package engine

import (
	"context"

	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard"
	"git.frostfs.info/TrueCloudLab/frostfs-observability/tracing"
	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.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/trace"
)

// SelectPrm groups the parameters of Select operation.
type SelectPrm struct {
	cnr              cid.ID
	filters          objectSDK.SearchFilters
	indexedContainer bool
}

// SelectRes groups the resulting values of Select operation.
type SelectRes struct {
	addrList []oid.Address
}

// WithContainerID is a Select option to set the container id to search in.
func (p *SelectPrm) WithContainerID(cnr cid.ID, indexedContainer bool) {
	p.cnr = cnr
	p.indexedContainer = indexedContainer
}

// WithFilters is a Select option to set the object filters.
func (p *SelectPrm) WithFilters(fs objectSDK.SearchFilters) {
	p.filters = fs
}

// AddressList returns list of addresses of the selected objects.
func (r SelectRes) AddressList() []oid.Address {
	return r.addrList
}

// Select selects the objects from local storage that match select parameters.
//
// Returns any error encountered that did not allow to completely select the objects.
//
// Returns an error if executions are blocked (see BlockExecution).
func (e *StorageEngine) Select(ctx context.Context, prm SelectPrm) (res SelectRes, err error) {
	ctx, span := tracing.StartSpanFromContext(ctx, "StorageEngine.Select",
		trace.WithAttributes(
			attribute.String("container_id", prm.cnr.EncodeToString()),
		))
	defer span.End()
	defer elapsed("Select", e.metrics.AddMethodDuration)()

	err = e.execIfNotBlocked(func() error {
		res, err = e._select(ctx, prm)
		return err
	})

	return
}

func (e *StorageEngine) _select(ctx context.Context, prm SelectPrm) (SelectRes, error) {
	addrList := make([]oid.Address, 0)
	uniqueMap := make(map[string]struct{})

	var outError error

	var shPrm shard.SelectPrm
	shPrm.SetContainerID(prm.cnr, prm.indexedContainer)
	shPrm.SetFilters(prm.filters)

	e.iterateOverUnsortedShards(func(sh hashedShard) (stop bool) {
		res, err := sh.Select(ctx, shPrm)
		if err != nil {
			e.reportShardError(sh, "could not select objects from shard", err)
			return false
		}

		for _, addr := range res.AddressList() { // save only unique values
			if _, ok := uniqueMap[addr.EncodeToString()]; !ok {
				uniqueMap[addr.EncodeToString()] = struct{}{}
				addrList = append(addrList, addr)
			}
		}

		return false
	})

	return SelectRes{
		addrList: addrList,
	}, outError
}

// List returns `limit` available physically storage object addresses in engine.
// If limit is zero, then returns all available object addresses.
//
// Returns an error if executions are blocked (see BlockExecution).
func (e *StorageEngine) List(ctx context.Context, limit uint64) (res SelectRes, err error) {
	defer elapsed("List", e.metrics.AddMethodDuration)()
	err = e.execIfNotBlocked(func() error {
		res, err = e.list(ctx, limit)
		return err
	})

	return
}

func (e *StorageEngine) list(ctx context.Context, limit uint64) (SelectRes, error) {
	addrList := make([]oid.Address, 0, limit)
	uniqueMap := make(map[string]struct{})
	ln := uint64(0)

	// consider iterating over shuffled shards
	e.iterateOverUnsortedShards(func(sh hashedShard) (stop bool) {
		res, err := sh.List(ctx) // consider limit result of shard iterator
		if err != nil {
			e.reportShardError(sh, "could not select objects from shard", err)
		} else {
			for _, addr := range res.AddressList() { // save only unique values
				if _, ok := uniqueMap[addr.EncodeToString()]; !ok {
					uniqueMap[addr.EncodeToString()] = struct{}{}
					addrList = append(addrList, addr)

					ln++
					if limit > 0 && ln >= limit {
						return true
					}
				}
			}
		}

		return false
	})

	return SelectRes{
		addrList: addrList,
	}, nil
}

// Select selects objects from local storage using provided filters.
func Select(ctx context.Context, storage *StorageEngine, cnr cid.ID, isIndexedContainer bool, fs objectSDK.SearchFilters) ([]oid.Address, error) {
	var selectPrm SelectPrm
	selectPrm.WithContainerID(cnr, isIndexedContainer)
	selectPrm.WithFilters(fs)

	res, err := storage.Select(ctx, selectPrm)
	if err != nil {
		return nil, err
	}

	return res.AddressList(), nil
}

// List returns `limit` available physically storage object addresses in
// engine. If limit is zero, then returns all available object addresses.
func List(ctx context.Context, storage *StorageEngine, limit uint64) ([]oid.Address, error) {
	res, err := storage.List(ctx, limit)
	if err != nil {
		return nil, err
	}

	return res.AddressList(), nil
}