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Dual-side template engine for the JVM
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package org.duelengine.duel;

import java.util.HashSet;
import java.util.Locale;
import java.util.ResourceBundle;
import java.util.Set;

public final class JSUtility {

	/**
	 * Server-side representation of the JS concept of "undefined" 
	 */
	public final static Object UNDEFINED = new Object() {
		@Override
		public String toString() {
			return UNDEFINED_KEYWORD;
		};
	};

	/**
	 * The undefined keyword literal
	 */
	static final String UNDEFINED_KEYWORD = "undefined";

	private static final String CONFIG_RESOURCE = "org.duelengine.duel.JSUtility";
	private static Set reserved;
	private static Set globals;
	private static Set properties;
	private static Set browser;
	private static boolean inited;

	// static class
	private JSUtility() {}

	public static boolean isValidIdentifier(String ident, boolean nested) {
		if (ident == null || ident.isEmpty()) {
			return false;
		}

		if (!inited) {
			initLookups();
		}

		if (nested) {
			String[] parts = ident.split(".");
			for (int i=0, length=parts.length; i= '0') && (ch <= '9'))) {
				// digits are only allowed after first char
				continue;
			}

			// can be start or part
			if (((ch >= 'a') && (ch <= 'z')) ||
				((ch >= 'A') && (ch <= 'Z')) ||
				(ch == '_') || (ch == '$')) {
				indentPart = true;
				continue;
			}

			return false;
		}

		return true;		
	}

	public static boolean isGlobalIdent(String ident) {
		if (ident == null || ident.isEmpty()) {
			return false;
		}

		if (!inited) {
			initLookups();
		}

		return globals.contains(ident) || browser.contains(ident);
	}

	public static boolean isObjectProperty(String ident) {
		if (ident == null || ident.isEmpty()) {
			return false;
		}

		if (!inited) {
			initLookups();
		}

		return properties.contains(ident);
	}
	
	private static void initLookups() {

		String[] tags;
		Set set;

		// definitions maintained in JSVocab.properties
		ResourceBundle config = ResourceBundle.getBundle(CONFIG_RESOURCE, Locale.ROOT);

		// reserved words
		tags = (config != null) && config.containsKey("reserved") ?
				config.getString("reserved").split(",") : new String[0];
		set = new HashSet(tags.length);
		for (String value : tags) {
			set.add(value);
		}

		// add Object properties to reserved words
		tags = (config != null) && config.containsKey("properties") ?
				config.getString("properties").split(",") : new String[0];
		for (String value : tags) {
			set.add(value);
		}
		reserved = set;

		// global objects
		tags = (config != null) && config.containsKey("globals") ?
				config.getString("globals").split(",") : new String[0];
		set = new HashSet(tags.length);
		for (String value : tags) {
			set.add(value);
		}
		globals = set;

		// object properties
		tags = (config != null) && config.containsKey("properties") ?
				config.getString("properties").split(",") : new String[0];
		set = new HashSet(tags.length);
		for (String value : tags) {
			set.add(value);
		}
		properties = set;

		// browser objects
		tags = (config != null) && config.containsKey("browser") ?
				config.getString("browser").split(",") : new String[0];
		set = new HashSet(tags.length);
		for (String value : tags) {
			set.add(value);
		}
		browser = set;
	}
}