package leveldb

import (
	"bytes"
	"context"
	"fmt"
	"io"
	"os"

	"github.com/syndtr/goleveldb/leveldb"
	leveldb_errors "github.com/syndtr/goleveldb/leveldb/errors"
	"github.com/syndtr/goleveldb/leveldb/filter"
	"github.com/syndtr/goleveldb/leveldb/opt"
	leveldb_util "github.com/syndtr/goleveldb/leveldb/util"

	"github.com/seaweedfs/seaweedfs/weed/filer"
	"github.com/seaweedfs/seaweedfs/weed/glog"
	"github.com/seaweedfs/seaweedfs/weed/pb/filer_pb"
	weed_util "github.com/seaweedfs/seaweedfs/weed/util"
)

const (
	DIR_FILE_SEPARATOR = byte(0x00)
)

var (
	_ = filer.Debuggable(&LevelDBStore{})
)

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

type LevelDBStore struct {
	db *leveldb.DB
}

func (store *LevelDBStore) GetName() string {
	return "leveldb"
}

func (store *LevelDBStore) Initialize(configuration weed_util.Configuration, prefix string) (err error) {
	dir := configuration.GetString(prefix + "dir")
	return store.initialize(dir)
}

func (store *LevelDBStore) initialize(dir string) (err error) {
	glog.V(0).Infof("filer store dir: %s", dir)
	os.MkdirAll(dir, 0755)
	if err := weed_util.TestFolderWritable(dir); err != nil {
		return fmt.Errorf("Check Level Folder %s Writable: %s", dir, err)
	}

	opts := &opt.Options{
		BlockCacheCapacity: 32 * 1024 * 1024,         // default value is 8MiB
		WriteBuffer:        16 * 1024 * 1024,         // default value is 4MiB
		Filter:             filter.NewBloomFilter(8), // false positive rate 0.02
	}

	if store.db, err = leveldb.OpenFile(dir, opts); err != nil {
		if leveldb_errors.IsCorrupted(err) {
			store.db, err = leveldb.RecoverFile(dir, opts)
		}
		if err != nil {
			glog.Infof("filer store open dir %s: %v", dir, err)
			return
		}
	}
	return
}

func (store *LevelDBStore) BeginTransaction(ctx context.Context) (context.Context, error) {
	return ctx, nil
}
func (store *LevelDBStore) CommitTransaction(ctx context.Context) error {
	return nil
}
func (store *LevelDBStore) RollbackTransaction(ctx context.Context) error {
	return nil
}

func (store *LevelDBStore) InsertEntry(ctx context.Context, entry *filer.Entry) (err error) {
	key := genKey(entry.DirAndName())

	value, err := entry.EncodeAttributesAndChunks()
	if err != nil {
		return fmt.Errorf("encoding %s %+v: %v", entry.FullPath, entry.Attr, err)
	}

	if len(entry.GetChunks()) > filer.CountEntryChunksForGzip {
		value = weed_util.MaybeGzipData(value)
	}

	err = store.db.Put(key, value, nil)

	if err != nil {
		return fmt.Errorf("persisting %s : %v", entry.FullPath, err)
	}

	// println("saved", entry.FullPath, "chunks", len(entry.GetChunks()))

	return nil
}

func (store *LevelDBStore) UpdateEntry(ctx context.Context, entry *filer.Entry) (err error) {

	return store.InsertEntry(ctx, entry)
}

// BatchInsertEntries inserts multiple entries in a single LevelDB batch write.
// This is more efficient than inserting entries one by one as it reduces
// the number of write operations and syncs to disk.
func (store *LevelDBStore) BatchInsertEntries(ctx context.Context, entries []*filer.Entry) error {
	if len(entries) == 0 {
		return nil
	}

	batch := new(leveldb.Batch)

	for _, entry := range entries {
		key := genKey(entry.DirAndName())

		value, err := entry.EncodeAttributesAndChunks()
		if err != nil {
			return fmt.Errorf("encoding %s %+v: %w", entry.FullPath, entry.Attr, err)
		}

		if len(entry.GetChunks()) > filer.CountEntryChunksForGzip {
			value = weed_util.MaybeGzipData(value)
		}

		batch.Put(key, value)
	}

	err := store.db.Write(batch, nil)
	if err != nil {
		return fmt.Errorf("batch write: %w", err)
	}

	return nil
}

func (store *LevelDBStore) FindEntry(ctx context.Context, fullpath weed_util.FullPath) (entry *filer.Entry, err error) {
	key := genKey(fullpath.DirAndName())

	data, err := store.db.Get(key, nil)

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

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

	// println("read", entry.FullPath, "chunks", len(entry.GetChunks()), "data", len(data), string(data))

	return entry, nil
}

func (store *LevelDBStore) DeleteEntry(ctx context.Context, fullpath weed_util.FullPath) (err error) {
	key := genKey(fullpath.DirAndName())

	err = store.db.Delete(key, nil)
	if err != nil {
		return fmt.Errorf("delete %s : %v", fullpath, err)
	}

	return nil
}

func (store *LevelDBStore) DeleteFolderChildren(ctx context.Context, fullpath weed_util.FullPath) (err error) {

	batch := new(leveldb.Batch)

	directoryPrefix := genDirectoryKeyPrefix(fullpath, "")
	iter := store.db.NewIterator(&leveldb_util.Range{Start: directoryPrefix}, nil)
	for iter.Next() {
		key := iter.Key()
		if !bytes.HasPrefix(key, directoryPrefix) {
			break
		}
		fileName := getNameFromKey(key)
		if fileName == "" {
			continue
		}
		batch.Delete([]byte(genKey(string(fullpath), fileName)))
	}
	iter.Release()

	err = store.db.Write(batch, nil)

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

	return nil
}

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

func (store *LevelDBStore) ListDirectoryPrefixedEntries(ctx context.Context, dirPath weed_util.FullPath, startFileName string, includeStartFile bool, limit int64, prefix string, eachEntryFunc filer.ListEachEntryFunc) (lastFileName string, err error) {

	directoryPrefix := genDirectoryKeyPrefix(dirPath, prefix)
	lastFileStart := directoryPrefix
	if startFileName != "" {
		lastFileStart = genDirectoryKeyPrefix(dirPath, startFileName)
	}

	iter := store.db.NewIterator(&leveldb_util.Range{Start: lastFileStart}, nil)
	for iter.Next() {
		key := iter.Key()
		if !bytes.HasPrefix(key, directoryPrefix) {
			break
		}
		fileName := getNameFromKey(key)
		if fileName == "" {
			continue
		}
		if fileName == startFileName && !includeStartFile {
			continue
		}
		limit--
		if limit < 0 {
			break
		}
		lastFileName = fileName
		entry := &filer.Entry{
			FullPath: weed_util.NewFullPath(string(dirPath), fileName),
		}
		if decodeErr := entry.DecodeAttributesAndChunks(weed_util.MaybeDecompressData(iter.Value())); decodeErr != nil {
			err = decodeErr
			glog.V(0).InfofCtx(ctx, "list %s : %v", entry.FullPath, err)
			break
		}

		resEachEntryFunc, resEachEntryFuncErr := eachEntryFunc(entry)
		if resEachEntryFuncErr != nil {
			err = fmt.Errorf("failed to process eachEntryFunc: %w", resEachEntryFuncErr)
			break
		}

		if !resEachEntryFunc {
			break
		}
	}
	iter.Release()

	return lastFileName, err
}

func genKey(dirPath, fileName string) (key []byte) {
	key = []byte(dirPath)
	key = append(key, DIR_FILE_SEPARATOR)
	key = append(key, []byte(fileName)...)
	return key
}

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

func getNameFromKey(key []byte) string {

	sepIndex := len(key) - 1
	for sepIndex >= 0 && key[sepIndex] != DIR_FILE_SEPARATOR {
		sepIndex--
	}

	return string(key[sepIndex+1:])

}

func (store *LevelDBStore) Shutdown() {
	store.db.Close()
}

func (store *LevelDBStore) Debug(writer io.Writer) {
	iter := store.db.NewIterator(&leveldb_util.Range{}, nil)
	for iter.Next() {
		key := iter.Key()
		fullName := bytes.Replace(key, []byte{DIR_FILE_SEPARATOR}, []byte{' '}, 1)
		fmt.Fprintf(writer, "%v\n", string(fullName))
	}
	iter.Release()
}
