/*
 * Copyright 2012 LinkedIn Corp.
 *
 * Licensed 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 azkaban.execapp;

import com.google.common.base.Preconditions;

import java.io.IOException;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

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

import org.apache.log4j.Logger;

import org.codehaus.jackson.map.ObjectMapper;

import azkaban.constants.ServerInternals;
import azkaban.executor.ConnectorParams;
import azkaban.executor.ExecutableFlowBase;
import azkaban.executor.Executor;
import azkaban.executor.ExecutorLoader;
import azkaban.executor.ExecutorManagerException;
import azkaban.utils.FileIOUtils.JobMetaData;
import azkaban.utils.FileIOUtils.LogData;
import azkaban.utils.JSONUtils;

import static java.util.Objects.requireNonNull;


public class ExecutorServlet extends HttpServlet implements ConnectorParams {
  private static final long serialVersionUID = 1L;
  private static final Logger logger = Logger.getLogger(ExecutorServlet.class
      .getName());
  public static final String JSON_MIME_TYPE = "application/json";

  private AzkabanExecutorServer application;
  private FlowRunnerManager flowRunnerManager;

  public ExecutorServlet() {
    super();
  }

  @Override
  public void init(ServletConfig config) throws ServletException {
    application =
        (AzkabanExecutorServer) config.getServletContext().getAttribute(
            ServerInternals.AZKABAN_SERVLET_CONTEXT_KEY);

    if (application == null) {
      throw new IllegalStateException(
          "No batch application is defined in the servlet context!");
    }

    flowRunnerManager = application.getFlowRunnerManager();
  }

  protected void writeJSON(HttpServletResponse resp, Object obj)
      throws IOException {
    resp.setContentType(JSON_MIME_TYPE);
    ObjectMapper mapper = new ObjectMapper();
    OutputStream stream = resp.getOutputStream();
    mapper.writeValue(stream, obj);
  }

  @Override
  public void doGet(HttpServletRequest req, HttpServletResponse resp)
      throws ServletException, IOException {
    HashMap<String, Object> respMap = new HashMap<String, Object>();
    // logger.info("ExecutorServer called by " + req.getRemoteAddr());
    try {
      if (!hasParam(req, ACTION_PARAM)) {
        logger.error("Parameter action not set");
        respMap.put("error", "Parameter action not set");
      } else {
        String action = getParam(req, ACTION_PARAM);
        if (action.equals(UPDATE_ACTION)) {
          // logger.info("Updated called");
          handleAjaxUpdateRequest(req, respMap);
        } else if (action.equals(PING_ACTION)) {
          respMap.put("status", "alive");
        } else if (action.equals(RELOAD_JOBTYPE_PLUGINS_ACTION)) {
          logger.info("Reloading Jobtype plugins");
          handleReloadJobTypePlugins(respMap);
        } else if (action.equals(ACTIVATE)) {
          logger.warn("Setting ACTIVE flag to true");
          setActive(true, respMap);
        } else if (action.equals(GET_STATUS)) {
          logger.debug("Get Executor Status: ");
          getStatus(respMap);
        } else if (action.equals(DEACTIVATE)) {
          logger.warn("Setting ACTIVE flag to false");
          setActive(false, respMap);
        } else if (action.equals(SHUTDOWN)) {
          shutdown(respMap);
        } else {
          int execid = Integer.parseInt(getParam(req, EXECID_PARAM));
          String user = getParam(req, USER_PARAM, null);

          logger.info("User " + user + " has called action " + action + " on "
              + execid);
          if (action.equals(METADATA_ACTION)) {
            handleFetchMetaDataEvent(execid, req, resp, respMap);
          } else if (action.equals(LOG_ACTION)) {
            handleFetchLogEvent(execid, req, resp, respMap);
          } else if (action.equals(ATTACHMENTS_ACTION)) {
            handleFetchAttachmentsEvent(execid, req, resp, respMap);
          } else if (action.equals(EXECUTE_ACTION)) {
            handleAjaxExecute(req, respMap, execid);
          } else if (action.equals(STATUS_ACTION)) {
            handleAjaxFlowStatus(respMap, execid);
          } else if (action.equals(CANCEL_ACTION)) {
            logger.info("Cancel called.");
            handleAjaxCancel(respMap, execid, user);
          } else if (action.equals(PAUSE_ACTION)) {
            logger.info("Paused called.");
            handleAjaxPause(respMap, execid, user);
          } else if (action.equals(RESUME_ACTION)) {
            logger.info("Resume called.");
            handleAjaxResume(respMap, execid, user);
          } else if (action.equals(MODIFY_EXECUTION_ACTION)) {
            logger.info("Modify Execution Action");
            handleModifyExecutionRequest(respMap, execid, user, req);
          } else {
            logger.error("action: '" + action + "' not supported.");
            respMap.put("error", "action: '" + action + "' not supported.");
          }
        }
      }
    } catch (Exception e) {
      logger.error(e);
      respMap.put(RESPONSE_ERROR, e.getMessage());
    }
    writeJSON(resp, respMap);
    resp.flushBuffer();
  }

  private void handleModifyExecutionRequest(Map<String, Object> respMap,
      int execId, String user, HttpServletRequest req) throws ServletException {
    if (!hasParam(req, MODIFY_EXECUTION_ACTION_TYPE)) {
      respMap.put(RESPONSE_ERROR, "Modification type not set.");
    }
    String modificationType = getParam(req, MODIFY_EXECUTION_ACTION_TYPE);

    try {
      if (MODIFY_RETRY_FAILURES.equals(modificationType)) {
        flowRunnerManager.retryFailures(execId, user);
      }
    } catch (ExecutorManagerException e) {
      logger.error(e);
      respMap.put("error", e.getMessage());
    }
  }

  private void handleFetchLogEvent(int execId, HttpServletRequest req,
      HttpServletResponse resp, Map<String, Object> respMap)
      throws ServletException {
    String type = getParam(req, "type");
    int startByte = getIntParam(req, "offset");
    int length = getIntParam(req, "length");

    resp.setContentType("text/plain");
    resp.setCharacterEncoding("utf-8");

    if (type.equals("flow")) {
      LogData result;
      try {
        result = flowRunnerManager.readFlowLogs(execId, startByte, length);
        respMap.putAll(result.toObject());
      } catch (Exception e) {
        logger.error(e);
        respMap.put(RESPONSE_ERROR, e.getMessage());
      }
    } else {
      int attempt = getIntParam(req, "attempt", 0);
      String jobId = getParam(req, "jobId");
      try {
        LogData result =
            flowRunnerManager.readJobLogs(execId, jobId, attempt, startByte,
                length);
        respMap.putAll(result.toObject());
      } catch (Exception e) {
        logger.error(e);
        respMap.put("error", e.getMessage());
      }
    }
  }

  private void handleFetchAttachmentsEvent(int execId, HttpServletRequest req,
      HttpServletResponse resp, Map<String, Object> respMap)
      throws ServletException {

    String jobId = getParam(req, "jobId");
    int attempt = getIntParam(req, "attempt", 0);
    try {
      List<Object> result =
          flowRunnerManager.readJobAttachments(execId, jobId, attempt);
      respMap.put("attachments", result);
    } catch (Exception e) {
      logger.error(e);
      respMap.put("error", e.getMessage());
    }
  }

  private void handleFetchMetaDataEvent(int execId, HttpServletRequest req,
      HttpServletResponse resp, Map<String, Object> respMap)
      throws ServletException {
    int startByte = getIntParam(req, "offset");
    int length = getIntParam(req, "length");

    resp.setContentType("text/plain");
    resp.setCharacterEncoding("utf-8");

    int attempt = getIntParam(req, "attempt", 0);
    String jobId = getParam(req, "jobId");
    try {
      JobMetaData result =
          flowRunnerManager.readJobMetaData(execId, jobId, attempt, startByte,
              length);
      respMap.putAll(result.toObject());
    } catch (Exception e) {
      logger.error(e);
      respMap.put("error", e.getMessage());
    }
  }

  @SuppressWarnings("unchecked")
  private void handleAjaxUpdateRequest(HttpServletRequest req,
      Map<String, Object> respMap) throws ServletException, IOException {
    ArrayList<Object> updateTimesList =
        (ArrayList<Object>) JSONUtils.parseJSONFromString(getParam(req,
            UPDATE_TIME_LIST_PARAM));
    ArrayList<Object> execIDList =
        (ArrayList<Object>) JSONUtils.parseJSONFromString(getParam(req,
            EXEC_ID_LIST_PARAM));

    ArrayList<Object> updateList = new ArrayList<Object>();
    for (int i = 0; i < execIDList.size(); ++i) {
      long updateTime = JSONUtils.getLongFromObject(updateTimesList.get(i));
      int execId = (Integer) execIDList.get(i);

      ExecutableFlowBase flow = flowRunnerManager.getExecutableFlow(execId);
      if (flow == null) {
        Map<String, Object> errorResponse = new HashMap<String, Object>();
        errorResponse.put(RESPONSE_ERROR, "Flow does not exist");
        errorResponse.put(UPDATE_MAP_EXEC_ID, execId);
        updateList.add(errorResponse);
        continue;
      }

      if (flow.getUpdateTime() > updateTime) {
        updateList.add(flow.toUpdateObject(updateTime));
      }
    }

    respMap.put(RESPONSE_UPDATED_FLOWS, updateList);
  }

  private void handleAjaxExecute(HttpServletRequest req,
      Map<String, Object> respMap, int execId) throws ServletException {
    try {
      flowRunnerManager.submitFlow(execId);
    } catch (ExecutorManagerException e) {
      e.printStackTrace();
      logger.error(e);
      respMap.put(RESPONSE_ERROR, e.getMessage());
    }
  }

  private void handleAjaxFlowStatus(Map<String, Object> respMap, int execid) {
    ExecutableFlowBase flow = flowRunnerManager.getExecutableFlow(execid);
    if (flow == null) {
      respMap.put(STATUS_PARAM, RESPONSE_NOTFOUND);
    } else {
      respMap.put(STATUS_PARAM, flow.getStatus().toString());
      respMap.put(RESPONSE_UPDATETIME, flow.getUpdateTime());
    }
  }

  private void handleAjaxPause(Map<String, Object> respMap, int execid,
      String user) throws ServletException {
    if (user == null) {
      respMap.put(RESPONSE_ERROR, "user has not been set");
      return;
    }

    try {
      flowRunnerManager.pauseFlow(execid, user);
      respMap.put(STATUS_PARAM, RESPONSE_SUCCESS);
    } catch (ExecutorManagerException e) {
      logger.error(e);
      respMap.put(RESPONSE_ERROR, e.getMessage());
    }
  }

  private void handleAjaxResume(Map<String, Object> respMap, int execid,
      String user) throws ServletException {
    if (user == null) {
      respMap.put(RESPONSE_ERROR, "user has not been set");
      return;
    }

    try {
      flowRunnerManager.resumeFlow(execid, user);
      respMap.put(STATUS_PARAM, RESPONSE_SUCCESS);
    } catch (ExecutorManagerException e) {
      e.printStackTrace();
      respMap.put(RESPONSE_ERROR, e.getMessage());
    }
  }

  private void handleAjaxCancel(Map<String, Object> respMap, int execid,
      String user) throws ServletException {
    if (user == null) {
      respMap.put(RESPONSE_ERROR, "user has not been set");
      return;
    }

    try {
      flowRunnerManager.cancelFlow(execid, user);
      respMap.put(STATUS_PARAM, RESPONSE_SUCCESS);
    } catch (ExecutorManagerException e) {
      logger.error(e);
      respMap.put(RESPONSE_ERROR, e.getMessage());
    }
  }

  private void handleReloadJobTypePlugins(Map<String, Object> respMap)
      throws ServletException {
    try {
      flowRunnerManager.reloadJobTypePlugins();
      respMap.put(STATUS_PARAM, RESPONSE_SUCCESS);
    } catch (Exception e) {
      logger.error(e);
      respMap.put(RESPONSE_ERROR, e.getMessage());
    }
  }

  private void setActive(boolean value, Map<String, Object> respMap)
      throws ServletException {
    try {
      setActiveInternal(value);
      respMap.put(STATUS_PARAM, RESPONSE_SUCCESS);
    } catch (Exception e) {
      logger.error(e);
      respMap.put(RESPONSE_ERROR, e.getMessage());
    }
  }

  private void setActiveInternal(boolean value)
      throws ExecutorManagerException {
    ExecutorLoader executorLoader = application.getExecutorLoader();
    Executor executor = executorLoader.fetchExecutor(application.getHost(), application.getPort());
    Preconditions.checkState(executor != null, "Unable to obtain self entry in DB");
    if (executor.isActive() != value) {
      executor.setActive(value);
      executorLoader.updateExecutor(executor);
      flowRunnerManager.setActive(value);
    } else {
      logger.warn("Set active action ignored. Executor is already " + (value? "active" : "inactive"));
    }
  }

  /**
   * Prepare the executor for shutdown.
   *
   * @param respMap json response object
   * @throws ServletException
   */
  private void shutdown(Map<String, Object> respMap)
      throws ServletException {
    try {
      logger.warn("Shutting down executor...");

      // Set the executor to inactive. Will receive no new flows.
      setActiveInternal(false);
      application.shutdown();
      respMap.put(STATUS_PARAM, RESPONSE_SUCCESS);
    } catch (Exception e) {
      logger.error(e);
      respMap.put(RESPONSE_ERROR, e.getMessage());
    }
  }

  private void getStatus(Map<String, Object> respMap)
      throws ServletException {
    try {
      ExecutorLoader executorLoader = application.getExecutorLoader();
      final Executor executor = requireNonNull(executorLoader.fetchExecutor(application.getHost(), application.getPort()),
          "The executor can not be null");

      respMap.put("executor_id", Integer.toString(executor.getId()));
      respMap.put("isActive", String.valueOf(executor.isActive()));
      respMap.put(STATUS_PARAM, RESPONSE_SUCCESS);
    } catch (Exception e) {
      logger.error(e);
      respMap.put(RESPONSE_ERROR, e.getMessage());
    }
  }

  @Override
  public void doPost(HttpServletRequest req, HttpServletResponse resp)
      throws ServletException, IOException {

  }

  /**
   * Duplicated code with AbstractAzkabanServlet, but ne
   */
  public boolean hasParam(HttpServletRequest request, String param) {
    return request.getParameter(param) != null;
  }

  public String getParam(HttpServletRequest request, String name)
      throws ServletException {
    String p = request.getParameter(name);
    if (p == null)
      throw new ServletException("Missing required parameter '" + name + "'.");
    else
      return p;
  }

  public String getParam(HttpServletRequest request, String name,
      String defaultVal) {
    String p = request.getParameter(name);
    if (p == null) {
      return defaultVal;
    }

    return p;
  }

  public int getIntParam(HttpServletRequest request, String name)
      throws ServletException {
    String p = getParam(request, name);
    return Integer.parseInt(p);
  }

  public int getIntParam(HttpServletRequest request, String name, int defaultVal) {
    if (hasParam(request, name)) {
      try {
        return getIntParam(request, name);
      } catch (Exception e) {
        return defaultVal;
      }
    }

    return defaultVal;
  }
}
