/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.knox.gateway.service.test;

import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.utils.URIBuilder;
import org.apache.http.conn.ssl.SSLContexts;
import org.apache.http.conn.ssl.TrustSelfSignedStrategy;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.knox.gateway.config.GatewayConfig;
import org.apache.knox.gateway.services.GatewayServices;
import org.apache.knox.gateway.services.topology.TopologyService;
import org.apache.knox.gateway.topology.Service;
import org.apache.knox.gateway.topology.Topology;
import org.glassfish.jersey.internal.util.Base64;

import javax.net.ssl.SSLContext;
import javax.servlet.http.HttpServletRequest;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.QueryParam;
import javax.ws.rs.core.Context;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElementWrapper;
import javax.xml.bind.annotation.XmlRootElement;
import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import static javax.ws.rs.core.MediaType.APPLICATION_JSON;
import static javax.ws.rs.core.MediaType.APPLICATION_XML;

@Path( "/service-test" )
public class ServiceTestResource {
  @Context
  private HttpServletRequest request;


  @GET
  @Produces({APPLICATION_XML, APPLICATION_JSON})
  public ServiceTestWrapper serviceTest(@QueryParam("username") String username,
                                        @QueryParam("password") String password) {
    List<ServiceTest> tests = new ArrayList<>();
    List<String> messages = new ArrayList<>();
    String authString;
    GatewayConfig config = (GatewayConfig) request.getServletContext().getAttribute(GatewayConfig.GATEWAY_CONFIG_ATTRIBUTE);
    SSLContext ctx = null;
    CloseableHttpClient client;
    String id = getTopologyName();

    Topology topology = getTopology(id);

//    Create Authorization String
    if( username != null && password != null) {
      authString = "Basic " + Base64.encodeAsString((username + ":" + password).getBytes(StandardCharsets.UTF_8));
    } else if (request.getHeader("Authorization") != null) {
      authString = request.getHeader("Authorization");
    } else {
      authString = null;
    }

//    Attempt to build SSL context for HTTP client.
    try {
      ctx = SSLContexts.custom().loadTrustMaterial(null, new TrustSelfSignedStrategy()).build();
    } catch (Exception e) {
      messages.add(e.getMessage());
    }

//    Initialize the HTTP client
    if(ctx == null) {
      client = HttpClients.createDefault();
    } else {
      client = HttpClients.custom().setSslcontext(ctx).build();
    }

    if(topology != null) {
      for (Service s : topology.getServices()) {
        List<String> urls = getServiceTestURLs(config, s.getRole(), topology);

//          Make sure we handle a case where no URLs are found.
        if(urls.size() <= 0) {
          ServiceTest test = new ServiceTest(s);
          test.setMessage("This service did not contain any test URLs");
        }

        for (String url : urls) {
          HttpGet req = new HttpGet();
          ServiceTest test = new ServiceTest(s, url);

          if(authString != null) {
            req.setHeader("Authorization", authString);
          } else {
            messages.add("No credentials provided. Expect HTTP 401 responses.");
          }

          try {
            req.setURI(new URIBuilder(url).build());
            CloseableHttpResponse res = client.execute(req);
            String contentLength = "Content-Length:" + res.getEntity().getContentLength();
            String contentType = (res.getEntity().getContentType() != null) ? res.getEntity().getContentType().toString() : "No-contenttype";
            test.setResponseContent( contentLength + "," + contentType );
            test.setHttpCode(res.getStatusLine().getStatusCode());
            res.close();

          } catch (IOException e) {
            messages.add("Exception: " + e.getMessage());
            test.setMessage(e.getMessage());
          } catch (URISyntaxException e) {
            test.setMessage(e.getMessage());
          } catch (Exception e) {
            messages.add(e.getMessage());
            test.setMessage(e.getMessage());
          } finally {
            req.releaseConnection();
            tests.add(test);
          }
        }
      }
    } else {
      messages.add("Topology " + id + " not found");
    }

    try {
      client.close();
    } catch (IOException e) {
      e.printStackTrace();
    }

    ServiceTestWrapper stw = new ServiceTestWrapper();
    stw.setTests(tests);
    stw.setMessages(messages);

    return stw;
  }

  private String getTopologyName() {
    String ctxPath = request.getContextPath();
    GatewayConfig config = (GatewayConfig) request.getServletContext().getAttribute(GatewayConfig.GATEWAY_CONFIG_ATTRIBUTE);
    String path = config.getGatewayPath();

    String topologyName = ctxPath.replace(path, "").replace("/", "");
    return topologyName;
  }

  public Topology getTopology(@PathParam("id") String id) {
    GatewayServices services = (GatewayServices) request.getServletContext()
        .getAttribute(GatewayServices.GATEWAY_SERVICES_ATTRIBUTE);
    GatewayConfig config = (GatewayConfig) request.getServletContext().getAttribute(GatewayConfig.GATEWAY_CONFIG_ATTRIBUTE);

    TopologyService ts = services.getService(GatewayServices.TOPOLOGY_SERVICE);

    for (Topology t : ts.getTopologies()) {
      if(t.getName().equals(id)) {
        try {
          t.setUri(new URI( buildURI(t, config, request) ));
        } catch (URISyntaxException se) {
          t.setUri(null);
        }
        return t;
      }
    }
    return null;
  }

  private List<String> getServiceTestURLs(GatewayConfig conf, String role, Topology topology) {
    GatewayServices services = (GatewayServices) request.getServletContext()
        .getAttribute(GatewayServices.GATEWAY_SERVICES_ATTRIBUTE);
    List<String> fullURLs = new ArrayList<>();
    if(services != null) {
      TopologyService ts = services.getService(GatewayServices.TOPOLOGY_SERVICE);
      Map<String, List<String>> urls = ts.getServiceTestURLs(topology, conf);
      List<String> urlPaths = urls.get(role);

      if(urlPaths != null) {
        String base = buildURI(topology, conf, request);
        for (String u : urlPaths) {

          fullURLs.add(base + u);
        }
      }
    }
    return fullURLs;
  }

  private String buildXForwardBaseURL(HttpServletRequest req){
    final String X_Forwarded = "X-Forwarded-";
    final String X_Forwarded_Context = X_Forwarded + "Context";
    final String X_Forwarded_Proto = X_Forwarded + "Proto";
    final String X_Forwarded_Host = X_Forwarded + "Host";
    final String X_Forwarded_Port = X_Forwarded + "Port";
    final String X_Forwarded_Server = X_Forwarded + "Server";

    String baseURL = "";

//    Get Protocol
    if(req.getHeader(X_Forwarded_Proto) != null){
      baseURL += req.getHeader(X_Forwarded_Proto) + "://";
    } else {
      baseURL += req.getProtocol() + "://";
    }

//    Handle Server/Host and Port Here
    if (req.getHeader(X_Forwarded_Host) != null && req.getHeader(X_Forwarded_Port) != null){
//        Double check to see if host has port
      if(req.getHeader(X_Forwarded_Host).contains(req.getHeader(X_Forwarded_Port))){
        baseURL += req.getHeader(X_Forwarded_Host);
      } else {
//        If there's no port, add the host and port together;
        baseURL += req.getHeader(X_Forwarded_Host) + ":" + req.getHeader(X_Forwarded_Port);
      }
    } else if(req.getHeader(X_Forwarded_Server) != null && req.getHeader(X_Forwarded_Port) != null){
//      Tack on the server and port if they're available. Try host if server not available
      baseURL += req.getHeader(X_Forwarded_Server) + ":" + req.getHeader(X_Forwarded_Port);
    } else if(req.getHeader(X_Forwarded_Port) != null) {
//      if we at least have a port, we can use it.
      baseURL += req.getServerName() + ":" + req.getHeader(X_Forwarded_Port);
    } else {
//      Resort to request members
      baseURL += req.getServerName() + ":" + req.getLocalPort();
    }

//    Handle Server context
    if( req.getHeader(X_Forwarded_Context) != null ) {
      baseURL += req.getHeader( X_Forwarded_Context );
    } else {
      baseURL += req.getContextPath();
    }

    return baseURL;
  }

  String buildURI(Topology topology, GatewayConfig config, HttpServletRequest req){
    String uri = buildXForwardBaseURL(req);

//    Strip extra context
    uri = uri.replace(req.getContextPath(), "");

//    Add the gateway path
    String gatewayPath;
    if(config.getGatewayPath() != null){
      gatewayPath = config.getGatewayPath();
    }else{
      gatewayPath = "gateway";
    }
    uri += "/" + gatewayPath;

    uri += "/" + topology.getName();
    return uri;
  }

  @XmlAccessorType(XmlAccessType.NONE)
  public static class ServiceTest {

    @XmlElement
    private String serviceName;
    @XmlElement
    private String requestURL;
    @XmlElement
    private String responseContent;
    @XmlElement
    private int httpCode = -1;

    @XmlElement
    String message;

    public ServiceTest() { }

    public ServiceTest(Service s) {
      this.serviceName = s.getRole();
    }

    public ServiceTest( Service s, String requestURL) {
      this.serviceName = s.getRole();
      this.requestURL = requestURL;
    }

    public String getServiceName() {
      return serviceName;
    }

    public void setServiceName(String n) {
      serviceName = n;
    }

    public String getRequestURL() {
      return requestURL;
    }

    public void setRequestURL(String requestURL) {
      this.requestURL = requestURL;
    }

    public String getResponseContent() {
      return responseContent;
    }

    public void setResponseContent(String responseContent) {
      this.responseContent = responseContent;
    }

    public int getHttpCode() {
      return httpCode;
    }

    public void setHttpCode(int httpCode) {
      this.httpCode = httpCode;
      setMessage();
    }

    public void setMessage() {
      message = buildMessage(httpCode);
    }

    public void setMessage(String msg) {

      if(httpCode != -1) {
        message = buildMessage(httpCode);
      } else {
        message = msg;
      }
    }

    public String getMessage(){
      return message;
    }

    static String buildMessage(int code) {

      String message = "";

      switch (code) {

        case 200:
          message += "Request sucessful.";
          break;
        case 400:
          message += "Could not properly intepret HTTP request.";
          break;
        case 401:
          message += "User was not authorized. Try using credentials with access to all services. " +
              "Ensure LDAP server is running.";
          break;
        case 403:
          message += "Access to this resource is forbidden. It seems we might have made a bad request.";
          break;
        case 404:
          message += "The page could not be found. Are the URLs for the topology services correct?";
          break;
        case 500:
          message += "The server encountered an error. Are all of the cluster's services running? \n" +
              "Can a connection be established without Knox?";
          break;

      }
      return message;

    }


  }

  @XmlAccessorType(XmlAccessType.FIELD)
  @XmlRootElement
  public static class ServiceTestWrapper{

    @XmlElement(name="ServiceTest")
    @XmlElementWrapper(name="Tests")
    private List<ServiceTest> tests = new ArrayList<>();

    @XmlElement(name="message")
    @XmlElementWrapper(name="messages")
    private List<String> messages = new ArrayList<>();

    public List<ServiceTest> getTests(){
      return tests;
    }

    public void setTests(List<ServiceTest> st){
      this.tests = st;
    }

    public List<String> getMessages() {
      return messages;
    }

    public void setMessages(List<String> messages){
      this.messages = messages;
    }

  }


}