namespace ytLive.Services;

/// <summary>
/// Identifies which monitor holds a full-screen window (a game/app running
/// borderless or exclusive fullscreen). Seam so ScreenCaptureManager is
/// testable without Win32 interop.
/// </summary>
public interface IFullScreenDetector
{
    /// <summary>
    /// The index of the monitor a full-screen foreground window covers, or null
    /// when the foreground window is windowed, missing, or one of our own.
    /// </summary>
    int? GetForegroundFullScreenMonitorIndex();

    /// <summary>Index of the primary (taskbar-hosting) monitor.</summary>
    int PrimaryMonitorIndex();

    /// <summary>All monitors in capture-key order (enumeration order).</summary>
    IReadOnlyList<DisplayInfo> GetDisplays();

    /// <summary>
    /// Raised on the UI thread whenever the foreground window changes.
    /// Payload is the full-screen monitor index, or null when the new
    /// foreground window is not full-screen / is one of our own windows.
    /// </summary>
    event Action<int?>? FullscreenMonitorChanged;

    /// <summary>Hook EVENT_SYSTEM_FOREGROUND so <see cref="FullscreenMonitorChanged"/> fires.</summary>
    void StartWatching();

    /// <summary>Unhook the foreground listener.</summary>
    void StopWatching();
}