using System.Security.Claims;
using Microsoft.AspNetCore.Components.Authorization;
using Microsoft.AspNetCore.Http;
using Shouldly;
using Xunit;
using ZB.MOM.WW.Auth.AspNetCore;
using ZB.MOM.WW.OtOpcUa.Security.Audit;

namespace ZB.MOM.WW.OtOpcUa.Security.Tests.Audit;

/// <summary>
///     R03:2.5 — inside a Blazor circuit there is no <c>HttpContext</c> after the first render, so an
///     HTTP-only accessor stamps every audit row from an interactive page <c>"system"</c>. The circuit's
///     <see cref="AuthenticationStateProvider"/> is consulted first; the HTTP context is the fallback.
/// </summary>
public sealed class AuthenticationStateAuditActorAccessorTests
{
    [Fact]
    public void Circuit_principal_wins_when_there_is_no_http_context()
    {
        var accessor = new AuthenticationStateAuditActorAccessor(
            new HttpContextAccessorStub(null),
            new FixedStateProvider(Authenticated(new Claim(ZbClaimTypes.Username, "alice"))));

        accessor.CurrentActor.ShouldBe("alice");
    }

    [Fact]
    public void Http_principal_is_the_fallback_outside_a_circuit()
    {
        var context = new DefaultHttpContext { User = Authenticated(new Claim(ZbClaimTypes.Username, "bob")) };
        var accessor = new AuthenticationStateAuditActorAccessor(new HttpContextAccessorStub(context), authenticationState: null);

        accessor.CurrentActor.ShouldBe("bob");
    }

    [Fact]
    public void Unauthenticated_circuit_falls_through_to_http_then_null()
    {
        var anonymousCircuit = new FixedStateProvider(new ClaimsPrincipal(new ClaimsIdentity()));

        new AuthenticationStateAuditActorAccessor(new HttpContextAccessorStub(null), anonymousCircuit)
            .CurrentActor.ShouldBeNull();

        var context = new DefaultHttpContext { User = Authenticated(new Claim(ZbClaimTypes.Name, "carol")) };
        new AuthenticationStateAuditActorAccessor(new HttpContextAccessorStub(context), anonymousCircuit)
            .CurrentActor.ShouldBe("carol");
    }

    /// <summary>An incomplete state task is "no circuit identity", never a block.</summary>
    [Fact]
    public void Pending_authentication_state_is_not_awaited()
    {
        var accessor = new AuthenticationStateAuditActorAccessor(
            new HttpContextAccessorStub(null),
            new PendingStateProvider());

        accessor.CurrentActor.ShouldBeNull();
    }

    /// <summary>
    ///     Fix round 1 / I5 — the REAL server-side provider, resolved in a non-circuit scope (a minimal-API
    ///     request, a background service), throws <see cref="InvalidOperationException"/> from
    ///     <c>GetAuthenticationStateAsync</c> because nothing called <c>SetAuthenticationState</c>. That used
    ///     to escape <c>CurrentActor</c>; it must fall back to the HTTP principal instead.
    /// </summary>
    [Fact]
    public void Real_server_provider_outside_a_circuit_falls_back_to_the_http_principal()
    {
        var context = new DefaultHttpContext { User = Authenticated(new Claim(ZbClaimTypes.Username, "dave")) };
        var accessor = new AuthenticationStateAuditActorAccessor(
            new HttpContextAccessorStub(context),
            new Microsoft.AspNetCore.Components.Server.ServerAuthenticationStateProvider());

        accessor.CurrentActor.ShouldBe("dave");

        // No HTTP principal either ⇒ null, still no throw.
        new AuthenticationStateAuditActorAccessor(
                new HttpContextAccessorStub(null),
                new Microsoft.AspNetCore.Components.Server.ServerAuthenticationStateProvider())
            .CurrentActor.ShouldBeNull();
    }

    /// <summary>Positive control on the real provider: once a circuit has set its state, that principal wins.</summary>
    [Fact]
    public void Real_server_provider_inside_a_circuit_serves_the_circuit_principal()
    {
        var provider = new Microsoft.AspNetCore.Components.Server.ServerAuthenticationStateProvider();
        provider.SetAuthenticationState(Task.FromResult(
            new AuthenticationState(Authenticated(new Claim(ZbClaimTypes.Username, "erin")))));
        var context = new DefaultHttpContext { User = Authenticated(new Claim(ZbClaimTypes.Username, "http-user")) };

        new AuthenticationStateAuditActorAccessor(new HttpContextAccessorStub(context), provider)
            .CurrentActor.ShouldBe("erin");
    }

    private static ClaimsPrincipal Authenticated(params Claim[] claims) =>
        new(new ClaimsIdentity(claims, "TestScheme", ZbClaimTypes.Name, ZbClaimTypes.Role));

    private sealed class HttpContextAccessorStub(HttpContext? context) : IHttpContextAccessor
    {
        public HttpContext? HttpContext { get; set; } = context;
    }

    private sealed class FixedStateProvider(ClaimsPrincipal user) : AuthenticationStateProvider
    {
        public override Task<AuthenticationState> GetAuthenticationStateAsync() =>
            Task.FromResult(new AuthenticationState(user));
    }

    private sealed class PendingStateProvider : AuthenticationStateProvider
    {
        public override Task<AuthenticationState> GetAuthenticationStateAsync() =>
            new TaskCompletionSource<AuthenticationState>().Task;
    }
}