// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
use deno_core::ErrBox;
use std::future::Future;
use std::net::SocketAddr;
use std::net::ToSocketAddrs;
use std::pin::Pin;
use std::task::Context;
use std::task::Poll;

/// Resolve network address. Returns a future.
pub fn resolve_addr(hostname: &str, port: u16) -> ResolveAddrFuture {
  ResolveAddrFuture {
    hostname: hostname.to_string(),
    port,
  }
}

pub struct ResolveAddrFuture {
  hostname: String,
  port: u16,
}

impl Future for ResolveAddrFuture {
  type Output = Result<SocketAddr, ErrBox>;

  fn poll(self: Pin<&mut Self>, _cx: &mut Context) -> Poll<Self::Output> {
    let inner = self.get_mut();
    // The implementation of this is not actually async at the moment,
    // however we intend to use async DNS resolution in the future and
    // so we expose this as a future instead of Result.

    // Default to localhost if given just the port. Example: ":80"
    let addr: &str = if !inner.hostname.is_empty() {
      &inner.hostname
    } else {
      "0.0.0.0"
    };

    // If this looks like an ipv6 IP address. Example: "[2001:db8::1]"
    // Then we remove the brackets.
    let addr = if addr.starts_with('[') && addr.ends_with(']') {
      let l = addr.len() - 1;
      addr.get(1..l).unwrap()
    } else {
      addr
    };
    let addr_port_pair = (addr, inner.port);
    let r = addr_port_pair.to_socket_addrs().map_err(ErrBox::from);

    Poll::Ready(r.and_then(|mut iter| match iter.next() {
      Some(a) => Ok(a),
      None => panic!("There should be at least one result"),
    }))
  }
}

#[cfg(test)]
mod tests {
  use super::*;
  use futures::executor::block_on;
  use std::net::Ipv4Addr;
  use std::net::Ipv6Addr;
  use std::net::SocketAddrV4;
  use std::net::SocketAddrV6;

  #[test]
  fn resolve_addr1() {
    let expected =
      SocketAddr::V4(SocketAddrV4::new(Ipv4Addr::new(127, 0, 0, 1), 80));
    let actual = block_on(resolve_addr("127.0.0.1", 80)).unwrap();
    assert_eq!(actual, expected);
  }

  #[test]
  fn resolve_addr2() {
    let expected =
      SocketAddr::V4(SocketAddrV4::new(Ipv4Addr::new(0, 0, 0, 0), 80));
    let actual = block_on(resolve_addr("", 80)).unwrap();
    assert_eq!(actual, expected);
  }

  #[test]
  fn resolve_addr3() {
    let expected =
      SocketAddr::V4(SocketAddrV4::new(Ipv4Addr::new(192, 0, 2, 1), 25));
    let actual = block_on(resolve_addr("192.0.2.1", 25)).unwrap();
    assert_eq!(actual, expected);
  }

  #[test]
  fn resolve_addr_ipv6() {
    let expected = SocketAddr::V6(SocketAddrV6::new(
      Ipv6Addr::new(0x2001, 0xdb8, 0, 0, 0, 0, 0, 1),
      8080,
      0,
      0,
    ));
    let actual = block_on(resolve_addr("[2001:db8::1]", 8080)).unwrap();
    assert_eq!(actual, expected);
  }
}