use hyper_util::client::legacy::connect::dns::Name as HyperName;

use tower_service::Service;

use std::collections::HashMap;

use std::future::Future;

use std::net::SocketAddr;

use std::pin::Pin;

use std::str::FromStr;

use std::sync::Arc;

use std::task::{Context, Poll};

use crate::error::BoxError;

/// Alias for an `Iterator` trait object over `SocketAddr`.

pub type Addrs = Box<dyn Iterator<Item = SocketAddr> + Send>;

/// Alias for the `Future` type returned by a DNS resolver.

pub type Resolving = Pin<Box<dyn Future<Output = Result<Addrs, BoxError>> + Send>>;

/// Trait for customizing DNS resolution in reqwest.

pub trait Resolve: Send + Sync {

    /// Performs DNS resolution on a `Name`.

    /// The return type is a future containing an iterator of `SocketAddr`.

    ///

    /// It differs from `tower_service::Service<Name>` in several ways:

    ///  * It is assumed that `resolve` will always be ready to poll.

    ///  * It does not need a mutable reference to `self`.

    ///  * Since trait objects cannot make use of associated types, it requires

    ///    wrapping the returned `Future` and its contained `Iterator` with `Box`.

    ///

    /// Explicitly specified port in the URL will override any port in the resolved `SocketAddr`s.

    /// Otherwise, port `0` will be replaced by the conventional port for the given scheme (e.g. 80 for http).

    fn resolve(&self, name: Name) -> Resolving;

}

/// A name that must be resolved to addresses.

#[derive(Debug)]

pub struct Name(pub(super) HyperName);

/// A more general trait implemented for types implementing `Resolve`.

///

/// Unnameable, only exported to aid seeing what implements this.

pub trait IntoResolve {

    #[doc(hidden)]

    fn into_resolve(self) -> Arc<dyn Resolve>;

}

impl Name {

    /// View the name as a string.

    pub fn as_str(&self) -> &str {

        self.0.as_str()

    }

}

impl FromStr for Name {

    type Err = sealed::InvalidNameError;

    fn from_str(host: &str) -> Result<Self, Self::Err> {

        HyperName::from_str(host)

            .map(Name)

            .map_err(|_| sealed::InvalidNameError { _ext: () })

    }

}

#[derive(Clone)]

pub(crate) struct DynResolver {

    resolver: Arc<dyn Resolve>,

}

impl DynResolver {

    pub(crate) fn new(resolver: Arc<dyn Resolve>) -> Self {

        Self { resolver }

    }

    #[cfg(feature = "socks")]

    pub(crate) fn gai() -> Self {

        Self::new(Arc::new(super::gai::GaiResolver::new()))

    }

    /// Resolve an HTTP host and port, not just a domain name.

    ///

    /// This does the same thing that hyper-util's HttpConnector does, before

    /// calling out to its underlying DNS resolver.

    #[cfg(feature = "socks")]

    pub(crate) async fn http_resolve(

        &self,

        target: &http::Uri,

    ) -> Result<impl Iterator<Item = std::net::SocketAddr>, BoxError> {

        let host = target.host().ok_or("missing host")?;

        let port = target

            .port_u16()

            .unwrap_or_else(|| match target.scheme_str() {

                Some("https") => 443,

                Some("socks4") | Some("socks4a") | Some("socks5") | Some("socks5h") => 1080,

                _ => 80,

            });

        let explicit_port = target.port().is_some();

        let addrs = self.resolver.resolve(host.parse()?).await?;

        Ok(addrs.map(move |mut addr| {

            if explicit_port || addr.port() == 0 {

                addr.set_port(port);

            }

            addr

        }))

    }

}

impl Service<HyperName> for DynResolver {

    type Response = Addrs;

    type Error = BoxError;

    type Future = Resolving;

    fn poll_ready(&mut self, _: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {

        Poll::Ready(Ok(()))

    }

    fn call(&mut self, name: HyperName) -> Self::Future {

        self.resolver.resolve(Name(name))

    }

}

pub(crate) struct DnsResolverWithOverrides {

    dns_resolver: Arc<dyn Resolve>,

    overrides: Arc<HashMap<String, Vec<SocketAddr>>>,

}

impl DnsResolverWithOverrides {

    pub(crate) fn new(

        dns_resolver: Arc<dyn Resolve>,

        overrides: HashMap<String, Vec<SocketAddr>>,

    ) -> Self {

        DnsResolverWithOverrides {

            dns_resolver,

            overrides: Arc::new(overrides),

        }

    }

}

impl Resolve for DnsResolverWithOverrides {

    fn resolve(&self, name: Name) -> Resolving {

        match self.overrides.get(name.as_str()) {

            Some(dest) => {

                let addrs: Addrs = Box::new(dest.clone().into_iter());

                Box::pin(std::future::ready(Ok(addrs)))

            }

            None => self.dns_resolver.resolve(name),

        }

    }

}

impl IntoResolve for Arc<dyn Resolve> {

    fn into_resolve(self) -> Arc<dyn Resolve> {

        self

    }

}

impl<R> IntoResolve for Arc<R>

where

    R: Resolve + 'static,

{

    fn into_resolve(self) -> Arc<dyn Resolve> {

        self

    }

}

impl<R> IntoResolve for R

where

    R: Resolve + 'static,

{

    fn into_resolve(self) -> Arc<dyn Resolve> {

        Arc::new(self)

    }

}

mod sealed {

    use std::fmt;

    #[derive(Debug)]

    pub struct InvalidNameError {

        pub(super) _ext: (),

    }

    impl fmt::Display for InvalidNameError {

        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

            f.write_str("invalid DNS name")

        }

    }

    impl std::error::Error for InvalidNameError {}

}