A Really Simple Phonebook in pure C

phonebook.c

/*
 * Phonebook
 * Mohammad Amin Sameti (951019034)
 */

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

typedef struct {
	char first_name[20];
	char last_name[20];
	char phone[20];
} Contact;

Contact contacts[60];
int contacts_count;

void add_contact() {
	Contact *contact = contacts + contacts_count;

	puts("Enter First Name:");
	scanf("%s", &contact->first_name);

	puts("Enter Last Name: ");
	scanf("%s", &contact->last_name);

	puts("Enter Phone Number: ");
	scanf("%s", &contact->phone);

	puts("Contact Saved.");
	contacts_count++;
}

void edit_contact(int index) {
	Contact *contact = contacts + index;

	if (index >= contacts_count || index < 0) {
		puts("ERROR: Invalid Contact ID");
		return;
	}

	printf("Current First Name: %s\n", contact->first_name);
	puts("Enter First Name:");
	scanf("%s", &contact->first_name);

	printf("Current Last Name: %s\n", contact->last_name);
	puts("Enter Last Name: ");
	scanf("%s", &contact->last_name);

	printf("Current Phone Number: %s\n", contact->phone);
	puts("Enter Phone Number: ");
	scanf("%s", &contact->phone);


	puts("Contact Edited.");
}

void delete_contact(int index) {
	Contact *contact, *last;

	if (index >= contacts_count || index < 0) {
		puts("ERROR: Invalid Contact ID");
		return;
	}

	contact = contacts + index;
	last = contacts + contacts_count - 1;

	strcpy(contact->first_name, last->first_name);
	strcpy(contact->last_name, last->last_name);
	strcpy(contact->phone, last->phone);

	contacts_count--;
}

void show_contacts() {
	int i;
	Contact *contact;

	puts("ID | Full Name | Phone Number");
	for (i = 0; i < contacts_count; i++) {
		contact = contacts + i;

		printf("%i | %s %s | %s\n", i + 1, contact->first_name, contact->last_name, contact->phone);
	}
}

char read_string(char *s, FILE *file) {
	char i, c;

	i = 0;
	s[0] = 0;

	while (1) {
		c = fgetc(file);

		if (c == 0) {
			s[i] = 0;
			return i;
		} else if (c == EOF) {
			return -1;
		} else {
			s[i] = c;
			i++;
		}
	}
}

void load_contacts() {
	char r, *s;
	FILE *file = fopen("contacts.txt", "r");

	if (!file)
		return;

	contacts_count = 0;

	while (1) {
		s = contacts[contacts_count].first_name;

		r = read_string(s, file);

		if (r < 0)
			break;

		s = contacts[contacts_count].last_name;
		read_string(s, file);

		s = contacts[contacts_count].phone;
		read_string(s, file);

		contacts_count++;
	}

	fclose(file);
}

void save_contacts() {
	int i;
	Contact *contact;
	FILE *file = fopen("contacts.txt", "w");

	if (!file)
		return;

	for (i = 0; i < contacts_count; i++) {
		contact = contacts + i;

		fputs(contact->first_name, file);
		fputc(0, file);

		fputs(contact->last_name, file);
		fputc(0, file);

		fputs(contact->phone, file);
		fputc(0, file);
	}

	fclose(file);
}

int get_command() {
	char c;

	puts("Enter Command:");
	puts("    a) Add");
	puts("    e) Edit");
	puts("    d) Delete");
	puts("    s) Show");
	puts("    q) Quit");
	printf("\n: ");

	scanf("%s", &c);

	switch (c) {
		case 'a':
			add_contact();
			break;

		case 'e':
			printf("Enter Contact ID: ");
			scanf("%i", &c);
			edit_contact(c - 1);
			break;

		case 'd':
			printf("Enter Contact ID: ");
			scanf("%i", &c);
			delete_contact(c - 1);
			break;

		case 's':
			show_contacts();
			break;

		case 'q':
			puts("Goodbye");
			return 0;

		default:
			puts("ERROR: Invalid Command");
			break;
	}

	puts("");
	return 1;
}

int main() {
	load_contacts();

	while (get_command());

	save_contacts();

	return 0;
}