use std::future::Future;
use std::pin::Pin;
use std::process::Stdio;
use std::sync::Arc;

use anyhow::{bail, format_err, Error};
use hyper::{Body, Request, Response};
use tokio::io::{AsyncBufReadExt, AsyncRead, AsyncWriteExt, BufReader};
use tokio::process::Command;

use proxmox_acme_rs::{Authorization, Challenge};

use crate::acme::AcmeClient;
use crate::api2::types::AcmeDomain;
use crate::server::WorkerTask;

use crate::config::acme::plugin::{DnsPlugin, PluginData};

const PROXMOX_ACME_SH_PATH: &str = "/usr/share/proxmox-acme/proxmox-acme";

pub(crate) fn get_acme_plugin(
    plugin_data: &PluginData,
    name: &str,
) -> Result<Option<Box<dyn AcmePlugin + Send + Sync + 'static>>, Error> {
    let (ty, data) = match plugin_data.get(name) {
        Some(plugin) => plugin,
        None => return Ok(None),
    };

    Ok(Some(match ty.as_str() {
        "dns" => {
            let plugin: DnsPlugin = serde_json::from_value(data.clone())?;
            Box::new(plugin)
        }
        "standalone" => {
            // this one has no config
            Box::new(StandaloneServer::default())
        }
        other => bail!("missing implementation for plugin type '{}'", other),
    }))
}

pub(crate) trait AcmePlugin {
    /// Setup everything required to trigger the validation and return the corresponding validation
    /// URL.
    fn setup<'fut, 'a: 'fut, 'b: 'fut, 'c: 'fut, 'd: 'fut>(
        &'a mut self,
        client: &'b mut AcmeClient,
        authorization: &'c Authorization,
        domain: &'d AcmeDomain,
        task: Arc<WorkerTask>,
    ) -> Pin<Box<dyn Future<Output = Result<&'c str, Error>> + Send + 'fut>>;

    fn teardown<'fut, 'a: 'fut, 'b: 'fut, 'c: 'fut, 'd: 'fut>(
        &'a mut self,
        client: &'b mut AcmeClient,
        authorization: &'c Authorization,
        domain: &'d AcmeDomain,
        task: Arc<WorkerTask>,
    ) -> Pin<Box<dyn Future<Output = Result<(), Error>> + Send + 'fut>>;
}

fn extract_challenge<'a>(
    authorization: &'a Authorization,
    ty: &str,
) -> Result<&'a Challenge, Error> {
    authorization
        .challenges
        .iter()
        .find(|ch| ch.ty == ty)
        .ok_or_else(|| format_err!("no supported challenge type (dns-01) found"))
}

async fn pipe_to_tasklog<T: AsyncRead + Unpin>(
    pipe: T,
    task: Arc<WorkerTask>,
) -> Result<(), std::io::Error> {
    let mut pipe = BufReader::new(pipe);
    let mut line = String::new();
    loop {
        line.clear();
        match pipe.read_line(&mut line).await {
            Ok(0) => return Ok(()),
            Ok(_) => task.log(line.as_str()),
            Err(err) => return Err(err),
        }
    }
}

impl DnsPlugin {
    async fn action<'a>(
        &self,
        client: &mut AcmeClient,
        authorization: &'a Authorization,
        domain: &AcmeDomain,
        task: Arc<WorkerTask>,
        action: &str,
    ) -> Result<&'a str, Error> {
        let challenge = extract_challenge(authorization, "dns-01")?;
        let mut stdin_data = client
            .dns_01_txt_value(
                challenge
                    .token()
                    .ok_or_else(|| format_err!("missing token in challenge"))?,
            )?
            .into_bytes();
        stdin_data.push(b'\n');
        stdin_data.extend(self.data.as_bytes());
        if stdin_data.last() != Some(&b'\n') {
            stdin_data.push(b'\n');
        }

        let mut command = Command::new("/usr/bin/setpriv");

        #[rustfmt::skip]
        command.args(&[
            "--reuid", "nobody",
            "--regid", "nogroup",
            "--clear-groups",
            "--reset-env",
            "--",
            "/bin/bash",
                PROXMOX_ACME_SH_PATH,
                action,
                &self.core.api,
                domain.alias.as_deref().unwrap_or(&domain.domain),
        ]);

        // We could use 1 socketpair, but tokio wraps them all in `File` internally causing `close`
        // to be called separately on all of them without exception, so we need 3 pipes :-(

        let mut child = command
            .stdin(Stdio::piped())
            .stdout(Stdio::piped())
            .stderr(Stdio::piped())
            .spawn()?;

        let mut stdin = child.stdin.take().expect("Stdio::piped()");
        let stdout = child.stdout.take().expect("Stdio::piped() failed?");
        let stdout = pipe_to_tasklog(stdout, Arc::clone(&task));
        let stderr = child.stderr.take().expect("Stdio::piped() failed?");
        let stderr = pipe_to_tasklog(stderr, Arc::clone(&task));
        let stdin = async move {
            stdin.write_all(&stdin_data).await?;
            stdin.flush().await?;
            Ok::<_, std::io::Error>(())
        };
        match futures::try_join!(stdin, stdout, stderr) {
            Ok(((), (), ())) => (),
            Err(err) => {
                if let Err(err) = child.kill().await {
                    task.log(format!(
                        "failed to kill '{} {}' command: {}",
                        PROXMOX_ACME_SH_PATH, action, err
                    ));
                }
                bail!("'{}' failed: {}", PROXMOX_ACME_SH_PATH, err);
            }
        }

        let status = child.wait().await?;
        if !status.success() {
            bail!(
                "'{} {}' exited with error ({})",
                PROXMOX_ACME_SH_PATH,
                action,
                status.code().unwrap_or(-1)
            );
        }

        Ok(&challenge.url)
    }
}

impl AcmePlugin for DnsPlugin {
    fn setup<'fut, 'a: 'fut, 'b: 'fut, 'c: 'fut, 'd: 'fut>(
        &'a mut self,
        client: &'b mut AcmeClient,
        authorization: &'c Authorization,
        domain: &'d AcmeDomain,
        task: Arc<WorkerTask>,
    ) -> Pin<Box<dyn Future<Output = Result<&'c str, Error>> + Send + 'fut>> {
        Box::pin(self.action(client, authorization, domain, task, "setup"))
    }

    fn teardown<'fut, 'a: 'fut, 'b: 'fut, 'c: 'fut, 'd: 'fut>(
        &'a mut self,
        client: &'b mut AcmeClient,
        authorization: &'c Authorization,
        domain: &'d AcmeDomain,
        task: Arc<WorkerTask>,
    ) -> Pin<Box<dyn Future<Output = Result<(), Error>> + Send + 'fut>> {
        Box::pin(async move {
            self.action(client, authorization, domain, task, "teardown")
                .await
                .map(drop)
        })
    }
}

#[derive(Default)]
struct StandaloneServer {
    abort_handle: Option<futures::future::AbortHandle>,
}

// In case the "order_certificates" future gets dropped between setup & teardown, let's also cancel
// the HTTP listener on Drop:
impl Drop for StandaloneServer {
    fn drop(&mut self) {
        self.stop();
    }
}

impl StandaloneServer {
    fn stop(&mut self) {
        if let Some(abort) = self.abort_handle.take() {
            abort.abort();
        }
    }
}

async fn standalone_respond(
    req: Request<Body>,
    path: Arc<String>,
    key_auth: Arc<String>,
) -> Result<Response<Body>, hyper::Error> {
    if req.method() == hyper::Method::GET && req.uri().path() == path.as_str() {
        Ok(Response::builder()
            .status(http::StatusCode::OK)
            .body(key_auth.as_bytes().to_vec().into())
            .unwrap())
    } else {
        Ok(Response::builder()
            .status(http::StatusCode::NOT_FOUND)
            .body("Not found.".into())
            .unwrap())
    }
}

impl AcmePlugin for StandaloneServer {
    fn setup<'fut, 'a: 'fut, 'b: 'fut, 'c: 'fut, 'd: 'fut>(
        &'a mut self,
        client: &'b mut AcmeClient,
        authorization: &'c Authorization,
        _domain: &'d AcmeDomain,
        _task: Arc<WorkerTask>,
    ) -> Pin<Box<dyn Future<Output = Result<&'c str, Error>> + Send + 'fut>> {
        use hyper::server::conn::AddrIncoming;
        use hyper::service::{make_service_fn, service_fn};

        Box::pin(async move {
            self.stop();

            let challenge = extract_challenge(authorization, "http-01")?;
            let token = challenge
                .token()
                .ok_or_else(|| format_err!("missing token in challenge"))?;
            let key_auth = Arc::new(client.key_authorization(&token)?);
            let path = Arc::new(format!("/.well-known/acme-challenge/{}", token));

            let service = make_service_fn(move |_| {
                let path = Arc::clone(&path);
                let key_auth = Arc::clone(&key_auth);
                async move {
                    Ok::<_, hyper::Error>(service_fn(move |request| {
                        standalone_respond(request, Arc::clone(&path), Arc::clone(&key_auth))
                    }))
                }
            });

            // `[::]:80` first, then `*:80`
            let incoming = AddrIncoming::bind(&(([0u16; 8], 80).into()))
                .or_else(|_| AddrIncoming::bind(&(([0u8; 4], 80).into())))?;

            let server = hyper::Server::builder(incoming).serve(service);

            let (future, abort) = futures::future::abortable(server);
            self.abort_handle = Some(abort);
            tokio::spawn(future);

            Ok(challenge.url.as_str())
        })
    }

    fn teardown<'fut, 'a: 'fut, 'b: 'fut, 'c: 'fut, 'd: 'fut>(
        &'a mut self,
        _client: &'b mut AcmeClient,
        _authorization: &'c Authorization,
        _domain: &'d AcmeDomain,
        _task: Arc<WorkerTask>,
    ) -> Pin<Box<dyn Future<Output = Result<(), Error>> + Send + 'fut>> {
        Box::pin(async move {
            if let Some(abort) = self.abort_handle.take() {
                abort.abort();
            }
            Ok(())
        })
    }
}