package envoy.data;

import java.util.function.Function;

/**
 * Contains a single {@link Config} value as well as the corresponding command line arguments and
 * its default value.
 * <p>
 * All {@code ConfigItem}s are automatically mandatory.
 *
 * @author Kai S. K. Engelbart
 * @param <T> the type of the config item's value
 * @since Envoy Common v0.1-beta
 */
public final class ConfigItem<T> {

	private final String				commandLong, commandShort;
	private final Function<String, T>	parseFunction;

	private T value;

	/**
	 * Initializes a {@link ConfigItem}.
	 *
	 * @param commandLong   the long command line argument to set this value
	 * @param commandShort  the short command line argument to set this value
	 * @param parseFunction the {@code Function<String, T>} that parses the value from a string
	 * @since Envoy Common v0.1-beta
	 */
	public ConfigItem(String commandLong, String commandShort, Function<String, T> parseFunction) {
		this.commandLong	= commandLong;
		this.commandShort	= commandShort;
		this.parseFunction	= parseFunction;
	}

	/**
	 * Parses this {@ConfigItem}'s value from a string.
	 *
	 * @param input the string to parse from
	 * @since Envoy Common v0.1-beta
	 */
	public void parse(String input) {
		value = parseFunction.apply(input);
	}

	/**
	 * @return The long command line argument to set the value of this {@link ConfigItem}
	 * @since Envoy Common v0.1-beta
	 */
	public String getCommandLong() { return commandLong; }

	/**
	 * @return The short command line argument to set the value of this {@link ConfigItem}
	 * @since Envoy Common v0.1-beta
	 */
	public String getCommandShort() { return commandShort; }

	/**
	 * @return the value of this {@link ConfigItem}
	 * @since Envoy Common v0.1-beta
	 */
	public T get() {
		return value;
	}

	/**
	 * @param value the value to set
	 * @since Envoy Common v0.2-beta
	 */
	protected void setValue(T value) { this.value = value; }
}