//! A very simple crate to use `letsencrypt.org` to serve an encrypted
//! website using warp.

use futures::channel::oneshot;
use futures::executor::block_on;
use warp::{Filter};

/// Run forever on the current thread, serving using TLS to serve on the given domain.
///
/// This function accepts a single [`warp::Filter`](warp::Filter)
/// which is the site to host.  `lets_encrypt` requires the capability
/// to serve port 80 and port 443.  It obtains TLS credentials from
/// `letsencrypt.org` and then serves up the site on port 443.  It
/// also serves redirects on port 80.  Errors are reported on stderr.
pub fn lets_encrypt<F>(service: F, email: &str, domain: &str) -> Result<(), acme_lib::Error>
where
    F: warp::Filter<Error = warp::Rejection> + Send + Sync + 'static,
    F::Extract: warp::reply::Reply,
    F: Clone,
{
    let domain = domain.to_string();

    let pem_name = format!("{}.pem", domain);
    let key_name = format!("{}.key", domain);

    // Use DirectoryUrl::LetsEncrypStaging for dev/testing.
    let url = acme_lib::DirectoryUrl::LetsEncrypt;

    // Save/load keys and certificates to current dir.
    let persist = acme_lib::persist::FilePersist::new(".");

    // Create a directory entrypoint.
    let dir = acme_lib::Directory::from_url(persist, url)?;

    // Reads the private account key from persistence, or
    // creates a new one before accessing the API to establish
    // that it's there.
    let acc = dir.account(email)?;

    // Order a new TLS certificate for a domain.
    let mut ord_new = acc.new_order(&domain, &[])?;

    loop {
        const TMIN: std::time::Duration = std::time::Duration::from_secs(60 * 60 * 24 * 30);
        println!(
            "The time to expiration of {:?} is {:?}",
            pem_name,
            time_to_expiration(&pem_name)
        );
        if time_to_expiration(&pem_name)
            .filter(|&t| t > TMIN)
            .is_none()
        {
            // If the ownership of the domain(s) have already been authorized
            // in a previous order, you might be able to skip validation. The
            // ACME API provider decides.
            let ord_csr = loop {
                // are we done?
                if let Some(ord_csr) = ord_new.confirm_validations() {
                    break ord_csr;
                }

                // Get the possible authorizations (for a single domain
                // this will only be one element).
                let auths = ord_new.authorizations()?;

                // For HTTP, the challenge is a text file that needs to
                // be placed in your web server's root:
                //
                // /var/www/.well-known/acme-challenge/<token>
                //
                // The important thing is that it's accessible over the
                // web for the domain(s) you are trying to get a
                // certificate for:
                //
                // http://mydomain.io/.well-known/acme-challenge/<token>
                let chall = auths[0].http_challenge();

                // The token is the filename.
                let token: &'static str = Box::leak(chall.http_token().to_string().into_boxed_str());

                // The proof is the contents of the file
                let proof = chall.http_proof();

                // Here you must do "something" to place
                // the file/contents in the correct place.
                // update_my_web_server(&path, &proof);
                let domain = domain.to_string();
                use std::str::FromStr;
                let token = warp::path!(".well-known" / "acme-challenge")
                    .and(warp::path(token))
                    .map(move || proof.clone());
                let redirect = warp::path::tail().map(move |path: warp::path::Tail| {
                    println!("redirecting to https://{}/{}", domain, path.as_str());
                    warp::redirect::redirect(
                        warp::http::Uri::from_str(&format!(
                            "https://{}/{}",
                            &domain,
                            path.as_str()
                        ))
                            .expect("problem with uri?"),
                    )
                });
                let (tx80, rx80) = oneshot::channel();
                std::thread::spawn(|| {
                    block_on(warp::serve(token.or(redirect))
                               .bind_with_graceful_shutdown(([0, 0, 0, 0], 80),  async { rx80.await.ok(); })
                               .1);
                });

                // After the file is accessible from the web, the calls
                // this to tell the ACME API to start checking the
                // existence of the proof.
                //
                // The order at ACME will change status to either
                // confirm ownership of the domain, or fail due to the
                // not finding the proof. To see the change, we poll
                // the API with 5000 milliseconds wait between.
                chall.validate(5000)?;
                tx80.send(()).unwrap(); // Now stop the server on port 80

                // Update the state against the ACME API.
                ord_new.refresh()?;
            };

            // Ownership is proven. Create a private/public key pair for the
            // certificate. These are provided for convenience, you can
            // provide your own keypair instead if you want.
            let (pkey_pri, pkey_pub) = acme_lib::create_p384_key();

            // Submit the CSR. This causes the ACME provider to enter a state
            // of "processing" that must be polled until the certificate is
            // either issued or rejected. Again we poll for the status change.
            let ord_cert =
                ord_csr.finalize_pkey(pkey_pri, pkey_pub, 5000)?;

            // Now download the certificate. Also stores the cert in the
            // persistence.
            let cert = ord_cert.download_and_save_cert()?;
            std::fs::write(&pem_name, cert.certificate())?;
            std::fs::write(&key_name, cert.private_key())?;
        }

        // Now we have working keys, let us use them!
        let (tx80, rx80) = oneshot::channel();
        {
            // First start the redirecting from port 80 to port 443.
            let domain = domain.to_string();
            use std::str::FromStr;
            let redirect = warp::path::tail().map(move |path: warp::path::Tail| {
                println!("redirecting to https://{}/{}", domain, path.as_str());
                warp::redirect::redirect(
                    warp::http::Uri::from_str(&format!(
                        "https://{}/{}",
                        &domain,
                        path.as_str()
                    ))
                        .expect("problem with uri?"),
                )
            });
            std::thread::spawn(|| {
                block_on(warp::serve(redirect)
                         .bind_with_graceful_shutdown(([0, 0, 0, 0], 80), async { rx80.await.ok(); })
                         .1);
            });
        }
        let (tx, rx) = oneshot::channel();
        {
            // Now start our actual site.
            let service = service.clone();
            let key_name = key_name.clone();
            let pem_name = pem_name.clone();
            std::thread::spawn(move || {
                block_on(warp::serve(service)
                         .tls()
                         .cert_path(&pem_name)
                         .key_path(&key_name)
                         .bind_with_graceful_shutdown(([0, 0, 0, 0], 443), async { rx.await.ok(); })
                         .1);
            });
        }

        // Now wait until it is time to grab a new certificate.
        if let Some(time_to_renew) = time_to_expiration(&pem_name).and_then(|x| x.checked_sub(TMIN))
        {
            println!("Sleeping for {:?} before renewing", time_to_renew);
            std::thread::sleep(time_to_renew);
            println!("Now it is time to renew!");
            tx.send(()).unwrap();
            tx80.send(()).unwrap();
            std::thread::sleep(std::time::Duration::from_secs(1)); // FIXME very hokey!
        } else if let Some(time_to_renew) = time_to_expiration(&pem_name) {
            // Presumably we already failed to renew, so let's
            // just keep using our current certificate as long
            // as we can!
            println!("Sleeping for {:?} before renewing", time_to_renew);
            std::thread::sleep(time_to_renew);
            println!("Now it is time to renew!");
            tx.send(()).unwrap();
            tx80.send(()).unwrap();
            std::thread::sleep(std::time::Duration::from_secs(1)); // FIXME very hokey!
        } else {
            println!("Uh oh... looks like we already are at our limit?");
            println!("Waiting an hour before trying again...");
            std::thread::sleep(std::time::Duration::from_secs(60 * 60));
        }
    }
}

fn time_to_expiration<P: AsRef<std::path::Path>>(p: P) -> Option<std::time::Duration> {
    let file = std::fs::File::open(p).ok()?;
    x509_parser::pem::Pem::read(std::io::BufReader::new(file))
        .ok()?
        .0
        .parse_x509()
        .ok()?
        .tbs_certificate
        .validity
        .time_to_expiration()
}