/*
   Copyright 2022 Erigon-Lightclient contributors
   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at
       http://www.apache.org/licenses/LICENSE-2.0
   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

package sentinel

import (
	"context"
	"time"

	"github.com/ledgerwatch/erigon/cmd/lightclient/clparams"
	"github.com/ledgerwatch/erigon/p2p/enr"
	"github.com/ledgerwatch/log/v3"
	"github.com/libp2p/go-libp2p-core/peer"
	"github.com/multiformats/go-multiaddr"
	"github.com/pkg/errors"
)

func (s *Sentinel) connectWithPeer(ctx context.Context, info peer.AddrInfo) error {
	if info.ID == s.host.ID() {
		return nil
	}
	if s.peers.IsBadPeer(info.ID) {
		return errors.New("refused to connect to bad peer")
	}
	ctxWithTimeout, cancel := context.WithTimeout(ctx, clparams.MaxDialTimeout)
	defer cancel()
	if err := s.host.Connect(ctxWithTimeout, info); err != nil {
		s.peers.Penalize(info.ID)
		return err
	}
	return nil
}

func (s *Sentinel) connectWithAllPeers(multiAddrs []multiaddr.Multiaddr) error {
	addrInfos, err := peer.AddrInfosFromP2pAddrs(multiAddrs...)
	if err != nil {
		return err
	}
	for _, peerInfo := range addrInfos {
		// make each dial non-blocking
		go func(peerInfo peer.AddrInfo) {
			if err := s.connectWithPeer(s.ctx, peerInfo); err != nil {
				log.Debug("Could not connect with peer", "err", err)
			}
		}(peerInfo)
	}
	return nil
}

// listen for new nodes watches for new nodes in the network and adds them to the peerstore.
func (s *Sentinel) listenForPeers() {
	iterator := s.listener.RandomNodes()
	defer iterator.Close()
	for {
		// Exit if service's context is canceled
		if s.ctx.Err() != nil {
			break
		}
		if s.HasTooManyPeers() {
			// Pause the main loop for a period to stop looking
			// for new peers.
			log.Trace("Not looking for peers, at peer limit")
			time.Sleep(100 * time.Millisecond)
			continue
		}
		exists := iterator.Next()
		if !exists {
			break
		}
		node := iterator.Node()
		peerInfo, _, err := convertToAddrInfo(node)
		if err != nil {
			log.Error("Could not convert to peer info", "err", err)
			continue
		}

		// Make sure that peer is not dialed too often, for each connection attempt there's a backoff period.
		go func(peerInfo *peer.AddrInfo) {
			if err := s.connectWithPeer(s.ctx, *peerInfo); err != nil {
				log.Debug("Could not connect with peer", "err", err)
			}
		}(peerInfo)
	}
}

func (s *Sentinel) connectToBootnodes() error {
	for i := range s.cfg.DiscoverConfig.Bootnodes {
		// do not dial bootnodes with their tcp ports not set
		if err := s.cfg.DiscoverConfig.Bootnodes[i].Record().Load(enr.WithEntry("tcp", new(enr.TCP))); err != nil {
			if !enr.IsNotFound(err) {
				log.Error("Could not retrieve tcp port")
			}
			continue
		}
	}
	multiAddresses := convertToMultiAddr(s.cfg.DiscoverConfig.Bootnodes)
	s.connectWithAllPeers(multiAddresses)
	return nil
}