/*
    A brainfuck intepreter written in C, complete with error checking so you
    don't hurt yourself while, uh, brainfucking. Nothing really special about
    the implementation and it is probably very poor performance-wise.
    
    Author: Felix Oghină
    License: (brain)fuck licenses!


*/

// taken from: http://it-ride.blogspot.com/2009/11/brainfuck-interpreter.html
// and adapted for FoolOs by Miguel
//
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// by brainfuck standards (doesn't that sound funny?), the data pointer has
// 3,000 bytes at its disposal, but I hate hard-coding such stuff.

// FOOLOS: decreased to 3000 (from 30.000)
#define DATA_SIZE 3000

void usage(char *progname)
{
    printf("Usage: %s [FILE]\n",progname);
}

int main(int argc, char **argv) 
{
    puts("\n\nbrainfuck: Welcome to the BRAINFUCK INTERPRETER by Felix Oghina");
    puts("brainfuck: Licensed under the (brain)fuck licenses!"); 
    puts("brainfuck: Adapted & Compiled for FoolOS by Miguel");

    // used by the bf program
    unsigned char *dataptr = malloc(sizeof(char) * DATA_SIZE);

    // position of the data pointer
    unsigned int datapos = 0;

    // input file
    FILE *input;

    // level - deepness of brackets
    // i - uh, you need explanation for this one?
    unsigned int level, i;

    // we will read chars from the input into r
    unsigned char r;
     
    // check argument count
    if(argc!=2)
    {
        usage(argv[0]);
        return EXIT_FAILURE;
    }

    // open brainfuck source
    input = fopen(argv[1], "r");

    if (input == NULL)
    {
	puts("Error opening input file");
	return EXIT_FAILURE;
    }

    // zero the data pointer
    for (i=0; i < DATA_SIZE; i++) {
        dataptr[i] = 0;
    }

    // start interpreting
    while (1) {

        r = (unsigned char) fgetc(input);

        switch(r) {
	case 'X': 
	    puts("END!");
	    return 0;
        case '>':
            if (datapos < DATA_SIZE - 1) datapos++;
            else {
                puts("brainfuck error: pointer overflow");
                return EXIT_FAILURE;
            }
            break;
        case '<':
            if (datapos > 0) datapos--;
            else {
                puts("brainfuck error: pointer underflow");
                return EXIT_FAILURE;
            }
            break;
        case '+':
            dataptr[datapos]++;
            break;
        case '-':
            dataptr[datapos]--;
            break;
        case '.':
            putchar(dataptr[datapos]);
            break;
        case ',':
            dataptr[datapos] = getchar();
            break;
        case '[':
            if (dataptr[datapos] == 0) {
                level = 1;
                while (level != 0) {
                    r = (unsigned char) fgetc(input);
                    if (r == '[') level ++;
                    else if (r == ']') level --;
                }
            }
            break;
        case ']':
            if (dataptr[datapos] != 0) {
                level = 1;
                while (level != 0) {
                    //fseek(input, -2, SEEK_CUR);
		    _lseek(3,-2,SEEK_CUR);
                    r = (unsigned char) fgetc(input);
                    if (r == ']') level ++;
                    else if (r == '[') level --;
                }
            }
            break;
        }
    }

    return EXIT_SUCCESS;
}