package engine

import (
	"context"
	"sync"
	"time"

	"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/writecache"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/metrics"
	"git.frostfs.info/TrueCloudLab/frostfs-observability/tracing"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/trace"
	"golang.org/x/sync/errgroup"
)

// FlushWriteCachePrm groups the parameters of FlushWriteCache operation.
type FlushWriteCachePrm struct {
	shardID      *shard.ID
	ignoreErrors bool
	seal         bool
}

// SetShardID is an option to set shard ID.
//
// Option is required.
func (p *FlushWriteCachePrm) SetShardID(id *shard.ID) {
	p.shardID = id
}

// SetIgnoreErrors sets errors ignore flag.
func (p *FlushWriteCachePrm) SetIgnoreErrors(ignore bool) {
	p.ignoreErrors = ignore
}

// SetSeal sets seal flag.
func (p *FlushWriteCachePrm) SetSeal(v bool) {
	p.seal = v
}

// FlushWriteCacheRes groups the resulting values of FlushWriteCache operation.
type FlushWriteCacheRes struct{}

// FlushWriteCache flushes write-cache on a single shard.
func (e *StorageEngine) FlushWriteCache(ctx context.Context, p FlushWriteCachePrm) (FlushWriteCacheRes, error) {
	ctx, span := tracing.StartSpanFromContext(ctx, "StorageEngine.FlushWriteCache",
		trace.WithAttributes(
			attribute.String("shard_id", p.shardID.String()),
			attribute.Bool("ignore_errors", p.ignoreErrors),
			attribute.Bool("seal", p.seal),
		))
	defer span.End()

	e.mtx.RLock()
	sh, ok := e.shards[p.shardID.String()]
	e.mtx.RUnlock()

	if !ok {
		return FlushWriteCacheRes{}, errShardNotFound
	}

	var prm shard.FlushWriteCachePrm
	prm.SetIgnoreErrors(p.ignoreErrors)
	prm.SetSeal(p.seal)

	return FlushWriteCacheRes{}, sh.FlushWriteCache(ctx, prm)
}

type SealWriteCachePrm struct {
	ShardIDs     []*shard.ID
	IgnoreErrors bool
}

type ShardSealResult struct {
	ShardID  *shard.ID
	Success  bool
	ErrorMsg string
}

type SealWriteCacheRes struct {
	ShardResults []ShardSealResult
}

// SealWriteCache flushed all data to blobstore and moves write-cache to degraded read only mode.
func (e *StorageEngine) SealWriteCache(ctx context.Context, prm SealWriteCachePrm) (SealWriteCacheRes, error) {
	ctx, span := tracing.StartSpanFromContext(ctx, "StorageEngine.SealWriteCache",
		trace.WithAttributes(
			attribute.Int("shard_id_count", len(prm.ShardIDs)),
			attribute.Bool("ignore_errors", prm.IgnoreErrors),
		))
	defer span.End()

	res := SealWriteCacheRes{
		ShardResults: make([]ShardSealResult, 0, len(prm.ShardIDs)),
	}
	resGuard := &sync.Mutex{}

	eg, egCtx := errgroup.WithContext(ctx)
	for _, shardID := range prm.ShardIDs {
		shardID := shardID
		eg.Go(func() error {
			e.mtx.RLock()
			sh, ok := e.shards[shardID.String()]
			e.mtx.RUnlock()

			if !ok {
				resGuard.Lock()
				defer resGuard.Unlock()
				res.ShardResults = append(res.ShardResults, ShardSealResult{
					ShardID:  shardID,
					ErrorMsg: errShardNotFound.Error(),
				})
				return nil
			}

			err := sh.SealWriteCache(egCtx, shard.SealWriteCachePrm{IgnoreErrors: prm.IgnoreErrors})

			resGuard.Lock()
			defer resGuard.Unlock()

			if err != nil {
				res.ShardResults = append(res.ShardResults, ShardSealResult{
					ShardID:  shardID,
					ErrorMsg: err.Error(),
				})
			} else {
				res.ShardResults = append(res.ShardResults, ShardSealResult{
					ShardID: shardID,
					Success: true,
				})
			}
			return nil
		})
	}

	if err := eg.Wait(); err != nil {
		return SealWriteCacheRes{}, err
	}
	return res, nil
}

type writeCacheMetrics struct {
	shardID string
	metrics metrics.WriteCacheMetrics
}

func (m *writeCacheMetrics) SetShardID(id string) {
	m.shardID = id
}

func (m *writeCacheMetrics) Get(d time.Duration, success bool, st writecache.StorageType) {
	m.metrics.AddMethodDuration(m.shardID, st.String(), "Get", success, d)
}

func (m *writeCacheMetrics) Delete(d time.Duration, success bool, st writecache.StorageType) {
	m.metrics.AddMethodDuration(m.shardID, st.String(), "Delete", success, d)
}

func (m *writeCacheMetrics) Put(d time.Duration, success bool, st writecache.StorageType) {
	m.metrics.AddMethodDuration(m.shardID, st.String(), "Put", success, d)
}

func (m *writeCacheMetrics) SetEstimateSize(db, fstree uint64) {
	m.metrics.SetEstimateSize(m.shardID, writecache.StorageTypeDB.String(), db)
	m.metrics.SetEstimateSize(m.shardID, writecache.StorageTypeFSTree.String(), fstree)
}

func (m *writeCacheMetrics) SetMode(mode mode.Mode) {
	m.metrics.SetMode(m.shardID, mode.String())
}

func (m *writeCacheMetrics) SetActualCounters(db, fstree uint64) {
	m.metrics.SetActualCount(m.shardID, writecache.StorageTypeDB.String(), db)
	m.metrics.SetActualCount(m.shardID, writecache.StorageTypeFSTree.String(), fstree)
}

func (m *writeCacheMetrics) Flush(success bool, st writecache.StorageType) {
	m.metrics.IncOperationCounter(m.shardID, st.String(), "Flush", metrics.NullBool{Bool: success, Valid: true})
}

func (m *writeCacheMetrics) Evict(st writecache.StorageType) {
	m.metrics.IncOperationCounter(m.shardID, st.String(), "Evict", metrics.NullBool{})
}

func (m *writeCacheMetrics) Close() {
	m.metrics.Close(m.shardID)
}