package tikv

import (
	"bytes"
	"context"
	"crypto/sha1"
	"fmt"
	"io"
	"strings"

	"github.com/chrislusf/seaweedfs/weed/filer"
	"github.com/chrislusf/seaweedfs/weed/glog"
	"github.com/chrislusf/seaweedfs/weed/pb/filer_pb"
	"github.com/chrislusf/seaweedfs/weed/util"
	"github.com/tikv/client-go/v2/tikv"
	"github.com/tikv/client-go/v2/txnkv"
)

func init() {
	filer.Stores = append(filer.Stores, &TikvStore{})
}

type TikvStore struct {
	client *tikv.KVStore
}

// Basic APIs
func (store *TikvStore) GetName() string {
	return "tikv"
}

func (store *TikvStore) Initialize(config util.Configuration, prefix string) error {
	pdAddrs := []string{}
	pdAddrsStr := config.GetString(prefix + "pdaddrs")
	for _, item := range strings.Split(pdAddrsStr, ",") {
		pdAddrs = append(pdAddrs, strings.TrimSpace(item))
	}
	return store.initialize(pdAddrs)
}

func (store *TikvStore) initialize(pdAddrs []string) error {
	client, err := tikv.NewTxnClient(pdAddrs)
	store.client = client
	return err
}

func (store *TikvStore) Shutdown() {
	err := store.client.Close()
	if err != nil {
		glog.V(0).Infof("Shutdown TiKV client got error: %v", err)
	}
}

// ~ Basic APIs

// Entry APIs
func (store *TikvStore) InsertEntry(ctx context.Context, entry *filer.Entry) error {
	dir, name := entry.DirAndName()
	key := generateKey(dir, name)

	value, err := entry.EncodeAttributesAndChunks()
	if err != nil {
		return fmt.Errorf("encoding %s %+v: %v", entry.FullPath, entry.Attr, err)
	}
	txn, err := store.getTxn(ctx)
	if err != nil {
		return err
	}
	err = txn.RunInTxn(func(txn *txnkv.KVTxn) error {
		return txn.Set(key, value)
	})
	if err != nil {
		return fmt.Errorf("persisting %s : %v", entry.FullPath, err)
	}
	return nil
}

func (store *TikvStore) UpdateEntry(ctx context.Context, entry *filer.Entry) error {
	return store.InsertEntry(ctx, entry)
}

func (store *TikvStore) FindEntry(ctx context.Context, path util.FullPath) (*filer.Entry, error) {
	dir, name := path.DirAndName()
	key := generateKey(dir, name)

	txn, err := store.getTxn(ctx)
	if err != nil {
		return nil, err
	}
	var value []byte = nil
	err = txn.RunInTxn(func(txn *txnkv.KVTxn) error {
		val, err := txn.Get(context.TODO(), key)
		if err == nil {
			value = val
		}
		return err
	})

	if isNotExists(err) || value == nil {
		return nil, filer_pb.ErrNotFound
	}

	if err != nil {
		return nil, fmt.Errorf("get %s : %v", path, err)
	}

	entry := &filer.Entry{
		FullPath: path,
	}
	err = entry.DecodeAttributesAndChunks(value)
	if err != nil {
		return entry, fmt.Errorf("decode %s : %v", entry.FullPath, err)
	}
	return entry, nil
}

func (store *TikvStore) DeleteEntry(ctx context.Context, path util.FullPath) error {
	dir, name := path.DirAndName()
	key := generateKey(dir, name)

	txn, err := store.getTxn(ctx)
	if err != nil {
		return err
	}

	err = txn.RunInTxn(func(txn *txnkv.KVTxn) error {
		return txn.Delete(key)
	})
	if err != nil {
		return fmt.Errorf("delete %s : %v", path, err)
	}
	return nil
}

// ~ Entry APIs

// Directory APIs
func (store *TikvStore) DeleteFolderChildren(ctx context.Context, path util.FullPath) error {
	directoryPrefix := genDirectoryKeyPrefix(path, "")

	txn, err := store.getTxn(ctx)
	if err != nil {
		return err
	}

	err = txn.RunInTxn(func(txn *txnkv.KVTxn) error {
		iter, err := txn.Iter(directoryPrefix, nil)
		if err != nil {
			return err
		}
		defer iter.Close()
		for iter.Valid() {
			key := iter.Key()
			if !bytes.HasPrefix(key, directoryPrefix) {
				break
			}
			err = txn.Delete(key)
			if err != nil {
				return err
			}
			err = iter.Next()
			if err != nil {
				return err
			}
		}
		return nil
	})
	if err != nil {
		return fmt.Errorf("delete %s : %v", path, err)
	}
	return nil
}

func (store *TikvStore) ListDirectoryEntries(ctx context.Context, dirPath util.FullPath, startFileName string, includeStartFile bool, limit int64, eachEntryFunc filer.ListEachEntryFunc) (string, error) {
	return store.ListDirectoryPrefixedEntries(ctx, dirPath, startFileName, includeStartFile, limit, "", eachEntryFunc)
}

func (store *TikvStore) ListDirectoryPrefixedEntries(ctx context.Context, dirPath util.FullPath, startFileName string, includeStartFile bool, limit int64, prefix string, eachEntryFunc filer.ListEachEntryFunc) (string, error) {
	lastFileName := ""
	directoryPrefix := genDirectoryKeyPrefix(dirPath, prefix)
	lastFileStart := directoryPrefix
	if startFileName != "" {
		lastFileStart = genDirectoryKeyPrefix(dirPath, startFileName)
	}

	txn, err := store.getTxn(ctx)
	if err != nil {
		return lastFileName, err
	}
	err = txn.RunInTxn(func(txn *txnkv.KVTxn) error {
		iter, err := txn.Iter(lastFileStart, nil)
		if err != nil {
			return err
		}
		defer iter.Close()
		i := int64(0)
		first := true
		for iter.Valid() {
			if first {
				first = false
				if !includeStartFile {
					if iter.Valid() {
						// Check first item is lastFileStart
						if bytes.Equal(iter.Key(), lastFileStart) {
							// Is lastFileStart and not include start file, just
							// ignore it.
							err = iter.Next()
							if err != nil {
								return err
							}
							continue
						}
					}
				}
			}
			// Check for limitation
			if limit > 0 {
				i++
				if i > limit {
					break
				}
			}
			// Validate key prefix
			key := iter.Key()
			if !bytes.HasPrefix(key, directoryPrefix) {
				break
			}
			value := iter.Value()

			// Start process
			fileName := getNameFromKey(key)
			if fileName != "" {
				// Got file name, then generate the Entry
				entry := &filer.Entry{
					FullPath: util.NewFullPath(string(dirPath), fileName),
				}
				// Update lastFileName
				lastFileName = fileName
				// Check for decode value.
				if decodeErr := entry.DecodeAttributesAndChunks(value); decodeErr != nil {
					// Got error just return the error
					glog.V(0).Infof("list %s : %v", entry.FullPath, err)
					return err
				}
				// Run for each callback if return false just break the iteration
				if !eachEntryFunc(entry) {
					break
				}
			}
			// End process

			err = iter.Next()
			if err != nil {
				return err
			}
		}
		return nil
	})
	if err != nil {
		return lastFileName, fmt.Errorf("prefix list %s : %v", dirPath, err)
	}
	return lastFileName, nil
}

// ~ Directory APIs

// Transaction Related APIs
func (store *TikvStore) BeginTransaction(ctx context.Context) (context.Context, error) {
	tx, err := store.client.Begin()
	if err != nil {
		return ctx, err
	}
	return context.WithValue(ctx, "tx", tx), nil
}

func (store *TikvStore) CommitTransaction(ctx context.Context) error {
	if tx, ok := ctx.Value("tx").(*txnkv.KVTxn); ok {
		return tx.Commit(context.Background())
	}
	return nil
}

func (store *TikvStore) RollbackTransaction(ctx context.Context) error {
	if tx, ok := ctx.Value("tx").(*txnkv.KVTxn); ok {
		return tx.Rollback()
	}
	return nil
}

// ~ Transaction Related APIs

// Transaction Wrapper
type TxnWrapper struct {
	*txnkv.KVTxn
	inContext bool
}

func (w *TxnWrapper) RunInTxn(f func(txn *txnkv.KVTxn) error) error {
	err := f(w.KVTxn)
	if !w.inContext {
		if err != nil {
			w.KVTxn.Rollback()
			return err
		}
		w.KVTxn.Commit(context.Background())
		return nil
	}
	return err
}

func (store *TikvStore) getTxn(ctx context.Context) (*TxnWrapper, error) {
	if tx, ok := ctx.Value("tx").(*txnkv.KVTxn); ok {
		return &TxnWrapper{tx, true}, nil
	}
	txn, err := store.client.Begin()
	if err != nil {
		return nil, err
	}
	return &TxnWrapper{txn, false}, nil
}

// ~ Transaction Wrapper

// Encoding Functions
func hashToBytes(dir string) []byte {
	h := sha1.New()
	io.WriteString(h, dir)
	b := h.Sum(nil)
	return b
}

func generateKey(dirPath, fileName string) []byte {
	key := hashToBytes(dirPath)
	key = append(key, []byte(fileName)...)
	return key
}

func getNameFromKey(key []byte) string {
	return string(key[sha1.Size:])
}

func genDirectoryKeyPrefix(fullpath util.FullPath, startFileName string) (keyPrefix []byte) {
	keyPrefix = hashToBytes(string(fullpath))
	if len(startFileName) > 0 {
		keyPrefix = append(keyPrefix, []byte(startFileName)...)
	}
	return keyPrefix
}

func isNotExists(err error) bool {
	if err == nil {
		return false
	}
	if err.Error() == "not exist" {
		return true
	}
	return false
}

// ~ Encoding Functions