Add initial implementation of game mechanics and resources management

Scripts/Core/Effects/ConvertResourceEffect.cs

@@ -0,0 +1,36 @@
+using Godot;
+
+namespace ParasiticGod.Scripts.Core.Effects;
+
+[GlobalClass]
+public partial class ConvertResourceEffect : Effect
+{
+    [Export] public ResourceType FromResource { get; set; }
+    [Export] public double FromAmount { get; set; }
+    [Export] public ResourceType ToResource { get; set; }
+    [Export] public double ToAmount { get; set; }
+    
+    public override void Execute(GameState gameState)
+    {
+        double GetValue(ResourceType type) => type switch {
+            ResourceType.Faith => gameState.Faith,
+            ResourceType.Followers => gameState.Followers,
+            ResourceType.Corruption => gameState.Corruption,
+            _ => 0
+        };
+        
+        void SetValue(ResourceType type, double value) {
+            switch(type) {
+                case ResourceType.Faith: gameState.Faith = value; break;
+                case ResourceType.Followers: gameState.Followers = (long)value; break;
+                case ResourceType.Corruption: gameState.Corruption = value; break;
+            }
+        }
+
+        if (GetValue(FromResource) >= FromAmount)
+        {
+            SetValue(FromResource, GetValue(FromResource) - FromAmount);
+            SetValue(ToResource, GetValue(ToResource) + ToAmount);
+        }
+    }
+}