res_mwi_devstate.c: New module to allow presence subs to VM boxes

This module allows presence subscriptions to voicemail boxes.  This
allows common BLF keys to act as voicemail waiting indicators.

ASTERISK-28301

Change-Id: I62a246c24f3d7d432e33e22d7a4a57c15c292fdd

CHANGES

@@ -92,6 +92,12 @@ res_pjsip
    RECOMMENDED), keep the current behavior, or trigger only on pjsip
    taskprocessor overloads.
 
+MWI
+------------------
+ * A new module "res_mwi_devstate" has been added that allows subscriptions
+   to voicemail boxes using "presence" events.  This allows common BLF keys
+   to act as voicemail waiting indicators.
+
 ------------------------------------------------------------------------------
 --- Functionality changes from Asterisk 16.1.0 to Asterisk 16.2.0 ------------
 ------------------------------------------------------------------------------

res/res_mwi_devstate.c

@@ -0,0 +1,105 @@
+/*
+ * Asterisk -- An open source telephony toolkit.
+ *
+ * Copyright (C) 2014, Schmooze Com, Inc.
+ *
+ * Jason Parker <jason.parker@schmoozecom.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.
+ */
+
+/*** MODULEINFO
+	<support_level>core</support_level>
+ ***/
+
+#include "asterisk.h"
+
+#include "asterisk/app.h"
+#include "asterisk/devicestate.h"
+#include "asterisk/module.h"
+#include "asterisk/stasis_message_router.h"
+#include "asterisk/stasis.h"
+
+static struct stasis_subscription *mwi_sub;
+
+static void mwi_update_cb(void *data, struct stasis_subscription *sub,
+				    struct stasis_message *msg)
+{
+	struct ast_mwi_state *mwi_state;
+
+	if (ast_mwi_state_type() != stasis_message_type(msg)) {
+		return;
+	}
+
+	mwi_state = stasis_message_data(msg);
+	if (!mwi_state) {
+		return;
+	}
+
+	if (mwi_state->new_msgs > 0) {
+		ast_debug(1, "Sending inuse devstate change for MWI:%s\n", mwi_state->uniqueid);
+		ast_devstate_changed(AST_DEVICE_INUSE, AST_DEVSTATE_CACHABLE, "MWI:%s", mwi_state->uniqueid);
+	} else {
+		ast_debug(1, "Sending not inuse devstate change for MWI:%s\n", mwi_state->uniqueid);
+		ast_devstate_changed(AST_DEVICE_NOT_INUSE, AST_DEVSTATE_CACHABLE, "MWI:%s", mwi_state->uniqueid);
+	}
+}
+
+static int mwi_cached_cb(void *obj, void *arg, int flags)
+{
+	struct stasis_message *msg = obj;
+	mwi_update_cb(NULL, mwi_sub, msg);
+
+	return 0;
+}
+
+static int unload_module(void)
+{
+	mwi_sub = stasis_unsubscribe(mwi_sub);
+
+	return 0;
+}
+
+static int load_module(void)
+{
+	struct ao2_container *cached;
+
+	if (!(mwi_sub = stasis_subscribe(ast_mwi_topic_all(), mwi_update_cb, NULL))) {
+		return AST_MODULE_LOAD_DECLINE;
+	}
+
+	if (stasis_subscription_accept_message_type(mwi_sub, ast_mwi_state_type())) {
+		unload_module();
+		return AST_MODULE_LOAD_DECLINE;
+	}
+
+	if (stasis_subscription_set_filter(mwi_sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE)) {
+		unload_module();
+		return AST_MODULE_LOAD_DECLINE;
+	}
+
+	cached = stasis_cache_dump(ast_mwi_state_cache(), NULL);
+	if (!cached) {
+		unload_module();
+		return AST_MODULE_LOAD_DECLINE;
+	}
+	ao2_callback(cached, OBJ_NODATA, mwi_cached_cb, NULL);
+	ao2_ref(cached, -1);
+
+	return AST_MODULE_LOAD_SUCCESS;
+}
+
+AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_DEFAULT, "MWI Device State Subscriptions",
+	.support_level = AST_MODULE_SUPPORT_CORE,
+	.load = load_module,
+	.unload = unload_module,
+	.load_pri = AST_MODPRI_DEVSTATE_PROVIDER,
+);