Implements accuracy/evasion

Plugins/PkmnLib.Plugin.Gen7/Libraries/Gen7BattleStatCalculator.cs

@@ -1,5 +1,7 @@
+using System;
 using PkmnLib.Dynamic.Libraries;
 using PkmnLib.Dynamic.Models;
+using PkmnLib.Dynamic.ScriptHandling;
 using PkmnLib.Static;
 
 namespace PkmnLib.Plugin.Gen7.Libraries;
@@ -48,6 +50,33 @@ public class Gen7BattleStatCalculator : IBattleStatCalculator
         return (uint)boostedStat;
     }
 
+    /// <inheritdoc />
+    public byte CalculateModifiedAccuracy(IExecutingMove executingMove, IPokemon target, byte hitIndex, byte moveAccuracy)
+    {
+        var accuracyModifier = 1.0f;
+        executingMove.RunScriptHook(x => x.ChangeAccuracyModifier(executingMove, target, hitIndex, ref accuracyModifier));
+        var modifiedAccuracy = (int)(moveAccuracy * accuracyModifier);
+        var targetEvasion = target.StatBoost.Evasion;
+        var userAccuracy = executingMove.User.StatBoost.Accuracy;
+        var difference = targetEvasion - userAccuracy;
+        var statModifier = difference switch
+        {
+            > 0 => 3.0f / (3.0f + difference),
+            < 0 => 3.0f + Math.Abs(difference) / 3.0f,
+            _ => 1.0f
+        };
+        modifiedAccuracy = (int)(modifiedAccuracy * statModifier);
+        modifiedAccuracy = modifiedAccuracy switch
+        {
+            > 255 => 255,
+            < 0 => 0,
+            _ => modifiedAccuracy
+        };
+        // NOTE: the main games also consider friendship here, but we don't yet have the concept of a "player Pokémon"
+        //       in the battle system, so for now we're just ignoring that.
+        return (byte)modifiedAccuracy;
+    }
+
     private static uint CalculateHealthStat(IPokemon pokemon)
     {
         var baseValue = (ulong)pokemon.Form.BaseStats.Hp;

Plugins/PkmnLib.Plugin.Gen7/Scripts/Side/AuroraVeilEffect.cs

@@ -27,6 +27,8 @@ namespace PkmnLib.Plugin.Gen7.Scripts.Side;
 public class AuroraVeilEffect : Script
 {
     public int NumberOfTurns { get; set; }
+    
+    private AuroraVeilEffect(){}
 
     public AuroraVeilEffect(int numberOfTurns)
     {