From a59c42e5caa76a5ea1d5e79b7820a1a012f9a3a4 Mon Sep 17 00:00:00 2001
From: cbdev <cb@cbcdn.com>
Date: Sat, 14 Nov 2020 15:21:53 +0100
Subject: MQTT backend skeleton

---
 backends/mqtt.c | 108 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 backends/mqtt.h |  48 +++++++++++++++++++++++++
 2 files changed, 156 insertions(+)
 create mode 100644 backends/mqtt.c
 create mode 100644 backends/mqtt.h

diff --git a/backends/mqtt.c b/backends/mqtt.c
new file mode 100644
index 0000000..4f56aa6
--- /dev/null
+++ b/backends/mqtt.c
@@ -0,0 +1,108 @@
+#define BACKEND_NAME "mqtt"
+
+#include <string.h>
+#include "mqtt.h"
+
+MM_PLUGIN_API int init(){
+	backend mqtt = {
+		.name = BACKEND_NAME,
+		.conf = mqtt_configure,
+		.create = mqtt_instance,
+		.conf_instance = mqtt_configure_instance,
+		.channel = mqtt_channel,
+		.handle = mqtt_set,
+		.process = mqtt_handle,
+		.start = mqtt_start,
+		.shutdown = mqtt_shutdown
+	};
+
+	//register backend
+	if(mm_backend_register(mqtt)){
+		LOG("Failed to register backend");
+		return 1;
+	}
+	return 0;
+}
+
+static size_t mqtt_varint_decode(uint8_t* buffer, uint32_t* result){
+	//TODO
+	return 0;
+}
+
+static int mqtt_configure(char* option, char* value){
+	LOG("This backend does not take global configuration");
+	return 1;
+}
+
+static int mqtt_configure_instance(instance* inst, char* option, char* value){
+	mqtt_instance_data* data = (mqtt_instance_data*) inst->impl;
+	char* token = value;
+
+	if(!strcmp(option, "user")){
+		free(data->user);
+		data->user = strdup(value);
+		return 0;
+	}
+	else if(!strcmp(option, "password")){
+		free(data->password);
+		data->user = strdup(value);
+		return 0;
+	}
+	else if(!strcmp(option, "host")){
+		//mqtt url may be of the form
+		//mqtt[s]://[username][:password]@host.domain[:port]
+		token = strchr(value, ':');
+		//TODO
+	}
+
+	LOGPF("Unknown instance configuration option %s on instance %s", option, inst->name);
+	return 1;
+}
+
+static int mqtt_instance(instance* inst){
+	//TODO
+	return 0;
+}
+
+static channel* mqtt_channel(instance* inst, char* spec, uint8_t flags){
+	//TODO
+	return NULL;
+}
+
+static int mqtt_set(instance* inst, size_t num, channel** c, channel_value* v){
+	//TODO
+	return 0;
+}
+
+static int mqtt_handle(size_t num, managed_fd* fds){
+	//TODO
+	return 0;
+}
+
+static int mqtt_start(size_t n, instance** inst){
+	//TODO
+	return 0;
+}
+
+static int mqtt_shutdown(size_t n, instance** inst){
+	size_t u, p;
+	mqtt_instance_data* data = NULL;
+
+	for(u = 0; u < n; u++){
+		data = (mqtt_instance_data*) inst[u]->impl;
+		for(p = 0; p < data->nchannels; p++){
+			free(data->channel[p]);
+		}
+		free(data->channel);
+		free(data->host);
+		free(data->port);
+		free(data->user);
+		free(data->password);
+
+		free(inst[u]->impl);
+		inst[u]->impl = NULL;
+	}
+
+	LOG("Backend shut down");
+	return 0;
+}
diff --git a/backends/mqtt.h b/backends/mqtt.h
new file mode 100644
index 0000000..165f2ba
--- /dev/null
+++ b/backends/mqtt.h
@@ -0,0 +1,48 @@
+#include "midimonster.h"
+
+MM_PLUGIN_API int init();
+static int mqtt_configure(char* option, char* value);
+static int mqtt_configure_instance(instance* inst, char* option, char* value);
+static int mqtt_instance(instance* inst);
+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);
+static int mqtt_handle(size_t num, managed_fd* fds);
+static int mqtt_start(size_t n, instance** inst);
+static int mqtt_shutdown(size_t n, instance** inst);
+
+#define MQTT_PORT "1883"
+#define MQTT_TLS_PORT "8883"
+
+enum {
+	MSG_RESERVED = 0x00,
+	MSG_CONNECT = 0x10,
+	MSG_CONNACK = 0x20,
+	MSG_PUBLISH = 0x30,
+	MSG_PUBACK = 0x40,
+	MSG_PUBREC = 0x50,
+	MSG_PUBREL = 0x60,
+	MSG_PUBCOMP = 0x70,
+	MSG_SUBSCRIBE = 0x80,
+	MSG_SUBACK = 0x90,
+	MSG_UNSUBSCRIBE = 0xA0,
+	MSG_UNSUBACK = 0xB0,
+	MSG_PINGREQ = 0xC0,
+	MSG_PINGRESP = 0xD0,
+	MSG_DISCONNECT = 0xE0,
+	MSG_AUTH = 0xF0
+};
+
+typedef struct /*_mqtt_instance_data*/ {
+	uint8_t tls;
+	char* host;
+	char* port;
+
+	char* user;
+	char* password;
+
+	size_t nchannels;
+	char** channel;
+} mqtt_instance_data;
+
+//per-channel
+//qos, subscribe
-- 
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