@using Sandbox;
@using Sandbox.UI;
@using Machines.Player;
@using Machines.Components;
@using Machines.GameModes;

@namespace Machines.UI
@inherits Panel

<root class="score-hud">
    @{
        var car = VisibleCar();
        if ( car is not null )
        {
            var score = car.Score;

            <div class="score-stack" style="opacity: @ComboAlpha( score ).ToString( "0.###", System.Globalization.CultureInfo.InvariantCulture );">
                <div class="combo-value">@score.ComboScore</div>

                @foreach ( var entry in score.Entries.OrderByDescending( e => e.LastTime ) )
                {
                    <div class="combo-entry">
                        <span class="entry-source">@entry.Source</span>
                        <span class="entry-amount">+@entry.Amount</span>
                    </div>
                }
            </div>
        }
    }
</root>

@code
{
    // Tail of the combo timeout over which the whole stack fades out (seconds).
    private const float FadeTail = 0.4f;

    /// <summary>
    /// Local car to show, only while a combo is running; null hides the overlay (so it never
    /// shows on start, and disappears once the chain lapses). Mirrors CarBoostHud's gating.
    /// </summary>
    private Car VisibleCar()
    {
        if ( !BaseGameMode.Current.IsValid() || BaseGameMode.Current.State != GameModeState.Playing )
            return null;

        if ( Game.ActiveScene?.Get<SpectatorCamera>()?.IsActive ?? false )
            return null;

        var car = Car.Local;
        if ( !car.IsValid() || car.Autopilot )
            return null;

        if ( !car.Score.IsValid() || !car.Score.IsComboActive )
            return null;

        return car;
    }

    // Full opacity until the last FadeTail seconds of the combo, then ramp to zero.
    private static float ComboAlpha( CarScore score )
    {
        var remaining = CarScore.ComboTimeout - score.SinceLastGain;
        return MathX.Clamp( remaining / FadeTail, 0f, 1f );
    }

    protected override int BuildHash() => HashCode.Combine( Time.Now );
}