/* Copyright (C) 2014 by Alexandru Cojocaru */

/* This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>. */

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

typedef struct unit unit;
struct unit {
  int q1;
  char s1, s2;
  char d;
  int q2;
  unit *next;
};

static unit *head;
static char tape[100];

static unit *
newunit (char *s)
{
  unit *u = malloc (sizeof (*u));
  assert (u);
  u->q1 = s[0]-'0';
  u->s1 = s[1];
  u->s2 = s[2];
  u->d = s[3];
  if (s[4] == '-')
    u->q2 = -1;
  else
    u->q2 = s[4]-'0';
  u->next = NULL;
  return u;
}

static unit *
nextunit (unit *head, int ti, int q1)
{
  unit *p = head;
  while (p) {
    if (p->q1 == q1 &&
	p->s1 == tape[ti])
      return p;
    p = p->next;
  }
  assert (0);
}

static void
run (unit *head)
{
  unit *p;
  int q1 = 0;
  int ti = 0;
  while (q1 != -1) {
    p = nextunit (head, ti, q1);
    tape[ti] = p->s2;
    q1 = p->q2;
    ti += p->d == 'R' ? 1 : -1;
    assert (ti >= 0 && ti < sizeof (tape)/sizeof (tape[0]));
  }
}

int
main (void)
{
  strcpy (tape, "111+11111_");
  printf ("%s\n", tape);

  unit *p;
  head = newunit ("011R0");
  p = head;
  p->next = newunit ("0+1R1");
  p = p->next;
  p->next = newunit ("111R1");
  p = p->next;
  p->next = newunit ("1__L2");
  p = p->next;
  p->next = newunit ("21_L-");

  run (head);
  printf ("%s\n", tape);
  return 0;
}