var exports = module.exports = {};

/*Simple exponential smoothing */

exports.SimpleExponentialSmoothing = function(data, alpha)
{
	if(data == null)
	{
		throw "data parameter is null";
	}
	else if(data.length < 2)
	{
		throw "data doesn't contain enough data to make a prediction";
	}

	if(alpha > 1 || alpha < 0)
	{
		throw "alpha parameter must be between 0 and 1";
	}

	this.data = data;
	this.alpha = alpha;
	this.forecast = null;
};

exports.SimpleExponentialSmoothing.prototype.predict = function()
{
	var forecast = Array();
	forecast[0] = null;
	forecast[1] = 0.5*(this.data[0] + this.data[1]);

	for(var i = 2; i <= this.data.length; ++i)
	{
		forecast[i] = this.alpha*(this.data[i-1] - forecast[i-1]) + forecast[i-1];
	}

	this.forecast = forecast;
	return forecast;
};

exports.SimpleExponentialSmoothing.prototype.getForecast = function()
{
	if(this.forecast == null)
	{
		this.predict();
	}
	return this.forecast;
}

exports.SimpleExponentialSmoothing.prototype.computeMeanSquaredError = function()
{
	var SSE = 0.0;
	var n = 0;
	for(var i = 0; i < this.data.length; ++i)
	{
		if(this.data[i] != null && this.forecast[i] != null)
		{
			SSE += Math.pow(this.data[i] - this.forecast[i], 2);
			n++;
		}

	}
	return 1/(n-1)*SSE;
};

exports.SimpleExponentialSmoothing.prototype.optimizeParameter = function(iter)
{
	var incr = 1/iter;
	var bestAlpha = 0.0;
	var bestError = -1;
	this.alpha = bestAlpha;

	while(this.alpha < 1)
	{
		var forecast = this.predict();
		var error = this.computeMeanSquaredError();
		if(error < bestError || bestError == -1)
		{
			bestAlpha = this.alpha;
			bestError = error;
		}
		this.alpha += incr;
	}

	this.alpha = bestAlpha;
	return this.alpha;
}




/*Double exponential smoothing */


exports.DoubleExponentialSmoothing = function(data, alpha)
{
	if(data == null)
	{
		throw "data parameter is null";
	}
	else if(data.length < 2)
	{
		throw "data doesn't contain enough data to make a prediction";
	}

	if(alpha > 1 || alpha < 0)
	{
		throw "alpha parameter must be between 0 and 1";
	}

	this.data = data;
	this.alpha = alpha;
	this.forecast = null;
};

exports.DoubleExponentialSmoothing.prototype.predict =function (horizon)
{
	var smoothings = Object();
	smoothings.first = Array();
	smoothings.second = Array();

	smoothings.first[0] = this.data[0];
	smoothings.first[1] = this.data[1];

	for(var i = 2; i < this.data.length; ++i)
	{
		smoothings.first[i] = this.alpha*this.data[i] + (1-this.alpha)*smoothings.first[i-1];
	}

	smoothings.second[0] = smoothings.first[0];
	for(var i = 1; i < this.data.length; ++i)
	{
		smoothings.second[i] = this.alpha*smoothings.first[i] + (1-this.alpha)*smoothings.second[i-1];
	}

	smoothings.a = Array();
	smoothings.b = Array();
	for(var i = 1; i < this.data.length; ++i)
	{
		smoothings.a[i] = (this.alpha/(1-this.alpha))*(smoothings.first[i] - smoothings.second[i]);
		smoothings.b[i] = 2*smoothings.first[i] - smoothings.second[i];
	}

	var forecast = Array();
	forecast[0] = null;
	forecast[1] = null;
	for(var i = 2; i <= this.data.length; ++i)
	{
		forecast[i] = smoothings.a[i-1] + smoothings.b[i-1];
	}

	for(var i = this.data.length +1; i < this.data.length + horizon; ++i)
	{
		forecast[i] = forecast[i-1] + smoothings.a[this.data.length-1];
	}

	this.forecast = forecast;
	return forecast;
}

exports.DoubleExponentialSmoothing.prototype.getForecast = function()
{
	if(this.forecast == null)
	{
		return null;
	}
	return this.forecast;
}

exports.DoubleExponentialSmoothing.prototype.computeMeanSquaredError = function()
{
	var SSE = 0.0;
	var n = 0;
	for(var i = 0; i < this.data.length; ++i)
	{
		if(this.data[i] != null && this.forecast[i] != null)
		{
			SSE += Math.pow(this.data[i] - this.forecast[i], 2);
			n++;
		}

	}
	return 1/(n-1)*SSE;
};

exports.DoubleExponentialSmoothing.prototype.optimizeParameter = function(iter)
{
	var incr = 1/iter;
	var bestAlpha = 0.0;
	var bestError = -1;
	this.alpha = bestAlpha;

	while(this.alpha < 1)
	{
		var forecast = this.predict();
		var error = this.computeMeanSquaredError();
		if(error < bestError || bestError == -1)
		{
			bestAlpha = this.alpha;
			bestError = error;
		}
		this.alpha += incr;
	}

	this.alpha = bestAlpha;
	return this.alpha;
}

/*Holt smoothing */
exports.HoltSmoothing = function(data, alpha, gamma)
{
	if(data == null)
	{
		throw "data parameter is null";
	}
	else if(data.length < 2)
	{
		throw "data doesn't contain enough data to make a prediction";
	}

	if(alpha > 1 || alpha < 0)
	{
		throw "alpha parameter must be between 0 and 1";
	}

	if(gamma > 1 || gamma < 0)
	{
		throw "gamma parameter must be between 0 and 1";
	}

	this.data = data;
	this.alpha = alpha;
	this.gamma = gamma;
	this.forecast = null;
};

exports.HoltSmoothing.prototype.predict =function (horizon)
{
	A = Array();
	B = Array();

	A[0] = 0;
	B[0] = this.data[0];

	for(var i = 1; i < this.data.length; ++i)
	{
		B[i] = this.alpha*this.data[i] + (1-this.alpha)*(B[i-1] + A[i-1]);
		A[i] = this.gamma*(B[i]-B[i-1])+ (1-this.gamma)*A[i-1];
	}

	var forecast = Array();
	forecast[0] = null;
	for(var i = 1; i <= this.data.length; ++i)
	{
		forecast[i] = A[i-1] + B[i-1];
	}

	for(var i = this.data.length +1; i < this.data.length + horizon; ++i)
	{
		forecast[i] = forecast[i-1] + A[this.data.length - 1];
	}


	this.forecast = forecast;
	return forecast;
}


exports.HoltSmoothing.prototype.getForecast = function()
{
	if(this.forecast == null)
	{
		return null;
	}
	return this.forecast;
}

exports.HoltSmoothing.prototype.computeMeanSquaredError = function()
{
	var SSE = 0.0;
	var n = 0;
	for(var i = 0; i < this.data.length; ++i)
	{
		if(this.data[i] != null && this.forecast[i] != null)
		{
			SSE += Math.pow(this.data[i] - this.forecast[i], 2);
			n++;
		}

	}
	return 1/(n-1)*SSE;
};

exports.HoltSmoothing.prototype.optimizeParameters = function(iter)
{
	var incr = 1/iter;
	var bestAlpha = 0.0;
	var bestError = -1;
	this.alpha = bestAlpha;
	var bestGamma = 0.0;
	this.gamma = bestGamma;

	while(this.alpha < 1)
	{
		while(this.gamma < 1)
		{
			var forecast = this.predict();
			var error = this.computeMeanSquaredError();
			if(error < bestError || bestError == -1)
			{
				bestAlpha = this.alpha;
				bestGamma = this.gamma;
				bestError = error;
			}
			this.gamma += incr;
		}
		this.gamma = 0;
		this.alpha += incr;
	}

	this.alpha = bestAlpha;
	this.gamma = bestGamma;
	return {"alpha":this.alpha, "gamma":this.gamma};
}

/*Holt Winters smoothing */
exports.HoltWintersSmoothing = function(data, alpha, gamma, delta, seasonLength, mult)
{
	if(data == null)
	{
		throw "data parameter is null";
	}
	else if(data.length < 2)
	{
		throw "data doesn't contain enough data to make a prediction";
	}

	if(alpha > 1 || alpha < 0)
	{
		throw "alpha parameter must be between 0 and 1";
	}

	if(gamma > 1 || gamma < 0)
	{
		throw "gamma parameter must be between 0 and 1";
	}

	if(delta > 1 || delta < 0)
	{
		throw "delta parameter must be between 0 and 1";
	}

	if(seasonLength < 0)
	{
		throw "seasonLength parameter must be a positive integer";
	}

	if(mult != true && mult != false)
	{
		throw "mult parameter must be a boolean";
	}

	this.data = data;
	this.alpha = alpha;
	this.gamma = gamma;
	this.delta = delta;
	this.seasonLength = seasonLength;
	this.mult = mult;
	this.forecast = null;
};

exports.HoltWintersSmoothing.prototype.predict =function ()
{
	if(this.mult)
	{
		return this.predictMult();
	}
	else
	{
		return this.predictAdd();
	}
}

exports.HoltWintersSmoothing.prototype.predictAdd = function()
{
	A = Array();
	B = Array();
	S = Array();

	A[this.seasonLength-1] = 0;
	var averageFirstSeason = 0;
	for(var i = 0; i < this.seasonLength; ++i)
	{
		averageFirstSeason += this.data[i];
	}
	B[this.seasonLength-1] = averageFirstSeason/this.seasonLength;

	for(var i = 0; i < this.seasonLength; ++i)
	{
		S[i] = this.data[i] - averageFirstSeason/this.seasonLength;
	}

	for(var i = this.seasonLength; i < this.data.length; ++i)
	{
		B[i] = this.alpha*(this.data[i]- S[i - this.seasonLength])+(1-this.alpha)*(B[i-1]+A[i-1]);
		A[i] = this.gamma*(B[i]-B[i-1])+(1-this.gamma)*A[i-1];
		S[i] = this.delta*(this.data[i]-B[i])+(1-this.delta)*S[i-this.seasonLength];
	}

	var forecast = Array();
	for(var i = 0; i < this.seasonLength; ++i)
	{
		forecast[i]= null;
	}

	for(var i = this.seasonLength; i < this.data.length; ++i)
	{
		forecast[i] = A[i-1] + B[i-1] + S[i - this.seasonLength];
	}

	for(var i = this.data.length; i < this.data.length + this.seasonLength; ++i)
	{
		forecast[i] = B[this.data.length-1] + (i - this.data.length + 1)*A[this.data.length-1] + S[i - this.seasonLength];
	}

	this.forecast = forecast;
	return forecast;
}

exports.HoltWintersSmoothing.prototype.predictMult = function()
{
	A = Array();
	B = Array();
	S = Array();

	A[this.seasonLength-1] = 0;
	var averageFirstSeason = 0;
	for(var i = 0; i < this.seasonLength; ++i)
	{
		averageFirstSeason += this.data[i];
	}
	B[this.seasonLength-1] = averageFirstSeason/this.seasonLength;

	for(var i = 0; i < this.seasonLength; ++i)
	{
		S[i] = (this.data[i])/(averageFirstSeason/this.seasonLength);
	}

	for(var i = this.seasonLength; i < this.data.length; ++i)
	{
		B[i] = this.alpha*(this.data[i]/S[i - this.seasonLength])+(1-this.alpha)*(B[i-1]+A[i-1]);
		A[i] = this.gamma*(B[i]-B[i-1])+(1-this.gamma)*A[i-1];
		S[i] = this.delta*(this.data[i]/B[i])+(1-this.delta)*S[i-this.seasonLength];
	}

	var forecast = Array();
	for(var i = 0; i < this.seasonLength; ++i)
	{
		forecast[i]= null;
	}

	for(var i = this.seasonLength; i < this.data.length; ++i)
	{
		forecast[i] = (A[i-1] + B[i-1])*S[i - this.seasonLength];
	}

	for(var i = this.data.length; i < this.data.length + this.seasonLength; ++i)
	{
		forecast[i] = (B[this.data.length-1] + (i - this.data.length + 1)*A[this.data.length-1])*S[i -this.seasonLength];
	}

	this.forecast = forecast;
	return forecast;
}

exports.HoltWintersSmoothing.prototype.getForecast = function()
{
	if(this.forecast == null)
	{
		this.predict();
	}
	return this.forecast;
}

exports.HoltWintersSmoothing.prototype.computeMeanSquaredError = function()
{
	var SSE = 0.0;
	var n = 0;
	for(var i = 0; i < this.data.length; ++i)
	{
		if(this.data[i] != null && this.forecast[i] != null)
		{
			SSE += Math.pow(this.data[i] - this.forecast[i], 2);
			n++;
		}

	}
	return 1/(n-1)*SSE;
};

exports.HoltWintersSmoothing.prototype.optimizeParameters = function(iter)
{
	var incr = 1/iter;
	var bestAlpha = 0.0;
	var bestError = -1;
	this.alpha = bestAlpha;
	var bestGamma = 0.0;
	this.gamma = bestGamma;
	var bestDelta = 0.0;
	this.delta = bestDelta;

	while(this.alpha < 1)
	{
		while(this.gamma < 1)
		{
			while(this.delta < 1)
			{
				var forecast = this.predict();
				var error = this.computeMeanSquaredError();
				if(error < bestError || bestError == -1)
				{
					bestAlpha = this.alpha;
					bestGamma = this.gamma;
					bestDelta = this.delta;
					bestError = error;
				}
				this.delta += incr;
			}
			this.delta = 0;
			this.gamma += incr;
		}
		this.gamma = 0;
		this.alpha += incr;
	}

	this.alpha = bestAlpha;
	this.gamma = bestGamma;
	this.delta = bestDelta;
	return {"alpha":this.alpha, "gamma":this.gamma, "delta":this.delta};
}

/*Moving average */

exports.MovingAverage = function(data)
{
	if(data == null)
	{
		throw "data parameter is null";
	}
	else if(data.length < 3)
	{
		throw "data doesn't contain enough data to make a prediction";
	}

	this.data = data;
};

exports.MovingAverage.prototype.smooth = function(order)
{
	if(order < 1)
	{
		throw "order parameter must be a positive integer";
	}

	var result = Array();

	for(var i = order; i < this.data.length - order ; ++i)
	{
		result[i] = 0;
		for(var j = i - order; j <= i + order; j++)
		{
			result[i] += this.data[j];
		}
		result[i] /= 2*order +1;
	}

	return result;
};