From 1a3468e7c0411118100fbb221e0d0b5bbb132fa1 Mon Sep 17 00:00:00 2001
From: Marco Pedone <m.pedone98@gmail.com>
Date: Tue, 13 Jan 2026 11:33:20 +0100
Subject: [PATCH] feat: improve error handling in GetDataXML function for
 better response management

---
 apps/backend/utils/utils.go | 45 +++++++++++++++++++++----------------
 1 file changed, 26 insertions(+), 19 deletions(-)

diff --git a/apps/backend/utils/utils.go b/apps/backend/utils/utils.go
index b863397..0cf0825 100644
--- a/apps/backend/utils/utils.go
+++ b/apps/backend/utils/utils.go
@@ -1,6 +1,7 @@
 package utils
 
 import (
+	"bytes"
 	"compress/gzip"
 	"encoding/xml"
 	"fmt"
@@ -85,30 +86,36 @@ func GetDataXML[T any](url string) (T, error) {
 	}
 	defer resp.Body.Close()
 
-	if resp.StatusCode != http.StatusOK {
-		body, _ := io.ReadAll(resp.Body)
-		_, _ = saveFailedRequest("non_200", url, req.Header, resp.Header, resp.StatusCode, body, "status error")
-		return result, fmt.Errorf("Failed to fetch url %s: status error: %d", url, resp.StatusCode)
-	}
-	// handle gzip decompression if server used it
-	var raw []byte
-	if strings.Contains(resp.Header.Get("Content-Encoding"), "gzip") {
-		gz, gerr := gzip.NewReader(resp.Body)
-		if gerr != nil {
-			body, _ := io.ReadAll(resp.Body) // best-effort
-			_, _ = saveFailedRequest("gzip_error", url, req.Header, resp.Header, resp.StatusCode, body, gerr.Error())
-			return result, fmt.Errorf("gzip new reader: %w", gerr)
-		}
-		defer gz.Close()
-		raw, err = io.ReadAll(gz)
-	} else {
-		raw, err = io.ReadAll(resp.Body)
-	}
+	raw, err := io.ReadAll(resp.Body)
 	if err != nil {
 		_, _ = saveFailedRequest("read_error", url, req.Header, resp.Header, resp.StatusCode, raw, err.Error())
 		return result, fmt.Errorf("failed to read response: %w", err)
 	}
 
+	if resp.StatusCode != http.StatusOK {
+		_, _ = saveFailedRequest("non_200", url, req.Header, resp.Header, resp.StatusCode, raw, "status error")
+		return result, fmt.Errorf("Failed to fetch url %s: status error: %d", url, resp.StatusCode)
+	}
+
+	// handle gzip decompression if server used it
+	isGzipHeader := strings.Contains(strings.ToLower(resp.Header.Get("Content-Encoding")), "gzip")
+	isGzipMagic := len(raw) > 2 && raw[0] == 0x1f && raw[1] == 0x8b
+
+	if isGzipHeader || isGzipMagic {
+		gz, gerr := gzip.NewReader(bytes.NewReader(raw))
+		if gerr != nil {
+			_, _ = saveFailedRequest("gzip_error", url, req.Header, resp.Header, resp.StatusCode, raw, gerr.Error())
+			return result, fmt.Errorf("gzip new reader: %w", gerr)
+		}
+		defer gz.Close()
+		decompressed, err := io.ReadAll(gz)
+		if err != nil {
+			_, _ = saveFailedRequest("gzip_read_error", url, req.Header, resp.Header, resp.StatusCode, raw, err.Error())
+			return result, fmt.Errorf("gzip read: %w", err)
+		}
+		raw = decompressed
+	}
+
 	// attempt to unmarshal
 	if err := xml.Unmarshal(raw, &result); err != nil {
 		_, _ = saveFailedRequest("unmarshal_error", url, req.Header, resp.Header, resp.StatusCode, raw, err.Error())