using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using Xunit;
using ytLive.Models;
using ytLive.Services;

namespace ytLive.Tests;

/// <summary>
/// The rate the app suggests next session, from real sessions — and the two rules that keep it from
/// becoming a nuisance: five sessions of evidence per tier and encoder, a 10% gap before asking for
/// more, and a lower bar for backing off.
/// </summary>
public class RateHistoryTests
{
    private static SessionRateResult Session(
        double rated, double settled = -1, int steps = 0, string tier = "1080p60", string encoder = "h264_nvenc")
        => new(tier, encoder, rated, settled < 0 ? rated : settled, steps);

    [Fact]
    public void Suggestions_need_five_sessions_of_the_same_tier_and_encoder_and_persist_with_them()
    {
        // Four sessions is not evidence.
        Assert.Null(RateHistory.Suggest(
            Enumerable.Range(0, 4).Select(_ => Session(15)), "1080p60", "h264_nvenc", 12));

        // Five clean sessions holding 15 against a 12 target: worth asking, and the ask is 10% up.
        var raised = RateHistory.Suggest(
            Enumerable.Range(0, 5).Select(_ => Session(15)), "1080p60", "h264_nvenc", 12);
        Assert.NotNull(raised);
        Assert.True(raised!.Value.Raise);
        Assert.Equal(15, raised.Value.Mbps);

        // The same evidence means nothing below the threshold (12 → 12.6 is under 10%).
        Assert.Null(RateHistory.Suggest(
            Enumerable.Range(0, 5).Select(_ => Session(13)), "1080p60", "h264_nvenc", 12));

        // A different encoder is a different machine: no suggestion.
        Assert.Null(RateHistory.Suggest(
            Enumerable.Range(0, 5).Select(_ => Session(15)), "1080p60", "h264_qsv", 12));

        // Three step-downs out of five asks to back off to the settled median, faster than it asks to
        // climb — fixing damage should not wait for a 10% gap.
        var lowered = RateHistory.Suggest(
            new[]
            {
                Session(12, 9.6, 1), Session(12, 8.0, 2), Session(12), Session(12, 7.2, 1), Session(12),
            },
            "1080p60", "h264_nvenc", 12);
        Assert.NotNull(lowered);
        Assert.False(lowered!.Value.Raise);
        Assert.Equal(9.6, lowered.Value.Mbps);   // median of 9.6, 8.0, 12, 7.2, 12

        // And the storage form survives a round trip through the settings row, which is where the
        // evidence actually lives between runs.
        var db = Path.Combine(Path.GetTempPath(), $"llamacasty-rate-history-{Guid.NewGuid():N}.db");
        using (var store = new LayoutStore(db))
        {
            foreach (var entry in Enumerable.Range(0, 5).Select(_ => Session(15)))
                store.AppendRateHistory(entry);

            var reloaded = store.LoadRateHistory();
            Assert.Equal(5, reloaded.Count);
            Assert.Equal(Session(15), reloaded[0]);
            Assert.Equal(15, RateHistory.Suggest(reloaded, "1080p60", "h264_nvenc", 12)!.Value.Mbps);
        }
        try { File.Delete(db); } catch (IOException) { }
    }
}