package org.madore.damlengine;

import java.util.regex.Pattern;
import java.util.regex.Matcher;
import java.util.Properties;
import java.util.Enumeration;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.file.Paths;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/* Thinkos about the mess that is tomcat:

 * - Make sure that /usr/share/java/postgresql-jdbc3.jar (or whatever
 *   contains the class org.postgresql.Driver) is symlinked from
 *   /var/lib/tomcat7/common (or some path listed in the common.loader
 *   property of the catalina.properties file).  Similarly,
 *   xercesImpl.jar and probably xml-resolver.jar need to be linked.

 * - The following parameters need to be defined in <init-param> tags
 *   inside the <servlet> block: base_path, template_path, pghost,
 *   pgport, dbname, pguser and pgpass or pgpassfile.

 */

public class WeblogServlet extends HttpServlet {

    private static final long serialVersionUID = 2014100704L;

    @Override
    public void init(ServletConfig cfg)
	throws ServletException
    {
	super.init(cfg);  // Important!
	synchronized ( DamlEngine.class ) { if ( DamlEngine.appProps == null ) {
	    DamlEngine.runAsServlet = true;
	    DamlEngine.appProps = new Properties();
	    for (Enumeration<String> e = cfg.getInitParameterNames() ; e.hasMoreElements() ; ) {
		String k = e.nextElement();
		DamlEngine.appProps.setProperty(k, cfg.getInitParameter(k));
	    }
	    if ( DamlEngine.appProps.getProperty("base_path") != null )
		DamlEngine.basePath = Paths.get(DamlEngine.appProps.getProperty("base_path"));
	    if ( DamlEngine.basePath == null )
		DamlEngine.basePath = Paths.get(getServletContext().getRealPath("/"));
	    if ( DamlEngine.appProps.getProperty("template_path") != null )
		DamlEngine.templatePath = Paths.get(DamlEngine.appProps.getProperty("template_path"));
	    if ( DamlEngine.templatePath == null )
		DamlEngine.templatePath = DamlEngine.basePath.resolve("templates");
	}  }
    }

    static abstract class RequestPath {
	public static RequestPath parsePath(String pathInfo)
	    throws ServletException {
	    Matcher matcher;
	    if ( pathInfo == null )
		return new NoSuchPath();
	    if ( (matcher=Pattern.compile("/(\\d{1,7})").matcher(pathInfo)).matches() ) {
		final int number;
		try {
		    number = Integer.parseInt(matcher.group(1));
		} catch (NumberFormatException e) {
		    return new NoSuchPath();
		}
		try {
		    final Connection conn = WeblogDatabaseConnection.getConnection();
		    final PreparedStatement selSt
			= conn.prepareStatement("SELECT id , extract(epoch from mdate) FROM entries WHERE id=?");
		    selSt.setInt(1,number);
		    final ResultSet selRes = selSt.executeQuery();
		    if ( selRes.next() ) {
			int id = selRes.getInt(1);
			double mdate = selRes.getDouble(2);
			if ( id != number )
			    throw new ServletException("this cannot happen");
			long lastModified = (long)(mdate*1000);
			long thisLastModified;
			try {
			    // Attempts to detect when *this* class was last modified.
			    thisLastModified = WeblogServlet.class.getResource("WeblogServlet.class").openConnection().getLastModified();
			} catch (Exception e) {
			    thisLastModified = 0;
			}
			if ( thisLastModified > lastModified )
			    lastModified = thisLastModified;
			// O'Reilly recommends not using milliseconds part:
			lastModified = (lastModified/1000)*1000;
			return new SingleBlogEntryPath(number, lastModified);
		    } else
			return new NoSuchPath();
		} catch (SQLException e) {
		    throw new ServletException(e);
		}
	    }
	    return new NoSuchPath();
	}
    }

    static final class NoSuchPath extends RequestPath { }

    static final class SingleBlogEntryPath extends RequestPath {
	public int number;
	public long lastModified;
	public SingleBlogEntryPath(int number, long lastModified) {
	    this.number = number;
	    this.lastModified = lastModified;
	}
    }

    @Override
    public void doGet(HttpServletRequest request,
                      HttpServletResponse response)
        throws IOException, ServletException
    {
	final RequestPath rp = RequestPath.parsePath(request.getPathInfo());
	if ( rp instanceof NoSuchPath ) {
	    response.sendError(HttpServletResponse.SC_NOT_FOUND);
	    return;
	}
	if ( ! (rp instanceof SingleBlogEntryPath) )
	    throw new ServletException("this cannot happen");
	final int number = ((SingleBlogEntryPath)rp).number;
        response.setContentType("text/html; charset=utf-8");
	response.setCharacterEncoding("UTF-8");
        OutputStream out = response.getOutputStream();
	try {
	    WeblogSelect.fullProcess(new Context.WeblogSingleSelectionContext(number),
				     out);
	} catch (Exception e) {
	    throw new ServletException("exception during WeblogSelect.fullProcess()", e);
	}
    }

    @Override
    public long getLastModified(HttpServletRequest request) {
	final RequestPath rp;
	try {
	    rp = RequestPath.parsePath(request.getPathInfo());
	} catch (Exception e) {
	    return -1;
	}
	if ( rp instanceof SingleBlogEntryPath ) {
	    final long lastModified = ((SingleBlogEntryPath)rp).lastModified;
	    return lastModified;
	}
	return -1;
    }
}