//! `--libp2p-ignore`: address ranges neither published nor dialled, nor connected over
//! (`Ignoring`, a behaviour that denies connections there), nor told peers by identify
//! (`Identifying`).

use std::fmt;

use super::*;

/// An address range (`10.244.0.0/16`, `42::/16`; a bare address is a range of one), for
/// `Libp2pConfig::ignore`.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub(crate) struct IpRange {
    pub(super) network: std::net::IpAddr,
    pub(super) prefix: u8,
}

impl FromStr for IpRange {
    type Err = anyhow::Error;

    fn from_str(text: &str) -> Result<Self> {
        let (address, prefix) = match text.split_once('/') {
            Some((address, prefix)) => (address, Some(prefix)),
            None => (text, None),
        };
        let network: std::net::IpAddr = address
            .parse()
            .with_context(|| format!("{text:?} is no address range (e.g. 10.244.0.0/16)"))?;
        let bits = if network.is_ipv4() { 32 } else { 128 };
        let prefix = match prefix {
            Some(prefix) => prefix
                .parse::<u8>()
                .ok()
                .filter(|prefix| *prefix <= bits)
                .with_context(|| format!("{text:?}: the prefix is 0 to {bits}"))?,
            None => bits,
        };
        Ok(Self { network, prefix })
    }
}

impl fmt::Display for IpRange {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}/{}", self.network, self.prefix)
    }
}

impl IpRange {
    /// The range of the `prefix` bits of `ip` (the rest zero).
    pub(super) fn masked(ip: std::net::IpAddr, prefix: u8) -> Self {
        use std::net::IpAddr;
        let network = match ip {
            IpAddr::V4(ip) => {
                let mask = u32::MAX.checked_shl(32 - u32::from(prefix)).unwrap_or(0);
                IpAddr::V4((u32::from(ip) & mask).into())
            }
            IpAddr::V6(ip) => {
                let mask = u128::MAX.checked_shl(128 - u32::from(prefix)).unwrap_or(0);
                IpAddr::V6((u128::from(ip) & mask).into())
            }
        };
        Self { network, prefix }
    }

    /// Whether every address of `other` is in this range too.
    pub(super) fn covers(&self, other: &IpRange) -> bool {
        self.network.is_ipv4() == other.network.is_ipv4()
            && self.prefix <= other.prefix
            && self.contains(other.network)
    }

    pub(super) fn contains(&self, ip: std::net::IpAddr) -> bool {
        use std::net::IpAddr;
        match (self.network, ip) {
            (IpAddr::V4(network), IpAddr::V4(ip)) => {
                let mask = u32::MAX
                    .checked_shl(32 - u32::from(self.prefix))
                    .unwrap_or(0);
                u32::from(network) & mask == u32::from(ip) & mask
            }
            (IpAddr::V6(network), IpAddr::V6(ip)) => {
                let mask = u128::MAX
                    .checked_shl(128 - u32::from(self.prefix))
                    .unwrap_or(0);
                u128::from(network) & mask == u128::from(ip) & mask
            }
            _ => false,
        }
    }
}

/// Whether `address` is in one of `ranges`: a direct address there (one through a relay
/// is judged by the connection to the relay).
pub(super) fn ignored(ranges: &[IpRange], address: &Multiaddr) -> bool {
    if ranges.is_empty() || is_relayed(address) {
        return false;
    }
    let ip = match address.iter().next() {
        Some(Protocol::Ip4(ip)) => std::net::IpAddr::V4(ip),
        Some(Protocol::Ip6(ip)) => std::net::IpAddr::V6(ip),
        _ => return false,
    };
    ranges.iter().any(|range| range.contains(ip))
}

/// Whether `address` can only be reached over a range of `ranges`: a direct address
/// there, or one through a relay whose own address is there (dialling the relay is
/// refused, `Ignoring`). For what's kept and dialled; connections are judged by
/// `ignored`.
pub(super) fn left_out(ranges: &[IpRange], address: &Multiaddr) -> bool {
    if !is_relayed(address) {
        return ignored(ranges, address);
    }
    let relay: Multiaddr = address
        .iter()
        .take_while(|protocol| !matches!(protocol, Protocol::P2pCircuit))
        .collect();
    ignored(ranges, &without_peer(relay))
}

/// Keeps connections off the address ranges `libp2p-ignore` names, whoever dialled:
/// hole punching and identify bring addresses there too, and a peer may dial us there.
pub(super) struct Ignoring {
    pub(super) ranges: Vec<IpRange>,
}

#[derive(Debug, thiserror::Error)]
#[error("{0} is in a range left out (libp2p-ignore)")]
pub(super) struct IgnoredAddress(Multiaddr);

impl ::libp2p::swarm::NetworkBehaviour for Ignoring {
    type ConnectionHandler = ::libp2p::swarm::dummy::ConnectionHandler;
    type ToSwarm = std::convert::Infallible;

    fn handle_pending_inbound_connection(
        &mut self,
        _connection_id: ConnectionId,
        _local_addr: &Multiaddr,
        remote_addr: &Multiaddr,
    ) -> Result<(), ::libp2p::swarm::ConnectionDenied> {
        if ignored(&self.ranges, remote_addr) {
            return Err(::libp2p::swarm::ConnectionDenied::new(IgnoredAddress(
                remote_addr.clone(),
            )));
        }
        Ok(())
    }

    fn handle_established_inbound_connection(
        &mut self,
        _connection_id: ConnectionId,
        _peer: PeerId,
        _local_addr: &Multiaddr,
        _remote_addr: &Multiaddr,
    ) -> Result<::libp2p::swarm::THandler<Self>, ::libp2p::swarm::ConnectionDenied> {
        Ok(::libp2p::swarm::dummy::ConnectionHandler)
    }

    /// Dials libp2p makes itself (hole punching, AutoNAT, the DHT) to addresses all in
    /// ranges left out are refused before they go out; ours never go there
    /// (`Book::usable`). A dial with an address elsewhere too goes, and a connection it
    /// makes in a range left out is refused once established (below).
    fn handle_pending_outbound_connection(
        &mut self,
        _connection_id: ConnectionId,
        _maybe_peer: Option<PeerId>,
        addresses: &[Multiaddr],
        _effective_role: ::libp2p::core::Endpoint,
    ) -> Result<Vec<Multiaddr>, ::libp2p::swarm::ConnectionDenied> {
        if let Some(first) = addresses.first()
            && addresses
                .iter()
                .all(|address| ignored(&self.ranges, address))
        {
            return Err(::libp2p::swarm::ConnectionDenied::new(IgnoredAddress(
                first.clone(),
            )));
        }
        Ok(Vec::new())
    }

    fn handle_established_outbound_connection(
        &mut self,
        _connection_id: ConnectionId,
        _peer: PeerId,
        addr: &Multiaddr,
        _role_override: ::libp2p::core::Endpoint,
        _port_use: ::libp2p::core::transport::PortUse,
    ) -> Result<::libp2p::swarm::THandler<Self>, ::libp2p::swarm::ConnectionDenied> {
        if ignored(&self.ranges, addr) {
            return Err(::libp2p::swarm::ConnectionDenied::new(IgnoredAddress(
                addr.clone(),
            )));
        }
        Ok(::libp2p::swarm::dummy::ConnectionHandler)
    }

    fn on_swarm_event(&mut self, _event: ::libp2p::swarm::FromSwarm) {}

    fn on_connection_handler_event(
        &mut self,
        _peer_id: PeerId,
        _connection_id: ConnectionId,
        event: ::libp2p::swarm::THandlerOutEvent<Self>,
    ) {
        match event {}
    }

    fn poll(
        &mut self,
        _cx: &mut std::task::Context<'_>,
    ) -> std::task::Poll<
        ::libp2p::swarm::ToSwarm<Self::ToSwarm, ::libp2p::swarm::THandlerInEvent<Self>>,
    > {
        std::task::Poll::Pending
    }
}

/// libp2p's identify, not told our listen addresses, nor external ones (found by UPnP,
/// AutoNAT, a relay), in the ranges `libp2p-ignore` names: peers would remember them,
/// show them, and dial them in vain. Announced addresses (`--libp2p-announce`) are told
/// whatever range they are in.
pub(super) struct Identifying {
    pub(super) inner: ::libp2p::identify::Behaviour,
    pub(super) ranges: Vec<IpRange>,
    pub(super) announced: Vec<Multiaddr>,
}

impl Identifying {
    /// An external address identify isn't told: in an ignored range, and not announced.
    fn left_out(&self, address: &Multiaddr) -> bool {
        ignored(&self.ranges, address) && !self.announced.contains(address)
    }
}

impl ::libp2p::swarm::NetworkBehaviour for Identifying {
    type ConnectionHandler =
        <::libp2p::identify::Behaviour as ::libp2p::swarm::NetworkBehaviour>::ConnectionHandler;
    type ToSwarm = ::libp2p::identify::Event;

    fn handle_pending_inbound_connection(
        &mut self,
        connection_id: ConnectionId,
        local_addr: &Multiaddr,
        remote_addr: &Multiaddr,
    ) -> Result<(), ::libp2p::swarm::ConnectionDenied> {
        self.inner
            .handle_pending_inbound_connection(connection_id, local_addr, remote_addr)
    }

    fn handle_established_inbound_connection(
        &mut self,
        connection_id: ConnectionId,
        peer: PeerId,
        local_addr: &Multiaddr,
        remote_addr: &Multiaddr,
    ) -> Result<::libp2p::swarm::THandler<Self>, ::libp2p::swarm::ConnectionDenied> {
        self.inner.handle_established_inbound_connection(
            connection_id,
            peer,
            local_addr,
            remote_addr,
        )
    }

    fn handle_pending_outbound_connection(
        &mut self,
        connection_id: ConnectionId,
        maybe_peer: Option<PeerId>,
        addresses: &[Multiaddr],
        effective_role: ::libp2p::core::Endpoint,
    ) -> Result<Vec<Multiaddr>, ::libp2p::swarm::ConnectionDenied> {
        self.inner.handle_pending_outbound_connection(
            connection_id,
            maybe_peer,
            addresses,
            effective_role,
        )
    }

    fn handle_established_outbound_connection(
        &mut self,
        connection_id: ConnectionId,
        peer: PeerId,
        addr: &Multiaddr,
        role_override: ::libp2p::core::Endpoint,
        port_use: ::libp2p::core::transport::PortUse,
    ) -> Result<::libp2p::swarm::THandler<Self>, ::libp2p::swarm::ConnectionDenied> {
        self.inner.handle_established_outbound_connection(
            connection_id,
            peer,
            addr,
            role_override,
            port_use,
        )
    }

    fn on_swarm_event(&mut self, event: ::libp2p::swarm::FromSwarm) {
        use ::libp2p::swarm::FromSwarm;
        match event {
            FromSwarm::NewListenAddr(new) if ignored(&self.ranges, new.addr) => {}
            FromSwarm::ExpiredListenAddr(expired) if ignored(&self.ranges, expired.addr) => {}
            FromSwarm::ExternalAddrConfirmed(confirmed) if self.left_out(confirmed.addr) => {}
            FromSwarm::ExternalAddrExpired(expired) if self.left_out(expired.addr) => {}
            _ => self.inner.on_swarm_event(event),
        }
    }

    fn on_connection_handler_event(
        &mut self,
        peer_id: PeerId,
        connection_id: ConnectionId,
        event: ::libp2p::swarm::THandlerOutEvent<Self>,
    ) {
        self.inner
            .on_connection_handler_event(peer_id, connection_id, event)
    }

    fn poll(
        &mut self,
        cx: &mut std::task::Context<'_>,
    ) -> std::task::Poll<
        ::libp2p::swarm::ToSwarm<Self::ToSwarm, ::libp2p::swarm::THandlerInEvent<Self>>,
    > {
        self.inner.poll(cx)
    }
}