/**
 * 
 *     Copyright (C) 2007 Alex Samad (Alex@Samad.com.au)

 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU Lesser General Public License as published by
 the Free Software Foundation; either version 2.1 of the License, or
 (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU Lesser General Public License for more details.

 You should have received a copy of the GNU Lesser General Public License
 along with this program; if not, write to the Free Software
 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 */
package au.com.samad.java.jspwiki.plugin;

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Map;
import java.util.regex.Pattern;

import org.apache.log4j.Logger;

import com.ecyrd.jspwiki.TextUtil;
import com.ecyrd.jspwiki.WikiContext;
import com.ecyrd.jspwiki.plugin.PluginException;
import com.ecyrd.jspwiki.plugin.WikiPlugin;
import com.ecyrd.jspwiki.ui.TemplateManager;

/**
 * Plugin HTTPHeader controls HTTP Header information associated with a Wiki
 * Page<br>
 * <br>
 * This plugin adds a resource to the pages, it adds nothing to the HTML. You
 * can have multiple entries on a pages. The input paramaters are Header and
 * Value<br>
 * <br>
 * Header - is the HTTP Header as defined in rfc2616<br>
 * Value - is the value to assing to the Header, NULL is acceptable in some
 * circumstances and a default value will be used<br>
 * <br>
 * <br>
 * ftp://ftp.isi.edu/in-notes/rfc2616.txt Section 4.2 + 4.5<br>
 * The order in which header fields with differing field names are received is
 * not significant. However, it is "good practice" to send general-header fields
 * first, followed by request-header or response- header fields, and ending with
 * the entity-header fields. <br>
 * Process these headers<br>
 * <br>
 * <br>
 * General Header Fields<br>
 * <li>Cache-Control ; Section 14.9</li>
 * <li>Date ; Section 14.18</li>
 * <li>Pragma ; Section 14.32</li>
 * <br>
 * <br>
 * Response Header Fields<br>
 * <li>Age ; Section 14.6</li>
 * <li>ETag ; Section 14.19</li>
 * <br>
 * Advance features can be control in jspwiki.properties<br>
 * jspwiki.plugin.HTTPHeader.Adv<br>
 * <li>ON : allow advanced features - allows for any header to be set
 * <li>OFF : Only allows the basic features Cache-Control, Date, Pragma, Age,
 * ETag <br>
 * <b>Default is off</b>
 * 
 * @author Alex Samad
 * @version 0.1
 */
public class HTTPHeader implements WikiPlugin {

	/**
	 * Property for HTTPHeader<br>
	 * set in jspwiki.properties<br>
	 * jspwiki.plugin.HTTPHeader.Adv<br>
	 * <li>ON : allow advanced features - allows for any header to be set
	 * <li>OFF : Only allows the basic features Cache-Control, Date, Pragma,
	 * Age, ETag <br>
	 * <b>Default is off</b>
	 */
	public static final String PROP_HTTPheader_ADV = "jspwiki.plugin.HTTPHeader.Adv";

	/*
	 * Flag to allow Advanced features
	 */
	private static Boolean m_Advanced = null;;

	/*
	 * Access to the system logger
	 */
	private static Logger log = Logger.getLogger(HTTPHeader.class);

	/**
	 * The Header being defined
	 */
	public static final String PARAM_HEADER = "header";

	/**
	 * The Value associated with the Header
	 */
	public static final String PARAM_VALUE = "value";

	/**
	 * Gets you access to the advanced features<br>
	 * 0 - no advanced features (default)<br>
	 * 1 - Allow any extra headers and values (Still check the known ones)<br>
	 * 2 - Allow any header with any values - no checking done<br>
	 * Only document this in the code not for general consumption
	 */
	public static final String PARAM_ADVANCED = "advanced";

	/**
	 * Cache Control
	 */
	public static final String HEADER_CACHE_CONTROL = "Cache-Control";

	/**
	 * Date Header
	 */
	public static final String HEADER_DATE = "Date";

	/**
	 * Pragma Header
	 */
	public static final String HEADER_PRAGMA = "Pragma";

	/**
	 * Age header
	 */
	public static final String HEADER_AGE = "Age";

	/**
	 * ETag header
	 */
	public static final String HEADER_ETAG = "ETag";

	/**
	 * @see com.ecyrd.jspwiki.plugin.WikiPlugin
	 * @param context
	 * @param params
	 * @throws PluginException
	 * @return String
	 */
	public String execute(WikiContext context, Map params)
			throws PluginException {
		log.debug("Process HTTPHeader plugin");

		if (!params.containsKey(PARAM_HEADER)) {
			// PARAM_HEADER not defined
			log.info("HTTPHeader called with out " + PARAM_HEADER
					+ " Parameter plugin ignored");
			return null;
		}

		String header = ((String) params.get(PARAM_HEADER)).replaceAll("^ *",
				"").replaceAll(" *$", "");

		String value = null;

		if (params.containsKey(PARAM_VALUE)) {
			// Trim white space at begging &Trim white space at end
			value = ((String) params.get(PARAM_VALUE)).replaceAll("^ *", "")
					.replaceAll(" *$", "");

		}

		if (m_Advanced == null) {
			// Initial advance flag based on value in wikiengine properties file
			// If its not set to the value ON then its off
			m_Advanced = new Boolean(TextUtil.getStringProperty(
					context.getEngine().getWikiProperties(),
					PROP_HTTPheader_ADV, null).compareToIgnoreCase("ON") == 0);
		}

		final int ADVANCED_NO = 0;
		final int ADVANCED_EXTRA = 1;
		final int ADVANCED_PLUS = 2;

		int advanced = ADVANCED_NO;

		if (m_Advanced.booleanValue() && params.containsKey(PARAM_ADVANCED)) {
			advanced = Integer.parseInt((String) params.get(PARAM_ADVANCED));
			log.info("HTTPHeader call with Advanced (" + advanced + ") param "
					+ value == null ? "no value" : "[" + value + "]");
		}

		/*
		 * Big String Switch Statement
		 */
		if (m_Advanced.booleanValue() && advanced == ADVANCED_PLUS) {
			TemplateManager.addResourceRequest(context,
					TemplateManager.RESOURCE_HTTPHEADER, header + ":" + value);
		} else if (header.equalsIgnoreCase(HEADER_CACHE_CONTROL)) {
			processCacheControl(context, value);
		} else if (header.equalsIgnoreCase(HEADER_DATE)) {
			processDate(context, value);
		} else if (header.equalsIgnoreCase(HEADER_PRAGMA)) {
			processPragma(context, value);
		} else if (header.equalsIgnoreCase(HEADER_AGE)) {
			processAge(context, value);
		}

		else if (header.equalsIgnoreCase(HEADER_ETAG)) {
			processETag(context, value);
		}

		else if (m_Advanced.booleanValue() && advanced == ADVANCED_EXTRA) {
			TemplateManager.addResourceRequest(context,
					TemplateManager.RESOURCE_HTTPHEADER, header + ":" + value);

		} else {
			log.info("HTTP Header called with unknown header" + header);
		}

		return null;
	}

	/**
	 * <li>Cache-Control ; Section 14.9</li>
	 * Acceptable values
	 * <li> "no-cache" ; Section 14.9.1</li>
	 * <li> "no-store" ; Section 14.9.2</li>
	 * <li> "max-age" "=" delta-seconds ; Section 14.9.3, 14.9.4</li>
	 * <li> "max-stale" [ "=" delta-seconds ] ; Section 14.9.3</li>
	 * <li> "min-fresh" "=" delta-seconds ; Section 14.9.3</li>
	 * <li> "no-transform" ; Section 14.9.5</li>
	 * <li> "only-if-cached" ; Section 14.9.4</li>
	 * <li> cache-extension ; Section 14.9.6 <B>Not implemented use Advances</b></li>
	 * 
	 * @param context
	 *            wiki context
	 * @param value
	 *            The value passed to this header
	 */
	public void processCacheControl(WikiContext context, String value) {

		if (value != null
				&& Pattern
						.compile(
								"^(no-cache|no-store|max-age *= *\\d*|max-stale(| *= *\\d*)|min-fresh *= *\\d*|no-transform|only-if-cached)$",
								Pattern.CASE_INSENSITIVE).matcher(value).find()) {
			TemplateManager.addResourceRequest(context,
					TemplateManager.RESOURCE_HTTPHEADER, HEADER_CACHE_CONTROL
							+ ": " + value);
			// rfc states that if http/1.1 Cache control = no-cache
			// server should alwo set http/1.0 Pragma no-cache
			if (value.equalsIgnoreCase("no-cache")) {
				processPragma(context, value);
			}
		} else {
			log.info(value + " is not valid for " + HEADER_CACHE_CONTROL);
		}

	}

	/**
	 * <li>Date ; Section 14.18</li>
	 * 
	 * @param context
	 *            wiki context
	 * @param value
	 *            The value passed to this header
	 */

	public void processDate(WikiContext context, String value) {

		if (context.getVariable(TemplateManager.RESOURCE_HTTPHEADER
				+ HEADER_DATE) == null) {
			log.info("Date header already processed for this page");
			return;
		}

		// Format dates according to RFC 822, updated by RFC 1123
		DateFormat httpDateFormat = new SimpleDateFormat(
				"EEE', 'dd' 'MMM' 'yyyy' 'HH:mm:ss' 'Z");

		// Start with the page date
		Date headerDate = context.getRealPage().getLastModified();

		if (value != null) {
			try {
				// If we have a header date us it instead
				headerDate = httpDateFormat.parse(value);
			} catch (ParseException e) {
				log.info("Unable to parse date from " + value);
				log.debug("Using context.getRealPage().getLastModified()");
				headerDate = context.getRealPage().getLastModified();
			}

		}

		// Header timezone should be GMT
		httpDateFormat.setTimeZone(java.util.TimeZone.getTimeZone("GMT"));
		TemplateManager.addResourceRequest(context,
				TemplateManager.RESOURCE_HTTPHEADER, HEADER_DATE + ": "
						+ httpDateFormat.format(headerDate));
		context.setVariable(TemplateManager.RESOURCE_HTTPHEADER + HEADER_DATE,
				"x");

	}

	/**
	 * <li>Pragma ; Section 14.32</li>
	 * 
	 * @param context
	 *            wiki context
	 * @param value
	 *            The value passed to this header
	 */

	public void processPragma(WikiContext context, String value) {

		if (value != null
				&& Pattern.compile(
						"^(no-cache|\\w+ *= *\\w+|\\w+ *= *\".*\")$",
						Pattern.CASE_INSENSITIVE).matcher(value).find()) {
			TemplateManager.addResourceRequest(context,
					TemplateManager.RESOURCE_HTTPHEADER, HEADER_PRAGMA + ": "
							+ value);
		} else {
			log.info(value + " is not valid for " + HEADER_PRAGMA);
		}

	}

	/**
	 * <li>Age ; Section 14.6</li>
	 * 
	 * @param context
	 *            This is the Wiki Context
	 * @param value
	 *            The value for the header
	 */
	public void processAge(WikiContext context, String value) {
		if (context.getVariable(TemplateManager.RESOURCE_HTTPHEADER
				+ HEADER_AGE) == null) {
			log.info("Age header already processed for this page");
			return;
		}

		// Format dates according to RFC 822, updated by RFC 1123
		DateFormat httpDateFormat = new SimpleDateFormat(
				"EEE', 'dd' 'MMM' 'yyyy' 'HH:mm:ss' 'Z");

		// Start with the time in seconds from the lastmodified date to now
		long headerDate = new Date().getTime()
				- context.getRealPage().getLastModified().getTime();

		if (value != null) {
			try {
				// If we have a header date us it instead
				headerDate = httpDateFormat.parse(value).getTime();
			} catch (ParseException e) {
				log.info("Unable to parse date from " + value);
				log
						.debug("Using Date().getTime() - context.getRealPage().getLastModified().getTime()");
				headerDate = new Date().getTime()
						- context.getRealPage().getLastModified().getTime();
			}

		}

		// Header timezone should be GMT
		httpDateFormat.setTimeZone(java.util.TimeZone.getTimeZone("GMT"));
		TemplateManager.addResourceRequest(context,
				TemplateManager.RESOURCE_HTTPHEADER, HEADER_AGE + ": "
						+ headerDate);

		context.setVariable(TemplateManager.RESOURCE_HTTPHEADER + HEADER_DATE,
				"x");

	}

	/**
	 * <li>ETag ; Section 14.19</li>
	 * If value is null, then ETag will equal Wiki.Name Page.Name Page.Version
	 * 
	 * @param context
	 *            This is the Wiki Context
	 * @param value
	 *            The value for the header
	 */
	public void processETag(WikiContext context, String value) {
		if (context.getVariable(TemplateManager.RESOURCE_HTTPHEADER
				+ HEADER_ETAG) == null) {
			log.info("ETag header already processed for this page");
			return;
		}

		TemplateManager.addResourceRequest(context,
				TemplateManager.RESOURCE_HTTPHEADER,
				HEADER_ETAG + ": " + value != null ? value : context
						.getRealPage().getWiki()
						+ "."
						+ context.getRealPage().getName()
						+ "."
						+ context.getRealPage().getVersion());

		context.setVariable(TemplateManager.RESOURCE_HTTPHEADER + HEADER_ETAG,
				"x");

	}
}