Simplify Go Endpoints + Add Tests (#120)

This MR represents a major refactor of the Go codebase, as well as introducing tests for the handlers. The MR also introduces an endpoint to shutdown or restart the Go server, which may be useful for clients who want to refresh the state of the plugin after checking out branches. Finally, this MR adds a contributing document for users who want to make feature changes.

cmd/attachment.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"bytes"
 	"encoding/json"
 	"fmt"
 	"io"
@@ -8,6 +9,10 @@ import (
 	"os"
 )
 
+type FileReader interface {
+	ReadFile(path string) (io.Reader, error)
+}
+
 type AttachmentRequest struct {
 	FilePath string `json:"file_path"`
 	FileName string `json:"file_name"`
@@ -20,18 +25,40 @@ type AttachmentResponse struct {
 	Url      string `json:"url"`
 }
 
-func AttachmentHandler(w http.ResponseWriter, r *http.Request) {
+type attachmentReader struct{}
+
+func (ar attachmentReader) ReadFile(path string) (io.Reader, error) {
+	file, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+
+	data, err := io.ReadAll(file)
+	if err != nil {
+		return nil, err
+	}
+
+	defer file.Close()
+
+	reader := bytes.NewReader(data)
+
+	return reader, nil
+}
+
+/* attachmentHandler uploads an attachment (file, image, etc) to Gitlab and returns metadata about the upload. */
+func (a *api) attachmentHandler(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "application/json")
 	if r.Method != http.MethodPost {
-		w.WriteHeader(http.StatusMethodNotAllowed)
+		w.Header().Set("Access-Control-Allow-Methods", http.MethodPost)
+		handleError(w, InvalidRequestError{}, "Expected POST", http.StatusMethodNotAllowed)
 		return
 	}
-	c := r.Context().Value("client").(Client)
-	w.Header().Set("Content-Type", "application/json")
 
 	var attachmentRequest AttachmentRequest
+
 	body, err := io.ReadAll(r.Body)
 	if err != nil {
-		c.handleError(w, err, "Could not read request body", http.StatusBadRequest)
+		handleError(w, err, "Could not read request body", http.StatusBadRequest)
 		return
 	}
 
@@ -39,21 +66,23 @@ func AttachmentHandler(w http.ResponseWriter, r *http.Request) {
 
 	err = json.Unmarshal(body, &attachmentRequest)
 	if err != nil {
-		c.handleError(w, err, "Could not unmarshal JSON", http.StatusBadRequest)
+		handleError(w, err, "Could not unmarshal JSON", http.StatusBadRequest)
 		return
 	}
 
-	file, err := os.Open(attachmentRequest.FilePath)
+	file, err := a.fileReader.ReadFile(attachmentRequest.FileName)
 	if err != nil {
-		c.handleError(w, err, fmt.Sprintf("Could not read %s", attachmentRequest.FilePath), http.StatusBadRequest)
+		handleError(w, err, fmt.Sprintf("Could not read %s file", attachmentRequest.FileName), http.StatusInternalServerError)
+	}
+
+	projectFile, res, err := a.client.UploadFile(a.projectInfo.ProjectId, file, attachmentRequest.FileName)
+	if err != nil {
+		handleError(w, err, fmt.Sprintf("Could not upload %s to Gitlab", attachmentRequest.FileName), http.StatusInternalServerError)
 		return
 	}
 
-	defer file.Close()
-
-	projectFile, res, err := c.git.Projects.UploadFile(c.projectId, file, attachmentRequest.FileName)
-	if err != nil {
-		c.handleError(w, err, fmt.Sprintf("Could not upload %s to Gitlab", attachmentRequest.FilePath), res.StatusCode)
+	if res.StatusCode >= 300 {
+		handleError(w, GenericError{endpoint: "/mr/attachment"}, fmt.Sprintf("Could not upload %s to Gitlab", attachmentRequest.FileName), res.StatusCode)
 		return
 	}
 
@@ -69,6 +98,6 @@ func AttachmentHandler(w http.ResponseWriter, r *http.Request) {
 
 	err = json.NewEncoder(w).Encode(response)
 	if err != nil {
-		c.handleError(w, err, "Could not encode response", http.StatusInternalServerError)
+		handleError(w, err, "Could not encode response", http.StatusInternalServerError)
 	}
 }