feat universal: add optional string to datetime parser

add optional string to datetime parser

Tests: протестировано utest
d3e81113f213a3c4a1cb14061c66d244205d1ace

Author: vitaly2020

universal/include/userver/utils/datetime.hpp

@@ -5,6 +5,7 @@
 /// @ingroup userver_universal
 
 #include <chrono>
+#include <optional>
 #include <stdexcept>
 #include <string>
 
@@ -138,6 +139,16 @@ std::chrono::system_clock::time_point GuessStringtime(
 std::chrono::system_clock::time_point GuessLocalTimezoneStringtime(
     const std::string& timestamp);
 
+/// @brief Returns optional time in a string of specified format
+/// Example:
+/// @snippet utils/datetime/datetime_test.cpp OptionalTimestring example
+/// @see kRfc3339Format, kTaximeterFormat, kStartOfTheEpoch,
+/// kDefaultDriverTimezone, kDefaultTimezone, kDefaultFormat, kIsoFormat
+std::optional<std::chrono::system_clock::time_point> OptionalStringtime(
+    const std::string& timestring,
+    const std::string& timezone = kDefaultTimezone,
+    const std::string& format = kDefaultFormat);
+
 /// @brief Converts time point to std::time_t
 /// Example:
 /// @snippet utils/datetime/datetime_test.cpp  Timestring C time example

universal/src/utils/datetime.cpp

@@ -28,17 +28,25 @@ constexpr int64_t k100NanosecondsIntervalsBetweenDotNetAndPosixTimeStart =
     62135596800L * 10000000L;  // sec to 100nanosec
 constexpr int64_t kNanosecondsIs100Nanoseconds = 100;
 
-cctz::time_zone GetTimezone(const std::string& tzname) {
+std::optional<cctz::time_zone> GetOptionalTimezone(const std::string& tzname) {
 #if defined(BSD) && !defined(__APPLE__)
-  if (tzname == "GMT") return GetTimezone("UTC");
+  if (tzname == "GMT") return GetOptionalTimezone("UTC");
 #endif
   cctz::time_zone tz;
   if (!load_time_zone(tzname, &tz)) {
-    throw TimezoneLookupError(tzname);
+    return std::nullopt;
   }
   return tz;
 }
 
+cctz::time_zone GetTimezone(const std::string& tzname) {
+  auto tz = GetOptionalTimezone(tzname);
+  if (!tz.has_value()) {
+    throw TimezoneLookupError(tzname);
+  }
+  return *tz;
+}
+
 const cctz::time_zone& GetLocalTimezone() {
   static const cctz::time_zone kLocalTz = cctz::local_time_zone();
   return kLocalTz;
@@ -107,6 +115,16 @@ std::string Timestring(std::chrono::system_clock::time_point tp,
   return cctz::format(format, tp, GetTimezone(timezone));
 }
 
+std::optional<std::chrono::system_clock::time_point> OptionalStringtime(
+    const std::string& timestring, const std::string& timezone,
+    const std::string& format) {
+  auto tz = GetOptionalTimezone(timezone);
+  if (!tz.has_value()) {
+    return std::nullopt;
+  }
+  return OptionalStringtime(timestring, *tz, format);
+}
+
 std::string LocalTimezoneTimestring(std::chrono::system_clock::time_point tp,
                                     const std::string& format) {
   return cctz::format(format, tp, GetLocalTimezone());

universal/src/utils/datetime/datetime_test.cpp

@@ -16,6 +16,15 @@ TEST(Datetime, Stringtime) {
   /// [Stringtime example]
 }
 
+TEST(Datetime, OptionalStringtime) {
+  /// [OptionalStringtime example]
+  const auto tp = utils::datetime::Stringtime("2014-03-17T02:47:07+0000");
+  EXPECT_EQ(
+      utils::datetime::OptionalStringtime("2014-03-17T02:47:07+0000").value(),
+      tp);
+  /// [OptionalStringtime example]
+}
+
 TEST(Datetime, Timestring) {
   /// [Timestring example]
   const auto tp = utils::datetime::Stringtime("2014-03-17T02:47:07+0000");
@@ -81,6 +90,19 @@ TEST(Datetime, kDefaultTimezone) {
   /// [kDefaultTimezone]
 }
 
+TEST(Datetime, kIncorrectDatetimeFormat) {
+  /// [kIncorrectDatetimeFormat]
+  EXPECT_FALSE(utils::datetime::OptionalStringtime("20140317T02:47:07+0000")
+                   .has_value());
+  /// [kIncorrectDatetimeFormat]
+}
+
+TEST(Datetime, kEmptyDatetime) {
+  /// [kEmptyDatetime]
+  EXPECT_FALSE(utils::datetime::OptionalStringtime("").has_value());
+  /// [kEmptyDatetime]
+}
+
 }  // namespace
 
 USERVER_NAMESPACE_END