package org.apache.cocoon.generation;

import org.apache.avalon.excalibur.pool.Recyclable;
import org.apache.avalon.framework.parameters.Parameters;
import org.apache.avalon.framework.configuration.Configurable;
import org.apache.avalon.framework.configuration.Configuration;
import org.apache.avalon.framework.configuration.ConfigurationException;
import org.apache.cocoon.ProcessingException;
import org.apache.cocoon.ResourceNotFoundException;
import org.apache.cocoon.environment.SourceResolver;
import org.apache.cocoon.Constants;
import org.apache.cocoon.util.Tokenizer;
import org.apache.regexp.RE;
import org.apache.regexp.RESyntaxException;
import org.apache.log.Logger;

import org.xml.sax.SAXException;
import org.xml.sax.helpers.AttributesImpl;

import java.io.IOException;
import java.io.InputStream;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.URLConnection;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Map;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.ArrayList;

/**
 * Generates a list of links that are reachable from the src and their status.
 *
 * @author Michael Homeijer
 */

public class LinkStatusGenerator extends ComposerGenerator implements Recyclable, Configurable {
    /** The URI of the namespace of this generator. */
    protected static final String URI =
        "http://apache.org/cocoon/linkstatus/2.0";

    /** The namespace prefix for this namespace. */
    protected static final String PREFIX = "linkstatus";

    /* Node and attribute names */
    protected static final String TOP_NODE_NAME         = "linkstatus";
    protected static final String LINK_NODE_NAME         = "link";

    protected static final String HREF_ATTR_NAME    = "href";
    protected static final String REFERRER_ATTR_NAME    = "referrer";
    protected static final String CONTENT_ATTR_NAME    = "content";
    protected static final String STATUS_ATTR_NAME    = "status";
    protected static final String MESSAGE_ATTR_NAME    = "message";     

    protected AttributesImpl attributes = new AttributesImpl();

    /**
     * Config element name specifying expected link content-typ.
     * <p>
     *   Its value is <code>link-content-type</code>.
     * </p>
     *
     * @since
     */
    public final static String LINK_CONTENT_TYPE_CONFIG = "link-content-type";

    /**
     * Default value of <code>link-content-type</code> configuration value.
     * <p>
     *   Its value is <code>application/x-cocoon-links</code>.
     * </p>
     *
     * @since
     */
    public final String LINK_CONTENT_TYPE_DEFAULT = "application/x-cocoon-links";
    
    /**
     * Config element name specifying query-string appendend for requesting links
     * of an URL.
     * <p>
     *  Its value is <code>link-view-query</code>.
     * </p>
     *
     * @since
     */
    public final static String LINK_VIEW_QUERY_CONFIG = "link-view-query";
    /**
     * Default value of <code>link-view-query</code> configuration value.
     * <p>
     *   Its value is <code>?cocoon-view=links</code>.
     * </p>
     *
     * @since
     */
    public final static String LINK_VIEW_QUERY_DEFAULT = "cocoon-view=links";

    /**
     * Config element name specifying excluding regular expression pattern.
     * <p>
     *  Its value is <code>exclude</code>.
     * </p>
     *
     * @since
     */
    public final static String EXCLUDE_CONFIG = "exclude";

    /**
     * Config element name specifying including regular expression pattern.
     * <p>
     *  Its value is <code>include</code>.
     * </p>
     *
     * @since
     */
    public final static String INCLUDE_CONFIG = "include";

    /**
     * Config element name specifying http header value for user-Agent.
     * <p>
     *  Its value is <code>user-agent</code>.
     * </p>
     *
     * @since
     */
    public final static String USER_AGENT_CONFIG = "user-agent";
    /**
     * Default value of <code>user-agent</code> configuration value.
     * <p>
     *   Its value is @see org.apache.cocoon.Constants#COMPLETE_NAME.
     * </p>
     *
     * @since
     */
    public final static String USER_AGENT_DEFAULT = Constants.COMPLETE_NAME;

    /**
     * Config element name specifying http header value for accept.
     * <p>
     *  Its value is <code>accept</code>.
     * </p>
     *
     * @since
     */
    public final static String ACCEPT_CONFIG = "accept";
    /**
     * Default value of <code>accept</code> configuration value.
     * <p>
     *   Its value is <code>* / *</code>
     * </p>
     *
     * @since
     */
    public final static String ACCEPT_DEFAULT = "*/*";

    private String linkViewQuery = LINK_VIEW_QUERY_DEFAULT;
    private String linkContentType = LINK_CONTENT_TYPE_DEFAULT;
    private HashSet excludeCrawlingURL;
    private HashSet includeCrawlingURL;
    private String userAgent = USER_AGENT_DEFAULT;
    private String accept = ACCEPT_DEFAULT;

    private HashSet crawled;
    private HashSet linksToProcess;

    /**
     * Stores links to process and the referrer links
     */

    private class Link {
        private URL url;
        private String referrer;

        public Link( URL url, String referrer ) {
            this.url = url;
            this.referrer = referrer;
        }

        public URL getURL() {
            return url;
        }

        public String getReferrer() {
            return referrer;
        }

        public boolean equals( Link l ) {
            return url.equals( l.getURL());
        }
    }

    /**
     * Configure the crawler component.
     * <p>
     *  Configure can specify which URI to include, and which URI to exclude
     *  from crawling. You specify the patterns as regular expressions.
     * </p>
     * <p>
     *  Morover you can configure
     *  the required content-type of crawling request, and the
     *  query-string appended to each crawling request.
     * </p>
     * <pre><tt>
     * &lt;include&gt;.*\.html?&lt;/exclude&gt; or &lt;exclude&gt;.*\.html?, .*\.xsp&lt;/exclude&gt;
     * &lt;exclude&gt;.*\.gif&lt;/exclude&gt; or &lt;exclude&gt;.*\.gif, .*\.jpe?g&lt;/exclude&gt;
     * &lt;link-content-type&gt; application/x-cocoon-links &lt;/link-content-type&gt;
     * &lt;link-view-query&gt; ?cocoon-view=links &lt;/link-view-query&gt;
     * </tt></pre>
     *
     * @param  configuration               XML configuration of this avalon component.
     * @exception  ConfigurationException  is throwing if configuration is invalid.
     * @since
     */
    public void configure(Configuration configuration)
        throws ConfigurationException {

        Configuration[] children;
        children = configuration.getChildren(INCLUDE_CONFIG);
        if (children != null && children.length > 0) {
            includeCrawlingURL = new HashSet();
            for (int i = 0; i < children.length; i++) {
                String pattern = children[i].getValue();
                try {
                    Tokenizer t = new Tokenizer(pattern, ", ");
                    while (t.hasMoreTokens()) {
                        String tokenized_pattern = t.nextToken();
                        this.includeCrawlingURL.add(new RE(tokenized_pattern));
                    }
                } catch (RESyntaxException rese) {
                    getLogger().error("Cannot create includeing regular-expression for " + 
                                      pattern, rese);
                }
            }
        }

        children = configuration.getChildren(EXCLUDE_CONFIG);
        if (children != null && children.length > 0) {
            excludeCrawlingURL = new HashSet();
            for (int i = 0; i < children.length; i++) {
                String pattern = children[i].getValue();
                try {
                    Tokenizer t = new Tokenizer(pattern, ", ");
                    while (t.hasMoreTokens()) {
                        String tokenized_pattern = t.nextToken();
                        this.excludeCrawlingURL.add(new RE(tokenized_pattern));
                    }
                } catch (RESyntaxException rese) {
                    getLogger().error("Cannot create excluding regular-expression for " + 
                                      pattern, rese);
                }
            }
        } else {
            excludeCrawlingURL = new HashSet();
            setDefaultExcludeFromCrawling();
        }

        Configuration child;
        String value;
        child = configuration.getChild(LINK_CONTENT_TYPE_CONFIG, false);
        if (child != null) {
            value = child.getValue();
            if (value != null && value.length() > 0) {
                this.linkContentType = value.trim();
            }
        }
        child = configuration.getChild(LINK_VIEW_QUERY_CONFIG, false);
        if (child != null) {
            value = child.getValue();
            if (value != null && value.length() > 0) {
                this.linkViewQuery = value.trim();
            }
        }

        child = configuration.getChild(USER_AGENT_CONFIG, false);
        if (child != null) {
            value = child.getValue();
            if (value != null && value.length() > 0) {
                this.userAgent = value;
            }
        }

        child = configuration.getChild(ACCEPT_CONFIG, false);
        if (child != null) {
            value = child.getValue();
            if (value != null && value.length() > 0) {
                this.accept = value;
            }
        }
    }

    public void setup(SourceResolver resolver, Map objectModel, String src, Parameters par)
        throws ProcessingException, SAXException, IOException {

        super.setup(resolver, objectModel, src, par);

        /* Create a reusable attributes for creating nodes */
        this.attributes = new AttributesImpl();

        excludeCrawlingURL = new HashSet();
        this.setDefaultExcludeFromCrawling();
    }

    /**
     * Generate XML data.
     *
     * @throws  SAXException
     *      if an error occurs while outputting the document
     * @throws  ProcessingException
     *      if the requsted URI wasn't found
     */
    public void generate()
        throws SAXException, ProcessingException {
        try {

            crawled = new HashSet();
            linksToProcess = new HashSet();

            URL root = new URL(source);
            linksToProcess.add(new Link( root, ""));


            if (getLogger().isDebugEnabled()) {
                getLogger().debug("crawl URL " + root);
            }

            this.contentHandler.startDocument();
            this.contentHandler.startPrefixMapping(PREFIX,URI);

            attributes.clear();
            super.contentHandler.startElement(URI, TOP_NODE_NAME, URI+':'+TOP_NODE_NAME, attributes);

            while (linksToProcess.size() > 0) {
                Iterator i = linksToProcess.iterator();

                if (i.hasNext()) {
                    // fetch a URL
                    Link link = (Link) i.next();
                    URL url = link.getURL();            

                    // remove it from the to-do list
                    linksToProcess.remove(link);

                    URLConnection conn = processURL(url, link.getReferrer());

                    // calc all links from this url
                    if (conn != null) {

                        List url_links = getLinksFromConnection(conn, url);
                        if (url_links != null) {
                            // add links of this url to the to-do list
                            linksToProcess.addAll(url_links);
                        }
                    }
                }
            }

            super.contentHandler.endElement(URI, TOP_NODE_NAME, URI+':'+TOP_NODE_NAME);
            this.contentHandler.endPrefixMapping(PREFIX);
            this.contentHandler.endDocument();
        } catch (IOException ioe) {
            getLogger().warn("Could not read source ", ioe);
            throw new ResourceNotFoundException("Could not read source ", ioe);
        }
    }

    /**
     * Default exclude patterns.
     * <p>
     *   By default URLs matching following patterns are excluded:
     * </p>
     * <ul>
     *   <li>.*\\.gif(\\?.*)?$ - exclude gif images</li>
     *   <li>.*\\.png(\\?.*)?$ - exclude png images</li>
     *   <li>.*\\.jpe?g(\\?.*)?$ - exclude jpeg images</li>
     *   <li>.*\\.js(\\?.*)?$ - exclude javascript </li>
     *   <li>.*\\.css(\\?.*)?$ - exclude cascaded stylesheets</li>
     * </ul>
     *
     * @since
     */
    private void setDefaultExcludeFromCrawling() {
        String[] EXCLUDE_FROM_CRAWLING_DEFAULT = {
            ".*\\.gif(\\?.*)?$",
            ".*\\.png(\\?.*)?$",
            ".*\\.jpe?g(\\?.*)?$",
            ".*\\.js(\\?.*)?$",
            ".*\\.css(\\?.*)?$"
        };

        for (int i = 0; i < EXCLUDE_FROM_CRAWLING_DEFAULT.length; i++) {
            String pattern = EXCLUDE_FROM_CRAWLING_DEFAULT[i];
            try {
                excludeCrawlingURL.add(new RE(pattern));
            } catch (RESyntaxException rese) {
                getLogger().error("Cannot create excluding regular-expression for " +
                                  pattern, rese);
            }
        }
    }


    protected List getLinksFromConnection(URLConnection conn, URL url) {
        List url_links = null;
        try {
            String content_type = conn.getContentType();

            if (getLogger().isDebugEnabled()) {
                getLogger().debug("Content-type: " + content_type);
            }

            if (content_type.equals(linkContentType)) {
                url_links = new ArrayList();

                InputStream is = conn.getInputStream();
                BufferedReader br = new BufferedReader(new InputStreamReader(is));

                // content is supposed to be a list of links,
                // relative to current URL
                String line;
                String referrer = url.toString();

                while ((line = br.readLine()) != null) {
                    URL new_url = new URL(url, line);
                    boolean add_url = true;
                    // don't add new_url twice
                    if (add_url) {
                        add_url &= !url_links.contains(new_url);
                    }

                    // don't add new_url if it has been crawled already
                    if (add_url) {
                        add_url &= !crawled.contains(new_url.toString());
                    }

                    Link new_link = new Link( new_url, referrer );
                    if (add_url) {
                        add_url &= !linksToProcess.contains(new_link);
                    }

                    // don't add if is not matched by existing include definition
                    if (add_url) {
                        add_url &= isIncludedURL(new_url.toString());
                    }

                    if (add_url) {
                        if (getLogger().isDebugEnabled()) {
                            getLogger().debug("Add URL: " + new_url.toString());
                        }
                        url_links.add(new_link);
                    }
                }
                // now we have a list of URL which should be examined
            }
        } catch (IOException ioe) {
            getLogger().warn("Problems get links of " + url, ioe);
        }
        return url_links;
    }

    protected URLConnection processURL(URL url, String referrer) throws SAXException {

        if (getLogger().isDebugEnabled()) {
            getLogger().debug("getLinks URL " + url);
        }

        URLConnection result = null;

        // don't try to investigate url which has been crawled already
        if (crawled.contains(url.toString())) {
            return null;
        }

        // mark it as crawled
        crawled.add(url.toString());

        attributes.clear();
        attributes.addAttribute("", HREF_ATTR_NAME,
                                HREF_ATTR_NAME, "CDATA", url.toString());
        attributes.addAttribute("", REFERRER_ATTR_NAME,
                                REFERRER_ATTR_NAME, "CDATA", referrer);

        // don't try to get links for url which is excluded from crawling
        if (isExcludedURL(url.toString())) {
            // Check for status and output it.

            try {
                URLConnection links_url_connection = url.openConnection();
                HttpURLConnection h = (HttpURLConnection)links_url_connection;
                String content_type = links_url_connection.getContentType();

                attributes.addAttribute("", CONTENT_ATTR_NAME,
                                        CONTENT_ATTR_NAME, "CDATA",
                                        content_type);

                attributes.addAttribute("", MESSAGE_ATTR_NAME,
                                        MESSAGE_ATTR_NAME, "CDATA",
                                        h.getResponseMessage());

                attributes.addAttribute("", STATUS_ATTR_NAME,
                                        STATUS_ATTR_NAME, "CDATA",
                                        String.valueOf(h.getResponseCode()));



            }
            catch (IOException ioe)
                {
                    attributes.addAttribute("", MESSAGE_ATTR_NAME,
                                            MESSAGE_ATTR_NAME, "CDATA",
                                            ioe.getMessage());
                }
                
        } else {

            // Output url, referrer, content-type, status, message for traversable url's
            // add prefix and query to get data from the linkserializer.        
            try {
                URL links_url = new URL(url, url.getPath()
                                        + ((url.getPath().indexOf("?") == -1) ? "?" : "&") 
                                        + linkViewQuery);
                URLConnection links_url_connection = links_url.openConnection();
                HttpURLConnection h = (HttpURLConnection)links_url_connection;

                result = links_url_connection;

                attributes.addAttribute("", CONTENT_ATTR_NAME,
                                        CONTENT_ATTR_NAME, "CDATA",
                                        links_url_connection.getContentType());

                attributes.addAttribute("", MESSAGE_ATTR_NAME,
                                        MESSAGE_ATTR_NAME, "CDATA",
                                        h.getResponseMessage());

                attributes.addAttribute("", STATUS_ATTR_NAME,
                                        STATUS_ATTR_NAME, "CDATA",
                                        String.valueOf(h.getResponseCode()));
            }
            catch(IOException ioe ) {
                // Output url referrer status message
                attributes.addAttribute("", MESSAGE_ATTR_NAME,
                                        MESSAGE_ATTR_NAME, "CDATA",
                                        ioe.getMessage());

        
            }
        }
        super.contentHandler.startElement(URI, LINK_NODE_NAME, URI+':'+LINK_NODE_NAME, attributes);
        super.contentHandler.endElement(URI, LINK_NODE_NAME, URI+':'+LINK_NODE_NAME);
        
        return result;
    }

    /**
     * check if URL is a candidate for indexing
     *
     * @param  url  Description of Parameter
     * @return      The excludedURL value
     * @since
     */
    private boolean isExcludedURL(String url) {
        // by default include URL for crawling
        if (excludeCrawlingURL == null) {
            if (getLogger().isDebugEnabled()) {
                getLogger().debug("exclude no URL " + url);
            }
            return false;
        }

        final String s = url.toString();
        Iterator i = excludeCrawlingURL.iterator();
        while (i.hasNext()) {
            RE pattern = (RE) i.next();
            if (pattern.match(s)) {
                if (getLogger().isDebugEnabled()) {
                    getLogger().debug("exclude URL " + url);
                }
                return true;
            }
        }
        if (getLogger().isDebugEnabled()) {
            getLogger().debug("exclude not URL " + url);
        }
        return false;
    }


    /**
     * check if URL is a candidate for indexing
     *
     * @param  url  Description of Parameter
     * @return      The includedURL value
     * @since
     */
    private boolean isIncludedURL(String url) {
        // by default include URL for crawling
        if (includeCrawlingURL == null) {
            if (getLogger().isDebugEnabled()) {
                getLogger().debug("include all URL " + url);
            }
            return true;
        }

        final String s = url.toString();
        Iterator i = includeCrawlingURL.iterator();
        while (i.hasNext()) {
            RE pattern = (RE) i.next();
            if (pattern.match(s)) {
                if (getLogger().isDebugEnabled()) {
                    getLogger().debug("include URL " + url);
                }
                return true;
            }
        }
        if (getLogger().isDebugEnabled()) {
            getLogger().debug("include not URL " + url);
        }
        return false;
    }

    public void recycle() {
        super.recycle();

        this.attributes = null;
        this.excludeCrawlingURL = null;
    }
}