package org.tus.servlet.upload;
 
import java.io.IOException;
import java.security.Principal;

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

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
 
/*
	The servlet_path is configured in servlet mapping in web.xml. 
	If using this servlet in a struts application, in struts.xml tell struts
	to exclude "/servlet_path/[0-9a-zA-Z]*".
	This servlet should only see uris of the form /servlet_path or /servlet_path/123foo , but nothing with
	special characters or deeper paths.  
*/
@SuppressWarnings("serial")
public class Upload extends HttpServlet 
{
	private static final Logger log = LoggerFactory.getLogger(Upload.class.getName());
	private Config config;
	private Composer composer;
	private boolean doTermination;
	private boolean doCreation;
	private boolean doGet;

	@Override
	public void init() throws ServletException
	{
		log.debug("Initialize Upload servlet");
		try
		{
			config = new Config(getServletConfig());
			composer = new Composer(config);
			doTermination = composer.datastore.getExtensions().contains("termination");
			doCreation = composer.datastore.getExtensions().contains("creation");
			doGet = composer.datastore.getExtensions().contains("get");
		}
		catch(ServletException se)
		{
			log.error("", se);
			throw se;
		}
		catch(Exception e)
		{
			log.error("", e);
			throw new ServletException(e);
		}
	}

	@Override
	public void destroy()
	{
		try
		{
			composer.datastore.destroy();
			super.destroy();
		}
		catch(Exception e)
		{
			log.error("", e);
		}
	}

	@Override
	public void service(HttpServletRequest request, HttpServletResponse servletResponse)
		throws IOException, ServletException 
	{
		Response response = new Response(servletResponse);
		try
		{
			log.debug("UPLOAD SERVLET " + request.getMethod() + " " + request.getRequestURL() + ". User = " +
				getAuthenticatedUser(request));

			checkVersion(request, response);

			String method = request.getMethod();
			if (method.equals("OPTIONS"))
			{
				new OptionsHandler(composer, request, response).go();
			} else if (method.equals("HEAD"))
			{
				new HeadHandler(composer, request, response).go();
			} else if (method.equals("PATCH"))
			{
				new PatchHandler(composer, request, response).go();
			} else if (method.equals("POST") && doCreation)
			{
				new PostHandler(composer, request, response).go();
			} else if (method.equals("DELETE") && doTermination)
			{
				new DeleteHandler(composer, request, response).go();
			} else if (method.equals("GET") && doGet)
			{
				new GetHandler(composer, request, response).go();
			}
			else
			{
				log.info("Method " + request.getMethod() + " not allowed.");
				throw new TusException.MethodNotAllowed();
			}
		}
		catch (TusException texc)
		{
			response.setStatus(texc.getStatus()).setText(texc.getText());
		}
		catch(Exception e)
		{
			log.error("", e);
			response.setStatus(500).setText((e.getMessage()  == null) ? 
				"Server Error" : "Server Error: " + e.getMessage());
		}
		send(request, response);
	}

	/*
		User authentication, if needed, is handled outside of the servlet and the information 
		is passed to the servlet via the request.getUserPrincipal().  If a user has been 
		authenticated, request.getUserPrincipal will be non null will contain the user's name.   
		Usually, when using authentication, a filter is configured to prevent the servlet 
		from running if a user hasn't logged in..
	*/
	public static String getAuthenticatedUser(HttpServletRequest request)
	{
		Principal principal = request.getUserPrincipal();
		if (principal != null)
		{
			return principal.getName();
		} 
		return null;
	}

	private void checkVersion(HttpServletRequest request, Response response)
		throws Exception
	{
		String clientVersion = request.getHeader("tus-resumable");

		// OPTIONS and GET don't require tus-resumable version header, everything else does
		if (!request.getMethod().equals("OPTIONS") &&  !request.getMethod().equals("GET") &&  
			(clientVersion == null || !clientVersion.equals(config.tusApiVersionSupported)))
		{
			throw new TusException.UnsupportedVersion();
		}
	}


	private void send(HttpServletRequest request, Response response)
		throws IOException
	{
		response.setHeader("Tus-Resumable", config.tusApiVersionSupported);
		response.setHeader("X-Content-Type-Options", "nosniff");
		addAccessHeaders(request, response);
		if (request.getMethod().equals("HEAD"))
		{
			response.setText("");
		}
		String body = response.getText();
		if (body.length() > 0)
		{
			body += "\n";
			response.setHeader("Content-Type", "text/plain; charset=utf-8");
			response.setHeader("Content-Length", Long.toString(body.length()));
		}
		response.setText(body);
		response.write();
	}

	private void addAccessHeaders(HttpServletRequest request, Response response)
	{
		String origin = request.getHeader("Origin");
		if (origin != null && origin.length() > 0)
		{
			response.setHeader("Access-Control-Allow-Origin", origin);
			if (request.getMethod().equals("OPTIONS"))
			{
				response.setHeader("Access-Control-Allow-Methods", 
					"POST, GET, HEAD, PATCH, DELETE, OPTIONS");
				response.setHeader("Access-Control-Allow-Headers", 
						"Origin, " +
						"X-Requested-With, " +
						"Content-Type, " +
						"Upload-Length, " +
						"Upload-Offset, " +
						"Tus-Resumable, " +
						"Upload-Metadata");
				response.setHeader("Access-Control-Max-Age", "86400");

			} else
			{
				response.setHeader("Access-Control-Expose-Headers", 
						"Upload-Offset, " +
						"Location, " +
						"Upload-Length, " +
						"Tus-Version, " +
						"Tus-Resumable, " +
						"Tus-Max-Size, " +
						"Tus-Extension, " +
						"Upload-Metadata");
			}
		}
	}



}