// Go: gateway.go — per-account subscription routing state on outbound gateway connections.
// Gap 11.3: Account-specific gateway routes.
using System.Net;
using System.Net.Sockets;
using NATS.Server.Gateways;
using Shouldly;

namespace NATS.Server.Tests.Gateways;

/// <summary>
/// Unit tests for account-specific subscription tracking on GatewayConnection.
/// Each test constructs a GatewayConnection using a connected socket pair so the
/// constructor succeeds; the subscription tracking methods are pure in-memory operations
/// that do not require the network handshake to have completed.
/// Go reference: gateway.go — account-scoped subscription propagation on outbound routes.
/// </summary>
public class AccountGatewayRoutesTests : IAsyncDisposable
{
    private readonly TcpListener _listener;
    private readonly Socket _clientSocket;
    private readonly Socket _serverSocket;
    private readonly GatewayConnection _conn;

    public AccountGatewayRoutesTests()
    {
        _listener = new TcpListener(IPAddress.Loopback, 0);
        _listener.Start();
        var port = ((IPEndPoint)_listener.LocalEndpoint).Port;

        _clientSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
        _clientSocket.Connect(IPAddress.Loopback, port);
        _serverSocket = _listener.AcceptSocket();

        _conn = new GatewayConnection(_serverSocket);
    }

    public async ValueTask DisposeAsync()
    {
        await _conn.DisposeAsync();
        _clientSocket.Dispose();
        _listener.Stop();
    }

    // Go: gateway.go — AddAccountSubscription records the subject under the account key.
    [Fact]
    public void AddAccountSubscription_adds_subject()
    {
        _conn.AddAccountSubscription("ACCT_A", "orders.created");

        _conn.AccountSubscriptionCount("ACCT_A").ShouldBe(1);
    }

    // Go: gateway.go — GetAccountSubscriptions returns a snapshot of tracked subjects.
    [Fact]
    public void GetAccountSubscriptions_returns_subjects()
    {
        _conn.AddAccountSubscription("ACCT_B", "payments.processed");
        _conn.AddAccountSubscription("ACCT_B", "payments.failed");

        var subs = _conn.GetAccountSubscriptions("ACCT_B");

        subs.ShouldContain("payments.processed");
        subs.ShouldContain("payments.failed");
        subs.Count.ShouldBe(2);
    }

    // Go: gateway.go — RemoveAccountSubscription removes a specific subject.
    [Fact]
    public void RemoveAccountSubscription_removes_subject()
    {
        _conn.AddAccountSubscription("ACCT_C", "foo.bar");
        _conn.AddAccountSubscription("ACCT_C", "foo.baz");

        _conn.RemoveAccountSubscription("ACCT_C", "foo.bar");

        _conn.GetAccountSubscriptions("ACCT_C").ShouldNotContain("foo.bar");
        _conn.GetAccountSubscriptions("ACCT_C").ShouldContain("foo.baz");
    }

    // Go: gateway.go — AccountSubscriptionCount reflects current tracked count.
    [Fact]
    public void AccountSubscriptionCount_tracks_count()
    {
        _conn.AddAccountSubscription("ACCT_D", "s1");
        _conn.AddAccountSubscription("ACCT_D", "s2");
        _conn.AddAccountSubscription("ACCT_D", "s3");
        _conn.RemoveAccountSubscription("ACCT_D", "s2");

        _conn.AccountSubscriptionCount("ACCT_D").ShouldBe(2);
    }

    // Go: gateway.go — each account maintains its own isolated subscription set.
    [Fact]
    public void Different_accounts_tracked_independently()
    {
        _conn.AddAccountSubscription("ACC_X", "shared.subject");
        _conn.AddAccountSubscription("ACC_Y", "other.subject");

        _conn.GetAccountSubscriptions("ACC_X").ShouldContain("shared.subject");
        _conn.GetAccountSubscriptions("ACC_X").ShouldNotContain("other.subject");

        _conn.GetAccountSubscriptions("ACC_Y").ShouldContain("other.subject");
        _conn.GetAccountSubscriptions("ACC_Y").ShouldNotContain("shared.subject");
    }

    // Go: gateway.go — GetAccountSubscriptions returns empty set for a never-seen account.
    [Fact]
    public void GetAccountSubscriptions_returns_empty_for_unknown()
    {
        var subs = _conn.GetAccountSubscriptions("UNKNOWN_ACCOUNT");

        subs.ShouldBeEmpty();
    }

    // Go: gateway.go — duplicate AddAccountSubscription calls are idempotent (set semantics).
    [Fact]
    public void AddAccountSubscription_deduplicates()
    {
        _conn.AddAccountSubscription("ACCT_E", "orders.>");
        _conn.AddAccountSubscription("ACCT_E", "orders.>");
        _conn.AddAccountSubscription("ACCT_E", "orders.>");

        _conn.AccountSubscriptionCount("ACCT_E").ShouldBe(1);
    }

    // Go: gateway.go — removing a subject that was never added is a no-op (no exception).
    [Fact]
    public void RemoveAccountSubscription_no_error_for_unknown()
    {
        // Neither the account nor the subject has ever been added.
        var act = () => _conn.RemoveAccountSubscription("NEVER_ADDED", "some.subject");

        act.ShouldNotThrow();
    }

    // Go: gateway.go — an account can track many subjects simultaneously.
    [Fact]
    public void Multiple_subjects_per_account()
    {
        var subjects = new[] { "a.b", "c.d", "e.f.>", "g.*", "h" };
        foreach (var s in subjects)
            _conn.AddAccountSubscription("ACCT_F", s);

        var result = _conn.GetAccountSubscriptions("ACCT_F");

        result.Count.ShouldBe(subjects.Length);
        foreach (var s in subjects)
            result.ShouldContain(s);
    }

    // Go: gateway.go — AccountSubscriptionCount returns 0 for an account with no entries.
    [Fact]
    public void AccountSubscriptionCount_zero_for_unknown()
    {
        _conn.AccountSubscriptionCount("COMPLETELY_NEW_ACCOUNT").ShouldBe(0);
    }
}