using System.Net.Http.Headers;
using System.Net.Http.Json;
using System.Text.Json;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Routing;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using ModeusSchedule.Abstractions;

namespace SfeduSchedule.Plugin.UniVerse;

public sealed class UniVersePlugin : IPlugin
{
    private const string ApiKeyScheme = "ApiKey";

    public string Name => "UniVerse";

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddHttpClient<IUniverseUserLookupService, UniverseUserLookupService>();
    }

    public void MapEndpoints(IEndpointRouteBuilder endpoints)
    {
        endpoints.MapGet("/plugins/universe/subid",
                async (string? fullname, IUniverseUserLookupService lookupService, CancellationToken cancellationToken) =>
                {
                    if (string.IsNullOrWhiteSpace(fullname))
                        return Results.BadRequest("Query parameter 'fullname' is required.");

                    var result = await lookupService.FindSubIdAsync(fullname, cancellationToken);

                    return result.Status switch
                    {
                        UniverseUserLookupStatus.Found => Results.Text(result.SubId, "text/plain"),
                        UniverseUserLookupStatus.NotFound => Results.NotFound(),
                        UniverseUserLookupStatus.UpstreamError => Results.Problem(
                            result.ErrorMessage,
                            statusCode: StatusCodes.Status502BadGateway),
                        _ => Results.Problem(statusCode: StatusCodes.Status500InternalServerError)
                    };
                })
            .RequireAuthorization(policy => policy
                .AddAuthenticationSchemes(ApiKeyScheme)
                .RequireAuthenticatedUser())
            .WithName("UniVerseGetSubId")
            .Produces<string>(StatusCodes.Status200OK, "text/plain")
            .Produces(StatusCodes.Status400BadRequest)
            .Produces(StatusCodes.Status401Unauthorized)
            .Produces(StatusCodes.Status403Forbidden)
            .Produces(StatusCodes.Status404NotFound)
            .ProducesProblem(StatusCodes.Status502BadGateway);
    }
}

public interface IUniverseUserLookupService
{
    Task<UniverseUserLookupResult> FindSubIdAsync(string fullName, CancellationToken cancellationToken = default);
}

public sealed class UniverseUserLookupService(
    HttpClient httpClient,
    IConfiguration configuration,
    ILogger<UniverseUserLookupService> logger) : IUniverseUserLookupService
{
    private const string AccessControlApiPath = "access-control/api";
    private const string UsersQuery = """
                                      query($t:String!){ users(filter:{text:$t}, pager:{activePage:1,pageSize:10}) { items { id name displayName description } } }
                                      """;

    private static readonly JsonSerializerOptions JsonOptions = new(JsonSerializerDefaults.Web);

    public async Task<UniverseUserLookupResult> FindSubIdAsync(
        string fullName,
        CancellationToken cancellationToken = default)
    {
        var token = configuration["TOKEN"];
        if (string.IsNullOrWhiteSpace(token))
            return UniverseUserLookupResult.UpstreamError("Modeus TOKEN is not configured.");

        var modeusUrl = configuration["MODEUS_URL"];
        if (string.IsNullOrWhiteSpace(modeusUrl))
            return UniverseUserLookupResult.UpstreamError("MODEUS_URL is not configured.");

        httpClient.BaseAddress = new Uri(modeusUrl, UriKind.Absolute);

        using var request = new HttpRequestMessage(HttpMethod.Post, AccessControlApiPath);
        request.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
        request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
        request.Content = JsonContent.Create(
            new UniverseUsersGraphQlRequest(
                UsersQuery,
                new UniverseUsersGraphQlVariables(fullName)),
            options: JsonOptions);

        using var response = await httpClient.SendAsync(request, cancellationToken);
        if (!response.IsSuccessStatusCode)
        {
            logger.LogWarning(
                "Modeus access-control/api returned {StatusCode} while searching user by fullName.",
                response.StatusCode);
            return UniverseUserLookupResult.UpstreamError(
                $"Modeus access-control/api returned {(int)response.StatusCode}.");
        }

        UniverseUsersGraphQlResponse? payload;
        try
        {
            await using var contentStream = await response.Content.ReadAsStreamAsync(cancellationToken);
            payload = await JsonSerializer.DeserializeAsync<UniverseUsersGraphQlResponse>(
                contentStream,
                JsonOptions,
                cancellationToken);
        }
        catch (JsonException exception)
        {
            logger.LogWarning(exception, "Unable to deserialize Modeus access-control/api response.");
            return UniverseUserLookupResult.UpstreamError("Modeus access-control/api returned invalid JSON.");
        }

        if (payload?.Errors is { Count: > 0 })
        {
            logger.LogWarning(
                "Modeus access-control/api returned GraphQL errors: {Errors}",
                JsonSerializer.Serialize(payload.Errors, JsonOptions));
            return UniverseUserLookupResult.UpstreamError("Modeus access-control/api returned GraphQL errors.");
        }

        var users = payload?.Data?.Users?.Items;
        if (users is null || users.Count == 0)
            return UniverseUserLookupResult.NotFound();

        var subId = users[0].Name;
        return string.IsNullOrWhiteSpace(subId)
            ? UniverseUserLookupResult.NotFound()
            : UniverseUserLookupResult.Found(subId);
    }
}

public enum UniverseUserLookupStatus
{
    Found,
    NotFound,
    UpstreamError
}