PkmnLib.NET/PkmnLib.Tests/Dynamic/BattleLifecycleTests.cs

using PkmnLib.Dynamic.Libraries;
using PkmnLib.Dynamic.Models;
using PkmnLib.Static;
using PkmnLib.Static.Species;
using PkmnLib.Tests.Integration;

namespace PkmnLib.Tests.Dynamic;

/// <summary>
/// Regression tests for the battle lifecycle of <see cref="IBattlePokemon"/>: battle-only state must die
/// with the battle, and the underlying <see cref="IPokemon"/> must come out of a battle unchanged except
/// for the deliberately persistent parts (health, PP, non-volatile status, experience).
/// </summary>
public class BattleLifecycleTests
{
    private static IPokemon CreatePokemon(IDynamicLibrary library, string speciesName)
    {
        if (!library.StaticLibrary.Species.TryGet(speciesName, out var species))
            throw new InvalidOperationException($"Failed to load {speciesName} species.");
        return new PokemonImpl(library, species, species.GetDefaultForm(), new AbilityIndex
        {
            Index = 0,
            IsHidden = false,
        }, 50, 0, Gender.Male, 0, "hardy");
    }

    private static IBattle CreateBattle(IDynamicLibrary library, IPokemon own, IPokemon opponent,
        bool isWildBattle = false, int seed = 0)
    {
        var party = new PokemonPartyImpl(1);
        party.SwapInto(own, 0);
        var opponentParty = new PokemonPartyImpl(1);
        opponentParty.SwapInto(opponent, 0);
        var parties = new[]
        {
            new BattlePartyImpl(party, [new ResponsibleIndex(0, 0)]),
            new BattlePartyImpl(opponentParty, [new ResponsibleIndex(1, 0)]),
        };
        var battle = new BattleImpl(library, parties, false, 2, 1, isWildBattle, "grass", seed);
        battle.Sides[0].SendOut(0, own);
        battle.Sides[1].SendOut(0, opponent);
        return battle;
    }

    /// <summary>
    /// The original bug this refactor removes by construction: a captured Pokémon must not carry any
    /// battle state into the party of its captor. The capture is reported through
    /// <see cref="BattleResult.CapturedPokemon"/> as the persistent Pokémon.
    /// </summary>
    [Test]
    public async Task Capture_ReportsPersistentPokemonAndLeavesItUsable()
    {
        var library = LibraryHelpers.LoadLibrary();
        if (!library.StaticLibrary.Items.TryGet("master_ball", out var masterBall))
            throw new InvalidOperationException("Failed to load master ball.");

        // The capture roll is random; find a seed where the capture succeeds. The loop is deterministic,
        // so the test always exercises the same battle.
        var result = CaptureResult.Failed;
        IBattle? battle = null;
        IPokemon? wildPokemon = null;
        for (var seed = 0; seed < 100 && !result.IsCaught; seed++)
        {
            battle?.Dispose();
            var own = CreatePokemon(library, "bulbasaur");
            wildPokemon = CreatePokemon(library, "caterpie");
            battle = CreateBattle(library, own, wildPokemon, true, seed);
            var wildBattlePokemon = battle.GetPokemon(1, 0)!;
            wildBattlePokemon.Damage(wildBattlePokemon.CurrentHealth - 1, DamageSource.MoveDamage);
            result = battle.AttempCapture(1, 0, masterBall);
        }

        await Assert.That(result.IsCaught).IsTrue();
        await Assert.That(battle!.HasEnded).IsTrue();
        await Assert.That(battle.Result!.Value.CapturedPokemon).Contains(wildPokemon!);

        battle.Dispose();

        // The persistent Pokémon left the battle without any battle state: it is usable and simply damaged.
        await Assert.That(wildPokemon!.IsUsable).IsTrue();
        await Assert.That(wildPokemon.CurrentHealth).IsEqualTo(1u);
    }

    /// <summary>
    /// Items removed or stolen during a battle are a battle-only overlay: after the battle, the victim
    /// still holds its item.
    /// </summary>
    [Test]
    public async Task StolenHeldItem_IsRestoredAfterBattle()
    {
        var library = LibraryHelpers.LoadLibrary();
        if (!library.StaticLibrary.Items.TryGet("oran_berry", out var berry))
            throw new InvalidOperationException("Failed to load oran berry.");
        var own = CreatePokemon(library, "bulbasaur");
        _ = own.ForceSetHeldItem(berry);
        var opponent = CreatePokemon(library, "charmander");

        var battle = CreateBattle(library, own, opponent);
        var battlePokemon = battle.GetPokemon(0, 0)!;
        await Assert.That(battlePokemon.TryStealHeldItem(out _)).IsTrue();
        await Assert.That(battlePokemon.HeldItem).IsNull();

        battle.Dispose();

        await Assert.That(own.HeldItem).IsSameReferenceAs(berry);
    }

    /// <summary>
    /// A battle-only form (such as a mega evolution) reverts to the original form when the battle ends.
    /// </summary>
    [Test]
    public async Task BattleOnlyForm_RevertsWhenBattleEnds()
    {
        var library = LibraryHelpers.LoadLibrary();
        var own = CreatePokemon(library, "absol");
        var originalForm = own.Form;
        if (!own.Species.TryGetForm("mega", out var megaForm))
            throw new InvalidOperationException("Absol has no mega form.");
        await Assert.That(megaForm.IsBattleOnlyForm).IsTrue();
        var opponent = CreatePokemon(library, "charmander");

        var battle = CreateBattle(library, own, opponent);
        var battlePokemon = battle.GetPokemon(0, 0)!;
        battlePokemon.ChangeForm(megaForm);
        await Assert.That(own.Form).IsSameReferenceAs(megaForm);

        battle.Dispose();

        await Assert.That(own.Form).IsSameReferenceAs(originalForm);
    }

    /// <summary>
    /// A second battle with the same party starts with fresh battle state: no seen opponents or stale
    /// original species from the previous battle.
    /// </summary>
    [Test]
    public async Task SecondBattleWithSameParty_StartsWithFreshBattleState()
    {
        var library = LibraryHelpers.LoadLibrary();
        var own = CreatePokemon(library, "bulbasaur");
        var opponent1 = CreatePokemon(library, "charmander");

        var battle1 = CreateBattle(library, own, opponent1);
        var firstWrapper = battle1.GetPokemon(0, 0)!;
        await Assert.That(firstWrapper.SeenOpponents.Count).IsEqualTo(1);
        firstWrapper.ChangeStatBoost(Statistic.Attack, 3, true, false);
        battle1.Dispose();

        var opponent2 = CreatePokemon(library, "squirtle");
        var battle2 = CreateBattle(library, own, opponent2);
        var secondWrapper = battle2.GetPokemon(0, 0)!;

        await Assert.That(secondWrapper).IsNotSameReferenceAs(firstWrapper);
        await Assert.That(secondWrapper.SeenOpponents.Count).IsEqualTo(1);
        await Assert.That(secondWrapper.SeenOpponents[0].UnderlyingPokemon).IsSameReferenceAs(opponent2);
        await Assert.That(secondWrapper.StatBoost.Attack).IsEqualTo((sbyte)0);
        await Assert.That(secondWrapper.OriginalSpecies).IsSameReferenceAs(own.Species);
        battle2.Dispose();
    }
}