merged from gramsrv upstream

internal/store/postgres/community_catalog_cache.go

@@ -0,0 +1,47 @@
+package postgres
+
+import (
+	"context"
+
+	"telesrv/internal/readmodelcache"
+	"telesrv/internal/store/postgres/sqlcgen"
+)
+
+const communityCatalogPresenceKey = "active"
+
+// CommunityCatalogCache is the global, version-invalidated gate in front of
+// owner-specific joined-Community reads. It caches only whether any non-deleted
+// Community exists; it never caches membership, collapsed/pinned state or a
+// Community payload.
+type CommunityCatalogCache struct {
+	cache *readmodelcache.Cache[string, bool]
+}
+
+func NewCommunityCatalogCache() *CommunityCatalogCache {
+	return &CommunityCatalogCache{cache: readmodelcache.New[string, bool](readmodelcache.Config[string, bool]{MaxEntries: 1})}
+}
+
+func (c *CommunityCatalogCache) hasActive(ctx context.Context, db sqlcgen.DBTX) (bool, error) {
+	if c == nil {
+		var active bool
+		err := db.QueryRow(ctx, `SELECT EXISTS (SELECT 1 FROM communities WHERE NOT deleted)`).Scan(&active)
+		return active, err
+	}
+	return c.cache.GetOrLoad(ctx, communityCatalogPresenceKey, func() (bool, error) {
+		var active bool
+		err := db.QueryRow(ctx, `SELECT EXISTS (SELECT 1 FROM communities WHERE NOT deleted)`).Scan(&active)
+		return active, err
+	})
+}
+
+func (c *CommunityCatalogCache) invalidate() {
+	if c != nil {
+		c.cache.Invalidate(communityCatalogPresenceKey)
+	}
+}
+
+func (c *CommunityCatalogCache) flush() {
+	if c != nil {
+		c.cache.Flush()
+	}
+}