using clojure.clr.api;
using clojure.lang;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

/* This appliction shows how C# can send an arbitrary string to Clojure to be evaluated.
 * This works like a REPL.  But it's event driven, not in a loop.  And the code comes
 * from a C# string, not a stream.
 * 
 * 
 * Things to try:
 * 
 * (+ 2 3)
 * Like 2 + 3 in C#
 * 
 * (+ 2 (* 3 4))
 * Like 2 + 3 * 4 in C#
 * 
 * (import (System.Windows.Forms MessageBox))
 * (MessageBox/Show "Hi from clojure-clr!" "Clojure-CLR Dialog")
 * Display a message box.  
 * From http://www.myclojureadventure.com/2011/10/getting-started-with-clojure-clr.html
 * 
 * (System.Windows.Forms.MessageBox/Show "Hi from clojure-clr!" "Clojure-CLR Dialog")
 * Same result as above, but all in one command.  (An older version of this program only
 * executed the first command it saw and ignored the rest.)
 * 
 * WindowsFormsApplication1.MainForm
 * Grab the main form's class.
 * 
 * WindowsFormsApplication1.MainForm/Instance
 * Grab the main form object.
 * 
 * (.-_intField WindowsFormsApplication1.MainForm/Instance)
 * Read the public field named _intField.
 * See http://clojure.org/reference/java_interop and http://clojure.org/reference/java_interop for general info about accessing C#.
 * 
 * (set! (.-_intField WindowsFormsApplication1.MainForm/Instance) (* 2 3))
 * Set the value of the public field named _intField to 6.
 * 
 * (.GetTextBox WindowsFormsApplication1.MainForm/Instance))
 * Grab the text box at the top of the main form.
 * The actual field textBox1 is private, so I made a public function GetTextBox() to access it.
 * 
 * (macroexpand '(.GetTextBox WindowsFormsApplication1.MainForm/Instance)))
 * The underlying command is a single dot.  That will look up a field or method.
 * .GetTextBox is a macro that makes things a little easier to write.
 * 
 * (.Text (.GetTextBox WindowsFormsApplication1.MainForm/Instance)))
 * Read the text from the text box.
 * 
 * (set! (.Text (.GetTextBox WindowsFormsApplication1.MainForm/Instance)) "Hello World")
 * Set the text in the text box.
 * 
 * (. WindowsFormsApplication1.MainForm/Instance IntProperty)
 * (set! (. WindowsFormsApplication1.MainForm/Instance IntProperty) 99)
 * (set! (.-IntProperty WindowsFormsApplication1.MainForm/Instance) 199)
 * (.-IntProperty WindowsFormsApplication1.MainForm/Instance)
 * You access a property the same way you access a field.
 * 
 * (do
 *   (use '[clojure.string :only (join)])
 *   (let [window WindowsFormsApplication1.MainForm/Instance
 *         input (.Text (.GetTextBox window))
 *         output (join ["The user said {" input "}."])]
 *     (set! (.Text (.GetLabel window)) output))
 *   'Success!
 * )
 * This examples goes full circle.  The clojure code reads a value from the .NET form,
 * manipulates the value, and then displays the result back on the form.  This example
 * uses the clojure "do" command so we can execute the entire example at once, as one
 * big command.  ("do" is no longer required here as we are now using "load-string" in
 * the code below.)
 * 
 * (do
 *   (use '[clojure.string :only (join)])
 *   (let [window WindowsFormsApplication1.MainForm/Instance
 *         input (.. window (GetTextBox) Text)
 *         output (join ["The user said {" input "}."])]
 *     (set! (.. window (GetLabel) Text) output))
 *   'Success!
 * )
 * This does the same thing as the previous example.  This uses clojure's .. command
 * to make the code look a little more like C++, C#, Java, etc.  Read the value of
 * the variable named window, then call the GetTextBox() method on that with no
 * arguments.  Then look for the Text property in the result of GetTextBox().
 * In C# that would be:  window.GetTextBox().Text
 */

namespace WindowsFormsApplication1
{
    public partial class MainForm : Form
    {
        public static MainForm Instance { get; private set; }

        public MainForm()
        {
            InitializeComponent();
            Instance = this;
        }

        private static readonly IFn EVAL = Clojure.var("clojure.core", "eval");
        private static readonly IFn READ_STRING = Clojure.var("clojure.core", "read-string");

        // Note:  The Clojure read-string function is not the same as the C# Clojure.read()
        // function.  In some cases, like "(+ 1 2)" or "(quote (+ 1 2))",  they give the same
        // result.  But read-string will expand macros.  For example read-string will expand
        // "'(+ 1 2)" into "(quote (+ 1 2))", but Clojure.read() will not.  Since our goal
        // is to execute code, like a REPL, we need to use read-string.  My solution for
        // reading and executing a string was inspired by
        // http://stackoverflow.com/questions/6672934/how-to-call-clojure-macros-from-java#6673881
        //
        // https://clojuredocs.org/clojure.core/load-string Offers another way to do this.
        // It might have some advantages.  read-string followed by eval will execute the first
        // expression it finds, ignore the rest, and return the result of that first expression.
        // load-string will execute all expressions in order, and return the result of the last
        // one.

        private static readonly IFn LOAD_STRING = Clojure.var("clojure.core", "load-string");

        private void executeButton_Click(object sender, EventArgs e)
        {
            try
            {
                // This would execute the code.  It worked as long as the input was a single
                // s-expression.  If you had more, this would read and evaluate the first 
                // s-expression in the string, and silently ignore the rest.  The Clojure 
                // "load-string" function, shown next, will read and execute all s-expressions,
                // and return the value of the last one.
                //object source = READ_STRING.invoke(sourceTextBox.Text);
                //object result = EVAL.invoke(source);
                object result = LOAD_STRING.invoke(sourceTextBox.Text);

                if (null == result)
                    resultTextBox.Text = "null";
                else
                    resultTextBox.Text = result.ToString() + " (" + result.GetType().Name + ")";
            }
            catch (Exception ex)
            {
                resultTextBox.Text = ex.ToString();
            }
        }

        public Label GetLabel()
        {
            return label1;
        }

        public TextBox GetTextBox()
        {
            return textBox1;
        }

        public int _intField = 42;

        public int IntProperty { get; set; }
    }
}