package localserver

import (
	"encoding/binary"
	"encoding/json"
	"os"
	"path/filepath"
	"sync"

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

type NodeChatDBHandler struct {
	ChatID     string
	PreviousId uint64
	ItemCount  uint64
	db         func(func(*badger.DB) (err error)) (err error)
	lock       *sync.RWMutex
}

func NewNodeChatDBHandler(chatID string) (nodeChatDBHandler *NodeChatDBHandler, err error) {
	nodeChatDBHandler = &NodeChatDBHandler{
		db: func(f func(*badger.DB) (err error)) (err error) {
			db, err := badger.Open(badger.DefaultOptions(filepath.Join(dataPath, "data", "chats", chatID, "messages")).WithLogger(dbLogger))
			if err != nil {
				return
			}
			defer db.Close()
			err = f(db)
			return
		},
		ChatID: chatID,
		lock:   new(sync.RWMutex),
	}
	err = nodeChatDBHandler.db(func(d *badger.DB) (err error) {
		err = d.View(func(txn *badger.Txn) error {
			opt := badger.DefaultIteratorOptions
			it := txn.NewIterator(opt)
			defer it.Close()
			var counter uint64 = 1
			var itemCounter uint64 = 0
			for it.Rewind(); it.Valid(); it.Next() {
				item := it.Item()
				if err = item.Value(func(val []byte) (err error) {
					var chatMessage *ChatMessage
					if err = json.Unmarshal(val, &chatMessage); err != nil {
						return err
					}
					counter = chatMessage.ID
					itemCounter++
					return
				}); err != nil {
					return err
				}
			}
			nodeChatDBHandler.PreviousId = counter
			nodeChatDBHandler.ItemCount = itemCounter
			return nil
		})
		return
	})
	return
}

func (ncdbh *NodeChatDBHandler) calculateNewChatCount(previousId uint64) (count uint, err error) {
	err = ncdbh.db(func(d *badger.DB) (err error) {
		err = d.View(func(txn *badger.Txn) error {
			opt := badger.DefaultIteratorOptions
			it := txn.NewIterator(opt)
			defer it.Close()
			count = 0
			b := make([]byte, bufferSize)
			binary.BigEndian.PutUint64(b, previousId)
			if previousId == 0 || previousId == 1 {
				count++
				for it.Rewind(); it.Valid(); it.Next() {
					count++
				}
			} else {
				for it.Seek(b); it.Valid(); it.Next() {
					count++
				}
			}
			if count > 0 {
				count--
			}
			return nil
		})
		return
	})
	return
}

func (ncdbh *NodeChatDBHandler) revertPreviousId() (err error) {
	err = ncdbh.db(func(d *badger.DB) (err error) {
		err = d.View(func(txn *badger.Txn) error {
			opt := badger.DefaultIteratorOptions
			opt.Reverse = true
			it := txn.NewIterator(opt)
			defer it.Close()
			it.Rewind()
			if it.Valid() {
				item := it.Item()
				if err = item.Value(func(val []byte) (err error) {
					var chatMessage *ChatMessage
					if err = json.Unmarshal(val, &chatMessage); err != nil {
						return err
					}
					ncdbh.PreviousId = chatMessage.ID
					return
				}); err != nil {
					return err
				}
			} else {
				ncdbh.PreviousId = 1
			}
			return nil
		})
		return
	})
	return
}

func (ncdbh *NodeChatDBHandler) AddNewChatMessage(chatMessage *ChatMessage) (err error) {
	b := make([]byte, bufferSize)
	ncdbh.PreviousId++
	binary.BigEndian.PutUint64(b, ncdbh.PreviousId)
	chatMessage.ID = ncdbh.PreviousId
	bs, err := json.Marshal(chatMessage)
	if err != nil {
		return
	}
	if err = ncdbh.db(func(d *badger.DB) (err error) {
		err = d.Update(func(txn *badger.Txn) (err error) {
			if updateErr := txn.Set(b, bs); updateErr != nil {
				return updateErr
			}
			return nil
		})
		return
	}); err != nil {
		return
	}
	return
}

func (ncdbh *NodeChatDBHandler) DeleteChatMessage(key uint64) (err error) {
	if err = ncdbh.db(func(d *badger.DB) (err error) {
		err = d.Update(func(txn *badger.Txn) (err error) {
			b := make([]byte, bufferSize)
			binary.BigEndian.PutUint64(b, key)
			if err = txn.Delete(b); err != nil {
				return
			}
			ncdbh.ItemCount--
			return
		})
		return
	}); err != nil {
		return
	}
	return
}

func (ncdbh *NodeChatDBHandler) DeleteChatFile(filename string, key uint64) (err error) {
	if err = ncdbh.DeleteChatMessage(key); err != nil {
		return
	}
	err = os.Remove(filepath.Join(dataPath, "data", "chats", ncdbh.ChatID, "__files__", filename))
	return
}

func (ncdbh *NodeChatDBHandler) ListChatMessages(lastIndex int, limit int) (chatMessages []*ChatMessage, l int, done bool, err error) {
	err = ncdbh.db(func(d *badger.DB) (err error) {
		err = d.View(func(txn *badger.Txn) (err error) {
			opt := badger.DefaultIteratorOptions
			opt.Reverse = true
			it := txn.NewIterator(opt)
			defer it.Close()
			b := make([]byte, bufferSize)
			if lastIndex <= 0 {
				binary.BigEndian.PutUint64(b, uint64(ncdbh.PreviousId))
			} else {
				binary.BigEndian.PutUint64(b, uint64(lastIndex))
			}
			x := 0
			defer func() {
				if x < limit {
					done = true
				}
			}()
			chatMessages = make([]*ChatMessage, 0)
			for it.Seek(b); it.Valid(); it.Next() {
				if x >= limit {
					break
				}
				item := it.Item()
				if err = item.Value(func(val []byte) (err error) {
					var chatMessage *ChatMessage
					if err = json.Unmarshal(val, &chatMessage); err != nil {
						return err
					}
					l = int(chatMessage.ID)
					chatMessages = append(chatMessages, chatMessage)
					return
				}); err != nil {
					return err
				}
				x++
			}
			return
		})
		return
	})
	return
}

func (ncdbh *NodeChatDBHandler) ListChatFiles(lastIndex int, limit int) (chatMessages []*ChatFile, l int, err error) {
	err = ncdbh.db(func(d *badger.DB) (err error) {
		err = d.View(func(txn *badger.Txn) (err error) {
			opt := badger.DefaultIteratorOptions
			opt.Reverse = true
			it := txn.NewIterator(opt)
			defer it.Close()
			b := make([]byte, bufferSize)
			var li int
			if lastIndex <= 0 {
				binary.BigEndian.PutUint64(b, uint64(ncdbh.PreviousId))
				li = int(ncdbh.PreviousId)
			} else {
				binary.BigEndian.PutUint64(b, uint64(lastIndex))
				li = lastIndex
			}
			x := 0
			y := 0
			defer func() {
				if li > x {
					l = li - x
				} else if li == 0 {
					if ncdbh.PreviousId > uint64(x) {
						l = int(ncdbh.PreviousId) - x
					} else {
						l = 0
					}
				} else {
					l = 0
				}
			}()
			defer it.Close()
			chatMessages = make([]*ChatFile, 0)
			for it.Seek(b); it.Valid(); it.Next() {
				if y >= limit || x >= int(ncdbh.PreviousId) {
					break
				}
				item := it.Item()
				if err = item.Value(func(val []byte) (err error) {
					var chatMessage *ChatMessage
					if err = json.Unmarshal(val, &chatMessage); err != nil {
						return err
					}
					if chatMessage.File != nil {
						chatMessage.File.ID = chatMessage.ID
						chatMessages = append(chatMessages, chatMessage.File)
						l = lastIndex - x
						y++
					}
					return
				}); err != nil {
					return err
				}
				x++
			}
			return
		})
		return
	})
	return
}

func (ncdbh *NodeChatDBHandler) GetChatMessage(index uint64) (chatMessage *ChatMessage, err error) {
	err = ncdbh.db(func(d *badger.DB) (err error) {
		err = d.View(func(txn *badger.Txn) (err error) {
			b := make([]byte, bufferSize)
			binary.BigEndian.PutUint64(b, uint64(index))
			item, err := txn.Get(b)
			if err != nil {
				return
			}
			err = item.Value(func(val []byte) error {
				return json.Unmarshal(val, &chatMessage)
			})
			return
		})
		return
	})
	return
}

func (ncdbh *NodeChatDBHandler) ModifyChatMessage(key uint64, newContent string) (err error) {
	b := make([]byte, bufferSize)
	binary.BigEndian.PutUint64(b, key)
	chatMessage, err := ncdbh.GetChatMessage(key)
	if err != nil {
		return
	}
	chatMessage.Content = newContent
	bs, err := json.Marshal(chatMessage)
	if err != nil {
		return
	}
	if err = ncdbh.db(func(d *badger.DB) (err error) {
		err = d.Update(func(txn *badger.Txn) (err error) {
			if updateErr := txn.Set(b, bs); updateErr != nil {
				return updateErr
			}
			return nil
		})
		return
	}); err != nil {
		return
	}
	return
}