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

// Berkeley DB 1.85
#include <db.h>

#define DATABASE_NAME "./database.db"
#define MODE 0600

#define USERNAME_LENGTH 20
#define FULLNAME_LENGTH 50

typedef struct {
	char username[USERNAME_LENGTH];
	char fullname[FULLNAME_LENGTH];
	int  age;
} user_type;

void
insert(DB *database)
{
	user_type users[] = {
		{ "datengott", "Thomas Schmucker", 44 },
		{ "user1", "Sabine Müller", 23 },
		{ "sql-user", "SQL Database User", -1 }
	};

	for ( int i = 0; i != 3; ++i ) {
		DBT data = { .data = &users[i], .size = sizeof(users[i]) };
		DBT key  = { .data = users[i].username, .size = strlen(users[i].username) };

		int error = database->put(database, &key, &data, 0);
		if ( error ) {
			(void) fprintf(stderr, "Datensatz konnte nicht eingefügt werden!\n");
		}
	}
}

void
update(DB *database, const char *username, int new_age)
{
	DBT key = { .data = (void *) username, .size = strlen(username) };
	DBT old_data;

	int error = database->get(database, &key, &old_data, 0);
	if ( error ) {
		(void) fprintf(stderr, "Datensatz %s nicht gefunden!\n", username);
		return;
	}

	// update
	user_type user;
	memcpy(&user, old_data.data, sizeof user);
	user.age = new_age;

	DBT new_data = {
		.data = &user,
		.size = sizeof user
	};

	error = database->put(database, &key, &new_data, 0);

	if ( error ) {
		(void) fprintf(stderr, "Datensatz %s wurde nicht aktualisiert\n", username);
	}
}

void
erase(DB *database, const char *username)
{
	DBT key = { .data = (void *) username, .size = strlen(username) };

	int error = database->del(database, &key, 0);
	if ( error ) {
		(void) fprintf(stderr, "Datensatz %s wurde nicht gelöscht\n", username);
	}
}

void
lookup(DB *database, const char *username)
{
	DBT key = { .data = (void *) username, .size = strlen(username) };
	DBT data;

	int error = database->get(database, &key, &data, 0);
	if ( !error ) {
		user_type *user = data.data;
		printf("%.*s -> %s (%d)\n", (int) key.size, (char *) key.data, user->fullname, user->age);
	}
}

void
list(DB *database)
{
	DBT key;
	DBT data;

	int error = database->seq(database, &key, &data, R_FIRST);
	while ( !error ) {
		user_type *user = data.data;
		printf("%.*s -> %s (%d)\n", (int) key.size, (char *) key.data, user->fullname, user->age);

		error = database->seq(database, &key, &data, R_NEXT);
	}
}

int
main(void)
{
	DB *database = dbopen(DATABASE_NAME, O_RDWR | O_CREAT, MODE, DB_BTREE, NULL);
	if ( database == NULL ) {
		(void) fprintf(stderr, "Datenbank konnte nicht geöffnet werden\n");
		return EXIT_FAILURE;
	}

	insert(database);

	lookup(database, "user1");

	erase(database, "user1");

	update(database, "datengott", 50);

	list(database);

	database->close(database);

	return EXIT_SUCCESS;
}