PkmnLib.NET/Plugins/PkmnLib.Plugin.Gen7.Tests/Scripts/Moves/LightScreenTests.cs

using PkmnLib.Dynamic.Models;
using PkmnLib.Dynamic.ScriptHandling;
using PkmnLib.Dynamic.ScriptHandling.Registry;
using PkmnLib.Plugin.Gen7.Scripts;
using PkmnLib.Plugin.Gen7.Scripts.Moves;
using PkmnLib.Plugin.Gen7.Scripts.Side;
using PkmnLib.Static.Moves;
using PkmnLib.Static.Utils;

namespace PkmnLib.Plugin.Gen7.Tests.Scripts.Moves;

/// <summary>
/// Tests for the <see cref="LightScreen"/> move script and its side effect script
/// <see cref="LightScreenEffect"/>.
/// Gen VII Bulbapedia behavior: Light Screen halves the damage the user's side takes from special moves
/// for 5 turns; "When multiple Pokémon are present on the user's side, special damage reduces by one-third
/// instead of one-half." and "If Light Clay is held when Light Screen is used, it will extend the duration
/// of Light Screen from 5 to 8 turns."
/// </summary>
public class LightScreenTests
{
    /// <summary>
    /// Test helper script that extends the Light Screen duration through the custom trigger, the same way
    /// the Light Clay item script does.
    /// </summary>
    [Script(ScriptCategory.Pokemon, "test_light_screen_duration_extender")]
    private class DurationExtender : Script, IScriptCustomTrigger
    {
        public void CustomTrigger(StringKey eventName, ICustomTriggerArgs args)
        {
            if (eventName == CustomTriggers.LightScreenNumberOfTurns &&
                args is CustomTriggers.LightScreenNumberOfTurnsArgs d)
                d.Duration = 8;
        }
    }

    private static (LightScreen script, IExecutingMove move, IScriptSet sideScripts) CreateMoveSetup()
    {
        var script = new LightScreen();
        var move = Substitute.For<IExecutingMove>();
        move.GetScripts().Returns(_ => new ScriptIterator(new List<IEnumerable<ScriptContainer>>()));

        var sideScripts = Substitute.For<IScriptSet>();
        // Mimic the real ScriptSet: invoke the factory and hand back a container holding the new script.
        sideScripts.StackOrAdd(Arg.Any<StringKey>(), Arg.Any<Func<Script?>>())
            .Returns(ci => new ScriptContainer(ci.Arg<Func<Script?>>()()!));
        var side = Substitute.For<IBattleSide>();
        side.VolatileScripts.Returns(sideScripts);

        var user = Substitute.For<IBattlePokemon>();
        move.User.Returns(user);
        user.BattleSide.Returns(side);

        return (script, move, sideScripts);
    }

    /// <summary>
    /// Helper to extract the effect script instance created through StackOrAdd on the side's volatile
    /// scripts.
    /// </summary>
    private static LightScreenEffect? GetAddedEffect(IScriptSet sideScripts)
    {
        var call = sideScripts.ReceivedCalls().FirstOrDefault(c => c.GetMethodInfo().Name == "StackOrAdd");
        if (call == null)
            return null;
        var factory = (Func<Script?>)call.GetArguments()[1]!;
        return factory() as LightScreenEffect;
    }

    /// <summary>
    /// Hosts the given effect in a real <see cref="ScriptSet"/> and counts how many end-of-turn ticks it
    /// survives, up to the given maximum.
    /// </summary>
    private static int CountSurvivedEndTurns(LightScreenEffect effect, int maximum)
    {
        var owner = Substitute.For<IBattleSide>();
        owner.GetScripts().Returns(_ => new ScriptIterator(Array.Empty<IEnumerable<ScriptContainer>>()));
        IScriptSet set = new ScriptSet(owner);
        set.Add(effect);
        for (var turns = 0; turns < maximum; turns++)
        {
            effect.OnEndTurn(owner, Substitute.For<IBattle>());
            if (!set.Contains(ScriptUtils.ResolveName<LightScreenEffect>()))
                return turns + 1;
        }
        return maximum + 1;
    }

    /// <summary>
    /// Creates a mocked incoming move of the given category for <see cref="LightScreenEffect"/> damage
    /// tests, with the defending target in a battle with the given amount of positions per side.
    /// </summary>
    private static (IExecutingMove move, IBattlePokemon target) CreateIncomingMove(MoveCategory category,
        byte positionsPerSide, bool isCritical = false)
    {
        var move = Substitute.For<IExecutingMove>();
        var moveData = Substitute.For<IMoveData>();
        moveData.Category.Returns(category);
        move.UseMove.Returns(moveData);

        var target = Substitute.For<IBattlePokemon>();
        var hitData = Substitute.For<IHitData>();
        hitData.IsCritical.Returns(isCritical);
        move.GetHitData(target, 0).Returns(hitData);

        var battle = Substitute.For<IBattle>();
        battle.PositionsPerSide.Returns(positionsPerSide);
        target.Battle.Returns(battle);

        return (move, target);
    }

    /// <summary>
    /// Using Light Screen places a <see cref="LightScreenEffect"/> on the user's side of the field.
    /// </summary>
    [Test]
    public async Task OnSecondaryEffect_UserInBattle_AddsLightScreenEffectToUserSide()
    {
        // Arrange
        var (script, move, sideScripts) = CreateMoveSetup();

        // Act
        script.OnSecondaryEffect(move, Substitute.For<IBattlePokemon>(), 0);

        // Assert
        await Assert.That(GetAddedEffect(sideScripts)).IsNotNull();
    }

    /// <summary>
    /// Bulbapedia (Generation II): Light Screen "remains in effect for 5 turns" — the effect placed on the
    /// side expires at the end of the fifth turn.
    /// </summary>
    [Test]
    public async Task OnSecondaryEffect_UserInBattle_EffectLastsFiveTurns()
    {
        // Arrange
        var (script, move, sideScripts) = CreateMoveSetup();

        // Act
        script.OnSecondaryEffect(move, Substitute.For<IBattlePokemon>(), 0);

        // Assert
        var effect = GetAddedEffect(sideScripts);
        await Assert.That(CountSurvivedEndTurns(effect!, 10)).IsEqualTo(5);
    }

    /// <summary>
    /// Bulbapedia: "If Light Clay is held when Light Screen is used, it will extend the duration of Light
    /// Screen from 5 to 8 turns." The extension flows through the LightScreenNumberOfTurns custom trigger;
    /// a script that sets the duration to 8 results in an effect lasting 8 turns.
    /// </summary>
    [Test]
    public async Task OnSecondaryEffect_DurationExtendedByTrigger_EffectLastsEightTurns()
    {
        // Arrange
        var (script, move, sideScripts) = CreateMoveSetup();
        move.GetScripts().Returns(_ => new ScriptIterator(new List<IEnumerable<ScriptContainer>>
        {
            new ScriptContainer(new DurationExtender()),
        }));

        // Act
        script.OnSecondaryEffect(move, Substitute.For<IBattlePokemon>(), 0);

        // Assert
        var effect = GetAddedEffect(sideScripts);
        await Assert.That(CountSurvivedEndTurns(effect!, 10)).IsEqualTo(8);
    }

    /// <summary>
    /// Bulbapedia (Generation III): Light Screen "halves damage from special attacks" — in a single battle
    /// the damage of an incoming special move is halved, with integer truncation.
    /// </summary>
    [Test, Arguments(100u, 50u), Arguments(101u, 50u), Arguments(99u, 49u)]
    public async Task ChangeIncomingMoveDamage_SpecialMoveSingleBattle_DamageHalved(uint damage, uint expectedDamage)
    {
        // Arrange
        var effect = new LightScreenEffect(5);
        var (move, target) = CreateIncomingMove(MoveCategory.Special, 1);

        // Act
        effect.ChangeIncomingMoveDamage(move, target, 0, ref damage);

        // Assert
        await Assert.That(damage).IsEqualTo(expectedDamage);
    }

    /// <summary>
    /// Bulbapedia: "When multiple Pokémon are present on the user's side, special damage reduces by
    /// one-third instead of one-half." — with more than one position per side the damage is multiplied
    /// by 2/3.
    /// </summary>
    [Test, Arguments(90u, 60u), Arguments(100u, 66u)]
    public async Task ChangeIncomingMoveDamage_SpecialMoveMultiBattle_DamageReducedByOneThird(uint damage,
        uint expectedDamage)
    {
        // Arrange
        var effect = new LightScreenEffect(5);
        var (move, target) = CreateIncomingMove(MoveCategory.Special, 2);

        // Act
        effect.ChangeIncomingMoveDamage(move, target, 0, ref damage);

        // Assert
        await Assert.That(damage).IsEqualTo(expectedDamage);
    }

    /// <summary>
    /// Light Screen only reduces damage from special moves — physical move damage is unchanged.
    /// </summary>
    [Test]
    public async Task ChangeIncomingMoveDamage_PhysicalMove_DamageUnchanged()
    {
        // Arrange
        var effect = new LightScreenEffect(5);
        var (move, target) = CreateIncomingMove(MoveCategory.Physical, 1);
        var damage = 100u;

        // Act
        effect.ChangeIncomingMoveDamage(move, target, 0, ref damage);

        // Assert
        await Assert.That(damage).IsEqualTo(100u);
    }

    /// <summary>
    /// Critical hits ignore Light Screen — a critical special move deals full damage through the screen.
    /// </summary>
    [Test]
    public async Task ChangeIncomingMoveDamage_CriticalHit_DamageUnchanged()
    {
        // Arrange
        var effect = new LightScreenEffect(5);
        var (move, target) = CreateIncomingMove(MoveCategory.Special, 1, true);
        var damage = 100u;

        // Act
        effect.ChangeIncomingMoveDamage(move, target, 0, ref damage);

        // Assert
        await Assert.That(damage).IsEqualTo(100u);
    }
}