SlaySharp/tests/SlaySharp.Tests/CombatEngineTests.cs

using SlaySharp.Core.Catalogs;
using SlaySharp.Core.Combat;
using SlaySharp.Core.Enums;
using SlaySharp.Core.Models;
using Xunit;

namespace SlaySharp.Tests;

public class CombatEngineTests
{
    [Fact]
    public void CombatEngine_InitializesDeckAndDraws5Cards()
    {
        var player = new Player("Senior Dev", 70, maxEnergy: 3, seed: 42);
        player.MasterDeck.AddRange(StarterDecks.CreateCsharpArchitectDeck());

        var engine = new CombatEngine();
        var enemy = new NullReferenceExceptionEnemy();

        engine.StartCombat(player, new List<Enemy> { enemy });

        Assert.Equal(CombatPhase.PlayerTurn, engine.Phase);
        Assert.Equal(3, player.CurrentEnergy);
        Assert.Equal(5, player.Hand.Count);
        Assert.Equal(player.MasterDeck.Count - 5, player.DrawPile.Count);
        Assert.Empty(player.DiscardPile);
    }

    [Fact]
    public void PlayCard_DealsDamage_AndConsumesEnergy()
    {
        var player = new Player("Senior Dev", 70, maxEnergy: 3);
        var card = new ConsoleWriteLineCard(); // Cost 1, dmg 6
        var enemy = new NullReferenceExceptionEnemy(); // 45 HP

        var engine = new CombatEngine();
        engine.StartCombat(player, new List<Enemy> { enemy });

        player.Hand.Clear();
        player.Hand.Add(card);
        player.CurrentEnergy = 3;

        var success = engine.PlayCard(card, enemy);

        Assert.True(success);
        Assert.Equal(2, player.CurrentEnergy);
        Assert.True(enemy.CurrentHp <= 39);
        Assert.Contains(card, player.DiscardPile);
    }

    [Fact]
    public void CalculateDamagePreview_AccuratelyCalculatesHpLossAndShieldAbsorbed()
    {
        var player = new Player("Senior Dev", 70, maxEnergy: 3);
        var card = new ThrowExceptionCard(); // 16 dmg
        var enemy = new OffByOneBugEnemy(); // 22 HP

        var engine = new CombatEngine();
        engine.StartCombat(player, new List<Enemy> { enemy });
        enemy.GainShield(6); // Set shield AFTER StartCombat

        var preview = engine.CalculateDamagePreview(card, enemy);

        Assert.Equal(16, preview.MinRawDamage);
        Assert.Equal(6, preview.ShieldAbsorbed);
        Assert.Equal(10, preview.MinHpLoss); // 16 - 6 shield = 10 HP loss
        Assert.Equal(12, preview.ProjectedRemainingHp); // 22 - 10 = 12
        Assert.False(preview.IsLethal);
    }

    [Fact]
    public void CalculateDamagePreview_IdentifiesLethalDamage()
    {
        var player = new Player("Senior Dev", 70, maxEnergy: 3);
        var card = new ThrowExceptionCard(); // 16 dmg
        var enemy = new OffByOneBugEnemy(); // 22 HP

        var engine = new CombatEngine();
        engine.StartCombat(player, new List<Enemy> { enemy });
        enemy.CurrentHp = 14;

        var preview = engine.CalculateDamagePreview(card, enemy);

        Assert.Equal(16, preview.MinHpLoss);
        Assert.True(preview.IsLethal);
        Assert.Equal(0, preview.ProjectedRemainingHp);
    }

    [Fact]
    public void SpanSliceCard_PiercesThroughShield()
    {
        var player = new Player("Senior Dev", 70, maxEnergy: 3);
        var card = new SpanSliceCard(); // 8 piercing dmg
        var enemy = new NullReferenceExceptionEnemy(); // 45 HP

        var engine = new CombatEngine();
        engine.StartCombat(player, new List<Enemy> { enemy });

        enemy.GainShield(10);
        player.Hand.Clear();
        player.Hand.Add(card);
        player.CurrentEnergy = 3;

        var success = engine.PlayCard(card, enemy);

        Assert.True(success);
        Assert.Equal(10, enemy.Shield);
        Assert.True(enemy.CurrentHp <= 37);
    }

    [Fact]
    public void StatusEffects_StrengthAndVulnerable_MultiplyDamage()
    {
        var player = new Player("Senior Dev", 70, maxEnergy: 3);
        var enemy = new NullReferenceExceptionEnemy(); // 45 HP
        var card = new ConsoleWriteLineCard(); // 6 dmg

        var engine = new CombatEngine();
        engine.StartCombat(player, new List<Enemy> { enemy });

        player.Statuses.Add(StatusType.Strength, 2);
        enemy.Statuses.Add(StatusType.Vulnerable, 1);

        player.Hand.Clear();
        player.Hand.Add(card);
        player.CurrentEnergy = 3;

        engine.PlayCard(card, enemy);

        Assert.True(enemy.CurrentHp <= 33);
    }

    [Fact]
    public void DiscardPile_Reshuffles_WhenDrawPileEmpty()
    {
        var player = new Player("Senior Dev", 70, maxEnergy: 3, seed: 123);
        player.MasterDeck.Add(new ConsoleWriteLineCard());
        player.MasterDeck.Add(new TryCatchCard());
        player.MasterDeck.Add(new LinqWhereCard());

        var engine = new CombatEngine();
        var enemy = new OffByOneBugEnemy();

        engine.StartCombat(player, new List<Enemy> { enemy });

        Assert.Equal(3, player.Hand.Count);
        Assert.Empty(player.DrawPile);

        player.DiscardPile.Add(player.Hand[0]);
        player.DiscardPile.Add(player.Hand[1]);
        player.Hand.RemoveRange(0, 2);

        player.DrawCards(2, engine.Log);

        Assert.Equal(3, player.Hand.Count);
        Assert.Empty(player.DiscardPile);
    }

    [Fact]
    public void KillingAllEnemies_TriggersVictory()
    {
        var player = new Player("Senior Dev", 70, maxEnergy: 3);
        var card = new ThrowExceptionCard(); // 16 dmg
        var enemy = new OffByOneBugEnemy(); // 22 HP

        var engine = new CombatEngine();
        engine.StartCombat(player, new List<Enemy> { enemy });

        enemy.CurrentHp = 10;
        player.Hand.Clear();
        player.Hand.Add(card);
        player.CurrentEnergy = 2;

        engine.PlayCard(card, enemy);

        Assert.Equal(CombatPhase.Victory, engine.Phase);
        Assert.Empty(engine.Enemies);
        Assert.NotEmpty(engine.CardRewards);
    }
}