
package org.codehaus.groovy.grails.web.taglib;

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import org.codehaus.groovy.grails.web.taglib.exceptions.GrailsTagException;

/**
 * A registry for holding all Grails tag implementations.
 *
 * @author Graeme Rocher
 */
public class GrailsTagRegistry {

    private static GrailsTagRegistry instance = new GrailsTagRegistry();

    private static Map<String, Class<?>> tagRegistry = new ConcurrentHashMap<String, Class<?>>();

    static {
        instance.registerTag(RenderInputTag.TAG_NAME,   RenderInputTag.class);
        instance.registerTag(GroovyEachTag.TAG_NAME,    GroovyEachTag.class);
        instance.registerTag(GroovyIfTag.TAG_NAME,      GroovyIfTag.class);
        instance.registerTag(GroovyUnlessTag.TAG_NAME,  GroovyUnlessTag.class);
        instance.registerTag(GroovyElseTag.TAG_NAME,    GroovyElseTag.class);
        instance.registerTag(GroovyElseIfTag.TAG_NAME,  GroovyElseIfTag.class);
        instance.registerTag(GroovyFindAllTag.TAG_NAME, GroovyFindAllTag.class);
        instance.registerTag(GroovyCollectTag.TAG_NAME, GroovyCollectTag.class);
        instance.registerTag(GroovyGrepTag.TAG_NAME,    GroovyGrepTag.class);
        instance.registerTag(GroovyWhileTag.TAG_NAME,   GroovyWhileTag.class);
        instance.registerTag(GroovyDefTag.TAG_NAME,     GroovyDefTag.class);
    }

    private GrailsTagRegistry() {
        // singleton
    }

    public static GrailsTagRegistry getInstance() {
        return instance;
    }

    public void registerTag(String tagName, Class<?> tag) {
        tagRegistry.put(tagName, tag);
    }

    public boolean tagSupported(String tagName) {
        return tagRegistry.containsKey(tagName);
    }

    public boolean isSyntaxTag(String tagName) {
        if (tagRegistry.containsKey(tagName)) {
            return GroovySyntaxTag.class.isAssignableFrom(tagRegistry.get(tagName));
        }
        return false;
    }

    public GrailsTag newTag(String tagName) {
        if (!tagRegistry.containsKey(tagName)) {
            throw new GrailsTagException("Tag [" + tagName + "] is not a a valid grails tag");
        }

        Class<?> tagClass = tagRegistry.get(tagName);

        try {
            return (GrailsTag)tagClass.newInstance();
        }
        catch (InstantiationException e) {
            throw new GrailsTagException("Instantiation error loading tag ["+tagName+"]: " + e.getMessage(), e);
        }
        catch (IllegalAccessException e) {
            throw new GrailsTagException("Illegal access error loading tag ["+tagName+"]: " + e.getMessage(), e);
        }
    }

    public boolean isRequestContextTag(String tagName) {
        if (tagRegistry.containsKey(tagName)) {
            return RequestContextTag.class.isAssignableFrom(tagRegistry.get(tagName));
        }
        return false;
    }
}
