/*
 * 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.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.JarURLConnection;
import java.net.URL;
import java.util.Stack;
import java.util.jar.JarFile;

import org.apache.struts2.jasper.JasperException;
import org.apache.struts2.jasper.JspCompilationContext;
import org.apache.struts2.jasper.xmlparser.XMLEncodingDetector;
import org.xml.sax.Attributes;

/**
 * Controller for the parsing of a JSP page.
 * <p>
 * The same ParserController instance is used for a JSP page and any JSP
 * segments included by it (via an include directive), where each segment may
 * be provided in standard or XML syntax. This class selects and invokes the
 * appropriate parser for the JSP page and its included segments.
 *
 * @author Pierre Delisle
 * @author Jan Luehe
 */
class ParserController implements TagConstants {

    private static final String CHARSET = "charset=";

    private JspCompilationContext ctxt;
    private Compiler compiler;
    private ErrorDispatcher err;

    /*
     * Indicates the syntax (XML or standard) of the file being processed
     */
    private boolean isXml;

    /*
     * A stack to keep track of the 'current base directory'
     * for include directives that refer to relative paths.
     */
    private Stack baseDirStack = new Stack();

    private boolean isEncodingSpecifiedInProlog;
    private boolean isBomPresent;
    private int skip;

    private String sourceEnc;

    private boolean isDefaultPageEncoding;
    private boolean isTagFile;
    private boolean directiveOnly;

    /*
     * Constructor
     */
    public ParserController(JspCompilationContext ctxt, Compiler compiler) {
        this.ctxt = ctxt; 
        this.compiler = compiler;
        this.err = compiler.getErrorDispatcher();
    }

    public JspCompilationContext getJspCompilationContext () {
        return ctxt;
    }

    public Compiler getCompiler () {
        return compiler;
    }

    /**
     * Parses a JSP page or tag file. This is invoked by the compiler.
     *
     * @param inFileName The path to the JSP page or tag file to be parsed.
     */
    public Node.Nodes parse(String inFileName)
    throws FileNotFoundException, JasperException, IOException {
        // If we're parsing a packaged tag file or a resource included by it
        // (using an include directive), ctxt.getTagFileJar() returns the 
        // JAR file from which to read the tag file or included resource,
        // respectively.
        isTagFile = ctxt.isTagFile();
        directiveOnly = false;
        return doParse(inFileName, null, ctxt.getTagFileJarUrl());
    }

    /**
     * Parses the directives of a JSP page or tag file. This is invoked by the
     * compiler.
     *
     * @param inFileName The path to the JSP page or tag file to be parsed.
     */
    public Node.Nodes parseDirectives(String inFileName)
    throws FileNotFoundException, JasperException, IOException {
        // If we're parsing a packaged tag file or a resource included by it
        // (using an include directive), ctxt.getTagFileJar() returns the 
        // JAR file from which to read the tag file or included resource,
        // respectively.
        isTagFile = ctxt.isTagFile();
        directiveOnly = true;
        return doParse(inFileName, null, ctxt.getTagFileJarUrl());
    }


    /**
     * Processes an include directive with the given path.
     *
     * @param inFileName The path to the resource to be included.
     * @param parent The parent node of the include directive.
     * @param jarFile The JAR file from which to read the included resource,
     * or null of the included resource is to be read from the filesystem
     */
    public Node.Nodes parse(String inFileName, Node parent,
            URL jarFileUrl)
    throws FileNotFoundException, JasperException, IOException {
        // For files that are statically included, isTagfile and directiveOnly
        // remain unchanged.
        return doParse(inFileName, parent, jarFileUrl);
    }

    /**
     * Extracts tag file directive information from the tag file with the
     * given name.
     *
     * This is invoked by the compiler 
     *
     * @param inFileName The name of the tag file to be parsed.
     * @deprecated Use {@link #parseTagFileDirectives(String, URL)}
     *             See https://issues.apache.org/bugzilla/show_bug.cgi?id=46471
     */
    public Node.Nodes parseTagFileDirectives(String inFileName)
    throws FileNotFoundException, JasperException, IOException {
        return parseTagFileDirectives(
                inFileName, ctxt.getTagFileJarUrl(inFileName));
    }

    /**
     * Extracts tag file directive information from the given tag file.
     *
     * This is invoked by the compiler 
     *
     * @param inFileName    The name of the tag file to be parsed.
     * @param tagFileJarUrl The location of the tag file.
     */
    public Node.Nodes parseTagFileDirectives(String inFileName,
            URL tagFileJarUrl)
            throws FileNotFoundException, JasperException, IOException {
        boolean isTagFileSave = isTagFile;
        boolean directiveOnlySave = directiveOnly;
        isTagFile = true;
        directiveOnly = true;
        Node.Nodes page = doParse(inFileName, null, tagFileJarUrl);
        directiveOnly = directiveOnlySave;
        isTagFile = isTagFileSave;
        return page;
    }

    /**
     * Parses the JSP page or tag file with the given path name.
     *
     * @param inFileName The name of the JSP page or tag file to be parsed.
     * @param parent The parent node (non-null when processing an include
     * directive)
     * @param isTagFile true if file to be parsed is tag file, and false if it
     * is a regular JSP page
     * @param directivesOnly true if the file to be parsed is a tag file and
     * we are only interested in the directives needed for constructing a
     * TagFileInfo.
     * @param jarFile The JAR file from which to read the JSP page or tag file,
     * or null if the JSP page or tag file is to be read from the filesystem
     */
    private Node.Nodes doParse(String inFileName,
            Node parent,
            URL jarFileUrl)
    throws FileNotFoundException, JasperException, IOException {

        Node.Nodes parsedPage = null;
        isEncodingSpecifiedInProlog = false;
        isBomPresent = false;
        isDefaultPageEncoding = false;

        JarFile jarFile = getJarFile(jarFileUrl);
        String absFileName = resolveFileName(inFileName);
        String jspConfigPageEnc = getJspConfigPageEncoding(absFileName);

        // Figure out what type of JSP document and encoding type we are
        // dealing with
        determineSyntaxAndEncoding(absFileName, jarFile, jspConfigPageEnc);

        if (parent != null) {
            // Included resource, add to dependent list
            if (jarFile == null) {
                compiler.getPageInfo().addDependant(absFileName);
            } else {
                compiler.getPageInfo().addDependant(
                        jarFileUrl.toExternalForm() + absFileName.substring(1));
            }
        }

        if ((isXml && isEncodingSpecifiedInProlog) || isBomPresent) {
            /*
             * Make sure the encoding explicitly specified in the XML
             * prolog (if any) matches that in the JSP config element
             * (if any), treating "UTF-16", "UTF-16BE", and "UTF-16LE" as
             * identical.
             */
            if (jspConfigPageEnc != null && !jspConfigPageEnc.equals(sourceEnc)
                    && (!jspConfigPageEnc.startsWith("UTF-16")
                            || !sourceEnc.startsWith("UTF-16"))) {
                err.jspError("jsp.error.prolog_config_encoding_mismatch",
                        sourceEnc, jspConfigPageEnc);
            }
        }

        // Dispatch to the appropriate parser
        if (isXml) {
            // JSP document (XML syntax)
            // InputStream for jspx page is created and properly closed in
            // JspDocumentParser.
            parsedPage = JspDocumentParser.parse(this, absFileName,
                    jarFile, parent,
                    isTagFile, directiveOnly,
                    sourceEnc,
                    jspConfigPageEnc,
                    isEncodingSpecifiedInProlog,
                    isBomPresent);
        } else {
            // Standard syntax
            InputStreamReader inStreamReader = null;
            try {
                inStreamReader = JspUtil.getReader(absFileName, sourceEnc,
                        jarFile, ctxt, err, skip);
                JspReader jspReader = new JspReader(ctxt, absFileName,
                        sourceEnc, inStreamReader,
                        err);
                parsedPage = Parser.parse(this, jspReader, parent, isTagFile,
                        directiveOnly, jarFileUrl,
                        sourceEnc, jspConfigPageEnc,
                        isDefaultPageEncoding, isBomPresent);
            } finally {
                if (inStreamReader != null) {
                    try {
                        inStreamReader.close();
                    } catch (Exception any) {
                    }
                }
            }
        }

        if (jarFile != null) {
            try {
                jarFile.close();
            } catch (Throwable t) {}
        }

        baseDirStack.pop();

        return parsedPage;
    }

    /*
     * Checks to see if the given URI is matched by a URL pattern specified in
     * a jsp-property-group in web.xml, and if so, returns the value of the
     * <page-encoding> element.
     *
     * @param absFileName The URI to match
     *
     * @return The value of the <page-encoding> attribute of the 
     * jsp-property-group with matching URL pattern
     */
    private String getJspConfigPageEncoding(String absFileName)
    throws JasperException {

        JspConfig jspConfig = ctxt.getOptions().getJspConfig();
        JspConfig.JspProperty jspProperty
            = jspConfig.findJspProperty(absFileName);
        return jspProperty.getPageEncoding();
    }

    /**
     * Determines the syntax (standard or XML) and page encoding properties
     * for the given file, and stores them in the 'isXml' and 'sourceEnc'
     * instance variables, respectively.
     */
    private void determineSyntaxAndEncoding(String absFileName,
            JarFile jarFile,
            String jspConfigPageEnc)
    throws JasperException, IOException {

        isXml = false;

        /*
         * 'true' if the syntax (XML or standard) of the file is given
         * from external information: either via a JSP configuration element,
         * the ".jspx" suffix, or the enclosing file (for included resources)
         */
        boolean isExternal = false;

        /*
         * Indicates whether we need to revert from temporary usage of
         * "ISO-8859-1" back to "UTF-8"
         */
        boolean revert = false;

        JspConfig jspConfig = ctxt.getOptions().getJspConfig();
        JspConfig.JspProperty jspProperty = jspConfig.findJspProperty(
                absFileName);
        if (jspProperty.isXml() != null) {
            // If <is-xml> is specified in a <jsp-property-group>, it is used.
            isXml = JspUtil.booleanValue(jspProperty.isXml());
            isExternal = true;
        } else if (absFileName.endsWith(".jspx")
                || absFileName.endsWith(".tagx")) {
            isXml = true;
            isExternal = true;
        }

        if (isExternal && !isXml) {
            // JSP (standard) syntax. Use encoding specified in jsp-config
            // if provided.
            sourceEnc = jspConfigPageEnc;
            if (sourceEnc != null) {
                return;
            }
            // We don't know the encoding, so use BOM to determine it
            sourceEnc = "ISO-8859-1";
        } else {
            // XML syntax or unknown, (auto)detect encoding ...
            Object[] ret = XMLEncodingDetector.getEncoding(absFileName,
                    jarFile, ctxt, err);
            sourceEnc = (String) ret[0];
            if (((Boolean) ret[1]).booleanValue()) {
                isEncodingSpecifiedInProlog = true;
            }
            if (((Boolean) ret[2]).booleanValue()) {
                isBomPresent = true;
            }
            skip = ((Integer) ret[3]).intValue();

            if (!isXml && sourceEnc.equals("UTF-8")) {
                /*
                 * We don't know if we're dealing with XML or standard syntax.
                 * Therefore, we need to check to see if the page contains
                 * a <jsp:root> element.
                 *
                 * We need to be careful, because the page may be encoded in
                 * ISO-8859-1 (or something entirely different), and may
                 * contain byte sequences that will cause a UTF-8 converter to
                 * throw exceptions. 
                 *
                 * It is safe to use a source encoding of ISO-8859-1 in this
                 * case, as there are no invalid byte sequences in ISO-8859-1,
                 * and the byte/character sequences we're looking for (i.e.,
                 * <jsp:root>) are identical in either encoding (both UTF-8
                 * and ISO-8859-1 are extensions of ASCII).
                 */
                sourceEnc = "ISO-8859-1";
                revert = true;
            }
        }

        if (isXml) {
            // (This implies 'isExternal' is TRUE.)
            // We know we're dealing with a JSP document (via JSP config or
            // ".jspx" suffix), so we're done.
            return;
        }

        /*
         * At this point, 'isExternal' or 'isXml' is FALSE.
         * Search for jsp:root action, in order to determine if we're dealing 
         * with XML or standard syntax (unless we already know what we're 
         * dealing with, i.e., when 'isExternal' is TRUE and 'isXml' is FALSE).
         * No check for XML prolog, since nothing prevents a page from
         * outputting XML and still using JSP syntax (in this case, the 
         * XML prolog is treated as template text).
         */
        JspReader jspReader = null;
        try {
            jspReader = new JspReader(ctxt, absFileName, sourceEnc, jarFile,
                    err);
        } catch (FileNotFoundException ex) {
            throw new JasperException(ex);
        }
        jspReader.setSingleFile(true);
        Mark startMark = jspReader.mark();
        if (!isExternal) {
            jspReader.reset(startMark);
            if (hasJspRoot(jspReader)) {
                if (revert) {
                    sourceEnc = "UTF-8";
                }
                isXml = true;
                return;
            } else {
                if (revert && isBomPresent) {
                    sourceEnc = "UTF-8";
                }
                isXml = false;
            }
        }

        /*
         * At this point, we know we're dealing with JSP syntax.
         * If an XML prolog is provided, it's treated as template text.
         * Determine the page encoding from the page directive, unless it's
         * specified via JSP config.
         */
        if (!isBomPresent) {
            sourceEnc = jspConfigPageEnc;
            if (sourceEnc == null) {
                sourceEnc = getPageEncodingForJspSyntax(jspReader, startMark);
                if (sourceEnc == null) {
                    // Default to "ISO-8859-1" per JSP spec
                    sourceEnc = "ISO-8859-1";
                    isDefaultPageEncoding = true;
                }
            }
        }
        
    }

    /*
     * Determines page source encoding for page or tag file in JSP syntax,
     * by reading (in this order) the value of the 'pageEncoding' page
     * directive attribute, or the charset value of the 'contentType' page
     * directive attribute.
     *
     * @return The page encoding, or null if not found
     */
    private String getPageEncodingForJspSyntax(JspReader jspReader,
            Mark startMark)
    throws JasperException {

        String encoding = null;
        String saveEncoding = null;

        jspReader.reset(startMark);

        /*
         * Determine page encoding from directive of the form <%@ page %>,
         * <%@ tag %>, <jsp:directive.page > or <jsp:directive.tag >.
         */
        while (true) {
            if (jspReader.skipUntil("<") == null) {
                break;
            }
            // If this is a comment, skip until its end
            if (jspReader.matches("%--")) {
                if (jspReader.skipUntil("--%>") == null) {
                    // error will be caught in Parser
                    break;
                }
                continue;
            }
            boolean isDirective = jspReader.matches("%@");
            if (isDirective) {
                jspReader.skipSpaces();
            }
            else {
                isDirective = jspReader.matches("jsp:directive.");
            }
            if (!isDirective) {
                continue;
            }

            // compare for "tag ", so we don't match "taglib"
            if (jspReader.matches("tag ") || jspReader.matches("page")) {

                jspReader.skipSpaces();
                Attributes attrs = Parser.parseAttributes(this, jspReader);
                encoding = getPageEncodingFromDirective(attrs, "pageEncoding");
                if (encoding != null) {
                    break;
                }
                encoding = getPageEncodingFromDirective(attrs, "contentType");
                if (encoding != null) {
                    saveEncoding = encoding;
                }
            }
        }

        if (encoding == null) {
            encoding = saveEncoding;
        }

        return encoding;
    }

    /*
     * Scans the given attributes for the attribute with the given name,
     * which is either 'pageEncoding' or 'contentType', and returns the
     * specified page encoding.
     *
     * In the case of 'contentType', the page encoding is taken from the
     * content type's 'charset' component.
     *
     * @param attrs The page directive attributes
     * @param attrName The name of the attribute to search for (either
     * 'pageEncoding' or 'contentType')
     *
     * @return The page encoding, or null
     */
    private String getPageEncodingFromDirective(Attributes attrs,
            String attrName) {
        String value = attrs.getValue(attrName);
        if (attrName.equals("pageEncoding")) {
            return value;
        }

        // attrName = contentType
        String contentType = value;
        String encoding = null;
        if (contentType != null) {
            int loc = contentType.indexOf(CHARSET);
            if (loc != -1) {
                encoding = contentType.substring(loc + CHARSET.length());
            }
        }

        return encoding;
    }

    /*
     * Resolve the name of the file and update baseDirStack() to keep track of
     * the current base directory for each included file.
     * The 'root' file is always an 'absolute' path, so no need to put an
     * initial value in the baseDirStack.
     */
    private String resolveFileName(String inFileName) {
        String fileName = inFileName.replace('\\', '/');
        String baseDir =
                fileName.substring(0, fileName.lastIndexOf("/") + 1);
        baseDirStack.push(baseDir);
        return fileName;
    }

    /*
     * Checks to see if the given page contains, as its first element, a <root>
     * element whose prefix is bound to the JSP namespace, as in:
     *
     * <wombat:root xmlns:wombat="http://java.sun.com/JSP/Page" version="1.2">
     *   ...
     * </wombat:root>
     *
     * @param reader The reader for this page
     *
     * @return true if this page contains a root element whose prefix is bound
     * to the JSP namespace, and false otherwise
     */
    private boolean hasJspRoot(JspReader reader) throws JasperException {

        // <prefix>:root must be the first element
        Mark start = null;
        while ((start = reader.skipUntil("<")) != null) {
            int c = reader.nextChar();
            if (c != '!' && c != '?') break;
        }
        if (start == null) {
            return false;
        }
        Mark stop = reader.skipUntil(":root");
        if (stop == null) {
            return false;
        }
        // call substring to get rid of leading '<'
        String prefix = reader.getText(start, stop).substring(1);

        start = stop;
        stop = reader.skipUntil(">");
        if (stop == null) {
            return false;
        }

        // Determine namespace associated with <root> element's prefix
        String root = reader.getText(start, stop);
        String xmlnsDecl = "xmlns:" + prefix;
        int index = root.indexOf(xmlnsDecl);
        if (index == -1) {
            return false;
        }
        index += xmlnsDecl.length();
        while (index < root.length()
                && Character.isWhitespace(root.charAt(index))) {
            index++;
        }
        if (index < root.length() && root.charAt(index) == '=') {
            index++;
            while (index < root.length()
                    && Character.isWhitespace(root.charAt(index))) {
                index++;
            }
            if (index < root.length() && root.charAt(index++) == '"'
                && root.regionMatches(index, JSP_URI, 0,
                        JSP_URI.length())) {
                return true;
            }
        }

        return false;
    }

    private JarFile getJarFile(URL jarFileUrl) throws IOException {
        JarFile jarFile = null;

        if (jarFileUrl != null) {
            JarURLConnection conn = (JarURLConnection) jarFileUrl.openConnection();
            conn.setUseCaches(false);
            conn.connect();
            jarFile = conn.getJarFile();
        }

        return jarFile;
    }

}
