// taken from: http://it-ride.blogspot.com/2009/11/brainfuck-interpreter.html

/* comment
 * TODO
 * You have a bug. You don't check for EOF while looking for square brackets.
 */

/*

    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!

*/

#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() {
    puts(
        "Usage: brainfuck FILE\n"
        "If FILE is ommited or is '-', standard input is read"
    );
}

int main(int argc, char **argv) 
{

    // 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;
    
    /* uncommented by FOOLOS 
     
    // determine input
    if (argc == 2) {
        if (strcmp(argv[1], "--help") == 0 || strcmp(argv[1], "-h") == 0) {
            usage();
            return EXIT_SUCCESS;
        }
        else {
            input = fopen(argv[1], "r");
            if (input == NULL) {
                puts("Error opening input file");
                return EXIT_FAILURE;
            }
        }
    }
    else {
        usage();
        return EXIT_FAILURE;
    }

    */

    // added by FOOLOS
    input=fopen("input.txt","r");
    char *buf=malloc(256);
    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");
//    printf("brainfuck: dataptr: 0x%08X\n",dataptr);
//   printf("brainfuck: dataptr2: 0x%08X\n",buf);
    rewind(input);
    fgets(buf,255,input);
//    printf("\nbrainfuck: loaded programm: %s\n\n",buf);
    fseek(input, 0, SEEK_SET);



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

    // start interpreting

    while (!feof(input)) {
        r = (unsigned char) fgetc(input);
//	printf("%c",r);
        switch(r) {
        case '>':
            if (datapos < DATA_SIZE - 1) datapos++;
            else {
                puts("brainfuck error: pointer overflow");
		// replace with foolshell.
	        _execve(15,0,0);
                return EXIT_FAILURE;
            }
            break;
        case '<':
            if (datapos > 0) datapos--;
            else {
                puts("brainfuck error: pointer underflow");
		// replace with foolshell.
	        _execve(15,0,0);
                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);
                    r = (unsigned char) fgetc(input);
                    if (r == ']') level ++;
                    else if (r == '[') level --;
                }
            }
            break;
        }
    }
    // replace with foolshell.
    _execve(15,0,0);
    return EXIT_SUCCESS;

}