var Form = require ('./form');

module.exports = new Class
({
	Extends: Vn.Param
	,Tag: 'db-param'
	,Parent: 'form'
	,Properties:
	{
		/**
		 * The form field referenced by this param.
		 */
		column:
		{
			type: String
			,set: function (x)
			{ 
				this._columnName = x;
				this.refresh ();
			}
			,get: function ()
			{
				this._columnName;
			}
		},
		/**
		 * The form referenced by this param.
		 */
		form:
		{
			type: Form
			,set: function (x)
			{
				this.link ({_set: x},
				{
					'change': this.onSetChange
				});

				this.refresh ();
			}
			,get: function ()
			{
				return this._set;
			}
		},
		/**
		 * Determines whether the link to the form is unidirectional, ie, a
		 * change in the form updates the parameter but not vice versa.
		 */
		oneWay:
		{
			type: Boolean
			,set: function (x)
			{
				this._oneWay = x;
			}
			,get: function ()
			{
				return this._oneWay;
			}
		}
	}

	,_columnName: null
	,_set: null
	,_setLock: false
	,_oneWay: false
	,_setValue: null
	
	,initialize: function (props)
	{
		this.parent (props);
		this.on ('changed', this.onChange, this);
	}
	
	,refresh: function ()
	{
		if (this._set)
			this.onSetChange ();
	}

	,onSetChange: function ()
	{
		this._setLock = true;
		var formValue = this._set.get (this._columnName);
		this.value = formValue;
		this._setLock = false;
	}

	,onChange: function ()
	{
		if (!this._setLock && this._columnName && !this.oneWay)
			this._set.set (this._columnName, this._value);
	}
});