package node

import (
	"context"
	"encoding/json"
	"time"

	"oc-discovery/daemons/node/common"
	"oc-discovery/daemons/node/indexer"

	oclib "cloud.o-forge.io/core/oc-lib"
	"cloud.o-forge.io/core/oc-lib/dbs"
	"cloud.o-forge.io/core/oc-lib/models/peer"
	"github.com/libp2p/go-libp2p/core/control"
	"github.com/libp2p/go-libp2p/core/host"
	"github.com/libp2p/go-libp2p/core/network"
	pp "github.com/libp2p/go-libp2p/core/peer"
	ma "github.com/multiformats/go-multiaddr"
)

// OCConnectionGater enforces two rules on every inbound connection:
//  1. If the peer is known locally and blacklisted → reject.
//  2. If the peer is unknown locally → ask indexers one by one whether it
//     exists in the DHT.  Accept as soon as one confirms it; reject if none do
//     (or if no indexers are reachable yet, allow optimistically).
//
// Outbound connections are always allowed — we chose to dial them.
type OCConnectionGater struct {
	host host.Host
}

func newOCConnectionGater(h host.Host) *OCConnectionGater {
	return &OCConnectionGater{host: h}
}

// InterceptPeerDial — allow all outbound dials.
func (g *OCConnectionGater) InterceptPeerDial(_ pp.ID) bool { return true }

// InterceptAddrDial — allow all outbound dials.
func (g *OCConnectionGater) InterceptAddrDial(_ pp.ID, _ ma.Multiaddr) bool { return true }

// InterceptAccept — allow at transport level (PeerID not yet known).
func (g *OCConnectionGater) InterceptAccept(_ network.ConnMultiaddrs) bool { return true }

// InterceptUpgraded — final gate; always allow (decisions already made in InterceptSecured).
func (g *OCConnectionGater) InterceptUpgraded(_ network.Conn) (bool, control.DisconnectReason) {
	return true, 0
}

// InterceptSecured is called after the cryptographic handshake — PeerID is now known.
// Only inbound connections are verified; outbound are trusted.
func (g *OCConnectionGater) InterceptSecured(dir network.Direction, pid pp.ID, _ network.ConnMultiaddrs) bool {
	if dir == network.DirOutbound {
		return true
	}
	logger := oclib.GetLogger()

	// 1. Local DB lookup by PeerID.
	access := oclib.NewRequestAdmin(oclib.LibDataEnum(oclib.PEER), nil)
	results := access.Search(&dbs.Filters{
		And: map[string][]dbs.Filter{ // search by name if no filters are provided
			"peer_id": {{Operator: dbs.EQUAL.String(), Value: pid.String()}},
		},
	}, pid.String(), false)
	for _, item := range results.Data {
		p, ok := item.(*peer.Peer)
		if !ok || p.PeerID != pid.String() {
			continue
		}
		if p.Relation == peer.BLACKLIST {
			logger.Warn().Str("peer", pid.String()).Msg("[gater] rejected blacklisted peer")
			return false
		}
		// Known, not blacklisted.
		return true
	}

	// 2. Unknown locally — verify via indexers.
	indexers := common.Indexers.GetAddrs()

	if len(indexers) == 0 {
		// No indexers reachable yet — allow optimistically (bootstrap phase).
		logger.Warn().Str("peer", pid.String()).Msg("[gater] no indexers available, allowing unverified inbound")
		return true
	}

	req := indexer.GetValue{PeerID: pid.String()}
	// A single DHT GetValue already traverses the entire DHT network, so asking
	// a second indexer would yield the same result. We only fall through to the
	// next indexer if the current one is unreachable (transport error), not if
	// it returns found=false (that answer is already DHT-wide authoritative).
	for _, ai := range indexers {
		found, reachable := queryIndexerPeerExists(g.host, *ai.Info, req)
		if !reachable {
			continue // indexer down — try next
		}
		if !found {
			logger.Warn().Str("peer", pid.String()).Msg("[gater] peer not found in DHT, rejecting inbound")
		}
		return found // definitive DHT answer
	}

	// All indexers unreachable — allow optimistically rather than blocking indefinitely.
	logger.Warn().Str("peer", pid.String()).Msg("[gater] all indexers unreachable, allowing unverified inbound")
	return true
}

// queryIndexerPeerExists opens a fresh one-shot stream to ai, sends a GetValue
// request, and returns (found, reachable).
// reachable=false means the indexer could not be reached (transport error);
// the caller should then try another indexer.
// reachable=true means the indexer answered — found is the DHT-wide authoritative result.
func queryIndexerPeerExists(h host.Host, ai pp.AddrInfo, req indexer.GetValue) (found, reachable bool) {
	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
	defer cancel()

	if h.Network().Connectedness(ai.ID) != network.Connected {
		if err := h.Connect(ctx, ai); err != nil {
			return false, false
		}
	}
	s, err := h.NewStream(ctx, ai.ID, common.ProtocolGet)
	if err != nil {
		return false, false
	}
	defer s.Close()
	s.SetDeadline(time.Now().Add(3 * time.Second))

	if err := json.NewEncoder(s).Encode(req); err != nil {
		return false, false
	}
	var resp indexer.GetResponse
	if err := json.NewDecoder(s).Decode(&resp); err != nil {
		return false, false
	}
	return resp.Found, true
}