ANTOOZA-BACKEND/Application/Features/Api/Auth/SocialAuthorizeUrl/Handler.cs

using Application.Abstractions.Authentication;
using Application.Abstractions.Messaging;
using SharedKernel;
using SharedKernel.Results;
using Microsoft.Extensions.Options;

namespace Application.Features.Api.Auth.SocialAuthorizeUrl;

internal sealed class Handler(
    IEnumerable<ISocialAuthProvider> socialProviders,
    IOptions<AppSettings> options
) : IQueryHandler<Query, Result<Response>> {

    private readonly AppSettings.OAuthSection _oauth = options.Value.OAuth;

    public Task<Result<Response>> Handle(Query request, CancellationToken ct)
    {
        var providerName = request.Provider?.Trim().ToLowerInvariant() switch
        {
            "naver" => "Naver",
            "kakao" => "Kakao",
            _ => null
        };

        if (providerName is null)
        {
            return Task.FromResult(Result.Failure<Response>(Error.Problem("Auth.UnsupportedProvider", "지원하지 않는 소셜 로그인입니다.")));
        }

        // 네이버는 스펙상 필수, 카카오도 CSRF 방어 위해 항상 요구 (d5 §③)
        if (string.IsNullOrWhiteSpace(request.State))
        {
            return Task.FromResult(Result.Failure<Response>(Error.Problem("Auth.StateRequired", "state 값이 필요합니다.")));
        }

        var oauthConfig = providerName == "Naver" ? _oauth.Naver : _oauth.Kakao;

        if (string.IsNullOrWhiteSpace(oauthConfig.ClientId))
        {
            return Task.FromResult(Result.Failure<Response>(Error.Problem("Auth.SocialNotConfigured", $"{providerName} 로그인이 설정되지 않았습니다.")));
        }

        var redirectUri = string.IsNullOrWhiteSpace(request.RedirectUri) ? oauthConfig.RedirectUri : request.RedirectUri;

        if (string.IsNullOrWhiteSpace(redirectUri))
        {
            return Task.FromResult(Result.Failure<Response>(Error.Problem("Auth.RedirectUriRequired", "Redirect URI 가 필요합니다.")));
        }

        var provider = socialProviders.FirstOrDefault(c => c.Provider == providerName);

        if (provider is null)
        {
            return Task.FromResult(Result.Failure<Response>(Error.Problem("Auth.UnsupportedProvider", "지원하지 않는 소셜 로그인입니다.")));
        }

        var url = provider.GetAuthorizationUrl(oauthConfig.ClientId, redirectUri, request.State);

        return Task.FromResult(Result.Success(new Response(providerName, url)));
    }
}