package kv

import (
	"bytes"
	"strconv"

	"github.com/prysmaticlabs/prysm/shared/bytesutil"
	bolt "go.etcd.io/bbolt"
)

var migrationBlockSlotIndex0Key = []byte("block_slot_index_0")

func migrateBlockSlotIndex(tx *bolt.Tx) error {
	mb := tx.Bucket(migrationsBucket)
	if b := mb.Get(migrationBlockSlotIndex0Key); bytes.Equal(b, migrationCompleted) {
		return nil // Migration already completed.
	}

	bkt := tx.Bucket(blockSlotIndicesBucket)

	// Convert indices from strings to big endian integers.
	if err := bkt.ForEach(func(k, v []byte) error {
		key, err := strconv.ParseUint(string(k), 10, 64)
		if err != nil {
			return err
		}
		if err := bkt.Delete(k); err != nil {
			return err
		}
		return bkt.Put(bytesutil.Uint64ToBytesBigEndian(key), v)
	}); err != nil {
		return err
	}

	return mb.Put(migrationBlockSlotIndex0Key, migrationCompleted)
}