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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.http.annotation.*;
import org.apache.juneau.rest.RestContext.*;
import org.apache.juneau.http.exception.*;
import org.apache.juneau.reflect.*;
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();
   }

   @Override /* RestCallHandler */
   public RestCall createCall(HttpServletRequest req, HttpServletResponse res) {
      return new RestCall(req, res).logger(context.getCallLogger()).loggerConfig(context.getCallLoggerConfig());
   }

   @Override /* RestCallHandler */
   public RestRequest createRequest(RestCall call) throws ServletException {
      return new RestRequest(context, call.getRequest());
   }

   @Override /* RestCallHandler */
   public RestResponse createResponse(RestCall call) throws ServletException {
      return new RestResponse(context, call.getRestRequest(), call.getResponse());
   }

   /**
    * 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 {

      RestCall call = createCall(r1, r2);

      try {
         context.checkForInitException();

         // If the resource path contains variables (e.g. @Rest(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 = call.getServletPath();
            String pi = call.getPathInfoUndecoded();
            UrlPathInfo upi2 = new UrlPathInfo(pi == null ? sp : sp + pi);
            UrlPathPatternMatch uppm = context.pathPattern.match(upi2);
            if (uppm != null && ! uppm.hasEmptyVars()) {
               RequestPath.addPathVars(call.getRequest(), uppm.getVars());
               call.request(
                  new OverrideableHttpServletRequest(call.getRequest())
                     .pathInfo(nullIfEmpty(urlDecode(uppm.getSuffix())))
                     .servletPath(uppm.getPrefix())
               );
            } else {
               call.debug(isDebug(call)).status(SC_NOT_FOUND).finish();
               return;
            }
         }

         // If this resource has child resources, try to recursively call them.
         String pi = call.getPathInfoUndecoded();
         if (context.hasChildResources() && pi != null && ! pi.equals("/")) {
            for (RestContext rc : context.getChildResources().values()) {
               UrlPathPattern upp = rc.pathPattern;
               UrlPathPatternMatch uppm = upp.match(call.getUrlPathInfo());
               if (uppm != null) {
                  if (! uppm.hasEmptyVars()) {
                     RequestPath.addPathVars(call.getRequest(), uppm.getVars());
                     HttpServletRequest childRequest = new OverrideableHttpServletRequest(call.getRequest())
                        .pathInfo(nullIfEmpty(urlDecode(uppm.getSuffix())))
                        .servletPath(call.getServletPath() + uppm.getPrefix());
                     rc.getCallHandler().service(childRequest, call.getResponse());
                  } else {
                     call.debug(isDebug(call)).status(SC_NOT_FOUND).finish();
                  }
                  return;
               }
            }
         }

         call.debug(isDebug(call));

         context.startCall(call);

         call.restRequest(createRequest(call));
         call.restResponse(createResponse(call));

         context.setRequest(call.getRestRequest());
         context.setResponse(call.getRestResponse());

         StreamResource r = null;
         if (call.getPathInfoUndecoded() != null) {
            String p = call.getPathInfoUndecoded().substring(1);
            if (context.isStaticFile(p)) {
               StaticFile sf = context.resolveStaticFile(p);
               r = sf.resource;
               call.responseMeta(sf.meta);
            } else if (p.equals("favicon.ico")) {
               call.output(null);
            }
         }

         if (r != null) {
            call.status(SC_OK);
            call.output(r);
         } else {

            // If the specified method has been defined in a subclass, invoke it.
            int rc = 0;
            String m = call.getMethod();

            if (restCallRouters.containsKey(m))
               rc = restCallRouters.get(m).invoke(call);

            if ((rc == 0 || rc == 404) && restCallRouters.containsKey("*"))
               rc = restCallRouters.get("*").invoke(call);

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

            if (call.getStatus() == 0)
               call.status(rc);
         }

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


      } catch (Throwable e) {
         handleError(call, convertThrowable(e));
      } finally {
         context.clearState();
      }

      call.finish();
      context.finishCall(call);
   }

   private boolean isDebug(RestCall call) {
      Enablement e = context.getDebug();
      if (e == TRUE)
         return true;
      if (e == FALSE)
         return false;
      return "true".equalsIgnoreCase(call.getRequest().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 call The HTTP call.
    * @throws IOException Thrown by underlying stream.
    * @throws HttpException Non-200 response.
    */
   @Override /* RestCallHandler */
   public void handleResponse(RestCall call) throws IOException, HttpException, NotImplemented {

      RestRequest req = call.getRestRequest();
      RestResponse res = call.getRestResponse();

      // 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.
    */
   @SuppressWarnings("deprecation")
   @Override
   public Throwable convertThrowable(Throwable t) {
      ClassInfo ci = ClassInfo.ofc(t);
      if (ci.is(HttpRuntimeException.class))
         t = ((HttpRuntimeException)t).getInner();
      if (ci.isChildOf(RestException.class) || ci.hasAnnotation(Response.class))
         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 call The HTTP call.
    */
   @Override /* RestCallHandler */
   public void handleNotFound(RestCall call) throws Exception {
      String pathInfo = call.getPathInfo();
      String methodUC = call.getMethod();
      int rc = call.getStatus();
      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{1}.", methodUC, onPath);
      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 call The rest call.
    * @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(RestCall call, Throwable e) throws IOException {

      call.exception(e);

      int occurrence = context == null ? 0 : context.getStackTraceOccurrence(e);

      int code = 500;

      ClassInfo ci = ClassInfo.ofc(e);
      Response r = ci.getAnnotation(Response.class);
      if (r != null)
         if (r.code().length > 0)
            code = r.code()[0];

      RestException e2 = (e instanceof RestException ? (RestException)e : new RestException(e, code)).setOccurrence(occurrence);

      HttpServletRequest req = call.getRequest();
      HttpServletResponse res = call.getResponse();

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