#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)
	{
		NUM(result) = 0LL;
	}
	else
	{
		object first, rest;
		first = CAR(parameters);
		rest = add(CDR(parameters));

		NUM(result) = NUM(first) + NUM(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)
	{
		NUM(result) = -NUM(CAR(parameters));
	}
	else
	{
		NUM(result) = NUM(CAR(parameters)) - NUM(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)
	{
		NUM(result) = 1LL;
	}
	else
	{
		object first, rest;
		first = CAR(parameters);
		rest = multiply(CDR(parameters));

		NUM(result) = NUM(first) * NUM(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)
	{
		if (NUM(CAR(parameters)) != 0)
		{
			NUM(result) = 1/NUM(CAR(parameters));
		}
		else
		{
			TYPE(result) = errorObject;
			ERR(result) = divisionByZeroError;
		}
	}
	else
	{
		if (NUM(multiply(CDR(parameters))) != 0)
		{
			NUM(result) = NUM(CAR(parameters))/NUM(multiply(CDR(parameters)));
		}
		else
		{
			TYPE(result) = errorObject;
			ERR(result) = divisionByZeroError;
		}
	}

	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;
}