SecureDocumentAccessorProxy.cs

public class SecureDocumentAccessorProxy : IDocumentAccessor
{
    private DocumentAccessor _documentAccessor;
    private readonly string _userId;

    public SecureDocumentAccessorProxy(string userId)
    {
        _userId = userId;
        _documentAccessor = new DocumentAccessor();
    }

    public string? FetchDocument(string documentId)
    {
        // Check if the user has access to the document
        if (!HasAccess(_userId, documentId))
        {
            Console.WriteLine($"Access denied for user {_userId} to document {documentId}.");
            return null;
        }

        // Log the access for audit
        LogAccess(_userId, documentId);

        // Delegate the call to the real document accessor
        Console.WriteLine($"User {_userId} accessed document {documentId}.");
        return _documentAccessor.FetchDocument(documentId);
    }

    private bool HasAccess(string userId, string documentId)
    {
        // Placeholder for access control logic
        // In a real system, this would check user permissions against the document's access control list.
        return true; // Assume all users have access for this example
    }

    private void LogAccess(string userId, string documentId)
    {
        // Placeholder for logging mechanism
        // In a real system, this would write to a secure log for audit purposes.
        Console.WriteLine($"Access log: User {userId} accessed {documentId} on {DateTime.UtcNow}.");
    }
}