feat: status page id validation and cache key

server/internal/services/statuspages.go

@@ -2,6 +2,8 @@ package services
 
 import (
 	"context"
+	"errors"
+	"regexp"
 	"time"
 
 	"gitea.hostxtra.co.uk/mrhid6/vantage/server/internal/db"
@@ -10,6 +12,26 @@ import (
 	"go.mongodb.org/mongo-driver/v2/mongo/options"
 )
 
+// ErrInvalidPageID is returned for any page id that would not be safe or
+// pleasant in a URL handed to a customer.
+var ErrInvalidPageID = errors.New("page id must be 3-40 characters of a-z, 0-9 and -, starting and ending alphanumeric")
+
+// The slug is operator-chosen rather than random because it is printed on
+// support pages and typed by people. First and last characters are
+// alphanumeric so a page id never reads as a flag or a trailing separator.
+var pageIDRe = regexp.MustCompile(`^[a-z0-9][a-z0-9-]{1,38}[a-z0-9]$`)
+
+func ValidatePageID(id string) error {
+	if !pageIDRe.MatchString(id) {
+		return ErrInvalidPageID
+	}
+	return nil
+}
+
+func statusCacheKey(instanceID, pageID string) string {
+	return "vantage:status:" + instanceID + ":" + pageID
+}
+
 func spCtx() (context.Context, context.CancelFunc) {
 	return context.WithTimeout(context.Background(), 5*time.Second)
 }

server/internal/services/statuspages_test.go

@@ -1,6 +1,9 @@
 package services
 
-import "testing"
+import (
+	"strings"
+	"testing"
+)
 
 // A new instance-scoped collection that is not in ScopedCollections leaves its
 // rows behind when the instance is deleted. This is the cheapest possible
@@ -20,3 +23,41 @@ func TestStatusCollectionsAreScoped(t *testing.T) {
 		}
 	}
 }
+
+func TestValidatePageID(t *testing.T) {
+	valid := []string{"api", "prod-eu", "status2", "a1b", strings.Repeat("a", 40)}
+	for _, s := range valid {
+		if err := ValidatePageID(s); err != nil {
+			t.Errorf("ValidatePageID(%q) = %v, want nil", s, err)
+		}
+	}
+
+	invalid := []string{
+		"",                        // empty
+		"ab",                      // too short
+		strings.Repeat("a", 41),   // too long
+		"-api",                    // leading hyphen
+		"api-",                    // trailing hyphen
+		"API",                     // uppercase
+		"my page",                 // space
+		"api_v2",                  // underscore
+		"api/v2",                  // path separator
+		"..",                      // dots
+	}
+	for _, s := range invalid {
+		if err := ValidatePageID(s); err == nil {
+			t.Errorf("ValidatePageID(%q) = nil, want error", s)
+		}
+	}
+}
+
+func TestStatusCacheKeyIsScopedByInstance(t *testing.T) {
+	a := statusCacheKey("inst-a", "api")
+	b := statusCacheKey("inst-b", "api")
+	if a == b {
+		t.Fatalf("two instances share a cache key: %q", a)
+	}
+	if a != "vantage:status:inst-a:api" {
+		t.Fatalf("statusCacheKey = %q, want vantage:status:inst-a:api", a)
+	}
+}