using System;
using System.Collections.Generic;
using System.Text;
using System.Collections;

using System;
using System.Collections.Generic;
using System.Text;
using System.Collections;

// although a type based factory is simple and allows addition of types at
// runtime through discovery it is less efficient than early binding
// this project demonstrates the use of inheritance to combine the efficiency
// of early binding of classes known at compile time and late binding
// for classes discovered at runtime.
// This project demonstrates
// 1) the reuse of code in an existing class factory at compile time 
// 2) the ability to mix late binding at runtime with early binding at compile time
// into a single class factory using simple inheritance
namespace ClassFactory
{
    // declare our interfaces
    // this class would be in a separate dll
    public interface IDrawable
    {
        void Draw();
    }
    // define two concrete classes in this project
    public class Circle : IDrawable
    {
        public void Draw() { System.Console.WriteLine("Circle"); }
    }
    public class Square : IDrawable
    {
        public void Draw() { System.Console.WriteLine("Square"); }
    }
    public class Oval : IDrawable
    {
        public void Draw() { System.Console.WriteLine("Oval"); }
    }
    // if this class is to be discovered at runtime as a plugin
    // it would be in a separate dll at runtime
    public class Triangle : IDrawable
    {
        public void Draw() { System.Console.WriteLine("Triangle"); }
    }
    // BASE_FACTORY A class factory that returns concrete objects of type IDrawable
    // using early binding of known classes at compile time
    public class BaseFactory
    {
        public virtual IDrawable GetInstance(string key)
        {
            //if (key == null) { return null; }
            if (key == "Circle") 
            {
                return new Circle();
            }
            else if (key == "Square")
            {
                return new Square();
            }
            else
            {
                return null;
            }
        }
        /*[STAThread]
        public static void Main(string[] args)
        {
            BaseFactory factory= new BaseFactory();
            IDrawable c = factory.GetInstance("Circle");
            if (c != null) { c.Draw();}
            IDrawable s = factory.GetInstance("Square");
            if (s != null) { s.Draw(); }
            System.Console.ReadLine();
        }*/
    }
    // DERIVED_FACTORY demonstrates reuse of code by extending from BaseFactory and 
    // adding a new concrete class Triangle at _compile_ time
    // still using early binding
    public class DerivedFactory : BaseFactory
    {
        public override IDrawable GetInstance(string key)
        {
            // if (key == null) {return null;}
            if (key == "Oval") 
            {
                return new Oval();
            }
            else
            {
                return base.GetInstance(key);
            }
        }
        /*[STAThread]
        public static void Main(string[] args)
        {
            DerivedFactory factory = new DerivedFactory();
            IDrawable c = factory.GetInstance("Circle");
            if (c != null) { c.Draw(); }
            IDrawable s = factory.GetInstance("Square");
            if (s != null) { s.Draw(); }
            IDrawable t = factory.GetInstance("Oval");
            if (t != null) { t.Draw(); }
            System.Console.ReadLine();
        }*/
    }
    // RUNTIME_FACTORY demonstrates reuse of code in the base factory but demonstrates
    // adding new IDrawables at _runtime_
    // using late binding and reflection
    // more efficient than a type based factory alone since this solution
    // uses early binding for compile time classes and late binding for plugins
    // We basically handle plug in classes first and then pass any un-handled
    // request to the base factory
    public class RuntimeFactory : BaseFactory
    {
        private Hashtable hashTypes = new Hashtable(); // must contain only IDrawable
        public RuntimeFactory()
            : base()
        {
            // you would need to discover ITriangle classes at runtime
            // from a plugins folder and add them here
            // if (typeof(IDrawableShape).IsAssignableFrom(t)
            //		&& !t.IsAbstract)) // safer
            //	{
            //		...
            //	}
            Type t = typeof(Triangle);
            this.hashTypes.Add(t.Name, typeof(Triangle));  // triangle plugin
        }
        public override IDrawable GetInstance(string key)
        {
            if (key != null && this.hashTypes.ContainsKey(key)) // case sensitive!
            {
                Type t = (Type)hashTypes[key];
                // dynamically load this class
                return (IDrawable)Activator.CreateInstance(t);
            }
            else
            {
                return base.GetInstance(key);
            }
        }
        [STAThread]
        public static void Main(string[] args)
        {
            System.Console.WriteLine("Early Bound Classes:");
            DerivedFactory factoryD = new DerivedFactory();
            IDrawable c = factoryD.GetInstance("Circle");
            if (c != null) { c.Draw(); }
            IDrawable s = factoryD.GetInstance("Square");
            if (s != null) { s.Draw(); }
            IDrawable t = factoryD.GetInstance("Oval");
            if (t != null) { t.Draw(); }

            System.Console.WriteLine("Early and Late Bound Classes.");
            RuntimeFactory factoryR = new RuntimeFactory();
            IDrawable c1 = factoryR.GetInstance("Circle");
            if (c1 != null) { c1.Draw(); }
            IDrawable s1 = factoryR.GetInstance("Square");
            if (s1 != null) { s1.Draw(); }
            IDrawable t1 = factoryR.GetInstance("Triangle");
            if (t1 != null) { t1.Draw(); }

            System.Console.WriteLine("Test null input");
            IDrawable n = factoryR.GetInstance(null);
            if (n == null) { System.Console.WriteLine("No Class"); }

            System.Console.WriteLine("Test invalid input");
            IDrawable invalid = factoryR.GetInstance("oval");
            if (invalid == null) { System.Console.WriteLine("No Class"); }

            System.Console.ReadLine();
        }
    }
}

            if (key == "Circle") 
            {
                return new Circle();
            }

            if (key != null && this.hashTypes.ContainsKey(key)) // case sensitive!
            {
                Type t = (Type)hashTypes[key];
                // dynamically load this class
                return (IDrawable)Activator.CreateInstance(t);
            }