fixes #471 (#481)

Expand fix for ja era to handle months and days

src/CalcViewModel/Common/DateCalculator.cpp

@@ -26,21 +26,19 @@ bool DateCalculationEngine::AddDuration(_In_ DateTime startDate, _In_ const Date
     {
         m_calendar->SetDateTime(startDate);
 
+        // The Japanese Era system can have multiple year partitions within the same year.
+        // For example, April 30, 2019 is denoted April 30, Heisei 31; May 1, 2019 is denoted as May 1, Reiwa 1.
+        // The Calendar treats Heisei 31 and Reiwa 1 as separate years, which results in some unexpected behaviors where subtracting a year from Reiwa 1 results in a date in Heisei 31.
+        // To provide the expected result across era boundaries, we first convert the Japanese era system to a Gregorian system, do date math, and then convert back to the Japanese era system.
+        // This works because the Japanese era system maintains the same year/month boundaries and durations as the Gregorian system and is only different in display value.
+        if (currentCalendarSystem == CalendarIdentifiers::Japanese)
+        {
+            m_calendar->ChangeCalendarSystem(CalendarIdentifiers::Gregorian);
+        }
+
         if (duration.year != 0)
         {
-            // The Japanese Era system can have multiple year partitions within the same year.
-            // For example, April 30, 2019 is denoted April 30, Heisei 31; May 1, 2019 is denoted as May 1, Reiwa 1.
-            // The Calendar treats Heisei 31 and Reiwa 1 as separate years, which results in some unexpected behaviors where subtracting a year from Reiwa 1 results in a date in Heisei 31.
-            // To provide the expected result across era boundaries, we first convert the Japanese era system to a Gregorian system, do date math, and then convert back to the Japanese era system.
-            // This works because the Japanese era system maintains the same year/month boundaries and durations as the Gregorian system and is only different in display value.
-            if (currentCalendarSystem == CalendarIdentifiers::Japanese)
-            {
-                m_calendar->ChangeCalendarSystem(CalendarIdentifiers::Gregorian);
-            }
-
             m_calendar->AddYears(duration.year);
-
-            m_calendar->ChangeCalendarSystem(currentCalendarSystem);
         }
         if (duration.month != 0)
         {
@@ -62,6 +60,8 @@ bool DateCalculationEngine::AddDuration(_In_ DateTime startDate, _In_ const Date
         return false;
     }
 
+    m_calendar->ChangeCalendarSystem(currentCalendarSystem);
+
     return true;
 }
 
@@ -77,6 +77,16 @@ bool DateCalculationEngine::SubtractDuration(_In_ DateTime startDate, _In_ const
     {
         m_calendar->SetDateTime(startDate);
 
+        // The Japanese Era system can have multiple year partitions within the same year.
+        // For example, April 30, 2019 is denoted April 30, Heisei 31; May 1, 2019 is denoted as May 1, Reiwa 1.
+        // The Calendar treats Heisei 31 and Reiwa 1 as separate years, which results in some unexpected behaviors where subtracting a year from Reiwa 1 results in a date in Heisei 31.
+        // To provide the expected result across era boundaries, we first convert the Japanese era system to a Gregorian system, do date math, and then convert back to the Japanese era system.
+        // This works because the Japanese era system maintains the same year/month boundaries and durations as the Gregorian system and is only different in display value.
+        if (currentCalendarSystem == CalendarIdentifiers::Japanese)
+        {
+            m_calendar->ChangeCalendarSystem(CalendarIdentifiers::Gregorian);
+        }
+
         if (duration.day != 0)
         {
             m_calendar->AddDays(-duration.day);
@@ -87,21 +97,8 @@ bool DateCalculationEngine::SubtractDuration(_In_ DateTime startDate, _In_ const
         }
         if (duration.year != 0)
         {
-            // The Japanese Era system can have multiple year partitions within the same year.
-            // For example, April 30, 2019 is denoted April 30, Heisei 31; May 1, 2019 is denoted as May 1, Reiwa 1.
-            // The Calendar treats Heisei 31 and Reiwa 1 as separate years, which results in some unexpected behaviors where subtracting a year from Reiwa 1 results in a date in Heisei 31.
-            // To provide the expected result across era boundaries, we first convert the Japanese era system to a Gregorian system, do date math, and then convert back to the Japanese era system.
-            // This works because the Japanese era system maintains the same year/month boundaries and durations as the Gregorian system and is only different in display value.
-            if (currentCalendarSystem == CalendarIdentifiers::Japanese)
-            {
-                m_calendar->ChangeCalendarSystem(CalendarIdentifiers::Gregorian);
-            }
-
             m_calendar->AddYears(-duration.year);
-
-            m_calendar->ChangeCalendarSystem(currentCalendarSystem);
         }
-
         *endDate = m_calendar->GetDateTime();
     }
     catch (Platform::InvalidArgumentException^ ex)
@@ -113,6 +110,8 @@ bool DateCalculationEngine::SubtractDuration(_In_ DateTime startDate, _In_ const
         return false;
     }
 
+    m_calendar->ChangeCalendarSystem(currentCalendarSystem);
+
     // Check that the UniversalTime value is not negative
     return (endDate->UniversalTime >= 0);
 }
@@ -308,27 +307,24 @@ bool DateCalculationEngine::TryGetCalendarDaysInYear(_In_ DateTime date, _Out_ U
 // Adds/Subtracts certain value for a particular date unit
 DateTime DateCalculationEngine::AdjustCalendarDate(Windows::Foundation::DateTime date, DateUnit dateUnit, int difference)
 {
-
     m_calendar->SetDateTime(date);
 
+    // The Japanese Era system can have multiple year partitions within the same year.
+    // For example, April 30, 2019 is denoted April 30, Heisei 31; May 1, 2019 is denoted as May 1, Reiwa 1.
+    // The Calendar treats Heisei 31 and Reiwa 1 as separate years, which results in some unexpected behaviors where subtracting a year from Reiwa 1 results in a date in Heisei 31.
+    // To provide the expected result across era boundaries, we first convert the Japanese era system to a Gregorian system, do date math, and then convert back to the Japanese era system.
+    // This works because the Japanese era system maintains the same year/month boundaries and durations as the Gregorian system and is only different in display value.
+    auto currentCalendarSystem = m_calendar->GetCalendarSystem();
+    if (currentCalendarSystem == CalendarIdentifiers::Japanese)
+    {
+        m_calendar->ChangeCalendarSystem(CalendarIdentifiers::Gregorian);
+    }
+
     switch (dateUnit)
     {
         case DateUnit::Year:
-        {
-            // In the Japanese calendar, transition years have 2 partial years.
-            // It is not guaranteed that adding 1 year will always add 365 days in the Japanese Calendar.
-            // To work around this quirk, we will change the calendar system to Gregorian before adding 1 year in the Japanese Calendar case only.
-            // We will then return the calendar system back to the Japanese Calendar.
-            auto currentCalendarSystem = m_calendar->GetCalendarSystem();
-            if (currentCalendarSystem == CalendarIdentifiers::Japanese)
-            {
-                m_calendar->ChangeCalendarSystem(CalendarIdentifiers::Gregorian);
-            }
-
             m_calendar->AddYears(difference);
-            m_calendar->ChangeCalendarSystem(currentCalendarSystem);
             break;
-        }
         case DateUnit::Month:
             m_calendar->AddMonths(difference);
             break;
@@ -337,5 +333,7 @@ DateTime DateCalculationEngine::AdjustCalendarDate(Windows::Foundation::DateTime
             break;
     }
 
+    m_calendar->ChangeCalendarSystem(currentCalendarSystem);
+
     return m_calendar->GetDateTime();
 }

src/CalculatorUnitTests/DateCalculatorUnitTests.cpp

@@ -670,7 +670,7 @@ namespace DateCalculationUnitTests
             auto viewModel = make_unique<DateCalculationEngine>(CalendarIdentifiers::Japanese);
             auto cal = ref new Calendar();
 
-            // Showa period ended in Jan 1989.
+            // The Showa period ended in Jan 1989.
             cal->Year = 1989;
             cal->Month = 1;
             cal->Day = 1;
@@ -681,14 +681,28 @@ namespace DateCalculationUnitTests
             cal->Day = 1;
 
             // Expect that adding a year across boundaries adds the equivalent in the Gregorian calendar.
-            auto expectedResult = cal->GetDateTime();
+            auto expectedYearResult = cal->GetDateTime();
-            DateDifference duration;
+            DateDifference yearDuration;
-            duration.year = 1;
+            yearDuration.year = 1;
 
-            DateTime actualResult;
+            DateTime actualYearResult;
-            viewModel->AddDuration(startTime, duration, &actualResult);
+            viewModel->AddDuration(startTime, yearDuration, &actualYearResult);
 
-            VERIFY_ARE_EQUAL(expectedResult.UniversalTime, actualResult.UniversalTime);
+            VERIFY_ARE_EQUAL(expectedYearResult.UniversalTime, actualYearResult.UniversalTime);
+
+            cal->Year = 1989;
+            cal->Month = 2;
+            cal->Day = 1;
+
+            // Expect that adding a month across boundaries adds the equivalent in the Gregorian calendar.
+            auto expectedMonthResult = cal->GetDateTime();
+            DateDifference monthDuration;
+            monthDuration.month = 1;
+
+            DateTime actualMonthResult;
+            viewModel->AddDuration(startTime, monthDuration, &actualMonthResult);
+
+            VERIFY_ARE_EQUAL(expectedMonthResult.UniversalTime, actualMonthResult.UniversalTime);
         }
 
         TEST_METHOD(JaEraTransitionSubtraction)
@@ -696,25 +710,61 @@ namespace DateCalculationUnitTests
             auto viewModel = make_unique<DateCalculationEngine>(CalendarIdentifiers::Japanese);
             auto cal = ref new Calendar();
 
-            // Showa period ended in Jan 1989.
+            // The Showa period ended in Jan 1989.
-            cal->Year = 1990;
+            cal->Year = 1989;
+            cal->Month = 2;
+            cal->Day = 1;
+            auto startTime = cal->GetDateTime();
+
+            cal->Year = 1988;
+            cal->Month = 2;
+            cal->Day = 1;
+
+            // Expect that adding a year across boundaries adds the equivalent in the Gregorian calendar.
+            auto expectedYearResult = cal->GetDateTime();
+            DateDifference yearDuration;
+            yearDuration.year = 1;
+
+            DateTime actualYearResult;
+            viewModel->SubtractDuration(startTime, yearDuration, &actualYearResult);
+
+            VERIFY_ARE_EQUAL(expectedYearResult.UniversalTime, actualYearResult.UniversalTime);
+
+            cal->Year = 1989;
+            cal->Month = 1;
+            cal->Day = 1;
+
+            // Expect that adding a month across boundaries adds the equivalent in the Gregorian calendar.
+            auto expectedMonthResult = cal->GetDateTime();
+            DateDifference monthDuration;
+            monthDuration.month = 1;
+
+            DateTime actualMonthResult;
+            viewModel->SubtractDuration(startTime, monthDuration, &actualMonthResult);
+
+            VERIFY_ARE_EQUAL(expectedMonthResult.UniversalTime, actualMonthResult.UniversalTime);
+        }
+
+        TEST_METHOD(JaEraTransitionDifference)
+        {
+            auto viewModel = make_unique<DateCalculationEngine>(CalendarIdentifiers::Japanese);
+            auto cal = ref new Calendar();
+
+            // The Showa period ended in Jan 8, 1989.  Pick 2 days across that boundary
+            cal->Year = 1989;
             cal->Month = 1;
             cal->Day = 1;
             auto startTime = cal->GetDateTime();
 
             cal->Year = 1989;
             cal->Month = 1;
-            cal->Day = 1;
+            cal->Day = 20;
+            auto endTime = cal->GetDateTime();
 
-            // Expect that adding a year across boundaries adds the equivalent in the Gregorian calendar.
+            DateDifference diff;
-            auto expectedResult = cal->GetDateTime();
+            viewModel->GetDateDifference(startTime, endTime, DateUnit::Day, &diff);
-            DateDifference duration;
-            duration.year = 1;
 
-            DateTime actualResult;
+            VERIFY_ARE_EQUAL(diff.day, 19);
-            viewModel->SubtractDuration(startTime, duration, &actualResult);
-
-            VERIFY_ARE_EQUAL(expectedResult.UniversalTime, actualResult.UniversalTime);
         }
     };
 }