/*
 * 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.BufferedInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.ArrayDeque;
import java.util.Deque;

import org.apache.jasper.JasperException;
import org.apache.jasper.JspCompilationContext;
import org.apache.tomcat.Jar;
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.
 */
public class ParserController implements TagConstants {

    private static final String CHARSET = "charset=";
    private static final String TAGS_IN_JAR_LOCATION = "/META-INF/tags/";

    private final JspCompilationContext ctxt;
    private final Compiler compiler;
    private final 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 final Deque<String> baseDirStack = new ArrayDeque<>();

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

    private String sourceEnc;

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

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

    /**
     * Returns the JSP compilation context associated with this parser controller.
     *
     * @return the JSP compilation context
     */
    public JspCompilationContext getJspCompilationContext() {
        return ctxt;
    }

    /**
     * Returns the compiler associated with this parser controller.
     *
     * @return the compiler
     */
    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.
     *
     * @return The parsed nodes
     *
     * @throws JasperException If an error occurs during parsing
     * @throws IOException     If an I/O error occurs such as the file not being found
     */
    public Node.Nodes parse(String inFileName) throws 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.getTagFileJar());
    }

    /**
     * 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.
     *
     * @return The parsed directive nodes
     *
     * @throws JasperException If an error occurs during parsing
     * @throws IOException     If an I/O error occurs such as the file not being found
     */
    public Node.Nodes parseDirectives(String inFileName) throws 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.getTagFileJar());
    }


    /**
     * 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 jar        The JAR file from which to read the included resource, or null of the included resource is to
     *                       be read from the filesystem
     *
     * @return The parsed nodes
     *
     * @throws JasperException If an error occurs during parsing
     * @throws IOException     If an I/O error occurs such as the file not being found
     */
    public Node.Nodes parse(String inFileName, Node parent, Jar jar) throws JasperException, IOException {
        // For files that are statically included, isTagfile and directiveOnly
        // remain unchanged.
        return doParse(inFileName, parent, jar);
    }

    /**
     * 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 jar        The location of the tag file.
     *
     * @return The parsed tag file nodes
     *
     * @throws JasperException If an error occurs during parsing
     * @throws IOException     If an I/O error occurs such as the file not being found
     */
    public Node.Nodes parseTagFileDirectives(String inFileName, Jar jar) throws JasperException, IOException {
        boolean isTagFileSave = isTagFile;
        boolean directiveOnlySave = directiveOnly;
        isTagFile = true;
        directiveOnly = true;
        Node.Nodes page = doParse(inFileName, null, jar);
        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 jar        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
     */
    @SuppressWarnings("null") // jar can't be null if processingTagInJar is true
    private Node.Nodes doParse(String inFileName, Node parent, Jar jar)
            throws FileNotFoundException, JasperException, IOException {

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

        boolean processingTagInJar = jar != null && baseDirStack.peekFirst() != null &&
                baseDirStack.peekFirst().startsWith(TAGS_IN_JAR_LOCATION);
        String absFileName = null;
        try {
            absFileName = resolveFileName(inFileName);
        } catch (URISyntaxException e) {
            err.jspError("jsp.error.invalid.includeInTagFileJar", inFileName, jar.getJarFileURL().toString());
        }
        if (processingTagInJar && !absFileName.startsWith(TAGS_IN_JAR_LOCATION)) {
            /*
             * An included file is being parsed that was included from the standard location for tag files in JAR but
             * tries to escape that location to either somewhere in the JAR not under the standard location or outside
             * the JAR. Neither of these are permitted.
             */
            err.jspError("jsp.error.invalid.includeInTagFileJar", inFileName, jar.getJarFileURL().toString());
        }
        String jspConfigPageEnc = getJspConfigPageEncoding(absFileName);

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

        if (parent != null) {
            // Included resource, add to dependent list
            if (jar == null) {
                compiler.getPageInfo().addDependant(absFileName, ctxt.getLastModified(absFileName));
            } else {
                String entry = absFileName.substring(1);
                compiler.getPageInfo().addDependant(jar.getURL(entry), Long.valueOf(jar.getLastModified(entry)));

            }
        }

        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, jar, parent, isTagFile, directiveOnly, sourceEnc,
                    jspConfigPageEnc, isEncodingSpecifiedInProlog, isBomPresent);
        } else {
            // Standard syntax
            try (InputStreamReader inStreamReader = JspUtil.getReader(absFileName, sourceEnc, jar, ctxt, err, skip)) {
                JspReader jspReader = new JspReader(ctxt, absFileName, inStreamReader, err);
                parsedPage = Parser.parse(this, jspReader, parent, isTagFile, directiveOnly, jar, sourceEnc,
                        jspConfigPageEnc, isDefaultPageEncoding, isBomPresent);
            }
        }

        baseDirStack.remove();

        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) {

        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, Jar jar, 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 ...
            EncodingDetector encodingDetector;
            try (BufferedInputStream bis = JspUtil.getInputStream(absFileName, jar, ctxt)) {
                encodingDetector = new EncodingDetector(bis);
            }

            sourceEnc = encodingDetector.getEncoding();
            isEncodingSpecifiedInProlog = encodingDetector.isEncodingSpecifiedInProlog();
            isBomPresent = (encodingDetector.getSkip() > 0);
            skip = encodingDetector.getSkip();

            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;
        try {
            jspReader = new JspReader(ctxt, absFileName, sourceEnc, jar, err);
        } catch (FileNotFoundException ex) {
            throw new JasperException(ex);
        }
        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;
            }

            // Want to match tag and page but not taglib
            if (jspReader.matches("tag") && !jspReader.matches("lib") || 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 encoding = null;
        if (value != null) {
            int loc = value.indexOf(CHARSET);
            if (loc != -1) {
                encoding = value.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) throws URISyntaxException {
        String fileName = inFileName.replace('\\', '/');
        boolean isAbsolute = fileName.startsWith("/");
        if (!isAbsolute) {
            URI uri = new URI(baseDirStack.peekFirst() + fileName);
            fileName = uri.normalize().toString();
        }
        String baseDir = fileName.substring(0, fileName.lastIndexOf('/') + 1);
        baseDirStack.addFirst(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) {

        // <prefix>:root must be the first element
        Mark start;
        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) == '=') {
            do {
                index++;
            } while (index < root.length() && Character.isWhitespace(root.charAt(index)));
            if (index < root.length() && (root.charAt(index) == '"' || root.charAt(index) == '\'')) {
                index++;
                return root.regionMatches(index, JSP_URI, 0, JSP_URI.length());
            }
        }

        return false;
    }
}