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

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

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

/// <summary>
/// Tests for the <see cref="MirrorCoat"/> move script.
/// Gen VII Bulbapedia behavior: "If the last amount of damage done to the user before the use of Mirror
/// Coat is greater than 0 and was dealt by a special move, Mirror Coat will do twice as much damage as
/// taken by that attack to the opponent." Mirror Coat fails if the user was not hit, or was last hit by
/// a physical move.
/// The turn-scoped bookkeeping is implemented by a private "mirror_coat_helper" volatile script that the
/// move script attaches to its user at the start of the turn; because that helper type is private, it is
/// driven here through its <see cref="IScriptOnIncomingHit"/> and <see cref="IScriptOnEndTurn"/>
/// interfaces after retrieving it from the user's volatile script set.
/// </summary>
public class MirrorCoatTests
{
    private static readonly StringKey HelperName = "mirror_coat_helper";

    /// <summary>
    /// Creates a Pokémon substitute with a real (empty) volatile script set, so that volatile lookups
    /// behave like they would on a real Pokémon.
    /// </summary>
    private static IPokemon CreatePokemonWithEmptyVolatile()
    {
        var pokemon = Substitute.For<IPokemon>();
        var volatileSet = new ScriptSet(pokemon);
        pokemon.Volatile.Returns(volatileSet);
        pokemon.GetScripts().Returns(_ => new ScriptIterator(new List<IEnumerable<ScriptContainer>>()));
        return pokemon;
    }

    /// <summary>
    /// Creates a Mirror Coat user that has declared Mirror Coat this turn: <see cref="MirrorCoat"/>'s
    /// <c>OnBeforeTurnStart</c> has run, so the helper volatile script is attached to the user.
    /// </summary>
    private static (MirrorCoat script, IPokemon user) CreateMirrorCoatUser()
    {
        var script = new MirrorCoat();
        var user = CreatePokemonWithEmptyVolatile();
        var choice = Substitute.For<IMoveChoice>();
        choice.User.Returns(user);
        script.OnBeforeTurnStart(choice);
        return (script, user);
    }

    /// <summary>
    /// Simulates the user being hit by a move of the given category dealing the given damage, by invoking
    /// the helper volatile script's <see cref="IScriptOnIncomingHit.OnIncomingHit"/> hook.
    /// </summary>
    private static void ReceiveHit(IPokemon user, IPokemon attacker, uint damage,
        MoveCategory category = MoveCategory.Special)
    {
        var incoming = Substitute.For<IExecutingMove>();
        var useMove = Substitute.For<IMoveData>();
        useMove.Category.Returns(category);
        incoming.UseMove.Returns(useMove);
        incoming.User.Returns(attacker);
        var hitData = Substitute.For<IHitData>();
        hitData.Damage.Returns(damage);
        incoming.GetHitData(user, 0).Returns(hitData);

        var helper = (IScriptOnIncomingHit)user.Volatile.Get(HelperName)!.Script!;
        helper.OnIncomingHit(incoming, user, 0);
    }

    /// <summary>
    /// Creates the executing Mirror Coat move of <paramref name="user"/> against <paramref name="target"/>.
    /// </summary>
    private static (IExecutingMove move, IHitData hitData) CreateExecutingMirrorCoat(IPokemon user, IPokemon target)
    {
        var move = Substitute.For<IExecutingMove>();
        move.User.Returns(user);
        var hitData = Substitute.For<IHitData>();
        move.GetHitData(target, 0).Returns(hitData);
        return (move, hitData);
    }

    /// <summary>
    /// Bulbapedia: "If the last amount of damage done to the user before the use of Mirror Coat is
    /// greater than 0 and was dealt by a special move, Mirror Coat will do twice as much damage as taken
    /// by that attack to the opponent."
    /// Mirror Coat watches for those hits over the whole turn: at the start of the turn it attaches its
    /// helper volatile script to the user.
    /// </summary>
    [Test]
    public async Task OnBeforeTurnStart_Always_AddsMirrorCoatHelperToUser()
    {
        // Arrange & Act
        var (_, user) = CreateMirrorCoatUser();

        // Assert
        await Assert.That(user.Volatile.Contains(HelperName)).IsTrue();
    }

    /// <summary>
    /// Bulbapedia: "If the last amount of damage done to the user before the use of Mirror Coat is
    /// greater than 0 and was dealt by a special move, Mirror Coat will do twice as much damage as taken
    /// by that attack to the opponent."
    /// </summary>
    [Test, Arguments(40u, 80u), Arguments(1u, 2u), Arguments(123u, 246u)]
    public async Task ChangeMoveDamage_UserHitBySpecialMove_DealsDoubleTheDamageTaken(uint damageTaken,
        uint expectedDamage)
    {
        // Arrange
        var (script, user) = CreateMirrorCoatUser();
        var attacker = CreatePokemonWithEmptyVolatile();
        ReceiveHit(user, attacker, damageTaken);
        var (move, hitData) = CreateExecutingMirrorCoat(user, attacker);
        uint damage = 0;

        // Act
        script.ChangeMoveDamage(move, attacker, 0, ref damage);

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

    /// <summary>
    /// Bulbapedia: if the user "is hit multiple times by a multistrike move", only the final strike is
    /// countered — the helper records the most recent hit, so Mirror Coat returns double the damage of
    /// the last strike only.
    /// </summary>
    [Test]
    public async Task ChangeMoveDamage_UserHitMultipleTimes_CountersOnlyTheLastHit()
    {
        // Arrange
        var (script, user) = CreateMirrorCoatUser();
        var attacker = CreatePokemonWithEmptyVolatile();
        ReceiveHit(user, attacker, 30);
        ReceiveHit(user, attacker, 50);
        var (move, _) = CreateExecutingMirrorCoat(user, attacker);
        uint damage = 0;

        // Act
        script.ChangeMoveDamage(move, attacker, 0, ref damage);

        // Assert - double the last hit (50), not the first (30) or the sum
        await Assert.That(damage).IsEqualTo(100u);
    }

    /// <summary>
    /// Bulbapedia: Mirror Coat fails if the user was not hit by an attack before it executes ("If the
    /// last amount of damage done to the user before the use of Mirror Coat is greater than 0...").
    /// </summary>
    [Test]
    public async Task ChangeMoveDamage_UserNotHitThisTurn_FailsHit()
    {
        // Arrange
        var (script, user) = CreateMirrorCoatUser();
        var target = CreatePokemonWithEmptyVolatile();
        var (move, hitData) = CreateExecutingMirrorCoat(user, target);
        uint damage = 0;

        // Act
        script.ChangeMoveDamage(move, target, 0, ref damage);

        // Assert
        hitData.Received(1).Fail();
        await Assert.That(damage).IsEqualTo(0u);
    }

    /// <summary>
    /// Bulbapedia: Mirror Coat only counters special moves ("...and was dealt by a special move");
    /// it fails when the user was hit by a physical move instead.
    /// </summary>
    [Test]
    public async Task ChangeMoveDamage_UserHitByPhysicalMoveOnly_FailsHit()
    {
        // Arrange
        var (script, user) = CreateMirrorCoatUser();
        var attacker = CreatePokemonWithEmptyVolatile();
        ReceiveHit(user, attacker, 40, MoveCategory.Physical);
        var (move, hitData) = CreateExecutingMirrorCoat(user, attacker);
        uint damage = 0;

        // Act
        script.ChangeMoveDamage(move, attacker, 0, ref damage);

        // Assert
        hitData.Received(1).Fail();
        await Assert.That(damage).IsEqualTo(0u);
    }

    /// <summary>
    /// Bulbapedia: "Mirror Coat will target the last opponent that dealt special damage to the attacker" —
    /// against any Pokémon other than that last attacker, the hit fails.
    /// </summary>
    [Test]
    public async Task ChangeMoveDamage_TargetIsNotTheLastAttacker_FailsHit()
    {
        // Arrange
        var (script, user) = CreateMirrorCoatUser();
        var attacker = CreatePokemonWithEmptyVolatile();
        ReceiveHit(user, attacker, 40);
        var someoneElse = CreatePokemonWithEmptyVolatile();
        var (move, hitData) = CreateExecutingMirrorCoat(user, someoneElse);
        uint damage = 0;

        // Act
        script.ChangeMoveDamage(move, someoneElse, 0, ref damage);

        // Assert
        hitData.Received(1).Fail();
        await Assert.That(damage).IsEqualTo(0u);
    }

    /// <summary>
    /// Bulbapedia: "Mirror Coat will target the last opponent that dealt special damage to the attacker" —
    /// like <see cref="Counter"/>, the script must implement <see cref="IScriptChangeTargets"/> and redirect
    /// the move at the Pokémon whose special move last damaged the user.
    /// </summary>
    [Test]
    public async Task ChangeTargets_UserHitBySpecialMove_RedirectsToLastSpecialAttacker()
    {
        // Arrange
        var (script, user) = CreateMirrorCoatUser();
        var attacker = CreatePokemonWithEmptyVolatile();
        ReceiveHit(user, attacker, 40);
        var choice = Substitute.For<IMoveChoice>();
        choice.User.Returns(user);
        IReadOnlyList<IPokemon?> targets = [CreatePokemonWithEmptyVolatile()];

        // Act & Assert - the script must expose the redirection hook and point the move at the attacker
        var changeTargets = script as IScriptChangeTargets;
        await Assert.That(changeTargets).IsNotNull();
        changeTargets!.ChangeTargets(choice, ref targets);
        await Assert.That(targets.Count).IsEqualTo(1);
        await Assert.That(targets[0]).IsEqualTo(attacker);
    }

    /// <summary>
    /// Bulbapedia (Generation IV onwards): "If the Pokémon using Mirror Coat is hit by a special move that
    /// deals 0 damage, Mirror Coat becomes a special move with 1 base power." Being hit by a 0-damage
    /// special move therefore must not make Mirror Coat fail.
    /// </summary>
    [Test]
    public async Task ChangeMoveDamage_UserHitBySpecialMoveDealingZeroDamage_DoesNotFail()
    {
        // Arrange
        var (script, user) = CreateMirrorCoatUser();
        var attacker = CreatePokemonWithEmptyVolatile();
        ReceiveHit(user, attacker, 0);
        var (move, hitData) = CreateExecutingMirrorCoat(user, attacker);
        uint damage = 0;

        // Act
        script.ChangeMoveDamage(move, attacker, 0, ref damage);

        // Assert
        await Assert.That(hitData.ReceivedCalls().Any(c => c.GetMethodInfo().Name == "Fail")).IsFalse();
    }

    /// <summary>
    /// Bulbapedia: Mirror Coat counters "the last amount of damage done to the user before the use of
    /// Mirror Coat" — i.e. damage taken within the same turn. The helper volatile script therefore
    /// removes itself at the end of the turn, so a hit from a previous turn is never countered.
    /// </summary>
    [Test]
    public async Task MirrorCoatHelper_OnEndTurn_RemovesItselfFromUser()
    {
        // Arrange
        var (_, user) = CreateMirrorCoatUser();
        var helper = (IScriptOnEndTurn)user.Volatile.Get(HelperName)!.Script!;

        // Act
        helper.OnEndTurn(user, Substitute.For<IBattle>());

        // Assert
        await Assert.That(user.Volatile.Contains(HelperName)).IsFalse();
    }
}