res_calendar_caldav.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2008 - 2009, Digium, Inc.
 *
 * Terry Wilson <[email protected]>
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*! \file
 * \brief Resource for handling CalDAV calendars
 */

/*** MODULEINFO
   <depend>res_calendar</depend>
   <depend>neon</depend>
   <depend>ical</depend>
   <depend>libxml2</depend>
   <support_level>extended</support_level>
***/

#include "asterisk.h"

#include <libical/ical.h>
#include <ne_session.h>
#include <ne_uri.h>
#include <ne_request.h>
#include <ne_auth.h>
#include <ne_redirect.h>
#include <libxml/xmlmemory.h>
#include <libxml/parser.h>

#include "asterisk/module.h"
#include "asterisk/channel.h"
#include "asterisk/calendar.h"
#include "asterisk/lock.h"
#include "asterisk/config.h"
#include "asterisk/astobj2.h"

static void *caldav_load_calendar(void *data);
static void *unref_caldav(void *obj);
static int caldav_write_event(struct ast_calendar_event *event);

static struct ast_calendar_tech caldav_tech = {
   .type = "caldav",
   .description = "CalDAV calendars",
   .module = AST_MODULE,
   .load_calendar = caldav_load_calendar,
   .unref_calendar = unref_caldav,
   .write_event = caldav_write_event,
};

struct caldav_pvt {
   AST_DECLARE_STRING_FIELDS(
      AST_STRING_FIELD(url);
      AST_STRING_FIELD(user);
      AST_STRING_FIELD(secret);
   );
   struct ast_calendar *owner;
   ne_uri uri;
   ne_session *session;
   struct ao2_container *events;
};

static void caldav_destructor(void *obj)
{
   struct caldav_pvt *pvt = obj;

   ast_debug(1, "Destroying pvt for CalDAV calendar %s\n", pvt->owner->name);
   if (pvt->session) {
      ne_session_destroy(pvt->session);
   }
   ne_uri_free(&pvt->uri);
   ast_string_field_free_memory(pvt);

   ao2_callback(pvt->events, OBJ_UNLINK | OBJ_NODATA | OBJ_MULTIPLE, NULL, NULL);

   ao2_ref(pvt->events, -1);
}

static void *unref_caldav(void *obj)
{
   struct caldav_pvt *pvt = obj;

   ao2_ref(pvt, -1);
   return NULL;
}

static int fetch_response_reader(void *data, const char *block, size_t len)
{
   struct ast_str **response = data;
   unsigned char *tmp;

   if (!(tmp = ast_malloc(len + 1))) {
      return -1;
   }
   memcpy(tmp, block, len);
   tmp[len] = '\0';
   ast_str_append(response, 0, "%s", tmp);
   ast_free(tmp);

   return 0;
}

static int auth_credentials(void *userdata, const char *realm, int attempts, char *username, char *secret)
{
   struct caldav_pvt *pvt = userdata;

   if (attempts > 1) {
      ast_log(LOG_WARNING, "Invalid username or password for CalDAV calendar '%s'\n", pvt->owner->name);
      return -1;
   }

   ne_strnzcpy(username, pvt->user, NE_ABUFSIZ);
   ne_strnzcpy(secret, pvt->secret, NE_ABUFSIZ);

   return 0;
}

static int debug_response_handler(void *userdata, ne_request *req, const ne_status *st)
{
   if (st->code < 200 || st->code > 299) {
      ast_debug(1, "Unexpected response from server, %d: %s\n", st->code, st->reason_phrase);
      return 0;
   }
   return 1;
}

static struct ast_str *caldav_request(struct caldav_pvt *pvt, const char *method, struct ast_str *req_body, struct ast_str *subdir, const char *content_type)
{
   struct ast_str *response;
   ne_request *req;
   int ret;
   char buf[1000];

   if (!pvt) {
      ast_log(LOG_ERROR, "There is no private!\n");
      return NULL;
   }

   if (!(response = ast_str_create(512))) {
      ast_log(LOG_ERROR, "Could not allocate memory for response.\n");
      return NULL;
   }

   snprintf(buf, sizeof(buf), "%s%s", pvt->uri.path, subdir ? ast_str_buffer(subdir) : "");

   req = ne_request_create(pvt->session, method, buf);
   ne_add_response_body_reader(req, debug_response_handler, fetch_response_reader, &response);
   ne_set_request_body_buffer(req, ast_str_buffer(req_body), ast_str_strlen(req_body));
   ne_add_request_header(req, "Content-type", ast_strlen_zero(content_type) ? "text/xml" : content_type);
   ne_add_request_header(req, "Depth", "1");

   ret = ne_request_dispatch(req);
   ne_request_destroy(req);

   if (ret != NE_OK) {
      ast_log(LOG_WARNING, "Unknown response to CalDAV calendar %s, request %s to %s: %s\n", pvt->owner->name, method, buf, ne_get_error(pvt->session));
      ast_free(response);
      return NULL;
   }

   return response;
}

static int caldav_write_event(struct ast_calendar_event *event)
{
   struct caldav_pvt *pvt;
   struct ast_str *body = NULL, *response = NULL, *subdir = NULL;
   icalcomponent *calendar, *icalevent;
   icaltimezone *utc = icaltimezone_get_utc_timezone();
   int ret = -1;

   if (!event) {
      ast_log(LOG_WARNING, "No event passed!\n");
      return -1;
   }

   if (!(event->start && event->end)) {
      ast_log(LOG_WARNING, "The event must contain a start and an end\n");
      return -1;
   }
   if (!(body = ast_str_create(512)) ||
      !(subdir = ast_str_create(32))) {
      ast_log(LOG_ERROR, "Could not allocate memory for request!\n");
      goto write_cleanup;
   }

   pvt = event->owner->tech_pvt;

   if (ast_strlen_zero(event->uid)) {
      unsigned short val[8];
      int x;
      for (x = 0; x < 8; x++) {
         val[x] = ast_random();
      }
      ast_string_field_build(event, uid, "%04x%04x-%04x-%04x-%04x-%04x%04x%04x",
         (unsigned)val[0], (unsigned)val[1], (unsigned)val[2],
         (unsigned)val[3], (unsigned)val[4], (unsigned)val[5],
         (unsigned)val[6], (unsigned)val[7]);
   }

   calendar = icalcomponent_new(ICAL_VCALENDAR_COMPONENT);
   icalcomponent_add_property(calendar, icalproperty_new_version("2.0"));
   icalcomponent_add_property(calendar, icalproperty_new_prodid("-//Digium, Inc.//res_caldav//EN"));

   icalevent = icalcomponent_new(ICAL_VEVENT_COMPONENT);
   icalcomponent_add_property(icalevent, icalproperty_new_dtstamp(icaltime_current_time_with_zone(utc)));
   icalcomponent_add_property(icalevent, icalproperty_new_uid(event->uid));
   icalcomponent_add_property(icalevent, icalproperty_new_dtstart(icaltime_from_timet_with_zone(event->start, 0, utc)));
   icalcomponent_add_property(icalevent, icalproperty_new_dtend(icaltime_from_timet_with_zone(event->end, 0, utc)));
   if (!ast_strlen_zero(event->organizer)) {
      icalcomponent_add_property(icalevent, icalproperty_new_organizer(event->organizer));
   }
   if (!ast_strlen_zero(event->summary)) {
      icalcomponent_add_property(icalevent, icalproperty_new_summary(event->summary));
   }
   if (!ast_strlen_zero(event->description)) {
      icalcomponent_add_property(icalevent, icalproperty_new_description(event->description));
   }
   if (!ast_strlen_zero(event->location)) {
      icalcomponent_add_property(icalevent, icalproperty_new_location(event->location));
   }
   if (!ast_strlen_zero(event->categories)) {
      icalcomponent_add_property(icalevent, icalproperty_new_categories(event->categories));
   }
   if (event->priority > 0) {
      icalcomponent_add_property(icalevent, icalproperty_new_priority(event->priority));
   }

   switch (event->busy_state) {
   case AST_CALENDAR_BS_BUSY:
      icalcomponent_add_property(icalevent, icalproperty_new_status(ICAL_STATUS_CONFIRMED));
      break;

   case AST_CALENDAR_BS_BUSY_TENTATIVE:
      icalcomponent_add_property(icalevent, icalproperty_new_status(ICAL_STATUS_TENTATIVE));
      break;

   default:
      icalcomponent_add_property(icalevent, icalproperty_new_status(ICAL_STATUS_NONE));
   }

   icalcomponent_add_component(calendar, icalevent);

   ast_str_append(&body, 0, "%s", icalcomponent_as_ical_string(calendar));
   ast_str_set(&subdir, 0, "%s%s.ics", pvt->url[strlen(pvt->url) - 1] == '/' ? "" : "/", event->uid);

   if ((response = caldav_request(pvt, "PUT", body, subdir, "text/calendar"))) {
      ret = 0;
   }

write_cleanup:
   if (body) {
      ast_free(body);
   }
   if (response) {
      ast_free(response);
   }
   if (subdir) {
      ast_free(subdir);
   }

   return ret;
}

static struct ast_str *caldav_get_events_between(struct caldav_pvt *pvt, time_t start_time, time_t end_time)
{
   struct ast_str *body, *response;
   icaltimezone *utc = icaltimezone_get_utc_timezone();
   icaltimetype start, end;
   const char *start_str, *end_str;

   if (!(body = ast_str_create(512))) {
      ast_log(LOG_ERROR, "Could not allocate memory for body of request!\n");
      return NULL;
   }

   start = icaltime_from_timet_with_zone(start_time, 0, utc);
   end = icaltime_from_timet_with_zone(end_time, 0, utc);
   start_str = icaltime_as_ical_string(start);
   end_str = icaltime_as_ical_string(end);

   /* If I was really being efficient, I would store a collection of event URIs and etags,
    * first doing a query of just the etag and seeing if anything had changed.  If it had,
    * then I would do a request for each of the events that had changed, and only bother
    * updating those.  Oh well. */
   ast_str_append(&body, 0,
      "<?xml version=\"1.0\" encoding=\"utf-8\" ?>\n"
      "<C:calendar-query xmlns:D=\"DAV:\" xmlns:C=\"urn:ietf:params:xml:ns:caldav\">\n"
      "  <D:prop>\n"
      "    <C:calendar-data>\n"
      "      <C:expand start=\"%s\" end=\"%s\"/>\n"
      "    </C:calendar-data>\n"
      "  </D:prop>\n"
      "  <C:filter>\n"
      "    <C:comp-filter name=\"VCALENDAR\">\n"
      "      <C:comp-filter name=\"VEVENT\">\n"
      "        <C:time-range start=\"%s\" end=\"%s\"/>\n"
      "      </C:comp-filter>\n"
      "    </C:comp-filter>\n"
      "  </C:filter>\n"
      "</C:calendar-query>\n", start_str, end_str, start_str, end_str);

   response = caldav_request(pvt, "REPORT", body, NULL, NULL);
   ast_free(body);
   if (response && !ast_str_strlen(response)) {
      ast_free(response);
      return NULL;
   }

   return response;
}

static time_t icalfloat_to_timet(icaltimetype time)
{
   struct ast_tm tm = {0,};
   struct timeval tv;

   tm.tm_mday = time.day;
   tm.tm_mon = time.month - 1;
   tm.tm_year = time.year - 1900;
   tm.tm_hour = time.hour;
   tm.tm_min = time.minute;
   tm.tm_sec = time.second;
   tm.tm_isdst = -1;
   tv = ast_mktime(&tm, NULL);

   return tv.tv_sec;
}

/* span->start & span->end may be dates or floating times which have no timezone,
 * which would mean that they should apply to the local timezone for all recepients.
 * For example, if a meeting was set for 1PM-2PM floating time, people in different time
 * zones would not be scheduled at the same local times.  Dates are often treated as
 * floating times, so all day events will need to be converted--so we can trust the
 * span here, and instead will grab the start and end from the component, which will
 * allow us to test for floating times or dates.
 */
static void caldav_add_event(icalcomponent *comp, struct icaltime_span *span, void *data)
{
   struct caldav_pvt *pvt = data;
   struct ast_calendar_event *event;
   icaltimezone *utc = icaltimezone_get_utc_timezone();
   icaltimetype start, end, tmp;
   icalcomponent *valarm;
   icalproperty *prop;
   struct icaltriggertype trigger;

   if (!(pvt && pvt->owner)) {
      ast_log(LOG_ERROR, "Require a private structure with an owner\n");
      return;
   }

   if (!(event = ast_calendar_event_alloc(pvt->owner))) {
      ast_log(LOG_ERROR, "Could not allocate an event!\n");
      return;
   }

   start = icalcomponent_get_dtstart(comp);
   end = icalcomponent_get_dtend(comp);

   event->start = icaltime_get_tzid(start) ? span->start : icalfloat_to_timet(start);
   event->end = icaltime_get_tzid(end) ? span->end : icalfloat_to_timet(end);
   event->busy_state = span->is_busy ? AST_CALENDAR_BS_BUSY : AST_CALENDAR_BS_FREE;

   if ((prop = icalcomponent_get_first_property(comp, ICAL_SUMMARY_PROPERTY))) {
      ast_string_field_set(event, summary, icalproperty_get_value_as_string(prop));
   }

   if ((prop = icalcomponent_get_first_property(comp, ICAL_DESCRIPTION_PROPERTY))) {
      ast_string_field_set(event, description, icalproperty_get_value_as_string(prop));
   }

   if ((prop = icalcomponent_get_first_property(comp, ICAL_ORGANIZER_PROPERTY))) {
      ast_string_field_set(event, organizer, icalproperty_get_value_as_string(prop));
   }

   if ((prop = icalcomponent_get_first_property(comp, ICAL_LOCATION_PROPERTY))) {
      ast_string_field_set(event, location, icalproperty_get_value_as_string(prop));
   }

   if ((prop = icalcomponent_get_first_property(comp, ICAL_CATEGORIES_PROPERTY))) {
      ast_string_field_set(event, categories, icalproperty_get_value_as_string(prop));
   }

   if ((prop = icalcomponent_get_first_property(comp, ICAL_PRIORITY_PROPERTY))) {
      event->priority = icalvalue_get_integer(icalproperty_get_value(prop));
   }

   if ((prop = icalcomponent_get_first_property(comp, ICAL_UID_PROPERTY))) {
      ast_string_field_set(event, uid, icalproperty_get_value_as_string(prop));
   } else {
      ast_log(LOG_WARNING, "No UID found, but one is required. Generating, but updates may not be acurate\n");
      if (!ast_strlen_zero(event->summary)) {
         ast_string_field_set(event, uid, event->summary);
      } else {
         char tmp[100];
         snprintf(tmp, sizeof(tmp), "%ld", event->start);
         ast_string_field_set(event, uid, tmp);
      }
   }

   /* Get the attendees */
   for (prop = icalcomponent_get_first_property(comp, ICAL_ATTENDEE_PROPERTY);
         prop; prop = icalcomponent_get_next_property(comp, ICAL_ATTENDEE_PROPERTY)) {
      struct ast_calendar_attendee *attendee;
      const char *data;

      if (!(attendee = ast_calloc(1, sizeof(*attendee)))) {
         event = ast_calendar_unref_event(event);
         return;
      }
      data = icalproperty_get_attendee(prop);
      if (ast_strlen_zero(data)) {
         ast_free(attendee);
         continue;
      }
      attendee->data = ast_strdup(data);
      AST_LIST_INSERT_TAIL(&event->attendees, attendee, next);
   }


   /* Only set values for alarm based on VALARM.  Can be overriden in main/calendar.c by autoreminder
    * therefore, go ahead and add events even if their is no VALARM or it is malformed
    * Currently we are only getting the first VALARM and are handling repitition in main/calendar.c from calendar.conf */
   if (!(valarm = icalcomponent_get_first_component(comp, ICAL_VALARM_COMPONENT))) {
      ao2_link(pvt->events, event);
      event = ast_calendar_unref_event(event);
      return;
   }

   if (!(prop = icalcomponent_get_first_property(valarm, ICAL_TRIGGER_PROPERTY))) {
      ast_log(LOG_WARNING, "VALARM has no TRIGGER, skipping!\n");
      ao2_link(pvt->events, event);
      event = ast_calendar_unref_event(event);
      return;
   }

   trigger = icalproperty_get_trigger(prop);

   if (icaltriggertype_is_null_trigger(trigger)) {
      ast_log(LOG_WARNING, "Bad TRIGGER for VALARM, skipping!\n");
      ao2_link(pvt->events, event);
      event = ast_calendar_unref_event(event);
      return;
   }

   if (!icaltime_is_null_time(trigger.time)) { /* This is an absolute time */
      tmp = icaltime_convert_to_zone(trigger.time, utc);
      event->alarm = icaltime_as_timet_with_zone(tmp, utc);
   } else { /* Offset from either dtstart or dtend */
      /* XXX Technically you can check RELATED to see if the event fires from the END of the event
       * But, I'm not sure I've ever seen anyone implement it in calendaring software, so I'm ignoring for now */
      tmp = icaltime_add(start, trigger.duration);
      event->alarm = icaltime_as_timet_with_zone(tmp, icaltime_get_timezone(start));
   }

   ao2_link(pvt->events, event);
   event = ast_calendar_unref_event(event);

   return;
}

struct xmlstate {
   int in_caldata;
   struct caldav_pvt *pvt;
   struct ast_str *cdata;
   time_t start;
   time_t end;
};

static const xmlChar *caldav_node_localname = BAD_CAST "calendar-data";
static const xmlChar *caldav_node_nsuri     = BAD_CAST "urn:ietf:params:xml:ns:caldav";

static void handle_start_element(void *data,
                         const xmlChar *localname, const xmlChar *prefix, const xmlChar *uri,
                         int nb_namespaces, const xmlChar **namespaces,
                         int nb_attributes, int nb_defaulted, const xmlChar **attributes)
{
   struct xmlstate *state = data;

   if (xmlStrcmp(localname, caldav_node_localname) || xmlStrcmp(uri, caldav_node_nsuri)) {
      return;
   }

   state->in_caldata = 1;
   ast_str_reset(state->cdata);
}

static void handle_end_element(void *data,
                        const xmlChar *localname, const xmlChar *prefix, const xmlChar *uri)
{
   struct xmlstate *state = data;
   struct icaltimetype start, end;
   icaltimezone *utc = icaltimezone_get_utc_timezone();
   icalcomponent *iter;
   icalcomponent *comp;

   if (xmlStrcmp(localname, caldav_node_localname) || xmlStrcmp(uri, caldav_node_nsuri)) {
      return;
   }

   state->in_caldata = 0;
   if (!(state->cdata && ast_str_strlen(state->cdata))) {
      return;
   }
   /* XXX Parse the calendar blurb for recurrence events in the time range,
    * create an event, and add it to pvt->events */
   start = icaltime_from_timet_with_zone(state->start, 0, utc);
   end = icaltime_from_timet_with_zone(state->end, 0, utc);
   comp = icalparser_parse_string(ast_str_buffer(state->cdata));

   for (iter = icalcomponent_get_first_component(comp, ICAL_VEVENT_COMPONENT);
        iter;
        iter = icalcomponent_get_next_component(comp, ICAL_VEVENT_COMPONENT))
   {
      icalcomponent_foreach_recurrence(iter, start, end, caldav_add_event, state->pvt);
   }

   icalcomponent_free(comp);
}

static void handle_characters(void *data, const xmlChar *ch, int len)
{
   struct xmlstate *state = data;
   xmlChar *tmp;

   if (!state->in_caldata) {
      return;
   }

   tmp = xmlStrndup(ch, len);
   ast_str_append(&state->cdata, 0, "%s", (char *)tmp);
   xmlFree(tmp);
}

static int update_caldav(struct caldav_pvt *pvt)
{
   struct timeval now = ast_tvnow();
   time_t start, end;
   struct ast_str *response;
   xmlSAXHandler saxHandler;
   struct xmlstate state = {
      .in_caldata = 0,
      .pvt = pvt
   };

   start = now.tv_sec;
   end = now.tv_sec + 60 * pvt->owner->timeframe;
   if (!(response = caldav_get_events_between(pvt, start, end))) {
      return -1;
   }

   if (!(state.cdata = ast_str_create(512))) {
      ast_free(response);
      return -1;
   }

   state.start = start;
   state.end = end;

   /*
    * We want SAX2, so you assume that we want to call xmlSAXVersion() here, and
    * that certainly seems like the right thing to do, but the default SAX
    * handling functions assume that the 'data' pointer is going to be a
    * xmlParserCtxtPtr, not a user data pointer, so we have to make sure that we
    * are only calling the handlers that we control.
    *
    * So instead we hack things up a bit, clearing the struct and then assigning
    * the magic number manually.
    *
    * There may be a cleaner way to do this, but frankly the libxml2 docs are
    * pretty sparse.
    */
   memset(&saxHandler, 0, sizeof(saxHandler));
   saxHandler.initialized = XML_SAX2_MAGIC;
   saxHandler.startElementNs = handle_start_element;
   saxHandler.endElementNs = handle_end_element;
   saxHandler.characters = handle_characters;

   xmlSAXUserParseMemory(&saxHandler, &state, ast_str_buffer(response), ast_str_strlen(response));

   ast_calendar_merge_events(pvt->owner, pvt->events);

   ast_free(response);
   ast_free(state.cdata);

   return 0;
}

static int verify_cert(void *userdata, int failures, const ne_ssl_certificate *cert)
{
   /* Verify all certs */
   return 0;
}

static void *caldav_load_calendar(void *void_data)
{
   struct caldav_pvt *pvt;
   const struct ast_config *cfg;
   struct ast_variable *v;
   struct ast_calendar *cal = void_data;
   ast_mutex_t refreshlock;

   if (!(cal && (cfg = ast_calendar_config_acquire()))) {
      ast_log(LOG_ERROR, "You must enable calendar support for res_caldav to load\n");
      return NULL;
   }

   if (ao2_trylock(cal)) {
      if (cal->unloading) {
         ast_log(LOG_WARNING, "Unloading module, load_calendar cancelled.\n");
      } else {
         ast_log(LOG_WARNING, "Could not lock calendar, aborting!\n");
      }
      ast_calendar_config_release();
      return NULL;
   }

   if (!(pvt = ao2_alloc(sizeof(*pvt), caldav_destructor))) {
      ast_log(LOG_ERROR, "Could not allocate caldav_pvt structure for calendar: %s\n", cal->name);
      ast_calendar_config_release();
      return NULL;
   }

   pvt->owner = cal;

   if (!(pvt->events = ast_calendar_event_container_alloc())) {
      ast_log(LOG_ERROR, "Could not allocate space for fetching events for calendar: %s\n", cal->name);
      pvt = unref_caldav(pvt);
      ao2_unlock(cal);
      ast_calendar_config_release();
      return NULL;
   }

   if (ast_string_field_init(pvt, 32)) {
      ast_log(LOG_ERROR, "Couldn't allocate string field space for calendar: %s\n", cal->name);
      pvt = unref_caldav(pvt);
      ao2_unlock(cal);
      ast_calendar_config_release();
      return NULL;
   }

   for (v = ast_variable_browse(cfg, cal->name); v; v = v->next) {
      if (!strcasecmp(v->name, "url")) {
         ast_string_field_set(pvt, url, v->value);
      } else if (!strcasecmp(v->name, "user")) {
         ast_string_field_set(pvt, user, v->value);
      } else if (!strcasecmp(v->name, "secret")) {
         ast_string_field_set(pvt, secret, v->value);
      }
   }

   ast_calendar_config_release();

   if (ast_strlen_zero(pvt->url)) {
      ast_log(LOG_WARNING, "No URL was specified for CalDAV calendar '%s' - skipping.\n", cal->name);
      pvt = unref_caldav(pvt);
      ao2_unlock(cal);
      return NULL;
   }

   if (ne_uri_parse(pvt->url, &pvt->uri) || pvt->uri.host == NULL || pvt->uri.path == NULL) {
      ast_log(LOG_WARNING, "Could not parse url '%s' for CalDAV calendar '%s' - skipping.\n", pvt->url, cal->name);
      pvt = unref_caldav(pvt);
      ao2_unlock(cal);
      return NULL;
   }

   if (pvt->uri.scheme == NULL) {
      pvt->uri.scheme = "http";
   }

   if (pvt->uri.port == 0) {
      pvt->uri.port = ne_uri_defaultport(pvt->uri.scheme);
   }

   pvt->session = ne_session_create(pvt->uri.scheme, pvt->uri.host, pvt->uri.port);
   ne_redirect_register(pvt->session);
   ne_set_server_auth(pvt->session, auth_credentials, pvt);
   if (!strcasecmp(pvt->uri.scheme, "https")) {
      ne_ssl_trust_default_ca(pvt->session);
      ne_ssl_set_verify(pvt->session, verify_cert, NULL);
   }

   cal->tech_pvt = pvt;

   ast_mutex_init(&refreshlock);

   /* Load it the first time */
   update_caldav(pvt);

   ao2_unlock(cal);

   /* The only writing from another thread will be if unload is true */
   for (;;) {
      struct timeval tv = ast_tvnow();
      struct timespec ts = {0,};

      ts.tv_sec = tv.tv_sec + (60 * pvt->owner->refresh);

      ast_mutex_lock(&refreshlock);
      while (!pvt->owner->unloading) {
         if (ast_cond_timedwait(&pvt->owner->unload, &refreshlock, &ts) == ETIMEDOUT) {
            break;
         }
      }
      ast_mutex_unlock(&refreshlock);

      if (pvt->owner->unloading) {
         ast_debug(10, "Skipping refresh since we got a shutdown signal\n");
         return NULL;
      }

      ast_debug(10, "Refreshing after %d minute timeout\n", pvt->owner->refresh);

      update_caldav(pvt);
   }

   return NULL;
}

static int load_module(void)
{
   ne_sock_init();
   if (ast_calendar_register(&caldav_tech)) {
      ne_sock_exit();
      return AST_MODULE_LOAD_DECLINE;
   }

   return AST_MODULE_LOAD_SUCCESS;
}

static int unload_module(void)
{
   ast_calendar_unregister(&caldav_tech);
   ne_sock_exit();
   return 0;
}

AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "Asterisk CalDAV Calendar Integration",
   .support_level = AST_MODULE_SUPPORT_EXTENDED,
   .load = load_module,
   .unload = unload_module,
   .load_pri = AST_MODPRI_DEVSTATE_PLUGIN,
   .requires = "res_calendar",
);