package querynode

import "C"
import (
	"context"
	"errors"
	"strconv"
	"strings"
	"sync"

	"go.uber.org/zap"

	"github.com/golang/protobuf/proto"
	"github.com/zilliztech/milvus-distributed/internal/log"
	"github.com/zilliztech/milvus-distributed/internal/msgstream"
	"github.com/zilliztech/milvus-distributed/internal/proto/commonpb"
	"github.com/zilliztech/milvus-distributed/internal/proto/internalpb"
	"github.com/zilliztech/milvus-distributed/internal/proto/milvuspb"
)

type searchService struct {
	ctx    context.Context
	wait   sync.WaitGroup
	cancel context.CancelFunc

	replica      ReplicaInterface
	tSafeWatcher *tSafeWatcher

	serviceableTimeMutex sync.Mutex // guards serviceableTime
	serviceableTime      Timestamp

	msgBuffer             chan msgstream.TsMsg
	unsolvedMsg           []msgstream.TsMsg
	searchMsgStream       msgstream.MsgStream
	searchResultMsgStream msgstream.MsgStream
	queryNodeID           UniqueID
}

type ResultEntityIds []UniqueID

func newSearchService(ctx context.Context, replica ReplicaInterface, factory msgstream.Factory) *searchService {
	receiveBufSize := Params.SearchReceiveBufSize

	searchStream, _ := factory.NewQueryMsgStream(ctx)
	searchResultStream, _ := factory.NewQueryMsgStream(ctx)

	// query node doesn't need to consumer any search or search result channel actively.
	consumeChannels := Params.SearchChannelNames
	consumeSubName := Params.MsgChannelSubName
	searchStream.AsConsumer(consumeChannels, consumeSubName)
	log.Debug("querynode AsConsumer: " + strings.Join(consumeChannels, ", ") + " : " + consumeSubName)
	producerChannels := Params.SearchResultChannelNames
	searchResultStream.AsProducer(producerChannels)
	log.Debug("querynode AsProducer: " + strings.Join(producerChannels, ", "))

	searchServiceCtx, searchServiceCancel := context.WithCancel(ctx)
	msgBuffer := make(chan msgstream.TsMsg, receiveBufSize)
	unsolvedMsg := make([]msgstream.TsMsg, 0)
	return &searchService{
		ctx:             searchServiceCtx,
		cancel:          searchServiceCancel,
		serviceableTime: Timestamp(0),
		msgBuffer:       msgBuffer,
		unsolvedMsg:     unsolvedMsg,

		replica:      replica,
		tSafeWatcher: newTSafeWatcher(),

		searchMsgStream:       searchStream,
		searchResultMsgStream: searchResultStream,
		queryNodeID:           Params.QueryNodeID,
	}
}

func (ss *searchService) start() {
	ss.searchMsgStream.Start()
	ss.searchResultMsgStream.Start()
	ss.register()
	ss.wait.Add(2)
	go ss.receiveSearchMsg()
	go ss.doUnsolvedMsgSearch()
	ss.wait.Wait()
}

func (ss *searchService) close() {
	if ss.searchMsgStream != nil {
		ss.searchMsgStream.Close()
	}
	if ss.searchResultMsgStream != nil {
		ss.searchResultMsgStream.Close()
	}
	ss.cancel()
}

func (ss *searchService) register() {
	tSafe := ss.replica.getTSafe()
	tSafe.registerTSafeWatcher(ss.tSafeWatcher)
}

func (ss *searchService) waitNewTSafe() Timestamp {
	// block until dataSyncService updating tSafe
	ss.tSafeWatcher.hasUpdate()
	timestamp := ss.replica.getTSafe().get()
	return timestamp
}

func (ss *searchService) getServiceableTime() Timestamp {
	ss.serviceableTimeMutex.Lock()
	defer ss.serviceableTimeMutex.Unlock()
	return ss.serviceableTime
}

func (ss *searchService) setServiceableTime(t Timestamp) {
	ss.serviceableTimeMutex.Lock()
	// hard code gracefultime to 1 second
	// TODO: use config to set gracefultime
	ss.serviceableTime = t + 1000*1000*1000
	ss.serviceableTimeMutex.Unlock()
}

func (ss *searchService) receiveSearchMsg() {
	defer ss.wait.Done()
	for {
		select {
		case <-ss.ctx.Done():
			return
		default:
			msgPack, _ := ss.searchMsgStream.Consume()
			if msgPack == nil || len(msgPack.Msgs) <= 0 {
				continue
			}
			searchMsg := make([]msgstream.TsMsg, 0)
			serverTime := ss.getServiceableTime()
			for i, msg := range msgPack.Msgs {
				if msg.BeginTs() > serverTime {
					ss.msgBuffer <- msg
					continue
				}
				searchMsg = append(searchMsg, msgPack.Msgs[i])
			}
			for _, msg := range searchMsg {
				err := ss.search(msg)
				if err != nil {
					log.Error(err.Error())
					err2 := ss.publishFailedSearchResult(msg, err.Error())
					if err2 != nil {
						log.Error("publish FailedSearchResult failed", zap.Error(err2))
					}
				}
			}
			log.Debug("ReceiveSearchMsg, do search done", zap.Int("num of searchMsg", len(searchMsg)))
		}
	}
}

func (ss *searchService) doUnsolvedMsgSearch() {
	defer ss.wait.Done()
	for {
		select {
		case <-ss.ctx.Done():
			return
		default:
			serviceTime := ss.waitNewTSafe()
			ss.setServiceableTime(serviceTime)
			searchMsg := make([]msgstream.TsMsg, 0)
			tempMsg := make([]msgstream.TsMsg, 0)
			tempMsg = append(tempMsg, ss.unsolvedMsg...)
			ss.unsolvedMsg = ss.unsolvedMsg[:0]
			for _, msg := range tempMsg {
				if msg.EndTs() <= serviceTime {
					searchMsg = append(searchMsg, msg)
					continue
				}
				ss.unsolvedMsg = append(ss.unsolvedMsg, msg)
			}

			for {
				msgBufferLength := len(ss.msgBuffer)
				if msgBufferLength <= 0 {
					break
				}
				msg := <-ss.msgBuffer
				if msg.EndTs() <= serviceTime {
					searchMsg = append(searchMsg, msg)
					continue
				}
				ss.unsolvedMsg = append(ss.unsolvedMsg, msg)
			}

			if len(searchMsg) <= 0 {
				continue
			}
			for _, msg := range searchMsg {
				err := ss.search(msg)
				if err != nil {
					log.Error(err.Error())
					err2 := ss.publishFailedSearchResult(msg, err.Error())
					if err2 != nil {
						log.Error("publish FailedSearchResult failed", zap.Error(err2))
					}
				}
			}
			log.Debug("doUnsolvedMsgSearch, do search done", zap.Int("num of searchMsg", len(searchMsg)))
		}
	}
}

// TODO:: cache map[dsl]plan
// TODO: reBatched search requests
func (ss *searchService) search(msg msgstream.TsMsg) error {
	searchMsg, ok := msg.(*msgstream.SearchMsg)
	if !ok {
		return errors.New("invalid request type = " + string(msg.Type()))
	}

	searchTimestamp := searchMsg.Base.Timestamp
	var queryBlob = searchMsg.Query.Value
	query := milvuspb.SearchRequest{}
	err := proto.Unmarshal(queryBlob, &query)
	if err != nil {
		return errors.New("unmarshal query failed")
	}
	collectionID := searchMsg.CollectionID
	collection, err := ss.replica.getCollectionByID(collectionID)
	if err != nil {
		return err
	}
	dsl := query.Dsl
	plan, err := createPlan(*collection, dsl)
	if err != nil {
		return err
	}
	placeHolderGroupBlob := query.PlaceholderGroup
	placeholderGroup, err := parserPlaceholderGroup(plan, placeHolderGroupBlob)
	if err != nil {
		return err
	}
	placeholderGroups := make([]*PlaceholderGroup, 0)
	placeholderGroups = append(placeholderGroups, placeholderGroup)

	searchResults := make([]*SearchResult, 0)
	matchedSegments := make([]*Segment, 0)

	//log.Debug("search msg's partitionID = ", partitionIDsInQuery)
	partitionIDsInCol, err := ss.replica.getPartitionIDs(collectionID)
	if err != nil {
		return err
	}
	var searchPartitionIDs []UniqueID
	partitionIDsInQuery := searchMsg.PartitionIDs
	if len(partitionIDsInQuery) == 0 {
		if len(partitionIDsInCol) == 0 {
			return errors.New("can't find any partition in this collection on query node")
		}
		searchPartitionIDs = partitionIDsInCol
	} else {
		findPartition := false
		for _, id := range partitionIDsInQuery {
			_, err := ss.replica.getPartitionByID(id)
			if err == nil {
				searchPartitionIDs = append(searchPartitionIDs, id)
				findPartition = true
			}
		}
		if !findPartition {
			return errors.New("partition to be searched not exist in query node")
		}
	}

	for _, partitionID := range searchPartitionIDs {
		segmentIDs, err := ss.replica.getSegmentIDs(partitionID)
		if err != nil {
			return err
		}
		for _, segmentID := range segmentIDs {
			//log.Debug("dsl = ", dsl)
			segment, err := ss.replica.getSegmentByID(segmentID)
			if err != nil {
				return err
			}
			searchResult, err := segment.segmentSearch(plan, placeholderGroups, []Timestamp{searchTimestamp})

			if err != nil {
				return err
			}
			searchResults = append(searchResults, searchResult)
			matchedSegments = append(matchedSegments, segment)
		}
	}

	if len(searchResults) <= 0 {
		for _, group := range placeholderGroups {
			nq := group.getNumOfQuery()
			nilHits := make([][]byte, nq)
			hit := &milvuspb.Hits{}
			for i := 0; i < int(nq); i++ {
				bs, err := proto.Marshal(hit)
				if err != nil {
					return err
				}
				nilHits[i] = bs
			}
			resultChannelInt, _ := strconv.ParseInt(searchMsg.ResultChannelID, 10, 64)
			searchResultMsg := &msgstream.SearchResultMsg{
				BaseMsg: msgstream.BaseMsg{HashValues: []uint32{uint32(resultChannelInt)}},
				SearchResults: internalpb.SearchResults{
					Base: &commonpb.MsgBase{
						MsgType:   commonpb.MsgType_SearchResult,
						MsgID:     searchMsg.Base.MsgID,
						Timestamp: searchTimestamp,
						SourceID:  searchMsg.Base.SourceID,
					},
					Status:          &commonpb.Status{ErrorCode: commonpb.ErrorCode_Success},
					ResultChannelID: searchMsg.ResultChannelID,
					Hits:            nilHits,
					MetricType:      plan.getMetricType(),
				},
			}
			err = ss.publishSearchResult(searchResultMsg)
			if err != nil {
				return err
			}
			return nil
		}
	}

	inReduced := make([]bool, len(searchResults))
	numSegment := int64(len(searchResults))
	err2 := reduceSearchResults(searchResults, numSegment, inReduced)
	if err2 != nil {
		return err2
	}
	err = fillTargetEntry(plan, searchResults, matchedSegments, inReduced)
	if err != nil {
		return err
	}
	marshaledHits, err := reorganizeQueryResults(plan, placeholderGroups, searchResults, numSegment, inReduced)
	if err != nil {
		return err
	}
	hitsBlob, err := marshaledHits.getHitsBlob()
	if err != nil {
		return err
	}

	var offset int64 = 0
	for index := range placeholderGroups {
		hitBlobSizePeerQuery, err := marshaledHits.hitBlobSizeInGroup(int64(index))
		if err != nil {
			return err
		}
		hits := make([][]byte, 0)
		for _, len := range hitBlobSizePeerQuery {
			hits = append(hits, hitsBlob[offset:offset+len])
			//test code to checkout marshaled hits
			//marshaledHit := hitsBlob[offset:offset+len]
			//unMarshaledHit := milvuspb.Hits{}
			//err = proto.Unmarshal(marshaledHit, &unMarshaledHit)
			//if err != nil {
			//	return err
			//}
			//log.Debug("hits msg  = ", unMarshaledHit)
			offset += len
		}
		resultChannelInt, _ := strconv.ParseInt(searchMsg.ResultChannelID, 10, 64)
		searchResultMsg := &msgstream.SearchResultMsg{
			BaseMsg: msgstream.BaseMsg{HashValues: []uint32{uint32(resultChannelInt)}},
			SearchResults: internalpb.SearchResults{
				Base: &commonpb.MsgBase{
					MsgType:   commonpb.MsgType_SearchResult,
					MsgID:     searchMsg.Base.MsgID,
					Timestamp: searchTimestamp,
					SourceID:  searchMsg.Base.SourceID,
				},
				Status:          &commonpb.Status{ErrorCode: commonpb.ErrorCode_Success},
				ResultChannelID: searchMsg.ResultChannelID,
				Hits:            hits,
				MetricType:      plan.getMetricType(),
			},
		}

		// For debugging, please don't delete.
		//for i := 0; i < len(hits); i++ {
		//	testHits := milvuspb.Hits{}
		//	err := proto.Unmarshal(hits[i], &testHits)
		//	if err != nil {
		//		panic(err)
		//	}
		//	log.Debug(testHits.IDs)
		//	log.Debug(testHits.Scores)
		//}
		err = ss.publishSearchResult(searchResultMsg)
		if err != nil {
			return err
		}
	}

	deleteSearchResults(searchResults)
	deleteMarshaledHits(marshaledHits)
	plan.delete()
	placeholderGroup.delete()
	return nil
}

func (ss *searchService) publishSearchResult(msg msgstream.TsMsg) error {
	// span, ctx := opentracing.StartSpanFromContext(msg.GetMsgContext(), "publish search result")
	// defer span.Finish()
	// msg.SetMsgContext(ctx)
	msgPack := msgstream.MsgPack{}
	msgPack.Msgs = append(msgPack.Msgs, msg)
	err := ss.searchResultMsgStream.Produce(context.TODO(), &msgPack)
	return err
}

func (ss *searchService) publishFailedSearchResult(msg msgstream.TsMsg, errMsg string) error {
	// span, ctx := opentracing.StartSpanFromContext(msg.GetMsgContext(), "receive search msg")
	// defer span.Finish()
	// msg.SetMsgContext(ctx)
	//log.Debug("Public fail SearchResult!")
	msgPack := msgstream.MsgPack{}
	searchMsg, ok := msg.(*msgstream.SearchMsg)
	if !ok {
		return errors.New("invalid request type = " + string(msg.Type()))
	}

	resultChannelInt, _ := strconv.ParseInt(searchMsg.ResultChannelID, 10, 64)
	searchResultMsg := &msgstream.SearchResultMsg{
		BaseMsg: msgstream.BaseMsg{HashValues: []uint32{uint32(resultChannelInt)}},
		SearchResults: internalpb.SearchResults{
			Base: &commonpb.MsgBase{
				MsgType:   commonpb.MsgType_SearchResult,
				MsgID:     searchMsg.Base.MsgID,
				Timestamp: searchMsg.Base.Timestamp,
				SourceID:  searchMsg.Base.SourceID,
			},
			Status:          &commonpb.Status{ErrorCode: commonpb.ErrorCode_UnexpectedError, Reason: errMsg},
			ResultChannelID: searchMsg.ResultChannelID,
			Hits:            [][]byte{},
		},
	}

	msgPack.Msgs = append(msgPack.Msgs, searchResultMsg)
	err := ss.searchResultMsgStream.Produce(context.TODO(), &msgPack)
	if err != nil {
		return err
	}

	return nil
}