days - do not stabalize periods spacified in days

weeks - calculate start date for finding period using remainer 400/periodlength to reduce number of iterations (perhaps this ought to follow the same conventio as years months and quarters)

add sample period command tests
add add day period tests for forecasts and budgets
add week period tests for forecasts and budgets - these do not change

1 files changed, 26 insertions, 12 deletions

diff --git a/src/times.cc b/src/times.cc
index b9c8fc01..274abc83 100644
--- a/src/times.cc
+++ b/src/times.cc
@@ -1304,21 +1304,35 @@ void date_interval_t::stabilize(const optional<date_t>& date)
 #endif
 
       date_t when = start ? *start : *date;
-
-      if (duration->quantum == date_duration_t::MONTHS ||
-          duration->quantum == date_duration_t::QUARTERS ||
-          duration->quantum == date_duration_t::YEARS) {
+      switch (duration->quantum) {
+      case date_duration_t::MONTHS:
+      case date_duration_t::QUARTERS:
+      case date_duration_t::YEARS:
+        // These start on most recent period start quantum before when
         DEBUG("times.interval",
-              "stabilize: monthly, quarterly or yearly duration");
+            "stabilize: monthly, quarterly or yearly duration");
         start = date_duration_t::find_nearest(when, duration->quantum);
-      } else {
-        DEBUG("times.interval", "stabilize: daily or weekly duration");
-        start = date_duration_t::find_nearest(when - gregorian::days(400),
-                                              duration->quantum);
+        break;
+      case date_duration_t::WEEKS:
+        // Weeks start on the beginning of week prior to 400 remainder period length
+        // Either the first quanta of the period or the last quanta of the period seems more sensible
+        // implies period is never less than 400 days not too unreasonable
+        DEBUG("times.interval", "stabilize: weekly duration");
+        {
+          int period = duration->length * 7;
+          start = date_duration_t::find_nearest(
+              when - gregorian::days(period + 400 % period), duration->quantum);
+        }
+        break;
+      default:
+        // multiples of days have a quanta of 1 day so should not have the start date adjusted to a quanta
+        DEBUG("times.interval",
+            "stabilize: daily duration - stable by definition");
+        start = when;
+        break;
       }
 
-      DEBUG("times.interval",
-            "stabilize: beginning start date = " << *start);
+      DEBUG("times.interval", "stabilize: beginning start date = " << *start);
 
       while (*start < *date) {
         date_interval_t next_interval(*this);
@@ -1328,7 +1342,7 @@ void date_interval_t::stabilize(const optional<date_t>& date)
           *this = next_interval;
         } else {
           end_of_duration = none;
-          next            = none;
+          next = none;
           break;
         }
       }