ClassName.java

package net.ayld.facade.model;

import com.google.common.collect.ImmutableSet;
import net.ayld.facade.util.Tokenizer;

import java.util.Set;
import java.util.regex.Pattern;

/** 
 * Meant to represent a fully qualified class name.
 * 
 * The idea behind the class is to provide a model object that makes sure that a string is actually a class name and not 
 * something else, so one doesn't need to check 'by hand' every time.
 * */
public final class ClassName {

	/** 
	 * This regex only checks plausibility it doesn't check validity. For a validity check a comparison against Java's reserved words must be made.
	 * Also checks whether the name contains only Unicode chars.
	 * 
	 * More info here:
	 *   http://docs.oracle.com/javase/specs/#3.8
	 * 
	 * */
	private final static String CLASS_NAME_VALIDATION_REGEX = "([a-zA-Z_$][a-zA-Z\\d_$]*\\.)*[a-zA-Z_$][a-zA-Z\\d_$]*";
	
	
	/** 
	 * Class names that are valid classes, but still don't match the above regex.
	 * 
	 * See here:
	 *     http://docs.oracle.com/javase/7/docs/technotes/tools/solaris/javadoc.html#packagecomment
	 * */
	private final static Set<String> EXCEPTIONAL_CLASS_NAMES = ImmutableSet.of(
			"package-info"
	);
	
	private final String qualifiedClassName;

	/** 
	 * Creates a {@link ClassName}.
	 * 
	 * Doesn't allow nulls or empty strings.
	 * Does everything it can to make sure that the argument is in fact a fully qualified class name and not something else.
	 * 
	 * @param qualifiedClassName a class name
	 * */
	public ClassName(String qualifiedClassName) {
		if (!isClassName(qualifiedClassName)) {
			throw new IllegalArgumentException("invalid fully qualified class name: " + qualifiedClassName + ", expected: " + CLASS_NAME_VALIDATION_REGEX);
		}
		this.qualifiedClassName = qualifiedClassName;
	}

	private static boolean isClassName(String qualifiedClassName) {
		final String shortName = Tokenizer.delimiter(".").tokenize(qualifiedClassName).lastToken();
		
		return Pattern.matches(CLASS_NAME_VALIDATION_REGEX, qualifiedClassName) || EXCEPTIONAL_CLASS_NAMES.contains(shortName);
	}

	/** 
	 * Returns the short name of the wrapped qualified class name.
	 * 
	 * <pre>
	 * 
	 * In other words for this:
	 *   
	 *   <code>net.ayld.facade.model.ClassName</code>
	 * 
	 * this method will return:
	 * 
	 *   <code>ClassName</code>
	 *   
	 * <pre>
	 *   
	 * @return the short name of the wrapped qualified class name
	 * */
	public String shortName() {
		return Tokenizer.delimiter(".").tokenize(qualifiedClassName).lastToken();
	}
	
	/** 
	 * Returns the wrapped qualifiedClassName.
	 * 
	 * @return the wrapped qualifiedClassName
	 * */
	@Override
	public String toString() {
		return qualifiedClassName;
	}

	@Override
	public int hashCode() {
		return qualifiedClassName.hashCode();
	}

	@Override
	public boolean equals(Object obj) {
		if (obj == null) {
			return false;
		}
		
		if (!(obj instanceof ClassName)) {
			return false;
		}
		
		final ClassName other = (ClassName) obj;
		
		return other.toString().equals(this.toString());
	}
}