/*
 * 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.jasper.compiler;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Iterator;

import javax.servlet.ServletContext;

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

/**
 * Manages tag plugin optimizations.
 * @author Kin-man Chung
 */
public class TagPluginManager {

    private static final String META_INF_JASPER_TAG_PLUGINS_XML =
            "META-INF/org.apache.jasper/tagPlugins.xml";
    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<String, TagPlugin> tagPlugins = null;
    private ServletContext ctxt;

    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;
        }

        page.visit(new NodeVisitor(this, pageInfo));
    }

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

        tagPlugins = new HashMap<String, TagPlugin>();

        Enumeration<URL> urls = null;
        try {
            urls = ctxt.getClassLoader().getResources(
                    META_INF_JASPER_TAG_PLUGINS_XML);
        } catch (IOException ioe) {
            throw new JasperException(ioe);
        }

        if (urls != null) {
            while(urls.hasMoreElements()) {
                URL url = urls.nextElement();
                InputStream is = null;
                try {
                    is = url.openStream();
                    loadTagPlugins(err, is);
                } catch(IOException ioe) {
                    throw new JasperException(ioe);
                } finally {
                    if (is != null) {
                        try {
                            is.close();
                        } catch (IOException ioe) {
                            throw new JasperException(ioe);
                        }
                    }
                }
            }
        }

        InputStream is = null;
        try {
            is = ctxt.getResourceAsStream(TAG_PLUGINS_XML);
            if (is != null) {
                loadTagPlugins(err, is);
            }
        } finally {
            try {
                if (is != null) {
                    is.close();
                }
            } catch (IOException ioe) {
                throw new JasperException(ioe);
            }
        }

        initialized = true;
    }


    private void loadTagPlugins(ErrorDispatcher err, InputStream is)
            throws JasperException {

        String blockExternalString = ctxt.getInitParameter(
                Constants.XML_BLOCK_EXTERNAL_INIT_PARAM);
        boolean blockExternal;
        if (blockExternalString == null) {
            blockExternal = true;
        } else {
            blockExternal = Boolean.parseBoolean(blockExternalString);
        }
        
        ParserUtils pu = new ParserUtils(false, blockExternal);
        
        TreeNode root = pu.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<String, TagPlugin>();
        Iterator<TreeNode> pluginList = root.findChildren("tag-plugin");
        while (pluginList.hasNext()) {
            TreeNode pluginNode = 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 =
                        ctxt.getClassLoader().loadClass(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, PageInfo pageInfo) {
        TagPlugin tagPlugin = tagPlugins.get(n.getTagHandlerClass().getName());
        if (tagPlugin == null) {
            return;
        }

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

    private static class NodeVisitor extends Node.Visitor {
        private final TagPluginManager manager;
        private final PageInfo pageInfo;

        public NodeVisitor(TagPluginManager manager, PageInfo pageInfo) {
            this.manager = manager;
            this.pageInfo = pageInfo;
        }

        @Override
        public void visit(Node.CustomTag n) throws JasperException {
            manager.invokePlugin(n, pageInfo);
            visitBody(n);
        }
    }

    private static class TagPluginContextImpl implements TagPluginContext {
        private final Node.CustomTag node;
        private Node.Nodes curNodes;
        private PageInfo pageInfo;
        private HashMap<String, Object> 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<String, Object>();
        }

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

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

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

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

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

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

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

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

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

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

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

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

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

        @Override
        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();
        }

        @Override
        public boolean isTagFile() {
            return pageInfo.isTagFile();
        }

        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;
        }
    }
}
