Getting started with implementing an explicit AI, based on the Essentials one.

Plugins/PkmnLib.Plugin.Gen7/Scripts/Weather/Hail.cs

@@ -1,7 +1,7 @@
 namespace PkmnLib.Plugin.Gen7.Scripts.Weather;
 
 [Script(ScriptCategory.Weather, "hail")]
-public class Hail : Script, ILimitedTurnsScript, IScriptOnEndTurn
+public class Hail : Script, ILimitedTurnsScript, IScriptOnEndTurn, IAIInfoScriptExpectedEndOfTurnDamage
 {
     private int? _duration;
 
@@ -46,4 +46,15 @@ public class Hail : Script, ILimitedTurnsScript, IScriptOnEndTurn
             battle.SetWeather(null, 0);
         }
     }
+
+    /// <inheritdoc />
+    public void ExpectedEndOfTurnDamage(IPokemon pokemon, ref int damage)
+    {
+        if (pokemon.Types.Any(x => x.Name == "ice"))
+            return; // Ice types are immune to Hail damage.
+        if (_duration.HasValue)
+        {
+            damage += (int)(pokemon.MaxHealth / 16f);
+        }
+    }
 }

Plugins/PkmnLib.Plugin.Gen7/Scripts/Weather/Sandstorm.cs

@@ -1,7 +1,8 @@
 namespace PkmnLib.Plugin.Gen7.Scripts.Weather;
 
 [Script(ScriptCategory.Weather, "sandstorm")]
-public class Sandstorm : Script, IScriptChangeBasePower, IScriptChangeDefensiveStatValue, IScriptOnEndTurn
+public class Sandstorm : Script, IScriptChangeBasePower, IScriptChangeDefensiveStatValue, IScriptOnEndTurn,
+    IAIInfoScriptExpectedEndOfTurnDamage
 {
     /// <inheritdoc />
     public void OnEndTurn(IScriptSource owner, IBattle battle)
@@ -39,4 +40,12 @@ public class Sandstorm : Script, IScriptChangeBasePower, IScriptChangeDefensiveS
         if (move.UseMove.Name == "solar_beam")
             basePower /= 2;
     }
+
+    /// <inheritdoc />
+    public void ExpectedEndOfTurnDamage(IPokemon pokemon, ref int damage)
+    {
+        if (pokemon.Types.Any(x => x.Name == "rock" || x.Name == "ground" || x.Name == "steel"))
+            return; // Rock, Ground, and Steel types are immune to Sandstorm damage.
+        damage += (int)(pokemon.MaxHealth / 16f);
+    }
 }