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-jdbc4.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 = 2014101204L;

    @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, boolean inGet)
	    throws ServletException {
	    Matcher matcher;
	    if ( pathInfo == null )
		return new NoSuchPath();
	    if ( (matcher=Pattern.compile("/d\\.(\\d{4}-\\d{2}-\\d{2})\\.(\\d{4})(?:\\.([\\p{Alnum}\\-]*))?\\.html").matcher(pathInfo)).matches() ) {
		final String date;
		final int number;
		final String extra;
		try {
		    date = matcher.group(1);
		    number = Integer.parseInt(matcher.group(2));
		    extra = matcher.group(3);
		} catch (NumberFormatException e) {
		    return new NoSuchPath();
		}
		try {
		    final Connection conn = WeblogDatabaseConnection.getConnection();
		    final PreparedStatement selSt
			= conn.prepareStatement("SELECT id , extract(epoch from mdate) , special_name FROM entries WHERE edate=? AND id=?");
		    selSt.setString(1,date);
		    selSt.setInt(2,number);
		    final ResultSet selRes = selSt.executeQuery();
		    if ( selRes.next() ) {
			int id = selRes.getInt(1);
			double mdate = selRes.getDouble(2);
			String specialName = selRes.getString(3);
			if ( id != number )
			    throw new ServletException("this cannot happen");
			if ( ! ( ( extra == null && specialName == null )
				 || ( extra != null && specialName != null
				      && extra.equals(specialName) ) ) )
			    return new SingleBlogEntryRedirectPath(date, id, specialName);
			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;
			return new SingleBlogEntryPath(number, lastModified);
		    } else
			return new NoSuchPath();
		} catch (SQLException e) {
		    throw new ServletException(e);
		}
	    }
	    // Legacy support for an old permalink format:
	    if ( inGet && (matcher=Pattern.compile("/d\\.(\\d{4}-\\d{2}-\\d{2})\\.([\\p{Alpha}][\\p{Alnum}\\-]*)\\.html").matcher(pathInfo)).matches() ) {
		final String date;
		final String extra;
		try {
		    date = matcher.group(1);
		    extra = matcher.group(2);
		} catch (NumberFormatException e) {
		    return new NoSuchPath();
		}
		try {
		    final Connection conn = WeblogDatabaseConnection.getConnection();
		    final PreparedStatement selSt
			= conn.prepareStatement("SELECT id FROM entries WHERE edate=? AND special_name=?");
		    selSt.setString(1,date);
		    selSt.setString(2,extra);
		    final ResultSet selRes = selSt.executeQuery();
		    if ( selRes.next() ) {
			int id = selRes.getInt(1);
			return new SingleBlogEntryRedirectPath(date, id, extra);
		    } 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;
	}
    }

    static final class SingleBlogEntryRedirectPath extends RequestPath {
	public String date;
	public int number;
	public String extra;  // May be null (passed to WeblogLink class)
	public SingleBlogEntryRedirectPath(String date, int number, String extra) {
	    this.date = date;
	    this.number = number;
	    this.extra = extra;
	}
    }

    @Override
    public void doGet(HttpServletRequest request,
                      HttpServletResponse response)
        throws IOException, ServletException
    {
	final RequestPath rp = RequestPath.parsePath(request.getPathInfo(), true);
	if ( rp instanceof NoSuchPath ) {
	    response.sendError(HttpServletResponse.SC_NOT_FOUND);
	    return;
	}
	if ( rp instanceof SingleBlogEntryRedirectPath ) {
	    SingleBlogEntryRedirectPath rrp = (SingleBlogEntryRedirectPath)rp;
	    Matcher matcher = Pattern.compile("(\\d{4})-(\\d{2})-(\\d{2})").matcher(rrp.date);
	    if ( ! matcher.matches() )
		throw new AssertionError("bad date format");
	    WeblogLink lk = new WeblogLink(matcher.group(1), matcher.group(2),
					   matcher.group(3),
					   String.format("%04d", rrp.number),
					   "", rrp.extra);
	    lk.setTypeStandard();
	    String basePath = request.getScheme() + "://"
		+ request.getServerName()
		+ ":" + request.getServerPort()
		+ request.getContextPath()
		+ "/";
	    // response.sendRedirect(lk.getFile(basePath));
	    response.setStatus(HttpServletResponse.SC_MOVED_PERMANENTLY);
	    response.setHeader("Location", lk.getFile(basePath));
	    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 {
	    Context.DynamicContext dc = new Context.DynamicContext();
	    dc.modTime = ((SingleBlogEntryPath)rp).lastModified;
	    WeblogSelect.fullProcess(new Context.WeblogSingleSelectionContext(number),
				     dc, 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(), false);
	} catch (Exception e) {
	    return -1;
	}
	if ( rp instanceof SingleBlogEntryPath ) {
	    final long lastModified = ((SingleBlogEntryPath)rp).lastModified;
	    return (lastModified/1000)*1000;
	}
	return -1;
    }
}