package meta

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"time"

	"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"
)

// InhumePrm encapsulates parameters for Inhume operation.
type InhumePrm struct {
	tomb *oid.Address

	target []oid.Address

	lockObjectHandling bool

	forceRemoval bool
}

// DeletionInfo contains details on deleted object.
type DeletionInfo struct {
	Size uint64
	CID  cid.ID
}

// InhumeRes encapsulates results of Inhume operation.
type InhumeRes struct {
	deletedLockObj   []oid.Address
	availableImhumed uint64
	deletionDetails  []DeletionInfo
}

// AvailableInhumed return number of available object
// that have been inhumed.
func (i InhumeRes) AvailableInhumed() uint64 {
	return i.availableImhumed
}

// DeletedLockObjects returns deleted object of LOCK
// type. Returns always nil if WithoutLockObjectHandling
// was provided to the InhumePrm.
func (i InhumeRes) DeletedLockObjects() []oid.Address {
	return i.deletedLockObj
}

// GetDeletionInfoLength returns amount of stored elements
// in deleted sizes array.
func (i InhumeRes) GetDeletionInfoLength() int {
	return len(i.deletionDetails)
}

// GetDeletionInfoByIndex returns both deleted object sizes and
// associated container ID by index.
func (i InhumeRes) GetDeletionInfoByIndex(target int) DeletionInfo {
	return i.deletionDetails[target]
}

// StoreDeletionInfo stores size of deleted object and associated container ID
// in corresponding arrays.
func (i *InhumeRes) storeDeletionInfo(containerID cid.ID, deletedSize uint64) {
	i.deletionDetails = append(i.deletionDetails, DeletionInfo{
		Size: deletedSize,
		CID:  containerID,
	})
}

// SetAddresses sets a list of object addresses that should be inhumed.
func (p *InhumePrm) SetAddresses(addrs ...oid.Address) {
	p.target = addrs
}

// SetTombstoneAddress sets tombstone address as the reason for inhume operation.
//
// addr should not be nil.
// Should not be called along with SetGCMark.
func (p *InhumePrm) SetTombstoneAddress(addr oid.Address) {
	p.tomb = &addr
}

// SetGCMark marks the object to be physically removed.
//
// Should not be called along with SetTombstoneAddress.
func (p *InhumePrm) SetGCMark() {
	p.tomb = nil
}

// SetLockObjectHandling checks if there were
// any LOCK object among the targets set via WithAddresses.
func (p *InhumePrm) SetLockObjectHandling() {
	p.lockObjectHandling = true
}

// SetForceGCMark allows removal any object. Expected to be
// called only in control service.
func (p *InhumePrm) SetForceGCMark() {
	p.tomb = nil
	p.forceRemoval = true
}

var errBreakBucketForEach = errors.New("bucket ForEach break")

// ErrLockObjectRemoval is returned when inhume operation is being
// performed on lock object, and it is not a forced object removal.
var ErrLockObjectRemoval = logicerr.New("lock object removal")

// Inhume marks objects as removed but not removes it from metabase.
//
// Allows inhuming non-locked objects only. Returns apistatus.ObjectLocked
// if at least one object is locked. Returns ErrLockObjectRemoval if inhuming
// is being performed on lock (not locked) object.
//
// NOTE: Marks any object with GC mark (despite any prohibitions on operations
// with that object) if WithForceGCMark option has been provided.
func (db *DB) Inhume(ctx context.Context, prm InhumePrm) (res InhumeRes, err error) {
	var (
		startedAt = time.Now()
		success   = false
	)
	defer func() {
		db.metrics.AddMethodDuration("Inhume", time.Since(startedAt), success)
	}()
	_, span := tracing.StartSpanFromContext(ctx, "metabase.Inhume")
	defer span.End()

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

	if db.mode.NoMetabase() {
		return InhumeRes{}, ErrDegradedMode
	} else if db.mode.ReadOnly() {
		return InhumeRes{}, ErrReadOnlyMode
	}

	currEpoch := db.epochState.CurrentEpoch()
	err = db.boltDB.Update(func(tx *bbolt.Tx) error {
		return db.inhumeTx(tx, currEpoch, prm, &res)
	})
	success = err == nil
	return res, metaerr.Wrap(err)
}

func (db *DB) inhumeTx(tx *bbolt.Tx, epoch uint64, prm InhumePrm, res *InhumeRes) error {
	garbageBKT := tx.Bucket(garbageBucketName)
	graveyardBKT := tx.Bucket(graveyardBucketName)

	bkt, value, err := db.getInhumeTargetBucketAndValue(garbageBKT, graveyardBKT, &prm)
	if err != nil {
		return err
	}

	buf := make([]byte, addressKeySize)
	for i := range prm.target {
		id := prm.target[i].Object()
		cnr := prm.target[i].Container()

		// prevent locked objects to be inhumed
		if !prm.forceRemoval && objectLocked(tx, cnr, id) {
			return apistatus.ObjectLocked{}
		}

		var lockWasChecked bool

		// prevent lock objects to be inhumed
		// if `Inhume` was called not with the
		// `WithForceGCMark` option
		if !prm.forceRemoval {
			if isLockObject(tx, cnr, id) {
				return ErrLockObjectRemoval
			}

			lockWasChecked = true
		}

		obj, err := db.get(tx, prm.target[i], buf, false, true, epoch)
		targetKey := addressKey(prm.target[i], buf)
		if err == nil {
			err = db.updateDeleteInfo(tx, garbageBKT, graveyardBKT, targetKey, cnr, obj, res)
			if err != nil {
				return err
			}
		}

		if prm.tomb != nil {
			var isTomb bool
			isTomb, err = db.markAsGC(graveyardBKT, garbageBKT, targetKey)
			if err != nil {
				return err
			}

			if isTomb {
				continue
			}
		}

		// consider checking if target is already in graveyard?
		err = bkt.Put(targetKey, value)
		if err != nil {
			return err
		}

		if prm.lockObjectHandling {
			// do not perform lock check if
			// it was already called
			if lockWasChecked {
				// inhumed object is not of
				// the LOCK type
				continue
			}

			if isLockObject(tx, cnr, id) {
				res.deletedLockObj = append(res.deletedLockObj, prm.target[i])
			}
		}
	}

	return db.updateCounter(tx, logical, res.availableImhumed, false)
}

// getInhumeTargetBucketAndValue return target bucket to store inhume result and value that will be put in the bucket.
//
// target bucket of the operation, one of the:
//  1. Graveyard if Inhume was called with a Tombstone
//  2. Garbage if Inhume was called with a GC mark
//
// value that will be put in the bucket, one of the:
//  1. tombstone address if Inhume was called with
//     a Tombstone
//  2. zeroValue if Inhume was called with a GC mark
func (db *DB) getInhumeTargetBucketAndValue(garbageBKT, graveyardBKT *bbolt.Bucket, prm *InhumePrm) (targetBucket *bbolt.Bucket, value []byte, err error) {
	if prm.tomb != nil {
		targetBucket = graveyardBKT
		tombKey := addressKey(*prm.tomb, make([]byte, addressKeySize))

		// it is forbidden to have a tomb-on-tomb in FrostFS,
		// so graveyard keys must not be addresses of tombstones
		data := targetBucket.Get(tombKey)
		if data != nil {
			err := targetBucket.Delete(tombKey)
			if err != nil {
				return nil, nil, fmt.Errorf("could not remove grave with tombstone key: %w", err)
			}
		}

		value = tombKey
	} else {
		targetBucket = garbageBKT
		value = zeroValue
	}
	return targetBucket, value, nil
}

func (db *DB) markAsGC(graveyardBKT, garbageBKT *bbolt.Bucket, key []byte) (bool, error) {
	targetIsTomb, err := isTomb(graveyardBKT, key)
	if err != nil {
		return false, err
	}

	// do not add grave if target is a tombstone
	if targetIsTomb {
		return true, nil
	}

	// if tombstone appears object must be
	// additionally marked with GC
	return false, garbageBKT.Put(key, zeroValue)
}

func (db *DB) updateDeleteInfo(tx *bbolt.Tx, garbageBKT, graveyardBKT *bbolt.Bucket, targetKey []byte, cnr cid.ID, obj *objectSDK.Object, res *InhumeRes) error {
	containerID, _ := obj.ContainerID()
	if inGraveyardWithKey(targetKey, graveyardBKT, garbageBKT) == 0 {
		res.availableImhumed++
		res.storeDeletionInfo(containerID, obj.PayloadSize())
	}

	// if object is stored, and it is regular object then update bucket
	// with container size estimations
	if obj.Type() == objectSDK.TypeRegular {
		err := changeContainerSize(tx, cnr, obj.PayloadSize(), false)
		if err != nil {
			return err
		}
	}
	return nil
}

func isTomb(graveyardBucket *bbolt.Bucket, key []byte) (bool, error) {
	targetIsTomb := false

	// iterate over graveyard and check if target address
	// is the address of tombstone in graveyard.
	err := graveyardBucket.ForEach(func(k, v []byte) error {
		// check if graveyard has record with key corresponding
		// to tombstone address (at least one)
		targetIsTomb = bytes.Equal(v, key)

		if targetIsTomb {
			// break bucket iterator
			return errBreakBucketForEach
		}

		return nil
	})
	if err != nil && !errors.Is(err, errBreakBucketForEach) {
		return false, err
	}
	return targetIsTomb, nil
}