using System.Collections.Immutable;
using SideScrollerGame.Sim.Definitions;
using SideScrollerGame.Sim.Input;

namespace SideScrollerGame.Sim.Tests;

public sealed class SimulationStepTests
{
    private sealed record UnsupportedAction : SimulationAction;

    [Fact]
    public void Step_AdvancesTickSnapshotsAndMovement()
    {
        Simulation simulation = new(SimulationTestFactory.CreateGameDefinition(), SimulationTestFactory.CreateConfig(), 7);

        var result = simulation.Step(SimulationTestFactory.CreateTick(1, new MoveAxisChanged(new(1), 2, -1), new AimAxisChanged(new(1), 30, 40), new ButtonChanged(new(1), InputButton.Jump, true), new WeaponSlotSelected(new(1), 3)));

        Assert.Equal(1, simulation.CurrentTick);
        Assert.Equal(0, simulation.PreviousSnapshot.Tick);
        Assert.Equal(0, result.PreviousSnapshot.Tick);
        Assert.Equal(1, result.CurrentSnapshot.Tick);
        Assert.Single(result.Events);

        var player = simulation.CurrentState.GetRequiredPlayer(new(1));
        Assert.Equal(12, player.Position.m_X.ToIntRound());
        Assert.Equal(19, player.Position.m_Y.ToIntRound());
        Assert.Equal(30, player.AimAxisX);
        Assert.Equal(40, player.AimAxisY);
        Assert.Equal(3, player.SelectedWeaponSlot);
        Assert.Equal(10, player.Health);
        Assert.NotEqual(0, player.ButtonMask);
        Assert.Equal(result.StateHash, simulation.CurrentSnapshot.StateHash);
        Assert.NotEqual(0UL, simulation.CurrentSnapshot.LastRandomValue);
    }

    [Fact]
    public void Step_ClampsPlayerToWorldBounds()
    {
        Simulation simulation = new(SimulationTestFactory.CreateGameDefinition(new(new(0, 0), new(11, 20))), SimulationTestFactory.CreateConfig(), 7);

        var result = simulation.Step(SimulationTestFactory.CreateTick(1, new MoveAxisChanged(new(1), 5, 0)));

        var player = simulation.CurrentState.GetRequiredPlayer(new(1));
        Assert.Equal(11, player.Position.m_X.ToIntRound());
        Assert.Contains(result.Events, static e => e.Kind == "PlayerClamped");
    }

    [Fact]
    public void Step_AppliesHazardDamage()
    {
        Simulation simulation = new(SimulationTestFactory.CreateGameDefinition(hazards: ImmutableArray.Create(new HazardDefinition("lava", new(new(11, 20), new(12, 21)), 3))), SimulationTestFactory.CreateConfig(), 7);

        var result = simulation.Step(SimulationTestFactory.CreateTick(1, new MoveAxisChanged(new(1), 1, 0)));

        var player = simulation.CurrentState.GetRequiredPlayer(new(1));
        Assert.Equal(7, player.Health);
        Assert.Contains(result.Events, static e => e.Kind == "PlayerDamaged");
    }

    [Fact]
    public void Step_IgnoresHazardsWhenPlayerIsOutside()
    {
        Simulation simulation = new(SimulationTestFactory.CreateGameDefinition(hazards: ImmutableArray.Create(new HazardDefinition("lava", new(new(50, 50), new(60, 60)), 3))), SimulationTestFactory.CreateConfig(), 7);

        var result = simulation.Step(SimulationTestFactory.CreateTick(1, new MoveAxisChanged(new(1), 1, 0)));

        Assert.Equal(10, simulation.CurrentState.GetRequiredPlayer(new(1)).Health);
        Assert.DoesNotContain(result.Events, static e => e.Kind == "PlayerDamaged");
    }

    [Fact]
    public void Step_ActivatesTriggerOnlyOnce()
    {
        Simulation simulation = new(SimulationTestFactory.CreateGameDefinition(triggers: ImmutableArray.Create(new TriggerDefinition("checkpoint_a", new(new(11, 20), new(12, 21)), "TriggerActivated"))), SimulationTestFactory.CreateConfig(), 7);

        var first = simulation.Step(SimulationTestFactory.CreateTick(1, new MoveAxisChanged(new(1), 1, 0)));
        var second = simulation.Step(SimulationTestFactory.CreateTick(2, new MoveAxisChanged(new(1), 0, 0)));

        Assert.Contains(first.Events, static e => e.Kind == "TriggerActivated");
        Assert.DoesNotContain(second.Events, static e => e.Kind == "TriggerActivated");
        Assert.Contains("checkpoint_a", simulation.CurrentState.ActivatedTriggerIds);
    }

    [Fact]
    public void Step_IgnoresTriggersWhenPlayerIsOutside()
    {
        Simulation simulation = new(SimulationTestFactory.CreateGameDefinition(triggers: ImmutableArray.Create(new TriggerDefinition("checkpoint_a", new(new(50, 50), new(60, 60)), "TriggerActivated"))), SimulationTestFactory.CreateConfig(), 7);

        var result = simulation.Step(SimulationTestFactory.CreateTick(1, new MoveAxisChanged(new(1), 1, 0)));

        Assert.DoesNotContain(result.Events, static e => e.Kind == "TriggerActivated");
        Assert.Empty(simulation.CurrentState.ActivatedTriggerIds);
    }

    [Fact]
    public void Step_RejectsUnexpectedTickNumbers()
    {
        Simulation simulation = new(SimulationTestFactory.CreateGameDefinition(), SimulationTestFactory.CreateConfig(), 7);

        var exception = Assert.Throws<InvalidOperationException>(() => simulation.Step(TickActionBatch.Empty(2)));

        Assert.Contains("Expected tick 1", exception.Message);
    }

    [Fact]
    public void Step_RejectsUnknownPlayers()
    {
        Simulation simulation = new(SimulationTestFactory.CreateGameDefinition(), SimulationTestFactory.CreateConfig(), 7);

        var exception = Assert.Throws<InvalidOperationException>(() => simulation.Step(SimulationTestFactory.CreateTick(1, new MoveAxisChanged(new(99), 1, 0))));

        Assert.Contains("Unknown player id 99", exception.Message);
    }

    [Fact]
    public void Step_RejectsUnsupportedActions()
    {
        Simulation simulation = new(SimulationTestFactory.CreateGameDefinition(), SimulationTestFactory.CreateConfig(), 7);

        var exception = Assert.Throws<NotSupportedException>(() => simulation.Step(SimulationTestFactory.CreateTick(1, new UnsupportedAction())));

        Assert.Contains("Unsupported action type", exception.Message);
    }

    [Fact]
    public void Constructor_RejectsDuplicatePlayers()
    {
        GameDefinition definition = new(new(new(new(0, 0), new(100, 100)), ImmutableArray<HazardDefinition>.Empty, ImmutableArray<TriggerDefinition>.Empty), ImmutableArray.Create(new(new(1), new(0, 0), 10), new PlayerDefinition(new(1), new(2, 3), 10)));

        var exception = Assert.Throws<InvalidOperationException>(() => new Simulation(definition, SimulationTestFactory.CreateConfig(), 11));

        Assert.Contains("Duplicate player id 1", exception.Message);
    }

    [Fact]
    public void Constructor_RejectsSpawnOutsideBounds()
    {
        GameDefinition definition = new(new(new(new(0, 0), new(5, 5)), ImmutableArray<HazardDefinition>.Empty, ImmutableArray<TriggerDefinition>.Empty), ImmutableArray.Create(new PlayerDefinition(new(1), new(10, 20), 10)));

        var exception = Assert.Throws<InvalidOperationException>(() => new Simulation(definition, SimulationTestFactory.CreateConfig(), 11));

        Assert.Contains("spawn must start inside world bounds", exception.Message);
    }

    [Fact]
    public void Constructor_RejectsNonPositiveHealth()
    {
        GameDefinition definition = new(new(new(new(0, 0), new(100, 100)), ImmutableArray<HazardDefinition>.Empty, ImmutableArray<TriggerDefinition>.Empty), ImmutableArray.Create(new PlayerDefinition(new(1), new(1, 1), 0)));

        var exception = Assert.Throws<InvalidOperationException>(() => new Simulation(definition, SimulationTestFactory.CreateConfig(), 11));

        Assert.Contains("positive health", exception.Message);
    }

    [Fact]
    public void Constructor_RejectsNullDefinition()
    {
        var exception = Assert.Throws<ArgumentNullException>(() => new Simulation(null!, SimulationTestFactory.CreateConfig(), 1));

        Assert.Equal("gameDefinition", exception.ParamName);
    }

    [Fact]
    public void Constructor_RejectsNullConfig()
    {
        var exception = Assert.Throws<ArgumentNullException>(() => new Simulation(SimulationTestFactory.CreateGameDefinition(), null!, 1));

        Assert.Equal("config", exception.ParamName);
    }

    [Fact]
    public void LoadState_RejectsNullDefinition()
    {
        var definition = SimulationTestFactory.CreateGameDefinition();
        var config = SimulationTestFactory.CreateConfig();
        Simulation simulation = new(definition, config, 2);
        var bytes = simulation.SaveState();

        var exception = Assert.Throws<ArgumentNullException>(() => Simulation.LoadState(bytes, null!, config));

        Assert.Equal("gameDefinition", exception.ParamName);
    }
}