using System.Security.Claims;
using System.Text.Json;
using Akka.Actor;
using Microsoft.AspNetCore.Components.Authorization;
using Microsoft.Extensions.Logging;
using ZB.MOM.WW.ScadaBridge.Commons.Messages.Management;
using ZB.MOM.WW.ScadaBridge.ManagementService;
using ZB.MOM.WW.ScadaBridge.Security;

namespace ZB.MOM.WW.ScadaBridge.CentralUI.Services;

/// <summary>
/// Default <see cref="ITemplateInheritanceQueryService"/> implementation — a thin
/// read-only facade that dispatches the <see cref="GetResolvedTemplateMembersCommand"/>
/// to the central <c>ManagementActor</c> through the in-process
/// <see cref="ManagementActorHolder"/> (the same Ask seam the HTTP <c>/management</c>
/// endpoint uses). The actor walks the full inheritance chain and returns the
/// effective member set + staleness; none of that is re-implemented here. Mirrors
/// <see cref="SchemaLibraryService"/>'s read path.
/// </summary>
public sealed class TemplateInheritanceQueryService : ITemplateInheritanceQueryService
{
    /// <summary>
    /// camelCase + case-insensitive, matching <c>ManagementActor.SerializeResult</c>'s
    /// options. <see cref="ManagementSuccess.JsonData"/> is produced with those settings,
    /// so the deserializer must mirror them to bind every property.
    /// </summary>
    private static readonly JsonSerializerOptions ResultDeserializerOptions = new()
    {
        PropertyNameCaseInsensitive = true,
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
    };

    private static readonly TimeSpan AskTimeout = TimeSpan.FromSeconds(30);

    private readonly ManagementActorHolder _holder;
    private readonly AuthenticationStateProvider _auth;
    private readonly ILogger<TemplateInheritanceQueryService> _logger;

    /// <summary>
    /// Initializes a new instance of the <see cref="TemplateInheritanceQueryService"/>.
    /// </summary>
    /// <param name="holder">Holder for the central <c>ManagementActor</c> reference.</param>
    /// <param name="auth">Authentication state provider used to project the current principal.</param>
    /// <param name="logger">Logger instance.</param>
    public TemplateInheritanceQueryService(
        ManagementActorHolder holder,
        AuthenticationStateProvider auth,
        ILogger<TemplateInheritanceQueryService> logger)
    {
        _holder = holder ?? throw new ArgumentNullException(nameof(holder));
        _auth = auth ?? throw new ArgumentNullException(nameof(auth));
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }

    /// <inheritdoc/>
    public async Task<ResolvedTemplateMembers?> ResolveAsync(
        int templateId, CancellationToken cancellationToken = default)
    {
        var response = await SendAsync(new GetResolvedTemplateMembersCommand(templateId), cancellationToken);
        if (response is ManagementSuccess success)
        {
            return JsonSerializer.Deserialize<ResolvedTemplateMembers>(
                success.JsonData, ResultDeserializerOptions);
        }

        // Read path: log + return null so the editor falls back to its stored-row view.
        _logger.LogWarning(
            "GetResolvedTemplateMembers failed for template {TemplateId}: {Response}",
            templateId, DescribeFailure(response));
        return null;
    }

    /// <summary>
    /// Wraps <paramref name="command"/> in a <see cref="ManagementEnvelope"/> for the
    /// current principal and Asks the <c>ManagementActor</c>. Transport faults (timeout,
    /// actor not yet started) become a synthetic <see cref="ManagementError"/> so the
    /// caller handles one response shape.
    /// </summary>
    private async Task<object> SendAsync(object command, CancellationToken cancellationToken)
    {
        var actor = _holder.ActorRef;
        if (actor is null)
        {
            return new ManagementError(
                string.Empty, "Management service is not ready.", "SERVICE_UNAVAILABLE");
        }

        var user = await BuildAuthenticatedUserAsync();
        var envelope = new ManagementEnvelope(user, command, Guid.NewGuid().ToString("N"));

        try
        {
            return await actor.Ask<object>(envelope, AskTimeout, cancellationToken);
        }
        catch (OperationCanceledException)
        {
            // Caller-initiated cancel (e.g. circuit teardown) — propagate cleanly.
            throw;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "ManagementActor Ask failed for {Command}", command.GetType().Name);
            return new ManagementError(string.Empty, ex.Message, "TRANSPORT_ERROR");
        }
    }

    /// <summary>
    /// Projects the current Blazor <see cref="ClaimsPrincipal"/> to the
    /// <see cref="AuthenticatedUser"/> the actor authorizes against (mirrors the
    /// claim set the HTTP endpoint constructs).
    /// </summary>
    private async Task<AuthenticatedUser> BuildAuthenticatedUserAsync()
    {
        var state = await _auth.GetAuthenticationStateAsync();
        var principal = state.User;

        var username = principal.FindFirst(JwtTokenService.UsernameClaimType)?.Value ?? "unknown";
        var displayName = principal.FindFirst(JwtTokenService.DisplayNameClaimType)?.Value ?? username;
        var roles = principal.FindAll(JwtTokenService.RoleClaimType).Select(c => c.Value).ToArray();
        var permittedSiteIds = principal.FindAll(JwtTokenService.SiteIdClaimType).Select(c => c.Value).ToArray();

        return new AuthenticatedUser(username, displayName, roles, permittedSiteIds);
    }

    /// <summary>Renders a fallback description for an unexpected/failure response.</summary>
    private static string DescribeFailure(object response) => response switch
    {
        ManagementUnauthorized unauthorized => unauthorized.Message,
        ManagementError error => error.Error,
        _ => "Unexpected response from the management service.",
    };
}