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// Copyright 2022 Protocol Labs.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

use crate::certificate;
use crate::certificate::P2pCertificate;
use futures::future::BoxFuture;
use futures::AsyncWrite;
use futures::{AsyncRead, FutureExt};
use futures_rustls::TlsStream;
use libp2p_core::{identity, InboundUpgrade, OutboundUpgrade, PeerId, UpgradeInfo};
use rustls::{CommonState, ServerName};
use std::net::{IpAddr, Ipv4Addr};
use std::sync::Arc;

#[derive(thiserror::Error, Debug)]
pub enum UpgradeError {
    #[error("Failed to generate certificate")]
    CertificateGeneration(#[from] certificate::GenError),
    #[error("Failed to upgrade server connection")]
    ServerUpgrade(std::io::Error),
    #[error("Failed to upgrade client connection")]
    ClientUpgrade(std::io::Error),
    #[error("Failed to parse certificate")]
    BadCertificate(#[from] certificate::ParseError),
}

#[derive(Clone)]
pub struct Config {
    server: rustls::ServerConfig,
    client: rustls::ClientConfig,
}

impl Config {
    pub fn new(identity: &identity::Keypair) -> Result<Self, certificate::GenError> {
        Ok(Self {
            server: crate::make_server_config(identity)?,
            client: crate::make_client_config(identity, None)?,
        })
    }
}

impl UpgradeInfo for Config {
    type Info = &'static [u8];
    type InfoIter = std::iter::Once<Self::Info>;

    fn protocol_info(&self) -> Self::InfoIter {
        std::iter::once(b"/tls/1.0.0")
    }
}

impl<C> InboundUpgrade<C> for Config
where
    C: AsyncRead + AsyncWrite + Send + Unpin + 'static,
{
    type Output = (PeerId, TlsStream<C>);
    type Error = UpgradeError;
    type Future = BoxFuture<'static, Result<Self::Output, Self::Error>>;

    fn upgrade_inbound(self, socket: C, _: Self::Info) -> Self::Future {
        async move {
            let stream = futures_rustls::TlsAcceptor::from(Arc::new(self.server))
                .accept(socket)
                .await
                .map_err(UpgradeError::ServerUpgrade)?;

            let peer_id = extract_single_certificate(stream.get_ref().1)?.peer_id();

            Ok((peer_id, stream.into()))
        }
        .boxed()
    }
}

impl<C> OutboundUpgrade<C> for Config
where
    C: AsyncRead + AsyncWrite + Send + Unpin + 'static,
{
    type Output = (PeerId, TlsStream<C>);
    type Error = UpgradeError;
    type Future = BoxFuture<'static, Result<Self::Output, Self::Error>>;

    fn upgrade_outbound(self, socket: C, _: Self::Info) -> Self::Future {
        async move {
            // Spec: In order to keep this flexibility for future versions, clients that only support the version of the handshake defined in this document MUST NOT send any value in the Server Name Indication.
            // Setting `ServerName` to unspecified will disable the use of the SNI extension.
            let name = ServerName::IpAddress(IpAddr::V4(Ipv4Addr::UNSPECIFIED));

            let stream = futures_rustls::TlsConnector::from(Arc::new(self.client))
                .connect(name, socket)
                .await
                .map_err(UpgradeError::ClientUpgrade)?;

            let peer_id = extract_single_certificate(stream.get_ref().1)?.peer_id();

            Ok((peer_id, stream.into()))
        }
        .boxed()
    }
}

fn extract_single_certificate(
    state: &CommonState,
) -> Result<P2pCertificate<'_>, certificate::ParseError> {
    let cert = match state
        .peer_certificates()
        .expect("config enforces presence of certificates")
    {
        [single] => single,
        _ => panic!("config enforces exactly one certificate"),
    };

    certificate::parse(cert)
}