Add form builder (#235)

* add form builder

* cover VariImage

* test for closing errors

* simplify tests

* add audio api test coverage

* don't leak authToken when printed

* rename api->client

* fix test

audio.go

@@ -4,8 +4,6 @@ import (
 	"bytes"
 	"context"
 	"fmt"
-	"io"
-	"mime/multipart"
 	"net/http"
 	"os"
 )
@@ -55,9 +53,9 @@ func (c *Client) callAudioAPI(
 	endpointSuffix string,
 ) (response AudioResponse, err error) {
 	var formBody bytes.Buffer
-	w := multipart.NewWriter(&formBody)
+	builder := c.createFormBuilder(&formBody)
 
-	if err = audioMultipartForm(request, w); err != nil {
+	if err = audioMultipartForm(request, builder); err != nil {
 		return
 	}
 
@@ -66,7 +64,7 @@ func (c *Client) callAudioAPI(
 	if err != nil {
 		return
 	}
-	req.Header.Add("Content-Type", w.FormDataContentType())
+	req.Header.Add("Content-Type", builder.formDataContentType())
 
 	err = c.sendRequest(req, &response)
 	return
@@ -74,73 +72,47 @@ func (c *Client) callAudioAPI(
 
 // audioMultipartForm creates a form with audio file contents and the name of the model to use for
 // audio processing.
-func audioMultipartForm(request AudioRequest, w *multipart.Writer) error {
+func audioMultipartForm(request AudioRequest, b formBuilder) error {
 	f, err := os.Open(request.FilePath)
 	if err != nil {
 		return fmt.Errorf("opening audio file: %w", err)
 	}
 	defer f.Close()
 
-	fw, err := w.CreateFormFile("file", f.Name())
+	err = b.createFormFile("file", f)
 	if err != nil {
 		return fmt.Errorf("creating form file: %w", err)
 	}
 
-	if _, err = io.Copy(fw, f); err != nil {
-		return fmt.Errorf("reading from opened audio file: %w", err)
-	}
-
-	fw, err = w.CreateFormField("model")
+	err = b.writeField("model", request.Model)
 	if err != nil {
-		return fmt.Errorf("creating form field: %w", err)
-	}
-
-	modelName := bytes.NewReader([]byte(request.Model))
-	if _, err = io.Copy(fw, modelName); err != nil {
 		return fmt.Errorf("writing model name: %w", err)
 	}
 
 	// Create a form field for the prompt (if provided)
 	if request.Prompt != "" {
-		fw, err = w.CreateFormField("prompt")
+		err = b.writeField("prompt", request.Prompt)
 		if err != nil {
-			return fmt.Errorf("creating form field: %w", err)
-		}
-
-		prompt := bytes.NewReader([]byte(request.Prompt))
-		if _, err = io.Copy(fw, prompt); err != nil {
 			return fmt.Errorf("writing prompt: %w", err)
 		}
 	}
 
 	// Create a form field for the temperature (if provided)
 	if request.Temperature != 0 {
-		fw, err = w.CreateFormField("temperature")
+		err = b.writeField("temperature", fmt.Sprintf("%.2f", request.Temperature))
 		if err != nil {
-			return fmt.Errorf("creating form field: %w", err)
-		}
-
-		temperature := bytes.NewReader([]byte(fmt.Sprintf("%.2f", request.Temperature)))
-		if _, err = io.Copy(fw, temperature); err != nil {
 			return fmt.Errorf("writing temperature: %w", err)
 		}
 	}
 
 	// Create a form field for the language (if provided)
 	if request.Language != "" {
-		fw, err = w.CreateFormField("language")
+		err = b.writeField("language", request.Language)
 		if err != nil {
-			return fmt.Errorf("creating form field: %w", err)
-		}
-
-		language := bytes.NewReader([]byte(request.Language))
-		if _, err = io.Copy(fw, language); err != nil {
 			return fmt.Errorf("writing language: %w", err)
 		}
 	}
 
 	// Close the multipart writer
-	w.Close()
-
-	return nil
+	return b.close()
 }