From 983313fe782047a5fe84314fafa2eb0b56e0e3a1 Mon Sep 17 00:00:00 2001
From: cbdev <cb@cbcdn.com>
Date: Sat, 6 Feb 2021 22:51:54 +0100
Subject: Implement MQTT output

---
 backends/mqtt.c | 75 ++++++++++++++++++++++++++++++++++++++++++++++++++++++---
 backends/mqtt.h |  3 ++-
 2 files changed, 73 insertions(+), 5 deletions(-)

diff --git a/backends/mqtt.c b/backends/mqtt.c
index d3e516f..00045c0 100644
--- a/backends/mqtt.c
+++ b/backends/mqtt.c
@@ -9,6 +9,14 @@
 
 static uint64_t last_maintenance = 0;
 
+/*
+ * TODO
+ *	* proper RETAIN handling
+ *	* use topic aliases if possible
+ *	* mqtt v3.1.1 local filtering
+ *	* modifiable output mappings
+ */
+
 MM_PLUGIN_API int init(){
 	backend mqtt = {
 		.name = BACKEND_NAME,
@@ -267,13 +275,20 @@ static int mqtt_configure_instance(instance* inst, char* option, char* value){
 			return mqtt_generate_instanceid(inst);
 		}
 	}
+	else if(!strcmp(option, "protocol")){
+		data->mqtt_version = MQTT_VERSION_DEFAULT;
+		if(!strcmp(value, "3.1.1")){
+			data->mqtt_version = 4;
+		}
+		return 0;
+	}
 
 	LOGPF("Unknown instance configuration option %s on instance %s", option, inst->name);
 	return 1;
 }
 
 static int mqtt_push_subscriptions(instance* inst){
-	mqtt_instance_data* data = calloc(1, sizeof(mqtt_instance_data));
+	mqtt_instance_data* data = (mqtt_instance_data*) inst->impl;
 	uint8_t variable_header[3] = {0};
 	uint8_t payload[MQTT_BUFFER_LENGTH];
 	size_t u, subs = 0, payload_offset = 0;
@@ -282,6 +297,7 @@ static int mqtt_push_subscriptions(instance* inst){
 	for(u = 0; u < data->nchannels; u++){
 		payload_offset = 0;
 		if(data->channel[u].flags & mmchannel_input){
+			DBGPF("Subscribing %s.%s, channel %" PRIsize_t ", flags %d", inst->name, data->channel[u].topic, u, data->channel[u].flags);
 			variable_header[0] = (data->packet_identifier >> 8) & 0xFF;
 			variable_header[1] = (data->packet_identifier) & 0xFF;
 
@@ -330,6 +346,7 @@ static channel* mqtt_channel(instance* inst, char* spec, uint8_t flags){
 	for(u = 0; u < data->nchannels; u++){
 		if(!strcmp(spec, data->channel[u].topic)){
 			data->channel[u].flags |= flags;
+			DBGPF("Reusing existing channel %" PRIsize_t " for spec %s.%s, flags are now %02X", u, inst->name, spec, data->channel[u].flags);
 			break;
 		}
 	}
@@ -343,13 +360,16 @@ static channel* mqtt_channel(instance* inst, char* spec, uint8_t flags){
 		}
 
 		data->channel[u].topic = strdup(spec);
-		data->channel[u].topic_alias = 0;
+		data->channel[u].topic_alias_sent = 0;
+		data->channel[u].topic_alias_rcvd = 0;
 		data->channel[u].flags = flags;
 
 		if(!data->channel[u].topic){
 			LOG("Failed to allocate memory");
 			return NULL;
 		}
+		
+		DBGPF("Allocated channel %" PRIsize_t " for spec %s.%s, flags are %02X", u, inst->name, spec, data->channel[u].flags);
 		data->nchannels++;
 	}
 
@@ -357,7 +377,52 @@ static channel* mqtt_channel(instance* inst, char* spec, uint8_t flags){
 }
 
 static int mqtt_set(instance* inst, size_t num, channel** c, channel_value* v){
-	//TODO mqtt v3.1.1 local filtering
+	mqtt_instance_data* data = (mqtt_instance_data*) inst->impl;
+	uint8_t variable_header[MQTT_BUFFER_LENGTH];
+	uint8_t payload[MQTT_BUFFER_LENGTH];
+	size_t vh_length = 0, payload_length = 0;
+	size_t u;
+
+	for(u = 0; u < num; u++){
+		vh_length = payload_length = 0;
+
+		if(data->mqtt_version == 0x05 && data->channel[c[u]->ident].topic_alias_sent){
+			//push zero-length topic
+			variable_header[vh_length++] = 0;
+			variable_header[vh_length++] = 0;
+
+			//push property length
+			variable_header[vh_length++] = 5;
+
+			//push payload type (0x01)
+			variable_header[vh_length++] = 0x01;
+			variable_header[vh_length++] = 1;
+
+			//push topic alias (0x23)
+			variable_header[vh_length++] = 0x23;
+			variable_header[vh_length++] = (data->channel[c[u]->ident].topic_alias_sent >> 8) & 0xFF;
+			variable_header[vh_length++] = data->channel[c[u]->ident].topic_alias_sent & 0xFF;
+		}
+		else{
+			//push topic
+			vh_length += mqtt_push_utf8(variable_header + vh_length, sizeof(variable_header) - vh_length, data->channel[c[u]->ident].topic);
+			if(data->mqtt_version == 0x05){
+				//push property length
+				variable_header[vh_length++] = 2;
+
+				//push payload type (0x01)
+				variable_header[vh_length++] = 0x01;
+				variable_header[vh_length++] = 1;
+			}
+		}
+		payload_length = snprintf((char*) payload, sizeof(payload), "%f", v[u].normalised);
+		//payload_length = snprintf((char*) (payload + 2), sizeof(payload) - 2, "%f", v[u].normalised);
+		//payload[0] = (payload_length >> 8) & 0xFF;
+		//payload[1] = payload_length & 0xFF;
+		//payload_length += 2;
+		mqtt_transmit(inst, MSG_PUBLISH, vh_length, variable_header, payload_length, payload);
+	}
+
 	return 0;
 }
 
@@ -412,7 +477,9 @@ static int mqtt_handle_message(instance* inst, uint8_t type, uint8_t* variable_h
 			}
 			break;
 		case MSG_PINGRESP:
-			//ignore ping responses
+		case MSG_SUBACK:
+			//ignore most responses
+			//FIXME error check SUBACK
 			break;
 		default:
 			LOGPF("Unhandled MQTT message type 0x%02X on %s", type, inst->name);
diff --git a/backends/mqtt.h b/backends/mqtt.h
index c9bce81..6483364 100644
--- a/backends/mqtt.h
+++ b/backends/mqtt.h
@@ -40,7 +40,8 @@ enum {
 //qos, subscribe
 typedef struct /*_mqtt_channel*/ {
 	char* topic;
-	uint16_t topic_alias;
+	uint16_t topic_alias_sent;
+	uint16_t topic_alias_rcvd;
 	uint8_t flags;
 } mqtt_channel_data;
 
-- 
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