package indexer

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

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

	oclib "cloud.o-forge.io/core/oc-lib"
	pp "github.com/libp2p/go-libp2p/core/peer"
	"github.com/libp2p/go-libp2p/core/network"
)

const TopicSearchPeer = "oc-search-peer"

// searchTimeout returns the configured search timeout, defaulting to 5s.
func searchTimeout() time.Duration {
	if t := conf.GetConfig().SearchTimeout; t > 0 {
		return time.Duration(t) * time.Second
	}
	return 5 * time.Second
}

// initSearchHandlers registers ProtocolSearchPeer and ProtocolSearchPeerResponse
// and subscribes to TopicSearchPeer on GossipSub.
func (ix *IndexerService) initSearchHandlers() {
	ix.Host.SetStreamHandler(common.ProtocolSearchPeer, ix.handleSearchPeer)
	ix.Host.SetStreamHandler(common.ProtocolSearchPeerResponse, ix.handleSearchPeerResponse)
	ix.initSearchSubscription()
}

// updateReferent is called from HandleHeartbeat when Referent flag changes.
// If referent=true the node is added to referencedNodes; if false it is removed.
func (ix *IndexerService) updateReferent(pid pp.ID, rec PeerRecord, referent bool) {
	ix.referencedNodesMu.Lock()
	defer ix.referencedNodesMu.Unlock()
	if referent {
		ix.referencedNodes[pid] = rec
	} else {
		delete(ix.referencedNodes, pid)
	}
}

// searchReferenced looks up nodes in referencedNodes matching the query.
// Matches on peerID (exact), DID (exact), or name (case-insensitive contains).
func (ix *IndexerService) searchReferenced(peerID, did, name string) []common.SearchHit {
	ix.referencedNodesMu.RLock()
	defer ix.referencedNodesMu.RUnlock()
	nameLow := strings.ToLower(name)
	var hits []common.SearchHit
	for pid, rec := range ix.referencedNodes {
		pidStr := pid.String()
		matchPeerID := peerID != "" && pidStr == peerID
		matchDID := did != "" && rec.DID == did
		matchName := name != "" && strings.Contains(strings.ToLower(rec.Name), nameLow)
		if matchPeerID || matchDID || matchName {
			hits = append(hits, common.SearchHit{
				PeerID: pidStr,
				DID:    rec.DID,
				Name:   rec.Name,
			})
		}
	}
	return hits
}

// handleSearchPeer is the ProtocolSearchPeer handler.
// The node opens this stream, sends a SearchPeerRequest, and reads results
// as they stream in. The stream stays open until timeout or node closes it.
func (ix *IndexerService) handleSearchPeer(s network.Stream) {
	logger := oclib.GetLogger()
	defer s.Reset()

	var req common.SearchPeerRequest
	if err := json.NewDecoder(s).Decode(&req); err != nil || req.QueryID == "" {
		return
	}

	// streamCtx is cancelled when the node closes its end of the stream.
	streamCtx, streamCancel := context.WithCancel(context.Background())
	go func() {
		// Block until the stream is reset/closed, then cancel our context.
		buf := make([]byte, 1)
		s.Read(buf) //nolint:errcheck — we only care about EOF/reset
		streamCancel()
	}()
	defer streamCancel()

	resultCh := make(chan []common.SearchHit, 16)
	ix.pendingSearchesMu.Lock()
	ix.pendingSearches[req.QueryID] = resultCh
	ix.pendingSearchesMu.Unlock()
	defer func() {
		ix.pendingSearchesMu.Lock()
		delete(ix.pendingSearches, req.QueryID)
		ix.pendingSearchesMu.Unlock()
	}()

	// Check own referencedNodes immediately.
	if hits := ix.searchReferenced(req.PeerID, req.DID, req.Name); len(hits) > 0 {
		resultCh <- hits
	}

	// Broadcast search on GossipSub so other indexers can respond.
	ix.publishSearchQuery(req.QueryID, req.PeerID, req.DID, req.Name)

	// Stream results back to node as they arrive; reset idle timer on each result.
	enc := json.NewEncoder(s)
	idleTimer := time.NewTimer(searchTimeout())
	defer idleTimer.Stop()
	for {
		select {
		case hits := <-resultCh:
			if err := enc.Encode(common.SearchPeerResult{QueryID: req.QueryID, Records: hits}); err != nil {
				logger.Debug().Err(err).Msg("[search] stream write failed")
				return
			}
			// Reset idle timeout: keep alive as long as results trickle in.
			if !idleTimer.Stop() {
				select {
				case <-idleTimer.C:
				default:
				}
			}
			idleTimer.Reset(searchTimeout())
		case <-idleTimer.C:
			// No new result within timeout — close gracefully.
			return
		case <-streamCtx.Done():
			// Node closed the stream (new search superseded this one).
			return
		}
	}
}

// handleSearchPeerResponse is the ProtocolSearchPeerResponse handler.
// Another indexer opens this stream to deliver hits for a pending queryID.
func (ix *IndexerService) handleSearchPeerResponse(s network.Stream) {
	defer s.Reset()
	var result common.SearchPeerResult
	if err := json.NewDecoder(s).Decode(&result); err != nil || result.QueryID == "" {
		return
	}
	ix.pendingSearchesMu.Lock()
	ch := ix.pendingSearches[result.QueryID]
	ix.pendingSearchesMu.Unlock()
	if ch != nil {
		select {
		case ch <- result.Records:
		default: // channel full, drop — node may be slow
		}
	}
}

// publishSearchQuery broadcasts a SearchQuery on TopicSearchPeer.
func (ix *IndexerService) publishSearchQuery(queryID, peerID, did, name string) {
	ix.LongLivedStreamRecordedService.LongLivedPubSubService.PubsubMu.RLock()
	topic := ix.LongLivedStreamRecordedService.LongLivedPubSubService.LongLivedPubSubs[TopicSearchPeer]
	ix.LongLivedStreamRecordedService.LongLivedPubSubService.PubsubMu.RUnlock()
	if topic == nil {
		return
	}
	q := common.SearchQuery{
		QueryID:   queryID,
		PeerID:    peerID,
		DID:       did,
		Name:      name,
		EmitterID: ix.Host.ID().String(),
	}
	b, err := json.Marshal(q)
	if err != nil {
		return
	}
	_ = topic.Publish(context.Background(), b)
}

// initSearchSubscription joins TopicSearchPeer and dispatches incoming queries.
func (ix *IndexerService) initSearchSubscription() {
	logger := oclib.GetLogger()
	ix.LongLivedStreamRecordedService.LongLivedPubSubService.PubsubMu.Lock()
	topic, err := ix.PS.Join(TopicSearchPeer)
	if err != nil {
		ix.LongLivedStreamRecordedService.LongLivedPubSubService.PubsubMu.Unlock()
		logger.Err(err).Msg("[search] failed to join search topic")
		return
	}
	ix.LongLivedStreamRecordedService.LongLivedPubSubService.LongLivedPubSubs[TopicSearchPeer] = topic
	ix.LongLivedStreamRecordedService.LongLivedPubSubService.PubsubMu.Unlock()

	common.SubscribeEvents(
		ix.LongLivedStreamRecordedService.LongLivedPubSubService,
		context.Background(),
		TopicSearchPeer,
		-1,
		func(_ context.Context, q common.SearchQuery, _ string) {
			ix.onSearchQuery(q)
		},
	)
}

// onSearchQuery handles an incoming GossipSub search broadcast.
// If we have matching referencedNodes, we respond to the emitting indexer.
func (ix *IndexerService) onSearchQuery(q common.SearchQuery) {
	// Don't respond to our own broadcasts.
	if q.EmitterID == ix.Host.ID().String() {
		return
	}
	hits := ix.searchReferenced(q.PeerID, q.DID, q.Name)
	if len(hits) == 0 {
		return
	}
	emitterID, err := pp.Decode(q.EmitterID)
	if err != nil {
		return
	}
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()
	s, err := ix.Host.NewStream(ctx, emitterID, common.ProtocolSearchPeerResponse)
	if err != nil {
		return
	}
	defer s.Reset()
	s.SetDeadline(time.Now().Add(5 * time.Second))
	json.NewEncoder(s).Encode(common.SearchPeerResult{QueryID: q.QueryID, Records: hits})
}