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mongox-go-driver/mongox/common/loadstream.go

85 lines
1.7 KiB

package common
import (
"context"
"fmt"
"go.mongodb.org/mongo-driver/mongo"
"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 {
*mongo.Cursor
ctx context.Context
target interface{}
}
// DecodeNext loads next documents to a target or returns an error
func (l *StreamLoader) DecodeNext() error {
hasNext := l.Cursor.Next(l.ctx)
if l.Cursor.Err() != nil {
return l.Cursor.Err()
}
if !hasNext {
return mongo.ErrNoDocuments
}
base.Reset(l.target)
err := l.Decode(l.target)
if err != nil {
return fmt.Errorf("can't decode desult: %w", err)
}
return nil
}
// Next loads next documents but doesn't perform decoding
func (l *StreamLoader) Next() error {
hasNext := l.Cursor.Next(l.ctx)
if l.Cursor.Err() != nil {
return l.Cursor.Err()
}
if !hasNext {
return mongo.ErrNoDocuments
}
return nil
}
// Close cursor
func (l *StreamLoader) Close() error {
return l.Cursor.Close(l.ctx)
}
// LoadStream function loads documents one by one into a target channel
func LoadStream(db mongox.Database, target interface{}, filters ...interface{}) (*StreamLoader, error) {
var cursor *mongo.Cursor
var err error
composed := query.Compose(filters...)
hasPreloader, _ := composed.Preloader()
if hasPreloader {
cursor, err = createAggregateLoad(db, target, composed)
} else {
cursor, err = createSimpleLoad(db, target, composed)
}
if err != nil {
return nil, fmt.Errorf("can't create find result: %w", err)
}
l := &StreamLoader{Cursor: cursor, ctx: db.Context(), target: target}
return l, nil
}