Refactor language detection logic to allow non-static CLD data sources.

chrome/browser/translate/cld_data_harness_factory.cc

Index: chrome/browser/translate/cld_data_harness_factory.cc
diff --git a/chrome/browser/translate/cld_data_harness_factory.cc b/chrome/browser/translate/cld_data_harness_factory.cc
new file mode 100644
index 0000000000000000000000000000000000000000..6ceafc53483c6247833d656ff18a15eac70df775
--- /dev/null
+++ b/chrome/browser/translate/cld_data_harness_factory.cc
@@ -0,0 +1,107 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/translate/cld_data_harness_factory.h"
+
+#include "base/lazy_instance.h"
+#include "chrome/browser/translate/component_cld_data_harness.h"
+#include "chrome/browser/translate/standalone_cld_data_harness.h"
+#include "components/translate/content/browser/browser_cld_utils.h"
+#include "components/translate/content/common/cld_data_source.h"
+
+namespace {
+
+// This is the global instance managed by Get/Set
+test::CldDataHarnessFactory* g_instance = NULL;
+
+// The following three instances are used to "cheat" in Create(). Each of them
+// is just an instance of this class, but because they are singletons they can
+// be compared using "this" to pick different behaviors in Create() at runtime.
+// This avoids the need to explicitly define boilerplate classes with no
+// significant value.
+//
+// Embedders can of course specify a different implementation of this class
+// using Set(CldDataHarnessFactory*), in which case Create() will have whatever
+// custom behavior is desired.
+base::LazyInstance<test::CldDataHarnessFactory>::Leaky g_wrapped_component =
+    LAZY_INSTANCE_INITIALIZER;
+base::LazyInstance<test::CldDataHarnessFactory>::Leaky g_wrapped_standalone =
+    LAZY_INSTANCE_INITIALIZER;
+base::LazyInstance<test::CldDataHarnessFactory>::Leaky g_wrapped_static =
+    LAZY_INSTANCE_INITIALIZER;
+
+}  // namespace
+
+namespace test {
+
+scoped_ptr<CldDataHarness> CldDataHarnessFactory::CreateCldDataHarness() {
+  // Cheat: Since the three "canned" implementations are all well-known, just
+  // check to see if "this" points to one of the singletons and then return
+  // the right answer. Embedder-provided CldDataHarnessFactory implementations
+  // will of course not have this behavior.
+  if (this == GetStaticDataHarnessFactory()) {
+    return CldDataHarness::CreateStaticDataHarness();
+  }
+  if (this == GetStandaloneDataHarnessFactory()) {
+    return CldDataHarness::CreateStandaloneDataHarness();
+  }
+  if (this == GetComponentDataHarnessFactory()) {
+    return CldDataHarness::CreateComponentDataHarness();
+  }
+
+  // Embedder did something wrong, failed to override this method.
+  NOTREACHED() << "Subclass failed to override CreateCldDataHarness()";
+  return CldDataHarness::CreateStaticDataHarness();
+}
+
+CldDataHarnessFactory* CldDataHarnessFactory::Get() {
+  // First honor any factory set by the embedder.
+  if (g_instance != NULL) return g_instance;
+
+  // Fall back to defaults: try to find a compatible harness for the currently-
+  // configured CldDataSource.
+  translate::BrowserCldUtils::ConfigureDefaultDataProvider();
+  if (translate::CldDataSource::IsUsingStaticDataSource()) {
+    return GetStaticDataHarnessFactory();
+  }
+  if (translate::CldDataSource::IsUsingComponentDataSource()) {
+    return GetComponentDataHarnessFactory();
+  }
+  if (translate::CldDataSource::IsUsingStandaloneDataSource()) {
+    return GetStandaloneDataHarnessFactory();
+  }
+
+  // The CldDataSource must have been set by an embedder, but the embedder has
+  // not configured a corresponding CldDataHarnessFactory. This is an error; the
+  // embedder must specify a harness that works with the corresponding
+  // CldDataSource. Crash for debug builds and return a no-op harness for
+  // everything else.
+  NOTREACHED() << "No CLD data harness factory was configured!";
+  return GetStaticDataHarnessFactory();
+}
+
+// static
+void CldDataHarnessFactory::Set(CldDataHarnessFactory* instance) {
+  g_instance = instance;
+}
+
+// static
+CldDataHarnessFactory*
+CldDataHarnessFactory::GetStaticDataHarnessFactory() {
+  return &g_wrapped_static.Get();
+}
+
+// static
+CldDataHarnessFactory*
+CldDataHarnessFactory::GetStandaloneDataHarnessFactory() {
+  return &g_wrapped_standalone.Get();
+}
+
+// static
+CldDataHarnessFactory*
+CldDataHarnessFactory::GetComponentDataHarnessFactory() {
+  return &g_wrapped_component.Get();
+}
+
+}  // namespace test