using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.Options;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Configuration.Entities;
using ZB.MOM.WW.OtOpcUa.Configuration.Enums;
using ZB.MOM.WW.OtOpcUa.Core.Authorization;
using ZB.MOM.WW.OtOpcUa.Host.OpcUa;
using ZB.MOM.WW.OtOpcUa.OpcUaServer.Security;

namespace ZB.MOM.WW.OtOpcUa.Host.Tests.OpcUa;

/// <summary>
///     Covers the #520 stage-2 identity cutover: the API-key authenticator and the interim role
///     mapping it feeds the two live authorization gates from.
/// </summary>
public sealed class ApiKeyAuthenticationTests
{
    private const string Pepper = "unit-test-pepper";
    private const string Principal = "scadabridge-dcl";

    // ---------- interim role mapping ----------

    [Fact]
    public void A_cluster_scoped_write_grant_confers_the_write_role()
    {
        var roles = ApiKeyInterimRoleMapper.Map(
            [Grant(NodeAclScopeKind.Cluster, NodePermissions.WriteOperate)], Principal);

        roles.ShouldContain(OpcUaDataPlaneRoles.WriteOperate);
    }

    [Fact]
    public void A_narrower_scoped_write_grant_confers_nothing_yet()
    {
        // THE load-bearing assertion of this stage. Nothing in the pipeline can honour a scope until
        // stage 5, so honouring the FLAG alone would turn "WriteOperate on Equipment X" into
        // server-wide write authority — the operator's narrow intent silently becoming broad. Under-
        // granting is the only safe reading while scope is unenforceable.
        foreach (var narrower in new[]
                 {
                     NodeAclScopeKind.Equipment, NodeAclScopeKind.UnsArea,
                     NodeAclScopeKind.UnsLine, NodeAclScopeKind.Namespace,
                 })
        {
            var roles = ApiKeyInterimRoleMapper.Map(
                [Grant(narrower, NodePermissions.WriteOperate)], Principal);

            roles.ShouldBeEmpty($"a {narrower}-scoped grant must not confer a server-wide role");
        }
    }

    [Fact]
    public void A_grant_for_a_different_principal_is_ignored()
    {
        var other = Grant(NodeAclScopeKind.Cluster, NodePermissions.Admin);
        other.Principal = "someone-else";

        ApiKeyInterimRoleMapper.Map([other], Principal).ShouldBeEmpty();
    }

    [Fact]
    public void Alarm_acknowledge_maps_to_the_alarm_role_and_read_only_maps_to_nothing()
    {
        ApiKeyInterimRoleMapper
            .Map([Grant(NodeAclScopeKind.Cluster, NodePermissions.AlarmAcknowledge)], Principal)
            .ShouldContain(OpcUaDataPlaneRoles.AlarmAck);

        // ReadOnly carries no gated permission — reads are ungated today, so it must confer no role
        // rather than quietly granting one.
        ApiKeyInterimRoleMapper
            .Map([Grant(NodeAclScopeKind.Cluster, NodePermissions.ReadOnly)], Principal)
            .ShouldBeEmpty();
    }

    [Fact]
    public void Flags_union_across_several_cluster_grants()
    {
        var roles = ApiKeyInterimRoleMapper.Map(
        [
            Grant(NodeAclScopeKind.Cluster, NodePermissions.WriteOperate),
            Grant(NodeAclScopeKind.Cluster, NodePermissions.AlarmAcknowledge),
        ], Principal);

        roles.ShouldContain(OpcUaDataPlaneRoles.WriteOperate);
        roles.ShouldContain(OpcUaDataPlaneRoles.AlarmAck);
    }

    [Fact]
    public void Principal_matching_is_case_insensitive_but_not_prefix_based()
    {
        ApiKeyInterimRoleMapper
            .Map([Grant(NodeAclScopeKind.Cluster, NodePermissions.WriteOperate)], Principal.ToUpperInvariant())
            .ShouldContain(OpcUaDataPlaneRoles.WriteOperate);

        // A principal that merely starts with the granted name must not inherit it.
        ApiKeyInterimRoleMapper
            .Map([Grant(NodeAclScopeKind.Cluster, NodePermissions.WriteOperate)], Principal + "-readonly")
            .ShouldBeEmpty();
    }

    // ---------- authenticator ----------

    [Fact]
    public async Task A_valid_key_authenticates_as_its_principal()
    {
        var (presented, store) = SetUp(NodePermissions.WriteOperate, NodeAclScopeKind.Cluster);

        var result = await Auth(store).AuthenticateUserNameAsync("apikey", presented, default);

        result.Success.ShouldBeTrue();
        result.DisplayName.ShouldBe(Principal);
        result.Roles.ShouldContain(OpcUaDataPlaneRoles.WriteOperate);
    }

    [Fact]
    public async Task The_wrong_username_is_denied()
    {
        var (presented, store) = SetUp();
        var result = await Auth(store).AuthenticateUserNameAsync("alice", presented, default);
        result.Success.ShouldBeFalse();
    }

    [Fact]
    public async Task A_wrong_secret_a_missing_key_and_a_malformed_credential_are_all_denied_identically()
    {
        var (presented, store) = SetUp();
        var auth = Auth(store);

        var wrongSecret = await auth.AuthenticateUserNameAsync("apikey", $"otua_{store.KeyId}_wrong", default);
        var noSuchKey = await auth.AuthenticateUserNameAsync("apikey", "otua_ffffffff_whatever", default);
        var malformed = await auth.AuthenticateUserNameAsync("apikey", "not-a-key", default);
        var empty = await auth.AuthenticateUserNameAsync("apikey", "", default);

        foreach (var r in new[] { wrongSecret, noSuchKey, malformed, empty })
        {
            r.Success.ShouldBeFalse();
            // Identical message for every failure mode: the server must not be usable as an oracle for
            // which half of the credential was wrong, or whether a key id exists at all.
            r.Error.ShouldBe(ApiKeyOpcUaUserAuthenticator.DenyMessage);
        }

        // ...and the valid one still works, so the above is not passing because everything is denied.
        (await auth.AuthenticateUserNameAsync("apikey", presented, default)).Success.ShouldBeTrue();
    }

    [Fact]
    public async Task A_store_that_throws_denies_rather_than_propagating()
    {
        // The interface contract forbids throwing — an exception escapes into the SDK session-activation
        // path and surfaces as BadInternalError instead of a clean rejection.
        var store = new ThrowingApiKeyStore();
        var result = await Auth(store).AuthenticateUserNameAsync("apikey", "otua_aabbccdd_secret", default);

        result.Success.ShouldBeFalse();
        result.Error.ShouldBe(ApiKeyOpcUaUserAuthenticator.DenyMessage);
    }

    [Fact]
    public async Task An_unset_pepper_denies_rather_than_authenticating_everything()
    {
        var (presented, store) = SetUp();
        var auth = new ApiKeyOpcUaUserAuthenticator(
            store,
            Options.Create(new ApiKeyOptions { Username = "apikey", Pepper = "" }),
            NullLogger<ApiKeyOpcUaUserAuthenticator>.Instance);

        (await auth.AuthenticateUserNameAsync("apikey", presented, default)).Success.ShouldBeFalse();
    }

    // ---------- anonymous as a normal principal (D3) ----------

    [Fact]
    public async Task Anonymous_resolves_through_the_same_grant_path_as_a_key()
    {
        var (_, store) = SetUp();
        store.PrincipalGrants.Add(new NodeAcl
        {
            NodeAclId = "ACL-anon",
            ClusterId = "MAIN",
            Principal = OpcUaPrincipals.Anonymous,
            ScopeKind = NodeAclScopeKind.Cluster,
            PermissionFlags = NodePermissions.WriteOperate,
        });

        var result = await Auth(store).AuthenticateAnonymousAsync(default);

        result.Success.ShouldBeTrue();
        result.DisplayName.ShouldBe(OpcUaPrincipals.Anonymous);
        // The point of D3: anonymous can be granted WRITE, not merely tolerated as read-only.
        result.Roles.ShouldContain(OpcUaDataPlaneRoles.WriteOperate);
    }

    [Fact]
    public async Task Anonymous_with_no_grants_is_admitted_with_no_roles()
    {
        // Today's behaviour preserved: it connects, and every role-gated operation denies.
        var (_, store) = SetUp();

        var result = await Auth(store).AuthenticateAnonymousAsync(default);

        result.Success.ShouldBeTrue();
        result.Roles.ShouldBeEmpty();
    }

    [Fact]
    public async Task Anonymous_denies_when_grants_cannot_be_read()
    {
        // Deliberately NOT admit-with-no-roles. That is the pre-#520 behaviour, and defaulting to it
        // exactly when we cannot read what anonymous may do stops being harmless once reads are gated.
        var result = await Auth(new ThrowingApiKeyStore()).AuthenticateAnonymousAsync(default);

        result.Success.ShouldBeFalse();
    }

    [Fact]
    public async Task A_key_may_not_authenticate_as_the_reserved_anonymous_principal()
    {
        var (presented, apiKeyId, hash) = ApiKeySecret.Generate(Pepper);
        var key = new ApiKey
        {
            ApiKeyId = apiKeyId,
            Name = "sneaky",
            SecretHash = hash,
            Principal = OpcUaPrincipals.Anonymous,
            Enabled = true,
            CreatedUtc = DateTime.UtcNow,
        };

        var result = await Auth(new FakeApiKeyStore(key, [])).AuthenticateUserNameAsync("apikey", presented, default);

        // Otherwise a credentialled client silently inherits whatever anonymous was granted.
        result.Success.ShouldBeFalse();
    }

    [Fact]
    public async Task The_default_interface_implementation_admits_anonymous_with_no_roles()
    {
        // NullOpcUaUserAuthenticator (driver-only nodes, pre-boot) must keep the pre-#520 behaviour
        // rather than denying anonymous outright, or turning this on would black out those nodes.
        // Interface-typed on purpose: a default interface implementation is only reachable through the
        // interface, which is how OpcUaApplicationHost holds it.
        IOpcUaUserAuthenticator sut = NullOpcUaUserAuthenticator.Instance;
        var result = await sut.AuthenticateAnonymousAsync(default);

        result.Success.ShouldBeTrue();
        result.Roles.ShouldBeEmpty();
    }

    // ---------- helpers ----------

    private static NodeAcl Grant(NodeAclScopeKind scope, NodePermissions flags) => new()
    {
        NodeAclId = $"ACL-{scope}-{flags}",
        ClusterId = "MAIN",
        Principal = Principal,
        ScopeKind = scope,
        ScopeId = scope == NodeAclScopeKind.Cluster ? null : "SOME-SCOPE",
        PermissionFlags = flags,
    };

    private static ApiKeyOpcUaUserAuthenticator Auth(IApiKeyStore store) => new(
        store,
        Options.Create(new ApiKeyOptions { Username = "apikey", Pepper = Pepper }),
        NullLogger<ApiKeyOpcUaUserAuthenticator>.Instance);

    private static (string Presented, FakeApiKeyStore Store) SetUp(
        NodePermissions flags = NodePermissions.None,
        NodeAclScopeKind scope = NodeAclScopeKind.Cluster)
    {
        var (presented, apiKeyId, hash) = ApiKeySecret.Generate(Pepper);
        var key = new ApiKey
        {
            ApiKeyId = apiKeyId,
            Name = "test key",
            SecretHash = hash,
            Principal = Principal,
            Enabled = true,
            CreatedUtc = DateTime.UtcNow,
        };
        var grants = flags == NodePermissions.None ? [] : new List<NodeAcl> { Grant(scope, flags) };
        return (presented, new FakeApiKeyStore(key, grants));
    }

    private sealed class FakeApiKeyStore(ApiKey key, IReadOnlyList<NodeAcl> grants) : IApiKeyStore
    {
        public string KeyId => key.ApiKeyId;

        /// <summary>Grants returned for a bare principal lookup (the anonymous path).</summary>
        public List<NodeAcl> PrincipalGrants { get; } = [];

        public Task<ApiKeyLookup?> FindAsync(string apiKeyId, DateTime utcNow, CancellationToken ct) =>
            Task.FromResult(string.Equals(apiKeyId, key.ApiKeyId, StringComparison.Ordinal)
                ? new ApiKeyLookup(key, grants)
                : null);

        public Task<IReadOnlyList<NodeAcl>> FindGrantsAsync(string principal, CancellationToken ct) =>
            Task.FromResult<IReadOnlyList<NodeAcl>>(
                [.. PrincipalGrants.Where(g => string.Equals(g.Principal, principal, StringComparison.OrdinalIgnoreCase))]);
    }

    private sealed class ThrowingApiKeyStore : IApiKeyStore
    {
        public Task<ApiKeyLookup?> FindAsync(string apiKeyId, DateTime utcNow, CancellationToken ct) =>
            throw new InvalidOperationException("store is down");

        public Task<IReadOnlyList<NodeAcl>> FindGrantsAsync(string principal, CancellationToken ct) =>
            throw new InvalidOperationException("store is down");
    }
}