package engine

import (
	"context"
	"errors"
	"fmt"
	"sync"
	"sync/atomic"

	"git.frostfs.info/TrueCloudLab/frostfs-node/internal/logs"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard/mode"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/util/logicerr"
	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
	"git.frostfs.info/TrueCloudLab/hrw"
	"github.com/google/uuid"
	"github.com/panjf2000/ants/v2"
	"go.uber.org/zap"
	"golang.org/x/sync/errgroup"
)

var errShardNotFound = logicerr.New("shard not found")

type hashedShard struct {
	shardWrapper
	hash uint64
}

type metricsWithID struct {
	id string
	mw MetricRegister
}

func (m *metricsWithID) SetShardID(id string) {
	// concurrent settings are not expected =>
	// no mutex protection
	m.id = id
}

func (m *metricsWithID) SetObjectCounter(objectType string, v uint64) {
	m.mw.SetObjectCounter(m.id, objectType, v)
}

func (m *metricsWithID) AddToObjectCounter(objectType string, delta int) {
	m.mw.AddToObjectCounter(m.id, objectType, delta)
}

func (m *metricsWithID) IncObjectCounter(objectType string) {
	m.mw.AddToObjectCounter(m.id, objectType, +1)
}

func (m *metricsWithID) SetMode(mode mode.Mode) {
	m.mw.SetMode(m.id, mode)
}

func (m *metricsWithID) AddToContainerSize(cnr string, size int64) {
	m.mw.AddToContainerSize(cnr, size)
}

func (m *metricsWithID) AddToPayloadSize(size int64) {
	m.mw.AddToPayloadCounter(m.id, size)
}

func (m *metricsWithID) IncErrorCounter() {
	m.mw.IncErrorCounter(m.id)
}

func (m *metricsWithID) ClearErrorCounter() {
	m.mw.ClearErrorCounter(m.id)
}

func (m *metricsWithID) DeleteShardMetrics() {
	m.mw.DeleteShardMetrics(m.id)
}

func (m *metricsWithID) SetContainerObjectsCount(cnrID string, objectType string, value uint64) {
	m.mw.SetContainerObjectCounter(m.id, cnrID, objectType, value)
}

func (m *metricsWithID) IncContainerObjectsCount(cnrID string, objectType string) {
	m.mw.IncContainerObjectCounter(m.id, cnrID, objectType)
}

func (m *metricsWithID) SubContainerObjectsCount(cnrID string, objectType string, value uint64) {
	m.mw.SubContainerObjectCounter(m.id, cnrID, objectType, value)
}

// AddShard adds a new shard to the storage engine.
//
// Returns any error encountered that did not allow adding a shard.
// Otherwise returns the ID of the added shard.
func (e *StorageEngine) AddShard(ctx context.Context, opts ...shard.Option) (*shard.ID, error) {
	sh, err := e.createShard(ctx, opts)
	if err != nil {
		return nil, fmt.Errorf("could not create a shard: %w", err)
	}

	err = e.addShard(sh)
	if err != nil {
		return nil, fmt.Errorf("could not add %s shard: %w", sh.ID().String(), err)
	}

	if e.cfg.metrics != nil {
		e.cfg.metrics.SetMode(sh.ID().String(), sh.GetMode())
	}

	return sh.ID(), nil
}

func (e *StorageEngine) createShard(_ context.Context, opts []shard.Option) (*shard.Shard, error) {
	id, err := generateShardID()
	if err != nil {
		return nil, fmt.Errorf("could not generate shard ID: %w", err)
	}

	opts = e.appendMetrics(id, opts)

	sh := shard.New(append(opts,
		shard.WithID(id),
		shard.WithExpiredTombstonesCallback(e.processExpiredTombstones),
		shard.WithExpiredLocksCallback(e.processExpiredLocks),
		shard.WithDeletedLockCallback(e.processDeletedLocks),
		shard.WithReportErrorFunc(e.reportShardErrorBackground),
		shard.WithRebuildWorkerLimiter(e.rebuildLimiter),
		shard.WithZeroSizeCallback(e.processZeroSizeContainers),
		shard.WithZeroCountCallback(e.processZeroCountContainers),
	)...)

	if err := sh.UpdateID(); err != nil {
		e.log.Warn(logs.FailedToUpdateShardID, zap.Stringer("shard_id", sh.ID()), zap.String("metabase_path", sh.DumpInfo().MetaBaseInfo.Path), zap.Error(err))
	}

	return sh, nil
}

func (e *StorageEngine) appendMetrics(id *shard.ID, opts []shard.Option) []shard.Option {
	e.mtx.RLock()
	defer e.mtx.RUnlock()

	if e.metrics != nil {
		opts = append(opts,
			shard.WithMetricsWriter(
				&metricsWithID{
					id: id.String(),
					mw: e.metrics,
				},
			),
			shard.WithWriteCacheMetrics(
				&writeCacheMetrics{
					shardID: id.String(),
					metrics: e.metrics.WriteCache(),
				},
			),
			shard.WithGCMetrics(
				&gcMetrics{
					storage: e.metrics.GC(),
					shardID: id.String(),
				},
			),
		)
	}

	return opts
}

func (e *StorageEngine) addShard(sh *shard.Shard) error {
	e.mtx.Lock()
	defer e.mtx.Unlock()

	pool, err := ants.NewPool(int(e.shardPoolSize), ants.WithNonblocking(true))
	if err != nil {
		return fmt.Errorf("could not create pool: %w", err)
	}

	strID := sh.ID().String()
	if _, ok := e.shards[strID]; ok {
		return fmt.Errorf("shard with id %s was already added", strID)
	}

	e.shards[strID] = hashedShard{
		shardWrapper: shardWrapper{
			errorCount: new(atomic.Uint32),
			Shard:      sh,
		},
		hash: hrw.StringHash(strID),
	}

	e.shardPools[strID] = pool

	return nil
}

// removeShards removes specified shards. Skips non-existent shards.
// Logs errors about shards that it could not Close after the removal.
func (e *StorageEngine) removeShards(ids ...string) {
	if len(ids) == 0 {
		return
	}

	ss := make([]hashedShard, 0, len(ids))

	e.mtx.Lock()
	for _, id := range ids {
		sh, found := e.shards[id]
		if !found {
			continue
		}

		sh.DeleteShardMetrics()

		ss = append(ss, sh)
		delete(e.shards, id)

		pool, ok := e.shardPools[id]
		if ok {
			pool.Release()
			delete(e.shardPools, id)
		}

		e.log.Info(logs.EngineShardHasBeenRemoved,
			zap.String("id", id))
	}
	e.mtx.Unlock()

	for _, sh := range ss {
		err := sh.SetMode(mode.Disabled)
		if err != nil {
			e.log.Error(logs.EngineCouldNotChangeShardModeToDisabled,
				zap.Stringer("id", sh.ID()),
				zap.Error(err),
			)
		}
		err = sh.Close()
		if err != nil {
			e.log.Error(logs.EngineCouldNotCloseRemovedShard,
				zap.Stringer("id", sh.ID()),
				zap.Error(err),
			)
		}
	}
}

func generateShardID() (*shard.ID, error) {
	uid, err := uuid.NewRandom()
	if err != nil {
		return nil, err
	}

	bin, err := uid.MarshalBinary()
	if err != nil {
		return nil, err
	}

	return shard.NewIDFromBytes(bin), nil
}

func (e *StorageEngine) sortShards(objAddr interface{ EncodeToString() string }) []hashedShard {
	e.mtx.RLock()
	defer e.mtx.RUnlock()

	h := hrw.StringHash(objAddr.EncodeToString())
	shards := make([]hashedShard, 0, len(e.shards))
	for _, sh := range e.shards {
		shards = append(shards, hashedShard(sh))
	}
	hrw.SortHasherSliceByValue(shards, h)
	return shards
}

func (e *StorageEngine) unsortedShards() []hashedShard {
	e.mtx.RLock()
	defer e.mtx.RUnlock()

	shards := make([]hashedShard, 0, len(e.shards))

	for _, sh := range e.shards {
		shards = append(shards, hashedShard(sh))
	}

	return shards
}

func (e *StorageEngine) iterateOverSortedShards(addr oid.Address, handler func(int, hashedShard) (stop bool)) {
	for i, sh := range e.sortShards(addr) {
		if handler(i, sh) {
			break
		}
	}
}

func (e *StorageEngine) iterateOverUnsortedShards(handler func(hashedShard) (stop bool)) {
	for _, sh := range e.unsortedShards() {
		if handler(sh) {
			break
		}
	}
}

// SetShardMode sets mode of the shard with provided identifier.
//
// Returns an error if shard mode was not set, or shard was not found in storage engine.
func (e *StorageEngine) SetShardMode(id *shard.ID, m mode.Mode, resetErrorCounter bool) error {
	e.mtx.RLock()
	defer e.mtx.RUnlock()

	for shID, sh := range e.shards {
		if id.String() == shID {
			if resetErrorCounter {
				sh.errorCount.Store(0)
				sh.Shard.ClearErrorCounter()
			}
			return sh.SetMode(m)
		}
	}

	return errShardNotFound
}

// HandleNewEpoch notifies every shard about NewEpoch event.
func (e *StorageEngine) HandleNewEpoch(ctx context.Context, epoch uint64) {
	ev := shard.EventNewEpoch(epoch)

	e.mtx.RLock()
	defer e.mtx.RUnlock()

	for _, sh := range e.shards {
		select {
		case <-ctx.Done():
			return
		case sh.NotificationChannel() <- ev:
		}
	}
}

func (e *StorageEngine) DetachShards(ids []*shard.ID) error {
	if len(ids) == 0 {
		return logicerr.New("ids must be non-empty")
	}

	deletedShards, err := e.deleteShards(ids)
	if err != nil {
		return err
	}

	return e.closeShards(deletedShards)
}

// closeShards closes deleted shards. Tries to close all shards.
// Returns single error with joined shard errors.
func (e *StorageEngine) closeShards(deletedShards []hashedShard) error {
	var multiErr error
	var multiErrGuard sync.Mutex
	var eg errgroup.Group
	for _, sh := range deletedShards {
		sh := sh
		eg.Go(func() error {
			err := sh.SetMode(mode.Disabled)
			if err != nil {
				e.log.Error(logs.EngineCouldNotChangeShardModeToDisabled,
					zap.Stringer("id", sh.ID()),
					zap.Error(err),
				)
				multiErrGuard.Lock()
				multiErr = errors.Join(multiErr, fmt.Errorf("could not change shard (id:%s) mode to disabled: %w", sh.ID(), err))
				multiErrGuard.Unlock()
			}

			err = sh.Close()
			if err != nil {
				e.log.Error(logs.EngineCouldNotCloseRemovedShard,
					zap.Stringer("id", sh.ID()),
					zap.Error(err),
				)
				multiErrGuard.Lock()
				multiErr = errors.Join(multiErr, fmt.Errorf("could not close removed shard (id:%s): %w", sh.ID(), err))
				multiErrGuard.Unlock()
			}
			return nil
		})
	}
	if err := eg.Wait(); err != nil {
		return err
	}
	return multiErr
}

// deleteShards deletes shards with specified ids from engine shard list
// and releases all engine resources associated with shards.
// Returns deleted shards or error if some shard could not be deleted.
func (e *StorageEngine) deleteShards(ids []*shard.ID) ([]hashedShard, error) {
	ss := make([]hashedShard, 0, len(ids))

	e.mtx.Lock()
	defer e.mtx.Unlock()

	for _, id := range ids {
		idStr := id.String()
		sh, found := e.shards[idStr]
		if !found {
			return nil, errShardNotFound
		}
		ss = append(ss, sh)
	}

	if len(ss) == len(e.shards) {
		return nil, logicerr.New("could not delete all the shards")
	}

	for _, sh := range ss {
		idStr := sh.ID().String()

		sh.DeleteShardMetrics()

		delete(e.shards, idStr)

		pool, ok := e.shardPools[idStr]
		if ok {
			pool.Release()
			delete(e.shardPools, idStr)
		}

		e.log.Info(logs.EngineShardHasBeenRemoved,
			zap.String("id", idStr))
	}

	return ss, nil
}

func (s hashedShard) Hash() uint64 {
	return s.hash
}