envoy/src/main/java/envoy/client/Config.java

package envoy.client;

import java.io.File;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;
import java.util.logging.Level;

import envoy.exception.EnvoyException;

/**
 * Manages all application settings that are set during application startup by
 * either loading them from the {@link Properties} file
 * {@code client.properties} or parsing them from the command line arguments of
 * the application.<br>
 * <br>
 * Project: <strong>envoy-client</strong><br>
 * File: <strong>Config.java</strong><br>
 * Created: <strong>12 Oct 2019</strong><br>
 *
 * @author Kai S. K. Engelbart
 * @since Envoy v0.1-alpha
 */
public class Config {

	private Map<String, ConfigItem<?>> items = new HashMap<>();

	private static Config config;

	private Config() {
		items.put("server", new ConfigItem<>("server", "s", (input) -> input, null));
		items.put("port", new ConfigItem<>("port", "p", (input) -> Integer.parseInt(input), null));
		items.put("localDB", new ConfigItem<>("localDB", "db", (input) -> new File(input), new File("localDB")));
		items.put("homeDirectory",
				new ConfigItem<>("homeDirectory", "h", (input) -> new File(input), new File(System.getProperty("user.home"), ".envoy")));
		items.put("fileLevelBarrier", new ConfigItem<>("fileLevelBarrier", "fb", (input) -> Level.parse(input), Level.CONFIG));
		items.put("consoleLevelBarrier", new ConfigItem<>("consoleLevelBarrier", "cb", (input) -> Level.parse(input), Level.FINEST));
	}

	/**
	 * @return the singleton instance of the {@link Config}
	 * @since Envoy v0.1-alpha
	 */
	public static Config getInstance() {
		if (config == null) config = new Config();
		return config;
	}

	/**
	 * Defaults to the {@code client.properties} file for information.
	 * This file contains information about
	 * the server and port, as well as the path to the local
	 * database and the synchronization timeout
	 *
	 * @throws EnvoyException if the {@code client.properties} file could not be
	 *                        loaded
	 * @since Envoy v0.1-alpha
	 */
	public void load() throws EnvoyException {
		ClassLoader loader = getClass().getClassLoader();
		try {
			Properties properties = new Properties();
			properties.load(loader.getResourceAsStream("client.properties"));
			items.forEach((name, item) -> { if (properties.containsKey(name)) item.parse(properties.getProperty(name)); });
		} catch (Exception e) {
			throw new EnvoyException("Failed to load client.properties", e);
		}
	}

	/**
	 * Sets the server, port and localDB path via command line properties --server /
	 * -s, --port / -p and --localDB / -db.
	 *
	 * @param args the command line arguments to parse
	 * @throws EnvoyException if the command line arguments contain an unknown token
	 * @since Envoy v0.1-alpha
	 */
	public void load(String[] args) throws EnvoyException {
		for (int i = 0; i < args.length; i++)
			for (ConfigItem<?> item : items.values())
				if (args[i].startsWith("--")) {
					if (args[i].length() == 2) throw new EnvoyException("Malformed command line argument at position " + i);
					final String commandLong = args[i].substring(2);
					if (item.getCommandLong().equals(commandLong)) {
						item.parse(args[++i]);
						break;
					}
				} else if (args[i].startsWith("-")) {
					if (args[i].length() == 1) throw new EnvoyException("Malformed command line argument at position " + i);
					final String commandShort = args[i].substring(1);
					if (item.getCommandShort().equals(commandShort)) {
						item.parse(args[++i]);
						break;
					}
				} else throw new EnvoyException("Malformed command line argument at position " + i);
	}

	/**
	 * @return {@code true} if server, port and localDB directory are known.
	 * @since Envoy v0.1-alpha
	 */
	public boolean isInitialized() { return items.values().stream().noneMatch(item -> item.get() == null); }

	/**
	 * @return the host name of the Envoy server
	 * @since Envoy v0.1-alpha
	 */
	public String getServer() { return (String) items.get("server").get(); }

	/**
	 * @return the port at which the Envoy server is located on the host
	 * @since Envoy v0.1-alpha
	 */
	public Integer getPort() { return (Integer) items.get("port").get(); }

	/**
	 * @return the local database specific to the client user
	 * @since Envoy v0.1-alpha
	 */
	public File getLocalDB() { return (File) items.get("localDB").get(); }

	/**
	 * @return the directory in which all local files are saves
	 * @since Envoy v0.2-alpha
	 */
	public File getHomeDirectory() { return (File) items.get("homeDirectory").get(); }

	/**
	 * @return the minimal {@link Level} to log inside the log file
	 * @since Envoy v0.2-alpha
	 */
	public Level getFileLevelBarrier() { return (Level) items.get("fileLevelBarrier").get(); }

	/**
	 * @return the minimal {@link Level} to log inside the console
	 * @since Envoy v0.2-alpha
	 */
	public Level getConsoleLevelBarrier() { return (Level) items.get("consoleLevelBarrier").get(); }
}