text: /*
   * Copyright (c) 2013, Institute for Pervasive Computing, ETH Zurich
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. Neither the name of the Institute nor the names of its contributors
   *    may be used to endorse or promote products derived from this software
   *    without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   *
   * This file is part of the Contiki operating system.
   */
  
  /**
   * \file
   *      CoAP module for observing resources (draft-ietf-core-observe-11).
   * \author
   *      Matthias Kovatsch <kovatsch@inf.ethz.ch>
   */
  
  /**
   * \addtogroup coap
   * @{
   */
  
  #include <stdio.h>
  #include <string.h>
  #include "coap-observe.h"
  #include "coap-engine.h"
  #include "lib/memb.h"
  #include "lib/list.h"
  
  /* Log configuration */
  #include "coap-log.h"
  #define LOG_MODULE "coap"
  #define LOG_LEVEL  LOG_LEVEL_COAP
  
  /*---------------------------------------------------------------------------*/
  MEMB(observers_memb, coap_observer_t, COAP_MAX_OBSERVERS);
  LIST(observers_list);
  /*---------------------------------------------------------------------------*/
  /*- Internal API ------------------------------------------------------------*/
  /*---------------------------------------------------------------------------*/
  static coap_observer_t *
  add_observer(const coap_endpoint_t *endpoint, const uint8_t *token,
               size_t token_len, const char *uri, int uri_len)
  {
    /* Remove existing observe relationship, if any. */
    coap_remove_observer_by_uri(endpoint, uri);
  
    coap_observer_t *o = memb_alloc(&observers_memb);
  
    if(o) {
      int max = sizeof(o->url) - 1;
      if(max > uri_len) {
        max = uri_len;
      }
      memcpy(o->url, uri, max);
      o->url[max] = 0;
      coap_endpoint_copy(&o->endpoint, endpoint);
      o->token_len = token_len;
      memcpy(o->token, token, token_len);
      o->last_mid = 0;
  
      LOG_INFO("Adding observer (%u/%u) for /%s [0x%02X%02X]\n",
               list_length(observers_list) + 1, COAP_MAX_OBSERVERS,
               o->url, o->token[0], o->token[1]);
      list_add(observers_list, o);
    }
  
    return o;
  }
  /*---------------------------------------------------------------------------*/
  /*- Removal -----------------------------------------------------------------*/
  /*---------------------------------------------------------------------------*/
  void
  coap_remove_observer(coap_observer_t *o)
  {
    LOG_INFO("Removing observer for /%s [0x%02X%02X]\n", o->url, o->token[0],
             o->token[1]);
  
    memb_free(&observers_memb, o);
    list_remove(observers_list, o);
  }
  /*---------------------------------------------------------------------------*/
  int
  coap_remove_observer_by_client(const coap_endpoint_t *endpoint)
  {
    int removed = 0;
    coap_observer_t *obs = NULL;
  
    LOG_DBG("Remove check client ");
    LOG_DBG_COAP_EP(endpoint);
    LOG_DBG_("\n");
    for(obs = (coap_observer_t *)list_head(observers_list); obs;
        obs = obs->next) {
      if(coap_endpoint_cmp(&obs->endpoint, endpoint)) {
        coap_remove_observer(obs);
        removed++;
      }
    }
    return removed;
  }
  /*---------------------------------------------------------------------------*/
  int
  coap_remove_observer_by_token(const coap_endpoint_t *endpoint,
                                uint8_t *token, size_t token_len)
  {
    int removed = 0;
    coap_observer_t *obs = NULL;
  
    for(obs = (coap_observer_t *)list_head(observers_list); obs;
        obs = obs->next) {
      LOG_DBG("Remove check Token 0x%02X%02X\n", token[0], token[1]);
      if(coap_endpoint_cmp(&obs->endpoint, endpoint)
         && obs->token_len == token_len
         && memcmp(obs->token, token, token_len) == 0) {
        coap_remove_observer(obs);
        removed++;
      }
    }
    return removed;
  }
  /*---------------------------------------------------------------------------*/
  int
  coap_remove_observer_by_uri(const coap_endpoint_t *endpoint,
                              const char *uri)
  {
    int removed = 0;
    coap_observer_t *obs = NULL;
  
    for(obs = (coap_observer_t *)list_head(observers_list); obs;
        obs = obs->next) {
      LOG_DBG("Remove check URL %p\n", uri);
      if((endpoint == NULL
          || (coap_endpoint_cmp(&obs->endpoint, endpoint)))
         && (obs->url == uri || memcmp(obs->url, uri, strlen(obs->url)) == 0)) {
        coap_remove_observer(obs);
        removed++;
      }
    }
    return removed;
  }
  /*---------------------------------------------------------------------------*/
  int
  coap_remove_observer_by_mid(const coap_endpoint_t *endpoint, uint16_t mid)
  {
    int removed = 0;
    coap_observer_t *obs = NULL;
  
    for(obs = (coap_observer_t *)list_head(observers_list); obs;
        obs = obs->next) {
      LOG_DBG("Remove check MID %u\n", mid);
      if(coap_endpoint_cmp(&obs->endpoint, endpoint)
         && obs->last_mid == mid) {
        coap_remove_observer(obs);
        removed++;
      }
    }
    return removed;
  }
  /*---------------------------------------------------------------------------*/
  /*- Notification ------------------------------------------------------------*/
  /*---------------------------------------------------------------------------*/
  void
  coap_notify_observers(coap_resource_t *resource)
  {
    coap_notify_observers_sub(resource, NULL);
  }
  /* Can be used either for sub - or when there is not resource - just
     a handler */
  void
  coap_notify_observers_sub(coap_resource_t *resource, const char *subpath)
  {
    /* build notification */
    coap_message_t notification[1]; /* this way the message can be treated as pointer as usual */
    coap_message_t request[1]; /* this way the message can be treated as pointer as usual */
    coap_observer_t *obs = NULL;
    int url_len, obs_url_len;
    char url[COAP_OBSERVER_URL_LEN];
    uint8_t sub_ok = 0;
  
    if(resource != NULL) {
      url_len = strlen(resource->url);
      strncpy(url, resource->url, COAP_OBSERVER_URL_LEN - 1);
      if(url_len < COAP_OBSERVER_URL_LEN - 1 && subpath != NULL) {
        strncpy(&url[url_len], subpath, COAP_OBSERVER_URL_LEN - url_len - 1);
      }
    } else if(subpath != NULL) {
      strncpy(url, subpath, COAP_OBSERVER_URL_LEN - 1);
    } else {
      /* No resource, no subpath */
      return;
    }
  
    /* Ensure url is null terminated because strncpy does not guarantee this */
    url[COAP_OBSERVER_URL_LEN - 1] = '\0';
    /* url now contains the notify URL that needs to match the observer */
    LOG_INFO("Notification from %s\n", url);
  
    coap_init_message(notification, COAP_TYPE_NON, CONTENT_2_05, 0);
    /* create a "fake" request for the URI */
    coap_init_message(request, COAP_TYPE_CON, COAP_GET, 0);
    coap_set_header_uri_path(request, url);
  
    /* iterate over observers */
    url_len = strlen(url);
    /* Assumes lazy evaluation... */
    sub_ok = (resource == NULL) || (resource->flags & HAS_SUB_RESOURCES);
    for(obs = (coap_observer_t *)list_head(observers_list); obs;
        obs = obs->next) {
      obs_url_len = strlen(obs->url);
  
      /* Do a match based on the parent/sub-resource match so that it is
         possible to do parent-node observe */
  
      /***** TODO fix here so that we handle the notofication correctly ******/
      /* All the new-style ... is assuming that the URL might be within */
      if((obs_url_len == url_len
          || (obs_url_len > url_len
              && sub_ok
              && obs->url[url_len] == '/'))
         && strncmp(url, obs->url, url_len) == 0) {
        coap_transaction_t *transaction = NULL;
  
        /*TODO implement special transaction for CON, sharing the same buffer to allow for more observers */
  
        if((transaction = coap_new_transaction(coap_get_mid(), &obs->endpoint))) {
          /* if COAP_OBSERVE_REFRESH_INTERVAL is zero, never send observations as confirmable messages */
          if(COAP_OBSERVE_REFRESH_INTERVAL != 0
              && (obs->obs_counter % COAP_OBSERVE_REFRESH_INTERVAL == 0)) {
            LOG_DBG("           Force Confirmable for\n");
            notification->type = COAP_TYPE_CON;
          }
  
          LOG_DBG("           Observer ");
          LOG_DBG_COAP_EP(&obs->endpoint);
          LOG_DBG_("\n");
  
          /* update last MID for RST matching */
          obs->last_mid = transaction->mid;
  
          /* prepare response */
          notification->mid = transaction->mid;
  
  	int32_t new_offset = 0;
  
          /* Either old style get_handler or the full handler */
          if(coap_call_handlers(request, notification, transaction->message +
                                COAP_MAX_HEADER_SIZE, COAP_MAX_CHUNK_SIZE,
                                &new_offset) > 0) {
            LOG_DBG("Notification on new handlers\n");
          } else {
            if(resource != NULL) {
              resource->get_handler(request, notification,
                                    transaction->message + COAP_MAX_HEADER_SIZE,
                                    COAP_MAX_CHUNK_SIZE, &new_offset);
            } else {
              /* What to do here? */
              notification->code = BAD_REQUEST_4_00;
            }
          }
  
          if(notification->code < BAD_REQUEST_4_00) {
            coap_set_header_observe(notification, (obs->obs_counter)++);
            /* mask out to keep the CoAP observe option length <= 3 bytes */
            obs->obs_counter &= 0xffffff;
          }
          coap_set_token(notification, obs->token, obs->token_len);
  
  	if(new_offset != 0) {
  	  coap_set_header_block2(notification,
  				 0,
  				 new_offset != -1,
  				 COAP_MAX_BLOCK_SIZE);
  	  coap_set_payload(notification,
  			   notification->payload,
  			   MIN(notification->payload_len,
  			       COAP_MAX_BLOCK_SIZE));
  	}
  
          transaction->message_len =
            coap_serialize_message(notification, transaction->message);
  
          coap_send_transaction(transaction);
        }
      }
    }
  }
  /*---------------------------------------------------------------------------*/
  void
  coap_observe_handler(coap_resource_t *resource, coap_message_t *coap_req,
                       coap_message_t *coap_res)
  {
    const coap_endpoint_t *src_ep;
    coap_observer_t *obs;
  
    LOG_DBG("CoAP observer handler rsc: %d\n", resource != NULL);
  
    if(coap_req->code == COAP_GET && coap_res->code < 128) { /* GET request and response without error code */
      if(coap_is_option(coap_req, COAP_OPTION_OBSERVE)) {
        src_ep = coap_get_src_endpoint(coap_req);
        if(src_ep == NULL) {
          /* No source endpoint, can not add */
        } else if(coap_req->observe == 0) {
          obs = add_observer(src_ep,
                             coap_req->token, coap_req->token_len,
                             coap_req->uri_path, coap_req->uri_path_len);
          if(obs) {
            coap_set_header_observe(coap_res, (obs->obs_counter)++);
            /* mask out to keep the CoAP observe option length <= 3 bytes */
            obs->obs_counter &= 0xffffff;
            /*
             * Following payload is for demonstration purposes only.
             * A subscription should return the same representation as a normal GET.
             * Uncomment if you want an information about the avaiable observers.
             */
  #if 0
            static char content[16];
            coap_set_payload(coap_res,
                             content,
                             snprintf(content, sizeof(content), "Added %u/%u",
                                      list_length(observers_list),
                                      COAP_MAX_OBSERVERS));
  #endif
          } else {
            coap_res->code = SERVICE_UNAVAILABLE_5_03;
            coap_set_payload(coap_res, "TooManyObservers", 16);
          }
        } else if(coap_req->observe == 1) {
  
          /* remove client if it is currently observe */
          coap_remove_observer_by_token(src_ep,
                                        coap_req->token, coap_req->token_len);
        }
      }
    }
  }
  /*---------------------------------------------------------------------------*/
  uint8_t
  coap_has_observers(char *path)
  {
    coap_observer_t *obs = NULL;
  
    for(obs = (coap_observer_t *)list_head(observers_list); obs;
        obs = obs->next) {
      if((strncmp(obs->url, path, strlen(path))) == 0) {
        return 1;
      }
    }
    return 0;
  }
  /*---------------------------------------------------------------------------*/
  /** @} */
  