_config() {
        let config = ResolverConfig::default();
        let opts = ResolverOpts::default();
        let _resolver = SipResolver::with_config(config, opts);
        // Just ensure it doesn't panic
    }

    #[tokio::test]
    async fn test_resolve_addresses_ip_passthrough() {
        let resolver = SipResolver::new().await.unwrap();

        // When given an IP address, it should return it directly
        let addrs = resolver.resolve_addresses("192.168.1.1").await;
        assert!(addrs.is_ok());
        let addrs = addrs.unwrap();
        assert_eq!(addrs.len(), 1);
        assert_eq!(addrs[0], "192.168.1.1".parse::<IpAddr>().unwrap());
    }

    #[tokio::test]
    async fn test_resolve_addresses_ipv6_passthrough() {
        let resolver = SipResolver::new().await.unwrap();

        let addrs = resolver.resolve_addresses("::1").await;
        assert!(addrs.is_ok());
        let addrs = addrs.unwrap();
        assert_eq!(addrs.len(), 1);
        assert_eq!(addrs[0], "::1".parse::<IpAddr>().unwrap());
    }

    #[tokio::test]
    async fn test_lookup_address_default_ports() {
        let resolver = SipResolver::new().await.unwrap();

        // Test UDP default port
        let targets = resolver
            .lookup_address("127.0.0.1", TransportProtocol::Udp)
            .await;
        assert!(targets.is_ok());
        assert_eq!(targets.unwrap()[0].port, 5060);

        // Test TCP default port
        let targets = resolver
            .lookup_address("127.0.0.1", TransportProtocol::Tcp)
            .await;
        assert!(targets.is_ok());
        assert_eq!(targets.unwrap()[0].port, 5060);

        // Test TLS default port
        let targets = resolver
            .lookup_address("127.0.0.1", TransportProtocol::Tls)
            .await;
        assert!(targets.is_ok());
        assert_eq!(targets.unwrap()[0].port, 5061);
    }

    #[tokio::test]
    async fn test_resolve_with_preferred_transport() {
        let resolver = SipResolver::new().await.unwrap();

        // Using IP address skips SRV but still respects transport
        let targets = resolver
            .resolve("127.0.0.1", Some(TransportProtocol::Tcp))
            .await;
        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].transport, TransportProtocol::Tcp);
    }

    #[tokio::test]
    async fn test_resolve_uri_multiple_params() {
        let resolver = SipResolver::new().await.unwrap();

        // URI with multiple parameters
        let targets = resolver
            .resolve_uri("sip:user@10.0.0.1:5070;transport=udp;lr;maddr=10.0.0.2")
            .await;
        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].port, 5070);
        assert_eq!(targets[0].transport, TransportProtocol::Udp);
    }

    #[tokio::test]
    async fn test_resolve_uri_unknown_transport() {
        let resolver = SipResolver::new().await.unwrap();

        // Unknown transport should default to UDP
        let targets = resolver
            .resolve_uri("sip:user@192.168.1.1:5060;transport=sctp")
            .await;
        assert!(targets.is_ok());
        let targets = targets.unwrap();
        // Unknown transport is ignored, defaults to UDP
        assert_eq!(targets[0].transport, TransportProtocol::Udp);
    }

    // Integration-style tests using stubbed lookups.
    #[tokio::test]
    async fn test_resolve_localhost() {
        let mut lookup_naptr =
            |_domain: String| boxed(async { Err(ResolverError::NoRecords("naptr".to_string())) });
        let mut lookup_srv =
            |_srv_name: String, _transport: TransportProtocol| boxed(async { Ok(Vec::new()) });
        let mut lookup_addr = |domain: String, transport: TransportProtocol| {
            boxed(async move {
                Ok(vec![ResolvedTarget {
                    host: domain,
                    port: 5060,
                    transport,
                    priority: 0,
                    weight: 0,
                    addresses: vec!["127.0.0.1".parse().unwrap()],
                }])
            })
        };

        let targets = resolve_with(
            "localhost",
            Some(TransportProtocol::Udp),
            &mut lookup_naptr,
            &mut lookup_srv,
            &mut lookup_addr,
        )
        .await
        .unwrap();

        assert_eq!(targets.len(), 1);
        assert_eq!(targets[0].port, 5060);
    }

    #[tokio::test]
    async fn test_resolve_real_domain() {
        let mut lookup_naptr =
            |_domain: String| boxed(async { Err(ResolverError::NoRecords("naptr".to_string())) });
        let mut lookup_srv = |srv_name: String, transport: TransportProtocol| {
            boxed(async move { Ok(vec![sample_target(&srv_name, transport)]) })
        };
        let mut lookup_addr = |_domain: String, _transport: TransportProtocol| {
            boxed(async { Err(ResolverError::NoRecords("addr".to_string())) })
        };

        let _ = lookup_addr("example.com".to_string(), TransportProtocol::Udp).await;
        let targets = resolve_with(
            "example.com",
            Some(TransportProtocol::Udp),
            &mut lookup_naptr,
            &mut lookup_srv,
            &mut lookup_addr,
        )
        .await
        .unwrap();

        assert_eq!(targets.len(), 1);
        assert_eq!(targets[0].host, "_sip._udp.example.com");
    }

    // ==================================================================================
    // Additional comprehensive tests for improved coverage
    // ==================================================================================

    // SRV sorting tests - test priority and weight sorting logic
    #[test]
    fn test_srv_sorting_by_priority() {
        // Create targets with different priorities
        let mut targets = [
            ResolvedTarget {
                host: "low-priority.example.com".to_string(),
                port: 5060,
                transport: TransportProtocol::Udp,
                priority: 20,
                weight: 100,
                addresses: vec![],
            },
            ResolvedTarget {
                host: "high-priority.example.com".to_string(),
                port: 5060,
                transport: TransportProtocol::Udp,
                priority: 10,
                weight: 100,
                addresses: vec![],
            },
            ResolvedTarget {
                host: "medium-priority.example.com".to_string(),
                port: 5060,
                transport: TransportProtocol::Udp,
                priority: 15,
                weight: 100,
                addresses: vec![],
            },
        ];

        // Apply the same sorting logic as lookup_srv
        targets.sort_by(|a, b| a.priority.cmp(&b.priority).then(b.weight.cmp(&a.weight)));

        // Lower priority should come first
        assert_eq!(targets[0].priority, 10);
        assert_eq!(targets[0].host, "high-priority.example.com");
        assert_eq!(targets[1].priority, 15);
        assert_eq!(targets[2].priority, 20);
    }

    #[test]
    fn test_srv_sorting_by_weight_when_priority_equal() {
        // Create targets with same priority but different weights
        let mut targets = [
            ResolvedTarget {
                host: "low-weight.example.com".to_string(),
                port: 5060,
                transport: TransportProtocol::Udp,
                priority: 10,
                weight: 50,
                addresses: vec![],
            },
            ResolvedTarget {
                host: "high-weight.example.com".to_string(),
                port: 5060,
                transport: TransportProtocol::Udp,
                priority: 10,
                weight: 200,
                addresses: vec![],
            },
            ResolvedTarget {
                host: "medium-weight.example.com".to_string(),
                port: 5060,
                transport: TransportProtocol::Udp,
                priority: 10,
                weight: 100,
                addresses: vec![],
            },
        ];

        // Apply the same sorting logic as lookup_srv
        targets.sort_by(|a, b| a.priority.cmp(&b.priority).then(b.weight.cmp(&a.weight)));

        // Same priority, so higher weight should come first
        assert_eq!(targets[0].weight, 200);
        assert_eq!(targets[0].host, "high-weight.example.com");
        assert_eq!(targets[1].weight, 100);
        assert_eq!(targets[2].weight, 50);
    }

    #[test]
    fn test_srv_sorting_combined_priority_and_weight() {
        let mut targets = [
            ResolvedTarget {
                host: "server1.example.com".to_string(),
                port: 5060,
                transport: TransportProtocol::Udp,
                priority: 10,
                weight: 100,
                addresses: vec![],
            },
            ResolvedTarget {
                host: "server2.example.com".to_string(),
                port: 5060,
                transport: TransportProtocol::Udp,
                priority: 10,
                weight: 200,
                addresses: vec![],
            },
            ResolvedTarget {
                host: "server3.example.com".to_string(),
                port: 5060,
                transport: TransportProtocol::Udp,
                priority: 5,
                weight: 50,
                addresses: vec![],
            },
            ResolvedTarget {
                host: "server4.example.com".to_string(),
                port: 5060,
                transport: TransportProtocol::Udp,
                priority: 5,
                weight: 150,
                addresses: vec![],
            },
        ];

        targets.sort_by(|a, b| a.priority.cmp(&b.priority).then(b.weight.cmp(&a.weight)));

        // Priority 5 comes first
        assert_eq!(targets[0].priority, 5);
        assert_eq!(targets[0].weight, 150); // Higher weight
        assert_eq!(targets[1].priority, 5);
        assert_eq!(targets[1].weight, 50); // Lower weight
                                           // Then priority 10
        assert_eq!(targets[2].priority, 10);
        assert_eq!(targets[2].weight, 200);
        assert_eq!(targets[3].priority, 10);
        assert_eq!(targets[3].weight, 100);
    }

    #[test]
    fn test_srv_sorting_zero_weight() {
        let mut targets = [
            ResolvedTarget {
                host: "zero-weight.example.com".to_string(),
                port: 5060,
                transport: TransportProtocol::Udp,
                priority: 10,
                weight: 0,
                addresses: vec![],
            },
            ResolvedTarget {
                host: "nonzero-weight.example.com".to_string(),
                port: 5060,
                transport: TransportProtocol::Udp,
                priority: 10,
                weight: 100,
                addresses: vec![],
            },
        ];

        targets.sort_by(|a, b| a.priority.cmp(&b.priority).then(b.weight.cmp(&a.weight)));

        // Higher weight comes first
        assert_eq!(targets[0].weight, 100);
        assert_eq!(targets[1].weight, 0);
    }

    #[test]
    fn test_srv_sorting_max_values() {
        let mut targets = [
            ResolvedTarget {
                host: "max-priority.example.com".to_string(),
                port: 5060,
                transport: TransportProtocol::Udp,
                priority: u16::MAX,
                weight: 100,
                addresses: vec![],
            },
            ResolvedTarget {
                host: "min-priority.example.com".to_string(),
                port: 5060,
                transport: TransportProtocol::Udp,
                priority: 0,
                weight: u16::MAX,
                addresses: vec![],
            },
        ];

        targets.sort_by(|a, b| a.priority.cmp(&b.priority).then(b.weight.cmp(&a.weight)));

        assert_eq!(targets[0].priority, 0);
        assert_eq!(targets[1].priority, u16::MAX);
    }

    // NAPTR sorting tests - test order and preference sorting logic
    #[test]
    fn test_naptr_sorting_by_order() {
        let mut services = [
            (
                30u16,
                50u16,
                "srv3.example.com".to_string(),
                TransportProtocol::Tcp,
            ),
            (
                10u16,
                50u16,
                "srv1.example.com".to_string(),
                TransportProtocol::Udp,
            ),
            (
                20u16,
                50u16,
                "srv2.example.com".to_string(),
                TransportProtocol::Tls,
            ),
        ];

        // Apply same sorting as lookup_naptr
        services.sort_by(|a, b| a.0.cmp(&b.0).then(a.1.cmp(&b.1)));

        // Lower order comes first
        assert_eq!(services[0].0, 10);
        assert_eq!(services[0].2, "srv1.example.com");
        assert_eq!(services[1].0, 20);
        assert_eq!(services[2].0, 30);
    }

    #[test]
    fn test_naptr_sorting_by_preference_when_order_equal() {
        let mut services = [
            (
                10u16,
                100u16,
                "srv3.example.com".to_string(),
                TransportProtocol::Tcp,
            ),
            (
                10u16,
                50u16,
                "srv1.example.com".to_string(),
                TransportProtocol::Udp,
            ),
            (
                10u16,
                75u16,
                "srv2.example.com".to_string(),
                TransportProtocol::Tls,
            ),
        ];

        services.sort_by(|a, b| a.0.cmp(&b.0).then(a.1.cmp(&b.1)));

        // Same order, lower preference comes first
        assert_eq!(services[0].1, 50);
        assert_eq!(services[0].2, "srv1.example.com");
        assert_eq!(services[1].1, 75);
        assert_eq!(services[2].1, 100);
    }

    #[test]
    fn test_naptr_sorting_combined_order_and_preference() {
        let mut services = [
            (
                20u16,
                50u16,
                "srv4.example.com".to_string(),
                TransportProtocol::Tcp,
            ),
            (
                10u16,
                100u16,
                "srv2.example.com".to_string(),
                TransportProtocol::Udp,
            ),
            (
                10u16,
                50u16,
                "srv1.example.com".to_string(),
                TransportProtocol::Tls,
            ),
            (
                20u16,
                25u16,
                "srv3.example.com".to_string(),
                TransportProtocol::Tcp,
            ),
        ];

        services.sort_by(|a, b| a.0.cmp(&b.0).then(a.1.cmp(&b.1)));

        // Order 10 first, then by preference
        assert_eq!(services[0].0, 10);
        assert_eq!(services[0].1, 50);
        assert_eq!(services[1].0, 10);
        assert_eq!(services[1].1, 100);
        // Then order 20, by preference
        assert_eq!(services[2].0, 20);
        assert_eq!(services[2].1, 25);
        assert_eq!(services[3].0, 20);
        assert_eq!(services[3].1, 50);
    }

    #[test]
    fn test_collect_naptr_services_filters_and_sorts() {
        let entries = vec![
            (
                20u16,
                10u16,
                "srv2.example.com".to_string(),
                "SIP+D2T".to_string(),
            ),
            (
                10u16,
                20u16,
                "srv1.example.com".to_string(),
                "SIP+D2U".to_string(),
            ),
            (
                10u16,
                5u16,
                "srv0.example.com".to_string(),
                "SIPS+D2T".to_string(),
            ),
            (
                30u16,
                5u16,
                "ignored.example.com".to_string(),
                "SIP+UNKNOWN".to_string(),
            ),
        ];

        let services = collect_naptr_services(entries);
        assert_eq!(services.len(), 3);
        assert_eq!(services[0].0, "srv0.example.com");
        assert_eq!(services[0].1, TransportProtocol::Tls);
        assert_eq!(services[1].0, "srv1.example.com");
        assert_eq!(services[1].1, TransportProtocol::Udp);
        assert_eq!(services[2].0, "srv2.example.com");
        assert_eq!(services[2].1, TransportProtocol::Tcp);
    }

    #[test]
    fn test_collect_naptr_records_filters_non_naptr() {
        init_tracing();
        let name = Name::from_ascii("example.com").unwrap();
        let replacement = Name::from_ascii("_sip._udp.example.com").unwrap();
        let naptr = NAPTR::new(
            10,
            5,
            b"s".to_vec().into_boxed_slice(),
            b"SIP+D2U".to_vec().into_boxed_slice(),
            Vec::new().into_boxed_slice(),
            replacement,
        );
        let naptr_record = Record::from_rdata(name.clone(), 60, RData::NAPTR(naptr));
        let a_record = Record::from_rdata(name.clone(), 60, RData::A(A::new(127, 0, 0, 1)));
        let empty_record = Record::with(name, RecordType::A, 60);

        let services = collect_naptr_records([naptr_record, a_record, empty_record].iter());
        assert_eq!(services.len(), 1);
        assert_eq!(services[0].0.trim_end_matches('.'), "_sip._udp.example.com");
        assert_eq!(services[0].1, TransportProtocol::Udp);
    }

    #[test]
    fn test_build_address_targets_empty() {
        let err =
            build_address_targets("example.com", TransportProtocol::Udp, Vec::new()).unwrap_err();
        assert!(format!("{err:?}").contains("NoRecords"));
    }

    #[test]
    fn test_build_address_targets_tls_port() {
        let targets = build_address_targets(
            "example.com",
            TransportProtocol::Tls,
            vec!["::1".parse().unwrap()],
        )
        .unwrap();
        assert_eq!(targets.len(), 1);
        assert_eq!(targets[0].port, 5061);
        assert_eq!(targets[0].transport, TransportProtocol::Tls);
    }

    // URI parsing edge cases
    #[tokio::test]
    async fn test_resolve_uri_case_insensitive_transport() {
        let resolver = SipResolver::new().await.unwrap();

        // Test uppercase transport parameter
        let targets = resolver
            .resolve_uri("sip:user@192.168.1.1:5060;transport=TCP")
            .await;
        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].transport, TransportProtocol::Tcp);

        // Test mixed case
        let targets = resolver
            .resolve_uri("sip:user@192.168.1.1:5060;transport=TlS")
            .await;
        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].transport, TransportProtocol::Tls);
    }

    #[tokio::test]
    async fn test_resolve_uri_with_ipv6_address() {
        let resolver = SipResolver::new().await.unwrap();

        let targets = resolver.resolve_uri("sip:user@[::1]:5060").await.unwrap();
        assert_eq!(targets[0].host, "[::1]");
        assert_eq!(targets[0].port, 5060);
        assert_eq!(targets[0].transport, TransportProtocol::Udp);
    }

    #[test]
    fn test_parse_sip_uri_internal_bracketed_ipv6_with_port() {
        let (host, port, transport) =
            parse_sip_uri_internal("sip:user@[2001:db8::1]:5070;transport=tls");
        assert_eq!(host, "[2001:db8::1]");
        assert_eq!(port, Some(5070));
        assert_eq!(transport, Some(TransportProtocol::Tls));
    }

    #[test]
    fn test_parse_sip_uri_internal_bracketed_ipv6_without_port() {
        let (host, port, transport) =
            parse_sip_uri_internal("sip:user@[2001:db8::1];transport=udp");
        assert_eq!(host, "[2001:db8::1]");
        assert_eq!(port, None);
        assert_eq!(transport, Some(TransportProtocol::Udp));
    }

    #[test]
    fn test_parse_sip_uri_internal_bracketed_ipv6_extra_suffix() {
        let (host, port, transport) =
            parse_sip_uri_internal("sip:user@[2001:db8::1]extra;transport=udp");
        assert_eq!(host, "[2001:db8::1]extra");
        assert_eq!(port, None);
        assert_eq!(transport, Some(TransportProtocol::Udp));
    }

    #[test]
    fn test_parse_sip_uri_internal_bracketed_ipv6_malformed() {
        let (host, port, transport) = parse_sip_uri_internal("sip:user@[2001:db8::1");
        assert_eq!(host, "[2001:db8::1");
        assert_eq!(port, None);
        assert_eq!(transport, None);
    }

    #[test]
    fn test_parse_sip_uri_internal_unknown_transport() {
        let (host, port, transport) =
            parse_sip_uri_internal("sip:user@127.0.0.1:5060;transport=sctp");
        assert_eq!(host, "127.0.0.1");
        assert_eq!(port, Some(5060));
        assert_eq!(transport, None);
    }

    #[tokio::test]
    async fn test_resolve_uri_trailing_semicolon() {
        let resolver = SipResolver::new().await.unwrap();

        let targets = resolver.resolve_uri("sip:user@192.168.1.1:5060;").await;
        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].host, "192.168.1.1");
        assert_eq!(targets[0].port, 5060);
    }

    fn sample_target(host: &str, transport: TransportProtocol) -> ResolvedTarget {
        ResolvedTarget {
            host: host.to_string(),
            port: 5060,
            transport,
            priority: 0,
            weight: 0,
            addresses: vec![],
        }
    }

    #[tokio::test]
    async fn test_resolve_with_naptr_success() {
        let mut lookup_naptr = |_domain: String| {
            boxed(async {
                Ok(vec![(
                    "_sip._udp.example.com".to_string(),
                    TransportProtocol::Udp,
                )])
            })
        };
        let mut lookup_srv = |srv_name: String, transport: TransportProtocol| {
            boxed(async move {
                assert_eq!(srv_name, "_sip._udp.example.com");
                Ok(vec![sample_target("udp.example.com", transport)])
            })
        };
        let mut lookup_addr = |_domain: String, _transport: TransportProtocol| {
            boxed(async { Err(ResolverError::NoRecords("addr".to_string())) })
        };

        let _ = lookup_addr("example.com".to_string(), TransportProtocol::Udp).await;
        let targets = resolve_with(
            "example.com",
            None,
            &mut lookup_naptr,
            &mut lookup_srv,
            &mut lookup_addr,
        )
        .await
        .unwrap();
        assert_eq!(targets.len(), 1);
        assert_eq!(targets[0].transport, TransportProtocol::Udp);
    }

    #[tokio::test]
    async fn test_resolve_with_naptr_preferred_transport_skips() {
        let mut lookup_naptr = |_domain: String| {
            boxed(async {
                Ok(vec![
                    ("_sip._udp.example.com".to_string(), TransportProtocol::Udp),
                    ("_sip._tcp.example.com".to_string(), TransportProtocol::Tcp),
                ])
            })
        };
        let mut lookup_srv = |srv_name: String, _transport: TransportProtocol| {
            boxed(async move { Ok(vec![sample_target(&srv_name, TransportProtocol::Tcp)]) })
        };
        let mut lookup_addr = |_domain: String, _transport: TransportProtocol| {
            boxed(async { Err(ResolverError::NoRecords("addr".to_string())) })
        };

        let _ = lookup_addr("example.com".to_string(), TransportProtocol::Udp).await;
        let targets = resolve_with(
            "example.com",
            Some(TransportProtocol::Tcp),
            &mut lookup_naptr,
            &mut lookup_srv,
            &mut lookup_addr,
        )
        .await
        .unwrap();
        assert_eq!(targets.len(), 1);
        assert_eq!(targets[0].transport, TransportProtocol::Tcp);
    }

    #[tokio::test]
    async fn test_resolve_from_naptr_inner_errors_when_empty() {
        let naptr_results = vec![("_sip._udp.example.com".to_string(), TransportProtocol::Udp)];
        let mut lookup_srv = |srv_name: String, _transport: TransportProtocol| {
            boxed(async move { Err(ResolverError::InvalidDomain(srv_name)) })
        };

        let err = resolve_from_naptr_inner(naptr_results, None, &mut lookup_srv)
            .await
            .err()
            .unwrap();
        assert!(format!("{err:?}").contains("NoRecords"));
    }

    #[tokio::test]
    async fn test_resolve_from_naptr_inner_ignores_lookup_errors() {
        let naptr_results = vec![
            ("_sip._udp.example.com".to_string(), TransportProtocol::Udp),
            ("_sip._tcp.example.com".to_string(), TransportProtocol::Tcp),
        ];
        let mut lookup_srv = |srv_name: String, transport: TransportProtocol| {
            boxed(async move {
                if transport == TransportProtocol::Udp {
                    Err(ResolverError::InvalidDomain(srv_name))
                } else {
                    Ok(vec![sample_target(&srv_name, transport)])
                }
            })
        };

        let targets = resolve_from_naptr_inner(naptr_results, None, &mut lookup_srv)
            .await
            .unwrap();
        assert_eq!(targets.len(), 1);
        assert_eq!(targets[0].transport, TransportProtocol::Tcp);
    }

    #[tokio::test]
    async fn test_resolve_with_srv_fallback_order() {
        let mut lookup_naptr = |_domain: String| {
            boxed(async { Ok::<Vec<(String, TransportProtocol)>, ResolverError>(Vec::new()) })
        };
        let mut lookup_srv = |srv_name: String, transport: TransportProtocol| {
            boxed(async move {
                if transport == TransportProtocol::Udp {
                    Ok(vec![sample_target(&srv_name, transport)])
                } else {
                    Ok(Vec::new())
                }
            })
        };
        let mut lookup_addr = |_domain: String, _transport: TransportProtocol| {
            boxed(async { Err(ResolverError::NoRecords("addr".to_string())) })
        };

        let _ = lookup_addr("example.com".to_string(), TransportProtocol::Udp).await;
        let targets = resolve_with(
            "example.com",
            None,
            &mut lookup_naptr,
            &mut lookup_srv,
            &mut lookup_addr,
        )
        .await
        .unwrap();
        assert_eq!(targets.len(), 1);
        assert_eq!(targets[0].transport, TransportProtocol::Udp);
    }

    #[tokio::test]
    async fn test_resolve_with_address_fallback() {
        let mut lookup_naptr = |_domain: String| {
            boxed(async { Err(ResolverError::InvalidDomain("fail".to_string())) })
        };
        let mut lookup_srv = |_srv_name: String, _transport: TransportProtocol| {
            boxed(async { Ok::<Vec<ResolvedTarget>, ResolverError>(Vec::new()) })
        };
        let mut lookup_addr = |domain: String, transport: TransportProtocol| {
            boxed(async move {
                Ok(vec![ResolvedTarget {
                    host: domain,
                    port: 5060,
                    transport,
                    priority: 0,
                    weight: 0,
                    addresses: vec!["127.0.0.1".parse().unwrap()],
                }])
            })
        };

        let targets = resolve_with(
            "example.com",
            Some(TransportProtocol::Udp),
            &mut lookup_naptr,
            &mut lookup_srv,
            &mut lookup_addr,
        )
        .await
        .unwrap();
        assert_eq!(targets.len(), 1);
        assert_eq!(targets[0].host, "example.com");
        assert_eq!(targets[0].transport, TransportProtocol::Udp);
    }

    #[tokio::test]
    async fn test_lookup_naptr_and_srv_with_local_dns() {
        init_tracing();
        let (dns_addr, shutdown_tx) = spawn_test_dns_server(false).await;
        let mut opts = ResolverOpts::default();
        opts.timeout = Duration::from_millis(200);
        opts.attempts = 1;
        opts.try_tcp_on_error = false;
        opts.ip_strategy = LookupIpStrategy::Ipv4Only;

        let name_servers =
            NameServerConfigGroup::from_ips_clear(&[dns_addr.ip()], dns_addr.port(), true);
        let config = ResolverConfig::from_parts(None, vec![], name_servers);
        let resolver = SipResolver::with_config(config, opts);

        let naptr = resolver.lookup_naptr("example.test").await.unwrap();
        assert_eq!(naptr.len(), 1);
        assert_eq!(naptr[0].0, "_sip._udp.example.test.");
        assert_eq!(naptr[0].1, TransportProtocol::Udp);

        let targets = resolver
            .lookup_srv("_sip._udp.example.test", TransportProtocol::Udp)
            .await
            .unwrap();
        assert_eq!(targets.len(), 1);
        assert_eq!(targets[0].host, "srv.example.test");
        assert_eq!(targets[0].port, 5060);
        assert_eq!(targets[0].addresses.len(), 1);
        let socket_addrs = targets[0].socket_addrs();
        assert_eq!(socket_addrs[0].port(), 5060);

        let _ = shutdown_tx.send(());
    }

    #[tokio::test]
    async fn test_lookup_srv_sorting_by_weight() {
        init_tracing();
        let (dns_addr, shutdown_tx) = spawn_test_dns_server(false).await;
        let mut opts = ResolverOpts::default();
        opts.timeout = Duration::from_millis(200);
        opts.attempts = 1;
        opts.try_tcp_on_error = false;
        opts.ip_strategy = LookupIpStrategy::Ipv4Only;

        let name_servers =
            NameServerConfigGroup::from_ips_clear(&[dns_addr.ip()], dns_addr.port(), true);
        let config = ResolverConfig::from_parts(None, vec![], name_servers);
        let resolver = SipResolver::with_config(config, opts);

        let targets = resolver
            .lookup_srv("_sip._udp.multi.test", TransportProtocol::Udp)
            .await
            .unwrap();
        assert_eq!(targets.len(), 2);
        assert_eq!(targets[0].host, "srv2.multi.test");
        assert_eq!(targets[1].host, "srv1.multi.test");

        let _ = shutdown_tx.send(());
    }

    #[tokio::test]
    async fn test_resolve_uri_empty_transport_param() {
        let resolver = SipResolver::new().await.unwrap();

        // transport= with no value should be handled gracefully
        let targets = resolver
            .resolve_uri("sip:user@192.168.1.1:5060;transport=")
            .await;
        assert!(targets.is_ok());
        // Should default to UDP when transport is invalid
        let targets = targets.unwrap();
        assert_eq!(targets[0].transport, TransportProtocol::Udp);
    }

    #[tokio::test]
    async fn test_resolve_uri_other_params_ignored() {
        let resolver = SipResolver::new().await.unwrap();

        // Other parameters should be ignored
        let targets = resolver
            .resolve_uri("sip:user@192.168.1.1:5060;lr;maddr=10.0.0.1;ttl=1")
            .await;
        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].host, "192.168.1.1");
        assert_eq!(targets[0].port, 5060);
    }

    #[tokio::test]
    async fn test_resolve_uri_no_scheme() {
        let resolver = SipResolver::new().await.unwrap();

        // URI without sip: or sips: prefix
        let targets = resolver.resolve_uri("user@192.168.1.1:5060").await;
        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].host, "192.168.1.1");
        assert_eq!(targets[0].port, 5060);
    }

    #[tokio::test]
    async fn test_resolve_uri_complex_username() {
        let resolver = SipResolver::new().await.unwrap();

        // Username with special characters
        let targets = resolver.resolve_uri("sip:user+name@192.168.1.1:5060").await;
        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].host, "192.168.1.1");
    }

    // Error handling and edge cases
    #[tokio::test]
    async fn test_lookup_address_empty_addresses() {
        let resolver = SipResolver::new().await.unwrap();

        // Try to resolve an invalid/nonexistent IP-like string
        // This should fail since it's not a valid IP
        let result = resolver
            .lookup_address(
                "not.a.valid.ip.address.that.does.not.exist.example",
                TransportProtocol::Udp,
            )
            .await;

        // Should return an error
        assert!(result.is_err());
    }

    #[tokio::test]
    async fn test_resolve_addresses_invalid_hostname() {
        let resolver = SipResolver::new().await.unwrap();

        // Invalid hostname that can't be resolved
        let result = resolver
            .resolve_addresses("this-domain-definitely-does-not-exist-12345.invalid")
            .await;

        // Should return an error
        assert!(result.is_err());
    }

    #[tokio::test]
    async fn test_resolve_with_all_transports_fallback() {
        let resolver = SipResolver::new().await.unwrap();

        // When no preferred transport is specified and no SRV records exist,
        // it should try TLS, TCP, then UDP and fall back to A/AAAA
        let targets = resolver.resolve("127.0.0.1", None).await;
        assert!(targets.is_ok());
        let targets = targets.unwrap();
        // Should fall back to default UDP with port 5060
        assert_eq!(targets[0].port, 5060);
    }

    #[tokio::test]
    async fn test_resolve_ipv6_loopback() {
        let resolver = SipResolver::new().await.unwrap();

        let targets = resolver.resolve("::1", Some(TransportProtocol::Tcp)).await;
        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].transport, TransportProtocol::Tcp);
        assert_eq!(targets[0].addresses[0], "::1".parse::<IpAddr>().unwrap());
    }

    #[tokio::test]
    async fn test_lookup_address_sets_correct_metadata() {
        let resolver = SipResolver::new().await.unwrap();

        let targets = resolver
            .lookup_address("192.168.1.1", TransportProtocol::Udp)
            .await
            .unwrap();

        assert_eq!(targets.len(), 1);
        assert_eq!(targets[0].host, "192.168.1.1");
        assert_eq!(targets[0].port, 5060);
        assert_eq!(targets[0].transport, TransportProtocol::Udp);
        assert_eq!(targets[0].priority, 0);
        assert_eq!(targets[0].weight, 0);
        assert_eq!(targets[0].addresses.len(), 1);
    }

    #[tokio::test]
    async fn test_lookup_address_tls_port() {
        let resolver = SipResolver::new().await.unwrap();

        let targets = resolver
            .lookup_address("10.0.0.1", TransportProtocol::Tls)
            .await
            .unwrap();

        assert_eq!(targets[0].port, 5061);
        assert_eq!(targets[0].transport, TransportProtocol::Tls);
    }

    // ResolvedTarget additional tests
    #[test]
    fn test_resolved_target_with_multiple_addresses() {
        let target = ResolvedTarget {
            host: "multi.example.com".to_string(),
            port: 5060,
            transport: TransportProtocol::Udp,
            priority: 10,
            weight: 100,
            addresses: vec![
                "192.168.1.1".parse().unwrap(),
                "192.168.1.2".parse().unwrap(),
                "192.168.1.3".parse().unwrap(),
                "2001:db8::1".parse().unwrap(),
            ],
        };

        let addrs = target.socket_addrs();
        assert_eq!(addrs.len(), 4);
        assert_eq!(addrs[0].port(), 5060);
        assert_eq!(addrs[1].port(), 5060);
        assert_eq!(addrs[2].port(), 5060);
        assert_eq!(addrs[3].port(), 5060);
    }

    #[test]
    fn test_resolved_target_fields() {
        let target = ResolvedTarget {
            host: "test.example.com".to_string(),
            port: 5070,
            transport: TransportProtocol::Tcp,
            priority: 25,
            weight: 75,
            addresses: vec!["10.0.0.1".parse().unwrap()],
        };

        assert_eq!(target.host, "test.example.com");
        assert_eq!(target.port, 5070);
        assert_eq!(target.transport, TransportProtocol::Tcp);
        assert_eq!(target.priority, 25);
        assert_eq!(target.weight, 75);
        assert_eq!(target.addresses.len(), 1);
    }

    // Test resolver configuration
    #[test]
    fn test_resolver_with_custom_config() {
        let config = ResolverConfig::default();
        let mut opts = ResolverOpts::default();
        opts.timeout = std::time::Duration::from_secs(5);

        let _resolver = SipResolver::with_config(config.clone(), opts.clone());
        // Should not panic
    }

    // Edge case: URI with no @ symbol
    #[tokio::test]
    async fn test_resolve_uri_bare_domain() {
        let resolver = SipResolver::new().await.unwrap();

        let targets = resolver.resolve_uri("sip:192.168.1.1:5060").await;
        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].host, "192.168.1.1");
        assert_eq!(targets[0].port, 5060);
    }

    // Test default transport when none specified
    #[tokio::test]
    async fn test_resolve_uri_default_transport() {
        let resolver = SipResolver::new().await.unwrap();

        let targets = resolver.resolve_uri("sip:user@192.168.1.1:5060").await;
        assert!(targets.is_ok());
        let targets = targets.unwrap();
        // Should default to UDP
        assert_eq!(targets[0].transport, TransportProtocol::Udp);
    }

    // Test port parsing edge cases
    #[tokio::test]
    async fn test_resolve_uri_invalid_port_ignored() {
        let resolver = SipResolver::new().await.unwrap();

        // Invalid port should be handled (parse fails, becomes None)
        let targets = resolver.resolve_uri("sip:user@127.0.0.1:99999").await;
        // Port parsing will fail for 99999 (> u16::MAX), so explicit_port = None
        // Falls back to resolve() which uses default ports
        assert!(targets.is_ok());
    }

    #[tokio::test]
    async fn test_resolve_uri_zero_port() {
        let resolver = SipResolver::new().await.unwrap();

        let targets = resolver.resolve_uri("sip:user@192.168.1.1:0").await;
        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].port, 0);
    }

    #[tokio::test]
    async fn test_resolve_uri_max_port() {
        let resolver = SipResolver::new().await.unwrap();

        let targets = resolver.resolve_uri("sip:user@192.168.1.1:65535").await;
        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].port, 65535);
    }

    // Test transport parameter edge cases
    #[tokio::test]
    async fn test_resolve_uri_transport_case_variations() {
        let resolver = SipResolver::new().await.unwrap();

        let test_cases = vec![
            ("transport=udp", TransportProtocol::Udp),
            ("transport=UDP", TransportProtocol::Udp),
            ("transport=tcp", TransportProtocol::Tcp),
            ("transport=TCP", TransportProtocol::Tcp),
            ("transport=tls", TransportProtocol::Tls),
            ("transport=TLS", TransportProtocol::Tls),
        ];

        for (param, expected) in test_cases {
            let uri = format!("sip:user@192.168.1.1:5060;{}", param);
            let targets = resolver.resolve_uri(&uri).await;
            assert!(targets.is_ok());
            let targets = targets.unwrap();
            assert_eq!(targets[0].transport, expected);
        }
    }

    // Test that resolve tries all transports in correct order
    #[tokio::test]
    async fn test_resolve_transport_preference_order() {
        let resolver = SipResolver::new().await.unwrap();

        // With no preferred transport and no SRV records, should try TLS, TCP, UDP
        // For IP addresses, it will skip SRV and go to A/AAAA lookup
        let targets = resolver.resolve("127.0.0.1", None).await;
        assert!(targets.is_ok());

        // The first match wins, and for IP it uses default (UDP in this case)
        let targets = targets.unwrap();
        assert!(!targets.is_empty());
    }

    // Additional error display tests
    #[test]
    fn test_resolver_error_display_formats() {
        let err = ResolverError::NoRecords("test.example.com".to_string());
        assert_eq!(err.to_string(), "no DNS records found for test.example.com");

        let err = ResolverError::InvalidDomain("bad..domain..example".to_string());
        assert_eq!(err.to_string(), "invalid domain: bad..domain..example");
    }

    // Test clone implementation
    #[test]
    fn test_resolved_target_clone_independence() {
        let target = ResolvedTarget {
            host: "original.example.com".to_string(),
            port: 5060,
            transport: TransportProtocol::Udp,
            priority: 10,
            weight: 100,
            addresses: vec!["192.168.1.1".parse().unwrap()],
        };

        let mut cloned = target.clone();

        // Modify clone
        cloned.host = "modified.example.com".to_string();
        cloned.port = 5070;

        // Original should be unchanged
        assert_eq!(target.host, "original.example.com");
        assert_eq!(target.port, 5060);
    }

    // Test socket_addrs with various IP types
    #[test]
    fn test_socket_addrs_ipv4_only() {
        let target = ResolvedTarget {
            host: "ipv4.example.com".to_string(),
            port: 5060,
            transport: TransportProtocol::Udp,
            priority: 0,
            weight: 0,
            addresses: vec!["10.0.0.1".parse().unwrap(), "10.0.0.2".parse().unwrap()],
        };

        let addrs = target.socket_addrs();
        assert!(addrs.iter().all(|a| a.is_ipv4()));
    }

    #[test]
    fn test_socket_addrs_ipv6_only() {
        let target = ResolvedTarget {
            host: "ipv6.example.com".to_string(),
            port: 5061,
            transport: TransportProtocol::Tls,
            priority: 0,
            weight: 0,
            addresses: vec![
                "2001:db8::1".parse().unwrap(),
                "2001:db8::2".parse().unwrap(),
            ],
        };

        let addrs = target.socket_addrs();
        assert!(addrs.iter().all(|a| a.is_ipv6()));
    }

    // Additional comprehensive tests for resolver coverage

    // Test error case where lookup_address gets empty addresses
    #[tokio::test]
    async fn test_lookup_address_with_invalid_domain() {
        let resolver = SipResolver::new().await.unwrap();

        // This should fail as it's an obviously invalid domain
        let result = resolver
            .lookup_address(
                "this.is.definitely.an.invalid.nonexistent.test.domain.12345",
                TransportProtocol::Udp,
            )
            .await;

        assert!(result.is_err());
        // Should be either ResolverError::LookupFailed or ResolverError::NoRecords
    }

    // Test the full resolve() method with transport fallback when no preferred transport
    #[tokio::test]
    async fn test_resolve_without_preferred_transport_ip() {
        let resolver = SipResolver::new().await.unwrap();

        // Using IP will skip SRV and go to A lookup
        let targets = resolver.resolve("127.0.0.1", None).await;

        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert!(!targets.is_empty());
        // Should default to UDP when no preference
        assert_eq!(targets[0].transport, TransportProtocol::Udp);
    }

    // Test resolve_uri that goes through resolve() path (no explicit port)
    #[tokio::test]
    async fn test_resolve_uri_without_port_uses_resolve_path() {
        let resolver = SipResolver::new().await.unwrap();

        // IP without port goes through resolve() -> lookup_address()
        let targets = resolver
            .resolve_uri("sip:user@127.0.0.1;transport=tcp")
            .await;

        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert!(!targets.is_empty());
        assert_eq!(targets[0].transport, TransportProtocol::Tcp);
        assert_eq!(targets[0].port, 5060); // Default TCP port
    }

    // Test resolve_uri with TLS transport and no port
    #[tokio::test]
    async fn test_resolve_uri_tls_without_port() {
        let resolver = SipResolver::new().await.unwrap();

        let targets = resolver
            .resolve_uri("sip:user@127.0.0.1;transport=tls")
            .await;

        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].transport, TransportProtocol::Tls);
        assert_eq!(targets[0].port, 5061); // Default TLS port
    }

    // Test URI parsing with equals sign in parameter value
    #[tokio::test]
    async fn test_resolve_uri_param_with_equals() {
        let resolver = SipResolver::new().await.unwrap();

        // Make sure transport parameter is still found even with other params
        let targets = resolver
            .resolve_uri("sip:user@192.168.1.1:5060;foo=bar=baz;transport=tcp;other=val")
            .await;

        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].transport, TransportProtocol::Tcp);
    }

    // Test the transport selection logic in resolve() when preferred is Some
    #[tokio::test]
    async fn test_resolve_with_udp_transport_preference() {
        let resolver = SipResolver::new().await.unwrap();

        let targets = resolver
            .resolve("127.0.0.1", Some(TransportProtocol::Udp))
            .await;

        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].transport, TransportProtocol::Udp);
        assert_eq!(targets[0].port, 5060);
    }

    // Test resolve with TLS preference
    #[tokio::test]
    async fn test_resolve_with_tls_transport_preference() {
        let resolver = SipResolver::new().await.unwrap();

        let targets = resolver
            .resolve("127.0.0.1", Some(TransportProtocol::Tls))
            .await;

        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].transport, TransportProtocol::Tls);
        assert_eq!(targets[0].port, 5061);
    }

    // Test ResolverError From trait
    #[test]
    fn test_resolver_error_from_hickory_error() {
        use hickory_resolver::error::ResolveErrorKind;

        let hickory_err =
            hickory_resolver::error::ResolveError::from(ResolveErrorKind::NoRecordsFound {
                query: Box::new(hickory_resolver::proto::op::Query::new()),
                soa: None,
                negative_ttl: None,
                response_code: hickory_resolver::proto::op::ResponseCode::NXDomain,
                trusted: false,
            });

        let resolver_err: ResolverError = hickory_err.into();

        // Should be converted to ResolverError::LookupFailed
        assert!(format!("{resolver_err:?}").contains("LookupFailed"));
    }

    // Test the default ports for different transports in lookup_address
    #[tokio::test]
    async fn test_lookup_address_port_selection() {
        let resolver = SipResolver::new().await.unwrap();

        // UDP -> 5060
        let targets_udp = resolver
            .lookup_address("127.0.0.1", TransportProtocol::Udp)
            .await
            .unwrap();
        assert_eq!(targets_udp[0].port, 5060);

        // TCP -> 5060
        let targets_tcp = resolver
            .lookup_address("127.0.0.1", TransportProtocol::Tcp)
            .await
            .unwrap();
        assert_eq!(targets_tcp[0].port, 5060);

        // TLS -> 5061
        let targets_tls = resolver
            .lookup_address("127.0.0.1", TransportProtocol::Tls)
            .await
            .unwrap();
        assert_eq!(targets_tls[0].port, 5061);
    }

    // Test resolve_addresses with IPv6
    #[tokio::test]
    async fn test_resolve_addresses_with_ipv6() {
        let resolver = SipResolver::new().await.unwrap();

        let addrs = resolver.resolve_addresses("::1").await.unwrap();
        assert_eq!(addrs.len(), 1);
        assert!(addrs[0].is_ipv6());
        assert_eq!(addrs[0], "::1".parse::<IpAddr>().unwrap());
    }

    // Test resolve_addresses with IPv4
    #[tokio::test]
    async fn test_resolve_addresses_with_ipv4() {
        let resolver = SipResolver::new().await.unwrap();

        let addrs = resolver.resolve_addresses("127.0.0.1").await.unwrap();
        assert_eq!(addrs.len(), 1);
        assert!(addrs[0].is_ipv4());
        assert_eq!(addrs[0], "127.0.0.1".parse::<IpAddr>().unwrap());
    }

    // Test URI parsing edge case - just an IP
    #[tokio::test]
    async fn test_resolve_uri_just_ip_with_port() {
        let resolver = SipResolver::new().await.unwrap();

        let targets = resolver.resolve_uri("192.168.1.1:5090").await;

        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].host, "192.168.1.1");
        assert_eq!(targets[0].port, 5090);
    }

    // Test that empty addresses list in lookup_address returns NoRecords error
    #[tokio::test]
    async fn test_lookup_address_no_addresses_returns_error() {
        let resolver = SipResolver::new().await.unwrap();

        // Try to resolve a nonexistent domain
        let result = resolver
            .lookup_address(
                "nonexistent-domain-that-definitely-does-not-exist-12345.invalid",
                TransportProtocol::Udp,
            )
            .await;

        assert!(result.is_err());
    }

    // Test resolve_uri with mixed case TRANSPORT parameter
    #[tokio::test]
    async fn test_resolve_uri_mixed_case_transport_param_key() {
        let resolver = SipResolver::new().await.unwrap();

        // Test that Transport (mixed case) is handled
        let targets = resolver
            .resolve_uri("sip:user@192.168.1.1:5060;Transport=tcp")
            .await;

        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].transport, TransportProtocol::Tcp);
    }

    // Test resolve_uri with all uppercase TRANSPORT parameter
    #[tokio::test]
    async fn test_resolve_uri_uppercase_transport_param_key() {
        let resolver = SipResolver::new().await.unwrap();

        let targets = resolver
            .resolve_uri("sip:user@192.168.1.1:5060;TRANSPORT=UDP")
            .await;

        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].transport, TransportProtocol::Udp);
    }

    // Test ResolvedTarget with various transport types
    #[test]
    fn test_resolved_target_with_all_transports() {
        let transports = vec![
            TransportProtocol::Udp,
            TransportProtocol::Tcp,
            TransportProtocol::Tls,
        ];

        for transport in transports {
            let target = ResolvedTarget {
                host: "test.com".to_string(),
                port: 5060,
                transport,
                priority: 0,
                weight: 0,
                addresses: vec![],
            };

            assert_eq!(target.transport, transport);
        }
    }

    // Test error display for all error variants
    #[test]
    fn test_all_resolver_error_variants_display() {
        // NoRecords
        let err1 = ResolverError::NoRecords("test.com".to_string());
        assert!(err1.to_string().contains("test.com"));
        assert!(err1.to_string().contains("no DNS records"));

        // InvalidDomain
        let err2 = ResolverError::InvalidDomain("bad.domain".to_string());
        assert!(err2.to_string().contains("bad.domain"));
        assert!(err2.to_string().contains("invalid domain"));
    }

    // Test resolve_uri with no transport parameter defaults to UDP
    #[tokio::test]
    async fn test_resolve_uri_no_transport_defaults_to_udp() {
        let resolver = SipResolver::new().await.unwrap();

        let targets = resolver.resolve_uri("sip:user@192.168.1.1:5060").await;

        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].transport, TransportProtocol::Udp);
    }

    // Test socket_addrs with different port numbers
    #[test]
    fn test_socket_addrs_various_ports() {
        let ports = vec![5060, 5061, 5080, 8080, 65535];

        for port in ports {
            let target = ResolvedTarget {
                host: "test.com".to_string(),
                port,
                transport: TransportProtocol::Udp,
                priority: 0,
                weight: 0,
                addresses: vec!["192.168.1.1".parse().unwrap()],
            };

            let addrs = target.socket_addrs();
            assert_eq!(addrs[0].port(), port);
        }
    }

    // Test that ResolvedTarget fields are accessible
    #[test]
    fn test_resolved_target_field_access() {
        let target = ResolvedTarget {
            host: "sip.example.com".to_string(),
            port: 5060,
            transport: TransportProtocol::Tcp,
            priority: 10,
            weight: 100,
            addresses: vec!["192.168.1.1".parse().unwrap()],
        };

        // Verify all fields are readable
        let _ = &target.host;
        let _ = target.port;
        let _ = target.transport;
        let _ = target.priority;
        let _ = target.weight;
        let _ = &target.addresses;

        assert_eq!(target.host, "sip.example.com");
        assert_eq!(target.port, 5060);
    }

    // Test resolve_uri with port but no transport uses default
    #[tokio::test]
    async fn test_resolve_uri_port_no_transport() {
        let resolver = SipResolver::new().await.unwrap();

        let targets = resolver.resolve_uri("sip:user@192.168.1.1:5070").await;

        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].port, 5070);
        assert_eq!(targets[0].transport, TransportProtocol::Udp); // Default
    }

    // Test ResolvedTarget clone creates independent copy
    #[test]
    fn test_resolved_target_clone_with_addresses() {
        let original = ResolvedTarget {
            host: "original.com".to_string(),
            port: 5060,
            transport: TransportProtocol::Udp,
            priority: 10,
            weight: 100,
            addresses: vec![
                "192.168.1.1".parse().unwrap(),
                "192.168.1.2".parse().unwrap(),
            ],
        };

        let cloned = original.clone();

        assert_eq!(cloned.addresses.len(), 2);
        assert_eq!(cloned.addresses[0], original.addresses[0]);
        assert_eq!(cloned.addresses[1], original.addresses[1]);
    }

    // Test that custom resolver config works
    #[test]
    fn test_custom_resolver_config_creation() {
        let config = ResolverConfig::new();

        let mut opts = ResolverOpts::default();
        opts.timeout = std::time::Duration::from_secs(10);
        opts.attempts = 3;

        let _resolver = SipResolver::with_config(config, opts);
        // Just verify it doesn't panic
    }

    // Test resolve_uri parsing various edge cases
    #[tokio::test]
    async fn test_resolve_uri_parsing_variations() {
        let resolver = SipResolver::new().await.unwrap();

        // Test various URI formats to exercise the parsing logic
        let test_cases = vec![
            // (URI, expected_host, expected_port, expected_transport)
            (
                "sip:alice@127.0.0.1:5060",
                "127.0.0.1",
                5060,
                TransportProtocol::Udp,
            ),
            (
                "sips:bob@[::1]:5061;transport=tls",
                "[::1]",
                5061,
                TransportProtocol::Tls,
            ),
            (
                "sip:carol@192.0.2.10:5070;transport=tcp",
                "192.0.2.10",
                5070,
                TransportProtocol::Tcp,
            ),
        ];

        for (uri, expected_host, expected_port, expected_transport) in test_cases {
            let targets = resolver.resolve_uri(uri).await.unwrap();
            assert_eq!(targets[0].host, expected_host);
            assert_eq!(targets[0].port, expected_port);
            assert_eq!(targets[0].transport, expected_transport);
        }
    }

    // Test that trailing dots are handled in hostnames
    #[tokio::test]
    async fn test_resolve_addresses_with_trailing_dot() {
        let resolver = SipResolver::new().await.unwrap();

        // Hickory resolver should handle trailing dots
        let result = resolver.resolve_addresses("127.0.0.1.").await;
        // May succeed or fail depending on resolver behavior, but shouldn't panic
        let _ = result;
    }

    // Test resolve with different transport priorities
    #[tokio::test]
    async fn test_resolve_srv_name_generation() {
        let resolver = SipResolver::new().await.unwrap();

        // Test that resolve() generates correct SRV names for different transports
        // Using an invalid domain so it falls through to A/AAAA
        let result = resolver
            .resolve("nonexistent-test-12345.invalid", None)
            .await;

        // Should fail but exercise the SRV name generation code paths
        assert!(result.is_err());
    }

    // Test resolve with each specific transport to exercise SRV name generation
    #[tokio::test]
    async fn test_resolve_srv_names_for_each_transport() {
        let resolver = SipResolver::new().await.unwrap();

        // Test UDP - generates _sip._udp.domain
        let _ = resolver
            .resolve("test-udp.invalid", Some(TransportProtocol::Udp))
            .await;

        // Test TCP - generates _sip._tcp.domain
        let _ = resolver
            .resolve("test-tcp.invalid", Some(TransportProtocol::Tcp))
            .await;

        // Test TLS - generates _sips._tcp.domain
        let _ = resolver
            .resolve("test-tls.invalid", Some(TransportProtocol::Tls))
            .await;
    }

    // Test resolve_uri with @ symbol handling
    #[tokio::test]
    async fn test_resolve_uri_with_at_symbol() {
        let resolver = SipResolver::new().await.unwrap();

        // Multiple @ symbols should use the last one
        let targets = resolver
            .resolve_uri("sip:user@domain@192.168.1.1:5060")
            .await;
        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].host, "192.168.1.1");
    }

    // Test resolve_uri with no @ symbol
    #[tokio::test]
    async fn test_resolve_uri_without_at_symbol() {
        let resolver = SipResolver::new().await.unwrap();

        let targets = resolver.resolve_uri("sip:192.168.1.1:5060").await;
        assert!(targets.is_ok());
        let targets = targets.unwrap();
        assert_eq!(targets[0].host, "192.168.1.1");
    }

    // Test the semicolon parameter parsing
    #[tokio::test]
    async fn test_resolve_uri_parameter_parsing() {
        let resolver = SipResolver::new().await.unwrap();

        // No semicolon
        let targets = resolver.resolve_uri("sip:user@192.168.1.1:5060").await;
        assert!(targets.is_ok());

        // With semicolon but no transport
        let targets = resolver.resolve_uri("sip:user@192.168.1.1:5060;lr").await;
        assert!(targets.is_ok());

        // With multiple parameters
        let targets = resolver
            .resolve_uri("sip:user@192.168.1.1:5060;lr;transport=tcp;maddr=10.0.0.1")
            .await;
        assert!(targets.is_ok());
        assert_eq!(targets.unwrap()[0].transport, TransportProtocol::Tcp);
    }

    // Test error from trait for hickory resolver errors
    #[test]
    fn test_resolver_error_from_trait() {
        use hickory_resolver::error::{ResolveError, ResolveErrorKind};

        // Create a hickory error
        let hickory_err = ResolveError::from(ResolveErrorKind::NoRecordsFound {
            query: Box::new(hickory_resolver::proto::op::Query::new()),
            soa: None,
            negative_ttl: None,
            response_code: hickory_resolver::proto::op::ResponseCode::NXDomain,
            trusted: false,
        });

        // Convert to ResolverError
        let resolver_err: ResolverError = hickory_err.into();

        // Verify it's the LookupFailed variant
        assert!(format!("{resolver_err:?}").contains("LookupFailed"));
    }

    // Test ResolvedTarget Debug impl coverage
    #[test]
    fn test_resolved_target_debug_format() {
        let target = ResolvedTarget {
            host: "test.example.com".to_string(),
            port: 5060,
            transport: TransportProtocol::Tcp,
            priority: 10,
            weight: 100,
            addresses: vec!["192.168.1.1".parse().unwrap()],
        };

        let debug_str = format!("{:?}", target);
        assert!(debug_str.contains("ResolvedTarget"));
        assert!(debug_str.contains("test.example.com"));
    }

    // Test ResolverError Debug impl coverage
    #[test]
    fn test_resolver_error_debug_format() {
        let err = ResolverError::NoRecords("test.invalid".to_string());
        let debug_str = format!("{:?}", err);
        assert!(debug_str.contains("NoRecords"));
        assert!(debug_str.contains("test.invalid"));
    }

    // Test Clone impl for ResolvedTarget
    #[test]
    fn test_resolved_target_clone_deep_copy() {
        let original = ResolvedTarget {
            host: "original.com".to_string(),
            port: 5060,
            transport: TransportProtocol::Udp,
            priority: 10,
            weight: 100,
            addresses: vec!["192.168.1.1".parse().unwrap()],
        };

        let mut cloned = original.clone();
        cloned.host = "modified.com".to_string();
        cloned.addresses.push("192.168.1.2".parse().unwrap());

        // Original should be unchanged
        assert_eq!(original.host, "original.com");
        assert_eq!(original.addresses.len(), 1);

        // Clone should have modifications
        assert_eq!(cloned.host, "modified.com");
        assert_eq!(cloned.addresses.len(), 2);
    }

    // Tests for extracted internal functions
    #[test]
    fn test_parse_naptr_transport() {
        assert_eq!(
            parse_naptr_transport("SIP+D2U"),
            Some(TransportProtocol::Udp)
        );
        assert_eq!(
            parse_naptr_transport("sip+d2u"),
            Some(TransportProtocol::Udp)
        );
        assert_eq!(
            parse_naptr_transport("SIP+D2T"),
            Some(TransportProtocol::Tcp)
        );
        assert_eq!(
            parse_naptr_transport("sip+d2t"),
            Some(TransportProtocol::Tcp)
        );
        assert_eq!(
            parse_naptr_transport("SIPS+D2T"),
            Some(TransportProtocol::Tls)
        );
        assert_eq!(
            parse_naptr_transport("sips+d2t"),
            Some(TransportProtocol::Tls)
        );

        // Invalid cases
        assert_eq!(parse_naptr_transport("SIP+D2X"), None);
        assert_eq!(parse_naptr_transport(""), None);
        assert_eq!(parse_naptr_transport("unknown"), None);
    }

    #[test]
    fn test_parse_sip_uri_internal() {
        // Basic URI
        let (host, port, transport) = parse_sip_uri_internal("sip:example.com");
        assert_eq!(host, "example.com");
        assert_eq!(port, None);
        assert_eq!(transport, None);

        // With port
        let (host, port, transport) = parse_sip_uri_internal("sip:example.com:5060");
        assert_eq!(host, "example.com");
        assert_eq!(port, Some(5060));
        assert_eq!(transport, None);

        // With transport
        let (host, port, transport) = parse_sip_uri_internal("sip:example.com;transport=tcp");
        assert_eq!(host, "example.com");
        assert_eq!(port, None);
        assert_eq!(transport, Some(TransportProtocol::Tcp));

        // With port and transport
        let (host, port, transport) = parse_sip_uri_internal("sip:example.com:5060;transport=tls");
        assert_eq!(host, "example.com");
        assert_eq!(port, Some(5060));
        assert_eq!(transport, Some(TransportProtocol::Tls));

        // SIPS scheme
        let (host, port, transport) = parse_sip_uri_internal("sips:example.com");
        assert_eq!(host, "example.com");
        assert_eq!(port, None);
        assert_eq!(transport, None); // Transport is inferred by resolver logic later, not parser

        // Invalid port
        let (host, port, transport) = parse_sip_uri_internal("sip:example.com:invalid");
        assert_eq!(host, "example.com");
        assert_eq!(port, None);
        assert_eq!(transport, None);

        // Multiple parameters
        let (host, port, transport) =
            parse_sip_uri_internal("sip:example.com;foo=bar;transport=udp;baz");
        assert_eq!(host, "example.com");
        assert_eq!(port, None);
        assert_eq!(transport, Some(TransportProtocol::Udp));

        // Case insensitivity
        let (host, port, transport) = parse_sip_uri_internal("SIP:example.com;TRANSPORT=TCP");
        assert_eq!(host, "example.com");
        assert_eq!(port, None);
        assert_eq!(transport, Some(TransportProtocol::Tcp));

        // IPv6
        let (host, port, transport) = parse_sip_uri_internal("sip:[::1]:5060");
        assert_eq!(host, "[::1]");
        assert_eq!(port, Some(5060));
        assert_eq!(transport, None);
    }
}