using VideoDownloader.App.Browser.Features;

namespace VideoDownloader.Tests.Browser;

/// <summary>페이지 다운로드 추상화(다운로드 매니저 UI 의 로직 코어) — fake op 로 검증.</summary>
public interface IFakeOpHost { }

public class PageDownloadTrackerTests
{
    private sealed class FakeOp : IDownloadOperation
    {
        public string Uri { get; set; } = "https://x.test/file.zip";
        public string FileName { get; set; } = "file.zip";
        public long BytesReceived { get; set; }
        public long TotalBytesToReceive { get; set; } = 1000;
        public string State { get; set; } = "InProgress";
        public bool Paused, Resumed, Cancelled;

        public event Action? Changed;
        public void Raise() => Changed?.Invoke();

        public void Pause() { Paused = true; State = "Paused"; Raise(); }
        public void Resume() { Resumed = true; State = "InProgress"; Raise(); }
        public void Cancel() { Cancelled = true; State = "Cancelled"; Raise(); }
    }

    [Fact]
    public void Add는_항목을_등록하고_최근순_정렬한다()
    {
        var t = new PageDownloadTracker();
        var a = new FakeOp { FileName = "a.zip" };
        var b = new FakeOp { FileName = "b.zip" };
        t.Add(a, a.FileName);
        t.Add(b, b.FileName);
        Assert.Equal(2, t.Items.Count);
        Assert.Equal("b.zip", t.Items[0].FileName); // 최신 우선
    }

    [Fact]
    public void 진행률과_속도를_계산한다()
    {
        var t = new PageDownloadTracker();
        var op = new FakeOp { TotalBytesToReceive = 1000 };
        var item = t.Add(op, "f.zip");

        item.UpdateSpeed(500, TimeSpan.FromSeconds(2)); // 500B/2s = 250 B/s
        Assert.Equal(50.0, item.Percent, 2);
        Assert.Equal(250, item.BytesPerSecond);
        Assert.Equal("250.0 B/s", item.SpeedText);
    }

    [Fact]
    public void 속도_단위는_KB_MB로_표시된다()
    {
        var t = new PageDownloadTracker();
        var item = t.Add(new FakeOp { TotalBytesToReceive = 10_000_000 }, "f");

        item.UpdateSpeed(0, TimeSpan.FromSeconds(1)); // 초기
        Assert.Equal("—", item.SpeedText);

        item = t.Add(new FakeOp { TotalBytesToReceive = 10_000_000 }, "g");
        item.UpdateSpeed(2048 * 100, TimeSpan.FromSeconds(1)); // 200 KB/s
        Assert.Equal("200.0 KB/s", item.SpeedText);

        item = t.Add(new FakeOp { TotalBytesToReceive = 10_000_000 }, "h");
        item.UpdateSpeed(3 * 1024 * 1024L, TimeSpan.FromSeconds(1)); // 3 MB/s
        Assert.Equal("3.0 MB/s", item.SpeedText);
    }

    [Fact]
    public void Pause_Resume_Cancel_위임()
    {
        var t = new PageDownloadTracker();
        var op = new FakeOp();
        var item = t.Add(op, "f");

        t.Pause(item); t.Resume(item); t.Cancel(item);
        Assert.True(op.Paused && op.Resumed && op.Cancelled);
    }

    [Fact]
    public void 완료_항목은_ClearCompleted로_일괄_제거()
    {
        var t = new PageDownloadTracker();
        var done = new FakeOp { State = "Completed" };
        var running = new FakeOp { State = "InProgress" };
        t.Add(done, "d"); t.Add(running, "r");

        t.ClearCompleted();
        Assert.Single(t.Items);
        Assert.Equal("r", t.Items[0].FileName);
    }

    [Fact]
    public void 취소된_항목도_ClearCompleted로_제거된다()
    {
        var t = new PageDownloadTracker();
        var c = new FakeOp { State = "Interrupted" };
        t.Add(c, "c");
        t.ClearCompleted();
        Assert.Empty(t.Items);
    }
}