// Copyright 2019 Parity Technologies (UK) Ltd.
//
// 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::behaviour::FromSwarm;
use crate::connection::ConnectionId;
use crate::handler::{
    AddressChange, ConnectionEvent, ConnectionHandler, ConnectionHandlerEvent, DialUpgradeError,
    FullyNegotiatedInbound, FullyNegotiatedOutbound, ListenUpgradeError, SubstreamProtocol,
};
use crate::upgrade::SendWrapper;
use crate::{
    ConnectionDenied, NetworkBehaviour, THandler, THandlerInEvent, THandlerOutEvent, ToSwarm,
};
use either::Either;
use futures::future;
use libp2p_core::{upgrade::DeniedUpgrade, Endpoint, Multiaddr};
use libp2p_identity::PeerId;
use std::{task::Context, task::Poll};

/// Implementation of `NetworkBehaviour` that can be either in the disabled or enabled state.
///
/// The state can only be chosen at initialization.
pub struct Toggle<TBehaviour> {
    inner: Option<TBehaviour>,
}

impl<TBehaviour> Toggle<TBehaviour> {
    /// Returns `true` if `Toggle` is enabled and `false` if it's disabled.
    pub fn is_enabled(&self) -> bool {
        self.inner.is_some()
    }

    /// Returns a reference to the inner `NetworkBehaviour`.
    pub fn as_ref(&self) -> Option<&TBehaviour> {
        self.inner.as_ref()
    }

    /// Returns a mutable reference to the inner `NetworkBehaviour`.
    pub fn as_mut(&mut self) -> Option<&mut TBehaviour> {
        self.inner.as_mut()
    }
}

impl<TBehaviour> From<Option<TBehaviour>> for Toggle<TBehaviour> {
    fn from(inner: Option<TBehaviour>) -> Self {
        Toggle { inner }
    }
}

impl<TBehaviour> NetworkBehaviour for Toggle<TBehaviour>
where
    TBehaviour: NetworkBehaviour,
{
    type ConnectionHandler = ToggleConnectionHandler<THandler<TBehaviour>>;
    type ToSwarm = TBehaviour::ToSwarm;

    fn handle_pending_inbound_connection(
        &mut self,
        connection_id: ConnectionId,
        local_addr: &Multiaddr,
        remote_addr: &Multiaddr,
    ) -> Result<(), ConnectionDenied> {
        let inner = match self.inner.as_mut() {
            None => return Ok(()),
            Some(inner) => inner,
        };

        inner.handle_pending_inbound_connection(connection_id, local_addr, remote_addr)?;

        Ok(())
    }

    fn handle_established_inbound_connection(
        &mut self,
        connection_id: ConnectionId,
        peer: PeerId,
        local_addr: &Multiaddr,
        remote_addr: &Multiaddr,
    ) -> Result<THandler<Self>, ConnectionDenied> {
        let inner = match self.inner.as_mut() {
            None => return Ok(ToggleConnectionHandler { inner: None }),
            Some(inner) => inner,
        };

        let handler = inner.handle_established_inbound_connection(
            connection_id,
            peer,
            local_addr,
            remote_addr,
        )?;

        Ok(ToggleConnectionHandler {
            inner: Some(handler),
        })
    }

    fn handle_pending_outbound_connection(
        &mut self,
        connection_id: ConnectionId,
        maybe_peer: Option<PeerId>,
        addresses: &[Multiaddr],
        effective_role: Endpoint,
    ) -> Result<Vec<Multiaddr>, ConnectionDenied> {
        let inner = match self.inner.as_mut() {
            None => return Ok(vec![]),
            Some(inner) => inner,
        };

        let addresses = inner.handle_pending_outbound_connection(
            connection_id,
            maybe_peer,
            addresses,
            effective_role,
        )?;

        Ok(addresses)
    }

    fn handle_established_outbound_connection(
        &mut self,
        connection_id: ConnectionId,
        peer: PeerId,
        addr: &Multiaddr,
        role_override: Endpoint,
    ) -> Result<THandler<Self>, ConnectionDenied> {
        let inner = match self.inner.as_mut() {
            None => return Ok(ToggleConnectionHandler { inner: None }),
            Some(inner) => inner,
        };

        let handler = inner.handle_established_outbound_connection(
            connection_id,
            peer,
            addr,
            role_override,
        )?;

        Ok(ToggleConnectionHandler {
            inner: Some(handler),
        })
    }

    fn on_swarm_event(&mut self, event: FromSwarm) {
        if let Some(behaviour) = &mut self.inner {
            behaviour.on_swarm_event(event);
        }
    }

    fn on_connection_handler_event(
        &mut self,
        peer_id: PeerId,
        connection_id: ConnectionId,
        event: THandlerOutEvent<Self>,
    ) {
        if let Some(behaviour) = &mut self.inner {
            behaviour.on_connection_handler_event(peer_id, connection_id, event)
        }
    }

    fn poll(
        &mut self,
        cx: &mut Context<'_>,
    ) -> Poll<ToSwarm<Self::ToSwarm, THandlerInEvent<Self>>> {
        if let Some(inner) = self.inner.as_mut() {
            inner.poll(cx)
        } else {
            Poll::Pending
        }
    }
}

/// Implementation of [`ConnectionHandler`] that can be in the disabled state.
pub struct ToggleConnectionHandler<TInner> {
    inner: Option<TInner>,
}

impl<TInner> ToggleConnectionHandler<TInner>
where
    TInner: ConnectionHandler,
{
    fn on_fully_negotiated_inbound(
        &mut self,
        FullyNegotiatedInbound {
            protocol: out,
            info,
        }: FullyNegotiatedInbound<
            <Self as ConnectionHandler>::InboundProtocol,
            <Self as ConnectionHandler>::InboundOpenInfo,
        >,
    ) {
        let out = match out {
            future::Either::Left(out) => out,
            future::Either::Right(v) => void::unreachable(v),
        };

        if let Either::Left(info) = info {
            self.inner
                .as_mut()
                .expect("Can't receive an inbound substream if disabled; QED")
                .on_connection_event(ConnectionEvent::FullyNegotiatedInbound(
                    FullyNegotiatedInbound {
                        protocol: out,
                        info,
                    },
                ));
        } else {
            panic!("Unexpected Either::Right in enabled `on_fully_negotiated_inbound`.")
        }
    }

    fn on_listen_upgrade_error(
        &mut self,
        ListenUpgradeError { info, error: err }: ListenUpgradeError<
            <Self as ConnectionHandler>::InboundOpenInfo,
            <Self as ConnectionHandler>::InboundProtocol,
        >,
    ) {
        let (inner, info) = match (self.inner.as_mut(), info) {
            (Some(inner), Either::Left(info)) => (inner, info),
            // Ignore listen upgrade errors in disabled state.
            (None, Either::Right(())) => return,
            (Some(_), Either::Right(())) => panic!(
                "Unexpected `Either::Right` inbound info through \
                 `on_listen_upgrade_error` in enabled state.",
            ),
            (None, Either::Left(_)) => panic!(
                "Unexpected `Either::Left` inbound info through \
                 `on_listen_upgrade_error` in disabled state.",
            ),
        };

        let err = match err {
            Either::Left(e) => e,
            Either::Right(v) => void::unreachable(v),
        };

        inner.on_connection_event(ConnectionEvent::ListenUpgradeError(ListenUpgradeError {
            info,
            error: err,
        }));
    }
}

impl<TInner> ConnectionHandler for ToggleConnectionHandler<TInner>
where
    TInner: ConnectionHandler,
{
    type FromBehaviour = TInner::FromBehaviour;
    type ToBehaviour = TInner::ToBehaviour;
    type InboundProtocol = Either<SendWrapper<TInner::InboundProtocol>, SendWrapper<DeniedUpgrade>>;
    type OutboundProtocol = TInner::OutboundProtocol;
    type OutboundOpenInfo = TInner::OutboundOpenInfo;
    type InboundOpenInfo = Either<TInner::InboundOpenInfo, ()>;

    fn listen_protocol(&self) -> SubstreamProtocol<Self::InboundProtocol, Self::InboundOpenInfo> {
        if let Some(inner) = self.inner.as_ref() {
            inner
                .listen_protocol()
                .map_upgrade(|u| Either::Left(SendWrapper(u)))
                .map_info(Either::Left)
        } else {
            SubstreamProtocol::new(Either::Right(SendWrapper(DeniedUpgrade)), Either::Right(()))
        }
    }

    fn on_behaviour_event(&mut self, event: Self::FromBehaviour) {
        self.inner
            .as_mut()
            .expect("Can't receive events if disabled; QED")
            .on_behaviour_event(event)
    }

    fn connection_keep_alive(&self) -> bool {
        self.inner
            .as_ref()
            .map(|h| h.connection_keep_alive())
            .unwrap_or(false)
    }

    fn poll(
        &mut self,
        cx: &mut Context<'_>,
    ) -> Poll<
        ConnectionHandlerEvent<Self::OutboundProtocol, Self::OutboundOpenInfo, Self::ToBehaviour>,
    > {
        if let Some(inner) = self.inner.as_mut() {
            inner.poll(cx)
        } else {
            Poll::Pending
        }
    }

    fn on_connection_event(
        &mut self,
        event: ConnectionEvent<
            Self::InboundProtocol,
            Self::OutboundProtocol,
            Self::InboundOpenInfo,
            Self::OutboundOpenInfo,
        >,
    ) {
        match event {
            ConnectionEvent::FullyNegotiatedInbound(fully_negotiated_inbound) => {
                self.on_fully_negotiated_inbound(fully_negotiated_inbound)
            }
            ConnectionEvent::FullyNegotiatedOutbound(FullyNegotiatedOutbound {
                protocol: out,
                info,
            }) => self
                .inner
                .as_mut()
                .expect("Can't receive an outbound substream if disabled; QED")
                .on_connection_event(ConnectionEvent::FullyNegotiatedOutbound(
                    FullyNegotiatedOutbound {
                        protocol: out,
                        info,
                    },
                )),
            ConnectionEvent::AddressChange(address_change) => {
                if let Some(inner) = self.inner.as_mut() {
                    inner.on_connection_event(ConnectionEvent::AddressChange(AddressChange {
                        new_address: address_change.new_address,
                    }));
                }
            }
            ConnectionEvent::DialUpgradeError(DialUpgradeError { info, error: err }) => self
                .inner
                .as_mut()
                .expect("Can't receive an outbound substream if disabled; QED")
                .on_connection_event(ConnectionEvent::DialUpgradeError(DialUpgradeError {
                    info,
                    error: err,
                })),
            ConnectionEvent::ListenUpgradeError(listen_upgrade_error) => {
                self.on_listen_upgrade_error(listen_upgrade_error)
            }
            ConnectionEvent::LocalProtocolsChange(change) => {
                if let Some(inner) = self.inner.as_mut() {
                    inner.on_connection_event(ConnectionEvent::LocalProtocolsChange(change));
                }
            }
            ConnectionEvent::RemoteProtocolsChange(change) => {
                if let Some(inner) = self.inner.as_mut() {
                    inner.on_connection_event(ConnectionEvent::RemoteProtocolsChange(change));
                }
            }
        }
    }

    fn poll_close(&mut self, cx: &mut Context<'_>) -> Poll<Option<Self::ToBehaviour>> {
        let Some(inner) = self.inner.as_mut() else {
            return Poll::Ready(None);
        };

        inner.poll_close(cx)
    }
}