package kv

import (
	"context"

	"github.com/prysmaticlabs/prysm/encoding/bytesutil"
	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
	bolt "go.etcd.io/bbolt"
	"go.opencensus.io/trace"
)

// SaveStateSummary saves a state summary object to the DB.
func (s *Store) SaveStateSummary(ctx context.Context, summary *ethpb.StateSummary) error {
	ctx, span := trace.StartSpan(ctx, "BeaconDB.SaveStateSummary")
	defer span.End()

	return s.SaveStateSummaries(ctx, []*ethpb.StateSummary{summary})
}

// SaveStateSummaries saves state summary objects to the DB.
func (s *Store) SaveStateSummaries(ctx context.Context, summaries []*ethpb.StateSummary) error {
	ctx, span := trace.StartSpan(ctx, "BeaconDB.SaveStateSummaries")
	defer span.End()

	// When we reach the state summary cache prune count,
	// dump the cached state summaries to the DB.
	if s.stateSummaryCache.len() >= stateSummaryCachePruneCount {
		if err := s.saveCachedStateSummariesDB(ctx); err != nil {
			return err
		}
	}

	for _, ss := range summaries {
		s.stateSummaryCache.put(bytesutil.ToBytes32(ss.Root), ss)
	}

	return nil
}

// StateSummary returns the state summary object from the db using input block root.
func (s *Store) StateSummary(ctx context.Context, blockRoot [32]byte) (*ethpb.StateSummary, error) {
	ctx, span := trace.StartSpan(ctx, "BeaconDB.StateSummary")
	defer span.End()

	if s.stateSummaryCache.has(blockRoot) {
		return s.stateSummaryCache.get(blockRoot), nil
	}
	var enc []byte
	if err := s.db.View(func(tx *bolt.Tx) error {
		enc = tx.Bucket(stateSummaryBucket).Get(blockRoot[:])
		return nil
	}); err != nil {
		return nil, err
	}
	if len(enc) == 0 {
		return nil, nil
	}
	summary := &ethpb.StateSummary{}
	if err := decode(ctx, enc, summary); err != nil {
		return nil, err
	}
	return summary, nil
}

// HasStateSummary returns true if a state summary exists in DB.
func (s *Store) HasStateSummary(ctx context.Context, blockRoot [32]byte) bool {
	_, span := trace.StartSpan(ctx, "BeaconDB.HasStateSummary")
	defer span.End()

	var hasSummary bool
	if err := s.db.View(func(tx *bolt.Tx) error {
		hasSummary = s.hasStateSummaryBytes(tx, blockRoot)
		return nil
	}); err != nil {
		return false
	}
	return hasSummary
}

func (s *Store) hasStateSummaryBytes(tx *bolt.Tx, blockRoot [32]byte) bool {
	if s.stateSummaryCache.has(blockRoot) {
		return true
	}
	enc := tx.Bucket(stateSummaryBucket).Get(blockRoot[:])
	return len(enc) > 0
}

// This saves all cached state summary objects to DB, and clears up the cache.
func (s *Store) saveCachedStateSummariesDB(ctx context.Context) error {
	summaries := s.stateSummaryCache.getAll()
	encs := make([][]byte, len(summaries))
	for i, s := range summaries {
		enc, err := encode(ctx, s)
		if err != nil {
			return err
		}
		encs[i] = enc
	}
	if err := s.db.Update(func(tx *bolt.Tx) error {
		bucket := tx.Bucket(stateSummaryBucket)
		for i, s := range summaries {
			if err := bucket.Put(s.Root, encs[i]); err != nil {
				return err
			}
		}
		return nil
	}); err != nil {
		return err
	}
	s.stateSummaryCache.clear()
	return nil
}