using System.Net;
using System.Net.Sockets;
using System.Net.WebSockets;
using System.Text;
using DodoSSH.Client.Session;
using DodoSSH.Client.Shell.ViewModels;
using DodoSSH.Client.Ssh;

namespace DodoSSH.Client.App.Tests;

/// <summary>
/// A host reached through Spelunk, from the editor and from a link to the request that reaches SSH.
/// </summary>
/// <remarks>
/// <para>
/// The tunnel is stood in for at <see cref="ISpelunkTunnel"/>, and what it hands back is a real
/// <see cref="SpelunkTunnelRoute"/> over the relay's real bridge and an in-process WebSocket pair — so the
/// proxy SSH is given, and the close code a failed connect is explained by, are the real ones. The tunnel's
/// own HTTP and WebSocket half is <c>SpelunkTunnelTests</c>' job.
/// </para>
/// <para>
/// What these hold is what the tick box and the link promise: a Spelunk host is never dialled directly and
/// never probed, a refusal is said in Spelunk's terms, the key goes only where the host says, and a link
/// never connects anything the user has not saved.
/// </para>
/// </remarks>
public sealed partial class ShellFlowTests
{
    private const string SpelunkApi = "https://api.spelunk.example.com";

    private const string SpelunkApiKey = "spelunk_0123456789abcdefghijklmnopqrstuvwxyzABCDEFG";

    private static readonly Guid SpelunkServer = Guid.Parse("0192f0c8-bbbb-7c3d-8e4f-5a6b7c8d9e0b");

    private readonly FakeSpelunkTunnel spelunkTunnels = new();

    [Fact]
    public async Task ASpelunkHost_IsDialledThroughTheTunnel_AndStillAsItself()
    {
        var vault = await ReadyToConnectThroughSpelunkAsync();

        await using var renderer = await FakeRenderer.AttachAsync(workspace, Token);
        await vault.ConnectCommand.ExecuteAsync(null);

        // The key from the credential, to the Spelunk and server the host names, for the host's own port.
        var opened = spelunkTunnels.Opened.ShouldHaveSingleItem();
        opened.ShouldBe((SpelunkApi, SpelunkServer, SpelunkApiKey, 22));

        // Through the loopback proxy, and named as the host, because the name is what its key is pinned under.
        var request = ssh.Requests.ShouldHaveSingleItem();
        request.Proxy.ShouldNotBeNull().Lifetime.ShouldBeOfType<RelayBridge>();
        request.Host.ShouldBe("203.0.113.10");

        shell.IsTerminalShowing.ShouldBeTrue();

        await request.Proxy.Lifetime.DisposeAsync();
    }

    [Fact]
    public async Task ARefusedTunnel_IsExplained_AndNothingIsDialledOrProbed()
    {
        spelunkTunnels.Refusal = new SpelunkTunnelException(
            "The Spelunk agent on this server is not connected, so Spelunk cannot reach it.");

        var vault = await ReadyToConnectThroughSpelunkAsync();

        await using var renderer = await FakeRenderer.AttachAsync(workspace, Token);
        await vault.ConnectCommand.ExecuteAsync(null);

        // No fallback to the address. For a Spelunk host it may be nothing that answers at all.
        ssh.Requests.ShouldBeEmpty();
        reachability.Probed.ShouldBeEmpty();
        vault.Status.ShouldNotBeNull().ShouldContain("agent on this server is not connected");
    }

    [Fact]
    public async Task ATunnelWhoseAgentCouldNotReachThePort_SaysSo_InsteadOfTheTransportError()
    {
        // What Spelunk does when the agent's own connect to 127.0.0.1:22 fails: accept, then close with 4502.
        spelunkTunnels.CloseWith = (4502, "dial tcp 127.0.0.1:22: connection refused");

        ssh.BeforeConnect = request => ThroughSocksToTheEndAsync(request.Proxy.ShouldNotBeNull().Port);
        ssh.Failure = new InvalidOperationException("An established connection was aborted by the server.");

        var vault = await ReadyToConnectThroughSpelunkAsync();

        await using var renderer = await FakeRenderer.AttachAsync(workspace, Token);
        await vault.ConnectCommand.ExecuteAsync(null);

        vault.Status.ShouldNotBeNull().ShouldContain("could not connect to port 22 on the server itself");
        vault.Status.ShouldNotContain("aborted");
        reachability.Probed.ShouldBeEmpty();
    }

    [Fact]
    public async Task ASpelunkHostsFileTransfer_GoesThroughTheTunnelToo()
    {
        var vault = await ReadyToConnectThroughSpelunkAsync();

        shell.Transfers.Attach(vault, knownHosts);
        shell.Transfers.SelectedHost = shell.Transfers.Hosts[0];

        await shell.Transfers.ConnectCommand.ExecuteAsync(null);

        spelunkTunnels.Opened.ShouldHaveSingleItem();
        var request = ssh.SftpRequests.ShouldHaveSingleItem();
        request.Proxy.ShouldNotBeNull().Lifetime.ShouldBeOfType<RelayBridge>();

        await request.Proxy.Lifetime.DisposeAsync();
    }

    [Fact]
    public async Task TheRelayAndSpelunk_AreOneChoice_InTheEditor()
    {
        await UnlockedAsync();
        var vault = shell.Vault!;

        vault.NewHostCommand.Execute(null);

        vault.EditorRelayEnabled = true;
        vault.EditorThroughSpelunk = true;
        vault.EditorRelayEnabled.ShouldBeFalse("ticking Spelunk unticks the relay");

        vault.EditorRelayEnabled = true;
        vault.EditorThroughSpelunk.ShouldBeFalse("and the other way round");
    }

    [Fact]
    public async Task ASpelunkHostWithNoKeyChosen_IsNotSaved()
    {
        await UnlockedAsync();
        var vault = shell.Vault!;

        vault.NewHostCommand.Execute(null);
        vault.EditorLabel = "web-01";
        vault.EditorHostname = "203.0.113.10";
        vault.EditorUsername = "deploy";
        vault.EditorThroughSpelunk = true;
        vault.EditorSpelunkApi = SpelunkApi;
        vault.EditorSpelunkServerId = SpelunkServer.ToString();

        await vault.SaveHostCommand.ExecuteAsync(null);

        vault.Status.ShouldNotBeNull().ShouldContain("Spelunk API key");
        vault.Hosts.ShouldBeEmpty();
    }

    [Fact]
    public async Task ASavedSpelunkHost_OpensInTheEditorWithItsRoute()
    {
        var vault = await ReadyToConnectThroughSpelunkAsync();

        vault.EditSelectedHostCommand.Execute(null);

        vault.EditorThroughSpelunk.ShouldBeTrue();
        vault.EditorSpelunkApi.ShouldBe(SpelunkApi);
        vault.EditorSpelunkServerId.ShouldBe(SpelunkServer.ToString());
        vault.EditorSelectedSpelunkKey.ShouldNotBeNull().Label.ShouldBe("spelunk key");
    }

    [Fact]
    public async Task ACredentialHoldingASpelunkKey_IsInUse_WhereverThatIsDrawn()
    {
        // So deleting it is warned about like any other credential a host needs, rather than looking unused.
        var vault = await ReadyToConnectThroughSpelunkAsync();

        vault.ShowSectionCommand.Execute(VaultSection.All);
        var row = vault.VaultItems.Single(item => string.Equals(item.Name, "spelunk key", StringComparison.Ordinal));

        row.UsedBySummary.ShouldBe("web-01");

        vault.SelectedVaultItem = row;
        vault.SelectedItemUsedByHosts.ShouldHaveSingleItem().Label.ShouldBe("web-01");
    }

    // ---- A link from Spelunk ----

    [Fact]
    public async Task ALinkForAServerWithNoHost_OpensTheEditor_AndConnectsNothing()
    {
        await UnlockedAsync();
        var vault = shell.Vault!;

        shell.OpenLink(Link(host: "203.0.113.10"));

        vault.IsEditing.ShouldBeTrue();
        vault.EditorLabel.ShouldBe("web 01");
        vault.EditorHostname.ShouldBe("203.0.113.10");
        vault.EditorPort.ShouldBe(22);
        vault.EditorThroughSpelunk.ShouldBeTrue();
        vault.EditorSpelunkApi.ShouldBe(SpelunkApi);
        vault.EditorSpelunkServerId.ShouldBe(SpelunkServer.ToString());

        // No key chosen for a Spelunk no host already uses: the link named the address, and guessing a key
        // for it would be offering to send the key wherever a link says.
        vault.EditorSelectedSpelunkKey.ShouldBeNull();

        spelunkTunnels.Opened.ShouldBeEmpty();
        ssh.Requests.ShouldBeEmpty();
        vault.Hosts.ShouldBeEmpty("nothing is saved until the user saves it");
    }

    [Fact]
    public async Task ALinkWithNoAddress_NamesTheHostAfterTheServer()
    {
        await UnlockedAsync();

        shell.OpenLink(Link(host: null));

        shell.Vault!.EditorHostname.ShouldBe($"spelunk-{SpelunkServer}");
    }

    [Fact]
    public async Task ALinkForASecondServerOnAKnownSpelunk_PicksTheKeyThatSpelunkAlreadyGets()
    {
        var vault = await ReadyToConnectThroughSpelunkAsync();

        shell.OpenLink(Link(server: Guid.Parse("0192f0c8-cccc-7c3d-8e4f-5a6b7c8d9e0c")));

        vault.IsEditing.ShouldBeTrue();
        vault.EditorSelectedSpelunkKey.ShouldNotBeNull().Label.ShouldBe("spelunk key");
    }

    [Fact]
    public async Task ALinkForASavedHost_ConnectsToIt()
    {
        var vault = await ReadyToConnectThroughSpelunkAsync();

        await using var renderer = await FakeRenderer.AttachAsync(workspace, Token);
        await vault.OpenSpelunkLinkAsync(Link(host: "198.51.100.7"));

        vault.IsEditing.ShouldBeFalse();
        spelunkTunnels.Opened.ShouldHaveSingleItem();

        // The saved host, as saved — not the address the link happened to carry.
        var request = ssh.Requests.ShouldHaveSingleItem();
        request.Host.ShouldBe("203.0.113.10");

        await request.Proxy.ShouldNotBeNull().Lifetime.DisposeAsync();
    }

    [Fact]
    public async Task ALinkWhileLocked_WaitsForTheUnlock()
    {
        await EnrolledAndConfirmedAsync();

        shell.OpenLink(Link(host: "203.0.113.10"));

        shell.Vault.ShouldBeNull();
        shell.StatusMessage.ShouldContain("Unlock to open web 01");

        shell.Passphrase = Passphrase;
        await shell.UnlockCommand.ExecuteAsync(null);

        var vault = shell.Vault.ShouldNotBeNull();
        vault.IsEditing.ShouldBeTrue();
        vault.EditorSpelunkServerId.ShouldBe(SpelunkServer.ToString());
    }

    [Fact]
    public async Task ALink_LeavesAHalfEditedHostAlone()
    {
        await UnlockedAsync();
        var vault = shell.Vault!;

        vault.NewHostCommand.Execute(null);
        vault.EditorLabel = "something I was typing";

        shell.OpenLink(Link(host: "203.0.113.10"));

        vault.EditorLabel.ShouldBe("something I was typing");
        vault.EditorThroughSpelunk.ShouldBeFalse();
        vault.Status.ShouldNotBeNull().ShouldContain("Finish or cancel");
    }

    /// <summary>A saved host through Spelunk, bound to a stored SSH password, with its key in the keychain.</summary>
    private async Task<VaultViewModel> ReadyToConnectThroughSpelunkAsync()
    {
        await UnlockedAsync();

        var vault = shell.Vault!;

        await AddCredentialAsync(vault, "spelunk key", password: SpelunkApiKey);
        await AddCredentialAsync(vault, "deploy password", password: "s3cret", username: "deploy");

        vault.NewHostCommand.Execute(null);
        vault.EditorLabel = "web-01";
        vault.EditorHostname = "203.0.113.10";
        vault.EditorUsername = "deploy";
        vault.EditorThroughSpelunk = true;
        vault.EditorSpelunkApi = SpelunkApi + "/";
        vault.EditorSpelunkServerId = SpelunkServer.ToString();
        vault.EditorSelectedSpelunkKey = vault.EditorSpelunkKeyChoices.Single(choice => choice.Label == "spelunk key");
        vault.EditorSelectedAuthentication = vault.EditorAuthenticationChoices
            .Single(choice => choice.Label == "deploy password");

        await vault.SaveHostCommand.ExecuteAsync(null);

        vault.SelectedHost = vault.Hosts.Single(row => row.Host.Spelunk is not null);

        // Saved in the one form, whatever was typed — which is what lets a link find it.
        vault.SelectedHost.Host.Spelunk!.ApiBase.ShouldBe(SpelunkApi);

        return vault;
    }

    private static SpelunkLink Link(string? host = "203.0.113.10", Guid? server = null) =>
        new(SpelunkApi, server ?? SpelunkServer, "web 01", host);

    /// <summary>
    /// Speaks SOCKS5 to the bridge as SSH.NET would, then reads until the bridge closes the stream — which it
    /// does once the tunnel has closed, so its reason is recorded by the time this returns.
    /// </summary>
    private static async Task ThroughSocksToTheEndAsync(int port)
    {
        using var client = new TcpClient();
        await client.ConnectAsync(IPAddress.Loopback, port, Token);

        var stream = client.GetStream();
        var name = Encoding.ASCII.GetBytes("203.0.113.10");

        await stream.WriteAsync(new byte[] { 5, 1, 0 }, Token);
        await stream.ReadExactlyAsync(new byte[2], Token);

        await stream.WriteAsync((byte[])[5, 1, 0, 3, (byte)name.Length, .. name, 0, 22], Token);
        await stream.ReadExactlyAsync(new byte[10], Token);

        var rest = new byte[256];
        while (await stream.ReadAsync(rest, Token) > 0)
        {
        }
    }

    /// <summary>
    /// Spelunk as far as the shell can see it: a route over a real bridge, or a refusal, as a test arranges.
    /// </summary>
    private sealed class FakeSpelunkTunnel : ISpelunkTunnel
    {
        internal List<(string ApiBase, Guid ServerId, string ApiKey, int Port)> Opened { get; } = [];

        internal SpelunkTunnelException? Refusal { get; set; }

        /// <summary>A close Spelunk sends as soon as the tunnel is open, or null to leave it open.</summary>
        internal (int Code, string Reason)? CloseWith { get; set; }

        public async Task<SpelunkTunnelRoute> OpenAsync(
            string apiBase,
            Guid serverId,
            string apiKey,
            int port,
            CancellationToken cancellationToken)
        {
            Opened.Add((apiBase, serverId, apiKey, port));

            if (Refusal is { } refusal)
            {
                throw refusal;
            }

            var (client, far) = await PairAsync(cancellationToken);

            if (CloseWith is { } close)
            {
                await far.CloseOutputAsync((WebSocketCloseStatus)close.Code, close.Reason, cancellationToken);
            }

            return new SpelunkTunnelRoute(RelayBridge.Start(client), port);
        }

        private static async Task<(WebSocket Client, WebSocket Far)> PairAsync(CancellationToken cancellationToken)
        {
            using var listener = new TcpListener(IPAddress.Loopback, 0);
            listener.Start();

            var dialling = new TcpClient();
            var connecting = dialling.ConnectAsync((IPEndPoint)listener.LocalEndpoint, cancellationToken);
            var accepted = await listener.AcceptTcpClientAsync(cancellationToken);
            await connecting;

            return (
                WebSocket.CreateFromStream(
                    dialling.GetStream(),
                    new WebSocketCreationOptions { IsServer = false, KeepAliveInterval = TimeSpan.Zero }),
                WebSocket.CreateFromStream(
                    accepted.GetStream(),
                    new WebSocketCreationOptions { IsServer = true, KeepAliveInterval = TimeSpan.Zero }));
        }
    }
}