simple_crud.c

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

static const char store_file[] = "./todo_data.bin";
static const char store_file_tmp[] = "./todo_data.bin.tmp";

struct todo {
	char data[255];
};

static int menu(void)
{
	int ret, n;

	// printf("\ec");
	printf("---- Welcome to the TODO List program ----\n");
	printf("1. Add.\n");
	printf("2. Update.\n");
	printf("3. Delete\n");
	printf("4. Show\n");
	printf("5. Exit\n");
	printf("======================================\n");
	printf("Enter the option: ");

	ret = scanf("%d", &n);
	if (ret != 1) {
		return -1;
	}

	while (getchar() != '\n') {
		// Do nothing.
	}

	return n;
}

static int handle_add(FILE *h)
{
	struct todo d;

	memset(&d, 0, sizeof(d));

	printf("Enter the todo list: ");
	if (!fgets(d.data, sizeof(d.data), stdin)) {
		return -1;
	}

	fwrite(&d, sizeof(d), 1, h);
	return 0;
}

static unsigned show_todo_list(FILE *h)
{
	struct todo d;
	size_t ret;
	unsigned i;

	rewind(h);
	printf("========================================\n");
	printf("TODO List:\n");
	i = 0;
	while (1) {
		ret = fread(&d, sizeof(d), 1, h);
		if (ret == 0) {
			break;
		}
		printf("  %u. %s\n", ++i, d.data);
	}
	printf("========================================\n");
	return i;
}

static int handle_show(FILE *h)
{
	show_todo_list(h);
	printf("Press enter to continue!");
	getchar();
	return 0;
}

static int handle_delete(FILE *h)
{
	unsigned n, i, choice;
	FILE *th;
	int ret;

	n = show_todo_list(h);
	printf("Which list do you want to delete? Enter the num: ");
	ret = scanf("%u", &choice);
	if (ret != 1) {
		return -1;
	}

	if (choice == 0 || choice > n) {
		printf("Invalid number!\n");
		return 0;
	}

	th = fopen(store_file_tmp, "wb");
	if (!th) {
		perror("Failed to open the store_file_tmp");
		return -1;
	}

	rewind(h);
	for (i = 1; i <= n; i++) {
		struct todo d;

		fread(&d, sizeof(d), 1, h);
		if (i == choice) {
			continue;
		}
		fwrite(&d, sizeof(d), 1, th);
	}
	fclose(th);
	remove(store_file);
	rename(store_file_tmp, store_file);
	return 0;
}


static int handle_input_menu(int n, FILE *h)
{
	switch (n) {
	case 1:
		return handle_add(h);
	// case 2:
	// 	return handle_update();
	case 3:
		return handle_delete(h);
	case 4:
		return handle_show(h);
	case 5:
		/* For exit. */
		return 1;
	default:
		printf("Invalid menu %d\n", n);
		break;
	}

	return 0;
}

int main(void)
{
	int ret, n;
	FILE *h;

	do {
		h = fopen(store_file, "ab+");
		if (!h) {
			perror("Failed to open the store_file");
			return 1;
		}

		n = menu();
		ret = handle_input_menu(n, h);
		if (ret != 0) {
			break;
		}

		fclose(h);
	} while (n != -1);
	return 0;
}