[i18n] Replaces fuchsia.deprecatedtimezone

The FIDL library fuchsia.deprecatedtimezone is going away.  There are
different and better ways to obtain the same functionality.

Fixes flutter#39650

Change-Id: If4e4234568c276d3cd2be34863f00165b6e97e0e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/129005
Commit-Queue: Filip Filmar <fmil@google.com>
Reviewed-by: Martin Kustermann <kustermann@google.com>

runtime/vm/BUILD.gn

@@ -70,16 +70,14 @@ library_for_all_configs("libdart_vm") {
   if (is_fuchsia) {
     if (using_fuchsia_sdk) {
       extra_deps += [
-        "$fuchsia_sdk_root/fidl:fuchsia.deprecatedtimezone",
+        "$fuchsia_sdk_root/fidl:fuchsia.intl",
         "$fuchsia_sdk_root/pkg:sys_cpp",
         "$fuchsia_sdk_root/pkg:trace-engine",
       ]
     } else {
       extra_deps += [
-        # TODO(US-399): Remove time_service specific code when it is no longer
-        # necessary.
+        "//sdk/fidl/fuchsia.intl",
         "//sdk/lib/sys/cpp",
-        "//sdk/fidl/fuchsia.deprecatedtimezone",
 
         "//zircon/public/lib/fbl",
         "//zircon/public/lib/trace-engine",

runtime/vm/os_fuchsia.cc

@@ -11,13 +11,16 @@
 #include <fcntl.h>
 #include <stdint.h>
 
-#include <fuchsia/deprecatedtimezone/cpp/fidl.h>
+#include <fuchsia/intl/cpp/fidl.h>
 #include <lib/sys/cpp/service_directory.h>
 #include <zircon/process.h>
 #include <zircon/syscalls.h>
 #include <zircon/syscalls/object.h>
 #include <zircon/types.h>
 
+#include "third_party/icu/source/common/unicode/errorcode.h"
+#include "third_party/icu/source/i18n/unicode/timezone.h"
+
 #include "platform/assert.h"
 #include "vm/zone.h"
 
@@ -61,33 +64,65 @@ intptr_t OS::ProcessId() {
   return static_cast<intptr_t>(getpid());
 }
 
+// This is the default timezone returned if it could not be obtained.  For
+// Fuchsia, the default device timezone is always UTC.
+static const char[] kDefaultTimezone = "UTC";
+
 // TODO(FL-98): Change this to talk to fuchsia.dart to get timezone service to
 // directly get timezone.
 //
 // Putting this hack right now due to CP-120 as I need to remove
 // component:ConnectToEnvironmentServices and this is the only thing that is
 // blocking it and FL-98 will take time.
-static fuchsia::deprecatedtimezone::TimezoneSyncPtr tz;
+static fuchsia::intl::PropertyProviderSyncPtr property_provider;
+
+// 1000 milliseconds do one second make.
+static const int32_t kMSPerSec = 1000;
 
 static zx_status_t GetLocalAndDstOffsetInSeconds(int64_t seconds_since_epoch,
                                                  int32_t* local_offset,
                                                  int32_t* dst_offset) {
-  zx_status_t status = tz->GetTimezoneOffsetMinutes(seconds_since_epoch * 1000,
-                                                    local_offset, dst_offset);
-  if (status != ZX_OK) {
-    return status;
+  const char* timezone_id = GetTimeZoneName(seconds_since_epoch);
+  std::unique_ptr<icu::TimeZone> timezone(
+      icu::TimeZone::createTimeZone(timezone_id));
+  UErrorCode error = U_ZERO_ERROR;
+  const auto ms_since_epoch =
+      static_cast<UDate>(kMSPerSec * seconds_since_epoch);
+  // The units of time that local_offset and dst_offset are returned from this
+  // function is, usefully, not documented, but it seems that the units are
+  // milliseconds.  Add these variables here for clarity.
+  int32_t local_offset_ms = 0;
+  int32_t dst_offset_ms = 0;
+  timezone->getOffset(ms_since_epoch, /*local_time=*/false, local_offset_ms,
+                      dst_offset_ms, error);
+  if (error != U_ZERO_ERROR) {
+    icu::ErrorCode icu_error;
+    icu_error.set(error);
+    // Sadly there is no way to report the actual error.  Next best thing is to
+    // log.  On the upside, a direct call to timezone->getOffset should fail
+    // rarely, so this should not amount to log spam.
+    LOG(ERROR) << "could not get DST offset: " << icu_error.errorName();
+    return ZX_ERR_INTERNAL;
   }
-  *local_offset *= 60;
-  *dst_offset *= 60;
+  // We must return offset in seconds, so convert.
+  *local_offset = local_offset_ms / kMSPerSec;
+  *dst_offset = dst_offset_ms / kMSPerSec;
   return ZX_OK;
 }
 
 const char* OS::GetTimeZoneName(int64_t seconds_since_epoch) {
   // TODO(abarth): Handle time zone changes.
   static const auto* tz_name = new std::string([] {
-    std::string result;
-    tz->GetTimezoneId(&result);
-    return result;
+    fuchsia::intl::Profile profile;
+    zx_status_t status = property_provider->GetProfile(&profile);
+    if (status != ZX_OK) {
+      return kDefaultTimezone;
+    }
+    const std::vector<fuchsia::intl::TimeZoneId>& tzs = profile.time_zones();
+    if (tzs.empty()) {
+      return kDefaultTimezone;
+    }
+    return tzs[0].id;
   }());
   return tz_name->c_str();
 }
@@ -265,7 +300,7 @@ void OS::PrintErr(const char* format, ...) {
 void OS::Init() {
   InitializeTZData();
   auto services = sys::ServiceDirectory::CreateFromNamespace();
-  services->Connect(tz.NewRequest());
+  services->Connect(property_provider.NewRequest());
 }
 
 void OS::Cleanup() {}