librespot/core/src/apresolve.rs

const AP_FALLBACK: &'static str = "ap.spotify.com:443";
const APRESOLVE_ENDPOINT: &'static str = "http://apresolve.spotify.com/";

use futures::{Future, Stream};
use hyper::client::HttpConnector;
use hyper::{self, Client, Method, Request, Uri};
use hyper_proxy::{Intercept, Proxy, ProxyConnector};
use serde_json;
use std::str::FromStr;
use tokio_core::reactor::Handle;

error_chain!{}

#[derive(Clone, Debug, Serialize, Deserialize)]
pub struct APResolveData {
    ap_list: Vec<String>,
}

fn apresolve(handle: &Handle, proxy: &Option<String>) -> Box<Future<Item = String, Error = Error>> {
    let url = Uri::from_str(APRESOLVE_ENDPOINT).expect("invalid AP resolve URL");
    let use_proxy = proxy.is_some();

    let mut req = Request::new(Method::Get, url.clone());
    let response = match proxy {
        &Some(ref val) => {
            let proxy_url = Uri::from_str(&val).expect("invalid http proxy");
            let proxy = Proxy::new(Intercept::All, proxy_url);
            let connector = HttpConnector::new(4, handle);
            let proxy_connector = ProxyConnector::from_proxy_unsecured(connector, proxy);
            if let Some(headers) = proxy_connector.http_headers(&url) {
                req.headers_mut().extend(headers.iter());
                req.set_proxy(true);
            }
            let client = Client::configure().connector(proxy_connector).build(handle);
            client.request(req)
        }
        _ => {
            let client = Client::new(handle);
            client.request(req)
        }
    };

    let body = response.and_then(|response| {
        response.body().fold(Vec::new(), |mut acc, chunk| {
            acc.extend_from_slice(chunk.as_ref());
            Ok::<_, hyper::Error>(acc)
        })
    });
    let body = body.then(|result| result.chain_err(|| "HTTP error"));
    let body = body.and_then(|body| String::from_utf8(body).chain_err(|| "invalid UTF8 in response"));

    let data =
        body.and_then(|body| serde_json::from_str::<APResolveData>(&body).chain_err(|| "invalid JSON"));

    let ap = data.and_then(move |data| {
        let mut aps = data.ap_list.iter().filter(|ap| {
            if use_proxy {
                // It is unlikely that the proxy will accept CONNECT on anything other than 443.
                Uri::from_str(ap)
                    .ok()
                    .map_or(false, |uri| uri.port().map_or(false, |port| port == 443))
            } else {
                true
            }
        });

        let ap = aps.next().ok_or("empty AP List")?;
        Ok(ap.clone())
    });

    Box::new(ap)
}

pub(crate) fn apresolve_or_fallback<E>(
    handle: &Handle,
    proxy: &Option<String>,
) -> Box<Future<Item = String, Error = E>>
where
    E: 'static,
{
    let ap = apresolve(handle, proxy).or_else(|e| {
        warn!("Failed to resolve Access Point: {}", e.description());
        warn!("Using fallback \"{}\"", AP_FALLBACK);
        Ok(AP_FALLBACK.into())
    });

    Box::new(ap)
}