package gdi1database.items;

/**
* describes the interface for an arbitrary database item
* that can be described by its name, data, key, and "additional data".
*
* @author Guido Rößling (roessling@acm.org)
*/
public interface DatabaseItem {

/**
* returns the name of the database item
*
* @return the name of the database item
*/
public String getName();

/**
* returns the main data of the database item
*
* @return the data of the database item
*/
public String getData();

/**
* returns additional data for the database item
*
* @return the additional data for the database item
*/
public String getAdditionalData();

/**
* returns the key of the database item
*
* @return the key of the database item
*/
public String getKey();
}

package gdi1database;

import gdi1database.items.DatabaseItem;

import java.util.Set;

/**
* Describes the interface for a (simplified) database implementation.
*
* @author Guido Rößling (roessling@acm.org)
*/
public interface DatabaseInterface<T extends DatabaseItem> {

/**
* adds a DatabaseItem to the database. Note: entries that already
* exist will not be added again.
*
* @param e
* the DatabaseItem that should be inserted to the database.
* @return true if DatabaseItem has been successfully inserted to the
* database, else false (usually because the value is null or already
* existed).
*/
public boolean addEntry(T e);

/**
* deletes the DatabaseItem e if it exists and updates the database
*
* @param e
* the DatabaseItem which should be deleted.
* @return true if the DatabaseItem has been deleted successfully, else
* false.
*/
public boolean deleteEntry(T e);

/**
* Drops the database and replaces it with one of size 0
*
* @return true if database has been deleted correctly, else false.
*/
public boolean dropDatabase();

/**
* returns true if an DatabaseItem matching the parameter exists in
* the database
*
* @param e
* the DatabaseItem that should exist.
* @return true if the DatabaseItem exists inside the database, else
* false.
*/
public boolean entryExists(T e);

/**
* returns the element at the chosen position of null if the position is
* invalid
*
* @param key
* the key of the DatabaseItem to be returned.
* @return the DatabaseItem object at the given position, if any, else
* null.
*/
public T getEntry(String key);

/**
* returns the keys for all elements in this database
*
* @return the set of (String) keys for all elements in this database
*/
public Set<String> getKeys();

/**
* returns the size of this database
*
* @return the size of this database.
*/
public int getSize();
}

package gdi1database;

/**
* describes a column in a (simplified) database
*
* @author Guido R&ouml;&szlig;ling (roessling@acm.org)
*/
public enum DatabaseColumn {
DATA, NAME, ADDITIONAL_DATA, KEY, DATA_NAME, KEY_DATA, KEY_DATA_NAME, ALL
}