nreplops-tool 0.0.7

// host_resolution.rs
// Copyright 2022 Matti Hänninen
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.

use std::{fs, io, net, path, thread, time};

use crate::{cli, error::Error};

pub fn resolve_host_from_args(
    host_arg: &cli::HostArg,
    wait_for: &Option<time::Duration>,
) -> Result<net::SocketAddr, Error> {
    use cli::HostArg::*;
    match host_arg {
        HostExpr(e) => resolve_from_host_expr(e),
        PortFile(f) => {
            if let Some(d) = wait_for {
                let deadline = time::SystemTime::now() + *d;
                loop {
                    match try_resolve_from_port_file(f.as_ref()) {
                        Ok(r) => return Ok(r),
                        Err(e) => match e {
                            Error::NotSpecified | Error::NotFound(_) => {
                                if time::SystemTime::now() >= deadline {
                                    return Err(Error::PortFileTimeout);
                                }
                            }
                            _ => return Err(e),
                        },
                    }
                    thread::sleep(time::Duration::from_millis(50));
                }
            } else {
                try_resolve_from_port_file(f.as_ref())
            }
        }
    }
}

fn try_resolve_from_port_file(
    given: Option<impl AsRef<path::Path>>,
) -> Result<net::SocketAddr, Error> {
    if let Some(f) = given {
        resolve_from_port_file(f)
    } else if let Some(ref f) = find_port_file().map_err(|_| Error::Unknown)? {
        resolve_from_port_file(f)
    } else {
        Err(Error::NotSpecified)
    }
}

fn find_port_file() -> io::Result<Option<path::PathBuf>> {
    let current_dir = path::PathBuf::from(".").canonicalize()?;
    for dir in current_dir.ancestors() {
        let mut path = path::PathBuf::from(dir);
        path.push(".nrepl-port");
        if path.is_file() {
            return Ok(Some(path));
        }
    }
    Ok(None)
}

fn resolve_from_host_expr(
    host_expr: &cli::HostExpr,
) -> Result<net::SocketAddr, Error> {
    use cli::HostExpr::*;
    match host_expr {
        Port(port) => resolve_from_domaint_and_port("localhost", *port),
        SocketAddr(addr) => Ok(*addr),
        DomainPort(domain, port) => {
            resolve_from_domaint_and_port(domain, *port)
        }
    }
}

fn resolve_from_domaint_and_port(
    domain: &str,
    port: u16,
) -> Result<net::SocketAddr, Error> {
    if let Ok(mut ips) = dns_lookup::lookup_host(domain) {
        // Prefer IPv4 addresses and 127.0.0.1, in particular.
        let ipv4_localhost = "127.0.0.1".parse::<net::IpAddr>().unwrap();
        ips.sort();
        let ip = ips
            .iter()
            .find(|ip| **ip == ipv4_localhost)
            .or_else(|| ips.first())
            .expect(
                r#"assumed that dns_loop::lookup_host would always \
                   result in non-empty IP list upon success"#,
            );
        Ok(net::SocketAddr::from((*ip, port)))
    } else {
        Err(Error::DomainNotFound(domain.to_owned()))
    }
}

fn resolve_from_port_file(
    path: impl AsRef<path::Path>,
) -> Result<net::SocketAddr, Error> {
    let path = path.as_ref();
    let host_expr = fs::read_to_string(path)
        .map_err(|e| {
            if e.kind() == io::ErrorKind::NotFound {
                Error::NotFound(path.to_string_lossy().into())
            } else {
                Error::CannotReadFile(path.to_string_lossy().into())
            }
        })?
        .trim()
        .parse::<cli::HostExpr>()
        .map_err(|_| {
            Error::CannotParsePortFile(path.to_string_lossy().into())
        })?;
    resolve_from_host_expr(&host_expr)
}