refactor: refactoring http request creation and sending (#395)

* refactoring http request creation and sending

* fix lint error

* increase the test coverage of client.go

* refactor: Change the style of HTTPRequestBuilder.Build func to one-argument-per-line.

internal/request_builder.go

@@ -3,11 +3,12 @@ package openai
 import (
 	"bytes"
 	"context"
+	"io"
 	"net/http"
 )
 
 type RequestBuilder interface {
-	Build(ctx context.Context, method, url string, request any) (*http.Request, error)
+	Build(ctx context.Context, method, url string, body any, header http.Header) (*http.Request, error)
 }
 
 type HTTPRequestBuilder struct {
@@ -20,21 +21,32 @@ func NewRequestBuilder() *HTTPRequestBuilder {
 	}
 }
 
-func (b *HTTPRequestBuilder) Build(ctx context.Context, method, url string, request any) (*http.Request, error) {
-	if request == nil {
-		return http.NewRequestWithContext(ctx, method, url, nil)
+func (b *HTTPRequestBuilder) Build(
+	ctx context.Context,
+	method string,
+	url string,
+	body any,
+	header http.Header,
+) (req *http.Request, err error) {
+	var bodyReader io.Reader
+	if body != nil {
+		if v, ok := body.(io.Reader); ok {
+			bodyReader = v
+		} else {
+			var reqBytes []byte
+			reqBytes, err = b.marshaller.Marshal(body)
+			if err != nil {
+				return
+			}
+			bodyReader = bytes.NewBuffer(reqBytes)
+		}
 	}
-
-	var reqBytes []byte
-	reqBytes, err := b.marshaller.Marshal(request)
+	req, err = http.NewRequestWithContext(ctx, method, url, bodyReader)
 	if err != nil {
-		return nil, err
+		return
 	}
-
-	return http.NewRequestWithContext(
-		ctx,
-		method,
-		url,
-		bytes.NewBuffer(reqBytes),
-	)
+	if header != nil {
+		req.Header = header
+	}
+	return
 }