More abilities, refactor custom triggers to be typed.

Plugins/PkmnLib.Plugin.Gen7/Scripts/Abilities/MistySurge.cs

@@ -0,0 +1,28 @@
+namespace PkmnLib.Plugin.Gen7.Scripts.Abilities;
+
+/// <summary>
+/// Misty Surge is an ability that creates Misty Terrain when the Pokémon enters battle.
+///
+/// <see href="https://bulbapedia.bulbagarden.net/wiki/Misty_Surge_(Ability)">Bulbapedia - Misty Surge</see>
+/// </summary>
+[Script(ScriptCategory.Ability, "misty_surge")]
+public class MistySurge : Script
+{
+    /// <inheritdoc />
+    public override void OnSwitchIn(IPokemon pokemon, byte position)
+    {
+        if (pokemon.BattleData?.Battle is null)
+            return;
+
+        var terrainName = ScriptUtils.ResolveName<Terrain.MistyTerrain>();
+        if (pokemon.BattleData.Battle.TerrainName == terrainName)
+            return;
+
+        EventBatchId batchId = new();
+        pokemon.BattleData.Battle.EventHook.Invoke(new AbilityTriggerEvent(pokemon)
+        {
+            BatchId = batchId,
+        });
+        pokemon.BattleData.Battle.SetTerrain(terrainName, batchId);
+    }
+}