package fusenrender

import (
	"encoding/binary"
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"time"

	"github.com/dgraph-io/badger/v3"
	sm "github.com/lni/dragonboat/v4/statemachine"
)

type SMQueue struct {
	Count uint64
	db    *badger.DB
}

type Command struct {
	Name string `json:"name"`

	Group *string    `json:"group"`
	Item  *QueueItem `json:"item"`
}

type QueueItem struct {
	Group    string    `json:"group"`     // 组名
	Priority uint32    `json:"priority"`  // 处理的优先级
	CreateAt time.Time `json:"create_at"` // 创建时间 统一utc
	Data     any       `json:"data"`      // 操作的数据结构
}

func (item *QueueItem) Encode() ([]byte, error) {
	val, err := json.Marshal(item)
	if err != nil {
		return nil, err
	}
	return val, nil
}

// NewSMQueue creates and return a new ExampleStateMachine object.
func NewSMQueue(datapath string) sm.IStateMachine {
	opts := badger.DefaultOptions(datapath)
	db, err := badger.Open(opts)
	if err != nil {
		panic(err)
	}

	return &SMQueue{
		db: db,
	}
}

// Lookup performs local lookup on the ExampleStateMachine instance. In this example,
// we always return the Count value as a little endian binary encoded byte
// slice.
func (s *SMQueue) Lookup(group interface{}) (item interface{}, err error) {

	prefix := []byte(fmt.Sprintf("%s_", group.(string)))
	err = s.db.Update(func(txn *badger.Txn) error {

		it := txn.NewIterator(badger.DefaultIteratorOptions)
		defer it.Close()

		it.Seek(prefix)
		if !it.ValidForPrefix(prefix) {
			return nil
		}

		itemKey := it.Item().Key()
		err = it.Item().Value(func(val []byte) error {
			item = &QueueItem{}
			return json.Unmarshal(val, item)
		})
		if err != nil {
			log.Println(err)
		}

		return txn.Delete(itemKey)
	})

	return item, nil
}

func (q *SMQueue) GetKey(item *QueueItem) []byte {
	return []byte(fmt.Sprintf("%s_%d_%d", item.Group, -item.Priority, item.CreateAt.UTC().Unix()))
}

// Update updates the object using the specified committed raft entry.
func (s *SMQueue) Update(e sm.Entry) (result sm.Result, err error) {

	var cmd Command

	err = json.Unmarshal(e.Cmd, &cmd)
	if err != nil {
		return result, err
	}

	switch cmd.Name {
	case "enqueue":
		d, err := cmd.Item.Encode()
		if err != nil {
			return result, err
		}

		err = s.db.Update(func(txn *badger.Txn) error {
			return txn.Set([]byte(s.GetKey(cmd.Item)), d)
		})
		return sm.Result{Value: uint64(len(d))}, err
	case "dequeue":

		prefix := []byte(fmt.Sprintf("%s_", *cmd.Group))
		err = s.db.Update(func(txn *badger.Txn) error {

			it := txn.NewIterator(badger.DefaultIteratorOptions)
			defer it.Close()

			it.Seek(prefix)
			if !it.ValidForPrefix(prefix) {
				return nil
			}

			itemKey := it.Item().Key()
			err = it.Item().Value(func(val []byte) error {
				result.Data = val
				return nil
			})
			if err != nil {
				log.Println(err)
			}
			return txn.Delete(itemKey)
		})

		return result, err
	default:
		return result, fmt.Errorf("unknonw cmd type: %s", cmd.Name)
	}

}

// SaveSnapshot saves the current IStateMachine state into a snapshot using the
// specified io.Writer object.
func (s *SMQueue) SaveSnapshot(w io.Writer,
	fc sm.ISnapshotFileCollection, done <-chan struct{}) error {
	// as shown above, the only state that can be saved is the Count variable
	// there is no external file in this IStateMachine example, we thus leave
	// the fc untouched

	// 创建一个只读事务
	txn := s.db.NewTransaction(false)

	// 在事务中读取数据
	iter := txn.NewIterator(badger.IteratorOptions{})

	for iter.Rewind(); iter.Valid(); iter.Next() {
		item := iter.Item()

		err := item.Value(func(val []byte) error {
			_, err := w.Write(val)
			return err
		})
		if err != nil {
			return err
		}

		// 处理key-value
	}

	// 释放迭代器和事务
	iter.Close()
	txn.Discard()

	return nil
}

// RecoverFromSnapshot recovers the state using the provided snapshot.
func (s *SMQueue) RecoverFromSnapshot(r io.Reader,
	files []sm.SnapshotFile,
	done <-chan struct{}) error {
	// restore the Count variable, that is the only state we maintain in this
	// example, the input files is expected to be empty
	data, err := ioutil.ReadAll(r)
	if err != nil {
		return err
	}
	v := binary.LittleEndian.Uint64(data)
	s.Count = v
	return nil
}

// Close closes the IStateMachine instance. There is nothing for us to cleanup
// or release as this is a pure in memory data store. Note that the Close
// method is not guaranteed to be called as node can crash at any time.
func (s *SMQueue) Close() error { return nil }

// import (
// 	"encoding/json"
// 	"fmt"
// 	"io"
// 	"log"
// 	"sync"
// 	"time"

// 	"github.com/dgraph-io/badger/v3"
// 	"github.com/hashicorp/raft"
// )

// type SMQueue struct {
// 	mu    sync.Mutex
// 	queue *Queue
// 	ra    *raft.Raft
// }

// func NewQueueFSM(datapath string) *SMQueue {
// 	q, err := NewQueue(datapath)
// 	if err != nil {
// 		panic(err)
// 	}
// 	return &SMQueue{
// 		queue: q,
// 	}
// }

// const (
// 	Enqueue raft.LogType = 20
// 	Dequeue raft.LogType = 21
// )

// func (q *SMQueue) LogInfo() {
// 	log.Println(q.ra.GetConfiguration().Configuration(), q.ra.State())
// }

// func (q *SMQueue) Put(item *QueueItem) error {
// 	data, err := item.Encode()
// 	if err != nil {
// 		return err
// 	}
// 	return q.PutJsonString(data)
// }

// func (q *SMQueue) PutJsonString(item []byte) error {
// 	task := ApplyTask{
// 		Name:   "enqueue",
// 		Object: item,
// 	}

// 	d, err := task.Encode()
// 	if err != nil {
// 		return err
// 	}

// 	future := q.ra.Apply(d, time.Second*15)

// 	if future.Error() != nil {
// 		return future.Error()
// 	}

// 	resp := future.Response()

// 	if resp == nil {
// 		return nil
// 	}

// 	return resp.(error)
// }

// func (q *SMQueue) Pop(group string) (*QueueItem, error) {
// 	task := ApplyTask{
// 		Name:   "dequeue",
// 		Object: []byte(group),
// 	}

// 	d, err := task.Encode()
// 	if err != nil {
// 		return nil, err
// 	}

// 	ierr := q.ra.Apply(d, time.Second*15)

// 	if ierr.Error() != nil {
// 		return nil, ierr.Error()
// 	}

// 	switch v := ierr.Response().(type) {
// 	case error:
// 		return nil, v
// 	case *QueueItem:
// 		return v, nil
// 	default:
// 		return nil, fmt.Errorf("unknown %v", v)
// 	}
// }

// func (q *SMQueue) Apply(log *raft.Log) interface{} {
// 	leader, id := q.ra.LeaderWithID()

// 	q.mu.Lock()
// 	defer q.mu.Unlock()

// 	var task ApplyTask
// 	err := task.Decode(log.Data)
// 	if err != nil {
// 		return err
// 	}

// 	switch task.Name {
// 	case "enqueue":
// 		var item QueueItem
// 		if err := json.Unmarshal(task.Object, &item); err != nil {
// 			return err
// 		}
// 		return q.queue.Enqueue(&item)
// 	case "dequeue":
// 		// log.Data 传入group
// 		item, err := q.queue.Dequeue(string(task.Object))
// 		if err != nil {
// 			return err
// 		}
// 		return item
// 	default:
// 		return fmt.Errorf("unknown type: %v", log.Type)
// 	}
// }

// type QueueSnapshot struct {
// 	Items []*QueueItem
// }

// // Persist writes the snapshot to the provided sink.
// func (snapshot *QueueSnapshot) Persist(sink raft.SnapshotSink) error {
// 	// The example has been simplified. In a production environment, you would
// 	// need to handle this operation with more care.
// 	return nil
// }

// // Release is invoked when the Raft instance is finished with the snapshot.
// func (snapshot *QueueSnapshot) Release() {
// 	// Normally you would put any cleanup here.
// }

// // Snapshot 返回队列快照
// func (fsm *SMQueue) Snapshot() (raft.FSMSnapshot, error) {

// 	var items []*QueueItem

// 	// 使用 Badger 读取所有队列项
// 	fsm.queue.db.View(func(txn *badger.Txn) error {
// 		opts := badger.DefaultIteratorOptions
// 		opts.PrefetchValues = false // 只需要key

// 		it := txn.NewIterator(opts)
// 		defer it.Close()

// 		for it.Rewind(); it.Valid(); it.Next() {

// 			err := it.Item().Value(func(val []byte) error {
// 				item := &QueueItem{}
// 				err := json.Unmarshal(val, item)
// 				if err != nil {
// 					return err
// 				}
// 				items = append(items, item)
// 				return nil
// 			})
// 			if err != nil {
// 				log.Println(err)
// 			}

// 		}

// 		return nil
// 	})

// 	snapshot := &QueueSnapshot{Items: items}
// 	return snapshot, nil

// }

// // Restore 恢复队列状态
// func (fsm *SMQueue) Restore(rc io.ReadCloser) error {

// 	snapshot := &QueueSnapshot{}
// 	if err := json.NewDecoder(rc).Decode(snapshot); err != nil {
// 		return err
// 	}

// 	// 用快照数据重建队列
// 	fsm.queue.db.Update(func(txn *badger.Txn) error {
// 		for _, item := range snapshot.Items {

// 			val, err := item.Encode()
// 			if err != nil {
// 				log.Println(err)
// 				continue
// 			}

// 			if err := txn.Set(fsm.queue.GetKey(item), val); err != nil {
// 				return err
// 			}
// 		}
// 		return nil
// 	})

// 	return nil
// }

// func waitForCluster(ra *raft.Raft) {
// 	ticker := time.NewTicker(500 * time.Millisecond)
// 	defer ticker.Stop()

// 	for range ticker.C {
// 		state := ra.State()
// 		if state == raft.Leader || state == raft.Follower {
// 			log.Println("Raft cluster is running")
// 			return
// 		} else {
// 			log.Println("Still waiting for the cluster to start...")
// 		}
// 	}
// }