Implement updateSnowLine (#954)

* Implement initialiseSnowLine and updateSnowLine

* Name ClimateObject variables

* Refactor out common code

src/OpenLoco/Map/MapGenerator.cpp

@@ -491,7 +491,7 @@ namespace OpenLoco::Map::MapGenerator
         updateProgress(5);
 
         Scenario::initialiseDate(options.scenarioStartYear);
-        call(0x00496A18);
+        Scenario::initialiseSnowLine();
         TileManager::initialise();
         updateProgress(10);
 

src/OpenLoco/Objects/ClimateObject.h

@@ -0,0 +1,17 @@
+#pragma once
+
+#include "../Types.hpp"
+
+namespace OpenLoco
+{
+#pragma pack(push, 1)
+    struct ClimateObject
+    {
+        string_id name;          // 0x00
+        uint8_t firstSeason;     // 0x02
+        uint8_t seasonLength[4]; // 0x03
+        uint8_t winterSnowLine;  // 0x07
+        uint8_t summerSnowLine;  // 0x08
+    };
+#pragma pack(pop)
+}

src/OpenLoco/Objects/ObjectManager.cpp

@@ -54,7 +54,7 @@ namespace OpenLoco::ObjectManager
     loco_global<VehicleObject* [224], 0x0050C9E4> _vehicleObjects;
     loco_global<TreeObject* [64], 0x0050CD64> _treeObjects;
     loco_global<SnowObject* [1], 0x0050CE64> _snowObjects;
-    loco_global<climate_object* [1], 0x0050CE68> _climateObjects;
+    loco_global<ClimateObject* [1], 0x0050CE68> _climateObjects;
     loco_global<HillShapesObject* [1], 0x0050CE6C> _hillShapeObjects;
     loco_global<BuildingObject* [128], 0x0050CE70> _buildingObjects;
     loco_global<ScaffoldingObject* [1], 0x0050D070> _scaffoldingObjects;
@@ -282,6 +282,17 @@ namespace OpenLoco::ObjectManager
         return _competitorObjects[id];
     }
 
+    template<>
+    ClimateObject* get()
+    {
+        if (_climateObjects[0] == (void*)-1)
+        {
+            return nullptr;
+        }
+
+        return _climateObjects[0];
+    }
+
     template<>
     ScenarioTextObject* get()
     {

src/OpenLoco/Objects/ObjectManager.h

@@ -83,7 +83,7 @@ namespace OpenLoco
     struct VehicleObject;
     struct TreeObject;
     struct SnowObject;
-    struct climate_object;
+    struct ClimateObject;
     struct HillShapesObject;
     struct BuildingObject;
     struct ScaffoldingObject;

src/OpenLoco/OpenLoco.cpp

@@ -48,6 +48,7 @@
 #include "OpenLoco.h"
 #include "Platform/Platform.h"
 #include "S5/S5.h"
+#include "Scenario.h"
 #include "ScenarioManager.h"
 #include "StationManager.h"
 #include "Title.h"
@@ -857,14 +858,6 @@ namespace OpenLoco
         }
     }
 
-    static void sub_496A84(int32_t edx)
-    {
-        // This is responsible for updating the snow line
-        registers regs;
-        regs.edx = edx;
-        call(0x00496A84, regs);
-    }
-
     static void autosaveReset()
     {
         _monthsSinceLastAutosave = 0;
@@ -983,7 +976,7 @@ namespace OpenLoco
                 auto yesterday = calcDate(getCurrentDay() - 1);
                 auto today = calcDate(getCurrentDay());
                 setDate(today);
-                sub_496A84(today.day_of_olympiad);
+                Scenario::updateSnowLine(today.day_of_olympiad);
                 if (today.month != yesterday.month)
                 {
                     // End of every month

src/OpenLoco/Scenario.cpp

@@ -9,6 +9,7 @@
 #include "Map/MapGenerator.h"
 #include "Map/TileManager.h"
 #include "Objects/CargoObject.h"
+#include "Objects/ClimateObject.h"
 #include "S5/S5.h"
 #include "StationManager.h"
 #include "Title.h"
@@ -25,7 +26,10 @@ namespace OpenLoco::Scenario
     static loco_global<CargoObject*, 0x0050D15C> _50D15C;
 
     static loco_global<uint32_t, 0x00525F5E> _scenario_ticks;
-    static loco_global<uint8_t, 0x00525FB5> _525FB5;
+
+    static loco_global<uint8_t, 0x00525FB4> _currentSnowLine;
+    static loco_global<Season, 0x00525FB5> _currentSeason;
+
     static loco_global<uint16_t, 0x0052622E> _52622E; // tick-related?
 
     static loco_global<uint8_t, 0x00526230> objectiveType;
@@ -50,10 +54,81 @@ namespace OpenLoco::Scenario
         call(0x004C4BC0);
     }
 
-    // 0x00496A18
-    static void sub_496A18()
+    Season nextSeason(Season season)
     {
-        call(0x00496A18);
+        switch (season)
+        {
+            case Season::autumn:
+                return Season::winter;
+            case Season::winter:
+                return Season::spring;
+            case Season::spring:
+                return Season::summer;
+            case Season::summer:
+            default:
+                return Season::autumn;
+        }
+    }
+
+    // 0x00496A18, 0x00496A84 (adapted)
+    static void updateSeason(int32_t currentDayOfYear, const ClimateObject* climateObj)
+    {
+        Season season = static_cast<Season>(climateObj->firstSeason);
+
+        int32_t dayOffset = currentDayOfYear;
+        for (size_t i = 0; i < std::size(climateObj->seasonLength); i++)
+        {
+            dayOffset -= climateObj->seasonLength[i];
+            if (dayOffset < 0)
+                break;
+
+            season = nextSeason(season);
+        }
+
+        _currentSeason = season;
+    }
+
+    // 0x00496A18
+    void initialiseSnowLine()
+    {
+        auto today = calcDate(getCurrentDay());
+        int32_t currentDayOfYear = today.day_of_olympiad;
+
+        auto* climateObj = ObjectManager::get<ClimateObject>();
+        if (climateObj == nullptr)
+            return;
+
+        updateSeason(currentDayOfYear, climateObj);
+
+        if (_currentSeason == Season::winter)
+        {
+            _currentSnowLine = climateObj->winterSnowLine;
+        }
+        else
+        {
+            _currentSnowLine = climateObj->summerSnowLine;
+        }
+    }
+
+    // 0x00496A84
+    void updateSnowLine(int32_t currentDayOfYear)
+    {
+        auto* climateObj = ObjectManager::get<ClimateObject>();
+        if (climateObj == nullptr)
+            return;
+
+        updateSeason(currentDayOfYear, climateObj);
+
+        if (_currentSeason == Season::winter)
+        {
+            if (_currentSnowLine != climateObj->winterSnowLine)
+                _currentSnowLine--;
+        }
+        else
+        {
+            if (_currentSnowLine != climateObj->summerSnowLine)
+                _currentSnowLine++;
+        }
     }
 
     // 0x00475988
@@ -105,8 +180,7 @@ namespace OpenLoco::Scenario
         sub_4C4BC0();
 
         initialiseDate(1900);
-
-        sub_496A18();
+        initialiseSnowLine();
         sub_475988();
         TownManager::reset();
         IndustryManager::reset();
@@ -164,7 +238,7 @@ namespace OpenLoco::Scenario
 
         _scenario_ticks = 0;
         _52622E = 0;
-        _525FB5 = 1;
+        _currentSeason = Season::winter;
 
         CompanyManager::determineAvailableVehicles();
 

src/OpenLoco/Scenario.h

@@ -34,6 +34,14 @@ namespace OpenLoco::Scenario
         cargo_delivery,
     };
 
+    enum class Season : uint8_t
+    {
+        autumn = 0,
+        winter = 1,
+        spring = 2,
+        summer = 3,
+    };
+
     // NB: min_year has been changed to 1800 in OpenLoco; Locomotion uses 1900.
     constexpr uint16_t min_year = 1800;
     constexpr uint16_t max_year = 2100;
@@ -92,6 +100,9 @@ namespace OpenLoco::Scenario
     constexpr uint8_t min_altitude_trees = 0;
     constexpr uint8_t max_altitude_trees = 40;
 
+    Season nextSeason(Season season);
+    void initialiseSnowLine();
+    void updateSnowLine(int32_t currentDayOfYear);
     void reset();
     void sub_4748D4();
     void eraseLandscape();