using System.Globalization;

namespace AcDream.App.UI.Layout;

/// <summary>
/// Binds retail's SmartBox frame-rate display to the authored text element from
/// <c>LayoutDesc 0x2100000F</c>.
/// </summary>
/// <remarks>
/// Faithful port of <c>gmSmartBoxUI::RecvNotice_SetFramerateDisplay @ 0x004D65E0</c>,
/// <c>gmSmartBoxUI::UpdateFPSMeter @ 0x004D63A0</c>, and
/// <c>gmSmartBoxUI::UseTime @ 0x004D6E30</c>. Portal string table 0x23000001,
/// string 0x0DCFFF73 supplies the two labels <c>FPS:</c> and <c>DEG:</c>;
/// retail inserts both floating-point values with two decimal places.
/// </remarks>
public sealed class RetailFpsController
{
    public const uint LayoutId = 0x2100000Fu;
    public const uint DisplayElementId = 0x10000047u;

    private readonly UiText _display;
    private readonly Func<double> _framesPerSecond;
    private readonly Func<double> _degradeMultiplier;
    private readonly Func<bool> _isVisible;

    private RetailFpsController(
        UiText display,
        Func<double> framesPerSecond,
        Func<double> degradeMultiplier,
        Func<bool> isVisible)
    {
        _display = display;
        _framesPerSecond = framesPerSecond;
        _degradeMultiplier = degradeMultiplier;
        _isVisible = isVisible;

        // The selected catalog element is authored at (1,1) inside gmSmartBoxUI.
        // Selective LayoutDesc import makes it a root, so restore that parent-relative
        // placement explicitly instead of letting it drift to (0,0).
        _display.Left = 1f;
        _display.Top = 1f;
        _display.Padding = 1f;
        _display.Selectable = false;
        _display.LinesProvider = BuildLines;
        Tick();
    }

    public UiText Display => _display;

    public static RetailFpsController? Bind(
        ImportedLayout layout,
        Func<double> framesPerSecond,
        Func<double> degradeMultiplier,
        Func<bool> isVisible)
    {
        ArgumentNullException.ThrowIfNull(layout);
        ArgumentNullException.ThrowIfNull(framesPerSecond);
        ArgumentNullException.ThrowIfNull(degradeMultiplier);
        ArgumentNullException.ThrowIfNull(isVisible);

        return layout.FindElement(DisplayElementId) is UiText display
            ? new RetailFpsController(display, framesPerSecond, degradeMultiplier, isVisible)
            : null;
    }

    /// <summary>Mirrors the retail notice-driven show/hide state each UI tick.</summary>
    public void Tick() => _display.Visible = _isVisible();

    private IReadOnlyList<UiText.Line> BuildLines()
    {
        string fps = _framesPerSecond().ToString("F2", CultureInfo.InvariantCulture);
        string degrade = _degradeMultiplier().ToString("F2", CultureInfo.InvariantCulture);
        return
        [
            new UiText.Line($"FPS: {fps}", _display.DefaultColor),
            new UiText.Line($"DEG: {degrade}", _display.DefaultColor),
        ];
    }
}