// Queue.c

#include <stdio.h>
#include <stdlib.h>
#include "Queue.h"

typedef struct node {
    Item item;
    struct node *next;
} Node;

struct queue {
    Node *head;   // front of queue
    Node *tail;   // end of queue
    int size;
};

// Helper to create a new node
static Node *newNode(Item it) {
    Node *n = malloc(sizeof(Node));
    
    n->item = it;
    n->next = NULL;
    return n;
}

Queue QueueNew(void) {
    Queue q = malloc(sizeof(struct queue));

    q->head = NULL;
    q->tail = NULL;
    q->size = 0;
    return q;
}

void QueueFree(Queue q) {
    Node *curr = q->head;
    while (curr != NULL) {
        Node *temp = curr;
        curr = curr->next;
        free(temp);
    }
    free(q);
}

void QueueEnqueue(Queue q, Item it) {
    Node *n = newNode(it);

    if (q->tail == NULL) {
        q->head = n;
        q->tail = n;
    } else {
        q->tail->next = n;
        q->tail = n;
    }

    q->size++;
}

Item QueueDequeue(Queue q) {
    Node *oldHead = q->head;
    Item it = oldHead->item;

    q->head = oldHead->next;

    if (q->head == NULL) {
        q->tail = NULL;
    }

    free(oldHead);
    q->size--;

    return it;
}

int QueueSize(Queue q) {
    return q->size;
}

Item QueuePeek(Queue q) {
    return q->head->item;
}