Umbraco-CMS/src/Umbraco.Web.BackOffice/Controllers/LanguageController.cs

using System.Globalization;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Options;
using Umbraco.Cms.Core.Configuration.Models;
using Umbraco.Cms.Core.Mapping;
using Umbraco.Cms.Core.Models;
using Umbraco.Cms.Core.Services;
using Umbraco.Cms.Web.Common.Attributes;
using Umbraco.Cms.Web.Common.Authorization;
using Umbraco.Extensions;
using Constants = Umbraco.Cms.Core.Constants;
using Language = Umbraco.Cms.Core.Models.ContentEditing.Language;

namespace Umbraco.Cms.Web.BackOffice.Controllers
{
    /// <summary>
    /// Backoffice controller supporting the dashboard for language administration.
    /// </summary>
    [PluginController(Constants.Web.Mvc.BackOfficeApiArea)]
    public class LanguageController : UmbracoAuthorizedJsonController
    {
        private readonly ILocalizationService _localizationService;
        private readonly IUmbracoMapper _umbracoMapper;

        [ActivatorUtilitiesConstructor]
        public LanguageController(ILocalizationService localizationService, IUmbracoMapper umbracoMapper)
        {
            _localizationService = localizationService ?? throw new ArgumentNullException(nameof(localizationService));
            _umbracoMapper = umbracoMapper ?? throw new ArgumentNullException(nameof(umbracoMapper));
        }

        [Obsolete("Use the constructor without global settings instead, scheduled for removal in V11.")]
        public LanguageController(ILocalizationService localizationService, IUmbracoMapper umbracoMapper, IOptionsSnapshot<GlobalSettings> globalSettings)
            : this(localizationService, umbracoMapper)
        { }

        /// <summary>
        /// Returns all cultures available for creating languages.
        /// </summary>
        /// <returns></returns>
        [HttpGet]
        public IDictionary<string, string> GetAllCultures()
            => CultureInfo.GetCultures(CultureTypes.AllCultures).DistinctBy(x => x.Name).OrderBy(x => x.EnglishName).ToDictionary(x => x.Name, x => x.EnglishName);

        /// <summary>
        /// Returns all currently configured languages.
        /// </summary>
        /// <returns></returns>
        [HttpGet]
        public IEnumerable<Language>? GetAllLanguages()
        {
            var allLanguages = _localizationService.GetAllLanguages();

            return _umbracoMapper.Map<IEnumerable<ILanguage>, IEnumerable<Language>>(allLanguages);
        }

        [HttpGet]
        public ActionResult<Language?> GetLanguage(int id)
        {
            var lang = _localizationService.GetLanguageById(id);
            if (lang == null)
            {
                return NotFound();
            }

            return _umbracoMapper.Map<Language>(lang);
        }

        /// <summary>
        /// Deletes a language with a given ID
        /// </summary>
        [Authorize(Policy = AuthorizationPolicies.TreeAccessLanguages)]
        [HttpDelete]
        [HttpPost]
        public IActionResult DeleteLanguage(int id)
        {
            var language = _localizationService.GetLanguageById(id);
            if (language == null)
            {
                return NotFound();
            }

            // the service would not let us do it, but test here nevertheless
            if (language.IsDefault)
            {
                var message = $"Language '{language.IsoCode}' is currently set to 'default' and can not be deleted.";
                return ValidationProblem(message);
            }

            // service is happy deleting a language that's fallback for another language,
            // will just remove it - so no need to check here
            _localizationService.Delete(language);

            return Ok();
        }

        /// <summary>
        /// Creates or saves a language
        /// </summary>
        [Authorize(Policy = AuthorizationPolicies.TreeAccessLanguages)]
        [HttpPost]
        public ActionResult<Language?> SaveLanguage(Language language)
        {
            if (!ModelState.IsValid)
            {
                return ValidationProblem(ModelState);
            }

            // this is prone to race conditions but the service will not let us proceed anyways
            var existingByCulture = _localizationService.GetLanguageByIsoCode(language.IsoCode);

            // the localization service might return the generic language even when queried for specific ones (e.g. "da" when queried for "da-DK")
            // - we need to handle that explicitly
            if (existingByCulture?.IsoCode != language.IsoCode)
            {
                existingByCulture = null;
            }

            if (existingByCulture != null && language.Id != existingByCulture.Id)
            {
                // Someone is trying to create a language that already exist
                ModelState.AddModelError("IsoCode", "The language " + language.IsoCode + " already exists");
                return ValidationProblem(ModelState);
            }

            var existingById = language.Id != default ? _localizationService.GetLanguageById(language.Id) : null;
            if (existingById == null)
            {
                // Creating a new lang...
                CultureInfo culture;
                try
                {
                    culture = CultureInfo.GetCultureInfo(language.IsoCode!);
                }
                catch (CultureNotFoundException)
                {
                    ModelState.AddModelError("IsoCode", "No Culture found with name " + language.IsoCode);
                    return ValidationProblem(ModelState);
                }

                // create it (creating a new language cannot create a fallback cycle)
                var newLang = new Core.Models.Language(culture.Name, language.Name ?? culture.EnglishName)
                {
                    IsDefault = language.IsDefault,
                    IsMandatory = language.IsMandatory,
                    FallbackLanguageId = language.FallbackLanguageId
                };

                _localizationService.Save(newLang);
                return _umbracoMapper.Map<Language>(newLang);
            }

            existingById.IsoCode = language.IsoCode;
            if (!string.IsNullOrEmpty(language.Name))
            {
                existingById.CultureName = language.Name;
            }

            // note that the service will prevent the default language from being "un-defaulted"
            // but does not hurt to test here - though the UI should prevent it too
            if (existingById.IsDefault && !language.IsDefault)
            {
                ModelState.AddModelError("IsDefault", "Cannot un-default the default language.");
                return ValidationProblem(ModelState);
            }

            existingById.IsDefault = language.IsDefault;
            existingById.IsMandatory = language.IsMandatory;
            existingById.FallbackLanguageId = language.FallbackLanguageId;

            // modifying an existing language can create a fallback, verify
            // note that the service will check again, dealing with race conditions
            if (existingById.FallbackLanguageId.HasValue)
            {
                var languages = _localizationService.GetAllLanguages().ToDictionary(x => x.Id, x => x);
                if (!languages.ContainsKey(existingById.FallbackLanguageId.Value))
                {
                    ModelState.AddModelError("FallbackLanguage", "The selected fall back language does not exist.");
                    return ValidationProblem(ModelState);
                }

                if (CreatesCycle(existingById, languages))
                {
                    ModelState.AddModelError("FallbackLanguage", $"The selected fall back language {languages[existingById.FallbackLanguageId.Value].IsoCode} would create a circular path.");
                    return ValidationProblem(ModelState);
                }
            }

            _localizationService.Save(existingById);
            return _umbracoMapper.Map<Language>(existingById);
        }

        // see LocalizationService
        private bool CreatesCycle(ILanguage language, IDictionary<int, ILanguage> languages)
        {
            // a new language is not referenced yet, so cannot be part of a cycle
            if (!language.HasIdentity)
            {
                return false;
            }

            var id = language.FallbackLanguageId;
            while (true) // assuming languages does not already contains a cycle, this must end
            {
                if (!id.HasValue)
                {
                    return false; // no fallback means no cycle
                }

                if (id.Value == language.Id)
                {
                    return true; // back to language = cycle!
                }

                id = languages[id.Value].FallbackLanguageId; // else keep chaining
            }
        }
    }
}