res_calendar_ews.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2008 - 2009, Digium, Inc.
 *
 * Jan Kalab <pitlicek@gmail.com>
 *
 * 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 MS Exchange Web Service calendars
 */
 
/*** MODULEINFO
    <depend>res_calendar</depend>
    <depend>neon29</depend>
    <support_level>extended</support_level>
***/
 
#include "asterisk.h"
 
#include <ne_request.h>
#include <ne_session.h>
#include <ne_uri.h>
#include <ne_socket.h>
#include <ne_auth.h>
#include <ne_xml.h>
#include <ne_xmlreq.h>
#include <ne_utils.h>
#include <ne_redirect.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 *ewscal_load_calendar(void *data);
static void *unref_ewscal(void *obj);
static int ewscal_write_event(struct ast_calendar_event *event);
 
static struct ast_calendar_tech ewscal_tech = {
    .type = "ews",
    .description = "MS Exchange Web Service calendars",
    .module = AST_MODULE,
    .load_calendar = ewscal_load_calendar,
    .unref_calendar = unref_ewscal,
    .write_event = ewscal_write_event,
};
 
enum xml_op {
    XML_OP_FIND = 100,
    XML_OP_GET,
    XML_OP_CREATE,
};
 
struct calendar_id {
    struct ast_str *id;
    AST_LIST_ENTRY(calendar_id) next;
};
 
struct xml_context {
    ne_xml_parser *parser;
    struct ast_str *cdata;
    struct ast_calendar_event *event;
    enum xml_op op;
    struct ewscal_pvt *pvt;
    AST_LIST_HEAD_NOLOCK(ids, calendar_id) ids;
};
 
/* Important states of XML parsing */
enum {
    XML_EVENT_CALENDAR_ITEM = 9,
    XML_EVENT_NAME = 10,
    XML_EVENT_DESCRIPTION,
    XML_EVENT_START,
    XML_EVENT_END,
    XML_EVENT_BUSY,
    XML_EVENT_ORGANIZER,
    XML_EVENT_LOCATION,
    XML_EVENT_ATTENDEE_LIST,
    XML_EVENT_ATTENDEE,
    XML_EVENT_MAILBOX,
    XML_EVENT_EMAIL_ADDRESS,
    XML_EVENT_CATEGORIES,
    XML_EVENT_CATEGORY,
    XML_EVENT_IMPORTANCE,
};
 
struct ewscal_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;
    unsigned int items;
};
 
static void ewscal_destructor(void *obj)
{
    struct ewscal_pvt *pvt = obj;
 
    ast_debug(1, "Destroying pvt for Exchange Web Service 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_ewscal(void *obj)
{
    struct ewscal_pvt *pvt = obj;
 
    ast_debug(5, "EWS: unref_ewscal()\n");
    ao2_ref(pvt, -1);
    return NULL;
}
 
static int auth_credentials(void *userdata, const char *realm, int attempts, char *username, char *secret)
{
    struct ewscal_pvt *pvt = userdata;
 
    if (attempts > 1) {
        ast_log(LOG_WARNING, "Invalid username or password for Exchange Web Service 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 ssl_verify(void *userdata, int failures, const ne_ssl_certificate *cert)
{
    struct ewscal_pvt *pvt = userdata;
    if (failures & NE_SSL_UNTRUSTED) {
        ast_log(LOG_WARNING, "Untrusted SSL certificate for calendar %s!\n", pvt->owner->name);
        return 0;
    }
    return 1;   /* NE_SSL_NOTYETVALID, NE_SSL_EXPIRED, NE_SSL_IDMISMATCH */
}
 
static time_t mstime_to_time_t(char *mstime)
{
    struct ast_tm tm;
    struct timeval tv;
 
    if (ast_strptime(mstime, "%FT%TZ", &tm)) {
        tv = ast_mktime(&tm, "UTC");
        return tv.tv_sec;
    }
    return 0;
}
 
static int startelm(void *userdata, int parent, const char *nspace, const char *name, const char **atts)
{
    struct xml_context *ctx = userdata;
 
    ast_debug(5, "EWS: XML: Start: %s\n", name);
    if (ctx->op == XML_OP_CREATE) {
        return NE_XML_DECLINE;
    }
 
    /* Nodes needed for traversing until CalendarItem is found */
    if (!strcmp(name, "Envelope") ||
        (!strcmp(name, "Body") && parent != XML_EVENT_CALENDAR_ITEM) ||
        !strcmp(name, "FindItemResponse") ||
        !strcmp(name, "GetItemResponse") ||
        !strcmp(name, "CreateItemResponse") ||
        !strcmp(name, "ResponseMessages") ||
        !strcmp(name, "FindItemResponseMessage") || !strcmp(name, "GetItemResponseMessage") ||
        !strcmp(name, "Items")
    ) {
        return 1;
    } else if (!strcmp(name, "RootFolder")) {
        /* Get number of events */
        unsigned int items;
 
        ast_debug(3, "EWS: XML: <RootFolder>\n");
        if (sscanf(ne_xml_get_attr(ctx->parser, atts, NULL, "TotalItemsInView"), "%u", &items) != 1) {
            /* Couldn't read enything */
            ne_xml_set_error(ctx->parser, "Could't read number of events.");
            return NE_XML_ABORT;
        }
 
        ast_debug(3, "EWS: %u calendar items to load\n", items);
        ctx->pvt->items = items;
        if (items < 1) {
            /* Stop processing XML if there are no events */
            ast_calendar_merge_events(ctx->pvt->owner, ctx->pvt->events);
            return NE_XML_DECLINE;
        }
        return 1;
    } else if (!strcmp(name, "CalendarItem")) {
        /* Event start */
        ast_debug(3, "EWS: XML: <CalendarItem>\n");
        if (!(ctx->pvt && ctx->pvt->owner)) {
            ast_log(LOG_ERROR, "Require a private structure with an owner\n");
            return NE_XML_ABORT;
        }
 
        ctx->event = ast_calendar_event_alloc(ctx->pvt->owner);
        if (!ctx->event) {
            ast_log(LOG_ERROR, "Could not allocate an event!\n");
            return NE_XML_ABORT;
        }
 
        ctx->cdata = ast_str_create(64);
        if (!ctx->cdata) {
            ast_log(LOG_ERROR, "Could not allocate CDATA!\n");
            return NE_XML_ABORT;
        }
 
        return XML_EVENT_CALENDAR_ITEM;
    } else if (!strcmp(name, "ItemId")) {
        /* Event UID */
        if (ctx->op == XML_OP_FIND) {
            struct calendar_id *id;
            if (!(id = ast_calloc(1, sizeof(*id)))) {
                return NE_XML_ABORT;
            }
            if (!(id->id = ast_str_create(256))) {
                ast_free(id);
                return NE_XML_ABORT;
            }
            ast_str_set(&id->id, 0, "%s", ne_xml_get_attr(ctx->parser, atts, NULL, "Id"));
            AST_LIST_INSERT_TAIL(&ctx->ids, id, next);
            ast_debug(3, "EWS_FIND: XML: UID: %s\n", ast_str_buffer(id->id));
        } else {
            ast_debug(3, "EWS_GET: XML: UID: %s\n", ne_xml_get_attr(ctx->parser, atts, NULL, "Id"));
            ast_string_field_set(ctx->event, uid, ne_xml_get_attr(ctx->parser, atts, NULL, "Id"));
        }
        return XML_EVENT_NAME;
    } else if (!strcmp(name, "Subject")) {
        /* Event name */
        if (!ctx->cdata) {
            return NE_XML_ABORT;
        }
        ast_str_reset(ctx->cdata);
        return XML_EVENT_NAME;
    } else if (!strcmp(name, "Body") && parent == XML_EVENT_CALENDAR_ITEM) {
        /* Event body/description */
        if (!ctx->cdata) {
            return NE_XML_ABORT;
        }
        ast_str_reset(ctx->cdata);
        return XML_EVENT_DESCRIPTION;
    } else if (!strcmp(name, "Start")) {
        /* Event start time */
        return XML_EVENT_START;
    } else if (!strcmp(name, "End")) {
        /* Event end time */
        return XML_EVENT_END;
    } else if (!strcmp(name, "LegacyFreeBusyStatus")) {
        /* Event busy state */
        return XML_EVENT_BUSY;
    } else if (!strcmp(name, "Organizer") ||
            (parent == XML_EVENT_ORGANIZER && (!strcmp(name, "Mailbox") ||
            !strcmp(name, "Name")))) {
        /* Event organizer */
        if (!ctx->cdata) {
            return NE_XML_ABORT;
        }
        ast_str_reset(ctx->cdata);
        return XML_EVENT_ORGANIZER;
    } else if (!strcmp(name, "Location")) {
        /* Event location */
        if (!ctx->cdata) {
            return NE_XML_ABORT;
        }
        ast_str_reset(ctx->cdata);
        return XML_EVENT_LOCATION;
    } else if (!strcmp(name, "Categories")) {
        /* Event categories */
        if (!ctx->cdata) {
            return NE_XML_ABORT;
        }
        ast_str_reset(ctx->cdata);
        return XML_EVENT_CATEGORIES;
    } else if (parent == XML_EVENT_CATEGORIES && !strcmp(name, "String")) {
        /* Event category */
        return XML_EVENT_CATEGORY;
    } else if (!strcmp(name, "Importance")) {
        /* Event importance (priority) */
        if (!ctx->cdata) {
            return NE_XML_ABORT;
        }
        ast_str_reset(ctx->cdata);
        return XML_EVENT_IMPORTANCE;
    } else if (!strcmp(name, "RequiredAttendees") || !strcmp(name, "OptionalAttendees")) {
        return XML_EVENT_ATTENDEE_LIST;
    } else if (!strcmp(name, "Attendee") && parent == XML_EVENT_ATTENDEE_LIST) {
        return XML_EVENT_ATTENDEE;
    } else if (!strcmp(name, "Mailbox") && parent == XML_EVENT_ATTENDEE) {
        return XML_EVENT_MAILBOX;
    } else if (!strcmp(name, "EmailAddress") && parent == XML_EVENT_MAILBOX) {
        if (!ctx->cdata) {
            return NE_XML_ABORT;
        }
        ast_str_reset(ctx->cdata);
        return XML_EVENT_EMAIL_ADDRESS;
    }
 
    return NE_XML_DECLINE;
}
 
static int cdata(void *userdata, int state, const char *cdata, size_t len)
{
    struct xml_context *ctx = userdata;
    char data[len + 1];
 
    /* !!! DON'T USE AST_STRING_FIELD FUNCTIONS HERE, JUST COLLECT CTX->CDATA !!! */
    if (state < XML_EVENT_NAME || ctx->op == XML_OP_CREATE) {
        return 0;
    }
 
    if (!ctx->event) {
        ast_log(LOG_ERROR, "Parsing event data, but event object does not exist!\n");
        return 1;
    }
 
    if (!ctx->cdata) {
        ast_log(LOG_ERROR, "String for storing CDATA is unitialized!\n");
        return 1;
    }
 
    ast_copy_string(data, cdata, len + 1);
 
    switch (state) {
    case XML_EVENT_START:
        ctx->event->start = mstime_to_time_t(data);
        break;
    case XML_EVENT_END:
        ctx->event->end = mstime_to_time_t(data);
        break;
    case XML_EVENT_BUSY:
        if (!strcmp(data, "Busy") || !strcmp(data, "OOF")) {
            ast_debug(3, "EWS: XML: Busy: yes\n");
            ctx->event->busy_state = AST_CALENDAR_BS_BUSY;
        }
        else if (!strcmp(data, "Tentative")) {
            ast_debug(3, "EWS: XML: Busy: tentative\n");
            ctx->event->busy_state = AST_CALENDAR_BS_BUSY_TENTATIVE;
        }
        else {
            ast_debug(3, "EWS: XML: Busy: no\n");
            ctx->event->busy_state = AST_CALENDAR_BS_FREE;
        }
        break;
    case XML_EVENT_CATEGORY:
        if (ast_str_strlen(ctx->cdata) == 0) {
            ast_str_set(&ctx->cdata, 0, "%s", data);
        } else {
            ast_str_append(&ctx->cdata, 0, ",%s", data);
        }
        break;
    default:
        ast_str_append(&ctx->cdata, 0, "%s", data);
    }
 
    ast_debug(5, "EWS: XML: CDATA: %s\n", ast_str_buffer(ctx->cdata));
 
    return 0;
}
 
static int endelm(void *userdata, int state, const char *nspace, const char *name)
{
    struct xml_context *ctx = userdata;
 
    ast_debug(5, "EWS: XML: End:   %s\n", name);
    if (ctx->op == XML_OP_FIND || ctx->op == XML_OP_CREATE) {
        return NE_XML_DECLINE;
    }
 
    if (!strcmp(name, "Subject")) {
        /* Event name end*/
        ast_string_field_set(ctx->event, summary, ast_str_buffer(ctx->cdata));
        ast_debug(3, "EWS: XML: Summary: %s\n", ctx->event->summary);
        ast_str_reset(ctx->cdata);
    } else if (!strcmp(name, "Body") && state == XML_EVENT_DESCRIPTION) {
        /* Event body/description end */
        ast_string_field_set(ctx->event, description, ast_str_buffer(ctx->cdata));
        ast_debug(3, "EWS: XML: Description: %s\n", ctx->event->description);
        ast_str_reset(ctx->cdata);
    } else if (!strcmp(name, "Organizer")) {
        /* Event organizer end */
        ast_string_field_set(ctx->event, organizer, ast_str_buffer(ctx->cdata));
        ast_debug(3, "EWS: XML: Organizer: %s\n", ctx->event->organizer);
        ast_str_reset(ctx->cdata);
    } else if (!strcmp(name, "Location")) {
        /* Event location end */
        ast_string_field_set(ctx->event, location, ast_str_buffer(ctx->cdata));
        ast_debug(3, "EWS: XML: Location: %s\n", ctx->event->location);
        ast_str_reset(ctx->cdata);
    } else if (!strcmp(name, "Categories")) {
        /* Event categories end */
        ast_string_field_set(ctx->event, categories, ast_str_buffer(ctx->cdata));
        ast_debug(3, "EWS: XML: Categories: %s\n", ctx->event->categories);
        ast_str_reset(ctx->cdata);
    } else if (!strcmp(name, "Importance")) {
        /* Event importance end */
        if (!strcmp(ast_str_buffer(ctx->cdata), "Low")) {
            ctx->event->priority = 9;
        } else if (!strcmp(ast_str_buffer(ctx->cdata), "Normal")) {
            ctx->event->priority = 5;
        } else if (!strcmp(ast_str_buffer(ctx->cdata), "High")) {
            ctx->event->priority = 1;
        }
        ast_debug(3, "EWS: XML: Importance: %s (%d)\n", ast_str_buffer(ctx->cdata), ctx->event->priority);
        ast_str_reset(ctx->cdata);
    } else if (state == XML_EVENT_EMAIL_ADDRESS) {
        struct ast_calendar_attendee *attendee;
 
        if (!(attendee = ast_calloc(1, sizeof(*attendee)))) {
            ctx->event = ast_calendar_unref_event(ctx->event);
            return  1;
        }
 
        if (ast_str_strlen(ctx->cdata)) {
            attendee->data = ast_strdup(ast_str_buffer(ctx->cdata));
            AST_LIST_INSERT_TAIL(&ctx->event->attendees, attendee, next);
        } else {
            ast_free(attendee);
        }
        ast_debug(3, "EWS: XML: attendee address '%s'\n", ast_str_buffer(ctx->cdata));
        ast_str_reset(ctx->cdata);
    } else if (!strcmp(name, "CalendarItem")) {
        /* Event end */
        ast_debug(3, "EWS: XML: </CalendarItem>\n");
        ast_free(ctx->cdata);
        if (ctx->event) {
            ao2_link(ctx->pvt->events, ctx->event);
            ctx->event = ast_calendar_unref_event(ctx->event);
        } else {
            ast_log(LOG_ERROR, "Event data ended in XML, but event object does not exist!\n");
            return 1;
        }
    } else if (!strcmp(name, "Envelope")) {
        /* Events end */
        ast_debug(3, "EWS: XML: %d of %u event(s) has been parsed…\n", ao2_container_count(ctx->pvt->events), ctx->pvt->items);
        if (ao2_container_count(ctx->pvt->events) >= ctx->pvt->items) {
            ast_debug(3, "EWS: XML: All events has been parsed, merging…\n");
            ast_calendar_merge_events(ctx->pvt->owner, ctx->pvt->events);
        }
    }
 
    return 0;
}
 
static const char *mstime(time_t t, char *buf, size_t buflen)
{
    struct timeval tv = {
        .tv_sec = t,
    };
    struct ast_tm tm;
 
    ast_localtime(&tv, &tm, "utc");
    ast_strftime(buf, buflen, "%FT%TZ", &tm);
 
    return S_OR(buf, "");
}
 
static const char *msstatus(enum ast_calendar_busy_state state)
{
    switch (state) {
    case AST_CALENDAR_BS_BUSY_TENTATIVE:
        return "Tentative";
    case AST_CALENDAR_BS_BUSY:
        return "Busy";
    case AST_CALENDAR_BS_FREE:
        return "Free";
    default:
        return "";
    }
}
 
static const char *get_soap_action(enum xml_op op)
{
    switch (op) {
    case XML_OP_FIND:
        return "\"http://schemas.microsoft.com/exchange/services/2006/messages/FindItem\"";
    case XML_OP_GET:
        return "\"http://schemas.microsoft.com/exchange/services/2006/messages/GetItem\"";
    case XML_OP_CREATE:
        return "\"http://schemas.microsoft.com/exchange/services/2006/messages/CreateItem\"";
    }
 
    return "";
}
 
static int send_ews_request_and_parse(struct ast_str *request, struct xml_context *ctx)
{
    int ret;
    ne_request *req;
    ne_xml_parser *parser;
 
    ast_debug(3, "EWS: HTTP request...\n");
    if (!(ctx && ctx->pvt)) {
        ast_log(LOG_ERROR, "There is no private!\n");
        return -1;
    }
 
    if (!ast_str_strlen(request)) {
        ast_log(LOG_ERROR, "No request to send!\n");
        return -1;
    }
 
    ast_debug(3, "%s\n", ast_str_buffer(request));
 
    /* Prepare HTTP POST request */
    req = ne_request_create(ctx->pvt->session, "POST", ctx->pvt->uri.path);
    ne_set_request_flag(req, NE_REQFLAG_IDEMPOTENT, 0);
 
    /* Set headers--should be application/soap+xml, but MS… :/ */
    ne_add_request_header(req, "Content-Type", "text/xml; charset=utf-8");
    ne_add_request_header(req, "SOAPAction", get_soap_action(ctx->op));
 
    /* Set body to SOAP request */
    ne_set_request_body_buffer(req, ast_str_buffer(request), ast_str_strlen(request));
 
    /* Prepare XML parser */
    parser = ne_xml_create();
    ctx->parser = parser;
    ne_xml_push_handler(parser, startelm, cdata, endelm, ctx);  /* Callbacks */
 
    /* Dispatch request and parse response as XML */
    ret = ne_xml_dispatch_request(req, parser);
    if (ret != NE_OK) { /* Error handling */
        ast_log(LOG_WARNING, "Unable to communicate with Exchange Web Service at '%s': %s\n", ctx->pvt->url, ne_get_error(ctx->pvt->session));
        ne_request_destroy(req);
        ne_xml_destroy(parser);
        return -1;
    }
 
    /* Cleanup */
    ne_request_destroy(req);
    ne_xml_destroy(parser);
 
    return 0;
}
 
static int ewscal_write_event(struct ast_calendar_event *event)
{
    struct ast_str *request;
    struct ewscal_pvt *pvt = event->owner->tech_pvt;
    char start[21], end[21];
    struct xml_context ctx = {
        .op = XML_OP_CREATE,
        .pvt = pvt,
    };
    int ret;
    char *category, *categories;
 
    if (!pvt) {
        return -1;
    }
 
    if (!(request = ast_str_create(1024))) {
        return -1;
    }
 
    ast_str_set(&request, 0,
        "<soap:Envelope xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" "
            "xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\" "
            "xmlns:soap=\"http://schemas.xmlsoap.org/soap/envelope/\" "
            "xmlns:t=\"http://schemas.microsoft.com/exchange/services/2006/types\">"
            "<soap:Body>"
            "<CreateItem xmlns=\"http://schemas.microsoft.com/exchange/services/2006/messages\" "
                "xmlns:t=\"http://schemas.microsoft.com/exchange/services/2006/types\" "
                "SendMeetingInvitations=\"SendToNone\" >"
                "<SavedItemFolderId>"
                    "<t:DistinguishedFolderId Id=\"calendar\"/>"
                "</SavedItemFolderId>"
                "<Items>"
                    "<t:CalendarItem xmlns=\"http://schemas.microsoft.com/exchange/services/2006/types\">"
                        "<Subject>%s</Subject>"
                        "<Body BodyType=\"Text\">%s</Body>"
                        "<ReminderIsSet>false</ReminderIsSet>"
                        "<Start>%s</Start>"
                        "<End>%s</End>"
                        "<IsAllDayEvent>false</IsAllDayEvent>"
                        "<LegacyFreeBusyStatus>%s</LegacyFreeBusyStatus>"
                        "<Location>%s</Location>",
        event->summary,
        event->description,
        mstime(event->start, start, sizeof(start)),
        mstime(event->end, end, sizeof(end)),
        msstatus(event->busy_state),
        event->location
    );
    /* Event priority */
    switch (event->priority) {
    case 1:
    case 2:
    case 3:
    case 4:
        ast_str_append(&request, 0, "<Importance>High</Importance>");
        break;
    case 5:
        ast_str_append(&request, 0, "<Importance>Normal</Importance>");
        break;
    case 6:
    case 7:
    case 8:
    case 9:
        ast_str_append(&request, 0, "<Importance>Low</Importance>");
        break;
    }
    /* Event categories*/
    if (strlen(event->categories) > 0) {
        ast_str_append(&request, 0, "<Categories>");
        categories = ast_strdupa(event->categories);    /* Duplicate string, since strsep() is destructive */
        category = strsep(&categories, ",");
        while (category != NULL) {
            ast_str_append(&request, 0, "<String>%s</String>", category);
            category = strsep(&categories, ",");
        }
        ast_str_append(&request, 0, "</Categories>");
    }
    /* Finish request */
    ast_str_append(&request, 0, "</t:CalendarItem></Items></CreateItem></soap:Body></soap:Envelope>");
 
    ret = send_ews_request_and_parse(request, &ctx);
 
    ast_free(request);
 
    return ret;
}
 
static struct calendar_id *get_ewscal_ids_for(struct ewscal_pvt *pvt)
{
    char start[21], end[21];
    struct ast_tm tm;
    struct timeval tv;
    struct ast_str *request;
    struct xml_context ctx = {
        .op = XML_OP_FIND,
        .pvt = pvt,
    };
 
    ast_debug(5, "EWS: get_ewscal_ids_for()\n");
 
    if (!pvt) {
        ast_log(LOG_ERROR, "There is no private!\n");
        return NULL;
    }
 
    /* Prepare timeframe strings */
    tv = ast_tvnow();
    ast_localtime(&tv, &tm, "UTC");
    ast_strftime(start, sizeof(start), "%FT%TZ", &tm);
    tv.tv_sec += 60 * pvt->owner->timeframe;
    ast_localtime(&tv, &tm, "UTC");
    ast_strftime(end, sizeof(end), "%FT%TZ", &tm);
 
    /* Prepare SOAP request */
    if (!(request = ast_str_create(512))) {
        return NULL;
    }
 
    ast_str_set(&request, 0,
        "<SOAP-ENV:Envelope xmlns:SOAP-ENV=\"http://schemas.xmlsoap.org/soap/envelope/\" "
        "xmlns:ns1=\"http://schemas.microsoft.com/exchange/services/2006/types\" "
        "xmlns:ns2=\"http://schemas.microsoft.com/exchange/services/2006/messages\">"
            "<SOAP-ENV:Body>"
                "<ns2:FindItem Traversal=\"Shallow\">"
                    "<ns2:ItemShape>"
                        "<ns1:BaseShape>IdOnly</ns1:BaseShape>"
                    "</ns2:ItemShape>"
                    "<ns2:CalendarView StartDate=\"%s\" EndDate=\"%s\"/>"   /* Timeframe */
                    "<ns2:ParentFolderIds>"
                        "<ns1:DistinguishedFolderId Id=\"calendar\"/>"
                    "</ns2:ParentFolderIds>"
                "</ns2:FindItem>"
            "</SOAP-ENV:Body>"
        "</SOAP-ENV:Envelope>",
        start, end  /* Timeframe */
    );
 
    AST_LIST_HEAD_INIT_NOLOCK(&ctx.ids);
 
    /* Dispatch request and parse response as XML */
    if (send_ews_request_and_parse(request, &ctx)) {
        ast_free(request);
        return NULL;
    }
 
    /* Cleanup */
    ast_free(request);
 
    return AST_LIST_FIRST(&ctx.ids);
}
 
static int parse_ewscal_id(struct ewscal_pvt *pvt, const char *id) {
    struct ast_str *request;
    struct xml_context ctx = {
        .pvt = pvt,
        .op = XML_OP_GET,
    };
 
    if (!(request = ast_str_create(512))) {
        return -1;
    }
 
    ast_str_set(&request, 0,
        "<?xml version=\"1.0\" encoding=\"utf-8\"?>"
        "<soap:Envelope xmlns:soap=\"http://schemas.xmlsoap.org/soap/envelope/\" "
        "xmlns:t=\"http://schemas.microsoft.com/exchange/services/2006/types\">"
        "<soap:Body>"
            "<GetItem xmlns=\"http://schemas.microsoft.com/exchange/services/2006/messages\">"
                "<ItemShape>"
                    "<t:BaseShape>AllProperties</t:BaseShape>"
                "</ItemShape>"
                "<ItemIds>"
                    "<t:ItemId Id=\"%s\"/>"
                "</ItemIds>"
            "</GetItem>"
        "</soap:Body>"
        "</soap:Envelope>", id
    );
 
    if (send_ews_request_and_parse(request, &ctx)) {
        ast_free(request);
        return -1;
    }
 
    ast_free(request);
 
    return 0;
}
 
static int update_ewscal(struct ewscal_pvt *pvt)
{
    struct calendar_id *id_head;
    struct calendar_id *iter;
 
    if (!(id_head = get_ewscal_ids_for(pvt))) {
        return 0;
    }
 
    for (iter = id_head; iter; iter = AST_LIST_NEXT(iter, next)) {
        parse_ewscal_id(pvt, ast_str_buffer(iter->id));
        ast_free(iter->id);
        ast_free(iter);
    }
 
    return 0;
}
 
static void *ewscal_load_calendar(void *void_data)
{
    struct ewscal_pvt *pvt;
    const struct ast_config *cfg;
    struct ast_variable *v;
    struct ast_calendar *cal = void_data;
    ast_mutex_t refreshlock;
 
    ast_debug(5, "EWS: ewscal_load_calendar()\n");
 
    if (!(cal && (cfg = ast_calendar_config_acquire()))) {
        ast_log(LOG_ERROR, "You must enable calendar support for res_ewscal 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), ewscal_destructor))) {
        ast_log(LOG_ERROR, "Could not allocate ewscal_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_ewscal(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_ewscal(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 Exchange Web Service calendar '%s' - skipping.\n", cal->name);
        pvt = unref_ewscal(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 Exchange Web Service calendar '%s' - skipping.\n", pvt->url, cal->name);
        pvt = unref_ewscal(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);
    }
 
    ast_debug(3, "ne_uri.scheme = %s\n", pvt->uri.scheme);
    ast_debug(3, "ne_uri.host   = %s\n", pvt->uri.host);
    ast_debug(3, "ne_uri.port   = %u\n", pvt->uri.port);
    ast_debug(3, "ne_uri.path   = %s\n", pvt->uri.path);
    ast_debug(3, "user      = %s\n", pvt->user);
    ast_debug(3, "secret        = %s\n", pvt->secret);
 
    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);
    ne_set_useragent(pvt->session, "Asterisk");
 
    if (!strcasecmp(pvt->uri.scheme, "https")) {
        ne_ssl_trust_default_ca(pvt->session);
        ne_ssl_set_verify(pvt->session, ssl_verify, pvt);
    }
 
    cal->tech_pvt = pvt;
 
    ast_mutex_init(&refreshlock);
 
    /* Load it the first time */
    update_ewscal(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_ewscal(pvt);
    }
 
    return NULL;
}
 
static int load_module(void)
{
    /* Actualy, 0.29.1 is required (because of NTLM authentication), but this
     * function does not support matching patch version.
     *
     * The ne_version_match function returns non-zero if the library
     * version is not of major version major, or the minor version
     * is less than minor. For neon versions 0.x, every minor
     * version is assumed to be incompatible with every other minor
     * version.
     *
     * I.e. for version 1.2..1.9 we would do ne_version_match(1, 2)
     * but for version 0.29 and 0.30 we need two checks. */
    if (ne_version_match(0, 29) && ne_version_match(0, 30)) {
        ast_log(LOG_ERROR, "Exchange Web Service calendar module require neon >= 0.29.1, but %s is installed.\n", ne_version_string());
        return AST_MODULE_LOAD_DECLINE;
    }
 
    if (ast_calendar_register(&ewscal_tech) && (ne_sock_init() == 0)) {
        return AST_MODULE_LOAD_DECLINE;
    }
 
    return AST_MODULE_LOAD_SUCCESS;
}
 
static int unload_module(void)
{
    ne_sock_exit();
    ast_calendar_unregister(&ewscal_tech);
 
    return 0;
}
 
AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "Asterisk MS Exchange Web Service Calendar Integration",
    .support_level = AST_MODULE_SUPPORT_EXTENDED,
    .load = load_module,
    .unload = unload_module,
    .load_pri = AST_MODPRI_DEVSTATE_PLUGIN,
    .requires = "res_calendar",
);