var VnObject = require ('./object');
var Lot = require ('./lot');
var Type = require ('./type');

module.exports = new Class
({
	Extends: VnObject
	,Tag: 'vn-param'
	,Child: 'param'
	,Properties:
	{
		param:
		{
			type: Object
			,set: function (x)
			{
				this.link ({_param: x}, {'changed': this._onParamChange});
				this._refreshParam ();
			}
			,get: function ()
			{
				return this._param;
			}
		},
		key:
		{
			type: String
			,set: function (x)
			{
				this._key = x;
				this._onLotChange ();
			}
			,get: function ()
			{
				return this._key;
			}
		},
		value:
		{
			type: Object
			,set: function (x)
			{
				this._setValue (x, true);
			}
			,get: function ()
			{
				return this._value;
			}
		},
		type:
		{
			type: Type
			,set: function (x)
			{
				this._type = x;
				this._onLotChange ();
			}
			,get: function ()
			{
				return this._type;
			}
		},
		lot:
		{
			type: Lot
			,set: function (x)
			{
				this.link ({_lot: x}, {'change': this._onLotChange});
				this._onLotChange ();
			}
			,get: function ()
			{
				return this._lot;
			}
		},
		/**
		 * Determines whether the link to the form is unidirectional, ie, a
		 * change in the lot updates the parameter but not vice versa.
		 */
		oneWay:
		{
			type: Boolean
			,set: function (x)
			{
				this._oneWay = x;
			}
			,get: function ()
			{
				return this._oneWay;
			}
		}
	}
	
	,_lotLock: false
	,_paramLock: false
	,_value: undefined
	,_lot: null
	,_key: null
	,_type: null
	,_oneWay: false

	,_onLotChange: function ()
	{
		if (this._lotLock || !this._key || !this._lot)
			return;

		var newValue = this._lot.get (this._key, this._type);

		this._lotLock = true;
		this._setValue (newValue, true);
		this._lotLock = false;
	}
	
	,_setValue: function (newValue, signal)
	{
		if (newValue == this._value)
			return;
	
		if (newValue instanceof Date)
			newValue = newValue.clone ();

		this._value = newValue;

		if (this._lot && this._key && !this._lotLock && !this._oneWay)
		{
			this._lotLock = true;
			this._lot.set (this._key, newValue);
			this._lotLock = false;
		}

		this._refreshParam ();

		if (signal)
			this.signalEmit ('changed', newValue);
	}

	,_refreshParam: function ()
	{
		if (this._param && !this._paramLock)
		{
			this._paramLock = true;
			this._param.value = this._value;
			this._paramLock = false;
		}
	}
	
	,_onParamChange: function ()
	{
		if (this._paramLock)
			return;

		this._paramLock = true;
		this._setValue (this._param.value);
		this._paramLock = false;
	}
});