// Copyright (C) 2019-2020 Zilliz. All rights reserved.
//
// 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 querynode

import (
	"context"
	"errors"
	"fmt"
	"path"
	"sort"
	"strconv"
	"strings"
	"sync"
	"time"

	"go.uber.org/zap"

	"github.com/milvus-io/milvus/internal/kv"
	minioKV "github.com/milvus-io/milvus/internal/kv/minio"
	"github.com/milvus-io/milvus/internal/log"
	"github.com/milvus-io/milvus/internal/msgstream"
	"github.com/milvus-io/milvus/internal/proto/commonpb"
	"github.com/milvus-io/milvus/internal/proto/indexpb"
	"github.com/milvus-io/milvus/internal/proto/internalpb"
	"github.com/milvus-io/milvus/internal/proto/milvuspb"
	"github.com/milvus-io/milvus/internal/storage"
	"github.com/milvus-io/milvus/internal/types"
)

type indexParam = map[string]string

type indexLoader struct {
	replica ReplicaInterface

	fieldIndexes   map[string][]*internalpb.IndexStats
	fieldStatsChan chan []*internalpb.FieldStats

	masterService types.MasterService
	indexService  types.IndexService

	kv kv.BaseKV // minio kv
}

func (loader *indexLoader) doLoadIndex(wg *sync.WaitGroup) {
	collectionIDs, _, segmentIDs := loader.replica.getSegmentsBySegmentType(segmentTypeSealed)
	if len(collectionIDs) <= 0 {
		wg.Done()
		return
	}
	log.Debug("do load index for sealed segments:", zap.String("segmentIDs", fmt.Sprintln(segmentIDs)))
	for i := range collectionIDs {
		// we don't need index id yet
		segment, err := loader.replica.getSegmentByID(segmentIDs[i])
		if err != nil {
			log.Warn(err.Error())
			continue
		}
		vecFieldIDs, err := loader.replica.getVecFieldIDsByCollectionID(collectionIDs[i])
		if err != nil {
			log.Warn(err.Error())
			continue
		}
		for _, fieldID := range vecFieldIDs {
			err = loader.setIndexInfo(collectionIDs[i], segment, fieldID)
			if err != nil {
				log.Warn(err.Error())
				continue
			}

			err = loader.loadIndex(segment, fieldID)
			if err != nil {
				log.Warn(err.Error())
				continue
			}
		}
	}
	// sendQueryNodeStats
	err := loader.sendQueryNodeStats()
	if err != nil {
		log.Error(err.Error())
		wg.Done()
		return
	}

	wg.Done()
}

func (loader *indexLoader) loadIndex(segment *Segment, fieldID int64) error {
	// 1. use msg's index paths to get index bytes
	var err error
	var indexBuffer [][]byte
	var indexParams indexParam
	var indexName string
	fn := func() error {
		indexPaths := segment.getIndexPaths(fieldID)
		indexBuffer, indexParams, indexName, err = loader.getIndexBinlog(indexPaths)
		if err != nil {
			return err
		}
		return nil
	}
	err = msgstream.Retry(5, time.Millisecond*200, fn)
	if err != nil {
		return err
	}
	err = segment.setIndexName(fieldID, indexName)
	if err != nil {
		return err
	}
	err = segment.setIndexParam(fieldID, indexParams)
	if err != nil {
		return err
	}
	ok := segment.checkIndexReady(fieldID)
	if !ok {
		// no error
		return errors.New("index info is not set correctly")
	}
	// 2. use index bytes and index path to update segment
	err = segment.updateSegmentIndex(indexBuffer, fieldID)
	if err != nil {
		return err
	}
	// 3. drop vector field data if index loaded successfully
	err = segment.dropFieldData(fieldID)
	if err != nil {
		return err
	}
	// 4. update segment index stats
	err = loader.updateSegmentIndexStats(segment)
	if err != nil {
		return err
	}
	log.Debug("load index done")
	return nil
}

func (loader *indexLoader) printIndexParams(index []*commonpb.KeyValuePair) {
	log.Debug("=================================================")
	for i := 0; i < len(index); i++ {
		log.Debug(fmt.Sprintln(index[i]))
	}
}

func (loader *indexLoader) indexParamsEqual(index1 []*commonpb.KeyValuePair, index2 []*commonpb.KeyValuePair) bool {
	if len(index1) != len(index2) {
		return false
	}

	for i := 0; i < len(index1); i++ {
		kv1 := *index1[i]
		kv2 := *index2[i]
		if kv1.Key != kv2.Key || kv1.Value != kv2.Value {
			return false
		}
	}

	return true
}

func (loader *indexLoader) fieldsStatsIDs2Key(collectionID UniqueID, fieldID UniqueID) string {
	return strconv.FormatInt(collectionID, 10) + "/" + strconv.FormatInt(fieldID, 10)
}

func (loader *indexLoader) fieldsStatsKey2IDs(key string) (UniqueID, UniqueID, error) {
	ids := strings.Split(key, "/")
	if len(ids) != 2 {
		return 0, 0, errors.New("illegal fieldsStatsKey")
	}
	collectionID, err := strconv.ParseInt(ids[0], 10, 64)
	if err != nil {
		return 0, 0, err
	}
	fieldID, err := strconv.ParseInt(ids[1], 10, 64)
	if err != nil {
		return 0, 0, err
	}
	return collectionID, fieldID, nil
}

func (loader *indexLoader) updateSegmentIndexStats(segment *Segment) error {
	for fieldID := range segment.indexInfos {
		fieldStatsKey := loader.fieldsStatsIDs2Key(segment.collectionID, fieldID)
		_, ok := loader.fieldIndexes[fieldStatsKey]
		newIndexParams := make([]*commonpb.KeyValuePair, 0)
		indexParams := segment.getIndexParams(fieldID)
		for k, v := range indexParams {
			newIndexParams = append(newIndexParams, &commonpb.KeyValuePair{
				Key:   k,
				Value: v,
			})
		}

		// sort index params by key
		sort.Slice(newIndexParams, func(i, j int) bool { return newIndexParams[i].Key < newIndexParams[j].Key })
		if !ok {
			loader.fieldIndexes[fieldStatsKey] = make([]*internalpb.IndexStats, 0)
			loader.fieldIndexes[fieldStatsKey] = append(loader.fieldIndexes[fieldStatsKey],
				&internalpb.IndexStats{
					IndexParams:        newIndexParams,
					NumRelatedSegments: 1,
				})
		} else {
			isNewIndex := true
			for _, index := range loader.fieldIndexes[fieldStatsKey] {
				if loader.indexParamsEqual(newIndexParams, index.IndexParams) {
					index.NumRelatedSegments++
					isNewIndex = false
				}
			}
			if isNewIndex {
				loader.fieldIndexes[fieldStatsKey] = append(loader.fieldIndexes[fieldStatsKey],
					&internalpb.IndexStats{
						IndexParams:        newIndexParams,
						NumRelatedSegments: 1,
					})
			}
		}
	}

	return nil
}

func (loader *indexLoader) getIndexBinlog(indexPath []string) ([][]byte, indexParam, string, error) {
	index := make([][]byte, 0)

	var indexParams indexParam
	var indexName string
	for _, p := range indexPath {
		log.Debug("", zap.String("load path", fmt.Sprintln(indexPath)))
		indexPiece, err := loader.kv.Load(p)
		if err != nil {
			return nil, nil, "", err
		}
		// get index params when detecting indexParamPrefix
		if path.Base(p) == storage.IndexParamsFile {
			indexCodec := storage.NewIndexCodec()
			_, indexParams, indexName, _, err = indexCodec.Deserialize([]*storage.Blob{
				{
					Key:   storage.IndexParamsFile,
					Value: []byte(indexPiece),
				},
			})
			if err != nil {
				return nil, nil, "", err
			}
		} else {
			index = append(index, []byte(indexPiece))
		}
	}

	if len(indexParams) <= 0 {
		return nil, nil, "", errors.New("cannot find index param")
	}
	return index, indexParams, indexName, nil
}

func (loader *indexLoader) sendQueryNodeStats() error {
	resultFieldsStats := make([]*internalpb.FieldStats, 0)
	for fieldStatsKey, indexStats := range loader.fieldIndexes {
		colID, fieldID, err := loader.fieldsStatsKey2IDs(fieldStatsKey)
		if err != nil {
			return err
		}
		fieldStats := internalpb.FieldStats{
			CollectionID: colID,
			FieldID:      fieldID,
			IndexStats:   indexStats,
		}
		resultFieldsStats = append(resultFieldsStats, &fieldStats)
	}

	loader.fieldStatsChan <- resultFieldsStats
	log.Debug("sent field stats")
	return nil
}

func (loader *indexLoader) setIndexInfo(collectionID UniqueID, segment *Segment, fieldID UniqueID) error {
	ctx := context.TODO()
	req := &milvuspb.DescribeSegmentRequest{
		Base: &commonpb.MsgBase{
			MsgType: commonpb.MsgType_DescribeSegment,
		},
		CollectionID: collectionID,
		SegmentID:    segment.segmentID,
	}
	response, err := loader.masterService.DescribeSegment(ctx, req)
	if err != nil {
		return err
	}
	if response.Status.ErrorCode != commonpb.ErrorCode_Success {
		return errors.New(response.Status.Reason)
	}

	if !response.EnableIndex {
		return errors.New("there are no indexes on this segment")
	}

	if loader.indexService == nil {
		return errors.New("null index service client")
	}

	indexFilePathRequest := &indexpb.GetIndexFilePathsRequest{
		IndexBuildIDs: []UniqueID{response.BuildID},
	}
	pathResponse, err := loader.indexService.GetIndexFilePaths(ctx, indexFilePathRequest)
	if err != nil || pathResponse.Status.ErrorCode != commonpb.ErrorCode_Success {
		return err
	}

	if len(pathResponse.FilePaths) <= 0 {
		return errors.New("illegal index file paths")
	}

	info := &indexInfo{
		indexID:    response.IndexID,
		buildID:    response.BuildID,
		indexPaths: pathResponse.FilePaths[0].IndexFilePaths,
		readyLoad:  true,
	}
	segment.setEnableIndex(response.EnableIndex)
	err = segment.setIndexInfo(fieldID, info)
	if err != nil {
		return err
	}

	return nil
}

func (loader *indexLoader) getIndexPaths(indexBuildID UniqueID) ([]string, error) {
	ctx := context.TODO()
	if loader.indexService == nil {
		return nil, errors.New("null index service client")
	}

	indexFilePathRequest := &indexpb.GetIndexFilePathsRequest{
		IndexBuildIDs: []UniqueID{indexBuildID},
	}
	pathResponse, err := loader.indexService.GetIndexFilePaths(ctx, indexFilePathRequest)
	if err != nil || pathResponse.Status.ErrorCode != commonpb.ErrorCode_Success {
		return nil, err
	}

	if len(pathResponse.FilePaths) <= 0 {
		return nil, errors.New("illegal index file paths")
	}

	return pathResponse.FilePaths[0].IndexFilePaths, nil
}

func newIndexLoader(ctx context.Context, masterService types.MasterService, indexService types.IndexService, replica ReplicaInterface) *indexLoader {
	option := &minioKV.Option{
		Address:           Params.MinioEndPoint,
		AccessKeyID:       Params.MinioAccessKeyID,
		SecretAccessKeyID: Params.MinioSecretAccessKey,
		UseSSL:            Params.MinioUseSSLStr,
		CreateBucket:      true,
		BucketName:        Params.MinioBucketName,
	}

	client, err := minioKV.NewMinIOKV(ctx, option)
	if err != nil {
		panic(err)
	}

	return &indexLoader{
		replica: replica,

		fieldIndexes:   make(map[string][]*internalpb.IndexStats),
		fieldStatsChan: make(chan []*internalpb.FieldStats, 1024),

		masterService: masterService,
		indexService:  indexService,

		kv: client,
	}
}