Add callback mechanism and implement on-decode callback

LICENSE.md

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright © 2020 Nikita Tokarchuk
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

mongox-testing/database/ephemeral.go

@@ -30,6 +30,6 @@ func NewEphemeral(URI string) (db *EphemeralDatabase, err error) {
 }
 
 // Close the connection and drop database
-func (e *EphemeralDatabase) Close() error {
+func (e *EphemeralDatabase) Close() (err error) {
 	return e.Client().Database(e.Name()).Drop(e.Context())
 }

mongox/base/getid.go

@@ -6,6 +6,7 @@ import (
 	"go.mongodb.org/mongo-driver/bson/primitive"
 
 	"github.com/mainnika/mongox-go-driver/v2/mongox"
+	"github.com/mainnika/mongox-go-driver/v2/mongox/utils"
 )
 
 // GetID returns source document id
@@ -62,7 +63,7 @@ func getObjectOrPanic(source mongox.JSONBased) (id primitive.D) {
 func getInterfaceOrPanic(source mongox.InterfaceBased) (id interface{}) {
 
 	id = source.GetID()
-	if id != nil {
+	if !utils.IsNil(id) {
 		return id
 	}
 

mongox/base/getprotection.go

@@ -7,11 +7,11 @@ import (
 )
 
 // GetProtection function finds protection field in the source document otherwise returns nil
-func GetProtection(source interface{}) *protection.Key {
+func GetProtection(source interface{}) (key *protection.Key) {
 
 	v := reflect.ValueOf(source)
 	if v.Kind() != reflect.Ptr || v.IsNil() {
-		return nil
+		return
 	}
 
 	el := v.Elem()
@@ -25,14 +25,16 @@ func GetProtection(source interface{}) *protection.Key {
 
 		switch field.Interface().(type) {
 		case *protection.Key:
-			return field.Interface().(*protection.Key)
+			key = field.Interface().(*protection.Key)
 		case protection.Key:
 			ptr := field.Addr()
-			return ptr.Interface().(*protection.Key)
+			key = ptr.Interface().(*protection.Key)
 		default:
 			continue
 		}
+
+		return
 	}
 
-	return nil
+	return
 }

mongox/base/jsonbased/id.go

@@ -14,7 +14,7 @@ type Primary struct {
 }
 
 // GetID returns an _id
-func (p *Primary) GetID() primitive.D {
+func (p *Primary) GetID() (id primitive.D) {
 	return p.ID
 }
 

mongox/base/oidbased/id.go

@@ -14,7 +14,7 @@ type Primary struct {
 }
 
 // GetID returns an _id
-func (p *Primary) GetID() primitive.ObjectID {
+func (p *Primary) GetID() (id primitive.ObjectID) {
 	return p.ID
 }
 

mongox/base/reset.go

@@ -1,6 +1,7 @@
 package base
 
 import (
+	"fmt"
 	"reflect"
 )
 
@@ -19,7 +20,7 @@ func Reset(target interface{}) {
 
 	v := reflect.ValueOf(target)
 	if v.Kind() != reflect.Ptr {
-		panic("reset target should be a pointer")
+		panic(fmt.Errorf("reset target should be a pointer"))
 	}
 
 	t := v.Elem().Type()

mongox/base/stringbased/id.go

@@ -12,7 +12,7 @@ type Primary struct {
 }
 
 // GetID returns an _id
-func (p *Primary) GetID() string {
+func (p *Primary) GetID() (id string) {
 	return p.ID
 }
 

mongox/database/callbacks.go

@@ -0,0 +1,19 @@
+package database
+
+import (
+	"context"
+
+	"github.com/mainnika/mongox-go-driver/v2/mongox/query"
+)
+
+func onDecode(ctx context.Context, iter interface{}, callbacks ...query.OnDecode) (err error) {
+
+	for _, cb := range callbacks {
+		err = cb(ctx, iter)
+		if err != nil {
+			return
+		}
+	}
+
+	return
+}

mongox/database/count.go

@@ -1,17 +1,14 @@
 package database
 
 import (
-	"fmt"
-
 	"go.mongodb.org/mongo-driver/mongo/options"
 
-	"github.com/mainnika/mongox-go-driver/v2/mongox"
 	"github.com/mainnika/mongox-go-driver/v2/mongox/query"
 )
 
 // Count function counts documents in the database by query
 // target is used only to get collection by tag so it'd be better to use nil ptr here
-func (d *Database) Count(target interface{}, filters ...interface{}) (int64, error) {
+func (d *Database) Count(target interface{}, filters ...interface{}) (result int64, err error) {
 
 	collection := d.GetCollectionOf(target)
 	opts := options.Count()
@@ -20,13 +17,7 @@ func (d *Database) Count(target interface{}, filters ...interface{}) (int64, err
 	opts.Limit = composed.Limiter()
 	opts.Skip = composed.Skipper()
 
-	result, err := collection.CountDocuments(d.Context(), composed.M(), opts)
+	result, err = collection.CountDocuments(d.Context(), composed.M(), opts)
-	if err == mongox.ErrNoDocuments {
-		return 0, err
-	}
-	if err != nil {
-		return 0, fmt.Errorf("can't decode desult: %w", err)
-	}
 
-	return result, nil
+	return
 }

mongox/database/database.go

@@ -22,17 +22,18 @@ type Database struct {
 }
 
 // NewDatabase function creates new database instance with mongo client and empty context
-func NewDatabase(client *mongox.Client, dbname string) mongox.Database {
+func NewDatabase(client *mongox.Client, dbname string) (db mongox.Database) {
 
-	db := &Database{}
+	db = &Database{
-	db.client = client
+		client: client,
-	db.dbname = dbname
+		dbname: dbname,
+	}
 
-	return db
+	return
 }
 
 // Client function returns a mongo client
-func (d *Database) Client() *mongox.Client {
+func (d *Database) Client() (client *mongox.Client) {
 	return d.client
 }
 
@@ -48,22 +49,24 @@ func (d *Database) Context() (ctx context.Context) {
 }
 
 // Name function returns a database name
-func (d *Database) Name() string {
+func (d *Database) Name() (name string) {
 	return d.dbname
 }
 
 // New function creates new database context with same client
-func (d *Database) New(ctx context.Context) mongox.Database {
+func (d *Database) New(ctx context.Context) (db mongox.Database) {
 
 	if ctx == nil {
 		ctx = context.Background()
 	}
 
-	return &Database{
+	db = &Database{
 		client: d.client,
 		dbname: d.dbname,
 		ctx:    ctx,
 	}
+
+	return
 }
 
 // GetCollectionOf returns the collection object by the «collection» tag of the given document;
@@ -72,7 +75,7 @@ func (d *Database) New(ctx context.Context) mongox.Database {
 //     base.ObjectID `bson:",inline" json:",inline" collection:"foobars"`
 // 	   ...
 // Will panic if there is no «collection» tag
-func (d *Database) GetCollectionOf(document interface{}) *mongox.Collection {
+func (d *Database) GetCollectionOf(document interface{}) (collection *mongox.Collection) {
 
 	el := reflect.TypeOf(document).Elem()
 	numField := el.NumField()
@@ -111,7 +114,7 @@ func (d *Database) createAggregateLoad(target interface{}, composed *query.Query
 	pipeline := primitive.A{}
 
 	if !composed.Empty() {
-		pipeline = append(pipeline, primitive.M{"$match": primitive.M{"$expr": composed.M()}})
+		pipeline = append(pipeline, primitive.M{"$match": composed.M()})
 	}
 	if composed.Sorter() != nil {
 		pipeline = append(pipeline, primitive.M{"$sort": composed.Sorter()})
@@ -137,9 +140,9 @@ func (d *Database) createAggregateLoad(target interface{}, composed *query.Query
 		if !ok {
 			continue
 		}
-		jsonTag, ok := tag.Lookup("json")
+		jsonTag, _ := tag.Lookup("json")
 		if jsonTag == "-" {
-			return nil, fmt.Errorf("preload private field is impossible")
+			panic(fmt.Errorf("preload private field is impossible"))
 		}
 
 		jsonData := strings.SplitN(jsonTag, ",", 2)
@@ -153,7 +156,7 @@ func (d *Database) createAggregateLoad(target interface{}, composed *query.Query
 			continue
 		}
 		if len(preloadData) == 1 {
-			panic("there is no foreign field")
+			panic(fmt.Errorf("there is no foreign field"))
 		}
 
 		localField := strings.TrimSpace(preloadData[0])
@@ -163,7 +166,7 @@ func (d *Database) createAggregateLoad(target interface{}, composed *query.Query
 
 		foreignField := strings.TrimSpace(preloadData[1])
 		if len(foreignField) == 0 {
-			panic("there is no foreign field")
+			panic(fmt.Errorf("there is no foreign field"))
 		}
 
 		preloadLimiter := 100
@@ -195,7 +198,7 @@ func (d *Database) createAggregateLoad(target interface{}, composed *query.Query
 				typ = typ.Elem()
 			}
 			if typ.Kind() != reflect.Ptr {
-				panic("preload field should have ptr type")
+				panic(fmt.Errorf("preload field should have ptr type"))
 			}
 
 			lookupCollection := d.GetCollectionOf(reflect.Zero(typ).Interface())

mongox/database/deletearray.go

@@ -11,7 +11,7 @@ import (
 )
 
 // DeleteArray removes documents list from a database by their ids
-func (d *Database) DeleteArray(target interface{}) error {
+func (d *Database) DeleteArray(target interface{}) (err error) {
 
 	targetV := reflect.ValueOf(target)
 	targetT := targetV.Type()
@@ -49,11 +49,11 @@ func (d *Database) DeleteArray(target interface{}) error {
 
 	result, err := collection.DeleteMany(d.Context(), primitive.M{"_id": primitive.M{"$in": ids}}, opts)
 	if err != nil {
-		return fmt.Errorf("can't create find and delete result: %w", err)
+		return
 	}
 	if result.DeletedCount != int64(targetLen) {
-		return fmt.Errorf("can't verify delete result: removed count mismatch %d != %d", result.DeletedCount, targetLen)
+		err = fmt.Errorf("can't verify delete result: removed count mismatch %d != %d", result.DeletedCount, targetLen)
 	}
 
-	return nil
+	return
 }

mongox/database/deleteone.go

@@ -7,13 +7,13 @@ import (
 	"go.mongodb.org/mongo-driver/bson/primitive"
 	"go.mongodb.org/mongo-driver/mongo/options"
 
-	"github.com/mainnika/mongox-go-driver/v2/mongox"
 	"github.com/mainnika/mongox-go-driver/v2/mongox/base"
 	"github.com/mainnika/mongox-go-driver/v2/mongox/query"
+	"github.com/mainnika/mongox-go-driver/v2/mongox/utils"
 )
 
 // DeleteOne removes a document from a database and then returns it into target
-func (d *Database) DeleteOne(target interface{}, filters ...interface{}) error {
+func (d *Database) DeleteOne(target interface{}, filters ...interface{}) (err error) {
 
 	collection := d.GetCollectionOf(target)
 	opts := &options.FindOneAndDeleteOptions{}
@@ -22,7 +22,7 @@ func (d *Database) DeleteOne(target interface{}, filters ...interface{}) error {
 
 	opts.Sort = composed.Sorter()
 
-	if target != nil {
+	if !utils.IsNil(target) {
 		composed.And(primitive.M{"_id": base.GetID(target)})
 	}
 
@@ -37,13 +37,7 @@ func (d *Database) DeleteOne(target interface{}, filters ...interface{}) error {
 		return fmt.Errorf("can't create find one and delete result: %w", result.Err())
 	}
 
-	err := result.Decode(target)
+	err = result.Decode(target)
-	if err == mongox.ErrNoDocuments {
-		return err
-	}
-	if err != nil {
-		return fmt.Errorf("can't decode result: %w", err)
-	}
 
-	return nil
+	return
 }

mongox/database/index.go

@@ -21,7 +21,7 @@ import (
 //   `index:"-,+foo,+-bar,unique,allowNull"` -- https://docs.mongodb.com/manual/core/index-partial
 //   `index:"-,unique,allowNull,expireAfter=86400"` -- https://docs.mongodb.com/manual/core/index-ttl
 //   `index:"-,unique,allowNull,expireAfter={{.Expire}}"` -- evaluate index as a golang template with `cfg` arguments
-func (d *Database) IndexEnsure(cfg interface{}, document interface{}) error {
+func (d *Database) IndexEnsure(cfg interface{}, document interface{}) (err error) {
 
 	el := reflect.ValueOf(document).Elem().Type()
 	numField := el.NumField()
@@ -41,14 +41,16 @@ func (d *Database) IndexEnsure(cfg interface{}, document interface{}) error {
 			return fmt.Errorf("bson tag is not defined for field:%v document:%v", field, document)
 		}
 
-		tmpBuffer := &bytes.Buffer{}
+		var tmpBuffer = &bytes.Buffer{}
-		tpl, err := template.New("").Parse(indexTag)
+		var tpl *template.Template
+
+		tpl, err = template.New("").Parse(indexTag)
 		if err != nil {
-			panic(fmt.Errorf("invalid prop template, %v", indexTag))
+			panic(fmt.Errorf("invalid prop template %v, err:%w", indexTag, err))
 		}
 		err = tpl.Execute(tmpBuffer, cfg)
 		if err != nil {
-			panic(fmt.Errorf("failed to evaluate prop template, %v", indexTag))
+			panic(fmt.Errorf("failed to evaluate prop template %v, err:%w", indexTag, err))
 		}
 
 		indexString := tmpBuffer.String()
@@ -64,15 +66,15 @@ func (d *Database) IndexEnsure(cfg interface{}, document interface{}) error {
 			panic(fmt.Errorf("cannot evaluate index key"))
 		}
 
-		index := primitive.M{key: 1}
 		opts := &options.IndexOptions{
 			Background: &f,
 			Unique:     &f,
 			Name:       &name,
 		}
 
+		index := primitive.D{{Key: key, Value: 1}}
 		if indexValues[0] == "-" {
-			index[key] = -1
+			index = primitive.D{{Key: key, Value: -1}}
 		}
 
 		for _, prop := range indexValues[1:] {
@@ -114,9 +116,9 @@ func (d *Database) IndexEnsure(cfg interface{}, document interface{}) error {
 				}
 
 				if compoundValue[0] == '-' {
-					index[compoundValue[1:]] = -1
+					index = append(index, primitive.E{compoundValue[1:], -1})
 				} else {
-					index[compoundValue] = 1
+					index = append(index, primitive.E{compoundValue, 1})
 				}
 
 			default:
@@ -126,9 +128,9 @@ func (d *Database) IndexEnsure(cfg interface{}, document interface{}) error {
 
 		_, err = documents.Indexes().CreateOne(d.Context(), mongo.IndexModel{Keys: index, Options: opts})
 		if err != nil {
-			return err
+			return
 		}
 	}
 
-	return nil
+	return
 }

mongox/database/loadarray.go

@@ -10,7 +10,7 @@ import (
 )
 
 // LoadArray loads an array of documents from the database by query
-func (d *Database) LoadArray(target interface{}, filters ...interface{}) error {
+func (d *Database) LoadArray(target interface{}, filters ...interface{}) (err error) {
 
 	targetV := reflect.ValueOf(target)
 	targetT := targetV.Type()
@@ -36,7 +36,7 @@ func (d *Database) LoadArray(target interface{}, filters ...interface{}) error {
 	hasPreloader, _ := composed.Preloader()
 
 	var result *mongox.Cursor
-	var err error
+	var i int
 
 	if hasPreloader {
 		result, err = d.createAggregateLoad(zeroElem.Interface(), composed)
@@ -44,25 +44,35 @@ func (d *Database) LoadArray(target interface{}, filters ...interface{}) error {
 		result, err = d.createSimpleLoad(zeroElem.Interface(), composed)
 	}
 	if err != nil {
-		return fmt.Errorf("can't create find result: %w", err)
+		err = fmt.Errorf("can't create find result: %w", err)
+		return
 	}
 
-	var i int
-
 	for i = 0; result.Next(d.Context()); {
+
+		var elem interface{}
+
 		if targetSliceV.Len() == i {
-			elem := reflect.New(targetSliceElemT.Elem())
+			value := reflect.New(targetSliceElemT.Elem())
-			if err = result.Decode(elem.Interface()); err == nil {
+			err = result.Decode(value.Interface())
-				targetSliceV = reflect.Append(targetSliceV, elem)
+			elem = value.Interface()
-			} else {
+			if err == nil {
-				continue
+				targetSliceV = reflect.Append(targetSliceV, value)
 			}
 		} else {
-			elem := targetSliceV.Index(i).Interface()
+			elem = targetSliceV.Index(i).Interface()
 			base.Reset(elem)
-			if err = result.Decode(elem); err != nil {
+			err = result.Decode(elem)
-				continue
 		}
+		if err != nil {
+			_ = result.Close(d.Context())
+			return
+		}
+
+		err = onDecode(d.ctx, elem, composed.OnDecode()...)
+		if err != nil {
+			_ = result.Close(d.Context())
+			return
 		}
 
 		i++

mongox/database/loadone.go

@@ -9,13 +9,12 @@ import (
 )
 
 // LoadOne function loads a first single target document by a query
-func (d *Database) LoadOne(target interface{}, filters ...interface{}) error {
+func (d *Database) LoadOne(target interface{}, filters ...interface{}) (err error) {
 
 	composed := query.Compose(append(filters, query.Limit(1))...)
 	hasPreloader, _ := composed.Preloader()
 
 	var result *mongox.Cursor
-	var err error
 
 	if hasPreloader {
 		result, err = d.createAggregateLoad(target, composed)
@@ -36,5 +35,15 @@ func (d *Database) LoadOne(target interface{}, filters ...interface{}) error {
 
 	base.Reset(target)
 
-	return result.Decode(target)
+	err = result.Decode(target)
+	if err != nil {
+		return
+	}
+
+	err = onDecode(d.ctx, target, composed.OnDecode()...)
+	if err != nil {
+		return
+	}
+
+	return
 }

mongox/database/loadstream.go

@@ -8,10 +8,9 @@ import (
 )
 
 // LoadStream function loads documents one by one into a target channel
-func (d *Database) LoadStream(target interface{}, filters ...interface{}) (mongox.StreamLoader, error) {
+func (d *Database) LoadStream(target interface{}, filters ...interface{}) (loader mongox.StreamLoader, err error) {
 
 	var cursor *mongox.Cursor
-	var err error
 
 	composed := query.Compose(filters...)
 	hasPreloader, _ := composed.Preloader()
@@ -22,10 +21,11 @@ func (d *Database) LoadStream(target interface{}, filters ...interface{}) (mongo
 		cursor, err = d.createSimpleLoad(target, composed)
 	}
 	if err != nil {
-		return nil, fmt.Errorf("can't create find result: %w", err)
+		err = fmt.Errorf("can't create find result: %w", err)
+		return
 	}
 
-	l := &StreamLoader{cur: cursor, ctx: d.Context(), target: target}
+	loader = &StreamLoader{cur: cursor, ctx: d.Context(), target: target, query: composed}
 
-	return l, nil
+	return
 }

mongox/database/saveone.go

@@ -12,7 +12,7 @@ import (
 )
 
 // SaveOne saves a single source document to the database
-func (d *Database) SaveOne(source interface{}) error {
+func (d *Database) SaveOne(source interface{}) (err error) {
 
 	collection := d.GetCollectionOf(source)
 	opts := options.FindOneAndReplace()

mongox/database/streamloader.go

@@ -2,78 +2,79 @@ package database
 
 import (
 	"context"
-	"fmt"
 
 	"github.com/mainnika/mongox-go-driver/v2/mongox"
 	"github.com/mainnika/mongox-go-driver/v2/mongox/base"
+	"github.com/mainnika/mongox-go-driver/v2/mongox/query"
 )
 
 // StreamLoader is a controller for a database cursor
 type StreamLoader struct {
 	cur    *mongox.Cursor
+	query  *query.Query
 	ctx    context.Context
 	target interface{}
 }
 
 // DecodeNext loads next documents to a target or returns an error
-func (l *StreamLoader) DecodeNext() error {
+func (l *StreamLoader) DecodeNext() (err error) {
 
-	hasNext := l.cur.Next(l.ctx)
+	err = l.Next()
-
-	if l.cur.Err() != nil {
-		return l.cur.Err()
-	}
-	if !hasNext {
-		return mongox.ErrNoDocuments
-	}
-
-	base.Reset(l.target)
-
-	err := l.cur.Decode(l.target)
 	if err != nil {
-		return fmt.Errorf("can't decode desult: %w", err)
+		return
 	}
 
-	return nil
+	err = l.Decode()
+	if err != nil {
+		return
+	}
+
+	return
 }
 
 // Decode function decodes the current cursor document into the target
-func (l *StreamLoader) Decode() error {
+func (l *StreamLoader) Decode() (err error) {
 
 	base.Reset(l.target)
 
-	err := l.cur.Decode(l.target)
+	err = l.cur.Decode(l.target)
 	if err != nil {
-		return fmt.Errorf("can't decode desult: %w", err)
+		return
 	}
 
-	return nil
+	err = onDecode(l.ctx, l.target, l.query.OnDecode()...)
+	if err != nil {
+		return
+	}
+
+	return
 }
 
 // Next loads next documents but doesn't perform decoding
-func (l *StreamLoader) Next() error {
+func (l *StreamLoader) Next() (err error) {
 
 	hasNext := l.cur.Next(l.ctx)
+	err = l.cur.Err()
 
-	if l.cur.Err() != nil {
+	if err != nil {
-		return l.cur.Err()
+		return
 	}
 	if !hasNext {
-		return mongox.ErrNoDocuments
+		err = mongox.ErrNoDocuments
 	}
 
-	return nil
+	return
 }
 
-func (l *StreamLoader) Cursor() *mongox.Cursor {
+func (l *StreamLoader) Cursor() (cursor *mongox.Cursor) {
 	return l.cur
 }
 
 // Close cursor
-func (l *StreamLoader) Close() error {
+func (l *StreamLoader) Close() (err error) {
 	return l.cur.Close(l.ctx)
 }
 
-func (l *StreamLoader) Err() error {
+func (l *StreamLoader) Err() (err error) {
 	return l.cur.Err()
 }

mongox/mongox.go

@@ -16,51 +16,51 @@ type (
 
 // Database is the mongox database interface
 type Database interface {
-	Client() *Client
+	Client() (client *Client)
-	Context() context.Context
+	Context() (context context.Context)
-	Name() string
+	Name() (name string)
-	New(ctx context.Context) Database
+	New(ctx context.Context) (db Database)
-	GetCollectionOf(document interface{}) *Collection
+	GetCollectionOf(document interface{}) (collection *Collection)
-	Count(target interface{}, filters ...interface{}) (int64, error)
+	Count(target interface{}, filters ...interface{}) (count int64, err error)
-	DeleteArray(target interface{}) error
+	DeleteArray(target interface{}) (err error)
-	DeleteOne(target interface{}, filters ...interface{}) error
+	DeleteOne(target interface{}, filters ...interface{}) (err error)
-	LoadArray(target interface{}, filters ...interface{}) error
+	LoadArray(target interface{}, filters ...interface{}) (err error)
-	LoadOne(target interface{}, filters ...interface{}) error
+	LoadOne(target interface{}, filters ...interface{}) (err error)
-	LoadStream(target interface{}, filters ...interface{}) (StreamLoader, error)
+	LoadStream(target interface{}, filters ...interface{}) (loader StreamLoader, err error)
-	SaveOne(source interface{}) error
+	SaveOne(source interface{}) (err error)
-	IndexEnsure(cfg interface{}, document interface{}) error
+	IndexEnsure(cfg interface{}, document interface{}) (err error)
 }
 
 // StreamLoader is a interface to control database cursor
 type StreamLoader interface {
-	Cursor() *Cursor
+	Cursor() (cursor *Cursor)
-	DecodeNext() error
+	DecodeNext() (err error)
-	Decode() error
+	Decode() (err error)
-	Next() error
+	Next() (err error)
-	Close() error
+	Close() (err error)
-	Err() error
+	Err() (err error)
 }
 
 // OIDBased is an interface for documents that have objectId type for the _id field
 type OIDBased interface {
-	GetID() primitive.ObjectID
+	GetID() (id primitive.ObjectID)
 	SetID(id primitive.ObjectID)
 }
 
 // StringBased is an interface for documents that have string type for the _id field
 type StringBased interface {
-	GetID() string
+	GetID() (id string)
 	SetID(id string)
 }
 
 // JSONBased is an interface for documents that have object type for the _id field
 type JSONBased interface {
-	GetID() primitive.D
+	GetID() (id primitive.D)
 	SetID(id primitive.D)
 }
 
 // InterfaceBased is an interface for documents that have custom declated type for the _id field
 type InterfaceBased interface {
-	GetID() interface{}
+	GetID() (id interface{})
 	SetID(id interface{})
 }

mongox/query/callbacks.go

@@ -0,0 +1,7 @@
+package query
+
+import (
+	"context"
+)
+
+type OnDecode func(ctx context.Context, iter interface{}) (err error)

mongox/query/compose.go

@@ -7,42 +7,44 @@ import (
 	"go.mongodb.org/mongo-driver/bson/primitive"
 
 	"github.com/mainnika/mongox-go-driver/v2/mongox/base/protection"
+	"github.com/mainnika/mongox-go-driver/v2/mongox/utils"
 )
 
 // Compose is a function to compose filters into a single query
-func Compose(filters ...interface{}) *Query {
+func Compose(filters ...interface{}) (query *Query) {
 
-	q := &Query{}
+	query = &Query{}
 
 	for _, f := range filters {
-		if !Push(q, f) {
+		if !Push(query, f) {
 			panic(fmt.Errorf("unknown filter %v", f))
 		}
 	}
 
-	return q
+	return
 }
 
 // Push applies single filter to a query
-func Push(q *Query, f interface{}) bool {
+func Push(q *Query, f interface{}) (ok bool) {
 
-	if f == nil {
+	if utils.IsNil(f) {
 		return true
 	}
 
-	ok := false
+	ok = false
 	ok = ok || applyBson(q, f)
 	ok = ok || applyLimit(q, f)
 	ok = ok || applySort(q, f)
 	ok = ok || applySkip(q, f)
 	ok = ok || applyProtection(q, f)
 	ok = ok || applyPreloader(q, f)
+	ok = ok || applyCallbacks(q, f)
 
 	return ok
 }
 
 // applyBson is a fallback for a custom bson.M
-func applyBson(q *Query, f interface{}) bool {
+func applyBson(q *Query, f interface{}) (ok bool) {
 
 	if f, ok := f.(bson.M); ok {
 		q.And(f)
@@ -53,7 +55,7 @@ func applyBson(q *Query, f interface{}) bool {
 }
 
 // applyLimits extends query with a limiter
-func applyLimit(q *Query, f interface{}) bool {
+func applyLimit(q *Query, f interface{}) (ok bool) {
 
 	if f, ok := f.(Limiter); ok {
 		q.limiter = f
@@ -64,7 +66,7 @@ func applyLimit(q *Query, f interface{}) bool {
 }
 
 // applySort extends query with a sort rule
-func applySort(q *Query, f interface{}) bool {
+func applySort(q *Query, f interface{}) (ok bool) {
 
 	if f, ok := f.(Sorter); ok {
 		q.sorter = f
@@ -75,7 +77,7 @@ func applySort(q *Query, f interface{}) bool {
 }
 
 // applySkip extends query with a skip number
-func applySkip(q *Query, f interface{}) bool {
+func applySkip(q *Query, f interface{}) (ok bool) {
 
 	if f, ok := f.(Skipper); ok {
 		q.skipper = f
@@ -85,7 +87,7 @@ func applySkip(q *Query, f interface{}) bool {
 	return false
 }
 
-func applyProtection(q *Query, f interface{}) bool {
+func applyProtection(q *Query, f interface{}) (ok bool) {
 
 	var x *primitive.ObjectID
 	var v *int64
@@ -113,7 +115,7 @@ func applyProtection(q *Query, f interface{}) bool {
 	return true
 }
 
-func applyPreloader(q *Query, f interface{}) bool {
+func applyPreloader(q *Query, f interface{}) (ok bool) {
 
 	if f, ok := f.(Preloader); ok {
 		q.preloader = f
@@ -122,3 +124,14 @@ func applyPreloader(q *Query, f interface{}) bool {
 
 	return false
 }
+
+func applyCallbacks(q *Query, f interface{}) (ok bool) {
+
+	switch cb := f.(type) {
+	case OnDecode:
+		q.ondecode = append(q.ondecode, cb)
+		ok = true
+	}
+
+	return
+}

mongox/query/limit.go

@@ -2,7 +2,7 @@ package query
 
 // Limiter is a filter to limit the result
 type Limiter interface {
-	Limit() *int64
+	Limit() (limit *int64)
 }
 
 // Limit is a simple implementation of the Limiter filter
@@ -11,12 +11,14 @@ type Limit int64
 var _ Limiter = Limit(0)
 
 // Limit returns a limit
-func (l Limit) Limit() *int64 {
+func (l Limit) Limit() (limit *int64) {
 
-	lim := int64(l)
+	if l <= 0 {
-	if lim <= 0 {
+		return
-		return nil
 	}
 
-	return &lim
+	limit = new(int64)
+	*limit = int64(l)
+
+	return
 }

mongox/query/preload.go

@@ -2,7 +2,7 @@ package query
 
 // Preloader is a filter to skip the result
 type Preloader interface {
-	Preload() []string
+	Preload() (preloads []string)
 }
 
 // Preload is a simple implementation of the Skipper filter
@@ -11,6 +11,6 @@ type Preload []string
 var _ Preloader = Preload{}
 
 // Preload returns a preload list
-func (l Preload) Preload() []string {
+func (l Preload) Preload() (preloads []string) {
 	return l
 }

mongox/query/query.go

@@ -2,8 +2,6 @@ package query
 
 import (
 	"go.mongodb.org/mongo-driver/bson"
-
-	"reflect"
 )
 
 // Query is an enchanched bson.M map
@@ -13,10 +11,11 @@ type Query struct {
 	sorter    Sorter
 	skipper   Skipper
 	preloader Preloader
+	ondecode  []OnDecode
 }
 
 // And function pushes the elem query to the $and array of the query
-func (q *Query) And(elem bson.M) *Query {
+func (q *Query) And(elem bson.M) (query *Query) {
 
 	if q.m == nil {
 		q.m = bson.M{}
@@ -35,61 +34,59 @@ func (q *Query) And(elem bson.M) *Query {
 }
 
 // Limiter returns limiter value or nil
-func (q *Query) Limiter() *int64 {
+func (q *Query) Limiter() (limit *int64) {
 
 	if q.limiter == nil {
-		return nil
+		return
 	}
 
 	return q.limiter.Limit()
 }
 
 // Sorter is a sort rule for a query
-func (q *Query) Sorter() interface{} {
+func (q *Query) Sorter() (sort interface{}) {
 
 	if q.sorter == nil {
-		return nil
+		return
 	}
 
 	return q.sorter.Sort()
 }
 
 // Skipper is a skipper for a query
-func (q *Query) Skipper() *int64 {
+func (q *Query) Skipper() (skip *int64) {
 
 	if q.skipper == nil {
-		return nil
+		return
 	}
 
 	return q.skipper.Skip()
 }
 
 // Preloader is a preloader list for a query
-func (q *Query) Preloader() (empty bool, preloader []string) {
+func (q *Query) Preloader() (ok bool, preloads []string) {
 
 	if q.preloader == nil {
 		return false, nil
 	}
 
-	preloader = q.preloader.Preload()
+	preloads = q.preloader.Preload()
+	ok = len(preloads) > 0
 
-	if len(preloader) == 0 {
+	return
-		return false, nil
+}
-	}
 
-	return true, preloader
+// OnDecode callback is called after the mongo decode function
+func (q *Query) OnDecode() (callbacks []OnDecode) {
+	return q.ondecode
 }
 
 // Empty checks the query for any content
-func (q *Query) Empty() bool {
+func (q *Query) Empty() (isEmpty bool) {
-
+	return len(q.m) == 0
-	qv := reflect.ValueOf(q.m)
-	keys := qv.MapKeys()
-
-	return len(keys) == 0
 }
 
 // M returns underlying query map
-func (q *Query) M() bson.M {
+func (q *Query) M() (m bson.M) {
 	return q.m
 }

mongox/query/skip.go

@@ -2,7 +2,7 @@ package query
 
 // Skipper is a filter to skip the result
 type Skipper interface {
-	Skip() *int64
+	Skip() (skip *int64)
 }
 
 // Skip is a simple implementation of the Skipper filter
@@ -11,12 +11,14 @@ type Skip int64
 var _ Skipper = Skip(0)
 
 // Skip returns a skip number
-func (l Skip) Skip() *int64 {
+func (l Skip) Skip() (skip *int64) {
 
-	lim := int64(l)
+	if l <= 0 {
-	if lim <= 0 {
+		return
-		return nil
 	}
 
-	return &lim
+	skip = new(int64)
+	*skip = int64(l)
+
+	return
 }

mongox/query/sort.go

@@ -6,7 +6,7 @@ import (
 
 // Sorter is a filter to sort the data before query
 type Sorter interface {
-	Sort() bson.M
+	Sort() (sort bson.M)
 }
 
 // Sort is a simple implementations of the Sorter filter
@@ -15,6 +15,6 @@ type Sort bson.M
 var _ Sorter = &Sort{}
 
 // Sort returns a slice of fields which have to be sorted
-func (f Sort) Sort() bson.M {
+func (f Sort) Sort() (sort bson.M) {
 	return bson.M(f)
 }

mongox/utils/isnil.go

@@ -0,0 +1,23 @@
+package utils
+
+import (
+	"unsafe"
+)
+
+// IsNil function evaluates the interface value to nil
+func IsNil(i interface{}) (isNil bool) {
+
+	type iface struct {
+		_   unsafe.Pointer
+		ptr unsafe.Pointer
+	}
+
+	unpacked := (*iface)(unsafe.Pointer(&i))
+	if unpacked.ptr == nil {
+		isNil = true
+		return
+	}
+
+	isNil = *(*unsafe.Pointer)(unpacked.ptr) == nil
+	return
+}

mongox/utils/isnil_test.go

@@ -0,0 +1,32 @@
+package utils
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestIsNil(t *testing.T) {
+
+	testvalues := []struct {
+		i     interface{}
+		isnil bool
+	}{
+		{nil, true},
+		{(*string)(nil), true},
+		{([]string)(nil), true},
+		{(map[string]string)(nil), true},
+		{(func() bool)(nil), true},
+		{(chan func() bool)(nil), true},
+		{"", true},
+		{0, true},
+		{append(([]string)(nil), ""), false},
+		{[]string{}, false},
+		{1, false},
+		{"1", false},
+	}
+
+	for _, tt := range testvalues {
+		assert.Equal(t, tt.isnil, IsNil(tt.i))
+	}
+}