PackageMemcache: Enable namespacing for index (#340)

And other cleanup

Author: kevmoo

app/lib/shared/package_memcache.dart

@@ -31,27 +31,27 @@ abstract class UIPackageCache {
 
 /// Uses a [Memache] to set/get/invalidate metadata for packages.
 class AppEnginePackageMemcache implements PackageCache, UIPackageCache {
-  static const Duration EXPIRATION = const Duration(minutes: 10);
-  static const String INDEX_PAGE_KEY = 'pub_index';
-  static const String KEY_PREFIX = 'dart_package_json';
-  static const String UI_KEY_PREFIX = 'dart_package_ui';
-
-  final Memcache memcache;
-  final String keyPrefix;
-  final String uiKeyPrefix;
-
-  AppEnginePackageMemcache(this.memcache, String namespace)
-      : keyPrefix = (namespace == null || namespace.isEmpty)
-            ? KEY_PREFIX
-            : 'ns_${namespace}_$KEY_PREFIX',
-        uiKeyPrefix = (namespace == null || namespace.isEmpty)
-            ? UI_KEY_PREFIX
-            : 'ns_${namespace}_$UI_KEY_PREFIX';
+  static const Duration _cacheExpiration = const Duration(minutes: 10);
+
+  final Memcache _memcache;
+  final String _indexKey;
+  final String _keyPrefix;
+  final String _uiKeyPrefix;
+
+  static String _prefixWithNamespace(String prefix, String namespace) =>
+      (namespace == null || namespace.isEmpty)
+          ? prefix
+          : 'ns_${namespace}_${prefix}';
+
+  AppEnginePackageMemcache(this._memcache, String namespace)
+      : _keyPrefix = _prefixWithNamespace('package_json_', namespace),
+        _uiKeyPrefix = _prefixWithNamespace('package_ui_', namespace),
+        _indexKey = _prefixWithNamespace('pub_index', namespace);
 
   @override
   Future<List<int>> getPackageData(String package) async {
-    final result =
-        await _ignoreErrors(memcache.get(_packageKey(package), asBinary: true));
+    final result = await _ignoreErrors(
+        _memcache.get(_packageKey(package), asBinary: true));
 
     if (result != null)
       _logger.info('memcache["$package"] found');
@@ -64,14 +64,14 @@ class AppEnginePackageMemcache implements PackageCache, UIPackageCache {
   @override
   Future setPackageData(String package, List<int> data) {
     _logger.info('memcache["$package"] setting to new data');
-    return _ignoreErrors(
-        memcache.set(_packageKey(package), data, expiration: EXPIRATION));
+    return _ignoreErrors(_memcache.set(_packageKey(package), data,
+        expiration: _cacheExpiration));
   }
 
   @override
   Future<String> getUIPackagePage(String package, String version) async {
     final result = await _ignoreErrors(
-        memcache.get(_packageUIKey(package, version), asBinary: true));
+        _memcache.get(_packageUIKey(package, version), asBinary: true));
 
     if (result != null) {
       _logger.info('memcache["$package"] rendered UI found');
@@ -85,33 +85,33 @@ class AppEnginePackageMemcache implements PackageCache, UIPackageCache {
   @override
   Future setUIPackagePage(String package, String version, String data) async {
     _logger.info('memcache["$package"] setting to new rendered UI data');
-    return _ignoreErrors(memcache.set(
+    return _ignoreErrors(_memcache.set(
         _packageUIKey(package, version), UTF8.encode(data),
-        expiration: EXPIRATION));
+        expiration: _cacheExpiration));
   }
 
   @override
   Future invalidateUIPackagePage(String package) async {
     _logger.info('memcache["$package"] invalidating UI data');
     return _ignoreErrors(Future.wait([
-      memcache.remove(_packageUIKey(package, null)),
-      memcache.remove(INDEX_PAGE_KEY),
+      _memcache.remove(_packageUIKey(package, null)),
+      _memcache.remove(_indexKey),
     ]));
   }
 
   @override
   Future invalidatePackageData(String package) {
     _logger.info('memcache["$package"] invalidate entry');
     return _ignoreErrors(Future.wait([
-      memcache.remove(_packageKey(package)),
-      memcache.remove(_packageUIKey(package, null)),
-      memcache.remove(INDEX_PAGE_KEY),
+      _memcache.remove(_packageKey(package)),
+      _memcache.remove(_packageUIKey(package, null)),
+      _memcache.remove(_indexKey),
     ]));
   }
 
   @override
   Future<String> getUIIndexPage() async {
-    final result = await _ignoreErrors(memcache.get(INDEX_PAGE_KEY));
+    final result = await _ignoreErrors(_memcache.get(_indexKey));
     if (result != null) {
       _logger.info('memcache[index-page] found rendered UI data');
     } else {
@@ -124,14 +124,14 @@ class AppEnginePackageMemcache implements PackageCache, UIPackageCache {
   Future setUIIndexPage(String content) async {
     _logger.info('memcache[index-page] setting to new rendered UI data');
     await _ignoreErrors(
-        memcache.set(INDEX_PAGE_KEY, content, expiration: EXPIRATION));
+        _memcache.set(_indexKey, content, expiration: _cacheExpiration));
   }
 
-  String _packageKey(String package) => '$keyPrefix$package';
+  String _packageKey(String package) => '$_keyPrefix$package';
 
   String _packageUIKey(String package, String version) {
-    if (version == null) return '$uiKeyPrefix$package';
-    return '$uiKeyPrefix$package**$version';
+    if (version == null) return '$_uiKeyPrefix$package';
+    return '$_uiKeyPrefix$package**$version';
   }
 
   // We are ignoring any memcache errors and just return `null` in this case.