using System;

namespace HC_APTBS.Services
{
    /// <summary>
    /// Provides runtime language switching and localised string retrieval.
    /// </summary>
    /// <remarks>
    /// XAML bindings use <c>{DynamicResource Key}</c> which update automatically
    /// when the merged <see cref="System.Windows.ResourceDictionary"/> is swapped.
    /// C# code uses <see cref="GetString"/> for the same keys.
    /// </remarks>
    public interface ILocalizationService
    {
        /// <summary>Current language code — <c>"ESP"</c> or <c>"ENG"</c>.</summary>
        string CurrentLanguage { get; }

        /// <summary>
        /// Switches the active UI language by swapping the merged resource dictionary
        /// and persisting the choice to <c>config.xml</c>.
        /// Must be called from the UI thread.
        /// </summary>
        /// <param name="languageCode"><c>"ESP"</c> for Spanish or <c>"ENG"</c> for English.</param>
        void SetLanguage(string languageCode);

        /// <summary>
        /// Retrieves a localised string by resource key.
        /// Returns the key itself when no matching resource is found (fail-visible).
        /// </summary>
        /// <param name="key">Resource key defined in <c>Resources/Strings.*.xaml</c>.</param>
        string GetString(string key);

        /// <summary>
        /// Raised after the active language dictionary has been swapped.
        /// ViewModels subscribe to refresh any cached localised strings.
        /// </summary>
        event Action? LanguageChanged;
    }
}