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


//#define DEBUG

#define MVR     '>'
#define MVL     '<'
#define INC     '+'
#define DEC     '-'
#define OUT     '.'
#define RIN     ','
#define OLP     '['
#define CLP     ']'


char* readall(FILE* ifp);
void clean(char* buffer);


/*
* The 'stack' will store data from the BF program
* 'sp' points to current "selected" "variable"
* The 'jumpstack' keeps track of `[` to track loops
* 'ip' points to instruction in the program
*/
unsigned char stack[200] = { 0 };
int sp = 0;

unsigned char jumpstack[50];
int ip = 0;

char op;



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

    if ( argc != 2 ) {
        printf("Usage: %s inputfile\n", argv[0]);
        return 1;
    }

    char* fname = argv[1];
    FILE*   ifp;
    char* buffer;

    /*
     * Check if file exists
     * Exit if not
     */
    if ( access( fname, F_OK ) == -1 ) {
        printf("No such file: %s\n", fname);
        return 1;
    } else if ( access( fname, R_OK ) == -1 ) {
        printf("You do not have permission to read file: %s\n", fname);
        return 1;
    }

    ifp = fopen(fname, "r");

    if ( !( buffer = readall(ifp) ) ) {
        printf("Cannot open file");
    }

    fclose(ifp);

    clean(buffer);

    #ifdef DEBUG
        printf("Contents of file:\n%s\n", buffer);
    #endif



    /*
     * Main interpreter loop
     */
    for(;;){

        /*
         * Define exit points for the interpreter
         */

        op = buffer[ip];
        if ( !op ) return 0;

        if ( sp < 0 ) {
            printf("Stackpointer was non-zero at character %d\n", ip);
            return 1;
        }


        switch ( op ) {
            case MVR:
                sp++;
                ip++;
                break;
            case MVL:
                sp--;
                ip++;
                break;
            case INC:
                stack[sp]++;
                ip++;
                break;
            case DEC:
                stack[sp]--;
                ip++;
                break;
            case OUT:
                putchar(stack[sp]);
                ip++;
                break;
            case RIN:
                break;
            case OLP:
                break;
            case CLP:
                break;
            default:
                printf("Unknown instruction: %c", op);
                return 1;
        }



    }

    free(buffer);

    return 0;
}



char* readall(FILE* ifp) {
    /*
    * Read stream 'ifp' to 'buffer'
    * Returns pointer to buffer, 1 on fail
    */

    char* buffer;

    fseek(ifp, 0L, SEEK_END);
    size_t fsize = ftell(ifp);
    rewind(ifp);

    buffer = malloc(fsize);
    /* Check for memory error */
    if ( buffer == NULL )
    return NULL;

    fread(buffer, 1, fsize, ifp);

    return buffer;
}



void clean(char* buffer) {
    /*
     * Returns stripped string
     * Used characters are: ><+-.,[]
     */

    int i, bp;
    char c;

    bp = 0;
    for ( i=0; buffer[i]; i++ ) {
        c = buffer[i];

        if ( c == MVR ||
             c == MVL ||
             c == INC ||
             c == DEC ||
             c == OUT ||
             c == RIN ||
             c == OLP ||
             c == CLP ) {
                 buffer[bp] = c;
                 bp += 1;
             }

    }
    buffer[bp] = 0x00;

    buffer = realloc( buffer, strlen(buffer)+1 );
}