// Licensed to the LF AI & Data foundation under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you 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 rootcoord

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

	"github.com/golang/protobuf/proto"
	"github.com/milvus-io/milvus/internal/kv"
	"github.com/milvus-io/milvus/internal/log"
	"github.com/milvus-io/milvus/internal/proto/commonpb"
	"github.com/milvus-io/milvus/internal/proto/datapb"
	"github.com/milvus-io/milvus/internal/proto/milvuspb"
	"github.com/milvus-io/milvus/internal/proto/rootcoordpb"
	"go.uber.org/zap"
)

const (
	Bucket               = "bucket"
	FailedReason         = "failed_reason"
	Files                = "files"
	MaxPendingCount      = 32
	delimiter            = "/"
	taskExpiredMsgPrefix = "task has expired after "
)

// import task state
type importTaskState struct {
	stateCode    commonpb.ImportState // state code
	segments     []int64              // ID list of generated segments
	rowIDs       []int64              // ID list of auto-generated is for auto-id primary key
	rowCount     int64                // how many rows imported
	failedReason string               // failed reason
}

// importManager manager for import tasks
type importManager struct {
	ctx       context.Context // reserved
	taskStore kv.MetaKv       // Persistent task info storage.
	busyNodes map[int64]bool  // Set of all current working DataNodes.

	// TODO: Make pendingTask a map to improve look up performance.
	pendingTasks  []*datapb.ImportTaskInfo         // pending tasks
	workingTasks  map[int64]*datapb.ImportTaskInfo // in-progress tasks
	pendingLock   sync.RWMutex                     // lock pending task list
	workingLock   sync.RWMutex                     // lock working task map
	busyNodesLock sync.RWMutex                     // lock for working nodes.
	nextTaskID    int64                            // for generating next import task ID
	lastReqID     int64                            // for generating a unique ID for import request

	startOnce sync.Once

	callImportService func(ctx context.Context, req *datapb.ImportTaskRequest) *datapb.ImportTaskResponse
}

// newImportManager helper function to create a importManager
func newImportManager(ctx context.Context, client kv.MetaKv,
	importService func(ctx context.Context, req *datapb.ImportTaskRequest) *datapb.ImportTaskResponse) *importManager {
	mgr := &importManager{
		ctx:               ctx,
		taskStore:         client,
		pendingTasks:      make([]*datapb.ImportTaskInfo, 0, MaxPendingCount), // currently task queue max size is 32
		workingTasks:      make(map[int64]*datapb.ImportTaskInfo),
		busyNodes:         make(map[int64]bool),
		pendingLock:       sync.RWMutex{},
		workingLock:       sync.RWMutex{},
		busyNodesLock:     sync.RWMutex{},
		nextTaskID:        0,
		lastReqID:         0,
		callImportService: importService,
	}
	return mgr
}

func (m *importManager) init(ctx context.Context) {
	m.startOnce.Do(func() {
		// Read tasks from Etcd and save them as pending tasks or working tasks.
		m.loadFromTaskStore()
		// Send out tasks to dataCoord.
		m.sendOutTasks(ctx)
	})
}

// sendOutTasks pushes all pending tasks to DataCoord, gets DataCoord response and re-add these tasks as working tasks.
func (m *importManager) sendOutTasks(ctx context.Context) error {
	m.pendingLock.Lock()
	m.busyNodesLock.Lock()
	defer m.pendingLock.Unlock()
	defer m.busyNodesLock.Unlock()

	// Trigger Import() action to DataCoord.
	for len(m.pendingTasks) > 0 {
		task := m.pendingTasks[0]
		// Skip failed (mostly like expired) tasks.
		if task.GetState().GetStateCode() == commonpb.ImportState_ImportFailed {
			continue
		}
		// TODO: Use ImportTaskInfo directly.
		it := &datapb.ImportTask{
			CollectionId: task.GetCollectionId(),
			PartitionId:  task.GetPartitionId(),
			ChannelNames: task.GetChannelNames(),
			RowBased:     task.GetRowBased(),
			TaskId:       task.GetId(),
			Files:        task.GetFiles(),
			Infos: []*commonpb.KeyValuePair{
				{
					Key:   Bucket,
					Value: task.GetBucket(),
				},
			},
		}

		log.Debug("sending import task to DataCoord", zap.Int64("taskID", task.GetId()))
		// Get all busy dataNodes for reference.
		var busyNodeList []int64
		for k := range m.busyNodes {
			busyNodeList = append(busyNodeList, k)
		}

		// Call DataCoord.Import().
		resp := m.callImportService(ctx, &datapb.ImportTaskRequest{
			ImportTask:   it,
			WorkingNodes: busyNodeList,
		})
		if resp.Status.ErrorCode == commonpb.ErrorCode_UnexpectedError {
			log.Debug("import task is rejected", zap.Int64("task ID", it.GetTaskId()))
			break
		}
		task.DatanodeId = resp.GetDatanodeId()
		log.Debug("import task successfully assigned to DataNode",
			zap.Int64("task ID", it.GetTaskId()),
			zap.Int64("dataNode ID", task.GetDatanodeId()))
		// Add new working dataNode to busyNodes.
		m.busyNodes[resp.GetDatanodeId()] = true

		// erase this task from head of pending list if the callImportService succeed
		m.pendingTasks = m.pendingTasks[1:]

		func() {
			m.workingLock.Lock()
			defer m.workingLock.Unlock()

			log.Debug("import task added as working task", zap.Int64("task ID", it.TaskId))
			task.State.StateCode = commonpb.ImportState_ImportPending
			m.workingTasks[task.GetId()] = task
			m.updateImportTaskStore(task)
		}()
	}

	return nil
}

// genReqID generates a unique id for import request, this method has no lock, should only be called by importJob()
func (m *importManager) genReqID() int64 {
	if m.lastReqID == 0 {
		m.lastReqID = time.Now().Unix()

	} else {
		id := time.Now().Unix()
		if id == m.lastReqID {
			id++
		}
		m.lastReqID = id
	}

	return m.lastReqID
}

// importJob processes the import request, generates import tasks, sends these tasks to DataCoord, and returns
// immediately.
func (m *importManager) importJob(ctx context.Context, req *milvuspb.ImportRequest, cID int64, pID int64) *milvuspb.ImportResponse {
	if req == nil || len(req.Files) == 0 {
		return &milvuspb.ImportResponse{
			Status: &commonpb.Status{
				ErrorCode: commonpb.ErrorCode_UnexpectedError,
				Reason:    "import request is empty",
			},
		}
	}

	if m.callImportService == nil {
		return &milvuspb.ImportResponse{
			Status: &commonpb.Status{
				ErrorCode: commonpb.ErrorCode_UnexpectedError,
				Reason:    "import service is not available",
			},
		}
	}

	resp := &milvuspb.ImportResponse{
		Status: &commonpb.Status{
			ErrorCode: commonpb.ErrorCode_Success,
		},
		Tasks: make([]int64, 0),
	}

	log.Debug("request received",
		zap.String("collection name", req.GetCollectionName()),
		zap.Int64("collection ID", cID),
		zap.Int64("partition ID", pID))
	func() {
		m.pendingLock.Lock()
		defer m.pendingLock.Unlock()

		capacity := cap(m.pendingTasks)
		length := len(m.pendingTasks)

		taskCount := 1
		if req.RowBased {
			taskCount = len(req.Files)
		}

		// task queue size has a limit, return error if import request contains too many data files
		if capacity-length < taskCount {
			resp.Status = &commonpb.Status{
				ErrorCode: commonpb.ErrorCode_IllegalArgument,
				Reason:    "Import task queue max size is " + strconv.Itoa(capacity) + ", currently there are " + strconv.Itoa(length) + " tasks is pending. Not able to execute this request with " + strconv.Itoa(taskCount) + " tasks.",
			}
			return
		}

		bucket := ""
		for _, kv := range req.Options {
			if kv.Key == Bucket {
				bucket = kv.Value
				break
			}
		}

		reqID := m.genReqID()
		// convert import request to import tasks
		if req.RowBased {
			// For row-based importing, each file makes a task.
			taskList := make([]int64, len(req.Files))
			for i := 0; i < len(req.Files); i++ {
				newTask := &datapb.ImportTaskInfo{
					Id:           m.nextTaskID,
					RequestId:    reqID,
					CollectionId: cID,
					PartitionId:  pID,
					ChannelNames: req.ChannelNames,
					Bucket:       bucket,
					RowBased:     req.GetRowBased(),
					Files:        []string{req.GetFiles()[i]},
					CreateTs:     time.Now().Unix(),
					State: &datapb.ImportTaskState{
						StateCode: commonpb.ImportState_ImportPending,
					},
				}
				resp.Tasks = append(resp.Tasks, newTask.GetId())
				taskList[i] = newTask.GetId()
				m.nextTaskID++
				log.Info("new task created as pending task", zap.Int64("task ID", newTask.GetId()))
				m.pendingTasks = append(m.pendingTasks, newTask)
				m.storeImportTask(newTask)
			}
			log.Info("row-based import request processed", zap.Int64("reqID", reqID), zap.Any("taskIDs", taskList))
		} else {
			// TODO: Merge duplicated code :(
			// for column-based, all files is a task
			newTask := &datapb.ImportTaskInfo{
				Id:           m.nextTaskID,
				RequestId:    reqID,
				CollectionId: cID,
				PartitionId:  pID,
				ChannelNames: req.ChannelNames,
				Bucket:       bucket,
				RowBased:     req.GetRowBased(),
				Files:        req.GetFiles(),
				CreateTs:     time.Now().Unix(),
				State: &datapb.ImportTaskState{
					StateCode: commonpb.ImportState_ImportPending,
				},
			}
			resp.Tasks = append(resp.Tasks, newTask.GetId())
			m.nextTaskID++
			log.Info("new task created as pending task", zap.Int64("task ID", newTask.GetId()))
			m.pendingTasks = append(m.pendingTasks, newTask)
			m.storeImportTask(newTask)
			log.Info("column-based import request processed", zap.Int64("reqID", reqID), zap.Int64("taskID", newTask.GetId()))
		}
	}()
	m.sendOutTasks(ctx)
	return resp
}

// updateTaskState updates the task's state in in-memory working tasks list and in task store, given ImportResult
// result. It returns the ImportTaskInfo of the given task.
func (m *importManager) updateTaskState(ir *rootcoordpb.ImportResult) (*datapb.ImportTaskInfo, error) {
	if ir == nil {
		return nil, errors.New("import result is nil")
	}
	log.Debug("import manager update task import result", zap.Int64("taskID", ir.GetTaskId()))

	found := false
	var v *datapb.ImportTaskInfo
	m.workingLock.Lock()
	defer m.workingLock.Unlock()
	ok := false
	if v, ok = m.workingTasks[ir.TaskId]; ok {
		// If the task has already been marked failed. Prevent further state updating and return an error.
		if v.GetState().GetStateCode() == commonpb.ImportState_ImportFailed {
			log.Warn("trying to update an already failed task which will end up being a no-op")
			return nil, errors.New("trying to update an already failed task " + strconv.FormatInt(ir.GetTaskId(), 10))
		}
		found = true
		v.State.StateCode = ir.GetState()
		v.State.Segments = ir.GetSegments()
		v.State.RowCount = ir.GetRowCount()
		for _, kv := range ir.GetInfos() {
			if kv.GetKey() == FailedReason {
				v.State.ErrorMessage = kv.GetValue()
				break
			}
		}
		// Update task in task store.
		m.updateImportTaskStore(v)
	}
	m.updateImportTaskStore(v)

	if !found {
		log.Debug("import manager update task import result failed", zap.Int64("taskID", ir.GetTaskId()))
		return nil, errors.New("failed to update import task, ID not found: " + strconv.FormatInt(ir.TaskId, 10))
	}
	return v, nil
}

// getTaskState looks for task with the given ID and returns its import state.
func (m *importManager) getTaskState(tID int64) *milvuspb.GetImportStateResponse {
	resp := &milvuspb.GetImportStateResponse{
		Status: &commonpb.Status{
			ErrorCode: commonpb.ErrorCode_UnexpectedError,
			Reason:    "import task id doesn't exist",
		},
		Infos: make([]*commonpb.KeyValuePair, 0),
	}

	log.Debug("getting import task state", zap.Int64("taskID", tID))
	found := false
	func() {
		m.pendingLock.Lock()
		defer m.pendingLock.Unlock()
		for i := 0; i < len(m.pendingTasks); i++ {
			if tID == m.pendingTasks[i].Id {
				resp.Status = &commonpb.Status{
					ErrorCode: commonpb.ErrorCode_Success,
				}
				resp.State = commonpb.ImportState_ImportPending
				resp.Infos = append(resp.Infos, &commonpb.KeyValuePair{Key: Files, Value: strings.Join(m.pendingTasks[i].GetFiles(), ",")})
				found = true
				break
			}
		}
	}()
	if found {
		return resp
	}

	func() {
		m.workingLock.Lock()
		defer m.workingLock.Unlock()
		if v, ok := m.workingTasks[tID]; ok {
			found = true
			resp.Status = &commonpb.Status{
				ErrorCode: commonpb.ErrorCode_Success,
			}
			resp.State = v.GetState().GetStateCode()
			resp.RowCount = v.GetState().GetRowCount()
			resp.IdList = v.GetState().GetRowIds()
			resp.Infos = append(resp.Infos, &commonpb.KeyValuePair{Key: Files, Value: strings.Join(v.GetFiles(), ",")})
			resp.Infos = append(resp.Infos, &commonpb.KeyValuePair{
				Key:   FailedReason,
				Value: v.GetState().GetErrorMessage(),
			})
		}
	}()
	if found {
		return resp
	}
	log.Debug("get import task state failed", zap.Int64("taskID", tID))
	return resp
}

// loadFromTaskStore loads task info from task store when RootCoord (re)starts.
func (m *importManager) loadFromTaskStore() error {
	log.Info("import manager starts loading from Etcd")
	_, v, err := m.taskStore.LoadWithPrefix(Params.RootCoordCfg.ImportTaskSubPath)
	if err != nil {
		log.Error("import manager failed to load from Etcd", zap.Error(err))
		return err
	}
	m.workingLock.Lock()
	defer m.workingLock.Unlock()
	m.pendingLock.Lock()
	defer m.pendingLock.Unlock()
	for i := range v {
		ti := &datapb.ImportTaskInfo{}
		if err := proto.Unmarshal([]byte(v[i]), ti); err != nil {
			log.Error("failed to unmarshal proto", zap.String("taskInfo", v[i]), zap.Error(err))
			// Ignore bad protos.
			continue
		}
		// Put tasks back to pending or working task list, given their import states.
		if ti.GetState().GetStateCode() == commonpb.ImportState_ImportPending {
			log.Info("task has been reloaded as a pending task", zap.Int64("TaskID", ti.GetId()))
			m.pendingTasks = append(m.pendingTasks, ti)
		} else {
			log.Info("task has been reloaded as a working tasks", zap.Int64("TaskID", ti.GetId()))
			m.workingTasks[ti.GetId()] = ti
		}
	}
	return nil
}

// storeImportTask signs a lease and saves import task info into Etcd with this lease.
func (m *importManager) storeImportTask(task *datapb.ImportTaskInfo) error {
	log.Debug("saving import task to Etcd", zap.Int64("task ID", task.GetId()))
	// Sign a lease. Tasks will be stored for at least `ImportTaskRetention` seconds.
	leaseID, err := m.taskStore.Grant(int64(Params.RootCoordCfg.ImportTaskRetention))
	if err != nil {
		log.Error("failed to grant lease from Etcd for data import",
			zap.Int64("task ID", task.GetId()),
			zap.Error(err))
		return err
	}
	log.Debug("lease granted for task", zap.Int64("task ID", task.GetId()))
	var taskInfo []byte
	if taskInfo, err = proto.Marshal(task); err != nil {
		log.Error("failed to marshall task proto", zap.Int64("task ID", task.GetId()), zap.Error(err))
		return err
	} else if err = m.taskStore.SaveWithLease(BuildImportTaskKey(task.GetId()), string(taskInfo), leaseID); err != nil {
		log.Error("failed to save import task info into Etcd",
			zap.Int64("task ID", task.GetId()),
			zap.Error(err))
		return err
	}
	log.Debug("task info successfully saved", zap.Int64("task ID", task.GetId()))
	return nil
}

// updateImportTaskStore updates the task info in Etcd according to task ID. It won't change the lease on the key.
func (m *importManager) updateImportTaskStore(ti *datapb.ImportTaskInfo) error {
	log.Debug("updating import task info in Etcd", zap.Int64("Task ID", ti.GetId()))
	if taskInfo, err := proto.Marshal(ti); err != nil {
		log.Error("failed to marshall task info proto", zap.Int64("Task ID", ti.GetId()), zap.Error(err))
		return err
	} else if err = m.taskStore.SaveWithIgnoreLease(BuildImportTaskKey(ti.GetId()), string(taskInfo)); err != nil {
		log.Error("failed to update import task info info in Etcd", zap.Int64("Task ID", ti.GetId()), zap.Error(err))
		return err
	}
	log.Debug("task info successfully updated in Etcd", zap.Int64("Task ID", ti.GetId()))
	return nil
}

// expireOldTasksLoop starts a loop that checks and expires old tasks every `ImportTaskExpiration` seconds.
func (m *importManager) expireOldTasksLoop(wg *sync.WaitGroup) {
	defer wg.Done()
	ticker := time.NewTicker(time.Duration(Params.RootCoordCfg.ImportTaskExpiration*1000) * time.Millisecond)
	defer ticker.Stop()
	for {
		select {
		case <-m.ctx.Done():
			log.Info("(in loop) import manager context done, exit expireOldTasksLoop")
			return
		case <-ticker.C:
			log.Info("(in loop) starting expiring old tasks...",
				zap.Duration("cleaning up interval",
					time.Duration(Params.RootCoordCfg.ImportTaskExpiration*1000)*time.Millisecond))
			m.expireOldTasks()
		}
	}
}

// expireOldTasks marks expires tasks as failed.
func (m *importManager) expireOldTasks() {
	// Expire old pending tasks, if any.
	func() {
		m.pendingLock.Lock()
		defer m.pendingLock.Unlock()
		for _, t := range m.pendingTasks {
			if taskExpired(t) {
				log.Info("a pending task has expired", zap.Int64("task ID", t.GetId()))
				t.State.StateCode = commonpb.ImportState_ImportFailed
				t.State.ErrorMessage = taskExpiredMsgPrefix +
					(time.Duration(Params.RootCoordCfg.ImportTaskExpiration*1000) * time.Millisecond).String()
				m.updateImportTaskStore(t)
			}
		}
	}()
	// Expire old working tasks.
	func() {
		m.workingLock.Lock()
		defer m.workingLock.Unlock()
		for _, v := range m.workingTasks {
			// Mark this expired task as failed.
			if taskExpired(v) {
				log.Info("a working task has expired", zap.Int64("task ID", v.GetId()))
				v.State.StateCode = commonpb.ImportState_ImportFailed
				v.State.ErrorMessage = taskExpiredMsgPrefix +
					(time.Duration(Params.RootCoordCfg.ImportTaskExpiration*1000) * time.Millisecond).String()
				m.updateImportTaskStore(v)
			}
		}
	}()
}

// BuildImportTaskKey constructs and returns an Etcd key with given task ID.
func BuildImportTaskKey(taskID int64) string {
	return fmt.Sprintf("%s%s%d", Params.RootCoordCfg.ImportTaskSubPath, delimiter, taskID)
}

// taskExpired returns true if the task has already expired.
func taskExpired(ti *datapb.ImportTaskInfo) bool {
	return Params.RootCoordCfg.ImportTaskExpiration <= float64(time.Now().Unix()-ti.GetCreateTs())
}