use std::{future, pin, sync, time};

use crate::domain::{self, acme};
use crate::error;
use crate::error::{MapUnexpected, ToUnexpected};

const LETS_ENCRYPT_URL: &'static str = "https://acme-v02.api.letsencrypt.org/directory";

pub type GetHttp01ChallengeKeyError = acme::store::GetHttp01ChallengeKeyError;

#[mockall::automock(
    type SyncDomainFuture=future::Ready<Result<(), error::Unexpected>>;
)]
pub trait Manager {
    type SyncDomainFuture<'mgr>: future::Future<Output = Result<(), error::Unexpected>>
        + Send
        + Unpin
        + 'mgr
    where
        Self: 'mgr;

    fn sync_domain(&self, domain: domain::Name) -> Self::SyncDomainFuture<'_>;

    fn get_http01_challenge_key(&self, token: &str) -> Result<String, GetHttp01ChallengeKeyError>;
}

pub trait BoxedManager: Manager + Send + Sync + Clone + 'static {}

struct ManagerImpl<Store>
where
    Store: acme::store::BoxedStore,
{
    store: Store,
    account: sync::Arc<acme2::Account>,
}

pub async fn new<Store>(
    store: Store,
    contact_email: &str,
) -> Result<impl BoxedManager, error::Unexpected>
where
    Store: acme::store::BoxedStore,
{
    let dir = acme2::DirectoryBuilder::new(LETS_ENCRYPT_URL.to_string())
        .build()
        .await
        .map_unexpected()?;

    let mut contact = String::from("mailto:");
    contact.push_str(contact_email);

    let mut builder = acme2::AccountBuilder::new(dir);
    builder.contact(vec![contact]);
    builder.terms_of_service_agreed(true);

    match store.get_account_key() {
        Ok(account_key) => {
            builder.private_key(account_key);
        }
        Err(acme::store::GetAccountKeyError::NotFound) => (),
        Err(acme::store::GetAccountKeyError::Unexpected(err)) => return Err(err.to_unexpected()),
    }

    let account = builder.build().await.map_unexpected()?;

    store
        .set_account_key(&account.private_key())
        .map_unexpected()?;

    Ok(sync::Arc::new(ManagerImpl { store, account }))
}

impl<Store> BoxedManager for sync::Arc<ManagerImpl<Store>> where Store: acme::store::BoxedStore {}

impl<Store> Manager for sync::Arc<ManagerImpl<Store>>
where
    Store: acme::store::BoxedStore,
{
    type SyncDomainFuture<'mgr> = pin::Pin<Box<dyn future::Future<Output = Result<(), error::Unexpected>> + Send + 'mgr>>
        where Self: 'mgr;

    fn sync_domain(&self, domain: domain::Name) -> Self::SyncDomainFuture<'_> {
        // if there's an existing cert, and its expiry (determined by the soonest value of
        // not_after amongst its parts) is later than 30 days from now, then we consider it to be
        // synced.
        if let Ok(cert) = self.store.get_certificate(domain.as_str()) {
            let thirty_days = openssl::asn1::Asn1Time::days_from_now(30)
                .expect("parsed thirty days from now as Asn1Time");

            let soonest_not_after = cert[1..]
                .into_iter()
                .map(|cert_part| cert_part.not_after())
                .fold(cert[0].not_after(), |a, b| if a < b { a } else { b });

            if thirty_days < soonest_not_after {
                return Box::pin(future::ready(Ok(())));
            }
        }

        println!("fetching a new certificate for domain {}", domain.as_str());

        Box::pin(async move {
            let mut builder = acme2::OrderBuilder::new(self.account.clone());
            builder.add_dns_identifier(domain.as_str().to_string());
            let order = builder.build().await.map_unexpected()?;

            let authorizations = order.authorizations().await.map_unexpected()?;

            for auth in authorizations {
                let challenge = auth
                    .get_challenge("http-01")
                    .ok_or(error::Unexpected::from("expected http-01 challenge"))?;

                let challenge_token = challenge
                    .token
                    .as_ref()
                    .ok_or(error::Unexpected::from("expected challenge to have token"))?;

                let challenge_key = challenge
                    .key_authorization()
                    .map_unexpected()?
                    .ok_or(error::Unexpected::from("expected challenge to have key"))?;

                self.store
                    .set_http01_challenge_key(challenge_token, &challenge_key)
                    .map_unexpected()?;

                // At this point the manager is prepared to serve the challenge key via the
                // `get_http01_challenge_key` method. It is expected that there is some http
                // server, with this domain pointing at it, which is prepared to serve that
                // challenge token/key under the `/.well-known/acme-challenge` path. The
                // `validate()` call below will instigate the acme server to make this check, and
                // block until it succeeds.

                println!(
                    "waiting for ACME challenge to be validated for domain {}",
                    domain.as_str(),
                );
                let challenge = challenge.validate().await.map_unexpected()?;

                // Poll the challenge every 5 seconds until it is in either the
                // `valid` or `invalid` state.
                let challenge_res = challenge.wait_done(time::Duration::from_secs(5), 3).await;

                // no matter what the result is, clean up the challenge key
                self.store
                    .del_http01_challenge_key(&challenge_token)
                    .map_unexpected()?;

                let challenge = challenge_res.map_unexpected()?;

                if challenge.status != acme2::ChallengeStatus::Valid {
                    return Err(error::Unexpected::from(
                        format!(
                            "expected challenge status to be valid, instead it was {:?}",
                            challenge.status
                        )
                        .as_str(),
                    ));
                }

                // Poll the authorization every 5 seconds until it is in either the
                // `valid` or `invalid` state.
                println!(
                    "waiting for ACME authorization to be validated for domain {}",
                    domain.as_str(),
                );

                let authorization = auth
                    .wait_done(time::Duration::from_secs(5), 3)
                    .await
                    .map_unexpected()?;

                if authorization.status != acme2::AuthorizationStatus::Valid {
                    return Err(error::Unexpected::from(
                        format!(
                            "expected authorization status to be valid, instead it was {:?}",
                            authorization.status,
                        )
                        .as_str(),
                    ));
                }
            }

            // Poll the order every 5 seconds until it is in either the `ready` or `invalid` state.
            // Ready means that it is now ready for finalization (certificate creation).
            println!(
                "waiting for ACME order to be made ready for domain {}",
                domain.as_str(),
            );

            let order = order
                .wait_ready(time::Duration::from_secs(5), 3)
                .await
                .map_unexpected()?;

            if order.status != acme2::OrderStatus::Ready {
                return Err(error::Unexpected::from(
                    format!(
                        "expected order status to be ready, instead it was {:?}",
                        order.status,
                    )
                    .as_str(),
                ));
            }

            // Generate an RSA private key for the certificate.
            let pkey = acme2::gen_rsa_private_key(4096).map_unexpected()?;

            // Create a certificate signing request for the order, and request
            // the certificate.
            let order = order
                .finalize(acme2::Csr::Automatic(pkey))
                .await
                .map_unexpected()?;

            // Poll the order every 5 seconds until it is in either the
            // `valid` or `invalid` state. Valid means that the certificate
            // has been provisioned, and is now ready for download.
            println!(
                "waiting for ACME order to be validated for domain {}",
                domain.as_str(),
            );
            let order = order
                .wait_done(time::Duration::from_secs(5), 3)
                .await
                .map_unexpected()?;

            if order.status != acme2::OrderStatus::Valid {
                return Err(error::Unexpected::from(
                    format!(
                        "expected order status to be valid, instead it was {:?}",
                        order.status,
                    )
                    .as_str(),
                ));
            }

            // Download the certificate, and panic if it doesn't exist.
            println!("fetching certificate for domain {}", domain.as_str());
            let cert =
                order
                    .certificate()
                    .await
                    .map_unexpected()?
                    .ok_or(error::Unexpected::from(
                        "expected the order to return a certificate",
                    ))?;

            if cert.len() <= 1 {
                return Err(error::Unexpected::from(
                    format!(
                        "expected more than one certificate to be returned, instead got {}",
                        cert.len(),
                    )
                    .as_str(),
                ));
            }

            println!("certificate for {} successfully retrieved", domain.as_str());
            self.store
                .set_certificate(domain.as_str(), cert)
                .map_unexpected()?;

            Ok(())
        })
    }

    fn get_http01_challenge_key(&self, token: &str) -> Result<String, GetHttp01ChallengeKeyError> {
        self.store.get_http01_challenge_key(token)
    }
}