PkmnLib.NET/Plugins/PkmnLib.Plugin.Gen7.Tests/Scripts/Moves/MimicTests.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="Mimic"/> script, which implements Mimic.
/// Behavior is verified against the Bulbapedia page for Mimic (Generation VII).
/// The script is expected to copy the target's last used move through the engine's
/// <see cref="IScriptOnSecondaryEffect"/> hook, the same pattern used by <see cref="Sketch"/>.
/// </summary>
public class MimicTests
{
    /// <summary>
    /// Creates a mocked <see cref="ILearnedMove"/> whose move data has the given name.
    /// </summary>
    private static ILearnedMove CreateLearnedMove(string name)
    {
        var learned = Substitute.For<ILearnedMove>();
        var data = Substitute.For<IMoveData>();
        data.Name.Returns(new StringKey(name));
        learned.MoveData.Returns(data);
        return learned;
    }

    /// <summary>
    /// Creates a fully mocked executing Mimic move. The user knows one other move in slot 0 and Mimic in
    /// slot 1. If <paramref name="targetLastUsedMove"/> is null, the target has not used a move yet.
    /// </summary>
    private static (IExecutingMove move, IPokemon user, IPokemon target, IHitData hitData) CreateTestSetup(
        string? targetLastUsedMove, string userOtherMove = "swords_dance")
    {
        var move = Substitute.For<IExecutingMove>();
        var user = Substitute.For<IPokemon>();
        var target = Substitute.For<IPokemon>();
        move.User.Returns(user);
        var hitData = Substitute.For<IHitData>();
        move.GetHitData(target, 0).Returns(hitData);

        // The user knows another move in slot 0, and Mimic in slot 1; Mimic is the chosen move.
        // The moves are created before the Returns call, as creating substitutes inside Returns arguments
        // resets NSubstitute's last-call tracking.
        var mimicMove = CreateLearnedMove("mimic");
        move.ChosenMove.Returns(mimicMove);
        var userMoves = new[] { CreateLearnedMove(userOtherMove), mimicMove };
        user.Moves.Returns(userMoves);

        var battleData = Substitute.For<IPokemonBattleData>();
        if (targetLastUsedMove != null)
        {
            var lastChoice = Substitute.For<IMoveChoice>();
            var lastUsedMove = CreateLearnedMove(targetLastUsedMove);
            lastChoice.ChosenMove.Returns(lastUsedMove);
            battleData.LastMoveChoice.Returns(lastChoice);
        }
        else
        {
            battleData.LastMoveChoice.Returns((IMoveChoice?)null);
        }

        target.BattleData.Returns(battleData);
        return (move, user, target, hitData);
    }

    /// <summary>
    /// Asserts that the <see cref="Mimic"/> script implements the secondary effect hook, and returns it as
    /// that hook. Every behavior of Mimic requires this hook to exist at all.
    /// </summary>
    private static async Task<IScriptOnSecondaryEffect> GetSecondaryEffectHook()
    {
        var mimic = new Mimic();
        await Assert.That(mimic is IScriptOnSecondaryEffect).IsTrue();
        return (IScriptOnSecondaryEffect)(object)mimic;
    }

    /// <summary>
    /// Helper that checks whether <see cref="IHitData.Fail"/> was called on the hit data.
    /// </summary>
    private static bool ReceivedFail(IHitData hitData) =>
        hitData.ReceivedCalls().Any(c => c.GetMethodInfo().Name == "Fail");

    /// <summary>
    /// Helper to extract the arguments of the user's received <see cref="IPokemon.LearnTemporaryMove"/> call.
    /// </summary>
    private static (StringKey moveName, byte index)? GetLearnedMove(IPokemon user)
    {
        var call = user.ReceivedCalls().FirstOrDefault(c => c.GetMethodInfo().Name == "LearnTemporaryMove");
        if (call == null)
            return null;
        return ((StringKey)call.GetArguments()[0]!, (byte)call.GetArguments()[2]!);
    }

    /// <summary>
    /// Bulbapedia: "Mimic copies a move from the target. The user will retain the copied move in Mimic's
    /// place" and (Generation II onwards) "Mimic now copies the target's last used move."
    /// The target's last used move must be learned in the move slot that holds Mimic.
    /// </summary>
    [Test]
    public async Task OnSecondaryEffect_TargetUsedMove_UserLearnsTargetsLastMoveInMimicsSlot()
    {
        // Arrange
        var mimic = await GetSecondaryEffectHook();
        var (move, user, target, _) = CreateTestSetup("tackle");

        // Act
        mimic.OnSecondaryEffect(move, target, 0);

        // Assert - the copied move replaces Mimic, which sits in slot 1.
        var learned = GetLearnedMove(user);
        await Assert.That(learned.HasValue).IsTrue();
        await Assert.That(learned!.Value.moveName).IsEqualTo(new StringKey("tackle"));
        await Assert.That(learned.Value.index).IsEqualTo((byte)1);
    }

    /// <summary>
    /// Bulbapedia: (Generation II onwards) "Mimic now copies the target's last used move."
    /// If the target has not used a move yet, there is nothing to copy and the hit must fail.
    /// </summary>
    [Test]
    public async Task OnSecondaryEffect_TargetHasNotUsedAMove_FailsHit()
    {
        // Arrange
        var mimic = await GetSecondaryEffectHook();
        var (move, user, target, hitData) = CreateTestSetup(null);

        // Act
        mimic.OnSecondaryEffect(move, target, 0);

        // Assert
        await Assert.That(ReceivedFail(hitData)).IsTrue();
        await Assert.That(GetLearnedMove(user).HasValue).IsFalse();
    }

    /// <summary>
    /// Bulbapedia: (Generation II onwards) "It now fails to copy the moves Sketch, Transform, Struggle,
    /// Metronome, or any move the user already knows.", (Generation IV onwards) "Mimic will fail to copy
    /// Chatter.", and (Generation V onwards) "Mimic is no longer able to copy Transform."
    /// </summary>
    [Test, Arguments("sketch"), Arguments("transform"), Arguments("struggle"), Arguments("metronome"),
     Arguments("chatter")]
    public async Task OnSecondaryEffect_TargetsLastMoveIsUncopyable_FailsHit(string uncopyableMove)
    {
        // Arrange
        var mimic = await GetSecondaryEffectHook();
        var (move, user, target, hitData) = CreateTestSetup(uncopyableMove);

        // Act
        mimic.OnSecondaryEffect(move, target, 0);

        // Assert
        await Assert.That(ReceivedFail(hitData)).IsTrue();
        await Assert.That(GetLearnedMove(user).HasValue).IsFalse();
    }

    /// <summary>
    /// Bulbapedia: (Generation II onwards) "It now fails to copy ... any move the user already knows."
    /// </summary>
    [Test]
    public async Task OnSecondaryEffect_UserAlreadyKnowsTargetsLastMove_FailsHit()
    {
        // Arrange
        var mimic = await GetSecondaryEffectHook();
        // The target's last used move is Tackle, which the user already knows in slot 0.
        var (move, user, target, hitData) = CreateTestSetup("tackle", "tackle");

        // Act
        mimic.OnSecondaryEffect(move, target, 0);

        // Assert
        await Assert.That(ReceivedFail(hitData)).IsTrue();
        await Assert.That(GetLearnedMove(user).HasValue).IsFalse();
    }

    /// <summary>
    /// Bulbapedia: (Generation II onwards) "The copied move will also only have 5 PP".
    /// After learning the copy, its current PP must be set to 5.
    /// </summary>
    [Test]
    public async Task OnSecondaryEffect_TargetUsedMove_CopiedMoveGetsFivePP()
    {
        // Arrange
        var mimic = await GetSecondaryEffectHook();
        var (move, user, target, _) = CreateTestSetup("tackle");

        // Act
        mimic.OnSecondaryEffect(move, target, 0);

        // Assert - the move in Mimic's slot (slot 1) has its PP set to 5.
        user.Moves[1]!.Received(1).SetCurrentPP(5);
    }
}