Merge pull request #36549 from jbytheway/non_synchronous_moon_phases

Non synchronous moon phases

src/calendar.cpp

@@ -59,11 +59,13 @@ double default_daylight_level()
 
 moon_phase get_moon_phase( const time_point &p )
 {
-    //One full phase every 1 rl months = 1/3 season length
-    const time_duration moon_phase_duration = calendar::season_length() / 3.0;
-    //Switch moon phase at noon so it stays the same all night
-    const time_duration current_day = ( p - calendar::turn_zero ) + 1_days / 2;
-    const double phase_change = current_day / moon_phase_duration;
+    static constexpr time_duration synodic_month = 29.530588853 * 1_days;
+    const time_duration moon_phase_duration =
+        calendar::season_from_default_ratio() * synodic_month;
+    // Switch moon phase at noon so it stays the same all night
+    const int num_middays = to_days<int>( p - calendar::turn_zero + 1_days / 2 );
+    const time_duration nearest_midnight = num_middays * 1_days;
+    const double phase_change = nearest_midnight / moon_phase_duration;
     const int current_phase = static_cast<int>( round( phase_change * MOON_PHASE_MAX ) ) %
                               static_cast<int>( MOON_PHASE_MAX );
     return static_cast<moon_phase>( current_phase );
@@ -448,15 +450,16 @@ void calendar::set_season_length( const int dur )
     cur_season_length = dur;
 }
 
+static constexpr int real_world_season_length = 91;
+static constexpr int default_season_length = real_world_season_length;
+
 float calendar::season_ratio()
 {
-    static const int real_world_season_length = 91;
     return to_days<float>( season_length() ) / real_world_season_length;
 }
 
 float calendar::season_from_default_ratio()
 {
-    static const int default_season_length = 91;
     return to_days<float>( season_length() ) / default_season_length;
 }
 

tests/calendar_test.cpp

@@ -0,0 +1,38 @@
+#include "catch/catch.hpp"
+
+#include "calendar.h"
+#include "rng.h"
+#include "stringmaker.h"
+
+TEST_CASE( "moon_phases_take_28_days", "[calendar]" )
+{
+    CAPTURE( calendar::season_length() );
+    // This test only makes sense if the seasons are set to the default length
+    REQUIRE( calendar::season_from_default_ratio() == Approx( 1.0f ) );
+
+    const int num_days = GENERATE( take( 100, random( 0, 1000 ) ) );
+    const time_point first_time = calendar::turn_zero + time_duration::from_days( num_days );
+    const time_point later_14_days = first_time + 14_days;
+    const time_point later_29_days = first_time + 29_days;
+    const time_point later_30_days = first_time + 30_days;
+
+    CAPTURE( num_days );
+    CHECK( get_moon_phase( first_time ) != get_moon_phase( later_14_days ) );
+    // Phase should match either 29 or 30 days later
+    CHECK( ( get_moon_phase( first_time ) == get_moon_phase( later_29_days ) ||
+             get_moon_phase( first_time ) == get_moon_phase( later_30_days ) ) );
+}
+
+TEST_CASE( "moon_phase_changes_at_noon", "[calendar]" )
+{
+    // This test only makes sense if the seasons are set to the default length
+    REQUIRE( calendar::season_from_default_ratio() == Approx( 1.0f ) );
+
+    const int num_days = GENERATE( take( 100, random( 0, 1000 ) ) );
+    const time_point midnight = calendar::turn_zero + time_duration::from_days( num_days );
+    const time_point earlier_11_hours = midnight - 11_hours;
+    const time_point later_11_hours = midnight + 11_hours;
+
+    CAPTURE( num_days );
+    CHECK( get_moon_phase( earlier_11_hours ) == get_moon_phase( later_11_hours ) );
+}

tests/catch/catch.hpp

@@ -4238,6 +4238,7 @@ namespace Catch {
     {
         if( !IMutableContext::currentContext )
             IMutableContext::createContext();
+        // NOLINTNEXTLINE(clang-analyzer-core.uninitialized.UndefReturn)
         return *IMutableContext::currentContext;
     }
 

tests/stringmaker.h

@@ -40,6 +40,13 @@ struct StringMaker<cata_variant> {
     }
 };
 
+template<>
+struct StringMaker<time_duration> {
+    static std::string convert( const time_duration &d ) {
+        return string_format( "time_duration( %d ) [%s]", to_turns<int>( d ), to_string( d ) );
+    }
+};
+
 } // namespace Catch
 
 #endif // CATA_TESTS_STRINGMAKER_H

tests/vision_test.cpp

@@ -460,7 +460,7 @@ TEST_CASE( "vision_wall_can_be_lit_by_player", "[shadowcasting][vision]" )
 
 TEST_CASE( "vision_see_wall_in_moonlight", "[shadowcasting][vision]" )
 {
-    const time_point full_moon = calendar::turn_zero + calendar::season_length() / 3 / 2;
+    const time_point full_moon = calendar::turn_zero + calendar::season_length() / 6;
     // Verify that I've picked the full_moon time correctly.
     CHECK( get_moon_phase( full_moon ) == MOON_FULL );