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

#define BUFFER_SIZE 1024
#define NUMBER_SIZE 32
#define PATH_SIZE 1024

struct _Cvor;
typedef struct _Cvor *Pos;
typedef struct _Cvor
{
	int El;
	Pos Next;
}_CVOR;

int Push(Pos, int);
int Pop(Pos, int *);
int Calc_Posfix(char *, int *);
int Calculate(int, int,char, int *);
int ReadFromFile(char *, char *, int);

int main(int argc, char *argv[])
{
	int error_code = 0;
	int result = 0;
	char ime_dat[PATH_SIZE]={0};

	printf(" %c", 201);
	for(int i = 0; i< 39; i++)
		printf("%c", 205);
	printf("%c", 187);
	printf("\n %c\t***\t   Vjezba 7\t    ***\t %c", 186,186);
	printf("\n %c\t*** Racunanje posfix izraza ***\t %c\n",186,186);
	printf(" %c", 200);
	for(int i = 0; i< 39; i++)
		printf("%c", 205);
	printf("%c", 188);
	printf("\n  Unesite ime datoteke s posfix izrazom:\n\t\t");
	scanf_s(" %s", ime_dat, PATH_SIZE);

	if(Calc_Posfix(ime_dat, &result) == 0)
		printf("\n\n\n\tRezultat je : %d\n\n", result);
	else
		printf("\n\n\nGreska u izrazu!\n\n");
}
int Calc_Posfix(char *ime_dat, int *result)
{
	int error_code = 0;
	char *data = NULL;
	char *fdata = NULL;
	Pos head = NULL;

	data = (char*)malloc(sizeof(char) * BUFFER_SIZE);
	if(data == NULL)
	{
		printf("\nGRESKA!!!\nMemorija nije alocirana!");
		error_code = -2;
	}
	else
	{
		fdata = data;
		memset(fdata, '\0', BUFFER_SIZE);
		if(!ReadFromFile(ime_dat, data, BUFFER_SIZE))
		{
			head=(Pos)malloc(sizeof(_CVOR));
			if(head == NULL)
			{
				printf("\nGRESKA!!!\nMemorija nije alocirana!");
				error_code = -1;
			}
			else
			{
				head->Next = NULL;
				char *buff;
				buff = (char*)malloc(sizeof(char) * NUMBER_SIZE);
				if(buff == NULL)
				{
					printf("\nGRESKA!!!\nMemorija nije alocirana!");
					error_code = -2;
				}
				else
				{
					memset(buff, '\0', NUMBER_SIZE);
					sscanf_s(fdata, " %s", buff, NUMBER_SIZE);
					do
					{
						if(isdigit(*buff))
						{//operand - Push
							char operand[NUMBER_SIZE] = {0};
							strcpy_s(operand,NUMBER_SIZE, buff);
							error_code = Push(head, atoi(operand));
							if(error_code != 0)
								break;
						}
						else
						{//operacija - Pop x2 AND Calculate AND Push
							int x = 0;
							int y = 0;
							int r = 0;

							error_code = Pop(head,&y);
							if(error_code != 0)
								break;
							error_code = Pop(head,&x);
							if(error_code != 0)
								break;
							error_code = Calculate(x,y,*buff,&r);
							if(error_code != 0)
								break;
							error_code = Push(head, r);
							if(error_code != 0)
								break;
						}
						memset(buff, '\0', NUMBER_SIZE);
						if(strlen(fdata) > 0)
						{
							fdata = strchr(fdata+1, ' ');
							if(fdata != NULL)
								sscanf_s(fdata, "%s", buff, NUMBER_SIZE);
						}
					}while(strlen(buff) > 0);
				}
				free(buff);
			}
		}
	}
	printf("\n\n\t\tPosfix izraz :\n");
	printf("\t%s", data);
	free(data);
	if(error_code == 0)
		*result = head->Next->El;
	else
		*result = 0;
	free(head->Next);
	free(head);
	return error_code;
}
int Push(Pos P, int x)
{
	int error_code = 0;
	Pos q;

	q=(Pos)malloc(sizeof(_CVOR));
	if(q == 0)
	{
		printf("\nGRESKA!!!\nMemorija nije alocirana!");
		error_code = -1;
	}
	else
	{
		q->El = x;
		q->Next = P->Next;
		P->Next = q;
	}
	return error_code;
}
int Pop(Pos P, int *x)
{
	int error_code = 0;
	Pos tmp;

	if(P->Next == NULL)
	{
		printf("\nGRESKA!!!\nStog je prazan!");
		error_code = -1;
	}
	else
	{
		tmp = P->Next;
		P->Next = tmp->Next;
		*x = tmp->El;
		free(tmp);
	}
	return error_code;
}
int Calculate(int x, int y,char op, int *r)
{
	int error_code = 0;
	switch(op)
	{
	case '+':
		*r = x+y;
		break;
	case '-':
		*r = x-y;
		break;
	case '*':
		*r = x*y;
		break;
	case '/':
		if(y == 0)
		{
			printf("\nGRESKA!!!\nDijeljenje s nulom!\n");
			error_code = -2;
		}
		else
			*r = x/y;
		break;
	default:
		printf("\nGRESKA!!!\nOperacija nije definirana!\n");
		error_code = -1;
	}
	return error_code;
}
int ReadFromFile(char *ime_dat, char *Data, int Len)
{
	int error_code = 0;
	FILE *fp;

	fopen_s(&fp, ime_dat, "r");
	if(fp == NULL)
	{
		printf("\nGRESKA!!!\nDatoteka %s nije otvorena!\n", ime_dat);
		error_code = -1;
	}
	else
	{
		if(0 >= fread(Data, sizeof(char), Len, fp))
			error_code = -2;
		fclose(fp);
	}
	return error_code;
}