EnvelopeGenerator/EnvelopeGenerator.ReceiverUI/Services/CultureService.cs

using System.Globalization;
using Microsoft.JSInterop;

namespace EnvelopeGenerator.ReceiverUI.Services;

/// <summary>
/// Service for managing application culture/localization.
/// </summary>
public class CultureService
{
    private readonly IJSRuntime _jsRuntime;
    private const string CULTURE_KEY = "AppCulture";

    public CultureService(IJSRuntime jsRuntime)
    {
        _jsRuntime = jsRuntime;
    }

    /// <summary>
    /// Gets the list of supported cultures.
    /// </summary>
    public static CultureInfo[] SupportedCultures { get; } = new[]
    {
        new CultureInfo("de-DE"),
        new CultureInfo("en-US"),
        new CultureInfo("fr-FR")
    };

    /// <summary>
    /// Sets the application culture and stores it in localStorage.
    /// </summary>
    public async Task SetCultureAsync(string culture)
    {
        if (!SupportedCultures.Any(c => c.Name == culture))
            throw new ArgumentException($"Culture '{culture}' is not supported.", nameof(culture));

        await _jsRuntime.InvokeVoidAsync("localStorage.setItem", CULTURE_KEY, culture);
    }

    /// <summary>
    /// Gets the stored culture from localStorage.
    /// </summary>
    public async Task<string?> GetCultureAsync()
    {
        try
        {
            return await _jsRuntime.InvokeAsync<string?>("localStorage.getItem", CULTURE_KEY);
        }
        catch
        {
            return null;
        }
    }

    /// <summary>
    /// Initializes the culture from localStorage or browser settings.
    /// </summary>
    public async Task<CultureInfo> InitializeCultureAsync()
    {
        var storedCulture = await GetCultureAsync();
        
        if (!string.IsNullOrEmpty(storedCulture) && 
            SupportedCultures.Any(c => c.Name == storedCulture))
        {
            return new CultureInfo(storedCulture);
        }

        // Fallback to browser culture or default
        var browserCulture = CultureInfo.CurrentCulture.Name;
        var matchedCulture = SupportedCultures.FirstOrDefault(c => c.Name == browserCulture);
        
        return matchedCulture ?? SupportedCultures[0]; // Default to German
    }
}