using System;
using System.IO;

namespace _158326_Week_7_Singletons
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("158.326 Software Architecture");
            Console.WriteLine("\tWeek 7 - Singleton Design Pattern");
            Console.WriteLine("\tSingletons are instanced classes that can have only 0 or 1 instances of that class in existance in the application (Multitons are a variant that restricts the maximum number of instances)");
        }
    }

    /// <summary>
    /// Represents a singleton file stream; useful for logs etc., where access to a specific file should be performed singularly
    /// (don't open multiple streams on the same file)
    /// </summary>
    sealed class FileSingleton
    {
        /// <summary>
        /// Store the instance in a private, static variable
        /// </summary>
        private static FileSingleton instance;

        /// <summary>
        /// Path of the file to open
        /// </summary>
        public static Uri FilePath { get; set; } = new Uri("\\log.txt", UriKind.Relative); // Opens exactly one file stream on log.txt and will always return that stream

        // We can define instance variables here:
        public FileStream OpenedFileStream { get; set; } // Calling FileSingleton.GetInstance().OpenedFileStream will always return this object


        // We can also define  

        /// <summary>
        /// The default constructor must be implemented, and as private so only functions in this class may call it
        /// This restricts the creation of this instance to local methods, so by restricting constructor calls
        /// to GetInstance(), we can ensure that only one instance is created
        /// </summary>
        private FileSingleton() { }

        
        /// <summary>
        /// Gets the initialised instance of FileSingleton
        /// </summary>
        /// <returns></returns>
        public static FileSingleton GetInstance()
        {
            if (instance is null)
            {
                instance = new FileSingleton();
            }
            return instance;
        }
    }
}