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

	#define STACK_SIZE 10
	#define EMPTY 'E'

	typedef struct stack {
		char letters[STACK_SIZE];
		int top;
	} stack;

	// Function Prototypes
	stack *createStack();
	int isEmpty(stack *s);
	int isFull(stack *s);
	char peek(stack *s);
	char pop(stack *s);
	int push(stack *s, char c);
	void printStack(stack *s);
	void printChar(char c);
	void printOptions();

	// Returns initialized stack
	stack *createStack() {
		stack *s = malloc(sizeof(stack));
		s->top = -1;
		return s;
	}

	// Returns 1 if stack is NULL or is empty
	int isEmpty(stack *s) { return (!s || s->top == -1); }

	// Returns 1 if stack is not NULL and is full, otherwise returns 0
	int isFull(stack *s) { return (s && (s->top == STACK_SIZE - 1)); }

	// Return - WITHOUT removing - character from top of stack
	char peek(stack *s) {
		if (isEmpty(s))
			return EMPTY;

		return s->letters[s->top];
	}

	// Return/ remove character from top of stack
	char pop(stack *s) {
		if (isEmpty(s))
			return EMPTY;

		char letter = s->letters[(s->top)--];

		return letter;
	}

	// Push character to top of stack
	int push(stack *s, char c) {
		if (!s || isFull(s))
			return 0;

		s->letters[++(s->top)] = c;
		return 1;
	}

	// Empty all elements in stack
	void clearStack(stack *s) {
		while (!isEmpty(s))
			pop(s);
	}

	// Prints stack to screen
	void printStack(stack *s) {
		if (isEmpty(s)) {
			printf("Stack is empty\n");
			return;
		}
		printf("(top)\n");

		for (int i = s->top; i >= 0; i--) {
			printf("%c\n", s->letters[i]);
		}
		printf("(bottom)\n");
	}

	// Print character
	void printChar(char c) {
		if (c == EMPTY)
			printf("EMPTY\n");
		else
			printf("%c\n", c);
	}

	// Print options menu
	void printOptions() {
		printf("1) Push\n");
		printf("2) Pop\n");
		printf("3) Peek\n");
		printf("4) Print Stack\n");
		printf("5) Clear Stack\n");
		printf("6) Quit\n");
		printf("\n:");
	}

	int main(void) {
		stack *s = createStack();

		int choice = 0;
		char c;

		while (choice != 6) {
			printOptions();
			scanf("%d", &choice);

			switch (choice) {

			case 1: // Push
				printf("Type a lowercase letter to add to stack:\n");
				scanf(" %c", &c);
				if (push(s, c))
					printf("%c added to stack\n", c);
				else
					printf("Failed to add %c to stack\n", c);
				break;

			case 2: // Pop
				c = pop(s);
				printf("Popped: ");
				printChar(c);
				break;

			case 3: // Peek
				c = peek(s);
				printf("Peeked: ");
				printChar(c);
				break;

			case 4: // Print Stack
				printStack(s);
				break;

			case 5: // Clear Stack
				clearStack(s);
				printf("Stack is now empty\n");
				break;

			default:
				break;
			}
			printf("\n");
		}

		// Free Memory
		free(s);

		return 0;
	}