#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "util.h"

object apply(object function, object parameters);

object eval(object input)
{
	object result;

	if (TYPE(input) == nilObject || TYPE(input) == numberObject ||
			TYPE(input) == errorObject)
		result = input;
	else if (TYPE(input) == symbolObject)
	{
		if (!strcmp(SYM(input), "+") || !strcmp(SYM(input), "-") ||
		    !strcmp(SYM(input), "*") || !strcmp(SYM(input), "/"))
		{
			result = input;
		}
		else
		{
			deleteObject(input);
			TYPE(result) = errorObject;
			ERR(result) = unrecognizedSymbolError;
		}
	}
	else if (TYPE(input) == consObject)
	{
		if (!properList(input))
		{
			deleteObject(input);
			TYPE(result) = errorObject;
			ERR(result) = improperListError;
		}

		object *currentCell = &input;
		int noErrors = 1;
		while (TYPE(*currentCell) != nilObject)
		{
			CAR(*currentCell) = eval(CAR(*currentCell));

			if (TYPE(CAR(*currentCell)) == errorObject)
			{
				noErrors = 0;
				TYPE(result) = errorObject;
				ERR(result) = ERR(CAR(*currentCell));
				break;
			}
			currentCell = &CDR(*currentCell);
		}

		if (noErrors)
		{
			result = apply(CAR(input), CDR(input));
		}
		deleteObject(input);
	}

	return result;
}

object add(object parameters);
object subtract(object parameters);
object multiply(object parameters);
object divide(object parameters);

object apply(object function, object parameters)
{
	object result;

	if (TYPE(function) != symbolObject)
	{
		deleteObject(function);
		TYPE(result) = errorObject;
		ERR(result) = notApplicableError;
	}
	/* TODO Ово налажење ће се касније извршавати кроз табелу симбола */
	else if (!strcmp(SYM(function), "+"))
	{
		result = add(parameters);
	}
	else if (!strcmp(SYM(function), "-"))
	{
		result = subtract(parameters);
	}
	else if (!strcmp(SYM(function), "*"))
	{
		result = multiply(parameters);
	}
	else if (!strcmp(SYM(function), "/"))
	{
		result = divide(parameters);
	}
	else
	{
		deleteObject(function);
		TYPE(result) = errorObject;
		ERR(result) = improperListError;
	}

	return result;
}

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(add(CDR(parameters))) != 0)
		{
			NUM(result) = NUM(CAR(parameters))/NUM(add(CDR(parameters)));
		}
		else
		{
			TYPE(result) = errorObject;
			ERR(result) = divisionByZeroError;
		}
	}

	return result;
}