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// *  http://www.apache.org/licenses/LICENSE-2.0                                                                             *
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package org.apache.juneau.rest;

import static javax.servlet.http.HttpServletResponse.*;
import static org.apache.juneau.internal.IOUtils.*;
import static org.apache.juneau.internal.StringUtils.*;
import static org.apache.juneau.rest.Enablement.*;

import java.io.*;
import java.util.*;

import javax.servlet.*;
import javax.servlet.http.*;

import org.apache.juneau.http.StreamResource;
import org.apache.juneau.rest.RestContext.*;
import org.apache.juneau.rest.exception.*;
import org.apache.juneau.rest.util.*;

/**
 * Default implementation of {@link RestCallHandler}.
 *
 * <p>
 * Subclasses can override these methods to tailor how HTTP REST calls are handled.
 * <br>Subclasses MUST implement a public constructor that takes in a {@link RestContext} object.
 *
 * <ul class='seealso'>
 *    <li class='jf'>{@link RestContext#REST_callHandler}
 * </ul>
 */
public class BasicRestCallHandler implements RestCallHandler {

   private final RestContext context;
   private final Map<String,RestCallRouter> restCallRouters;

   /**
    * Constructor.
    *
    * @param context The resource context.
    */
   public BasicRestCallHandler(RestContext context) {
      this.context = context;
      this.restCallRouters = context.getCallRouters();
   }

   /**
    * Creates a {@link RestRequest} object based on the specified incoming {@link HttpServletRequest} object.
    *
    * <p>
    * Subclasses may choose to override this method to provide a specialized request object.
    *
    * @param req The request object from the {@link #service(HttpServletRequest, HttpServletResponse)} method.
    * @return The wrapped request object.
    * @throws ServletException If any errors occur trying to interpret the request.
    */
   @Override /* RestCallHandler */
   public RestRequest createRequest(HttpServletRequest req) throws ServletException {
      return new RestRequest(context, req);
   }

   /**
    * Creates a {@link RestResponse} object based on the specified incoming {@link HttpServletResponse} object
    * and the request returned by {@link #createRequest(HttpServletRequest)}.
    *
    * <p>
    * Subclasses may choose to override this method to provide a specialized response object.
    *
    * @param req The request object returned by {@link #createRequest(HttpServletRequest)}.
    * @param res The response object from the {@link #service(HttpServletRequest, HttpServletResponse)} method.
    * @return The wrapped response object.
    * @throws ServletException If any errors occur trying to interpret the request or response.
    */
   @Override /* RestCallHandler */
   public RestResponse createResponse(RestRequest req, HttpServletResponse res) throws ServletException {
      return new RestResponse(context, req, res);
   }

   /**
    * The main service method.
    *
    * <p>
    * Subclasses can optionally override this method if they want to tailor the behavior of requests.
    *
    * @param r1 The incoming HTTP servlet request object.
    * @param r2 The incoming HTTP servlet response object.
    * @throws ServletException General servlet exception.
    * @throws IOException Thrown by underlying stream.
    */
   @Override /* RestCallHandler */
   public void service(HttpServletRequest r1, HttpServletResponse r2) throws ServletException, IOException {

      long startTime = System.currentTimeMillis();
      RestRequest req = null;
      RestResponse res = null;
      RestCallLogger logger = context.getCallLogger();
      RestCallLoggerConfig loggerConfig = context.getCallLoggerConfig();

      try {
         context.checkForInitException();

         String pathInfo = RestUtils.getPathInfoUndecoded(r1);  // Can't use r1.getPathInfo() because we don't want '%2F' resolved.
         UrlPathInfo upi = new UrlPathInfo(pathInfo);

         // If the resource path contains variables (e.g. @RestResource(path="/f/{a}/{b}"), then we want to resolve
         // those variables and push the servletPath to include the resolved variables.  The new pathInfo will be
         // the remainder after the new servletPath.
         // Only do this for the top-level resource because the logic for child resources are processed next.
         if (context.pathPattern.hasVars() && context.getParentContext() == null) {
            String sp = r1.getServletPath();
            UrlPathInfo upi2 = new UrlPathInfo(pathInfo == null ? sp : sp + pathInfo);
            UrlPathPatternMatch uppm = context.pathPattern.match(upi2);
            if (uppm != null && ! uppm.hasEmptyVars()) {
               RequestPath.addPathVars(r1, uppm.getVars());
               r1 = new OverrideableHttpServletRequest(r1)
                  .pathInfo(nullIfEmpty(urlDecode(uppm.getSuffix())))
                  .servletPath(uppm.getPrefix());
               pathInfo = RestUtils.getPathInfoUndecoded(r1);  // Can't use r1.getPathInfo() because we don't want '%2F' resolved.
               upi = new UrlPathInfo(pathInfo);
            } else {
               if (isDebug(r1)) {
                  r1 = CachingHttpServletRequest.wrap(r1);
                  r1.setAttribute("Debug", true);
               }
               r2.setStatus(SC_NOT_FOUND);
               return;
            }
         }

         // If this resource has child resources, try to recursively call them.
         if (context.hasChildResources() && pathInfo != null && ! pathInfo.equals("/")) {
            for (RestContext rc : context.getChildResources().values()) {
               UrlPathPattern upp = rc.pathPattern;
               UrlPathPatternMatch uppm = upp.match(upi);
               if (uppm != null) {
                  if (! uppm.hasEmptyVars()) {
                     RequestPath.addPathVars(r1, uppm.getVars());
                     HttpServletRequest childRequest = new OverrideableHttpServletRequest(r1)
                        .pathInfo(nullIfEmpty(urlDecode(uppm.getSuffix())))
                        .servletPath(r1.getServletPath() + uppm.getPrefix());
                     rc.getCallHandler().service(childRequest, r2);
                  } else {
                     if (isDebug(r1)) {
                        r1 = CachingHttpServletRequest.wrap(r1);
                        r1.setAttribute("Debug", true);
                     }
                     r2.setStatus(SC_NOT_FOUND);
                  }
                  return;
               }
            }
         }

         if (isDebug(r1)) {
            r1 = CachingHttpServletRequest.wrap(r1);
            r2 = CachingHttpServletResponse.wrap(r2);
            r1.setAttribute("Debug", true);
         }

         context.startCall(r1, r2);

         req = createRequest(r1);
         res = createResponse(req, r2);
         req.setResponse(res);
         context.setRequest(req);
         context.setResponse(res);
         String method = req.getMethod();
         String methodUC = method.toUpperCase(Locale.ENGLISH);

         StreamResource r = null;
         if (pathInfo != null) {
            String p = pathInfo.substring(1);
            if (context.isStaticFile(p)) {
               StaticFile sf = context.resolveStaticFile(p);
               r = sf.resource;
               res.setResponseMeta(sf.meta);
            } else if (p.equals("favicon.ico")) {
               res.setOutput(null);
            }
         }

         if (r != null) {
            res.setStatus(SC_OK);
            res.setOutput(r);
         } else {

            // If the specified method has been defined in a subclass, invoke it.
            int rc = 0;
            if (restCallRouters.containsKey(methodUC)) {
               rc = restCallRouters.get(methodUC).invoke(upi, req, res);
            } else if (restCallRouters.containsKey("*")) {
               rc = restCallRouters.get("*").invoke(upi, req, res);
            }

            // Should be 405 if the URL pattern matched but HTTP method did not.
            if (rc == 0)
               for (RestCallRouter rcc : restCallRouters.values())
                  if (rcc.matches(upi))
                     rc = SC_METHOD_NOT_ALLOWED;

            // Should be 404 if URL pattern didn't match.
            if (rc == 0)
               rc = SC_NOT_FOUND;

            // If not invoked above, see if it's an OPTIONs request
            if (rc != SC_OK)
               handleNotFound(rc, req, res);

            if (res.getStatus() == 0)
               res.setStatus(rc);
         }

         if (res.hasOutput()) {
            // Now serialize the output if there was any.
            // Some subclasses may write to the OutputStream or Writer directly.
            handleResponse(req, res);
         }

         // Make sure our writer in RestResponse gets written.
         res.flushBuffer();
         req.close();

         r1 = req.getInner();
         r2 = res.getInner();
         loggerConfig = req.getCallLoggerConfig();

         r1.setAttribute("ExecTime", System.currentTimeMillis() - startTime);

      } catch (Throwable e) {
         e = convertThrowable(e);
         if (req != null) {
            r1 = req.getInner();
            loggerConfig = req.getCallLoggerConfig();
         }
         if (res != null)
            r2 = res.getInner();
         r1.setAttribute("Exception", e);
         r1.setAttribute("ExecTime", System.currentTimeMillis() - startTime);
         handleError(r1, r2, e);
      } finally {
         context.clearState();
      }

      logger.log(loggerConfig, r1, r2);
      context.finishCall(r1, r2);
   }

   private boolean isDebug(HttpServletRequest req) {
      Enablement e = context.getDebug();
      if (e == TRUE)
         return true;
      if (e == FALSE)
         return false;
      return "true".equalsIgnoreCase(req.getHeader("X-Debug"));
   }

   /**
    * The main method for serializing POJOs passed in through the {@link RestResponse#setOutput(Object)} method or
    * returned by the Java method.
    *
    * <p>
    * Subclasses may override this method if they wish to modify the way the output is rendered or support other output
    * formats.
    *
    * <p>
    * The default implementation simply iterates through the response handlers on this resource
    * looking for the first one whose {@link ResponseHandler#handle(RestRequest, RestResponse)} method returns
    * <jk>true</jk>.
    *
    * @param req The HTTP request.
    * @param res The HTTP response.
    * @throws IOException Thrown by underlying stream.
    * @throws RestException Non-200 response.
    */
   @Override /* RestCallHandler */
   public void handleResponse(RestRequest req, RestResponse res) throws IOException, RestException, NotImplemented {
      // Loop until we find the correct handler for the POJO.
      for (ResponseHandler h : context.getResponseHandlers())
         if (h.handle(req, res))
            return;
      Object output = res.getOutput();
      throw new NotImplemented("No response handlers found to process output of type '"+(output == null ? null : output.getClass().getName())+"'");
   }

   /**
    * Method that can be subclassed to allow uncaught throwables to be treated as other types of throwables.
    *
    * <p>
    * The default implementation looks at the throwable class name to determine whether it can be converted to another type:
    *
    * <ul>
    *    <li><js>"*AccessDenied*"</js> - Converted to {@link Unauthorized}.
    *    <li><js>"*Empty*"</js>,<js>"*NotFound*"</js> - Converted to {@link NotFound}.
    * </ul>
    *
    * @param t The thrown object.
    * @return The converted thrown object.
    */
   @Override
   public Throwable convertThrowable(Throwable t) {
      if (t instanceof RestException)
         return t;
      String n = t.getClass().getName();
      if (n.contains("AccessDenied"))
         return new Unauthorized(t);
      if (n.contains("Empty") || n.contains("NotFound"))
         return new NotFound(t);
      return t;
   }

   /**
    * Handle the case where a matching method was not found.
    *
    * <p>
    * Subclasses can override this method to provide a 2nd-chance for specifying a response.
    * The default implementation will simply throw an exception with an appropriate message.
    *
    * @param rc The HTTP response code.
    * @param req The HTTP request.
    * @param res The HTTP response.
    */
   @Override /* RestCallHandler */
   public void handleNotFound(int rc, RestRequest req, RestResponse res) throws Exception {
      String pathInfo = req.getPathInfo();
      String methodUC = req.getMethod();
      String onPath = pathInfo == null ? " on no pathInfo"  : String.format(" on path '%s'", pathInfo);
      if (rc == SC_NOT_FOUND)
         throw new NotFound("Method ''{0}'' not found on resource with matching pattern{1}.", methodUC, onPath);
      else if (rc == SC_PRECONDITION_FAILED)
         throw new PreconditionFailed("Method ''{0}'' not found on resource{1} with matching matcher.", methodUC, onPath);
      else if (rc == SC_METHOD_NOT_ALLOWED)
         throw new MethodNotAllowed("Method ''{0}'' not found on resource.", methodUC);
      else
         throw new ServletException("Invalid method response: " + rc);
   }

   /**
    * Method for handling response errors.
    *
    * <p>
    * Subclasses can override this method to provide their own custom error response handling.
    *
    * @param req The servlet request.
    * @param res The servlet response.
    * @param e The exception that occurred.
    * @throws IOException Can be thrown if a problem occurred trying to write to the output stream.
    */
   @Override /* RestCallHandler */
   @SuppressWarnings("deprecation")
   public synchronized void handleError(HttpServletRequest req, HttpServletResponse res, Throwable e) throws IOException {

      int occurrence = context == null ? 0 : context.getStackTraceOccurrence(e);
      RestException e2 = (e instanceof RestException ? (RestException)e : new RestException(e, 500)).setOccurrence(occurrence);

      Throwable t = e2.getRootCause();
      if (t != null) {
         res.setHeader("Exception-Name", t.getClass().getName());
         res.setHeader("Exception-Message", t.getMessage());
      }

      try {
         res.setContentType("text/plain");
         res.setHeader("Content-Encoding", "identity");
         res.setStatus(e2.getStatus());

         PrintWriter w = null;
         try {
            w = res.getWriter();
         } catch (IllegalStateException x) {
            w = new PrintWriter(new OutputStreamWriter(res.getOutputStream(), UTF8));
         }

         try (PrintWriter w2 = w) {
            String httpMessage = RestUtils.getHttpResponseText(e2.getStatus());
            if (httpMessage != null)
               w2.append("HTTP ").append(String.valueOf(e2.getStatus())).append(": ").append(httpMessage).append("\n\n");
            if (context != null && context.isRenderResponseStackTraces())
               e.printStackTrace(w2);
            else
               w2.append(e2.getFullStackMessage(true));
         }

      } catch (Exception e1) {
         req.setAttribute("Exception", e1);
      }
   }

   /**
    * Returns the session objects for the specified request.
    *
    * <p>
    * The default implementation simply returns a single map containing <c>{'req':req}</c>.
    *
    * @param req The REST request.
    * @return The session objects for that request.
    */
   @Override /* RestCallHandler */
   public Map<String,Object> getSessionObjects(RestRequest req, RestResponse res) {
      Map<String,Object> m = new HashMap<>();
      m.put("req", req);
      m.put("res", res);
      return m;
   }
}