#include <stdio.h>
#define MAXINPUT 10

typedef enum {IN0 = 0, IN1 = 1, ANDG, ORG, XORG, NANDG, NORG, INVG} GateType;
typedef struct Gate* GatePtr;

struct Gate {
  GateType type;
  GatePtr input1;
  GatePtr input2;
  GatePtr input3;
  GatePtr input4;
};

int initialiseInputArray (GatePtr gateArray[], int count)
{
  int i = 0;
  while (i < count) {
    GatePtr g = malloc(sizeof(struct Gate));
    g->input1 = NULL;
    g->input2 = NULL;
    g->type = IN0;
    gateArray[i] = g;
    ++i;
  }
  gateArray[i] = NULL;
}

int resetInput (GatePtr gateArray[])
{
  /* Must set all inputgates to type IN0 */
  GatePtr g = *gateArray;
  while (g != NULL) {
    g->type = IN0;
    g = *(++gateArray);
  }
}

int applyNextInput (GatePtr gateArray[])
{
  GatePtr g = *gateArray;
  int done = 0;
  int overflow = 1;
  while (!done) {
    if (g->type == IN0) {
      // Add one and return
      g->type = IN1;
      done = 1;
      overflow = 0;
    }
    else {
      // Reset and carry:
      g->type = IN0;
      g = *(++gateArray);
    }
    if (g == NULL)
      done = 1;
  }
  return overflow;
}

int eval(GatePtr gate) {
  if(gate->type == IN0) {
    return 0;
  } else if(gate->type == IN1) {
    return 1;
  } else if(gate->type == ANDG) {
    return eval(gate->input1) & eval(gate->input2)
    & eval(gate->input3)& eval(gate->input4);
  } else if (gate->type == ORG) {
    return eval(gate->input1) | eval(gate->input2);
  } else if(gate->type == XORG) {
    return eval(gate->input1) ^ eval(gate->input2);
  } else if (gate->type == NANDG) {
    return !(eval(gate->input1) & eval(gate->input2));
  } else if (gate->type == NORG) {
    return !(eval(gate->input1) | eval(gate->input2));
  } else if (gate->type == INVG) {
    return !(eval(gate->input1));
  }
}

void printTruthTable(GatePtr inputGates[], int results[]) {
  GatePtr gate = *inputGates;
  while (gate != NULL) {
    if(gate->type == IN0) {
      printf("|\t0\t|");
    } else if (gate->type == IN1) {
       printf("|\t1\t|");
    }
    gate = *(++inputGates);
  }
  int * result = results;
  while(*result != -1) {
    printf("|\t%d\t|", *result);
    result = ++results;
  }
  printf("\n");
}

int main(void) {
  GatePtr inputGates[MAXINPUT+1];
  initialiseInputArray (inputGates, 4);

  GatePtr andgate = malloc(sizeof(struct Gate));
  andgate->type = ANDG;
  andgate->input1 = inputGates[0];
  andgate->input2 = inputGates[1];
  andgate->input3 = inputGates[2];
  andgate->input4 = inputGates[3];
  resetInput(inputGates);
  do {
    int out = eval(andgate);
    int results[4] = {out, -1};
    printTruthTable(inputGates, results);
  } while (!applyNextInput(inputGates));

  return 0;
}