1 files changed, 44 insertions, 0 deletions
diff --git a/MediaBrowser.Providers/Manager/MetadataLanguageUtils.cs b/MediaBrowser.Providers/Manager/MetadataLanguageUtils.cs
new file mode 100644
index 0000000000..92a16feaee
--- /dev/null
+++ b/MediaBrowser.Providers/Manager/MetadataLanguageUtils.cs
@@ -0,0 +1,44 @@
+using System;
+
+namespace MediaBrowser.Providers.Manager;
+
+/// <summary>
+/// Helpers for comparing the language of fetched metadata with the language that was requested.
+/// </summary>
+internal static class MetadataLanguageUtils
+{
+    /// <summary>
+    /// Gets the language subtag of a language tag, e.g. "es" for "es-ES".
+    /// </summary>
+    /// <param name="language">The language tag.</param>
+    /// <returns>The language subtag, lowercased, or <c>null</c> if none was given.</returns>
+    public static string? GetLanguageSubtag(string? language)
+    {
+        if (string.IsNullOrEmpty(language))
+        {
+            return null;
+        }
+
+        var separator = language.IndexOf('-', StringComparison.Ordinal);
+
+        return (separator == -1 ? language : language[..separator]).ToLowerInvariant();
+    }
+
+    /// <summary>
+    /// Determines whether a provider result can be considered to be in the requested language.
+    /// </summary>
+    /// <param name="resultLanguage">The language the provider reported for its result, if any.</param>
+    /// <param name="preferredLanguage">The language that was requested, if any.</param>
+    /// <returns><c>true</c> if the result is in the requested language or either language is unknown.</returns>
+    public static bool MatchesPreferredLanguage(string? resultLanguage, string? preferredLanguage)
+    {
+        // A provider that doesn't report a language cannot be judged, assume it honored the request
+        if (string.IsNullOrEmpty(resultLanguage) || string.IsNullOrEmpty(preferredLanguage))
+        {
+            return true;
+        }
+
+        // Compare on the language subtag only so that e.g. "es" matches "es-ES"
+        return string.Equals(GetLanguageSubtag(resultLanguage), GetLanguageSubtag(preferredLanguage), StringComparison.Ordinal);
+    }
+}