package uk.org.ury.backend.database;

import java.util.HashMap;
import java.util.Map;

import uk.org.ury.backend.database.exceptions.MissingPropertyException;

/**
 * An abstract class presenting a template for objects serving as a data
 * structure for collections of properties retrieved from a SQL database.
 * 
 * @param E
 *            The enumeration type used as the property list.
 * 
 * @param T
 *            The type of datum stored for each property.
 * 
 * @author Matt Windsor
 */
public abstract class DatabaseItem<E, T> {
    private Map<E, T> properties;

    /**
     * Construct a new item from an existing list of properties.
     * 
     * @param properties
     *            The map of properties that the new item will inherit.
     */
    public DatabaseItem(Map<E, T> properties) {
	this.properties = properties;
    }

    /**
     * Check whether a property has been set in the item.
     * 
     * @return true if the property has been set; false otherwise.
     */

    public boolean has(E property) {
	return properties.containsKey(property);
    }

    /**
     * Query this item for a property.
     * 
     * @param property
     *            The property to query.
     * 
     * @return The property, if it exists.
     * 
     * @throws MissingPropertyException
     *             if the property does not exist.
     */
    public T get(E property) throws MissingPropertyException {
	if (properties.containsKey(property))
	    return properties.get(property);
	else
	    throw new MissingPropertyException(property.toString());
    }

    /**
     * Retrieve a map of string representations of the properties.
     * 
     * This relies on E and T having meaningful toString methods.
     * 
     * @return a list of lines representing the response.
     */
    public Map<String, String> asResponse() {
	// TODO: Fan out implementation details into separate class
	Map<String, String> response = new HashMap<String, String>();

	for (E property : properties.keySet()) {
	    if (properties.get(property) != null)
		response.put(property.toString(), properties.get(property)
			.toString());
	}

	return response;
    }
}