#include "util.h"

int allNumbers(object list)
{
	object *currentCell = &list;
	while (TYPE(*currentCell) != nilObject)
	{
		if (TYPE(CAR(*currentCell)) != numberObject)
		{
			return 0;
		}
		currentCell = &CDR(*currentCell);
	}
	return 1;
}

object add(object parameters)
{
	object result;
	TYPE(result) = numberObject;

	if (!allNumbers(parameters))
	{
		TYPE(result) = errorObject;
		ERR(result) = typeError;
	}
	else if (listLength(parameters) == 0)
	{
		result = longlongToNumber(0LL);
	}
	else
	{
		object first, rest;
		first = CAR(parameters);
		rest = add(CDR(parameters));

		result = plusNum(first, rest);
	}

	return result;
}

object subtract(object parameters)
{
	object result;
	TYPE(result) = numberObject;

	if (!allNumbers(parameters))
	{
		TYPE(result) = errorObject;
		ERR(result) = typeError;
	}
	else if (listLength(parameters) == 0)
	{
		TYPE(result) = errorObject;
		ERR(result) = argumentNumberError;
	}
	else if (listLength(parameters) == 1)
	{
		result = minusNum(CAR(parameters));
	}
	else
	{
		result = plusNum(CAR(parameters),
				minusNum(add(CDR(parameters))));
	}

	return result;
}

object multiply(object parameters)
{
	object result;
	TYPE(result) = numberObject;

	if (!allNumbers(parameters))
	{
		TYPE(result) = errorObject;
		ERR(result) = typeError;
	}
	else if (listLength(parameters) == 0)
	{
		result = longlongToNumber(1LL);
	}
	else
	{
		object first, rest;
		first = CAR(parameters);
		rest = multiply(CDR(parameters));

		result = timesNum(first,rest);
	}

	return result;
}

object divide(object parameters)
{
	object result;
	TYPE(result) = numberObject;

	if (!allNumbers(parameters))
	{
		TYPE(result) = errorObject;
		ERR(result) = typeError;
	}
	else if (listLength(parameters) == 0)
	{
		TYPE(result) = errorObject;
		ERR(result) = argumentNumberError;
	}
	else if (listLength(parameters) == 1)
	{
		result = inverseNum(CAR(parameters));
	}
	else
	{
		object check = inverseNum(multiply(CDR(parameters)));
		if (TYPE(check) != errorObject)
		{
			result = timesNum(CAR(parameters),
				inverseNum(multiply(CDR(parameters))));
		}
		else
		{
			result = check;
		}
		result = shortenFractionNum(result);
	}

	return result;
}

object exactToInexact(object parameters)
{
	object result;

	if (listLength(parameters) != 1)
	{
		TYPE(result) = errorObject;
		ERR(result) = argumentNumberError;
	}
	else if (TYPE(CAR(parameters)) != numberObject)
	{
		TYPE(result) = errorObject;
		ERR(result) = typeError;
	}
	else
	{
		result = exactToInexactNum(CAR(parameters));
	}

	return result;
}

object inexactToExact(object parameters)
{
	object result;

	if (listLength(parameters) != 1)
	{
		TYPE(result) = errorObject;
		ERR(result) = argumentNumberError;
	}
	else if (TYPE(CAR(parameters)) != numberObject)
	{
		TYPE(result) = errorObject;
		ERR(result) = typeError;
	}
	else
	{
		result = inexactToExactNum(CAR(parameters));
	}

	return result;
}

object quote(object parameters)
{
	object result;
	if (listLength(parameters) != 1)
	{
		TYPE(result) = errorObject;
		ERR(result) = argumentNumberError;
	}
	else
	{
		result = copyObject(CAR(parameters));
	}
	return result;
}