using System.Diagnostics;
using SQLInsight.Core.Servers;

namespace SQLInsight.Servers.Tests;

/// <summary>What the agent remembers per server, and that a server that does not answer never holds the agent longer than its deadline.</summary>
public class ServerDeadlineTests
{
    private sealed class Clock(DateTimeOffset now) : TimeProvider
    {
        public DateTimeOffset Now { get; set; } = now;

        public override DateTimeOffset GetUtcNow() => Now;
    }

    [Fact]
    public void A_fact_about_a_server_is_remembered_for_a_while_then_tried_again()
    {
        var clock = new Clock(new DateTimeOffset(2026, 10, 2, 12, 0, 0, TimeSpan.Zero));
        var memory = new ServerHostMemory(clock, TimeSpan.FromHours(1));

        memory.Remember("aos01.firma.local", "protocol", "DCOM");
        clock.Now = clock.Now.AddMinutes(59);
        Assert.Equal("DCOM", memory.Recall<string>("AOS01.firma.local", "protocol"));
        Assert.Null(memory.Recall<string>("aos01.firma.local", "eventlog-rpc"));

        clock.Now = clock.Now.AddMinutes(1);
        Assert.Null(memory.Recall<string>("aos01.firma.local", "protocol"));

        memory.Remember("aos01", "protocol", "DCOM");
        memory.Forget("aos01", "protocol");
        Assert.Null(memory.Recall<string>("aos01", "protocol"));
    }

    [Fact]
    public void Operation_timeouts_are_bounded()
    {
        Assert.Equal(TimeSpan.FromSeconds(5), ServerConnectionOptions.BoundTimeout(TimeSpan.Zero));
        Assert.Equal(TimeSpan.FromSeconds(5), ServerConnectionOptions.BoundTimeout(TimeSpan.FromSeconds(-1)));
        Assert.Equal(TimeSpan.FromMinutes(5), ServerConnectionOptions.BoundTimeout(TimeSpan.FromHours(3)));
        Assert.Equal(TimeSpan.FromSeconds(45), ServerConnectionOptions.BoundTimeout(TimeSpan.FromSeconds(45)));
    }

    /// <summary>A server that accepts the connection, then never answers any area (it honours cancellation, as the CIM source makes sure it is).</summary>
    private sealed class HungServer(bool hangOnConnect = false) : IWindowsServerSource, IWindowsServerSession
    {
        public string Protocol => "DCOM";

        public string? ProtocolNote => null;

        public async Task<IWindowsServerSession> ConnectAsync(string host, CancellationToken cancellationToken)
        {
            if (hangOnConnect)
            {
                await Hang(cancellationToken);
            }

            return this;
        }

        private static Task Hang(CancellationToken cancellationToken) => Task.Delay(Timeout.Infinite, cancellationToken);

        public async Task<ServerOsInfo> GetOperatingSystemAsync(CancellationToken cancellationToken)
        {
            await Hang(cancellationToken);
            throw new UnreachableException();
        }

        public Task<ServerPerformanceRaw> GetPerformanceAsync(DateTimeOffset now, CancellationToken cancellationToken) => throw new UnreachableException();

        public Task<IReadOnlyList<ServerDisk>> GetDisksAsync(CancellationToken cancellationToken) =>
            Task.FromResult<IReadOnlyList<ServerDisk>>([new ServerDisk(@"C:\", null, "NTFS", 100, 50)]);

        public async Task<IReadOnlyList<ServerService>> GetServicesAsync(CancellationToken cancellationToken)
        {
            await Hang(cancellationToken);
            throw new UnreachableException();
        }

        public Task<ServerService?> GetServiceAsync(string name, CancellationToken cancellationToken) => throw new UnreachableException();

        public async Task<ServerEventRead> GetEventsAsync(IReadOnlyDictionary<string, DateTimeOffset> since, int max, CancellationToken cancellationToken)
        {
            await Hang(cancellationToken);
            throw new UnreachableException();
        }

        public async Task<ServerTaskRead> GetTasksAsync(Func<string, bool> watch, int maxWatched, TimeSpan budget, CancellationToken cancellationToken)
        {
            await Hang(cancellationToken);
            throw new UnreachableException();
        }

        public void Dispose()
        {
        }
    }

    [Fact]
    public async Task A_test_of_a_server_that_hangs_ends_at_its_deadline_with_every_area_said()
    {
        var watch = Stopwatch.StartNew();
        var result = await WindowsServerTester.TestAsync(new HungServer(), "aos01", null, DateTimeOffset.UtcNow, TimeSpan.FromMilliseconds(300), CancellationToken.None);
        var hungAtConnect = await WindowsServerTester.TestAsync(new HungServer(hangOnConnect: true), "aos01", null, DateTimeOffset.UtcNow, TimeSpan.FromMilliseconds(300),
            CancellationToken.None);

        Assert.True(watch.Elapsed < TimeSpan.FromSeconds(30), $"took {watch.Elapsed}");
        Assert.True(result.Reachable);
        Assert.Equal(ServerArea.All, result.Areas.Select(a => a.Area));
        Assert.All(result.Areas, a => Assert.False(a.Ok));
        Assert.All(result.Areas, a => Assert.Contains("svarede ikke inden for", a.Detail, StringComparison.Ordinal));
        Assert.False(hungAtConnect.Reachable);
        Assert.Contains("svarede ikke inden for", hungAtConnect.Error, StringComparison.Ordinal);
    }

    [Fact]
    public async Task Stopping_the_agent_still_cancels_a_test()
    {
        using var stop = new CancellationTokenSource(TimeSpan.FromMilliseconds(200));

        await Assert.ThrowsAnyAsync<OperationCanceledException>(() =>
            WindowsServerTester.TestAsync(new HungServer(hangOnConnect: true), "aos01", null, DateTimeOffset.UtcNow, TimeSpan.FromMinutes(5), stop.Token));
    }
}