using System.Net;
using System.Net.Sockets;
using Nonemm.Core;

namespace Nonemm.Network.Tests;

/// Two links talking to each other over loopback. The stations are named by
/// hand rather than found by a beacon: a broadcast test would depend on the
/// machine's interfaces, and what is being tested here is what happens after
/// two stations have found each other.
public class StationLinkTests
{
    private const string Version = "1.0.11364";

    private static readonly TimeSpan Patience = TimeSpan.FromSeconds(10);

    [Fact]
    public async Task AContactReachesTheOtherStation()
    {
        (int onePort, int twoPort) = SparePorts();
        using StationLink one = new("RUN-PC", Version, stationNumber: 1, port: onePort);
        using StationLink two = new("MULT-PC", Version, stationNumber: 2, port: twoPort);
        one.Start();
        two.Start();
        ContactUpdate? arrived = null;
        two.UpdateArrived += (_, update) => arrived = update;
        one.AddStation("MULT-PC", "127.0.0.1", twoPort);
        await WaitForAsync(() => one.Stations.Any(s => s is { IsMine: false, IsConnected: true }));

        await one.SendLoggedAsync(Contact());

        await WaitForAsync(() => arrived is not null);
        ContactLogged logged = Assert.IsType<ContactLogged>(arrived);
        Assert.Equal("G3XYZ", logged.Qso.Call.Text);
        Assert.Equal("RUN-PC", logged.Qso.StationName);
        Assert.Equal(1, logged.Qso.NetworkedComputerNumber);
    }

    /// The first message on a new connection says which station of the entry
    /// the sender is, so the other end can show its number.
    [Fact]
    public async Task ConnectingSaysWhichStationNumberThisIs()
    {
        (int onePort, int twoPort) = SparePorts();
        using StationLink one = new("RUN-PC", Version, stationNumber: 1, port: onePort);
        using StationLink two = new("MULT-PC", Version, stationNumber: 7, port: twoPort);
        one.Start();
        two.Start();
        one.AddStation("MULT-PC", "127.0.0.1", twoPort);
        await WaitForAsync(() =>
            two.Stations.FirstOrDefault(s => s.ComputerName == "RUN-PC")?.StationNumber == 1);

        NetworkedStation? seen = two.Stations.FirstOrDefault(s => s.ComputerName == "RUN-PC");
        Assert.Equal(1, seen?.StationNumber);
        Assert.Equal("IAM", seen?.LastMessage);
    }

    /// The band a station is on is what the status window shows and what the
    /// band-change rule counts.
    /// N1MM carries the frequency in hundredths of a kilohertz, in its own
    /// `FREQ` message. A tenth of a hertz survives the trip.
    [Fact]
    public async Task WhereAStationIsTunedReachesTheOthers()
    {
        (int onePort, int twoPort) = SparePorts();
        using StationLink one = new("RUN-PC", Version, stationNumber: 1, port: onePort);
        using StationLink two = new("MULT-PC", Version, stationNumber: 2, port: twoPort);
        one.Start();
        two.Start();
        one.AddStation("MULT-PC", "127.0.0.1", twoPort);
        await WaitForAsync(() => one.Stations.Any(s => s is { IsMine: false, IsConnected: true }));

        await one.SendFrequencyAsync(Frequency.FromKilohertz(21_025.25));

        await WaitForAsync(() =>
            two.Stations.FirstOrDefault(s => s.ComputerName == "RUN-PC")?.Band?.Name == "15M");
        NetworkedStation? seen = two.Stations.FirstOrDefault(s => s.ComputerName == "RUN-PC");
        Assert.Equal("15M", seen?.Band?.Name);
        Assert.Equal(21_025.25, seen?.Frequency.Kilohertz ?? 0, 2);
    }

    /// What a station is sending is what the other operators read in the `Msg`
    /// column, and N1MM carries it in the transmit message.
    [Fact]
    public async Task WhatAStationIsSendingReachesTheOthers()
    {
        (int onePort, int twoPort) = SparePorts();
        using StationLink one = new("RUN-PC", Version, stationNumber: 1, port: onePort);
        using StationLink two = new("MULT-PC", Version, stationNumber: 2, port: twoPort);
        one.Start();
        two.Start();
        one.AddStation("MULT-PC", "127.0.0.1", twoPort);
        await WaitForAsync(() => one.Stations.Any(s => s is { IsMine: false, IsConnected: true }));

        await one.SendTransmittingAsync(true, "F1 CQ", isRun2: true);

        await WaitForAsync(() =>
            two.Stations.FirstOrDefault(s => s.ComputerName == "RUN-PC")?.IsTransmitting == true);
        NetworkedStation? seen = two.Stations.FirstOrDefault(s => s.ComputerName == "RUN-PC");
        Assert.Equal("F1 CQ", seen?.Message);
        Assert.True(seen?.IsRun2);

        await one.SendTransmittingAsync(false);

        await WaitForAsync(() =>
            two.Stations.FirstOrDefault(s => s.ComputerName == "RUN-PC")?.IsTransmitting == false);
        Assert.Equal("", two.Stations.First(s => s.ComputerName == "RUN-PC").Message);
    }

    /// A pass frequency is the frequency and nothing else, in hundredths of a
    /// kilohertz.
    [Fact]
    public async Task APassFrequencyReachesTheOthers()
    {
        (int onePort, int twoPort) = SparePorts();
        using StationLink one = new("RUN-PC", Version, stationNumber: 1, port: onePort);
        using StationLink two = new("MULT-PC", Version, stationNumber: 2, port: twoPort);
        one.Start();
        two.Start();
        one.AddStation("MULT-PC", "127.0.0.1", twoPort);
        await WaitForAsync(() => one.Stations.Any(s => s is { IsMine: false, IsConnected: true }));

        await one.SendPassAsync(Frequency.FromKilohertz(14_205.5));

        await WaitForAsync(() =>
            two.Stations.FirstOrDefault(s => s.ComputerName == "RUN-PC")?.PassFrequency.Hertz > 0);
        Assert.Equal(
            14_205.5,
            two.Stations.First(s => s.ComputerName == "RUN-PC").PassFrequency.Kilohertz,
            1);
    }

    /// A station that reconnects is told when the other one last worked
    /// somebody, and asks for what it is missing without anybody pressing a
    /// button.
    [Fact]
    public async Task AStationThatIsBehindResynchronisesOnItsOwn()
    {
        (int onePort, int twoPort) = SparePorts();
        using StationLink one = new("RUN-PC", Version, stationNumber: 1, port: onePort);
        using StationLink two = new("MULT-PC", Version, stationNumber: 2, port: twoPort);
        DateTime hour = DateTime.UtcNow.AddMinutes(-30);
        Qso first = Contact() with { TimestampUtc = hour, Id = "first" };
        Qso later = Contact() with
        {
            TimestampUtc = hour.AddMinutes(10),
            Call = Callsign.Parse("DL1ABC"),
            Id = "later",
        };
        one.Log = new FakeLog([first, later]);
        // MULT-PC has the first contact and missed the one after it
        FakeLog multLog = new([first]);
        two.Log = multLog;
        two.UpdateArrived += (_, update) => multLog.Take(update);
        one.Start();
        two.Start();
        one.AddStation("MULT-PC", "127.0.0.1", twoPort);
        two.AddStation("RUN-PC", "127.0.0.1", onePort);

        await WaitForAsync(() => multLog.All.Count == 2);
        Assert.Equal(["DL1ABC", "G3XYZ"], multLog.All.Select(q => q.Call.Text).Order());
    }

    /// The status message carries what the network status window shows: the
    /// operator, the rates, the pass frequency and which radio is running.
    [Fact]
    public async Task AStationSaysHowItIsDoing()
    {
        (int onePort, int twoPort) = SparePorts();
        using StationLink one = new("RUN-PC", Version, stationNumber: 1, port: onePort);
        using StationLink two = new("MULT-PC", Version, stationNumber: 2, port: twoPort);
        one.Start();
        two.Start();
        one.AddStation("MULT-PC", "127.0.0.1", twoPort);
        await WaitForAsync(() => one.Stations.Any(s => s is { IsMine: false, IsConnected: true }));

        await one.SendStatusAsync(new StationStatus(
            Frequency.FromKilohertz(14_205.5),
            Frequency.FromKilohertz(21_025.1),
            IsRunning: true,
            "OM3RM",
            Modes.Rtty,
            Last10: 120,
            Last100: 84,
            "MULTI-ONE",
            "TWO",
            IsRun2: true));

        await WaitForAsync(() =>
            two.Stations.FirstOrDefault(s => s.ComputerName == "RUN-PC")?.Last10 == 120);
        NetworkedStation? seen = two.Stations.FirstOrDefault(s => s.ComputerName == "RUN-PC");
        Assert.Equal(120, seen?.Last10);
        Assert.Equal(84, seen?.Last100);
        Assert.Equal("OM3RM", seen?.Operator);
        Assert.Equal("RTTY", seen?.Mode?.Name);
        Assert.Equal(21_025.1, seen?.Frequency.Kilohertz ?? 0, 1);
        Assert.Equal(14_205.5, seen?.PassFrequency.Kilohertz ?? 0, 1);
        Assert.True(seen?.IsRunning);
        Assert.True(seen?.IsRun2);
    }

    /// A connection the operator closed stays closed: a beacon from that
    /// station would otherwise open it again within ten seconds.
    [Fact]
    public async Task AClosedConnectionStaysClosedUntilItIsOpenedAgain()
    {
        (int onePort, int twoPort) = SparePorts();
        using StationLink one = new("RUN-PC", Version, stationNumber: 1, port: onePort);
        using StationLink two = new("MULT-PC", Version, stationNumber: 2, port: twoPort);
        one.Start();
        two.Start();
        NetworkedStation station = one.AddStation("MULT-PC", "127.0.0.1", twoPort);
        await WaitForAsync(() => station.IsConnected);

        one.Close(station);
        Assert.False(station.IsConnected);
        Assert.Equal(0, await one.SendTalkAsync("anybody there"));

        one.Open(station);
        await WaitForAsync(() => station.IsConnected);
        Assert.True(station.IsConnected);
    }

    [Fact]
    public async Task ChatReachesTheOtherOperator()
    {
        (int onePort, int twoPort) = SparePorts();
        using StationLink one = new("RUN-PC", Version, stationNumber: 1, port: onePort);
        using StationLink two = new("MULT-PC", Version, stationNumber: 2, port: twoPort);
        one.Start();
        two.Start();
        string? said = null;
        two.TalkArrived += (_, text) => said = text;
        one.AddStation("MULT-PC", "127.0.0.1", twoPort);
        await WaitForAsync(() => one.Stations.Any(s => s is { IsMine: false, IsConnected: true }));

        await one.SendTalkAsync("qsy 20");

        await WaitForAsync(() => said is not null);
        Assert.Equal("[RUN-PC] qsy 20", said);
    }

    /// An echo request is answered without anybody asking, which is how N1MM
    /// measures the round trip to each station.
    [Fact]
    public async Task AnEchoRequestIsAnswered()
    {
        (int onePort, int twoPort) = SparePorts();
        using StationLink one = new("RUN-PC", Version, stationNumber: 1, port: onePort);
        using StationLink two = new("MULT-PC", Version, stationNumber: 2, port: twoPort);
        one.Start();
        two.Start();
        one.AddStation("MULT-PC", "127.0.0.1", twoPort);
        two.AddStation("RUN-PC", "127.0.0.1", onePort);
        await WaitForAsync(() =>
            one.Stations.Any(s => s is { IsMine: false, IsConnected: true })
            && two.Stations.Any(s => s is { IsMine: false, IsConnected: true }));

        await one.SendEchoRequestAsync();

        await WaitForAsync(() =>
            one.Stations.FirstOrDefault(s => s.ComputerName == "MULT-PC")?.EchoTime is not null);
        Assert.NotNull(one.Stations.FirstOrDefault(s => s.ComputerName == "MULT-PC")?.EchoTime);
    }

    /// This computer is in its own list, the way N1MM shows it, so an operator
    /// can read its station number and version off the same window.
    [Fact]
    public void ThisComputerIsInItsOwnStationList()
    {
        using StationLink link = new("RUN-PC", Version, stationNumber: 3, port: SparePorts().One);

        NetworkedStation mine = Assert.Single(link.Stations);

        Assert.True(mine.IsMine);
        Assert.Equal("RUN-PC", mine.ComputerName);
        Assert.Equal(3, mine.StationNumber);
        Assert.Equal(Version, mine.Version);
    }

    /// A message that reached nobody says so, rather than looking as though it
    /// went out.
    [Fact]
    public async Task SendingWithNoStationsConnectedReachesNobody()
    {
        using StationLink link = new("RUN-PC", Version, port: SparePorts().One);
        link.Start();

        Assert.Equal(0, await link.SendLoggedAsync(Contact()));
    }

    /// A station that missed an hour of the contest asks for it and gets it.
    /// The other station is the authority on the contacts it made: it tells the
    /// asker to drop what it holds for that hour and sends the hour again.
    [Fact]
    public async Task AResyncFillsInWhatAStationMissed()
    {
        (int onePort, int twoPort) = SparePorts();
        using StationLink one = new("RUN-PC", Version, stationNumber: 1, port: onePort);
        using StationLink two = new("MULT-PC", Version, stationNumber: 2, port: twoPort);
        DateTime hour = new(2026, 5, 30, 12, 0, 0, DateTimeKind.Utc);
        FakeLog runLog = new([Contact() with { TimestampUtc = hour }, Contact() with { TimestampUtc = hour.AddMinutes(20), Call = Callsign.Parse("DL1ABC"), Id = Qso.NewId() }]);
        FakeLog multLog = new([]);
        one.Log = runLog;
        two.Log = multLog;
        two.UpdateArrived += (_, update) => multLog.Take(update);
        one.Start();
        two.Start();
        // each station opens its own connection, which is N1MM's arrangement:
        // an answer goes back over the one this end opened
        one.AddStation("MULT-PC", "127.0.0.1", twoPort);
        two.AddStation("RUN-PC", "127.0.0.1", onePort);
        await WaitForAsync(() =>
            one.Stations.Any(s => s is { IsMine: false, IsConnected: true })
            && two.Stations.Any(s => s is { IsMine: false, IsConnected: true }));
        NetworkedStation runStation = two.Stations.First(s => s.ComputerName == "RUN-PC");

        two.StartResync(runStation, hour, hour.AddHours(1));

        await WaitForAsync(() => !runStation.IsResyncing && multLog.All.Count == 2);
        Assert.Equal(["DL1ABC", "G3XYZ"], multLog.All.Select(q => q.Call.Text).Order());
        Assert.Equal("Resync complete", runStation.ResyncStatus);
        Assert.True(runStation.HoursOk > 0, "the hour that was sent again should now agree");
    }

    /// A station whose log already agrees is told nothing but the answer.
    [Fact]
    public async Task AResyncOfAnHourThatAgreesSendsNoContacts()
    {
        (int onePort, int twoPort) = SparePorts();
        using StationLink one = new("RUN-PC", Version, stationNumber: 1, port: onePort);
        using StationLink two = new("MULT-PC", Version, stationNumber: 2, port: twoPort);
        DateTime hour = new(2026, 5, 30, 12, 0, 0, DateTimeKind.Utc);
        Qso shared = Contact() with { TimestampUtc = hour };
        one.Log = new FakeLog([shared]);
        FakeLog multLog = new([shared]);
        two.Log = multLog;
        int arrived = 0;
        two.UpdateArrived += (_, update) =>
        {
            arrived++;
            multLog.Take(update);
        };
        one.Start();
        two.Start();
        // each station opens its own connection, which is N1MM's arrangement:
        // an answer goes back over the one this end opened
        one.AddStation("MULT-PC", "127.0.0.1", twoPort);
        two.AddStation("RUN-PC", "127.0.0.1", onePort);
        await WaitForAsync(() =>
            one.Stations.Any(s => s is { IsMine: false, IsConnected: true })
            && two.Stations.Any(s => s is { IsMine: false, IsConnected: true }));
        NetworkedStation runStation = two.Stations.First(s => s.ComputerName == "RUN-PC");

        two.StartResync(runStation, hour, hour.AddHours(1));

        await WaitForAsync(() => !runStation.IsResyncing);
        Assert.Equal(0, arrived);
        Assert.Equal(0, runStation.HoursFailed);
        Assert.Single(multLog.All);
    }

    /// A log a resync can ask about, and that takes what a resync sends it.
    private sealed class FakeLog(IEnumerable<Qso> contacts) : ContactLog
    {
        private readonly List<Qso> qsos = [.. contacts];

        public string ContestName => "CQWW";

        public string MyCall => "OM3XYZ";

        public IReadOnlyList<Qso> All => qsos;

        public IReadOnlyList<Qso> Contacts(string computerName, DateTime fromUtc, TimeSpan length) =>
            LogChecksum.Block(qsos, computerName, fromUtc, length);

        public DateTime LastContactUtc(string computerName) =>
            qsos.Where(q => string.Equals(q.StationName, computerName, StringComparison.OrdinalIgnoreCase))
                .Select(q => q.TimestampUtc)
                .DefaultIfEmpty(default)
                .Max();

        public DateTime FirstContactUtc =>
            qsos.Select(q => q.TimestampUtc).DefaultIfEmpty(default).Min();

        public void Take(ContactUpdate update)
        {
            switch (update)
            {
                case ContactLogged logged when !qsos.Any(q => q.Id == logged.Qso.Id):
                    qsos.Add(logged.Qso);
                    break;
                case ContactsCleared cleared:
                    qsos.RemoveAll(q =>
                        string.Equals(q.StationName, cleared.StationName, StringComparison.OrdinalIgnoreCase)
                        && q.TimestampUtc >= cleared.FromUtc
                        && q.TimestampUtc < cleared.FromUtc + cleared.Length);
                    break;
            }
        }
    }

    private static async Task WaitForAsync(Func<bool> ready)
    {
        DateTime giveUp = DateTime.UtcNow + Patience;
        while (!ready() && DateTime.UtcNow < giveUp)
        {
            await Task.Delay(5);
        }
    }

    /// Two ports nothing else is on, so the tests do not fight each other or
    /// the N1MM the machine may be running.
    ///
    /// Both are taken before either is let go. Asking twice in a row does not
    /// work: the second ask often gets the port the first one has just given
    /// back, and two links on one port leaves the second without a listener.
    private static (int One, int Two) SparePorts()
    {
        TcpListener first = new(IPAddress.Loopback, 0);
        TcpListener second = new(IPAddress.Loopback, 0);
        first.Start();
        second.Start();
        int one = ((IPEndPoint)first.LocalEndpoint).Port;
        int two = ((IPEndPoint)second.LocalEndpoint).Port;
        first.Stop();
        second.Stop();
        return (one, two);
    }

    private static Qso Contact() => new()
    {
        Id = Qso.NewId(),
        TimestampUtc = new DateTime(2026, 9, 3, 12, 34, 56, DateTimeKind.Utc),
        Call = Callsign.Parse("G3XYZ"),
        Frequency = Frequency.FromKilohertz(14_025),
        Mode = Modes.Cw,
        ContestName = "CQWW",
        ContestNumber = 2,
        SentNumber = 41,
        StationName = "RUN-PC",
    };
}