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.
    [Fact]
    public async Task WhereAStationIsReachesTheOthers()
    {
        (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.SendBandAsync(Frequency.FromKilohertz(21_025), Modes.Cw, running: true, radioNumber: 1);

        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("CW", seen?.Mode?.Name);
        Assert.True(seen?.IsRunning);
    }

    [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()));
    }

    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,
    };
}