LMEMappeCatastaliApp/Services/AppLocalizationService.cs

using System.Globalization;

namespace LMEMappeCatastaliApp.Services;

public sealed class AppLocalizationService
{
    public const string LanguagePreferenceKey = "app_language";
    public const string MeasurementPreferenceKey = "measurement_system";

    private static readonly HashSet<string> SupportedLanguages = new(StringComparer.OrdinalIgnoreCase)
    {
        "auto",
        "it",
        "en"
    };

    private static readonly HashSet<string> SupportedMeasurementSystems = new(StringComparer.OrdinalIgnoreCase)
    {
        "auto",
        "metric",
        "imperial"
    };

    private static readonly Dictionary<string, Dictionary<string, string>> Strings = new(StringComparer.OrdinalIgnoreCase)
    {
        ["it"] = new(StringComparer.Ordinal)
        {
            ["settings.localization.title"] = "Lingua e misure",
            ["settings.language"] = "Lingua",
            ["settings.language.auto"] = "Automatica",
            ["settings.language.it"] = "Italiano",
            ["settings.language.en"] = "English",
            ["settings.measurements"] = "Sistema di misura",
            ["settings.measurements.auto"] = "Automatico in base all'area",
            ["settings.measurements.metric"] = "Metrico",
            ["settings.measurements.imperial"] = "Imperiale",
            ["settings.pro.title"] = "Abbonamento Pro",
            ["settings.pro.status"] = "Stato",
            ["settings.pro.active"] = "Pro attivo",
            ["settings.pro.base"] = "Base gratuita",
            ["settings.pro.offline"] = "Offline: le funzioni Pro restano disponibili durante il periodo di tolleranza senza cancellare i dati.",
            ["settings.pro.restore"] = "Ripristina acquisti",
            ["settings.pro.manage"] = "Gestisci abbonamento",
            ["settings.pro.monthly"] = "Pro mensile",
            ["settings.pro.yearly"] = "Pro annuale",
            ["settings.pro.note"] = "Il prodotto LME Pro si configura nella Play Console con piano mensile e annuale.",
            ["settings.pro.manual.code"] = "Codice licenza manuale",
            ["settings.pro.manual.help"] = "Incolla il codice cifrato ricevuto. Nome, email e scadenza vengono letti solo dopo la verifica crittografica.",
            ["settings.pro.manual.activate"] = "Attiva codice",
            ["settings.pro.manual.remove"] = "Rimuovi licenza",
            ["settings.pro.manual.expires"] = "Scadenza",
            ["settings.pro.manual.valid"] = "Licenza manuale valida",
            ["settings.pro.manual.expired"] = "Licenza manuale scaduta: funzionalita Base attive",
            ["settings.pro.manual.activated"] = "Licenza manuale attivata.",
            ["settings.pro.manual.invalid"] = "Codice licenza non valido.",
            ["settings.pro.manual.removed"] = "Licenza manuale rimossa.",
            ["menu.quickHelp"] = "Guida rapida",
            ["menu.map"] = "Mappa",
            ["menu.search"] = "Cerca localita",
            ["menu.cadastre"] = "Ricerca catastale",
            ["menu.data"] = "Dati e disegni",
            ["menu.projects"] = "Progetti",
            ["menu.export"] = "Esporta",
            ["menu.tools"] = "Strumenti avanzati",
            ["menu.settings"] = "Impostazioni",
            ["panel.settings.title"] = "Impostazioni",
            ["panel.settings.eyebrow"] = "Mappa, GPS, Pro e servizi ufficiali",
            ["measure.area"] = "Misura area",
            ["measure.distance"] = "Misura distanza",
            ["measure.circle"] = "Misura cerchio",
            ["measure.rectangle"] = "Disegna rettangolo",
            ["measure.poi"] = "Aggiungi POI"
        },
        ["en"] = new(StringComparer.Ordinal)
        {
            ["settings.localization.title"] = "Language and units",
            ["settings.language"] = "Language",
            ["settings.language.auto"] = "Automatic",
            ["settings.language.it"] = "Italiano",
            ["settings.language.en"] = "English",
            ["settings.measurements"] = "Measurement system",
            ["settings.measurements.auto"] = "Automatic by region",
            ["settings.measurements.metric"] = "Metric",
            ["settings.measurements.imperial"] = "Imperial",
            ["settings.pro.title"] = "Pro subscription",
            ["settings.pro.status"] = "Status",
            ["settings.pro.active"] = "Pro active",
            ["settings.pro.base"] = "Free base plan",
            ["settings.pro.offline"] = "Offline: Pro features remain available during the grace period without deleting user data.",
            ["settings.pro.restore"] = "Restore purchases",
            ["settings.pro.manage"] = "Manage subscription",
            ["settings.pro.monthly"] = "Monthly Pro",
            ["settings.pro.yearly"] = "Yearly Pro",
            ["settings.pro.note"] = "Create the LME Pro product in Play Console with monthly and yearly base plans.",
            ["settings.pro.manual.code"] = "Manual license code",
            ["settings.pro.manual.help"] = "Paste the encrypted code you received. Name, email and expiry are read only after cryptographic verification.",
            ["settings.pro.manual.activate"] = "Activate code",
            ["settings.pro.manual.remove"] = "Remove license",
            ["settings.pro.manual.expires"] = "Expires",
            ["settings.pro.manual.valid"] = "Manual license valid",
            ["settings.pro.manual.expired"] = "Manual license expired: Base features active",
            ["settings.pro.manual.activated"] = "Manual license activated.",
            ["settings.pro.manual.invalid"] = "Invalid license code.",
            ["settings.pro.manual.removed"] = "Manual license removed.",
            ["menu.quickHelp"] = "Quick help",
            ["menu.map"] = "Map",
            ["menu.search"] = "Search place",
            ["menu.cadastre"] = "Cadastral search",
            ["menu.data"] = "Data and drawings",
            ["menu.projects"] = "Projects",
            ["menu.export"] = "Export",
            ["menu.tools"] = "Advanced tools",
            ["menu.settings"] = "Settings",
            ["panel.settings.title"] = "Settings",
            ["panel.settings.eyebrow"] = "Map, GPS, Pro and official services",
            ["measure.area"] = "Measure area",
            ["measure.distance"] = "Measure distance",
            ["measure.circle"] = "Measure circle",
            ["measure.rectangle"] = "Draw rectangle",
            ["measure.poi"] = "Add POI"
        }
    };

    public string LanguagePreference { get; private set; } = "auto";
    public string MeasurementPreference { get; private set; } = "auto";

    public CultureInfo Culture => new(ResolveLanguage());

    public string MeasurementSystem => MeasurementPreference == "auto"
        ? ResolveAutomaticMeasurementSystem()
        : MeasurementPreference;

    public void Load()
    {
        LanguagePreference = NormalizeLanguage(Preferences.Default.Get(LanguagePreferenceKey, "auto"));
        MeasurementPreference = NormalizeMeasurementSystem(Preferences.Default.Get(MeasurementPreferenceKey, "auto"));
    }

    public void SetLanguage(string? language)
    {
        LanguagePreference = NormalizeLanguage(language);
        Preferences.Default.Set(LanguagePreferenceKey, LanguagePreference);
        ApplyCulture();
    }

    public void SetMeasurementSystem(string? measurementSystem)
    {
        MeasurementPreference = NormalizeMeasurementSystem(measurementSystem);
        Preferences.Default.Set(MeasurementPreferenceKey, MeasurementPreference);
    }

    public void ApplyCulture()
    {
        var culture = Culture;
        CultureInfo.DefaultThreadCurrentCulture = culture;
        CultureInfo.DefaultThreadCurrentUICulture = culture;
    }

    public string T(string key)
    {
        var language = ResolveLanguage();
        if (Strings.TryGetValue(language, out var table) && table.TryGetValue(key, out var value))
        {
            return value;
        }

        return Strings["it"].TryGetValue(key, out var fallback) ? fallback : key;
    }

    private string ResolveLanguage()
    {
        if (LanguagePreference != "auto")
        {
            return LanguagePreference;
        }

        var twoLetter = CultureInfo.CurrentUICulture.TwoLetterISOLanguageName;
        return Strings.ContainsKey(twoLetter) ? twoLetter : "en";
    }

    private static string ResolveAutomaticMeasurementSystem()
    {
        var region = RegionInfo.CurrentRegion.TwoLetterISORegionName;
        return region is "US" or "LR" or "MM" ? "imperial" : "metric";
    }

    private static string NormalizeLanguage(string? language) =>
        !string.IsNullOrWhiteSpace(language) && SupportedLanguages.Contains(language) ? language.ToLowerInvariant() : "auto";

    private static string NormalizeMeasurementSystem(string? measurementSystem) =>
        !string.IsNullOrWhiteSpace(measurementSystem) && SupportedMeasurementSystems.Contains(measurementSystem) ? measurementSystem.ToLowerInvariant() : "auto";
}