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

#include "util.h"
#include "symtable.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 (symbolExists(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 apply(object function, object parameters)
{
	object result;

	if (TYPE(function) != symbolObject)
	{
		deleteObject(function);
		TYPE(result) = errorObject;
		ERR(result) = notApplicableError;
	}
	else if (symbolExists(SYM(function)))
	{
		object(*f)();
		if ((f = internalFunction(SYM(function))) != NULL)
		{
			result = f(parameters);
		}
	}
	else
	{
		deleteObject(function);
		TYPE(result) = errorObject;
		ERR(result) = unrecognizedSymbolError;
	}

	return result;
}