namespace SharepointToolbox.Core.Helpers;

/// <summary>
/// Pure static helpers for classifying SharePoint permission entries.
/// </summary>
public static class PermissionEntryHelper
{
    /// <summary>
    /// Returns true when the login name is a B2B guest (contains #EXT#).
    /// </summary>
    public static bool IsExternalUser(string loginName) =>
        loginName.Contains("#EXT#", StringComparison.OrdinalIgnoreCase);

    /// <summary>
    /// Removes "Limited Access" from the supplied permission levels.
    /// Returns the remaining levels; returns an empty list when all are removed.
    /// </summary>
    public static IReadOnlyList<string> FilterPermissionLevels(IEnumerable<string> levels) =>
        levels
            .Where(l => !string.Equals(l, "Limited Access", StringComparison.OrdinalIgnoreCase))
            .ToList();

    /// <summary>
    /// Returns true when the login name represents an internal sharing-link group
    /// or the "Limited Access System Group" pseudo-principal.
    /// </summary>
    public static bool IsSharingLinksGroup(string loginName) =>
        loginName.StartsWith("SharingLinks.", StringComparison.OrdinalIgnoreCase)
        || loginName.Equals("Limited Access System Group", StringComparison.OrdinalIgnoreCase);
}