package migration_01_to_11

import (
	"github.com/lightningnetwork/lnd/channeldb/kvdb"
)

var (
	// metaBucket stores all the meta information concerning the state of
	// the database.
	metaBucket = []byte("metadata")

	// dbVersionKey is a boltdb key and it's used for storing/retrieving
	// current database version.
	dbVersionKey = []byte("dbp")
)

// Meta structure holds the database meta information.
type Meta struct {
	// DbVersionNumber is the current schema version of the database.
	DbVersionNumber uint32
}

// putMeta is an internal helper function used in order to allow callers to
// re-use a database transaction. See the publicly exported PutMeta method for
// more information.
func putMeta(meta *Meta, tx kvdb.RwTx) error {
	metaBucket, err := tx.CreateTopLevelBucket(metaBucket)
	if err != nil {
		return err
	}

	return putDbVersion(metaBucket, meta)
}

func putDbVersion(metaBucket kvdb.RwBucket, meta *Meta) error {
	scratch := make([]byte, 4)
	byteOrder.PutUint32(scratch, meta.DbVersionNumber)
	return metaBucket.Put(dbVersionKey, scratch)
}