fix: derive JSON/Clash subscription URLs from configured subURI (#5203)

* fix: derive JSON/Clash subscription URLs from configured subURI

When subURI is explicitly configured (reverse-proxy setup) but subJsonURI
or subClashURI are not, BuildSubURIBase generates URLs with the raw sub-
server port (2096) and the wrong scheme (http), producing broken links
on the subscription page (e.g. http://domain:2096/json/SUB_ID).

Fix: in BuildURLs, when subURI is set, extract its scheme+host and use
that as the base for all unconfigured sibling URLs instead of calling
BuildSubURIBase. This ensures JSON and Clash Copy URLs match the reverse-
proxy endpoint.

Fixes: JSON/Clash subscription URLs shown on the subscription info page
now correctly inherit the configured subURI's scheme and host.

* fix(sub): fall back to request base when configured subURI is unparseable

Harden the JSON/Clash URL derivation added for the reverse-proxy fix:
extractBaseFromURI now returns "" when the configured subURI has no
scheme/host, and BuildURLs falls back to the request-derived base in
that case instead of emitting a broken value (e.g. ":///json/ABC").

Add a regression test covering a scheme-less subURI.

---------

Co-authored-by: w3struk <w3struk@gmail.com>
Co-authored-by: Sanaei <ho3ein.sanaei@gmail.com>

internal/sub/build_urls_test.go

@@ -69,3 +69,51 @@ func TestBuildURLs_EmptySubId(t *testing.T) {
 		t.Fatalf("empty subId must yield empty URLs, got %q %q %q", a, b, c)
 	}
 }
+
+// A subscriber arriving via a reverse proxy (subURI configured with full
+// HTTPS URL) must see the same scheme+host in the JSON and Clash Copy
+// URLs as in the main subURL — not the raw sub-server port 2096.
+func TestBuildURLs_DerivesJsonFromConfiguredSubURI(t *testing.T) {
+	initSubDB(t)
+	s := &SubService{}
+	s.PrepareForRequest("sub.example.com")
+
+	// Simulate the admin having set subURI (reverse-proxy setup).
+	database.GetDB().Exec(
+		"INSERT INTO settings (key, value) VALUES (?, ?)",
+		"subURI", "https://example.com/sub-xxx/")
+
+	subURL, jsonURL, clashURL := s.BuildURLs("/sub-xxx/", "/json/", "/clash/", "ABC")
+
+	if subURL != "https://example.com/sub-xxx/ABC" {
+		t.Fatalf("subURL = %q", subURL)
+	}
+	if jsonURL != "https://example.com/json/ABC" {
+		t.Fatalf("jsonURL = %q (should derive scheme+host from subURI), want %q", jsonURL, "https://example.com/json/ABC")
+	}
+	if clashURL != "https://example.com/clash/ABC" {
+		t.Fatalf("clashURL = %q (should derive scheme+host from subURI), want %q", clashURL, "https://example.com/clash/ABC")
+	}
+}
+
+// A malformed subURI (no scheme/host) must not leak a broken base into the
+// JSON/Clash URLs; BuildURLs should fall back to the request-derived base.
+func TestBuildURLs_MalformedSubURIFallsBackToRequestBase(t *testing.T) {
+	initSubDB(t)
+	s := &SubService{}
+	s.PrepareForRequest("sub.example.com")
+
+	// A value with no scheme can't yield a usable scheme+host.
+	database.GetDB().Exec(
+		"INSERT INTO settings (key, value) VALUES (?, ?)",
+		"subURI", "example.com/sub-xxx/")
+
+	_, jsonURL, clashURL := s.BuildURLs("/sub-xxx/", "/json/", "/clash/", "ABC")
+
+	if jsonURL != "http://sub.example.com:2096/json/ABC" {
+		t.Fatalf("jsonURL = %q, want fallback to request base %q", jsonURL, "http://sub.example.com:2096/json/ABC")
+	}
+	if clashURL != "http://sub.example.com:2096/clash/ABC" {
+		t.Fatalf("clashURL = %q, want fallback to request base %q", clashURL, "http://sub.example.com:2096/clash/ABC")
+	}
+}

internal/sub/service.go

@@ -2123,12 +2123,37 @@ func (s *SubService) BuildURLs(subPath, subJsonPath, subClashPath, subId string)
 	base := s.settingService.BuildSubURIBase(s.address)
 
 	subURL = s.buildSingleURL(configuredSubURI, base, subPath, subId)
-	subJsonURL = s.buildSingleURL(configuredSubJsonURI, base, subJsonPath, subId)
-	subClashURL = s.buildSingleURL(configuredSubClashURI, base, subClashPath, subId)
+
+	// When subURI is explicitly configured (reverse-proxy setup), use its
+	// scheme+host as the base for JSON and Clash URLs so they match the
+	// reverse-proxy endpoint instead of the raw sub-server port. Fall back
+	// to the request-derived base if subURI is empty or can't be parsed
+	// into a scheme+host (e.g. a malformed value with no scheme).
+	jsonClashBase := base
+	if configuredSubURI != "" {
+		if derived := s.extractBaseFromURI(configuredSubURI); derived != "" {
+			jsonClashBase = derived
+		}
+	}
+
+	subJsonURL = s.buildSingleURL(configuredSubJsonURI, jsonClashBase, subJsonPath, subId)
+	subClashURL = s.buildSingleURL(configuredSubClashURI, jsonClashBase, subClashPath, subId)
 
 	return subURL, subJsonURL, subClashURL
 }
 
+// extractBaseFromURI extracts scheme://host from a configured URI.
+// e.g., "https://example.com/sub-xxx/" → "https://example.com".
+// Returns "" when the URI is empty or lacks a scheme/host, so callers can
+// fall back to the request-derived base instead of emitting a broken value.
+func (s *SubService) extractBaseFromURI(uri string) string {
+	u, err := url.Parse(uri)
+	if err != nil || u.Scheme == "" || u.Host == "" {
+		return ""
+	}
+	return fmt.Sprintf("%s://%s", u.Scheme, u.Host)
+}
+
 // buildSingleURL constructs a single URL using configured URI or base components
 func (s *SubService) buildSingleURL(configuredURI, base, basePath, subId string) string {
 	if configuredURI != "" {