Implements terrain

Plugins/PkmnLib.Plugin.Gen7/Scripts/Terrain/GrassyTerrain.cs

@@ -3,5 +3,46 @@ namespace PkmnLib.Plugin.Gen7.Scripts.Terrain;
 [Script(ScriptCategory.Terrain, "grassy_terrain")]
 public class GrassyTerrain : Script
 {
-    // TODO: Implement Terrain
+    private static bool IsAffectedByTerrain(IPokemon pokemon) =>
+        !pokemon.IsFloating;
+
+    /// <inheritdoc />
+    public override void ChangeBasePower(IExecutingMove move, IPokemon target, byte hit, ref ushort basePower)
+    {
+        // It boosts the power of Grass-type moves used by affected Pokémon by 50% (regardless of whether the target of
+        // the move is affected by Grassy Terrain).
+        if (IsAffectedByTerrain(move.User))
+        {
+            var type = move.GetHitData(target, hit).Type;
+            if (type?.Name == "grass")
+            {
+                basePower = basePower.MultiplyOrMax(1.5f);
+            }
+        }
+
+        // The power of Bulldoze, Earthquake, and Magnitude is halved against affected targets (regardless of whether the
+        // user of the move is affected by Grassy Terrain).
+        if (IsAffectedByTerrain(target))
+        {
+            var moveName = move.UseMove.Name;
+            if (moveName == "bulldoze" || moveName == "earthquake" || moveName == "magnitude")
+            {
+                basePower /= 2;
+            }
+        }
+    }
+
+    /// <inheritdoc />
+    public override void OnEndTurn(IScriptSource owner, IBattle battle)
+    {
+        // At the end of each turn, Grassy Terrain restores 1/16 of the maximum HP of each affected Pokémon.
+        foreach (var pokemon in battle.Sides.SelectMany(x => x.Pokemon).WhereNotNull())
+        {
+            if (!IsAffectedByTerrain(pokemon) || pokemon.IsFainted)
+                continue;
+
+            var healing = pokemon.MaxHealth / 16f;
+            pokemon.Heal((uint)healing);
+        }
+    }
 }