use std::net::ToSocketAddrs;

use actix_web::client::Client;
use actix_web::{middleware, web, App, Error, HttpRequest, HttpResponse, HttpServer};
use clap::{value_t, Arg};
use url::Url;

async fn forward(
    req: HttpRequest,
    body: web::Bytes,
    url: web::Data<Url>,
    client: web::Data<Client>,
) -> Result<HttpResponse, Error> {
    let mut new_url = url.get_ref().clone();
    new_url.set_path(req.uri().path());
    new_url.set_query(req.uri().query());

    // TODO: This forwarded implementation is incomplete as it only handles the inofficial
    // X-Forwarded-For header but not the official Forwarded one.
    let forwarded_req = client
        .request_from(new_url.as_str(), req.head())
        .no_decompress();
    let forwarded_req = if let Some(addr) = req.head().peer_addr {
        forwarded_req.header("x-forwarded-for", format!("{}", addr.ip()))
    } else {
        forwarded_req
    };

    let mut res = forwarded_req.send_body(body).await.map_err(Error::from)?;

    let mut client_resp = HttpResponse::build(res.status());
    // Remove `Connection` as per
    // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Connection#Directives
    for (header_name, header_value) in
        res.headers().iter().filter(|(h, _)| *h != "connection")
    {
        client_resp.header(header_name.clone(), header_value.clone());
    }

    Ok(client_resp.body(res.body().await?))
}

#[actix_rt::main]
async fn main() -> std::io::Result<()> {
    let matches = clap::App::new("HTTP Proxy")
        .arg(
            Arg::with_name("listen_addr")
                .takes_value(true)
                .value_name("LISTEN ADDR")
                .index(1)
                .required(true),
        )
        .arg(
            Arg::with_name("listen_port")
                .takes_value(true)
                .value_name("LISTEN PORT")
                .index(2)
                .required(true),
        )
        .arg(
            Arg::with_name("forward_addr")
                .takes_value(true)
                .value_name("FWD ADDR")
                .index(3)
                .required(true),
        )
        .arg(
            Arg::with_name("forward_port")
                .takes_value(true)
                .value_name("FWD PORT")
                .index(4)
                .required(true),
        )
        .get_matches();

    let listen_addr = matches.value_of("listen_addr").unwrap();
    let listen_port = value_t!(matches, "listen_port", u16).unwrap_or_else(|e| e.exit());

    let forwarded_addr = matches.value_of("forward_addr").unwrap();
    let forwarded_port =
        value_t!(matches, "forward_port", u16).unwrap_or_else(|e| e.exit());

    let forward_url = Url::parse(&format!(
        "http://{}",
        (forwarded_addr, forwarded_port)
            .to_socket_addrs()
            .unwrap()
            .next()
            .unwrap()
    ))
    .unwrap();

    HttpServer::new(move || {
        App::new()
            .data(Client::new())
            .data(forward_url.clone())
            .wrap(middleware::Logger::default())
            .default_service(web::route().to(forward))
    })
    .bind((listen_addr, listen_port))?
    .system_exit()
    .run()
    .await
}