Parse error messages using JSON parser instead of regexes

errors.go

@@ -85,6 +85,7 @@ var (
 	ErrFailedImageProcess   = NewAPIError(400, "Bad Request: IMAGE_PROCESS_FAILED", "Image process failed")
 	ErrInvalidStickerSet    = NewAPIError(400, "Bad Request: STICKERSET_INVALID", "Stickerset is invalid")
 	ErrBadPollOptions       = NewAPIError(400, "Bad Request: expected an Array of String as options")
+	ErrGroupMigrated        = NewAPIError(400, "Bad Request: group chat was upgraded to a supergroup chat")
 
 	// No rights errors
 	ErrNoRightsToRestrict     = NewAPIError(400, "Bad Request: not enough rights to restrict/unrestrict chat member")
@@ -177,6 +178,8 @@ func ErrByDescription(s string) error {
 		return ErrFailedImageProcess
 	case ErrInvalidStickerSet.ʔ():
 		return ErrInvalidStickerSet
+	case ErrGroupMigrated.ʔ():
+		return ErrGroupMigrated
 	default:
 		return nil
 	}

util.go

@@ -59,26 +59,41 @@ func wrapError(err error) error {
 // In other cases it extracts API error. If error is not presented
 // in errors.go, it will be prefixed with `unknown` keyword.
 func extractOk(data []byte) error {
-	match := errorRx.FindStringSubmatch(string(data))
-	if match == nil || len(match) < 3 {
+	// Parse the error message as JSON
+	var tgramApiError struct {
+		Ok bool `json:"ok"`
+		ErrorCode int `json:"error_code"`
+		Description string `json:"description"`
+		Parameters map[string]interface{} `json:"parameters"`
+	}
+	err := json.Unmarshal(data, &tgramApiError)
+	if err != nil {
+		//return errors.Wrap(err, "can't parse JSON reply, the Telegram server is mibehaving")
+		// FIXME / TODO: in this case the error might be at HTTP level, or the content is not JSON (eg. image?)
 		return nil
 	}
 
-	desc := match[2]
-	err := ErrByDescription(desc)
+	if tgramApiError.Ok {
+		// No error
+		return nil
+	}
 
+	err = ErrByDescription(tgramApiError.Description)
 	if err == nil {
-		code, _ := strconv.Atoi(match[1])
-
-		switch code {
+		switch tgramApiError.ErrorCode {
 		case http.StatusTooManyRequests:
-			retry, _ := strconv.Atoi(match[3])
+			retryAfter, ok := tgramApiError.Parameters["retry_after"]
+			if !ok {
+				return NewAPIError(429, tgramApiError.Description)
+			}
+			retryAfterInt, _ := strconv.Atoi(fmt.Sprint(retryAfter))
+
 			err = FloodError{
-				APIError:   NewAPIError(429, desc),
-				RetryAfter: retry,
+				APIError:   NewAPIError(429, tgramApiError.Description),
+				RetryAfter: retryAfterInt,
 			}
 		default:
-			err = fmt.Errorf("telegram unknown: %s (%d)", desc, code)
+			err = fmt.Errorf("telegram unknown: %s (%d)", tgramApiError.Description, tgramApiError.ErrorCode)
 		}
 	}
 

util_test.go

@@ -19,6 +19,9 @@ func TestExtractOk(t *testing.T) {
 		APIError:   NewAPIError(429, "Too Many Requests: retry after 8"),
 		RetryAfter: 8,
 	}, extractOk(data))
+
+	data = []byte(`{"ok":false,"error_code":400,"description":"Bad Request: group chat was upgraded to a supergroup chat","parameters":{"migrate_to_chat_id": -1234}}`)
+	assert.EqualError(t, extractOk(data), ErrGroupMigrated.Error())
 }
 
 func TestExtractMessage(t *testing.T) {