package kv

import (
	"bytes"
	"context"

	types "github.com/prysmaticlabs/eth2-types"
	"github.com/prysmaticlabs/prysm/encoding/bytesutil"
	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
	bolt "go.etcd.io/bbolt"
)

var migrationArchivedIndex0Key = []byte("archive_index_0")

func migrateArchivedIndex(ctx context.Context, db *bolt.DB) error {
	if updateErr := db.Update(func(tx *bolt.Tx) error {
		mb := tx.Bucket(migrationsBucket)
		if b := mb.Get(migrationArchivedIndex0Key); bytes.Equal(b, migrationCompleted) {
			return nil // Migration already completed.
		}

		bkt := tx.Bucket(archivedRootBucket)
		if bkt == nil {
			return nil
		}
		// Remove "last archived index" key before iterating over all keys.
		if err := bkt.Delete(lastArchivedIndexKey); err != nil {
			return err
		}

		var highest types.Slot
		c := bkt.Cursor()
		for k, v := c.First(); k != nil; k, v = c.Next() {
			// Look up actual slot from block
			b := tx.Bucket(blocksBucket).Get(v)
			// Skip this key if there is no block for whatever reason.
			if b == nil {
				continue
			}
			blk := &ethpb.SignedBeaconBlock{}
			if err := decode(context.TODO(), b, blk); err != nil {
				return err
			}
			if err := tx.Bucket(stateSlotIndicesBucket).Put(bytesutil.SlotToBytesBigEndian(blk.Block.Slot), v); err != nil {
				return err
			}
			if blk.Block.Slot > highest {
				highest = blk.Block.Slot
			}
			// check if context is cancelled in between
			if ctx.Err() != nil {
				return ctx.Err()
			}
		}

		// Delete deprecated buckets.
		for _, bkt := range [][]byte{slotsHasObjectBucket, archivedRootBucket} {
			if tx.Bucket(bkt) != nil {
				if err := tx.DeleteBucket(bkt); err != nil {
					return err
				}
			}
		}

		// Mark migration complete.
		return mb.Put(migrationArchivedIndex0Key, migrationCompleted)
	}); updateErr != nil {
		log.WithError(updateErr).Errorf("could not migrate bucket: %s", archivedRootBucket)
		return updateErr
	}
	return nil
}