/**
 *   Copyright (c) Rich Hickey. All rights reserved.
 *   The use and distribution terms for this software are covered by the
 *   Common Public License 1.0 (http://opensource.org/licenses/cpl.php)
 *   which can be found in the file CPL.TXT at the root of this distribution.
 *   By using this software in any fashion, you are agreeing to be bound by
 * 	 the terms of this license.
 *   You must not remove this notice, or any other, from this software.
 **/

using System;
using System.Threading;

namespace clojure.lang
{
public class Var :  AFn
    {
public readonly Symbol sym;
public Namespace ns;
public Binding binding;
public IFn fn;  //todo, bind to throw stub?
public IFn setfn;
volatile IPersistentMap threadBindings = PersistentArrayIdentityMap.EMPTY;

internal Var(Symbol sym, Namespace ns)
	{
	if(sym.GetType() != typeof(Symbol))
	    throw new ArgumentException("Only simple symbols can be vars");
	this.ns = ns;
	this.sym = sym;
	}

override public String ToString()
	{
	if(ns == null)
		return "#:" + sym;
	return ns.name + ":" + sym;
	}

public Var bind(Object val)
	{
	if(binding == null)
		binding = new Binding(val);
	else
		binding.val = val;

    if (val is IFn)
        this.fn = (IFn)val;
    else
        this.fn = null; //todo, bind to throw stub?

	return this;
	}


public Object getValue()
	{
	Binding binding = getBinding();
	if(binding != null)
		return binding.val;
	throw new InvalidOperationException(this.ToString() + " is unbound.");
	}

public Object setValue(Object val)
	{
	Binding b = getThreadBinding();
	if(b != null)
		return b.val = val;
	if(binding == null)
        throw new InvalidOperationException(this.ToString() + " is unbound.");

	if(val is IFn)
		this.fn = (IFn) val;
	else
		this.fn = null; //todo, bind to throw stub?

	return binding.val = val;
	}

public Binding pushThreadBinding(Object val) {
    Binding ret = new Binding(val, getThreadBinding());
    setThreadBinding(ret);
    return ret;
}

public void popThreadBinding() {
    setThreadBinding(getThreadBinding().rest);
}

Binding getBinding()
	{
	Binding b = getThreadBinding();
	if(b != null)
		return b;
	return binding;
	}

Binding getThreadBinding()
	{
	if (threadBindings.count() > 0)
		return (Binding)threadBindings.get(Thread.CurrentThread);
	return null;
	}

void setThreadBinding(Binding b) {
    Thread thread = Thread.CurrentThread;
    IPersistentMap tb;
    IPersistentMap newtb;
    do
        {
        tb = threadBindings;
        if (b == null)
            newtb = tb.remove(thread);
        else
            newtb = tb.put(thread, b);
		} while (tb != Interlocked.CompareExchange(ref threadBindings, newtb, tb));
}

override public Object invoke() /*throws Exception*/
	{
	return fn.invoke();
	}

override public Object invoke( Object arg1) /*throws Exception*/
	{
	return fn.invoke(arg1);
	}

override public Object invoke( Object arg1, Object arg2) /*throws Exception*/
	{
	return fn.invoke(arg1,arg2);
	}

override public Object invoke( Object arg1, Object arg2, Object arg3) /*throws Exception*/
	{
	return fn.invoke(arg1,arg2,arg3);
	}

override public Object invoke( Object arg1, Object arg2, Object arg3, Object arg4) /*throws Exception*/
	{
	return fn.invoke(arg1,arg2,arg3,arg4);
	}

override public Object invoke( Object arg1, Object arg2, Object arg3, Object arg4, Object arg5)
		/*throws Exception*/
	{
	return fn.invoke(arg1,arg2,arg3,arg4,arg5);
	}

override public Object invoke( Object arg1, Object arg2, Object arg3, Object arg4, Object arg5, ISeq args)
		/*throws Exception*/
	{
	return fn.invoke(arg1,arg2,arg3,arg4,arg5,args);
	}
    }
}