// 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 indexnode

import (
	"context"
	"errors"
	"runtime"
	"strconv"
	"time"

	"github.com/milvus-io/milvus/internal/util/retry"

	"github.com/golang/protobuf/proto"
	"go.uber.org/zap"

	"github.com/milvus-io/milvus/internal/kv"
	etcdkv "github.com/milvus-io/milvus/internal/kv/etcd"
	"github.com/milvus-io/milvus/internal/log"
	"github.com/milvus-io/milvus/internal/proto/commonpb"
	"github.com/milvus-io/milvus/internal/proto/indexpb"
	"github.com/milvus-io/milvus/internal/storage"
	"github.com/milvus-io/milvus/internal/util/funcutil"
)

const (
	paramsKeyToParse   = "params"
	IndexBuildTaskName = "IndexBuildTask"
)

type task interface {
	Ctx() context.Context
	ID() UniqueID // return ReqID
	Name() string
	SetID(uid UniqueID) // set ReqID
	PreExecute(ctx context.Context) error
	Execute(ctx context.Context) error
	PostExecute(ctx context.Context) error
	WaitToFinish() error
	Notify(err error)
	OnEnqueue() error
	SetError(err error)
}

type BaseTask struct {
	done chan error
	ctx  context.Context
	id   UniqueID
	err  error
}

func (bt *BaseTask) SetError(err error) {
	bt.err = err
}

func (bt *BaseTask) ID() UniqueID {
	return bt.id
}

func (bt *BaseTask) setID(id UniqueID) {
	bt.id = id
}

func (bt *BaseTask) WaitToFinish() error {
	select {
	case <-bt.ctx.Done():
		return errors.New("timeout")
	case err := <-bt.done:
		return err
	}
}

func (bt *BaseTask) Notify(err error) {
	bt.done <- err
}

type IndexBuildTask struct {
	BaseTask
	index     Index
	kv        kv.BaseKV
	etcdKV    *etcdkv.EtcdKV
	savePaths []string
	req       *indexpb.CreateIndexRequest
	nodeID    UniqueID
}

func (it *IndexBuildTask) Ctx() context.Context {
	return it.ctx
}

func (it *IndexBuildTask) ID() UniqueID {
	return it.id
}

func (it *IndexBuildTask) SetID(ID UniqueID) {
	it.BaseTask.setID(ID)
}

func (bt *BaseTask) Name() string {
	return IndexBuildTaskName
}

func (it *IndexBuildTask) OnEnqueue() error {
	it.SetID(it.req.IndexBuildID)
	log.Debug("IndexNode IndexBuilderTask Enqueue", zap.Int64("TaskID", it.ID()))
	return nil
}

func (it *IndexBuildTask) checkIndexMeta(pre bool) error {
	fn := func() error {
		indexMeta := indexpb.IndexMeta{}
		_, values, versions, err := it.etcdKV.LoadWithPrefix2(it.req.MetaPath)
		if err != nil {
			log.Debug("IndexNode checkIndexMeta", zap.Any("load meta error with path", it.req.MetaPath),
				zap.Error(err), zap.Any("pre", pre))
			return err
		}
		log.Debug("IndexNode checkIndexMeta load meta success", zap.Any("path", it.req.MetaPath), zap.Any("pre", pre))
		err = proto.UnmarshalText(values[0], &indexMeta)
		if err != nil {
			log.Debug("IndexNode checkIndexMeta Unmarshal", zap.Error(err))
			return err
		}
		log.Debug("IndexNode checkIndexMeta Unmarshal success", zap.Any("IndexMeta", indexMeta))
		if indexMeta.Version > it.req.Version || indexMeta.State == commonpb.IndexState_Finished {
			log.Debug("IndexNode checkIndexMeta Notify build index this version is not the latest version", zap.Any("version", it.req.Version))
			return nil
		}
		if indexMeta.MarkDeleted {
			indexMeta.State = commonpb.IndexState_Finished
			v := proto.MarshalTextString(&indexMeta)
			err := it.etcdKV.CompareVersionAndSwap(it.req.MetaPath, versions[0], v)
			if err != nil {
				return err
			}
			return nil
		}
		if pre {
			return nil
		}
		indexMeta.IndexFilePaths = it.savePaths
		indexMeta.State = commonpb.IndexState_Finished
		if it.err != nil {
			indexMeta.State = commonpb.IndexState_Failed
		}
		err = it.etcdKV.CompareVersionAndSwap(it.req.MetaPath, versions[0],
			proto.MarshalTextString(&indexMeta))
		log.Debug("IndexNode checkIndexMeta CompareVersionAndSwap", zap.Error(err))
		return err
	}

	err := retry.Retry(3, time.Millisecond*200, fn)
	log.Debug("IndexNode checkIndexMeta final", zap.Error(err))
	return err

}

func (it *IndexBuildTask) PreExecute(ctx context.Context) error {
	log.Debug("IndexNode IndexBuildTask preExecute...")
	return it.checkIndexMeta(true)
}

func (it *IndexBuildTask) PostExecute(ctx context.Context) error {
	log.Debug("IndexNode IndexBuildTask PostExecute...")

	return it.checkIndexMeta(false)
}

func (it *IndexBuildTask) Execute(ctx context.Context) error {
	log.Debug("IndexNode IndexBuildTask Execute ...")
	var err error

	typeParams := make(map[string]string)
	for _, kvPair := range it.req.GetTypeParams() {
		key, value := kvPair.GetKey(), kvPair.GetValue()
		_, ok := typeParams[key]
		if ok {
			return errors.New("duplicated key in type params")
		}
		if key == paramsKeyToParse {
			params, err := funcutil.ParseIndexParamsMap(value)
			if err != nil {
				return err
			}
			for pk, pv := range params {
				typeParams[pk] = pv
			}
		} else {
			typeParams[key] = value
		}
	}

	indexParams := make(map[string]string)
	for _, kvPair := range it.req.GetIndexParams() {
		key, value := kvPair.GetKey(), kvPair.GetValue()
		_, ok := indexParams[key]
		if ok {
			return errors.New("duplicated key in index params")
		}
		if key == paramsKeyToParse {
			params, err := funcutil.ParseIndexParamsMap(value)
			if err != nil {
				return err
			}
			for pk, pv := range params {
				indexParams[pk] = pv
			}
		} else {
			indexParams[key] = value
		}
	}

	it.index, err = NewCIndex(typeParams, indexParams)
	if err != nil {
		log.Error("IndexNode IndexBuildTask Execute NewCIndex failed", zap.Error(err))
		return err
	}
	defer func() {
		err = it.index.Delete()
		if err != nil {
			log.Warn("IndexNode IndexBuildTask Execute CIndexDelete Failed", zap.Error(err))
		}
	}()

	getKeyByPathNaive := func(path string) string {
		// splitElements := strings.Split(path, "/")
		// return splitElements[len(splitElements)-1]
		return path
	}
	getValueByPath := func(path string) ([]byte, error) {
		data, err := it.kv.Load(path)
		if err != nil {
			return nil, err
		}
		return []byte(data), nil
	}
	getBlobByPath := func(path string) (*Blob, error) {
		value, err := getValueByPath(path)
		if err != nil {
			return nil, err
		}
		return &Blob{
			Key:   getKeyByPathNaive(path),
			Value: value,
		}, nil
	}
	getStorageBlobs := func(blobs []*Blob) []*storage.Blob {
		return blobs
	}

	toLoadDataPaths := it.req.GetDataPaths()
	keys := make([]string, len(toLoadDataPaths))
	blobs := make([]*Blob, len(toLoadDataPaths))

	loadKey := func(idx int) error {
		keys[idx] = getKeyByPathNaive(toLoadDataPaths[idx])
		blob, err := getBlobByPath(toLoadDataPaths[idx])
		if err != nil {
			return err
		}

		blobs[idx] = blob

		return nil
	}
	err = funcutil.ProcessFuncParallel(len(toLoadDataPaths), runtime.NumCPU(), loadKey, "loadKey")
	if err != nil {
		return err
	}

	storageBlobs := getStorageBlobs(blobs)
	var insertCodec storage.InsertCodec
	defer insertCodec.Close()
	partitionID, segmentID, insertData, err2 := insertCodec.Deserialize(storageBlobs)
	if err2 != nil {
		return err2
	}
	if len(insertData.Data) != 1 {
		return errors.New("we expect only one field in deserialized insert data")
	}

	for _, value := range insertData.Data {
		// TODO: BinaryVectorFieldData
		floatVectorFieldData, fOk := value.(*storage.FloatVectorFieldData)
		if fOk {
			err = it.index.BuildFloatVecIndexWithoutIds(floatVectorFieldData.Data)
			if err != nil {
				log.Error("IndexNode BuildFloatVecIndexWithoutIds failed", zap.Error(err))
				return err
			}
		}

		binaryVectorFieldData, bOk := value.(*storage.BinaryVectorFieldData)
		if bOk {
			err = it.index.BuildBinaryVecIndexWithoutIds(binaryVectorFieldData.Data)
			if err != nil {
				log.Error("IndexNode BuildBinaryVecIndexWithoutIds failed", zap.Error(err))
				return err
			}
		}

		if !fOk && !bOk {
			return errors.New("we expect FloatVectorFieldData or BinaryVectorFieldData")
		}

		indexBlobs, err := it.index.Serialize()
		if err != nil {
			log.Error("IndexNode index Serialize failed", zap.Error(err))

			return err
		}

		var indexCodec storage.IndexCodec
		serializedIndexBlobs, err := indexCodec.Serialize(getStorageBlobs(indexBlobs), indexParams, it.req.IndexName, it.req.IndexID)
		if err != nil {
			return err
		}

		getSavePathByKey := func(key string) string {
			// TODO: fix me, use more reasonable method
			return strconv.Itoa(int(it.req.IndexBuildID)) + "/" + strconv.Itoa(int(it.req.Version)) + "/" + strconv.Itoa(int(partitionID)) + "/" + strconv.Itoa(int(segmentID)) + "/" + key
		}
		saveBlob := func(path string, value []byte) error {
			return it.kv.Save(path, string(value))
		}

		it.savePaths = make([]string, len(serializedIndexBlobs))
		saveIndexFile := func(idx int) error {
			blob := serializedIndexBlobs[idx]
			key, value := blob.Key, blob.Value

			savePath := getSavePathByKey(key)

			saveIndexFileFn := func() error {
				v, err := it.etcdKV.Load(it.req.MetaPath)
				if err != nil {
					log.Debug("IndexNode load meta failed", zap.Any("path", it.req.MetaPath), zap.Error(err))
					return err
				}
				indexMeta := indexpb.IndexMeta{}
				err = proto.UnmarshalText(v, &indexMeta)
				if err != nil {
					log.Debug("IndexNode Unmarshal indexMeta error ", zap.Error(err))
					return err
				}
				log.Debug("IndexNode Unmarshal indexMeta success ", zap.Any("meta", indexMeta))
				if indexMeta.Version > it.req.Version {
					log.Debug("IndexNode try saveIndexFile failed req.Version is low", zap.Any("req.Version", it.req.Version),
						zap.Any("indexMeta.Version", indexMeta.Version))
					return errors.New("This task has been reassigned ")
				}
				return saveBlob(savePath, value)
			}
			err := retry.Retry(5, time.Millisecond*200, saveIndexFileFn)
			log.Debug("IndexNode try saveIndexFile final", zap.Error(err), zap.Any("savePath", savePath))
			if err != nil {
				return err
			}

			it.savePaths[idx] = savePath

			return nil
		}
		err = funcutil.ProcessFuncParallel(len(serializedIndexBlobs), runtime.NumCPU(), saveIndexFile, "saveIndexFile")
		if err != nil {
			return err
		}
	}
	// err = it.index.Delete()
	// if err != nil {
	// 	log.Print("CIndexDelete Failed")
	// }
	return nil
}