docs: sync public link configuration reference

internal/links/links.go

@@ -6,9 +6,52 @@ import (
 	"strings"
 )
 
-const DefaultPublicBaseURL = "https://telesrv.net"
+const (
+	DefaultPublicBaseURL = "https://telesrv.net"
+	DefaultWebBaseURL    = "https://web.telesrv.net"
+	DefaultAppScheme     = "telesrv"
+	DefaultAppName       = "telesrv"
+)
 const MaxChatlistSlugBytes = 128
 
+// ValidateAppScheme normalizes the client-visible custom URL scheme used by
+// public landing pages. Standard Web schemes and Telegram's official tg scheme
+// are deliberately rejected: the latter remains a manual compatibility link
+// and must never become the automatic open target.
+func ValidateAppScheme(raw string) (string, error) {
+	scheme := strings.ToLower(strings.TrimSpace(raw))
+	if scheme == "" {
+		scheme = DefaultAppScheme
+	}
+	for i, r := range scheme {
+		if (r >= 'a' && r <= 'z') || (i > 0 && ((r >= '0' && r <= '9') || r == '+' || r == '-' || r == '.')) {
+			continue
+		}
+		return "", fmt.Errorf("must match [a-z][a-z0-9+.-]*")
+	}
+	switch scheme {
+	case "http", "https", "tg":
+		return "", fmt.Errorf("reserved scheme %q is not allowed", scheme)
+	}
+	return scheme, nil
+}
+
+func ValidateAppName(raw string) (string, error) {
+	name := strings.TrimSpace(raw)
+	if name == "" {
+		return "", fmt.Errorf("must not be empty")
+	}
+	if len([]rune(name)) > 64 {
+		return "", fmt.Errorf("must not exceed 64 characters")
+	}
+	for _, r := range name {
+		if r < 0x20 || r == 0x7f {
+			return "", fmt.Errorf("must not contain control characters")
+		}
+	}
+	return name, nil
+}
+
 func NormalizeBaseURL(raw string) string {
 	raw = strings.TrimSpace(raw)
 	if raw == "" {

internal/links/links_test.go

@@ -2,6 +2,7 @@ package links
 
 import (
 	"net/url"
+	"strings"
 	"testing"
 )
 
@@ -59,6 +60,45 @@ func TestValidateBaseURL(t *testing.T) {
 	}
 }
 
+func TestValidateAppScheme(t *testing.T) {
+	tests := []struct {
+		name    string
+		raw     string
+		want    string
+		wantErr bool
+	}{
+		{name: "default", raw: "", want: "telesrv"},
+		{name: "normalized", raw: "  My-App+Dev  ", want: "my-app+dev"},
+		{name: "starts with digit", raw: "1app", wantErr: true},
+		{name: "colon", raw: "myapp:", wantErr: true},
+		{name: "official tg", raw: "tg", wantErr: true},
+		{name: "http", raw: "http", wantErr: true},
+		{name: "https", raw: "https", wantErr: true},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			got, err := ValidateAppScheme(tc.raw)
+			if (err != nil) != tc.wantErr {
+				t.Fatalf("ValidateAppScheme(%q) error = %v, wantErr %v", tc.raw, err, tc.wantErr)
+			}
+			if got != tc.want {
+				t.Fatalf("ValidateAppScheme(%q) = %q, want %q", tc.raw, got, tc.want)
+			}
+		})
+	}
+}
+
+func TestValidateAppName(t *testing.T) {
+	if got, err := ValidateAppName("  Example Chat  "); err != nil || got != "Example Chat" {
+		t.Fatalf("ValidateAppName valid = %q, %v", got, err)
+	}
+	for _, raw := range []string{"", "   ", "bad\nname", strings.Repeat("x", 65)} {
+		if got, err := ValidateAppName(raw); err == nil {
+			t.Fatalf("ValidateAppName(%q) = %q, want error", raw, got)
+		}
+	}
+}
+
 func TestBuildPreservesBasePathAndQuery(t *testing.T) {
 	got := Build("http://127.0.0.1:2401/root/", "/call/abc", url.Values{"slug": []string{"abc"}})
 	if want := "http://127.0.0.1:2401/root/call/abc?slug=abc"; got != want {