/* Rebecca Dreezer
Sample Assignment 3B
Adaptation of Dr Farmer's code */

#include <stdio.h>
#include <stdbool.h>
#include <stdlib.h>

#define MAX_LENGTH 10

typedef int nat;

typedef struct {
  char data[20];
  nat id;
} element;

typedef struct {
  element contents[MAX_LENGTH];
  nat length;
  nat front;
  nat back;
} queue_record;

typedef queue_record * queue;

/* Primitive operators */

queue bottom() {
  queue newQ = malloc(sizeof(queue_record));
  newQ->length = 0;
  newQ->front = 0;
  newQ->back = 0;
  return newQ;
}

nat length(queue q) {
	return q->length;
}

element front(queue q) {
  nat queue_len = q->length;
  if (queue_len == 0) {
    printf("\nError: the queue is empty!\n");
    element e1 = {"/", 0};
    return e1;
  }
  else {
	return q->contents[q->front];
  }
}

void pop(queue q) {
  nat queue_len = q->length;
  if (queue_len == 0) {
    printf("Error in pop: queue is empty.\n");
    return;
  }
  else {
    q->front = q->front + 1;
    q->length = queue_len - 1;
    return;
  }
}

void push(element e, queue q) {
  nat queue_len = q->length;
  if (queue_len == MAX_LENGTH) {
    printf("Error in push: queue is full.\n");
  }
  else {
    q->back = q->back + 1;
    q->contents[queue_len] = e;
    q->length = queue_len + 1;
  }
  return;
}

void print(queue q) {
  nat queue_len = q->length;
  nat i;
  nat j = q->front;
  printf("queue contents: [");
  for (i = 0; i < queue_len; i++) {
    if (i + 1 == queue_len)
      printf("%s %d", q->contents[j].data, q->contents[j].id);
    else
      printf("%s %d,", q->contents[j].data, q->contents[j].id);
    j++;
  }
  printf("].\n");
}

void dismantle(queue q) {
  free(q);
  return;
}

/* Derived Operators */

bool is_empty (queue q) {
  return length(q) == 0;
}

void reset (queue q) {
  while (!is_empty(q)) {
    pop(q);
  }
}

/* Main function */

int main() {

  element e0 = {"a", 1};
  element e1 = {"b", 2};
  element e2 = {"c", 1};
  element e3 = {"d", 2};
  element e4 = {"e", 1};
  element e5 = {"f", 2};
  element e6 = {"g", 1};
  element e7 = {"h", 2};
  element e8 = {"i", 1};
  element e9 = {"j", 2};

  queue q = bottom();
  print(q);
  front(q);
  pop(q);
  push(e0,q);
  print(q);

  element e = front(q);

  printf("Front is [%s %d].\n", e.data, e.id);
  push(e1,q);
  print(q);
  push(e2,q);
  print(q);
  push(e3,q);
  print(q);
  push(e4,q);
  print(q);
  push(e5,q);
  print(q);
  push(e6,q);
  print(q);
  push(e7,q);
  print(q);
  push(e8,q);
  print(q);
  push(e9,q);
  print(q);
  push(e0,q);
  print(q);

  pop(q);
  pop(q);
  print(q);

  reset(q);
  print(q);
  dismantle(q);
  print(q);
  return 0;

}