Auto username/UID parser, and small change in parse function.

src/main/java/net/pingex/dcf/util/ArgumentParser.java

@@ -1,9 +1,12 @@
 package net.pingex.dcf.util;
 
 import org.apache.commons.lang3.ClassUtils;
-
+import sx.blah.discord.api.IDiscordClient;
+import sx.blah.discord.handle.obj.IUser;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Optional;
+import java.util.regex.Pattern;
 
 /**
  * Util class used to parse a String into primitive types.
@@ -21,7 +24,7 @@ public class ArgumentParser
 	 */
 	public static Object parse(Class<?> target, String value) throws IllegalArgumentException
 	{
-		if(value         == null   || value.equals("null")  ) return null;
+		if(value         == null   || value.equalsIgnoreCase("null")) return null;
 		if(Boolean.class == target || Boolean.TYPE == target) return Boolean.parseBoolean(value);
 		if(Byte.class    == target || Byte.TYPE    == target) return Byte.parseByte(value);
 		if(Short.class   == target || Short.TYPE   == target) return Short.parseShort(value);
@@ -77,6 +80,43 @@ public class ArgumentParser
 		return outputList;
 	}
 
+	private static Pattern usernamePattern = Pattern.compile("^.*#\\d{4}$");
+	private static Pattern idPattern = Pattern.compile("^\\d{18}$");
+
+	/**
+	 * Binds an username or an UID to an actual {@code IUser}.
+	 * The following username input formats are allowed:
+	 * <ul>
+	 *     <li>18-digit UID: "123456789012345678"</li>
+	 *     <li>Username and 4-digit discriminator: "Username#1234"</li>
+	 * </ul>
+	 *
+	 * Unknown formats will cause a {@link ParserException}.
+	 *
+	 * @param input String to parse
+	 * @param client Discord instance to look for actual users
+	 * @return A filled Optional when an user was found, an empty one otherwise.
+	 * @throws ParserException Unknown format
+	 */
+	public static Optional<IUser> checkParseUsernameOrID(String input, IDiscordClient client) throws ParserException
+	{
+		IUser foundUser = null;
+
+		if(idPattern.matcher(input).matches()) foundUser = client.getUserByID(input); // UID
+		else if(usernamePattern.matcher(input).matches()) // username#1234
+		{
+			for(IUser iUser : client.getUsers()) // Greedy
+				if(input.equalsIgnoreCase(iUser.getName() + "#" + iUser.getDiscriminator()))
+				{
+					foundUser = iUser;
+					break; // Limit greediness
+				}
+		}
+		else throw new ParserException("Invalid argument."); // ?
+
+		return Optional.ofNullable(foundUser);
+	}
+
 	/**
 	 * Thrown whenever any parse operation failed.
 	 */