#[macro_use] extern crate log;

use std::{panic::AssertUnwindSafe, convert::TryFrom, io::BufReader, sync::Arc, path::PathBuf};
use futures::{future::BoxFuture, FutureExt};
use tokio::{
    prelude::*,
    io::{self, BufStream},
    net::{TcpStream, ToSocketAddrs},
};
use tokio::net::TcpListener;
use rustls::ClientCertVerifier;
use tokio_rustls::{rustls, TlsAcceptor};
use rustls::*;
use anyhow::*;
use uri::URIReference;
use lazy_static::lazy_static;

pub mod types;
pub mod util;
#[cfg(feature = "user_management")]
pub mod user_management;

#[cfg(feature="user_management")]
use user_management::UserManager;

pub use mime;
pub use uriparse as uri;
pub use types::*;

pub const REQUEST_URI_MAX_LEN: usize = 1024;
pub const GEMINI_PORT: u16 = 1965;

type Handler = Arc<dyn Fn(Request) -> HandlerResponse + Send + Sync>;
type HandlerResponse = BoxFuture<'static, Result<Response>>;

#[derive(Clone)]
pub struct Server {
    tls_acceptor: TlsAcceptor,
    listener: Arc<TcpListener>,
    handler: Handler,
    #[cfg(feature="user_management")]
    manager: UserManager,
}

impl Server {
    pub fn bind<A: ToSocketAddrs>(addr: A) -> Builder<A> {
        Builder::bind(addr)
    }

    async fn serve(self) -> Result<()> {
        loop {
            let (stream, _addr) = self.listener.accept().await
                .context("Failed to accept client")?;
            let this = self.clone();

            tokio::spawn(async move {
                if let Err(err) = this.serve_client(stream).await {
                    error!("{:?}", err);
                }
            });
        }
    }

    async fn serve_client(self, stream: TcpStream) -> Result<()> {
        let stream = self.tls_acceptor.accept(stream).await
            .context("Failed to establish TLS session")?;
        let mut stream = BufStream::new(stream);

        #[cfg(feature="user_management")]
        let mut request = self.receive_request(&mut stream).await
            .context("Failed to receive request")?;
        #[cfg(not(feature="user_management"))]
        let mut request = Self::receive_request(&mut stream).await
            .context("Failed to receive request")?;

        debug!("Client requested: {}", request.uri());

        // Identify the client certificate from the tls stream.  This is the first
        // certificate in the certificate chain.
        let client_cert = stream.get_ref()
            .get_ref()
            .1
            .get_peer_certificates()
            .and_then(|mut v| if v.is_empty() {None} else {Some(v.remove(0))});

        request.set_cert(client_cert);

        let handler = (self.handler)(request);
        let handler = AssertUnwindSafe(handler);

        let response = handler.catch_unwind().await
            .unwrap_or_else(|_| Response::server_error(""))
            .or_else(|err| {
                error!("Handler failed: {:?}", err);
                Response::server_error("")
            })
            .context("Request handler failed")?;

        send_response(response, &mut stream).await
            .context("Failed to send response")?;

        stream.flush().await
            .context("Failed to flush response data")?;

        Ok(())
    }

    async fn receive_request(
        #[cfg(feature="user_management")]
        &self,
        stream: &mut (impl AsyncBufRead + Unpin)
    ) -> Result<Request> {
        let limit = REQUEST_URI_MAX_LEN + "\r\n".len();
        let mut stream = stream.take(limit as u64);
        let mut uri = Vec::new();

        stream.read_until(b'\n', &mut uri).await?;

        if !uri.ends_with(b"\r\n") {
            if uri.len() < REQUEST_URI_MAX_LEN {
                bail!("Request header not terminated with CRLF")
            } else {
                bail!("Request URI too long")
            }
        }

        // Strip CRLF
        uri.pop();
        uri.pop();

        let uri = URIReference::try_from(&*uri)
            .context("Request URI is invalid")?
            .into_owned();
        let request = Request::from_uri(
            uri,
            #[cfg(feature="user_management")]
            self.manager.clone(),
        ) .context("Failed to create request from URI")?;

        Ok(request)
    }
}

pub struct Builder<A> {
    addr: A,
    #[cfg(feature="user_management")]
    data_dir: PathBuf,
}

impl<A: ToSocketAddrs> Builder<A> {
    fn bind(addr: A) -> Self {
        Self {
            addr,
            #[cfg(feature="user_management")]
            data_dir: "data".into(),
        }
    }

    #[cfg(feature="user_management")]
    /// Sets the directory to store user data in
    ///
    /// Defaults to `./data` if not specified
    pub fn set_database_dir(mut self, path: impl Into<PathBuf>) -> Self {
        self.data_dir = path.into();
        self
    }

    pub async fn serve<F>(self, handler: F) -> Result<()>
    where
        F: Fn(Request) -> HandlerResponse + Send + Sync + 'static,
    {
        let config = tls_config()
            .context("Failed to create TLS config")?;

        let listener = TcpListener::bind(self.addr).await
            .context("Failed to create socket")?;

        let server = Server {
            tls_acceptor: TlsAcceptor::from(config),
            listener: Arc::new(listener),
            handler: Arc::new(handler),
            #[cfg(feature="user_management")]
            manager: UserManager::new(self.data_dir)?,
        };

        server.serve().await
    }
}

async fn send_response(mut response: Response, stream: &mut (impl AsyncWrite + Unpin)) -> Result<()> {
    send_response_header(response.header(), stream).await
        .context("Failed to send response header")?;

    if let Some(body) = response.take_body() {
        send_response_body(body, stream).await
            .context("Failed to send response body")?;
    }

    Ok(())
}

async fn send_response_header(header: &ResponseHeader, stream: &mut (impl AsyncWrite + Unpin)) -> Result<()> {
    let header = format!(
        "{status} {meta}\r\n",
        status = header.status.code(),
        meta = header.meta.as_str(),
    );

    stream.write_all(header.as_bytes()).await?;

    Ok(())
}

async fn send_response_body(body: Body, stream: &mut (impl AsyncWrite + Unpin)) -> Result<()> {
    match body {
        Body::Bytes(bytes) => stream.write_all(&bytes).await?,
        Body::Reader(mut reader) => { io::copy(&mut reader, stream).await?; },
    }

    Ok(())
}

fn tls_config() -> Result<Arc<ServerConfig>> {
    let mut config = ServerConfig::new(AllowAnonOrSelfsignedClient::new());

    let cert_chain = load_cert_chain()
        .context("Failed to load TLS certificate")?;
    let key = load_key()
        .context("Failed to load TLS key")?;
    config.set_single_cert(cert_chain, key)
        .context("Failed to use loaded TLS certificate")?;

    Ok(config.into())
}

fn load_cert_chain() -> Result<Vec<Certificate>> {
    let cert_path = "cert/cert.pem";
    let certs = std::fs::File::open(cert_path)
        .with_context(|| format!("Failed to open `{}`", cert_path))?;
    let mut certs = BufReader::new(certs);
    let certs = rustls::internal::pemfile::certs(&mut certs)
        .map_err(|_| anyhow!("failed to load certs `{}`", cert_path))?;

    Ok(certs)
}

fn load_key() -> Result<PrivateKey> {
    let key_path = "cert/key.pem";
    let keys = std::fs::File::open(key_path)
        .with_context(|| format!("Failed to open `{}`", key_path))?;
    let mut keys = BufReader::new(keys);
    let mut keys = rustls::internal::pemfile::pkcs8_private_keys(&mut keys)
        .map_err(|_| anyhow!("failed to load key `{}`", key_path))?;

    ensure!(!keys.is_empty(), "no key found");

    let key = keys.swap_remove(0);

    Ok(key)
}

/// Mime for Gemini documents
pub const GEMINI_MIME_STR: &str = "text/gemini";

lazy_static! {
    /// Mime for Gemini documents ("text/gemini")
    pub static ref GEMINI_MIME: Mime = GEMINI_MIME_STR.parse().expect("northstar BUG");
}

#[deprecated(note = "Use `GEMINI_MIME` instead", since = "0.3.0")]
pub fn gemini_mime() -> Result<Mime> {
    Ok(GEMINI_MIME.clone())
}

/// A client cert verifier that accepts all connections
///
/// Unfortunately, rustls doesn't provide a ClientCertVerifier that accepts self-signed
/// certificates, so we need to implement this ourselves.
struct AllowAnonOrSelfsignedClient { }
impl AllowAnonOrSelfsignedClient {

    /// Create a new verifier
    fn new() -> Arc<Self> {
        Arc::new(Self {})
    }

}

impl ClientCertVerifier for AllowAnonOrSelfsignedClient {

    fn client_auth_root_subjects(
        &self,
        _: Option<&webpki::DNSName>
    ) -> Option<DistinguishedNames> {
        Some(Vec::new())
    }

    fn client_auth_mandatory(&self, _sni: Option<&webpki::DNSName>) -> Option<bool> {
        Some(false)
    }

    fn verify_client_cert(
        &self,
        _: &[Certificate],
        _: Option<&webpki::DNSName>
    ) -> Result<ClientCertVerified, TLSError> {
        Ok(ClientCertVerified::assertion())
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn gemini_mime_parses() {
        let _: &Mime = &GEMINI_MIME;
    }
}