MQTTTranslate.h

/* MQTTTranslate uses the ReconnectingMqttClient
   https://github.com/fredilarsen/ReconnectingMqttClient
   library to deliver PJON packets over TCP on local network (LAN) as a MQTT
   protocol client.

   This strategy works in one of four modes.
   The first two modes are for allowing a PJON bus via MQTT, the first mode is
   "closed" and the second is "open" to use by non-PJON programs.
   The last two modes are for behaving like MQTT devices normally do.

   * "Raw bus mode" will send the binary JSON packets delivered to a topic like
     pjon/device45 (where 45 is a receiver device id). Each device
     will subscribe to a topic with its own name and will receive packets like
     from any other PJON strategy. This strategy requires that all senders and
     receivers are linked with PJON for encoding/decoding, so other systems
     are not easily connected.

   * "JSON bus mode" will send JSON packets with to, from and data, delivered
     to a topic like pjon/device45 (where 45 is a receiver device id). Each
     device will subscribe to a topic with its own name and will receive
     packets like
       {to:45,from:44,data:"message text sent from device 44 to device 45"}.

   * "Device mirror, translating" mode will not use JSON encapsulation of
     values, and will publish to its own topic, not the receiver's. It will
     publish to a "output" folder and subscribe to an "input" folder. An
     outgoing packet with payload "P=44.1,T=22.0" would result in the topics
       pjon/device44/output/temperature, with a value "44.1"
       pjon/device44/output/pressure, with a value "22.0"
     Likewise, a receiving an update of:
       pjon/device44/input/setpoint, with a value "45"
     would result in a packet with payload "S=45".
     This mode supports a translation table to allow short names to be used
     in packets while topic names are longer. For example "T" -> "temperature".
     If no translation table is populated, the same names will be used in
     the packets and the topics.

   * "Device mirror, direct" works like the first device mirror mode, but will
     just pass the payload on without any translation, leaving the formatting
     to the user. It will not split packets into separate topics but transfer
     the packets as-is to one output topic and from one input topic:
       pjon/device44/output
       pjon/device44/input
     The user sketch will have control of the format used, which can be
     plain text like "P=44.1,T=22.0" or a JSON text.

   The "Translate" in the strategy name is because a translation table can be
   used to translate PJON packet contents to MQTT topics and back. This is to
   enable PJON packets to remain small ("t=44.3") between devices with limited
   memory, while the MQTT packets are made more explicit ("temperature") to
   support longer name syntax in external systems.

   The preprocessor define MQTTT_USE_MAC can be set when using one of the
   MIRROR modes, to change the topic name from i.e. /pjon/device44/output to
   pjon/AE7804FEA7D0/output. This can be useful to avoid setting a device id
   and instead just use the MAC address as a unique subject identifier.

   Compliant with the PJON protocol layer specification v4.0
   _____________________________________________________________________________

    MQTTTranslate strategy proposed and developed by Fred Larsen 07/12/2019

    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
    You may obtain a copy of the License at

        http://www.apache.org/licenses/LICENSE-2.0

    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License. */

#pragma once
#include <PJONDefines.h>
#include <ReconnectingMqttClient.h>
#ifndef ARDUINO
#include <stdlib.h>
#endif

#define MQTTT_DEFAULT_PORT                   1883
#ifndef MQTTT_RESPONSE_TIMEOUT
  #define MQTTT_RESPONSE_TIMEOUT  (uint32_t) 10000
#endif

// This is the maximum size of MQTT packets after translation
#ifndef MQTTT_BUFFER_SIZE
  #define MQTTT_BUFFER_SIZE  (uint32_t) PJON_PACKET_MAX_LENGTH
#endif

// Max size of key and value in MQTTT_MODE_MIRROR_TRANSLATE mode
#ifndef MQTTT_KEY_SIZE
  #define MQTTT_KEY_SIZE 15
#endif
#ifndef MQTTT_VALUE_SIZE
  #define MQTTT_VALUE_SIZE 15
#endif

#define MQTTT_MODE_BUS_RAW 0
#define MQTTT_MODE_BUS_JSON 1
#define MQTTT_MODE_MIRROR_TRANSLATE 2
#define MQTTT_MODE_MIRROR_DIRECT 3

// Select which mode to use
#ifndef MQTTT_MODE
  #define MQTTT_MODE MQTTT_MODE_BUS_RAW
#endif

// The maximum number of keys to be translated in MIRROR_TRANSLATE mode
#ifndef MQTTT_TRANSLATION_TABLE_SIZE
  #define MQTTT_TRANSLATION_TABLE_SIZE 5
#endif

// Recommended receive time for this strategy, in microseconds
#ifndef MQTTT_RECEIVE_TIME
  #define MQTTT_RECEIVE_TIME 0
#endif

#if defined(MQTTT_USE_MAC) && ((MQTTT_MODE == MQTTT_MODE_MIRROR_TRANSLATE) || (MQTTT_MODE == MQTTT_MODE_MIRROR_DIRECT))
  #define MQTTT_MAC
#endif

class MQTTTranslate {
    bool last_send_success = false;
    
    uint16_t incoming_packet_size = 0;
// TODO: Eliminate extra buffer -- is the on in the MqttClient not enough?    
    uint8_t packet_buffer[MQTTT_BUFFER_SIZE];
    PJON_Packet_Info _packet_info; // Used for parsing incoming and outgoing packets

    #ifdef MQTTT_MAC
    uint8_t mac[6];

    char *add_mac(char *p) {
      sprintf(p, "/%2X%2X%2X%2X%2X%2X", mac[0], mac[1], mac[2], mac[3], mac[4], mac[5]);
      p += strlen(p);
      return p;
    }
    #endif

    #if (MQTTT_MODE == MQTTT_MODE_MIRROR_TRANSLATE)
    char key[MQTTT_KEY_SIZE];
    char value[MQTTT_VALUE_SIZE];
    // Translation table
    uint8_t translation_count = 0;
    char pjon_keys[MQTTT_TRANSLATION_TABLE_SIZE][MQTTT_KEY_SIZE];
    char mqtt_keys[MQTTT_TRANSLATION_TABLE_SIZE][MQTTT_KEY_SIZE];
    
    bool translate(char *key, uint8_t len, bool to_mqtt) {
      for (uint8_t i=0; i<translation_count; i++) {
        if (strcmp(key, to_mqtt ? pjon_keys[i] : mqtt_keys[i]) == 0) {
          strncpy(key, to_mqtt ? mqtt_keys[i] : pjon_keys[i], min(len, MQTTT_KEY_SIZE));
          key[len-1] = 0;
          return true;
        }
      }
      return false;
    }
    #endif

    static void static_receiver(const char *topic, const uint8_t *payload, uint16_t len, void *callback_object) {
      if (callback_object) ((MQTTTranslate*)callback_object)->receiver(topic, payload, len);
    }
    
    #if (MQTTT_MODE == MQTTT_MODE_BUS_JSON)
    bool find_next_json_key(const char **p, const char *last) {
      while (**p && *p < last && **p != '{' && **p != ',') (*p)++; // Find start brace or comma
      if (!**p || *p >= last) return false;
      (*p)++; // Skip start brace or comma {"to":44,"from":"45","data":"sgfsdf"}
      while (**p && *p < last && **p != '\"') (*p)++; // Skip until double quote
      if (**p != '\"' || *p >= last) return false;
      (*p)++; // Point to first char of key
      return true;
    }

    bool find_next_json_value(const char **p, const char *last) {
      while (**p && *p < last && **p != ':') (*p)++; // Find colon
      if (!**p || *p >= last) return false;
      (*p)++; // Skip colon {"to":44,"from":"45","data":"sgfsdf"}
      while (**p && *p < last && (**p == ' ' || **p == '\t')) (*p)++; // Skip potential whitespace
      if (!**p || *p >= last) return false;
      if (**p == '\"' && *p < last) (*p)++; // Skip leading quote if present
      return true;
    }
    #endif

    void receiver(const char *topic, const uint8_t *payload, uint16_t len) {
      #if (MQTTT_MODE == MQTTT_MODE_BUS_RAW)
      if(len <= MQTTT_BUFFER_SIZE) {
        memcpy(packet_buffer, payload, len);
        incoming_packet_size = len;
      }
      #endif
      #if (MQTTT_MODE == MQTTT_MODE_BUS_JSON)
      // Must assume that payload is text, unless UUencoding/base64encoding
      // {"to": to_id, "from": from id, "data": "payload"}
      uint8_t sender_id = 0, receiver_id = 0;
      const char *p = (const char*)payload, *last = p+len-1;
      bool found = false;
      while (find_next_json_key(&p, last)) { // to, from or data
        if (strncmp(p, "to\"", 3)==0 && find_next_json_value(&p, last)) receiver_id = atoi(p);
        else if (strncmp(p, "from\"", 5)==0 && find_next_json_value(&p, last)) sender_id = atoi(p);
        else if (strncmp(p, "data\"", 5)==0 && find_next_json_value(&p, last)) {
          const char *p2 = p;
          while (p2-(const char*)payload+1 < len && *p2 && *p2 != '\"') p2++;
          if (*p2 == '\"') { found = true; payload = (uint8_t*)p; len = p2 - p; }
        }
      }
      if (receiver_id == 0 || !found) return;
      // Package the data message into a PJON packet
      uint8_t h = header;
      if (sender_id != 0) header |= PJON_TX_INFO_BIT;
      incoming_packet_size = PJONTools::compose_packet(sender_id, bus_id, receiver_id,
        bus_id, packet_buffer, payload, len, h);
      #endif
      #if (MQTTT_MODE == MQTTT_MODE_MIRROR_TRANSLATE || MQTTT_MODE == MQTTT_MODE_MIRROR_DIRECT)
        uint8_t receiver_id = my_id;
        #ifdef MQTTT_MAC
        // Parse topic to get source device MAC
        const char *device_start = strstr(topic, "/");
        #else
        // Parse topic to get source device id
        const char *device_start = strstr(topic, "/device");
        if (device_start) receiver_id = (uint8_t) atoi(&device_start[7]);
        #endif
      #endif
      #if (MQTTT_MODE == MQTTT_MODE_MIRROR_TRANSLATE)
      // Split into multiple topics (must assume a specific payload format to parse):
      // "T=44.1,P=1.1"  ->
      // pjon/device44/output/temperature  44.1
      // pjon/device44/output/pressure     1.1
      if (device_start) {
        // Find start of /input/
        const char *start = (const char*)memchr(device_start+1, '/', (const char*)payload-device_start+len-2);
        // Find end of /input/
        if (start) start = (const char*)memchr(start+1, '/', (const char*)payload-start+len-2);
        if (start) { // Get variable name
          uint8_t l = min(start - device_start + len -1, sizeof key -1);
          strncpy(key, start+1, l);
          key[l] = 0; // Null terminate
          translate(key, sizeof key, false);
          l = min(len, sizeof value-1);
          strncpy(value, (const char*)payload, l);
          value[l] = 0; // Null terminate
          String s = key; s += "="; s += value;
          // Package the key=value into a PJON packet
          incoming_packet_size = PJONTools::compose_packet(receiver_id, bus_id, receiver_id,
            bus_id, packet_buffer, s.c_str(), s.length()+1, header);
        }
      }
      return;
      #endif
      #if (MQTTT_MODE == MQTTT_MODE_MIRROR_DIRECT)
      // Package the payload as it is, into a PJON packet
      incoming_packet_size = PJONTools::compose_packet(receiver_id, bus_id, receiver_id,
        bus_id, packet_buffer, payload, len, header);
      #endif
    }

public:
    ReconnectingMqttClient mqttclient;
    bool retain = false; // Leave message in broker for clients to receive at connect
    uint8_t qos = 0; // Set this to 1 to have guaranteed delivery
    String topic = "pjon"; // e.g. "pjon" without trailing slash
    uint8_t my_id = PJON_NOT_ASSIGNED;
    uint8_t bus_id[4] = {0,0,0,0};
    uint8_t header = 0;
    bool lowercase_topics = true;
    bool subscribe_all = false; // Read input from all devices or just my own topic?

    void set_config(uint8_t id, const uint8_t bus_id[4], uint8_t header) {
      my_id = id; 
      if (bus_id != NULL) memcpy(this->bus_id, bus_id, 4);
      this->header = header;
    }
    void set_qos(uint8_t qos) { this->qos = qos; }
    void set_retain(bool retain) { this->retain = retain; }
    void set_topic(const char *topic) { this->topic = topic; }
    

    /* Subscribe to input from all devices, not only this device?
       This is needed to use router mode in PJON.
    */    
    
    void set_subscribe_all(bool yes) { subscribe_all = yes; }


    /* Set the broker's ip, the port used and the topic */

    void set_address(
      const uint8_t server_ip[4],
      const uint16_t server_port,
      const char *client_id
    ) {
      mqttclient.set_address(server_ip, server_port, client_id);
    }


    /* Returns the suggested delay related to the attempts passed as parameter: */

    uint32_t back_off(uint8_t attempts) { return 10000; };


    /* Begin method, to be called on initialization */

    bool begin(uint8_t device_id = 0) {
      #ifdef MQTTT_MAC
      PJON_GET_MAC(mac);
      #endif
      my_id = device_id;
      mqttclient.set_receive_callback(static_receiver, this);
      char *p = (char*)packet_buffer;
      strcpy(p, topic.c_str());
      p += strlen(p);
      #ifdef MQTTT_MAC
        // In this mode (MIRROR modes), I are only interested in my own input
        p = add_mac(p); // Adds slash and MAC
      #else
        if (subscribe_all) {
          strcpy(p, "/+"); // Pick up for all devices
          p += 2;
        } else { // For one single device id
          strcpy(p, "/device");
          p += strlen(p);
          p += mqttclient.uint8toa(device_id, p); // Now like pjon/device44
        }
      #endif
      #if (MQTTT_MODE == MQTTT_MODE_MIRROR_TRANSLATE)
      strcat(p, "/input/+");
      #endif
      #if (MQTTT_MODE == MQTTT_MODE_MIRROR_DIRECT)
      strcat(p, "/input"); // Only one input topic
      #endif
      mqttclient.subscribe((const char*)packet_buffer, qos);
      return mqttclient.connect();
    };


    /* Check if the channel is free for transmission */

    bool can_start() { return mqttclient.connect(); };


    /* Returns the maximum number of attempts for each transmission: */

    static uint8_t get_max_attempts() { return 0; };


    /* Returns the recommended receive time for this strategy: */

    static uint16_t get_receive_time() { return MQTTT_RECEIVE_TIME; };


    /* Handle a collision (empty because handled on Ethernet level): */

    void handle_collision() { };


    /* Receive a frame: */

    uint16_t receive_frame(uint8_t *data, uint16_t max_length) {
      if (incoming_packet_size == 0) mqttclient.update();
      if (incoming_packet_size > 0 && incoming_packet_size <= max_length) {
        memcpy(data, packet_buffer, incoming_packet_size);
        uint16_t len = incoming_packet_size;
        incoming_packet_size = 0; // Flag as handled
        return len;
      }
      return PJON_FAIL;
    }


    /* Receive byte response */

    uint16_t receive_response() {
      return last_send_success ? PJON_ACK : PJON_FAIL;
    };


    /* Send byte response to package transmitter */

    void send_response(uint8_t response) { // Empty
    };


    /* Send a frame: */

    void send_frame(uint8_t *data, uint16_t length) {
      // Extract some info from the packet header
      PJONTools::parse_header(data, _packet_info);

      // Compose topic
      uint8_t len = strlen(topic.c_str());
      if (len >= SMCTOPICSIZE) return;
      strcpy(mqttclient.topic_buf(), topic.c_str());
      char *p = &mqttclient.topic_buf()[len];
      #ifdef MQTTT_MAC
        if (p-mqttclient.topic_buf()+7+7 >= SMCTOPICSIZE) return;
        p = add_mac(p);
        strcpy(p, "/output");
        p += strlen(p); // End of /output
      #else
        if (p-mqttclient.topic_buf()+7+3+7 >= SMCTOPICSIZE) return;
        strcpy(p, "/device"); p += 7;
        #if (MQTTT_MODE == MQTTT_MODE_MIRROR_TRANSLATE || MQTTT_MODE == MQTTT_MODE_MIRROR_DIRECT)
        p += mqttclient.uint8toa(_packet_info.tx.id, p);
        strcat(p, "/output"); // Like pjon/device44/output
        p = &p[strlen(p)]; // End of /output
        #else // One of the bus modes, publish to receiver device
        mqttclient.uint8toa(_packet_info.rx.id, p);
        #endif
      #endif
      #if (MQTTT_MODE != MQTTT_MODE_BUS_RAW)
      uint8_t overhead = PJONTools::packet_overhead(_packet_info.header);
      uint8_t crc_size = PJONTools::crc_overhead(_packet_info.header);
      #endif

      // Re-compose packet in other modes than RAW
      #if (MQTTT_MODE == MQTTT_MODE_MIRROR_TRANSLATE)
      // Split into multiple topics (must assume a specific payload format to parse):
      // "T=44.1,P=1.1"  ->
      // pjon/device44/output/temperature  44.1
      // pjon/device44/output/pressure     1.1
      uint8_t send_cnt = 0;
      const char *d = (const char*)&data[overhead - crc_size], *v = d, *c, *e;
      uint16_t plen = length - overhead;
      while (v && (c = find_value_separator(v, d-v+plen))) {
        if (e = (const char *)memchr(v, '=', (uint16_t)(c-v))) {
          uint8_t l = min(e-v, sizeof key-1);
          strncpy(key, v, l); // Complete topic like /pjon/device44/output/temperature
          key[l] = 0;
          l = min(c-e-1, sizeof value-1);
          strncpy(value, e+1, l);
          value[l] = 0;
          if (!translate(key, sizeof key, true))
            if (lowercase_topics) for (char *k=key; *k!=0; k++) *k = tolower(*k);
          if (p-mqttclient.topic_buf()+1+strlen(key) >= SMCTOPICSIZE) return;  
          *p = '/';
          strcpy(p+1, key);
          send_cnt += mqttclient.publish(mqttclient.topic_buf(), (uint8_t*)value, strlen(value), retain, qos);
          v = c-d >= plen ? NULL : c+1;
        }
      }
      last_send_success = send_cnt > 0;
      return; // We have sent multiple smaller packets, just return
      #endif
      #if (MQTTT_MODE == MQTTT_MODE_MIRROR_DIRECT)
      // Post just the payload as it is, to the output topic
      data = &data[overhead - crc_size];
      length -= overhead;
      #endif
      #if (MQTTT_MODE == MQTTT_MODE_BUS_JSON)
      // Must assume that payload is text, unless UUencoding/base64encoding
      // {"to": to_id, "from": from id, "data": "payload"}
      p = (char *) packet_buffer;
      if (6+3+8+3+9+payload_len+2 >= MQTTT_BUFFER_SIZE) return;
      strcpy(p, "{\"to\":"); p += 6;
      p += mqttclient.uint8toa(_packet_info.rx.id, p);
      strcpy(p, ",\"from\":"); p+= 8;
      p += mqttclient.uint8toa(_packet_info.tx.id, p);
      strcpy(p, ",\"data\":\""); p+= 9;
      uint8_t payload_len = length - overhead;
      strncpy(p, (const char*)&data[overhead - crc_size], payload_len); p[payload_len] = 0;
      p += strlen(p);
      strcpy(p, "\"}"); p += 2;
      data = packet_buffer;
      length = ((uint8_t*)p - packet_buffer);
      #endif

      // Publish
      last_send_success = mqttclient.publish(mqttclient.topic_buf(), data, length, retain, qos);
    };

    const char *find_value_separator(const char *value, uint16_t len) {
      // This does the job of a strchr but accepting that null-terminator may be missing
      const char *p = value;
      while (p != NULL && (p-value < len) && *p != ',' && *p != 0) p++;
      return p;
    }
    
     #if (MQTTT_MODE == MQTTT_MODE_MIRROR_TRANSLATE)
     bool add_translation(const char *pjon_key, const char *mqtt_key) {
      if (translation_count >= MQTTT_TRANSLATION_TABLE_SIZE) return false;
      strncpy(pjon_keys[translation_count], pjon_key, MQTTT_KEY_SIZE);
      pjon_keys[translation_count][MQTTT_KEY_SIZE-1] = 0;
      strncpy(mqtt_keys[translation_count], mqtt_key, MQTTT_KEY_SIZE);
      mqtt_keys[translation_count][MQTTT_KEY_SIZE-1] = 0;
      for (char *p=mqtt_keys[translation_count]; *p!=0; p++) *p = tolower(*p);
      translation_count++;
      return true;
    }
    #endif
};