package meta

import (
	"context"
	"fmt"
	"time"

	objectV2 "git.frostfs.info/TrueCloudLab/frostfs-api-go/v2/object"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/metaerr"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/util/logicerr"
	"git.frostfs.info/TrueCloudLab/frostfs-observability/tracing"
	apistatus "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/client/status"
	cid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/container/id"
	objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
	"go.etcd.io/bbolt"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/trace"
)

// ExistsPrm groups the parameters of Exists operation.
type ExistsPrm struct {
	addr oid.Address
}

// ExistsRes groups the resulting values of Exists operation.
type ExistsRes struct {
	exists bool
}

var ErrLackSplitInfo = logicerr.New("no split info on parent object")

// SetAddress is an Exists option to set object checked for existence.
func (p *ExistsPrm) SetAddress(addr oid.Address) {
	p.addr = addr
}

// Exists returns the fact that the object is in the metabase.
func (p ExistsRes) Exists() bool {
	return p.exists
}

// Exists returns ErrAlreadyRemoved if addr was marked as removed. Otherwise it
// returns true if addr is in primary index or false if it is not.
//
// Returns an error of type apistatus.ObjectAlreadyRemoved if object has been placed in graveyard.
// Returns the object.ErrObjectIsExpired if the object is presented but already expired.
func (db *DB) Exists(ctx context.Context, prm ExistsPrm) (res ExistsRes, err error) {
	var (
		startedAt = time.Now()
		success   = false
	)
	defer func() {
		db.metrics.AddMethodDuration("Exists", time.Since(startedAt), success)
	}()

	_, span := tracing.StartSpanFromContext(ctx, "metabase.Exists",
		trace.WithAttributes(
			attribute.String("address", prm.addr.EncodeToString()),
		))
	defer span.End()

	db.modeMtx.RLock()
	defer db.modeMtx.RUnlock()

	if db.mode.NoMetabase() {
		return res, ErrDegradedMode
	}

	select {
	case <-ctx.Done():
		return res, ctx.Err()
	default:
	}

	currEpoch := db.epochState.CurrentEpoch()

	err = db.boltDB.View(func(tx *bbolt.Tx) error {
		res.exists, err = db.exists(tx, prm.addr, currEpoch)

		return err
	})
	success = err == nil
	return res, metaerr.Wrap(err)
}

func (db *DB) exists(tx *bbolt.Tx, addr oid.Address, currEpoch uint64) (exists bool, err error) {
	// check graveyard and object expiration first
	switch objectStatus(tx, addr, currEpoch) {
	case 1:
		return false, logicerr.Wrap(new(apistatus.ObjectNotFound))
	case 2:
		return false, logicerr.Wrap(new(apistatus.ObjectAlreadyRemoved))
	case 3:
		return false, ErrObjectIsExpired
	}

	objKey := objectKey(addr.Object(), make([]byte, objectKeySize))

	cnr := addr.Container()
	key := make([]byte, bucketKeySize)

	// if graveyard is empty, then check if object exists in primary bucket
	if inBucket(tx, primaryBucketName(cnr, key), objKey) {
		return true, nil
	}

	// if primary bucket is empty, then check if object exists in parent bucket
	if inBucket(tx, parentBucketName(cnr, key), objKey) {
		splitInfo, err := getSplitInfo(tx, cnr, objKey)
		if err != nil {
			return false, err
		}

		return false, logicerr.Wrap(objectSDK.NewSplitInfoError(splitInfo))
	}

	// if parent bucket is empty, then check if object exists in typed buckets
	return firstIrregularObjectType(tx, cnr, objKey) != objectSDK.TypeRegular, nil
}

// objectStatus returns:
//   - 0 if object is available;
//   - 1 if object with GC mark;
//   - 2 if object is covered with tombstone;
//   - 3 if object is expired.
func objectStatus(tx *bbolt.Tx, addr oid.Address, currEpoch uint64) uint8 {
	// locked object could not be removed/marked with GC/expired
	if objectLocked(tx, addr.Container(), addr.Object()) {
		return 0
	}

	// we check only if the object is expired in the current
	// epoch since it is considered the only corner case: the
	// GC is expected to collect all the objects that have
	// expired previously for less than the one epoch duration

	expired := isExpiredWithAttribute(tx, objectV2.SysAttributeExpEpoch, addr, currEpoch)
	if !expired {
		expired = isExpiredWithAttribute(tx, objectV2.SysAttributeExpEpochNeoFS, addr, currEpoch)
	}

	if expired {
		return 3
	}

	graveyardBkt := tx.Bucket(graveyardBucketName)
	garbageBkt := tx.Bucket(garbageBucketName)
	addrKey := addressKey(addr, make([]byte, addressKeySize))
	return inGraveyardWithKey(addrKey, graveyardBkt, garbageBkt)
}

func inGraveyardWithKey(addrKey []byte, graveyard, garbageBCK *bbolt.Bucket) uint8 {
	if graveyard == nil {
		// incorrect metabase state, does not make
		// sense to check garbage bucket
		return 0
	}

	val := graveyard.Get(addrKey)
	if val == nil {
		if garbageBCK == nil {
			// incorrect node state
			return 0
		}

		val = garbageBCK.Get(addrKey)
		if val != nil {
			// object has been marked with GC
			return 1
		}

		// neither in the graveyard
		// nor was marked with GC mark
		return 0
	}

	// object in the graveyard
	return 2
}

// inBucket checks if key <key> is present in bucket <name>.
func inBucket(tx *bbolt.Tx, name, key []byte) bool {
	bkt := tx.Bucket(name)
	if bkt == nil {
		return false
	}

	// using `get` as `exists`: https://github.com/boltdb/bolt/issues/321
	val := bkt.Get(key)

	return len(val) != 0
}

// getSplitInfo returns SplitInfo structure from root index. Returns error
// if there is no `key` record in root index.
func getSplitInfo(tx *bbolt.Tx, cnr cid.ID, key []byte) (*objectSDK.SplitInfo, error) {
	bucketName := rootBucketName(cnr, make([]byte, bucketKeySize))
	rawSplitInfo := getFromBucket(tx, bucketName, key)
	if len(rawSplitInfo) == 0 {
		return nil, ErrLackSplitInfo
	}

	splitInfo := objectSDK.NewSplitInfo()

	err := splitInfo.Unmarshal(rawSplitInfo)
	if err != nil {
		return nil, fmt.Errorf("can't unmarshal split info from root index: %w", err)
	}

	return splitInfo, nil
}