/*
 * Copyright (c) 2003, KNOPFLERFISH project
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following
 * conditions are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials
 *   provided with the distribution.
 *
 * - Neither the name of the KNOPFLERFISH project nor the names of its
 *   contributors may be used to endorse or promote products derived
 *   from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.knopflerfish.bundle.http;

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.InputStream;
import java.util.Stack;
import java.util.Dictionary;
import java.util.Hashtable;
import java.net.URLConnection;
import java.net.URL;

import javax.servlet.RequestDispatcher;
import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.SingleThreadModel;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.osgi.service.http.HttpContext;


public class RequestDispatcherImpl implements RequestDispatcher {

  // private constants

  private final static Dictionary threadStacks = new Hashtable();


  // private fields

  private final String servletPath;
  private final Servlet servlet;
  private final HttpContext httpContext;
  private final ServletConfig config;

  private String uri = null;
  private String queryString = null;
  private String pathInfo = null;


  // constructors

  RequestDispatcherImpl(final String servletPath,
                        final Servlet servlet,
                        final HttpContext httpContext) {
    this(servletPath, servlet, httpContext, null);
  }

  RequestDispatcherImpl(final String servletPath,
                        final Servlet servlet,
                        final HttpContext httpContext,
                        final ServletConfig config) {

    this.servletPath = servletPath;
    this.servlet = servlet;
    this.httpContext = httpContext;
    this.config = config;
  }


  // private methods

  private void service(HttpServletRequest request, HttpServletResponse response)
      throws IOException, ServletException {

    if (httpContext.handleSecurity(request, response)) {

      Thread t = Thread.currentThread();
      Stack usedURIStack = (Stack) threadStacks.get(t);
      if (usedURIStack == null) {
        usedURIStack = new Stack();
        threadStacks.put(t, usedURIStack);
      }
      String uri =
          (String) request.getAttribute("javax.servlet.include.request_uri");
      if (uri == null)
        uri = request.getRequestURI();
      if (usedURIStack.contains(uri))
        throw new ServletException("Recursive include of \"" + uri + "\"");

      usedURIStack.push(uri);
      try {
        if (servlet instanceof SingleThreadModel) {
          synchronized (servlet) {
            if (config == null)
              servlet.service(request, response);
            else
              serviceResource(request, response, config);
          }
        } else {
          if (config == null)
            servlet.service(request, response);
          else
            serviceResource(request, response, config);
        }
      } finally {
        usedURIStack.pop();
        if (usedURIStack.empty())
          threadStacks.remove(t);
      }

    }
  }

  private void serviceResource(HttpServletRequest request,
                               HttpServletResponse response,
                               ServletConfig config)
      throws IOException {

    String uri = (String) request.getAttribute("javax.servlet.include.request_uri");
    if (uri == null)
      uri = request.getRequestURI();

    if (uri.endsWith(".shtml")) {
      serviceSSIResource(uri, response, config);
    } else {

      String target = uri.substring(servletPath.length());
      ServletContext context = config.getServletContext();
      URL url = context.getResource(target);
      URLConnection resource = url.openConnection();

      String contentType = context.getMimeType(uri);
      if (contentType == null)
        contentType = resource.getContentType();
      if (contentType != null) {
        String encoding = resource.getContentEncoding();
        if (encoding != null)
          contentType += "; charset=" + encoding;
        response.setContentType(contentType);
      }

      int contentLength = resource.getContentLength();
      if (contentLength > 0)
        response.setContentLength(contentLength);

      InputStream is = resource.getInputStream();
      OutputStream os = response.getOutputStream();

      int bytesRead = 0;
      byte buffer[] = new byte[512];
      while ((bytesRead = is.read(buffer)) != -1)
        os.write(buffer, 0, bytesRead);

      is.close();
    }
  }

  private void serviceSSIResource(String uri,
                                  HttpServletResponse response,
                                  ServletConfig config)
      throws IOException {

    String target = uri.substring(servletPath.length());
    ServletContext context = config.getServletContext();

    String contentType = context.getMimeType(uri);
    if (contentType != null)
      response.setContentType(contentType);

    ServletOutputStream os = response.getOutputStream();
    try {
      parseHtml(target,
                context,
                os,
                new Stack());
    } catch (IOException ioe) {
      throw ioe;
    } catch (Exception e) {
      os.print("<b><font color=\"red\">SSI Error: " + e + "</font></b>");
    }
  }

  private void parseHtml(String uri,
                         ServletContext context,
                         ServletOutputStream os,
                         Stack usedFiles) throws IOException {

    if (usedFiles.contains(uri)) {
      os.print("<b><font color=\"red\">SSI Error: Recursive include: " + uri + "</font></b>");
      return;
    }
    usedFiles.push(uri);
    InputStream raw;
    try {
      raw = context.getResourceAsStream(uri);
    } catch (Exception e) {
      raw = null;
    }
    if (raw == null) {
      os.print("<b><font color=\"red\">SSI Error: Error reading file: " + uri + "</font></b>");
      return;
    }
    InputStream is = new BufferedInputStream(raw);

    byte c;
    boolean tagBegin = false;
    StringBuffer buf = new StringBuffer(20);
    while ((c = (byte) is.read()) != -1) {
      if (c == '<') {
        buf.setLength(0);
        tagBegin = true;
      } else if (tagBegin && c == '>') {
        String restOfTag = buf.toString();

        final String ssi_pattern = "!--#";
        if (restOfTag.length() > ssi_pattern.length() &&
            restOfTag.startsWith(ssi_pattern)) { // is this an ssi tag?
          restOfTag = restOfTag.substring(ssi_pattern.length());

          final String include_pattern = "include";
          if (restOfTag.length() > include_pattern.length() &&
              restOfTag.startsWith(include_pattern)) { // is this an include directive?
            restOfTag = restOfTag.substring(include_pattern.length());

            final String file_pattern = "file=\"";
            int index = restOfTag.indexOf(file_pattern);
            if (index > 0 &&
                Character.isWhitespace(restOfTag.charAt(0))) {
              restOfTag = restOfTag.substring(index + file_pattern.length());
              String file = restOfTag.substring(0, restOfTag.indexOf('\"'));
              parseHtml(uri.substring(0, uri.lastIndexOf("/") + 1) + file,
                        context,
                        os,
                        usedFiles);
            } else {
              os.print("<b><font color=\"red\">SSI Error: Unsupported directive</font></b>");
            }
          } else {
            os.print("<b><font color=\"red\">SSI Error: Unsupported directive</font></b>");
          }
        } else {
          os.print('<');
          os.print(restOfTag);
          os.print('>');
        }

        tagBegin = false;
      } else if (tagBegin) {
        buf.append((char) c);
      } else {
        os.write(c);
      }
    }

    is.close();
    usedFiles.pop();
  }


  // public methods

  public String getServletPath() {
    return servletPath;
  }

  public Servlet getServlet() {
    return servlet;
  }

  public HttpContext getHttpContext() {
    return httpContext;
  }

  public void setURI(String uri) {

    int index = uri.indexOf('?');
    if (index != -1) {
      this.uri = uri.substring(0, index);
      this.queryString = uri.substring(index + 1);
    } else {
      this.uri = uri;
      this.queryString = null;
    }

    String decodedURI = HttpUtil.decodeURLEncoding(uri);
    if (decodedURI != null &&
        decodedURI.length() > servletPath.length() &&
        decodedURI.startsWith(servletPath))
      this.pathInfo = decodedURI.substring(servletPath.length());
    else
      this.pathInfo = null;
  }


  // implements RequestDispatcher

  public void forward(ServletRequest request, ServletResponse response)
      throws IOException, ServletException {

    if (!(request instanceof HttpServletRequest &&
          response instanceof HttpServletResponse))
      throw new ServletException("Must be http request");

    if (response.isCommitted())
      throw new IllegalStateException("Cannot forward request after response is committed");
    else
      response.reset();

    service((HttpServletRequest) request, (HttpServletResponse) response);

    response.flushBuffer();
  }

  public void include(ServletRequest request, ServletResponse response)
      throws IOException, ServletException {

    if (!(request instanceof HttpServletRequest &&
          response instanceof HttpServletResponse))
      throw new ServletException("Must be http request");

    HttpServletRequest wrappedRequest =
        new RequestWrapper((HttpServletRequest) request);
    HttpServletResponse wrappedResponse =
        new ResponseWrapper((HttpServletResponse) response);

    wrappedRequest.setAttribute("javax.servlet.include.request_uri", uri);
    wrappedRequest.setAttribute("javax.servlet.include.context_path", "");
    wrappedRequest.setAttribute("javax.servlet.include.servlet_path",
                                servletPath);
    if (pathInfo != null)
      wrappedRequest.setAttribute("javax.servlet.include.path_info", pathInfo);
    if (queryString != null)
      wrappedRequest.setAttribute("javax.servlet.include.query_string",
                                  queryString);

    service(wrappedRequest, wrappedResponse);

    response.flushBuffer();
  }

} // RequestDispatcherImpl