/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.struts2.jasper.compiler;

import java.util.*;
import java.io.*;
import javax.servlet.ServletContext;

import org.apache.struts2.jasper.JasperException;
import org.apache.struts2.jasper.xmlparser.ParserUtils;
import org.apache.struts2.jasper.xmlparser.TreeNode;
import org.apache.struts2.jasper.compiler.tagplugin.TagPlugin;
import org.apache.struts2.jasper.compiler.tagplugin.TagPluginContext;

/**
 * Manages tag plugin optimizations.
 * @author Kin-man Chung
 */

public class TagPluginManager {

    private static final String TAG_PLUGINS_XML = "/WEB-INF/tagPlugins.xml";
    private static final String TAG_PLUGINS_ROOT_ELEM = "tag-plugins";

    private boolean initialized = false;
    private HashMap tagPlugins = null;
    private ServletContext ctxt;
    private PageInfo pageInfo;

    public TagPluginManager(ServletContext ctxt) {
	this.ctxt = ctxt;
    }

    public void apply(Node.Nodes page, ErrorDispatcher err, PageInfo pageInfo)
	    throws JasperException {

	init(err);
	if (tagPlugins == null || tagPlugins.size() == 0) {
	    return;
	}

	this.pageInfo = pageInfo;

        page.visit(new Node.Visitor() {
            public void visit(Node.CustomTag n)
                    throws JasperException {
                invokePlugin(n);
                visitBody(n);
            }
        });

    }
 
    private void init(ErrorDispatcher err) throws JasperException {
	if (initialized)
	    return;

	InputStream is = ctxt.getResourceAsStream(TAG_PLUGINS_XML);
	if (is == null)
	    return;

	TreeNode root = (new ParserUtils()).parseXMLDocument(TAG_PLUGINS_XML,
							     is);
	if (root == null) {
	    return;
	}

	if (!TAG_PLUGINS_ROOT_ELEM.equals(root.getName())) {
	    err.jspError("jsp.error.plugin.wrongRootElement", TAG_PLUGINS_XML,
			 TAG_PLUGINS_ROOT_ELEM);
	}

	tagPlugins = new HashMap();
	Iterator pluginList = root.findChildren("tag-plugin");
	while (pluginList.hasNext()) {
	    TreeNode pluginNode = (TreeNode) pluginList.next();
            TreeNode tagClassNode = pluginNode.findChild("tag-class");
	    if (tagClassNode == null) {
		// Error
		return;
	    }
	    String tagClass = tagClassNode.getBody().trim();
	    TreeNode pluginClassNode = pluginNode.findChild("plugin-class");
	    if (pluginClassNode == null) {
		// Error
		return;
	    }

	    String pluginClassStr = pluginClassNode.getBody();
	    TagPlugin tagPlugin = null;
	    try {
		Class pluginClass = Class.forName(pluginClassStr);
		tagPlugin = (TagPlugin) pluginClass.newInstance();
	    } catch (Exception e) {
		throw new JasperException(e);
	    }
	    if (tagPlugin == null) {
		return;
	    }
	    tagPlugins.put(tagClass, tagPlugin);
	}
	initialized = true;
    }

    /**
     * Invoke tag plugin for the given custom tag, if a plugin exists for 
     * the custom tag's tag handler.
     *
     * The given custom tag node will be manipulated by the plugin.
     */
    private void invokePlugin(Node.CustomTag n) {
	TagPlugin tagPlugin = (TagPlugin)
		tagPlugins.get(n.getTagHandlerClass().getName());
	if (tagPlugin == null) {
	    return;
	}

	TagPluginContext tagPluginContext = new TagPluginContextImpl(n, pageInfo);
	n.setTagPluginContext(tagPluginContext);
	tagPlugin.doTag(tagPluginContext);
    }

    static class TagPluginContextImpl implements TagPluginContext {
	private Node.CustomTag node;
	private Node.Nodes curNodes;
	private PageInfo pageInfo;
	private HashMap pluginAttributes;

	TagPluginContextImpl(Node.CustomTag n, PageInfo pageInfo) {
	    this.node = n;
	    this.pageInfo = pageInfo;
	    curNodes = new Node.Nodes();
	    n.setAtETag(curNodes);
	    curNodes = new Node.Nodes();
	    n.setAtSTag(curNodes);
	    n.setUseTagPlugin(true);
	    pluginAttributes = new HashMap();
        }

        public TagPluginContext getParentContext() {
            Node parent = node.getParent();
            if (! (parent instanceof Node.CustomTag)) {
                return null;
            }
            return ((Node.CustomTag) parent).getTagPluginContext();
        }

        public void setPluginAttribute(String key, Object value) {
            pluginAttributes.put(key, value);
        }

        public Object getPluginAttribute(String key) {
            return pluginAttributes.get(key);
        }

        public boolean isScriptless() {
            return node.getChildInfo().isScriptless();
        }

        public boolean isConstantAttribute(String attribute) {
            Node.JspAttribute attr = getNodeAttribute(attribute);
            if (attr == null)
                return false;
            return attr.isLiteral();
        }

        public String getConstantAttribute(String attribute) {
            Node.JspAttribute attr = getNodeAttribute(attribute);
            if (attr == null)
                return null;
            return attr.getValue();
        }

        public boolean isAttributeSpecified(String attribute) {
            return getNodeAttribute(attribute) != null;
        }

        public String getTemporaryVariableName() {
            return node.getRoot().nextTemporaryVariableName();
        }

        public void generateImport(String imp) {
            pageInfo.addImport(imp);
        }

        public void generateDeclaration(String id, String text) {
            if (pageInfo.isPluginDeclared(id)) {
                return;
            }
            curNodes.add(new Node.Declaration(text, node.getStart(), null));
        }

        public void generateJavaSource(String sourceCode) {
            curNodes.add(new Node.Scriptlet(sourceCode, node.getStart(),
                                            null));
        }

        public void generateAttribute(String attributeName) {
            curNodes.add(new Node.AttributeGenerator(node.getStart(),
                                                     attributeName,
                                                     node));
        }

        public void dontUseTagPlugin() {
            node.setUseTagPlugin(false);
        }

        public void generateBody() {
            // Since we'll generate the body anyway, this is really a nop, 
            // except for the fact that it lets us put the Java sources the
            // plugins produce in the correct order (w.r.t the body).
            curNodes = node.getAtETag();
        }

        private Node.JspAttribute getNodeAttribute(String attribute) {
            Node.JspAttribute[] attrs = node.getJspAttributes();
            for (int i=0; attrs != null && i < attrs.length; i++) {
                if (attrs[i].getName().equals(attribute)) {
                    return attrs[i];
                }
            }
            return null;
        }
    }
}
