PkmnLib.NET/Plugins/PkmnLib.Plugin.Gen7.Tests/Scripts/Moves/MetalBurstTests.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="MetalBurst"/> script, which implements Metal Burst.
/// Behavior is verified against the Bulbapedia page for Metal Burst (Generation VII).
/// </summary>
public class MetalBurstTests
{
    /// <summary>
    /// Creates a Metal Burst user whose damage-tracking volatile has been installed through
    /// <see cref="MetalBurst.OnBeforeTurnStart"/>. The user's <see cref="IPokemon.Volatile"/> is a real
    /// <see cref="ScriptSet"/> so the internal tracker script can actually be stored and retrieved.
    /// </summary>
    private static (MetalBurst metalBurst, IPokemon user, IScriptSet userVolatile) CreateUserWithTracker()
    {
        var metalBurst = new MetalBurst();
        var user = Substitute.For<IPokemon>();
        var userVolatile = new ScriptSet(user);
        user.Volatile.Returns(userVolatile);
        // ScriptSet.Add runs the IScriptPreventVolatileAdd hook pass over the owner's scripts; give the mock a
        // real (empty) iterator so that pass can run.
        user.GetScripts().Returns(_ => new ScriptIterator(new List<IEnumerable<ScriptContainer>>()));

        var choice = Substitute.For<ITurnChoice>();
        choice.User.Returns(user);
        metalBurst.OnBeforeTurnStart(choice);
        return (metalBurst, user, userVolatile);
    }

    /// <summary>
    /// Creates an opposing Pokémon with a real (empty) <see cref="ScriptSet"/> as its volatile collection.
    /// </summary>
    private static IPokemon CreateOpponent()
    {
        var opponent = Substitute.For<IPokemon>();
        opponent.Volatile.Returns(new ScriptSet(opponent));
        return opponent;
    }

    /// <summary>
    /// Simulates the user being hit by an opponent's move; the damage tracker installed on the user observes
    /// this through its <see cref="IScriptOnIncomingHit"/> hook.
    /// </summary>
    private static void HitUser(IPokemon user, IPokemon attacker, uint damage,
        MoveCategory category = MoveCategory.Physical, byte hit = 0)
    {
        var attackMove = Substitute.For<IExecutingMove>();
        attackMove.User.Returns(attacker);
        var moveData = Substitute.For<IMoveData>();
        moveData.Category.Returns(category);
        attackMove.UseMove.Returns(moveData);
        var hitData = Substitute.For<IHitData>();
        hitData.Damage.Returns(damage);
        attackMove.GetHitData(user, hit).Returns(hitData);

        var tracker = user.Volatile.Select(c => c.Script).OfType<IScriptOnIncomingHit>().Single();
        tracker.OnIncomingHit(attackMove, user, hit);
    }

    /// <summary>
    /// Creates the executing Metal Burst move used by <paramref name="user"/> against <paramref name="target"/>.
    /// </summary>
    private static (IExecutingMove move, IHitData hitData) CreateMetalBurstMove(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>
    /// 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>
    /// Bulbapedia: "Metal Burst returns 1.5 times the damage dealt by the foe's last attack."
    /// To know that damage, the script installs a damage-tracking volatile on the user just before the turn
    /// starts.
    /// </summary>
    [Test]
    public async Task OnBeforeTurnStart_Called_AddsDamageTrackerToUserVolatile()
    {
        // Arrange & Act
        var (_, _, userVolatile) = CreateUserWithTracker();

        // Assert
        await Assert.That(userVolatile.Count).IsEqualTo(1);
    }

    /// <summary>
    /// Bulbapedia: "Metal Burst returns 1.5 times the damage dealt by the foe's last attack."
    /// The user is hit by the target, then retaliates with Metal Burst against that target; the damage must be
    /// 1.5 times the damage taken (fractions truncated).
    /// </summary>
    [Test, Arguments(100u, 150u), Arguments(101u, 151u), Arguments(33u, 49u), Arguments(1u, 1u)]
    public async Task ChangeMoveDamage_UserWasHitByTarget_DealsOneAndAHalfTimesDamageTaken(uint damageTaken,
        uint expectedDamage)
    {
        // Arrange
        var (metalBurst, user, _) = CreateUserWithTracker();
        var attacker = CreateOpponent();
        HitUser(user, attacker, damageTaken);
        var (move, _) = CreateMetalBurstMove(user, attacker);

        // Act
        uint damage = 0;
        metalBurst.ChangeMoveDamage(move, attacker, 0, ref damage);

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

    /// <summary>
    /// Bulbapedia: "Metal Burst returns 1.5 times the damage dealt by the foe's last attack."
    /// When the user was hit by the target this turn, Metal Burst succeeds, so the hit must not be failed.
    /// </summary>
    [Test]
    public async Task ChangeMoveDamage_UserWasHitByTarget_DoesNotFailHit()
    {
        // Arrange
        var (metalBurst, user, _) = CreateUserWithTracker();
        var attacker = CreateOpponent();
        HitUser(user, attacker, 100);
        var (move, hitData) = CreateMetalBurstMove(user, attacker);

        // Act
        uint damage = 0;
        metalBurst.ChangeMoveDamage(move, attacker, 0, ref damage);

        // Assert
        await Assert.That(ReceivedFail(hitData)).IsFalse();
    }

    /// <summary>
    /// Bulbapedia: "if the user acts before it is hit by an opponent's damaging move, Metal Burst will fail."
    /// If no damaging move hit the user this turn, the hit is failed and no damage is dealt.
    /// </summary>
    [Test]
    public async Task ChangeMoveDamage_UserNotHitThisTurn_FailsHit()
    {
        // Arrange
        var (metalBurst, user, _) = CreateUserWithTracker();
        var opponent = CreateOpponent();
        var (move, hitData) = CreateMetalBurstMove(user, opponent);

        // Act
        uint damage = 0;
        metalBurst.ChangeMoveDamage(move, opponent, 0, ref damage);

        // Assert
        await Assert.That(ReceivedFail(hitData)).IsTrue();
        await Assert.That(damage).IsEqualTo(0u);
    }

    /// <summary>
    /// Bulbapedia: "if the user acts before it is hit by an opponent's damaging move, Metal Burst will fail."
    /// A status move is not a damaging move, so being targeted by only a status move must still make Metal
    /// Burst fail.
    /// </summary>
    [Test]
    public async Task ChangeMoveDamage_UserOnlyHitByStatusMove_FailsHit()
    {
        // Arrange
        var (metalBurst, user, _) = CreateUserWithTracker();
        var attacker = CreateOpponent();
        HitUser(user, attacker, 0, MoveCategory.Status);
        var (move, hitData) = CreateMetalBurstMove(user, attacker);

        // Act
        uint damage = 0;
        metalBurst.ChangeMoveDamage(move, attacker, 0, ref damage);

        // Assert
        await Assert.That(ReceivedFail(hitData)).IsTrue();
    }

    /// <summary>
    /// Bulbapedia: "Only the last damage taken will be counted, if the user is hit by a multi-hit move, only
    /// the damage from the final hit will be counted."
    /// </summary>
    [Test]
    public async Task ChangeMoveDamage_UserHitByMultiHitMove_OnlyFinalHitCounted()
    {
        // Arrange
        var (metalBurst, user, _) = CreateUserWithTracker();
        var attacker = CreateOpponent();
        HitUser(user, attacker, 40, hit: 0);
        HitUser(user, attacker, 100, hit: 1);
        var (move, _) = CreateMetalBurstMove(user, attacker);

        // Act
        uint damage = 0;
        metalBurst.ChangeMoveDamage(move, attacker, 0, ref damage);

        // Assert - 1.5 times the final hit's 100 damage, not the earlier 40.
        await Assert.That(damage).IsEqualTo(150u);
    }

    /// <summary>
    /// Bulbapedia: "In battles involving multiple Pokémon, Metal Burst will hit the last opponent that dealt
    /// damage to the user".
    /// When two opponents hit the user, retaliating against the last one uses that opponent's damage.
    /// </summary>
    [Test]
    public async Task ChangeMoveDamage_UserHitByTwoOpponents_UsesDamageOfLastAttacker()
    {
        // Arrange
        var (metalBurst, user, _) = CreateUserWithTracker();
        var firstAttacker = CreateOpponent();
        var lastAttacker = CreateOpponent();
        HitUser(user, firstAttacker, 50);
        HitUser(user, lastAttacker, 80);
        var (move, _) = CreateMetalBurstMove(user, lastAttacker);

        // Act
        uint damage = 0;
        metalBurst.ChangeMoveDamage(move, lastAttacker, 0, ref damage);

        // Assert
        await Assert.That(damage).IsEqualTo(120u);
    }

    /// <summary>
    /// Bulbapedia: "Metal Burst will hit the last opponent that dealt damage to the user".
    /// Hitting an opponent that is not the last Pokémon that damaged the user must fail.
    /// </summary>
    [Test]
    public async Task ChangeMoveDamage_TargetIsNotLastAttacker_FailsHit()
    {
        // Arrange
        var (metalBurst, user, _) = CreateUserWithTracker();
        var firstAttacker = CreateOpponent();
        var lastAttacker = CreateOpponent();
        HitUser(user, firstAttacker, 50);
        HitUser(user, lastAttacker, 80);
        var (move, hitData) = CreateMetalBurstMove(user, firstAttacker);

        // Act
        uint damage = 0;
        metalBurst.ChangeMoveDamage(move, firstAttacker, 0, ref damage);

        // Assert
        await Assert.That(ReceivedFail(hitData)).IsTrue();
    }

    /// <summary>
    /// Bulbapedia: "In battles involving multiple Pokémon, Metal Burst will hit the last opponent that dealt
    /// damage to the user" — like <see cref="Counter"/>, the script must implement
    /// <see cref="IScriptChangeTargets"/> and redirect the move at the last attacker.
    /// </summary>
    [Test]
    public async Task ChangeTargets_UserHitByOpponents_RedirectsToLastAttacker()
    {
        // Arrange
        var (metalBurst, user, _) = CreateUserWithTracker();
        var firstAttacker = CreateOpponent();
        var lastAttacker = CreateOpponent();
        HitUser(user, firstAttacker, 50);
        HitUser(user, lastAttacker, 80);
        var choice = Substitute.For<IMoveChoice>();
        choice.User.Returns(user);
        IReadOnlyList<IPokemon?> targets = [firstAttacker];

        // Act & Assert - the script must expose the redirection hook and point the move at the last attacker
        var changeTargets = metalBurst 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(lastAttacker);
    }

    /// <summary>
    /// Bulbapedia: "Metal Burst returns 1.5 times the damage dealt by the foe's last attack." combined with
    /// "if the user acts before it is hit by an opponent's damaging move, Metal Burst will fail."
    /// Only damage taken during the current turn counts, so the damage tracker must be cleaned up at the end
    /// of the turn.
    /// </summary>
    [Test]
    public async Task OnEndTurn_Called_RemovesDamageTrackerFromUser()
    {
        // Arrange
        var (_, user, userVolatile) = CreateUserWithTracker();
        var tracker = userVolatile.At(0).Script!;

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

        // Assert
        await Assert.That(userVolatile.Get(new StringKey("metal_burst_helper"))).IsNull();
    }
}