Implement optional io.Reader in AudioRequest (#303) (#265) (#331)

* Implement optional io.Reader in AudioRequest (#303) (#265)

* Fix err shadowing

* Add test to cover AudioRequest io.Reader usage

* Add additional test cases to cover AudioRequest io.Reader usage

* Add test to cover opening the file specified in an AudioRequest

internal/form_builder.go

@@ -1,13 +1,16 @@
 package openai
 
 import (
+	"fmt"
 	"io"
 	"mime/multipart"
 	"os"
+	"path"
 )
 
 type FormBuilder interface {
 	CreateFormFile(fieldname string, file *os.File) error
+	CreateFormFileReader(fieldname string, r io.Reader, filename string) error
 	WriteField(fieldname, value string) error
 	Close() error
 	FormDataContentType() string
@@ -24,15 +27,28 @@ func NewFormBuilder(body io.Writer) *DefaultFormBuilder {
 }
 
 func (fb *DefaultFormBuilder) CreateFormFile(fieldname string, file *os.File) error {
-	fieldWriter, err := fb.writer.CreateFormFile(fieldname, file.Name())
+	return fb.createFormFile(fieldname, file, file.Name())
+}
+
+func (fb *DefaultFormBuilder) CreateFormFileReader(fieldname string, r io.Reader, filename string) error {
+	return fb.createFormFile(fieldname, r, path.Base(filename))
+}
+
+func (fb *DefaultFormBuilder) createFormFile(fieldname string, r io.Reader, filename string) error {
+	if filename == "" {
+		return fmt.Errorf("filename cannot be empty")
+	}
+
+	fieldWriter, err := fb.writer.CreateFormFile(fieldname, filename)
 	if err != nil {
 		return err
 	}
 
-	_, err = io.Copy(fieldWriter, file)
+	_, err = io.Copy(fieldWriter, r)
 	if err != nil {
 		return err
 	}
+
 	return nil
 }