/*
    * 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.hadoop.chukwa.datatrigger;
  
  import org.apache.hadoop.fs.FileSystem;
  import org.apache.hadoop.fs.FileStatus;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.BufferedReader;
  import java.io.OutputStreamWriter;
  import java.net.URL;
  import java.net.HttpURLConnection;
  import java.net.MalformedURLException;
  import java.util.Map;
  import java.util.HashMap;
  
  /**
   * Trigger action that makes an HTTP request when executed.
   * <P>
   * To use this trigger, two types of configurations must be set. First, this class
   * must be configured to be invoked for a given trigger event. Second, the
   * the relevant settings for the HTTP request(s) to be made must be set as
   * described below.
   * <P>
   * The general format of this classes configs is
   * <code>chukwa.trigger.[eventName].http.[N].[paramName]</code> where
   * <code>eventName</code> is the name of the event the request values are bound
   * to (see TriggerEvent), <code>N</code> is a counter for each request configured (starting at 1)
   * and <code>paramName</code> is the request parameter being set.
   * <P>
   * Using the post demux success trigger event as an example, the first request
   * to be fired would use the following configurations
   * <ul>
   * <li><code>chukwa.trigger.post.demux.success.http.1.url</code> - The HTTP url to
   * invoke.</li>
   * <li><code>chukwa.trigger.post.demux.success.http.1.method</code> - The HTTP method
   * (optional, default=GET).</li>
   * <li><code>chukwa.trigger.post.demux.success.http.1.headers</code> - A comma-delimited
   * set of HTTP headers (in <code>[headerName]:[headerValue]</code> form) to
   * include (optional).</li>
   * <li><code>chukwa.trigger.post.demux.success.http.1.body</code> - The text HTTP body
   * to include (optional).</li>
   * <li><code>chukwa.trigger.post.demux.success.http.1.connect.timeout</code> - The
   * HTTP connection timeout setting in milliseconds (optional, default=5000ms).</li>
   * <li><code>chukwa.trigger.post.demux.success.http.1.read.timeout</code> - The
   * HTTP read timeout setting in milliseconds (optional, default=5000ms).</li>
   * </ul>
   * @see TriggerAction
   * @see TriggerEvent
   */
  public class HttpTriggerAction implements TriggerAction {
    protected Log log = LogFactory.getLog(getClass());
  
  
    /**
     * Iterates over each URL found, fetched other settings and fires and HTTP
     * request.
     *
     * @param conf
     * @param fs
     * @param src
     * @param triggerEvent
     * @throws IOException
     */
    public void execute(Configuration conf, FileSystem fs,
                        FileStatus[] src, TriggerEvent triggerEvent) throws IOException {
  
      if (log.isDebugEnabled()) {
        for (FileStatus file : src) {
            log.debug("Execute file: " + file.getPath());
        }
      }
  
      int reqNumber = 1;
      URL url = null;
      while ((url = getUrl(conf, triggerEvent, reqNumber)) != null) {
  
        // get settings for this request
        String method = getMethod(conf, triggerEvent, reqNumber);
        Map<String, String> headers = getHeaders(conf, triggerEvent, reqNumber);
       String body = getBody(conf, triggerEvent, reqNumber);
       int connectTimeout = getConnectTimeout(conf, triggerEvent, reqNumber);
       int readTimeout = getReadTimeout(conf, triggerEvent, reqNumber);
 
       try {
         // make the request
         makeHttpRequest(url, method, headers, body, connectTimeout, readTimeout);
       }
       catch(Exception e) {
         log.error("Error making request to " + url, e);
       }
       reqNumber++;
     }
   }
 
   private void makeHttpRequest(URL url, String method,
                                Map<String, String> headers, String body,
                                int connectTimeout, int readTimeout) throws IOException {
     if (url == null) {
       return;
     }
 
     // initialize the connection
     HttpURLConnection conn = (HttpURLConnection)url.openConnection();
     conn.setRequestMethod(method);
     conn.setDoInput(true);
     conn.setConnectTimeout(connectTimeout);
     conn.setReadTimeout(readTimeout);
 
     // set headers
     boolean contentLengthExists = false;
     if (headers != null) {
       for (String name: headers.keySet()) {
         if (log.isDebugEnabled()) {
           log.debug("Setting header " + name + ": " + headers.get(name));
         }
         if (name.equalsIgnoreCase("content-length")) {
           contentLengthExists = true;
         }
         conn.setRequestProperty(name, headers.get(name));
       }
     }
 
     // set content-length if not already set
     if (!"GET".equals(method) && !contentLengthExists) {
       String contentLength = body != null ? String.valueOf(body.length()) : "0";
       conn.setRequestProperty("Content-Length", contentLength);
     }
 
     // send body if it exists
     if (body != null) {
       conn.setDoOutput(true);
       OutputStreamWriter writer = new OutputStreamWriter(conn.getOutputStream());
       writer.write(body);
       writer.flush();
       writer.close();
     }
     else {
       conn.setDoOutput(false);
     }
 
     // read reponse code/message and dump response
     log.info("Making HTTP " + method + " to: " + url);
     int responseCode = conn.getResponseCode();
     log.info("HTTP Response code: " + responseCode);
 
 
     if (responseCode != 200) {
       log.info("HTTP Response message: " + conn.getResponseMessage());
     }
     else {
       BufferedReader reader = new BufferedReader(
                                 new InputStreamReader(conn.getInputStream()));
       String line;
       StringBuilder sb = new StringBuilder();
       while ((line = reader.readLine()) != null) {
         if(sb.length() > 0) {
           sb.append("\n");
         }
         sb.append(line);
       }
       log.info("HTTP Response:\n" + sb);
 
       reader.close();
     }
 
     conn.disconnect();
   }
 
   protected URL getUrl(Configuration conf,
                        TriggerEvent triggerEvent,
                        int reqNumber) throws MalformedURLException {
     String urlString = conf.get(getConfigKey(triggerEvent, reqNumber, "url"), null);
     if (urlString == null) {
       return null;
     }
 
     return new URL(urlString);
   }
 
   protected String getMethod(Configuration conf,
                              TriggerEvent triggerEvent,
                              int reqNumber) {
     return conf.get(getConfigKey(triggerEvent, reqNumber, "method"), "GET");
   }
 
   protected Map<String, String> getHeaders(Configuration conf,
                                            TriggerEvent triggerEvent,
                                            int reqNumber) {
     Map<String, String> headerMap = new HashMap<String,String>();
 
     String headers = conf.get(getConfigKey(triggerEvent, reqNumber, "headers"), null);
 
     if (headers != null) {
       String[] headersSplit = headers.split(",");
       for (String header : headersSplit) {
         String[] nvp = header.split(":", 2);
         if (nvp.length < 2) {
           log.error("Invalid HTTP header found: " + nvp);
           continue;
         }
         headerMap.put(nvp[0].trim(), nvp[1].trim());
       }
     }
 
     return headerMap;
   }
 
   protected String getBody(Configuration conf,
                            TriggerEvent triggerEvent,
                            int reqNumber) {
     return conf.get(getConfigKey(triggerEvent, reqNumber, "body"), "GET");
   }
 
   protected int getConnectTimeout(Configuration conf,
                                  TriggerEvent triggerEvent,
                                  int reqNumber) {
     String timeout = conf.get(getConfigKey(triggerEvent, reqNumber, "connect.timeout"), null);
     return timeout != null ? Integer.parseInt(timeout) : 5000;
   }
 
   
   protected int getReadTimeout(Configuration conf,
                               TriggerEvent triggerEvent,
                               int reqNumber) {
     String timeout = conf.get(getConfigKey(triggerEvent, reqNumber, "read.timeout"), null);
     return timeout != null ? Integer.parseInt(timeout) : 5000;
   }
 
   private String getConfigKey(TriggerEvent triggerEvent, int reqNumber, String name) {
     return triggerEvent.getConfigKeyBase() + ".http." + reqNumber + "." + name;
   }
 }