// Copyright 2016 The Domain Registry Authors. All Rights Reserved.
//
// 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 com.google.domain.registry.testing.mapreduce;

import static com.google.common.truth.Truth.assertThat;
import static com.google.domain.registry.model.ofy.ObjectifyService.ofy;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.when;

import com.google.appengine.api.blobstore.dev.LocalBlobstoreService;
import com.google.appengine.api.taskqueue.dev.LocalTaskQueue;
import com.google.appengine.api.taskqueue.dev.QueueStateInfo;
import com.google.appengine.api.taskqueue.dev.QueueStateInfo.HeaderWrapper;
import com.google.appengine.api.taskqueue.dev.QueueStateInfo.TaskStateInfo;
import com.google.appengine.tools.development.ApiProxyLocal;
import com.google.appengine.tools.development.testing.LocalTaskQueueTestConfig;
import com.google.appengine.tools.mapreduce.MapReduceServlet;
import com.google.appengine.tools.mapreduce.impl.shardedjob.ShardedJobHandler;
import com.google.appengine.tools.pipeline.impl.servlets.PipelineServlet;
import com.google.appengine.tools.pipeline.impl.servlets.TaskHandler;
import com.google.apphosting.api.ApiProxy;
import com.google.common.base.CharMatcher;
import com.google.domain.registry.testing.AppEngineRule;
import com.google.domain.registry.testing.FakeClock;
import com.google.domain.registry.util.FormattingLogger;

import org.junit.Before;
import org.junit.Rule;

import java.io.ByteArrayInputStream;
import java.io.ObjectInputStream;
import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.annotation.Nullable;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Base test class for mapreduces.  Adapted from EndToEndTestCase with some modifications that
 * allow it to work with the Domain Registry project, most notably inside knowledge of our
 * routing paths and our Datastore/Task Queue configurations.
 *
 * <p>See https://github.com/GoogleCloudPlatform/appengine-mapreduce/blob/master/java/src/test/java/com/google/appengine/tools/mapreduce/EndToEndTestCase.java
 *
 * @param <T> The type of the Action class that implements the mapreduce.
 */
public abstract class MapreduceTestCase<T> {

  private static final FormattingLogger logger = FormattingLogger.getLoggerForCallerClass();

  protected T action;

  private final MapReduceServlet mrServlet = new MapReduceServlet();
  private final PipelineServlet pipelineServlet = new PipelineServlet();
  private LocalTaskQueue taskQueue;

  @Rule
  public final AppEngineRule appEngine = AppEngineRule.builder()
      .withDatastore()
      .withLocalModules()
      .withTaskQueue()
      .build();

  @Before
  public void setUp() throws Exception {
    taskQueue = LocalTaskQueueTestConfig.getLocalTaskQueue();
    ApiProxyLocal proxy = (ApiProxyLocal) ApiProxy.getDelegate();
    // Creating files is not allowed in some test execution environments, so don't.
    proxy.setProperty(LocalBlobstoreService.NO_STORAGE_PROPERTY, "true");
  }

  protected List<QueueStateInfo.TaskStateInfo> getTasks(String queueName) {
    return taskQueue.getQueueStateInfo().get(queueName).getTaskInfo();
  }

  protected void executeTask(String queueName, QueueStateInfo.TaskStateInfo taskStateInfo)
      throws Exception {
    logger.finefmt("Executing task %s with URL %s",
        taskStateInfo.getTaskName(), taskStateInfo.getUrl());
    // Hack to allow for deferred tasks. Exploits knowing how they work.
    if (taskStateInfo.getUrl().endsWith("__deferred__")) {
      ObjectInputStream oin =
          new ObjectInputStream(new ByteArrayInputStream(taskStateInfo.getBodyAsBytes()));
      Runnable object = (Runnable) oin.readObject();
      object.run();
      return;
    }
    HttpServletRequest request = mock(HttpServletRequest.class);
    HttpServletResponse response = mock(HttpServletResponse.class);

    // Strip off routing paths that are handled in web.xml in non-test scenarios.
    String pathInfo = taskStateInfo.getUrl();
    if (pathInfo.startsWith("/_dr/mapreduce/")) {
      pathInfo = pathInfo.replace("/_dr/mapreduce", "");
    } else if (pathInfo.startsWith("/")) {
      pathInfo = pathInfo.replace("/_ah/", "");
      pathInfo = pathInfo.substring(pathInfo.indexOf('/'));
    } else {
      pathInfo = "/" + pathInfo;
    }
    when(request.getPathInfo()).thenReturn(pathInfo);
    when(request.getHeader("X-AppEngine-QueueName")).thenReturn(queueName);
    when(request.getHeader("X-AppEngine-TaskName")).thenReturn(taskStateInfo.getTaskName());
    // Pipeline looks at this header but uses the value only for diagnostic messages
    when(request.getIntHeader(TaskHandler.TASK_RETRY_COUNT_HEADER)).thenReturn(-1);
    for (HeaderWrapper header : taskStateInfo.getHeaders()) {
      int value = parseAsQuotedInt(header.getValue());
      when(request.getIntHeader(header.getKey())).thenReturn(value);
      logger.finefmt("header: %s=%s", header.getKey(), header.getValue());
      when(request.getHeader(header.getKey())).thenReturn(header.getValue());
    }

    Map<String, String> parameters = decodeParameters(taskStateInfo.getBody());
    for (String name : parameters.keySet()) {
      when(request.getParameter(name)).thenReturn(parameters.get(name));
    }
    when(request.getParameterNames()).thenReturn(Collections.enumeration(parameters.keySet()));

    if (taskStateInfo.getMethod().equals("POST")) {
      if (taskStateInfo.getUrl().startsWith(PipelineServlet.BASE_URL)) {
        pipelineServlet.doPost(request, response);
      } else {
        mrServlet.doPost(request, response);
      }
    } else {
      throw new UnsupportedOperationException();
    }
  }

  private int parseAsQuotedInt(String str) {
    try {
      return Integer.parseInt(CharMatcher.is('"').trimFrom(str));
    } catch (NumberFormatException e) {
      return -1;
    }
  }

  protected void executeTasksUntilEmpty() throws Exception {
    executeTasksUntilEmpty("default");
  }

  protected void executeTasksUntilEmpty(String queueName) throws Exception {
    executeTasksUntilEmpty(queueName, null);
  }

  /**
   * Executes mapreduce tasks, increment the clock between each task.
   *
   * <p>Incrementing the clock between tasks is important if tasks have transactions inside the
   * mapper or reducer, which don't have access to the fake clock.
   */
  protected void
      executeTasksUntilEmpty(String queueName, @Nullable FakeClock clock) throws Exception {
    while (true) {
      ofy().clearSessionCache();
      // We have to re-acquire task list every time, because local implementation returns a copy.
      List<QueueStateInfo.TaskStateInfo> taskInfo =
          taskQueue.getQueueStateInfo().get(queueName).getTaskInfo();
      if (taskInfo.isEmpty()) {
        break;
      }
      QueueStateInfo.TaskStateInfo taskStateInfo = taskInfo.get(0);
      taskQueue.deleteTask(queueName, taskStateInfo.getTaskName());
      executeTask(queueName, taskStateInfo);
      if (clock != null) {
        clock.advanceOneMilli();
      }
    }
  }

  protected TaskStateInfo grabNextTaskFromQueue(String queueName) {
    List<TaskStateInfo> taskInfo = getTasks(queueName);
    assertThat(taskInfo).isNotEmpty();
    TaskStateInfo taskStateInfo = taskInfo.get(0);
    taskQueue.deleteTask(queueName, taskStateInfo.getTaskName());
    return taskStateInfo;
  }

  // Sadly there's no way to parse query string with JDK. This is a good enough approximation.
  private static Map<String, String> decodeParameters(String requestBody)
      throws UnsupportedEncodingException {
    Map<String, String> result = new HashMap<>();

    String[] params = requestBody.split("&");
    for (String param : params) {
      String[] pair = param.split("=");
      String name = pair[0];
      String value = URLDecoder.decode(pair[1], "UTF-8");
      if (result.containsKey(name)) {
        throw new IllegalArgumentException("Duplicate parameter: " + requestBody);
      }
      result.put(name, value);
    }

    return result;
  }

  protected String getTaskId(TaskStateInfo taskStateInfo) throws UnsupportedEncodingException {
    return decodeParameters(taskStateInfo.getBody()).get(ShardedJobHandler.TASK_ID_PARAM);
  }
}