using System.Runtime.CompilerServices;
using AvParser.Core.Collecting;
using AvParser.Core.Parsing;
using AvParser.Core.Proxies;
using AvParser.Core.Settings;
using AvParser.UI.Tests.Fakes;
using AvParser.UI.ViewModels;
using Microsoft.Extensions.Logging.Abstractions;
using ReactiveUI.Primitives;
using ReactiveUI.Primitives.Concurrency;

namespace AvParser.UI.Tests;

public class CollectViewModelTests
{
    /// <summary>A runner that returns a canned stream instead of touching a network.</summary>
    private sealed class FakeRunner : ICollectRunner
    {
        public List<ParseOutcome<CollectedItem>> Results { get; } = [];

        public int Runs { get; private set; }

        public CollectOptions? LastOptions { get; private set; }

        public MediaQuery? LastQuery { get; private set; }

        public TimeSpan Delay { get; set; }

        public async IAsyncEnumerable<ParseOutcome<CollectedItem>> RunAsync(
            IMediaSource source,
            MediaQuery query,
            CollectOptions options,
            IProgress<ParseProgress>? progress,
            [EnumeratorCancellation] CancellationToken cancellationToken
        )
        {
            Runs++;
            LastOptions = options;
            LastQuery = query;

            foreach (var result in Results)
            {
                cancellationToken.ThrowIfCancellationRequested();

                if (Delay > TimeSpan.Zero)
                {
                    await Task.Delay(Delay, cancellationToken);
                }

                yield return result;
            }

            progress?.Report(new ParseProgress(Results.Count, Results.Count));
        }
    }

    private sealed class StubSource(string id, string name, bool network) : IMediaSource
    {
        public string Id => id;

        public string DisplayName => name;

        public string Description => string.Empty;

        public bool RequiresNetwork => network;

        public bool CanParse(MediaQuery input) => true;

        public async IAsyncEnumerable<ParseOutcome<MediaCandidate>> ParseAsync(
            MediaQuery input,
            IProgress<ParseProgress>? progress,
            [EnumeratorCancellation] CancellationToken cancellationToken
        )
        {
            await Task.Yield();
            yield break;
        }
    }

    private sealed class EmptyServiceProvider : IServiceProvider
    {
        public object? GetService(Type serviceType) => null;
    }

    private static CollectedItem Item(string url, CollectStatus status, long length = 4096) =>
        new(
            new MediaCandidate(new Uri(url)) { SourceId = "url-list", Ordinal = 1 },
            MediaBlob.Create(new string('a', 64), MediaKind.Png, length),
            status
        );

    private static (CollectViewModel Page, FakeRunner Runner, FakeSettingsService Settings) Build(
        AppSettings? settings = null,
        IProxyPool? proxyPool = null,
        bool includeNetworkSource = false
    )
    {
        IMediaSource[] sources = includeNetworkSource
            ? [new StubSource("url-list", "URL list", false), new StubSource("own-service", "Own service", true)]
            : [new StubSource("url-list", "URL list", false)];

        var catalog = new MediaSourceCatalog(sources, "url-list");
        var settingsService = new FakeSettingsService(settings);
        var runner = new FakeRunner();

        var page = new CollectViewModel(
            catalog,
            settingsService,
            proxyPool ?? new ProxyPool([], new FakeProxyProbe(), new ProxyOptions()),
            runner,
            new EmptyServiceProvider(),
            NullLogger<CollectViewModel>.Instance,
            ImmediateSequencer.Instance
        );

        return (page, runner, settingsService);
    }

    private static Task RunAsync(CollectViewModel page) => page.CollectCommand.Execute().ToTask();

    [Fact]
    public void The_page_opens_on_the_source_that_needs_no_proxy()
    {
        // Otherwise the app lands behind the gate before the user has asked for anything.
        var (page, _, _) = Build(includeNetworkSource: true);

        page.SelectedSource.Id.ShouldBe("url-list");
        page.IsBlockedWithoutProxy.ShouldBeFalse();
    }

    [Fact]
    public void The_last_used_source_is_restored()
    {
        var (page, _, _) = Build(
            new AppSettings { LastSourceId = "own-service", AllowDirectConnection = true },
            includeNetworkSource: true
        );

        page.SelectedSource.Id.ShouldBe("own-service");
    }

    [Fact]
    public void An_unknown_remembered_source_falls_back_instead_of_throwing()
    {
        var (page, _, _) = Build(new AppSettings { LastSourceId = "removed-in-a-past-version" });

        page.SelectedSource.Id.ShouldBe("url-list");
    }

    [Fact]
    public void Choosing_a_source_remembers_it()
    {
        var (page, _, settings) = Build(new AppSettings { AllowDirectConnection = true }, includeNetworkSource: true);

        page.SelectedSource = page.Sources.Single(source => source.Id == "own-service");

        settings.Current.LastSourceId.ShouldBe("own-service");
    }

    [Fact]
    public void Collecting_needs_something_to_collect()
    {
        var (page, _, _) = Build();
        var canExecute = true;
        using var subscription = page.CollectCommand.CanExecute.Subscribe(value => canExecute = value);

        canExecute.ShouldBeFalse();

        page.InputText = "https://example.test/a.png";
        canExecute.ShouldBeTrue();

        page.InputText = "   ";
        canExecute.ShouldBeFalse();
    }

    [Fact]
    public void An_endpoint_source_wants_an_address_not_pasted_text()
    {
        var (page, _, _) = Build(new AppSettings { AllowDirectConnection = true }, includeNetworkSource: true);
        page.SelectedSource = page.Sources.Single(source => source.Id == "own-service");

        var canExecute = true;
        using var subscription = page.CollectCommand.CanExecute.Subscribe(value => canExecute = value);

        page.InputText = "https://example.test/a.png";
        canExecute.ShouldBeFalse();

        page.EndpointText = "not an address";
        canExecute.ShouldBeFalse();

        page.EndpointText = "https://own.test/api/list";
        canExecute.ShouldBeTrue();
    }

    [Fact]
    public async Task Results_land_in_the_list_and_the_summary_counts_them()
    {
        var (page, runner, _) = Build();
        runner.Results.AddRange([
            ParseOutcome<CollectedItem>.Success(Item("https://a.test/1.png", CollectStatus.Stored)),
            ParseOutcome<CollectedItem>.Success(Item("https://a.test/2.png", CollectStatus.Duplicate)),
            ParseOutcome<CollectedItem>.Success(Item("https://a.test/3.png", CollectStatus.Skipped)),
        ]);

        page.InputText = "https://a.test/1.png";
        await RunAsync(page);

        page.Items.Count.ShouldBe(3);
        page.Errors.ShouldBeEmpty();
        var summary = page.StatusMessage.ShouldNotBeNull();
        summary.ShouldContain("1 image");
        summary.ShouldContain("already held");
        summary.ShouldContain("skipped");
    }

    [Fact]
    public async Task Failures_land_in_the_error_list_without_stopping_the_run()
    {
        var (page, runner, _) = Build();
        runner.Results.AddRange([
            ParseOutcome<CollectedItem>.Success(Item("https://a.test/1.png", CollectStatus.Stored)),
            ParseOutcome<CollectedItem>.Failure(ParseError.Create(2, "TooLarge", "too big")),
        ]);

        page.InputText = "https://a.test/1.png";
        await RunAsync(page);

        page.Items.ShouldHaveSingleItem();
        page.Errors.ShouldHaveSingleItem().Text.ShouldBe("Larger than the size limit.");
        page.StatusMessage!.ShouldContain("1 error");
    }

    [Fact]
    public async Task The_force_refetch_switch_reaches_the_runner()
    {
        var (page, runner, _) = Build();
        page.InputText = "https://a.test/1.png";
        page.ForceRefetch = true;

        await RunAsync(page);

        runner.LastOptions!.ForceRefetch.ShouldBeTrue();
    }

    [Fact]
    public async Task The_pasted_text_reaches_the_query()
    {
        var (page, runner, _) = Build();
        page.InputText = "https://a.test/1.png\nhttps://a.test/2.png";

        await RunAsync(page);

        runner.LastQuery!.Text.ShouldContain("2.png");
        runner.LastQuery.Endpoint.ShouldBeNull();
    }

    [Fact]
    public async Task A_second_run_replaces_the_previous_results()
    {
        var (page, runner, _) = Build();
        runner.Results.Add(ParseOutcome<CollectedItem>.Success(Item("https://a.test/1.png", CollectStatus.Stored)));
        page.InputText = "https://a.test/1.png";

        await RunAsync(page);
        await RunAsync(page);

        page.Items.ShouldHaveSingleItem();
    }

    [Fact]
    public void A_local_source_runs_with_no_proxy_at_all()
    {
        var (page, _, _) = Build();

        page.IsBlockedWithoutProxy.ShouldBeFalse();
    }

    [Fact]
    public void A_network_source_is_blocked_while_nothing_is_live()
    {
        var (page, _, _) = Build(new AppSettings { LastSourceId = "own-service" }, includeNetworkSource: true);

        page.IsBlockedWithoutProxy.ShouldBeTrue();

        var canExecute = true;
        using var subscription = page.CollectCommand.CanExecute.Subscribe(value => canExecute = value);
        page.EndpointText = "https://own.test/api/list";

        canExecute.ShouldBeFalse();
    }

    [Fact]
    public void Allowing_direct_connections_lifts_the_gate()
    {
        var (page, _, _) = Build(
            new AppSettings { LastSourceId = "own-service", AllowDirectConnection = true },
            includeNetworkSource: true
        );

        page.IsBlockedWithoutProxy.ShouldBeFalse();
    }

    [Fact]
    public async Task A_network_source_runs_once_a_proxy_answers()
    {
        var endpoint = new ProxyEndpoint(ProxyProtocol.Http, "1.2.3.4", 8080);
        var pool = new ProxyPool(
            [new FakeProxySource([endpoint])],
            new FakeProxyProbe().Set(endpoint, alive: true),
            new ProxyOptions()
        );

        var (page, _, _) = Build(new AppSettings { LastSourceId = "own-service" }, pool, includeNetworkSource: true);
        page.IsBlockedWithoutProxy.ShouldBeTrue();

        await pool.RefreshAsync(TestContext.Current.CancellationToken);
        await pool.WarmUpAsync(1, cancellationToken: TestContext.Current.CancellationToken);
        page.RefreshProxyGate();

        page.IsBlockedWithoutProxy.ShouldBeFalse();
    }

    [Fact]
    public void Switching_away_from_a_network_source_lifts_the_gate()
    {
        var (page, _, _) = Build(new AppSettings { LastSourceId = "own-service" }, includeNetworkSource: true);
        page.IsBlockedWithoutProxy.ShouldBeTrue();

        page.SelectedSource = page.Sources.Single(source => source.Id == "url-list");

        page.IsBlockedWithoutProxy.ShouldBeFalse();
    }

    [Fact]
    public void Sizes_read_the_way_a_file_manager_shows_them()
    {
        CollectedItemViewModel.FormatSize(0).ShouldBeEmpty();
        CollectedItemViewModel.FormatSize(512).ShouldBe("512 B");
        CollectedItemViewModel.FormatSize(2048).ShouldBe("2 KB");
        CollectedItemViewModel.FormatSize(1024 * 1024 * 3).ShouldBe("3 MB");
    }
}