// getMaxUsedIdx returns the highest used index from the used addresses bucket
// of the given pool, series and branch.
func getMaxUsedIdx(tx walletdb.Tx, poolID []byte, seriesID uint32, branch Branch) (Index, error) {
	maxIdx := Index(0)
	usedAddrs := tx.RootBucket().Bucket(poolID).Bucket(usedAddrsBucketName)
	bucket := usedAddrs.Bucket(getUsedAddrBucketID(seriesID, branch))
	if bucket == nil {
		return maxIdx, nil
	}
	// FIXME: This is far from optimal and should be optimized either by storing
	// a separate key in the DB with the highest used idx for every
	// series/branch or perhaps by doing a large gap linear forward search +
	// binary backwards search (e.g. check for 1000000, 2000000, ....  until it
	// doesn't exist, and then use a binary search to find the max using the
	// discovered bounds).
	err := bucket.ForEach(
		func(k, v []byte) error {
			idx := Index(bytesToUint32(k))
			if idx > maxIdx {
				maxIdx = idx
			}
			return nil
		})
	if err != nil {
		return Index(0), newError(ErrDatabase, "failed to get highest idx of used addresses", err)
	}
	return maxIdx, nil
}

// getUsedAddrHash returns the addr hash with the given index from the used
// addresses bucket of the given pool, series and branch.
func getUsedAddrHash(tx walletdb.Tx, poolID []byte, seriesID uint32, branch Branch,
	index Index) []byte {

	usedAddrs := tx.RootBucket().Bucket(poolID).Bucket(usedAddrsBucketName)
	bucket := usedAddrs.Bucket(getUsedAddrBucketID(seriesID, branch))
	if bucket == nil {
		return nil
	}
	return bucket.Get(uint32ToBytes(uint32(index)))
}

// putUsedAddrHash adds an entry (key==index, value==encryptedHash) to the used
// addresses bucket of the given pool, series and branch.
func putUsedAddrHash(tx walletdb.Tx, poolID []byte, seriesID uint32, branch Branch,
	index Index, encryptedHash []byte) error {

	usedAddrs := tx.RootBucket().Bucket(poolID).Bucket(usedAddrsBucketName)
	bucket, err := usedAddrs.CreateBucketIfNotExists(getUsedAddrBucketID(seriesID, branch))
	if err != nil {
		return newError(ErrDatabase, "failed to store used address hash", err)
	}
	return bucket.Put(uint32ToBytes(uint32(index)), encryptedHash)
}

// putSeriesRow stores the given series row inside a voting pool bucket named
// after poolID. The voting pool bucket does not need to be created
// beforehand.
func putSeriesRow(tx walletdb.Tx, poolID []byte, ID uint32, row *dbSeriesRow) error {
	bucket, err := tx.RootBucket().CreateBucketIfNotExists(poolID)
	if err != nil {
		str := fmt.Sprintf("cannot create bucket %v", poolID)
		return newError(ErrDatabase, str, err)
	}
	bucket = bucket.Bucket(seriesBucketName)
	serialized, err := serializeSeriesRow(row)
	if err != nil {
		return err
	}
	err = bucket.Put(uint32ToBytes(ID), serialized)
	if err != nil {
		str := fmt.Sprintf("cannot put series %v into bucket %v", serialized, poolID)
		return newError(ErrDatabase, str, err)
	}
	return nil
}

// loadAllSeries returns a map of all the series stored inside a voting pool
// bucket, keyed by id.
func loadAllSeries(tx walletdb.Tx, poolID []byte) (map[uint32]*dbSeriesRow, error) {
	bucket := tx.RootBucket().Bucket(poolID).Bucket(seriesBucketName)
	allSeries := make(map[uint32]*dbSeriesRow)
	err := bucket.ForEach(
		func(k, v []byte) error {
			seriesID := bytesToUint32(k)
			series, err := deserializeSeriesRow(v)
			if err != nil {
				return err
			}
			allSeries[seriesID] = series
			return nil
		})
	if err != nil {
		return nil, err
	}
	return allSeries, nil
}

// putPool stores a voting pool in the database, creating a bucket named
// after the voting pool id and two other buckets inside it to store series and
// used addresses for that pool.
func putPool(tx walletdb.Tx, poolID []byte) error {
	poolBucket, err := tx.RootBucket().CreateBucket(poolID)
	if err != nil {
		return newError(ErrDatabase, fmt.Sprintf("cannot create pool %v", poolID), err)
	}
	_, err = poolBucket.CreateBucket(seriesBucketName)
	if err != nil {
		return newError(ErrDatabase, fmt.Sprintf("cannot create series bucket for pool %v",
			poolID), err)
	}
	_, err = poolBucket.CreateBucket(usedAddrsBucketName)
	if err != nil {
		return newError(ErrDatabase, fmt.Sprintf("cannot create used addrs bucket for pool %v",
			poolID), err)
	}
	_, err = poolBucket.CreateBucket(withdrawalsBucketName)
	if err != nil {
		return newError(
			ErrDatabase, fmt.Sprintf("cannot create withdrawals bucket for pool %v", poolID), err)
	}
	return nil
}

func getWithdrawal(tx walletdb.Tx, poolID []byte, roundID uint32) []byte {
	bucket := tx.RootBucket().Bucket(poolID)
	return bucket.Get(uint32ToBytes(roundID))
}

func putWithdrawal(tx walletdb.Tx, poolID []byte, roundID uint32, serialized []byte) error {
	bucket := tx.RootBucket().Bucket(poolID)
	return bucket.Put(uint32ToBytes(roundID), serialized)
}

// existsPool checks the existence of a bucket named after the given
// voting pool id.
func existsPool(tx walletdb.Tx, poolID []byte) bool {
	bucket := tx.RootBucket().Bucket(poolID)
	return bucket != nil
}