// Copyright 2019 The turbo-geth authors
// This file is part of the turbo-geth library.
//
// The turbo-geth library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The turbo-geth library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the turbo-geth library. If not, see <http://www.gnu.org/licenses/>.

package ethdb

import (
	"bytes"
	"context"
	"os"
	"time"

	"github.com/dgraph-io/badger/v2"
	"github.com/ledgerwatch/turbo-geth/common"
	"github.com/ledgerwatch/turbo-geth/common/dbutils"
	"github.com/ledgerwatch/turbo-geth/log"
)

// https://github.com/dgraph-io/badger#garbage-collection
const gcPeriod = 5 * time.Minute

// BadgerDatabase is a wrapper over BadgerDb,
// compatible with the Database interface.
type BadgerDatabase struct {
	db       *badger.DB   // BadgerDB instance
	log      log.Logger   // Contextual logger tracking the database path
	tmpDir   string       // Temporary data directory
	gcTicker *time.Ticker // Garbage Collector
	id       uint64
}

// NewBadgerDatabase returns a BadgerDB wrapper.
func NewBadgerDatabase(dir string) (*BadgerDatabase, error) {
	logger := log.New("database", dir)

	options := badger.DefaultOptions(dir).WithMaxTableSize(128 << 20) // 128Mb, default 64Mb

	db, err := badger.Open(options)
	if err != nil {
		return nil, err
	}

	// Start GC in background
	ticker := time.NewTicker(gcPeriod)
	go func() {
		// DB.RunValueLogGC(): This method is designed to do garbage collection while Badger is online. Along with randomly picking a file, it uses statistics generated by the LSM-tree compactions to pick files that are likely to lead to maximum space reclamation. It is recommended to be called during periods of low activity in your system, or periodically. One call would only result in removal of at max one log file. As an optimization, you could also immediately re-run it whenever it returns nil error (indicating a successful value log GC), as shown below.
		i := 0
		for range ticker.C {
		nextFile:
			err := db.RunValueLogGC(0.7)
			if err == nil {
				i++
				goto nextFile
			}
			if err != badger.ErrNoRewrite {
				logger.Info("Badger GC happened", "rewritten_vlog_files", i)
				i = 0
				continue
			}
		}
	}()

	return &BadgerDatabase{
		db:       db,
		log:      logger,
		gcTicker: ticker,
		id:       id(),
	}, nil
}

// NewEphemeralBadger returns a new BadgerDB in a temporary directory.
func NewEphemeralBadger() (*BadgerDatabase, error) {
	logger := log.New("db", "badgerInMem")

	db, err := badger.Open(badger.DefaultOptions("").WithInMemory(true))
	if err != nil {
		return nil, err
	}

	return &BadgerDatabase{
		db:  db,
		log: logger,
	}, nil
}

func (db *BadgerDatabase) KV() KV {
	return &badgerKV{badger: db.db}
}

// Close closes the database.
func (db *BadgerDatabase) Close() {
	if db.gcTicker != nil {
		db.gcTicker.Stop()
	}

	if err := db.db.Close(); err == nil {
		db.log.Info("Database closed")
		if len(db.tmpDir) > 0 {
			os.RemoveAll(db.tmpDir)
		}
	} else {
		db.log.Error("Failed to close database", "err", err)
	}
}

func bucketKey(bucket, key []byte) []byte {
	composite := make([]byte, 0, len(bucket)+len(key))
	composite = append(composite, bucket...)
	composite = append(composite, key...)
	return composite
}

func keyWithoutBucket(key, bucket []byte) []byte {
	if len(key) <= len(bucket) || !bytes.HasPrefix(key, bucket) {
		return nil
	}
	return key[len(bucket):]
}

// Delete removes a single entry.
func (db *BadgerDatabase) Delete(bucket, key []byte) error {
	return db.db.Update(func(txn *badger.Txn) error {
		return txn.Delete(bucketKey(bucket, key))
	})
}

// Put inserts or updates a single entry.
func (db *BadgerDatabase) Put(bucket, key []byte, value []byte) error {
	return db.db.Update(func(txn *badger.Txn) error {
		return txn.Set(bucketKey(bucket, key), value)
	})
}

// Get returns the value for a given key if it's present.
func (db *BadgerDatabase) Get(bucket, key []byte) ([]byte, error) {
	var val []byte
	err := db.db.View(func(txn *badger.Txn) error {
		item, err := txn.Get(bucketKey(bucket, key))
		if err != nil {
			return err
		}
		val, err = item.ValueCopy(nil)
		return err
	})
	if err == badger.ErrKeyNotFound {
		return nil, ErrKeyNotFound
	}
	return val, err
}

func (db *BadgerDatabase) GetIndexChunk(bucket, key []byte, timestamp uint64) ([]byte, error) {
	var val []byte
	var innerErr error

	err := db.db.View(func(txn *badger.Txn) error {
		it := txn.NewIterator(badger.DefaultIteratorOptions)
		defer it.Close()
		it.Seek(bucketKey(bucket, dbutils.IndexChunkKey(key, timestamp)))
		if it.ValidForPrefix(bucketKey(bucket, key)) {
			val, innerErr = it.Item().ValueCopy(nil)
			if innerErr != nil {
				return innerErr
			}
			return nil
		}
		return badger.ErrKeyNotFound
	})
	if err == badger.ErrKeyNotFound {
		return nil, ErrKeyNotFound
	}
	return val, err
}

// GetAsOf returns the value valid as of a given timestamp.
func (db *BadgerDatabase) GetAsOf(bucket, hBucket, key []byte, timestamp uint64) ([]byte, error) {
	composite, _ := dbutils.CompositeKeySuffix(key, timestamp)
	var dat []byte
	err := db.db.View(func(tx *badger.Txn) error {
		{ // first look in the historical dbi
			it := tx.NewIterator(badger.DefaultIteratorOptions)
			defer it.Close()
			it.Seek(bucketKey(hBucket, composite))

			if it.ValidForPrefix(bucketKey(hBucket, key)) {
				var err2 error
				dat, err2 = it.Item().ValueCopy(nil)
				return err2
			}
		}

		{ // fall back to the current dbi
			item, err2 := tx.Get(bucketKey(bucket, key))
			if err2 != nil {
				return err2
			}
			dat, err2 = item.ValueCopy(nil)
			return err2
		}
	})

	if err == badger.ErrKeyNotFound {
		return dat, ErrKeyNotFound
	}
	return dat, err
}

// Has indicates whether a key exists in the database.
func (db *BadgerDatabase) Has(bucket, key []byte) (bool, error) {
	_, err := db.Get(bucket, key)
	if err == ErrKeyNotFound {
		return false, nil
	}
	return err == nil, err
}

// Walk iterates over entries with keys greater or equals to startkey.
// Only the keys whose first fixedbits match those of startkey are iterated over.
// walker is called for each eligible entry.
// If walker returns false or an error, the walk stops.
func (db *BadgerDatabase) Walk(bucket, startkey []byte, fixedbits int, walker func(k, v []byte) (bool, error)) error {
	fixedbytes, mask := Bytesmask(fixedbits)
	prefix := bucketKey(bucket, startkey)
	err := db.db.View(func(tx *badger.Txn) error {
		it := tx.NewIterator(badger.DefaultIteratorOptions)
		defer it.Close()
		for it.Seek(prefix); it.Valid(); it.Next() {
			item := it.Item()
			k := keyWithoutBucket(item.Key(), bucket)
			if k == nil {
				break
			}

			goOn := fixedbits == 0 || bytes.Equal(k[:fixedbytes-1], startkey[:fixedbytes-1]) && (k[fixedbytes-1]&mask) == (startkey[fixedbytes-1]&mask)
			if !goOn {
				break
			}

			err := item.Value(func(v []byte) error {
				var err2 error
				goOn, err2 = walker(k, v)
				return err2
			})
			if err != nil {
				return err
			}
			if !goOn {
				break
			}
		}
		return nil
	})
	return err
}

// MultiWalk is similar to multiple Walk calls folded into one.
func (db *BadgerDatabase) MultiWalk(bucket []byte, startkeys [][]byte, fixedbits []int, walker func(int, []byte, []byte) error) error {
	if len(startkeys) == 0 {
		return nil
	}

	rangeIdx := 0 // What is the current range we are extracting
	fixedbytes, mask := Bytesmask(fixedbits[rangeIdx])
	startkey := startkeys[rangeIdx]

	err := db.db.View(func(tx *badger.Txn) error {
		it := tx.NewIterator(badger.DefaultIteratorOptions)
		defer it.Close()
		for it.Seek(bucketKey(bucket, startkey)); it.Valid(); it.Next() {
			item := it.Item()
			k := keyWithoutBucket(item.Key(), bucket)
			if k == nil {
				return nil
			}

			// Adjust rangeIdx if needed
			if fixedbytes > 0 {
				cmp := int(-1)
				for cmp != 0 {
					cmp = bytes.Compare(k[:fixedbytes-1], startkey[:fixedbytes-1])
					if cmp == 0 {
						k1 := k[fixedbytes-1] & mask
						k2 := startkey[fixedbytes-1] & mask
						if k1 < k2 {
							cmp = -1
						} else if k1 > k2 {
							cmp = 1
						}
					}
					if cmp < 0 {
						it.Seek(bucketKey(bucket, startkey))
						if !it.Valid() {
							return nil
						}
						item = it.Item()
						k = keyWithoutBucket(item.Key(), bucket)
						if k == nil {
							return nil
						}
					} else if cmp > 0 {
						rangeIdx++
						if rangeIdx == len(startkeys) {
							return nil
						}
						fixedbytes, mask = Bytesmask(fixedbits[rangeIdx])
						startkey = startkeys[rangeIdx]
					}
				}
			}

			err := item.Value(func(v []byte) error {
				if len(v) == 0 {
					return nil
				}
				return walker(rangeIdx, k, v)
			})
			if err != nil {
				return err
			}
		}
		return nil
	})

	return err
}

// MultiPut inserts or updates multiple entries.
// Entries are passed as an array:
// bucket0, key0, val0, bucket1, key1, val1, ...
func (db *BadgerDatabase) MultiPut(triplets ...[]byte) (uint64, error) {
	l := len(triplets)
	err := db.db.Update(func(tx *badger.Txn) error {
		for i := 0; i < l; i += 3 {
			bucket := triplets[i]
			key := triplets[i+1]
			val := triplets[i+2]
			if err := tx.Set(bucketKey(bucket, key), val); err != nil {
				return err
			}
		}
		return nil
	})
	if err != nil {
		return 0, err
	}
	return uint64(l / 3), err
}

func (db *BadgerDatabase) NewBatch() DbWithPendingMutations {
	m := &mutation{
		db:   db,
		puts: newPuts(),
	}
	return m
}

// IdealBatchSize defines the size of the data batches should ideally add in one write.
func (db *BadgerDatabase) IdealBatchSize() int {
	return int(db.db.MaxBatchSize() / 2)
}

// DiskSize returns the total disk size of the database in bytes.
func (db *BadgerDatabase) DiskSize(_ context.Context) (common.StorageSize, error) {
	lsm, vlog := db.db.Size()
	return common.StorageSize(lsm + vlog), nil
}

func (db *BadgerDatabase) ClearBuckets(buckets ...[]byte) error {
	for _, bucket := range buckets {
		if err := db.db.DropPrefix(bucket); err != nil {
			return err
		}
	}
	return nil
}

func (db *BadgerDatabase) BucketsStat(ctx context.Context) (map[string]common.StorageBucketWriteStats, error) {
	return nil, nil
}

// MemCopy creates a copy of the database in a temporary directory.
// We don't do it in memory because BadgerDB doesn't support that.
func (db *BadgerDatabase) MemCopy() Database {
	newDb, err := NewEphemeralBadger()
	if err != nil {
		panic("failed to create tmp database: " + err.Error())
	}

	err = db.db.View(func(readTx *badger.Txn) error {
		return newDb.db.Update(func(writeTx *badger.Txn) error {
			it := readTx.NewIterator(badger.DefaultIteratorOptions)
			defer it.Close()

			for it.Rewind(); it.Valid(); it.Next() {
				item := it.Item()
				k := item.Key()
				err2 := item.Value(func(v []byte) error {
					return writeTx.Set(k, v)
				})
				if err2 != nil {
					return err2
				}
			}
			return nil
		})
	})

	if err != nil {
		panic(err)
	}

	return newDb
}

// TODO [Issue 144] Implement the methods

func (db *BadgerDatabase) WalkAsOf(bucket, hBucket, startkey []byte, fixedbits int, timestamp uint64, walker func([]byte, []byte) (bool, error)) error {
	panic("Not implemented")
}

func (db *BadgerDatabase) Keys() ([][]byte, error) {
	panic("Not implemented")
}

func (db *BadgerDatabase) Ancients() (uint64, error) {
	return 0, errNotSupported
}

func (db *BadgerDatabase) TruncateAncients(items uint64) error {
	return errNotSupported
}

func (db *BadgerDatabase) ID() uint64 {
	return db.id
}