using System.Linq;
using System.Threading;
using Xunit;
using ytLive.Models;
using ytLive.Services.Compositor;

namespace ytLive.Tests;

/// <summary>The strip's cache is a performance rule with teeth: it must rebuild when a displayed
/// value moves and must NOT rebuild otherwise, or the compositor pays for a raster per tick into
/// pixels that did not change.</summary>
public class ScoreboardPresenterTests
{
    private static ChatMessage Member(string name) => new() { Kind = ChatEventKind.NewMember, AuthorName = name };

    [Fact]
    public void The_strip_rebuilds_only_when_a_displayed_value_moves()
    {
        System.Exception? failure = null;
        var thread = new Thread(() =>
        {
            try
            {
                var recorder = new ScoreboardRecorder();
                var tiles = new ScoreboardTiles
                {
                    SuperChats = false, WatchHours = false, Subscribers = false,
                    NewMembers = true, Milestones = false, LastMember = true,
                    LastSuperChat = false, LastGift = false,
                };
                var presenter = new ScoreboardPresenter(recorder, new ScoreboardStyle());
                presenter.SetTiles(tiles);

                // Before a session: nothing counted, nothing to draw.
                Assert.Null(presenter.Frame);

                recorder.StartSession();
                recorder.Record(Member("First"));
                var first = presenter.Frame;
                Assert.NotNull(first);

                // No tick, no change: the same pixels come back (the run is cached).
                Assert.Equal(first!.BgraPixels, presenter.Frame!.BgraPixels);

                // A TICK moves the window: the pixels must differ.
                presenter.Advance(0.5);
                var ticked = presenter.Frame;
                Assert.NotNull(ticked);
                Assert.NotEqual(first.BgraPixels, ticked!.BgraPixels);

                // SPEED is a real dial: the same elapsed time at twice the speed moves twice as far,
                // so the window lands somewhere else.
                var slow = new ScoreboardPresenter(recorder, new ScoreboardStyle()) { PixelsPerSecond = 60 };
                var fast = new ScoreboardPresenter(recorder, new ScoreboardStyle()) { PixelsPerSecond = 120 };
                slow.SetTiles(tiles);
                fast.SetTiles(tiles);
                slow.Advance(1.0);
                fast.Advance(1.0);
                Assert.NotEqual(slow.Frame!.BgraPixels, fast.Frame!.BgraPixels);

                // A visible change re-rasterises the run.
                recorder.Record(Member("Second"));
                var second = presenter.Frame;
                Assert.NotNull(second);
                Assert.NotEqual(ticked.BgraPixels, second!.BgraPixels);

                // A gift-recipient event changes nothing displayed: same window, same pixels.
                var beforeGift = presenter.Frame!.BgraPixels.ToArray();
                recorder.Record(new ChatMessage { Kind = ChatEventKind.GiftReceived, AuthorName = "Recipient" });
                Assert.Equal(beforeGift, presenter.Frame!.BgraPixels);

                // Disabling every tile returns no frame, and the layer draws nothing.
                presenter.SetTiles(ScoreboardTiles.None);
                Assert.Null(presenter.Frame);
            }
            catch (System.Exception ex) { failure = ex; }
        });
        thread.SetApartmentState(ApartmentState.STA);
        thread.Start();
        thread.Join();
        Assert.Null(failure);
    }
}