Implement `echo` action (#18)

PROTOCOL.md

@@ -182,3 +182,22 @@ Get the decrypted contents of a specific file.
     }
 }
 ```
+
+### Echo
+
+Send the `echoResponse` in the request as a response.
+
+#### Request
+
+```
+{
+    "action": "echo",
+    "echoResponse": <anything>
+}
+```
+
+#### Response
+
+```
+<echoResponse>
+```

request/process.go

@@ -22,10 +22,11 @@ type settings struct {
 }
 
 type request struct {
-	Action   string   `json:"action"`
-	Settings settings `json:"settings"`
-	File     string   `json:"file"`
-	Store    string   `json:"store"`
+	Action       string      `json:"action"`
+	Settings     settings    `json:"settings"`
+	File         string      `json:"file"`
+	Store        string      `json:"store"`
+	EchoResponse interface{} `json:"echoResponse"`
 }
 
 // Process handles browser request
@@ -61,6 +62,8 @@ func Process() {
 		listFiles(request)
 	case "fetch":
 		fetchDecryptedContents(request)
+	case "echo":
+		response.SendRaw(request.EchoResponse)
 	default:
 		log.Errorf("Received a browser request with an unknown action: %+v", request)
 		response.SendErrorAndExit(

response/response.go

@@ -64,7 +64,7 @@ func MakeFetchResponse() *FetchResponse {
 
 // SendOk sends a success response to the browser extension in the predefined json format
 func SendOk(data interface{}) {
-	send(&okResponse{
+	SendRaw(&okResponse{
 		Status:  "ok",
 		Version: version.Code,
 		Data:    data,
@@ -73,7 +73,7 @@ func SendOk(data interface{}) {
 
 // SendErrorAndExit sends an error response to the browser extension in the predefined json format and exits with the specified exit code
 func SendErrorAndExit(errorCode errors.Code, params *map[errors.Field]string) {
-	send(&errorResponse{
+	SendRaw(&errorResponse{
 		Status:  "error",
 		Code:    errorCode,
 		Version: version.Code,
@@ -83,24 +83,17 @@ func SendErrorAndExit(errorCode errors.Code, params *map[errors.Field]string) {
 	errors.ExitWithCode(errorCode)
 }
 
-func send(data interface{}) {
-	switch data.(type) {
-	case *okResponse:
-	case *errorResponse:
-		break
-	default:
-		log.Fatalf("Only data of type OkResponse and ErrorResponse is allowed to be sent to the browser extension, attempted to send: %+v", data)
-	}
-
+// SendRaw sends a raw data to the browser extension
+func SendRaw(response interface{}) {
 	var bytesBuffer bytes.Buffer
-	if err := json.NewEncoder(&bytesBuffer).Encode(data); err != nil {
-		log.Fatal("Unable to encode data for sending: ", err)
+	if err := json.NewEncoder(&bytesBuffer).Encode(response); err != nil {
+		log.Fatal("Unable to encode response for sending: ", err)
 	}
 
 	if err := binary.Write(os.Stdout, binary.LittleEndian, uint32(bytesBuffer.Len())); err != nil {
-		log.Fatal("Unable to send the length of the response data: ", err)
+		log.Fatal("Unable to send the length of the response: ", err)
 	}
 	if _, err := bytesBuffer.WriteTo(os.Stdout); err != nil {
-		log.Fatal("Unable to send the response data: ", err)
+		log.Fatal("Unable to send the response: ", err)
 	}
 }