package shard

import (
	"context"
	"errors"
	"fmt"
	"slices"
	"sync"

	"git.frostfs.info/TrueCloudLab/frostfs-node/internal/logs"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/core/object"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor"
	meta "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/metabase"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard/mode"
	"git.frostfs.info/TrueCloudLab/frostfs-observability/tracing"
	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/client"
	objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
	"go.uber.org/zap"
	"golang.org/x/sync/errgroup"
)

func (s *Shard) handleMetabaseFailure(ctx context.Context, stage string, err error) error {
	s.log.Error(ctx, logs.ShardMetabaseFailureSwitchingMode,
		zap.String("stage", stage),
		zap.Stringer("mode", mode.ReadOnly),
		zap.Error(err))

	err = s.SetMode(ctx, mode.ReadOnly)
	if err == nil {
		return nil
	}

	s.log.Error(ctx, logs.ShardCantMoveShardToReadonlySwitchMode,
		zap.String("stage", stage),
		zap.Stringer("mode", mode.DegradedReadOnly),
		zap.Error(err))

	err = s.SetMode(ctx, mode.DegradedReadOnly)
	if err != nil {
		return fmt.Errorf("could not switch to mode %s", mode.Mode(mode.DegradedReadOnly))
	}
	return nil
}

// Open opens all Shard's components.
func (s *Shard) Open(ctx context.Context) error {
	components := []interface {
		Open(context.Context, mode.Mode) error
	}{
		s.blobStor,
	}
	m := s.GetMode()

	if !m.NoMetabase() {
		components = append(components, s.metaBase)
	}

	if s.hasWriteCache() && !m.NoMetabase() {
		components = append(components, s.writeCache)
	}

	if s.pilorama != nil {
		components = append(components, s.pilorama)
	}

	for i, component := range components {
		if err := component.Open(ctx, m); err != nil {
			if component == s.metaBase {
				// We must first open all other components to avoid
				// opening non-existent DB in read-only mode.
				for j := i + 1; j < len(components); j++ {
					if err := components[j].Open(ctx, m); err != nil {
						// Other components must be opened, fail.
						return fmt.Errorf("could not open %T: %w", components[j], err)
					}
				}
				err = s.handleMetabaseFailure(ctx, "open", err)
				if err != nil {
					return err
				}

				break
			}

			return fmt.Errorf("could not open %T: %w", component, err)
		}
	}
	return nil
}

type metabaseSynchronizer Shard

func (x *metabaseSynchronizer) Init(ctx context.Context) error {
	ctx, span := tracing.StartSpanFromContext(ctx, "metabaseSynchronizer.Init")
	defer span.End()

	return (*Shard)(x).refillMetabase(ctx)
}

// Init initializes all Shard's components.
func (s *Shard) Init(ctx context.Context) error {
	m := s.GetMode()
	if err := s.initializeComponents(ctx, m); err != nil {
		return err
	}

	s.updateMetrics(ctx)

	s.gc = &gc{
		gcCfg:       &s.gcCfg,
		remover:     s.removeGarbage,
		stopChannel: make(chan struct{}),
		eventChan:   make(chan Event),
		mEventHandler: map[eventType]*eventHandlers{
			eventNewEpoch: {
				cancelFunc: func() {},
				handlers: []eventHandler{
					s.collectExpiredLocks,
					s.collectExpiredObjects,
					s.collectExpiredTombstones,
					s.collectExpiredMetrics,
				},
			},
		},
	}
	if s.gc.metrics != nil {
		s.gc.metrics.SetShardID(s.info.ID.String())
	}

	s.gc.init(ctx)

	s.rb = newRebuilder()
	if !m.NoMetabase() {
		s.rb.Start(ctx, s.blobStor, s.metaBase, s.log)
	}
	s.writecacheSealCancel.Store(dummyCancel)
	return nil
}

func (s *Shard) initializeComponents(ctx context.Context, m mode.Mode) error {
	type initializer interface {
		Init(context.Context) error
	}

	var components []initializer

	if !m.NoMetabase() {
		var initMetabase initializer

		if s.NeedRefillMetabase() {
			initMetabase = (*metabaseSynchronizer)(s)
		} else {
			initMetabase = s.metaBase
		}

		components = []initializer{
			s.blobStor, initMetabase,
		}
	} else {
		components = []initializer{s.blobStor}
	}

	if s.hasWriteCache() && !m.NoMetabase() {
		components = append(components, s.writeCache)
	}

	if s.pilorama != nil {
		components = append(components, s.pilorama)
	}

	for _, component := range components {
		if err := component.Init(ctx); err != nil {
			if component == s.metaBase {
				if errors.Is(err, meta.ErrOutdatedVersion) || errors.Is(err, meta.ErrIncompletedUpgrade) {
					return fmt.Errorf("metabase initialization: %w", err)
				}

				err = s.handleMetabaseFailure(ctx, "init", err)
				if err != nil {
					return err
				}

				break
			}

			return fmt.Errorf("could not initialize %T: %w", component, err)
		}
	}
	return nil
}

func (s *Shard) refillMetabase(ctx context.Context) error {
	path := s.metaBase.DumpInfo().Path
	s.metricsWriter.SetRefillStatus(path, "running")
	s.metricsWriter.SetRefillPercent(path, 0)
	var success bool
	defer func() {
		if success {
			s.metricsWriter.SetRefillStatus(path, "completed")
		} else {
			s.metricsWriter.SetRefillStatus(path, "failed")
		}
	}()

	err := s.metaBase.Reset()
	if err != nil {
		return fmt.Errorf("could not reset metabase: %w", err)
	}

	withCount := true
	totalObjects, err := s.blobStor.ObjectsCount(ctx)
	if err != nil {
		s.log.Warn(ctx, logs.EngineRefillFailedToGetObjectsCount, zap.Error(err))
		withCount = false
	}

	eg, egCtx := errgroup.WithContext(ctx)
	if s.cfg.refillMetabaseWorkersCount > 0 {
		eg.SetLimit(s.cfg.refillMetabaseWorkersCount)
	}

	var completedCount uint64
	var metricGuard sync.Mutex
	itErr := blobstor.IterateBinaryObjects(egCtx, s.blobStor, func(addr oid.Address, data []byte, descriptor []byte) error {
		eg.Go(func() error {
			var success bool
			defer func() {
				s.metricsWriter.IncRefillObjectsCount(path, len(data), success)
				if withCount {
					metricGuard.Lock()
					completedCount++
					s.metricsWriter.SetRefillPercent(path, uint32(completedCount*100/totalObjects))
					metricGuard.Unlock()
				}
			}()

			if err := s.refillObject(egCtx, data, addr, descriptor); err != nil {
				return err
			}
			success = true
			return nil
		})

		select {
		case <-egCtx.Done():
			return egCtx.Err()
		default:
			return nil
		}
	})

	egErr := eg.Wait()

	err = errors.Join(egErr, itErr)
	if err != nil {
		return fmt.Errorf("could not put objects to the meta: %w", err)
	}

	err = s.metaBase.SyncCounters()
	if err != nil {
		return fmt.Errorf("could not sync object counters: %w", err)
	}

	success = true
	s.metricsWriter.SetRefillPercent(path, 100)
	return nil
}

func (s *Shard) refillObject(ctx context.Context, data []byte, addr oid.Address, descriptor []byte) error {
	obj := objectSDK.New()
	if err := obj.Unmarshal(data); err != nil {
		s.log.Warn(ctx, logs.ShardCouldNotUnmarshalObject,
			zap.Stringer("address", addr),
			zap.Error(err))
		return nil
	}

	hasIndexedAttribute := slices.IndexFunc(obj.Attributes(), func(attr objectSDK.Attribute) bool { return meta.IsAtrributeIndexed(attr.Key()) }) > 0

	var isIndexedContainer bool
	if hasIndexedAttribute {
		info, err := s.containerInfo.Info(addr.Container())
		if err != nil {
			return err
		}
		if info.Removed {
			s.log.Debug(ctx, logs.ShardSkipObjectFromResyncContainerDeleted, zap.Stringer("address", addr))
			return nil
		}
		isIndexedContainer = info.Indexed
	}

	var err error
	switch obj.Type() {
	case objectSDK.TypeTombstone:
		err = s.refillTombstoneObject(ctx, obj)
	case objectSDK.TypeLock:
		err = s.refillLockObject(ctx, obj)
	default:
	}
	if err != nil {
		return err
	}

	var mPrm meta.PutPrm
	mPrm.SetObject(obj)
	mPrm.SetStorageID(descriptor)
	mPrm.SetIndexAttributes(hasIndexedAttribute && isIndexedContainer)

	_, err = s.metaBase.Put(ctx, mPrm)
	if err != nil && !client.IsErrObjectAlreadyRemoved(err) && !errors.Is(err, meta.ErrObjectIsExpired) {
		return err
	}
	return nil
}

func (s *Shard) refillLockObject(ctx context.Context, obj *objectSDK.Object) error {
	var lock objectSDK.Lock
	if err := lock.Unmarshal(obj.Payload()); err != nil {
		return fmt.Errorf("could not unmarshal lock content: %w", err)
	}

	locked := make([]oid.ID, lock.NumberOfMembers())
	lock.ReadMembers(locked)

	cnr, _ := obj.ContainerID()
	id, _ := obj.ID()
	err := s.metaBase.Lock(ctx, cnr, id, locked)
	if err != nil {
		return fmt.Errorf("could not lock objects: %w", err)
	}
	return nil
}

func (s *Shard) refillTombstoneObject(ctx context.Context, obj *objectSDK.Object) error {
	tombstone := objectSDK.NewTombstone()

	if err := tombstone.Unmarshal(obj.Payload()); err != nil {
		return fmt.Errorf("could not unmarshal tombstone content: %w", err)
	}

	tombAddr := object.AddressOf(obj)
	memberIDs := tombstone.Members()
	tombMembers := make([]oid.Address, 0, len(memberIDs))

	for i := range memberIDs {
		a := tombAddr
		a.SetObject(memberIDs[i])

		tombMembers = append(tombMembers, a)
	}

	var inhumePrm meta.InhumePrm

	inhumePrm.SetTombstoneAddress(tombAddr)
	inhumePrm.SetAddresses(tombMembers...)

	_, err := s.metaBase.Inhume(ctx, inhumePrm)
	if err != nil {
		return fmt.Errorf("could not inhume objects: %w", err)
	}
	return nil
}

// Close releases all Shard's components.
func (s *Shard) Close(ctx context.Context) error {
	if s.rb != nil {
		s.rb.Stop(ctx, s.log)
	}
	var components []interface{ Close(context.Context) error }

	if s.pilorama != nil {
		components = append(components, s.pilorama)
	}

	if s.hasWriteCache() {
		prev := s.writecacheSealCancel.Swap(notInitializedCancel)
		prev.cancel() // no need to wait: writecache.Seal and writecache.Close lock the same mutex
		components = append(components, s.writeCache)
	}

	components = append(components, s.blobStor, s.metaBase)

	var lastErr error
	for _, component := range components {
		if err := component.Close(ctx); err != nil {
			lastErr = err
			s.log.Error(ctx, logs.ShardCouldNotCloseShardComponent, zap.Error(err))
		}
	}

	// If Init/Open was unsuccessful gc can be nil.
	if s.gc != nil {
		s.gc.stop(ctx)
	}

	return lastErr
}

// Reload reloads configuration portions that are necessary.
// If a config option is invalid, it logs an error and returns nil.
// If there was a problem with applying new configuration, an error is returned.
func (s *Shard) Reload(ctx context.Context, opts ...Option) error {
	ctx, span := tracing.StartSpanFromContext(ctx, "Shard.Reload")
	defer span.End()

	// Do not use defaultCfg here missing options need not be reloaded.
	var c cfg
	for i := range opts {
		opts[i](&c)
	}

	unlock := s.lockExclusive()
	defer unlock()

	s.rb.Stop(ctx, s.log)
	if !s.info.Mode.NoMetabase() {
		defer func() {
			s.rb.Start(ctx, s.blobStor, s.metaBase, s.log)
		}()
	}

	ok, err := s.metaBase.Reload(ctx, c.metaOpts...)
	if err != nil {
		if errors.Is(err, meta.ErrDegradedMode) {
			s.log.Error(ctx, logs.ShardCantOpenMetabaseMoveToADegradedMode, zap.Error(err))
			_ = s.setMode(ctx, mode.DegradedReadOnly)
		}
		return err
	}
	if ok {
		var err error
		if c.refillMetabase {
			// Here we refill metabase only if a new instance was opened. This is a feature,
			// we don't want to hang for some time just because we forgot to change
			// config after the node was updated.
			err = s.refillMetabase(ctx)
		} else {
			err = s.metaBase.Init(ctx)
		}
		if err != nil {
			s.log.Error(ctx, logs.ShardCantInitializeMetabaseMoveToADegradedreadonlyMode, zap.Error(err))
			_ = s.setMode(ctx, mode.DegradedReadOnly)
			return err
		}
	}
	return s.setMode(ctx, c.info.Mode)
}

func (s *Shard) lockExclusive() func() {
	s.setModeRequested.Store(true)
	val := s.gcCancel.Load()
	if val != nil {
		cancelGC := val.(context.CancelFunc)
		cancelGC()
	}
	if c := s.writecacheSealCancel.Load(); c != nil {
		c.cancel()
	}
	s.m.Lock()
	s.setModeRequested.Store(false)
	return s.m.Unlock
}