// Copyright 2019-2025 The NATS Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// Mirrors server/leafnode_test.go (first 14 tests) from the NATS server Go source.
// All tests require a running NATS server with leaf-node support and are
// deferred until the full server runtime is available.

using ZB.MOM.NatsNet.Server.IntegrationTests.Helpers;

namespace ZB.MOM.NatsNet.Server.IntegrationTests.LeafNode;

/// <summary>
/// Integration tests for leaf-node connectivity, authentication, TLS, and
/// loop detection scenarios.
/// Mirrors server/leafnode_test.go.
/// All tests are deferred pending leaf-node server infrastructure.
/// </summary>
[Collection("LeafNodeIntegration")]
[Trait("Category", "Integration")]
public sealed class LeafNodeTests : IntegrationTestBase
{
    /// <summary>
    /// Verifies that when a leaf-node remote URL resolves to multiple IP addresses
    /// the server randomly cycles through them, ensuring all IPs are eventually used.
    /// Mirrors TestLeafNodeRandomIP.
    /// </summary>
    [Fact(Skip = "deferred: requires running NATS server with leaf-node support")]
    public void RandomIP_ShouldSucceed()
    {
        // Go source: DefaultOptions with LeafNode.Remotes pointing to a hostname that
        // resolves to 3 IPs (127.0.0.1/2/3) via a custom DNS resolver.
        // ReconnectInterval = 50ms, dialTimeout = 15ms.
        // Verifies all three IPs appear in debug logs within 3 seconds.
    }

    /// <summary>
    /// Verifies that leaf-node remote URL lists are randomised on startup when
    /// NoRandomize is false, and preserved in order when NoRandomize is true.
    /// Mirrors TestLeafNodeRandomRemotes.
    /// </summary>
    [Fact(Skip = "deferred: requires running NATS server with leaf-node support")]
    public void RandomRemotes_ShouldSucceed()
    {
        // Go source: DefaultOptions with 2 RemoteLeafOpts — rem0 (NoRandomize=true)
        // and rem1 (NoRandomize=false), each with 16 URLs.
        // Asserts rem0 URLs are in original order; rem1 URLs are shuffled.
    }

    /// <summary>
    /// Verifies that a leaf node can connect to a server that requires mutual TLS
    /// (client and server certificates).
    /// Mirrors TestLeafNodeTLSWithCerts.
    /// </summary>
    [Fact(Skip = "deferred: requires running NATS server with leaf-node TLS support")]
    public void TlsWithCerts_ShouldSucceed()
    {
        // Go source: s1 configured with leaf TLS (ca, cert, key) listening.
        // s2 leaf remote specifies client cert and key (tlsauth/* certs).
        // Verifies leaf node establishes TLS-authenticated connection.
    }

    /// <summary>
    /// Verifies that a leaf-node remote that does not provide a certificate to a
    /// server requiring mutual TLS fails to connect.
    /// Mirrors TestLeafNodeTLSRemoteWithNoCerts.
    /// </summary>
    [Fact(Skip = "deferred: requires running NATS server with leaf-node TLS support")]
    public void TlsRemoteWithNoCerts_ShouldSucceed()
    {
        // Go source: s1 requires client cert (verify=true). s2 provides no cert.
        // Verifies that s2 fails to connect and reports TLS error in logs.
    }

    /// <summary>
    /// Verifies that attempting to connect a leaf node with a local account that
    /// does not exist on the server produces a clear error, and that retries are
    /// observed after the account is removed mid-operation.
    /// Mirrors TestLeafNodeAccountNotFound.
    /// </summary>
    [Fact(Skip = "deferred: requires running NATS server with leaf-node support")]
    public void AccountNotFound_ShouldSucceed()
    {
        // Go source:
        // 1. NewServer with LeafNode.Remotes specifying LocalAccount="foo" (missing) → error.
        // 2. Add account "foo", RunServer → leaf connects to sb.
        // 3. Delete account "foo" from sa; restart sb → expect "Unable to lookup account" error log.
        // 4. Verify gcid keeps incrementing (retries happen).
    }

    /// <summary>
    /// Verifies that a leaf node reconnects to an alternate server in the cluster
    /// after the primary server it was connected to shuts down, and that the leaf
    /// node password never appears in debug or trace logs.
    /// Mirrors TestLeafNodeBasicAuthFailover.
    /// </summary>
    [Fact(Skip = "deferred: requires running NATS server cluster with leaf-node support")]
    public void BasicAuthFailover_ShouldSucceed()
    {
        // Go source: 2-server cluster (sb1+sb2) with leafnode auth user=foo/password=pwdfatal.
        // sa configured as leaf remote pointing to sb1 only.
        // sb1 shuts down; sa must reconnect to sb2.
        // All log messages checked to ensure "pwdfatal" never appears.
    }

    /// <summary>
    /// Verifies that the RTT (round-trip time) reported by a leaf-node connection
    /// is non-zero and updated after PING/PONG exchanges.
    /// Mirrors TestLeafNodeRTT.
    /// </summary>
    [Fact(Skip = "deferred: requires running NATS server with leaf-node support")]
    public void Rtt_ShouldSucceed()
    {
        // Go source: PingInterval=15ms on both servers. Leaf connects to sb.
        // After a short wait, checks that sa leaf RTT > 0.
        // Also verifies RTT is reported in CONNZ output.
    }

    /// <summary>
    /// Verifies that configuring both a single-user credential and a Users array
    /// on the leaf-node listener returns a clear error, and that duplicate user
    /// names in the array also produce an error.
    /// Mirrors TestLeafNodeValidateAuthOptions.
    /// </summary>
    [Fact(Skip = "deferred: requires running NATS server with leaf-node support")]
    public void ValidateAuthOptions_ShouldSucceed()
    {
        // Go source: DefaultOptions with both LeafNode.Username and LeafNode.Users set →
        // "can not have a single user/pass and a users array".
        // Then clears Username, adds duplicate "user" → "duplicate user".
        // These are options-validation errors; NewServer must return error before starting.
    }

    /// <summary>
    /// Verifies that single-user leaf-node authorization correctly routes connections
    /// to the configured account, and that connections with the wrong credentials
    /// are rejected.
    /// Mirrors TestLeafNodeBasicAuthSingleton.
    /// </summary>
    [Fact(Skip = "deferred: requires running NATS server with leaf-node support")]
    public void BasicAuthSingleton_ShouldSucceed()
    {
        // Go source: 4 sub-test combinations:
        // 1. No user spec, no creds → fail (no LN connection established).
        // 2. No user spec, creds=user2:user2 → succeeds, bound to ACC2.
        // 3. No user spec, unknown user → fail.
        // 4. user=ln/pass=pwd, creds=ln:pwd → succeeds, bound to ACC1.
        // Verifies pub/sub message routing to correct account.
    }

    /// <summary>
    /// Verifies that a leaf-node server with multiple authorised users can
    /// map different leaf connections to different accounts, and that each
    /// account's messages are isolated from the others.
    /// Mirrors TestLeafNodeBasicAuthMultiple.
    /// </summary>
    [Fact(Skip = "deferred: requires running NATS server with leaf-node support")]
    public void BasicAuthMultiple_ShouldSucceed()
    {
        // Go source: s1 with users ln1→S1ACC1, ln2→S1ACC2, ln3 (no account).
        // s2 with 2 leaf remotes: ln1 bound to S2ACC1, ln2 to S2ACC2.
        // Verifies publish from S2ACC1 is received by S1ACC1 subscribers only,
        // and publish from S2ACC2 reaches only S1ACC2 subscribers.
    }

    /// <summary>
    /// Verifies that a self-loop leaf-node configuration (A→B and B→A) is detected
    /// and reported as an error by both standalone and clustered server combinations.
    /// Mirrors TestLeafNodeLoop.
    /// </summary>
    [Fact(Skip = "deferred: requires running NATS server with leaf-node support")]
    public void Loop_ShouldSucceed()
    {
        // Go source: t.Run("standalone", ...) and t.Run("cluster", ...).
        // Server A on port 1234 pointing to B on 5678; B pointing back to A.
        // Within 5s, one of the loop-detected loggers must fire.
        // After B restarts without the return remote, A must connect successfully.
    }

    /// <summary>
    /// Verifies that a loop formed through a directed acyclic graph (C→A and C→B,
    /// where B→A) is detected: C receives the loop error and establishes zero connections.
    /// Mirrors TestLeafNodeLoopFromDAG.
    /// </summary>
    [Fact(Skip = "deferred: requires running NATS server with leaf-node support")]
    public void LoopFromDAG_ShouldSucceed()
    {
        // Go source: A standalone, B→A, C→A and C→B.
        // Loop detected on C; C has 0 leaf connections.
        // After restarting C with only C→B, A has 1, B has 2, C has 1.
        // Uses CheckHelper.CheckLeafNodeConnectedCount.
    }

    /// <summary>
    /// Verifies that a pending write that is blocking does not prevent the server
    /// from closing a TLS leaf-node connection within a reasonable timeout.
    /// Mirrors TestLeafNodeCloseTLSConnection.
    /// </summary>
    [Fact(Skip = "deferred: requires running NATS server with leaf-node TLS support")]
    public void CloseTlsConnection_ShouldSucceed()
    {
        // Go source: Server with TLSTimeout=100ms. TLS client performs raw TCP
        // dial, TLS handshake, sends CONNECT+PING, verifies leaf is established.
        // Fills the kernel write buffer to create a blocked write, then closes
        // the connection — must complete within 3 seconds without hanging.
    }

    /// <summary>
    /// Verifies that the server name used in TLS SNI is saved and returned
    /// in varz/connz output for a leaf-node connection.
    /// Mirrors TestLeafNodeTLSSaveName.
    /// </summary>
    [Fact(Skip = "deferred: requires running NATS server with leaf-node TLS support")]
    public void TlsSaveName_ShouldSucceed()
    {
        // Go source: Leaf remote with TLSConfig containing ServerName.
        // After connection, checks that the leaf connection's TLS server name
        // is saved and visible in connz (RemoteAddr or TLS info).
    }
}