// Copyright (c) Microsoft Corporation. All rights reserved.
// SPDX-License-Identifier: MIT

/*
 * This is an Arduino-based Azure IoT Hub sample for ESPRESSIF ESP32 boards.
 * It uses our Azure Embedded SDK for C to help interact with Azure IoT.
 * For reference, please visit https://github.com/azure/azure-sdk-for-c.
 *
 * To connect and work with Azure IoT Hub you need an MQTT client, connecting, subscribing
 * and publishing to specific topics to use the messaging features of the hub.
 * Our azure-sdk-for-c is an MQTT client support library, helping composing and parsing the
 * MQTT topic names and messages exchanged with the Azure IoT Hub.
 *
 * This sample performs the following tasks:
 * - Synchronize the device clock with a NTP server;
 * - Initialize our "az_iot_hub_client" (struct for data, part of our azure-sdk-for-c);
 * - Initialize the MQTT client (here we use ESPRESSIF's esp_mqtt_client, which also handle the tcp
 * connection and TLS);
 * - Connect the MQTT client (using server-certificate validation, SAS-tokens for client
 * authentication);
 * - Periodically send telemetry data to the Azure IoT Hub.
 *
 * To properly connect to your Azure IoT Hub, please fill the information in the `iot_configs.h`
 * file.
 */

// C99 libraries
#include <cstdlib>
#include <string.h>
#include <time.h>

// Libraries for MQTT client and WiFi connection
#include <WiFi.h>
#include <mqtt_client.h>

// Azure IoT SDK for C includes
#include <az_core.h>
#include <az_iot.h>
#include <azure_ca.h>

// DHT sensor library
#include <Adafruit_Sensor.h>
#include <DHT.h>
#include <DHT_U.h>

// Additional sample headers
#include "AzIoTSasToken.h"
#include "SerialLogger.h"
#include "iot_configs.h"

// When developing for your own Arduino-based platform,
// please follow the format '(ard;<platform>)'.
#define AZURE_SDK_CLIENT_USER_AGENT "c%2F" AZ_SDK_VERSION_STRING "(ard;esp32)"

// Utility macros and defines
#define sizeofarray(a) (sizeof(a) / sizeof(a[0]))
#define NTP_SERVERS "pool.ntp.org", "time.nist.gov"
#define MQTT_QOS1 1
#define DO_NOT_RETAIN_MSG 0
#define SAS_TOKEN_DURATION_IN_MINUTES 60
#define UNIX_TIME_NOV_13_2017 1510592825

#define PST_TIME_ZONE -8
#define PST_TIME_ZONE_DAYLIGHT_SAVINGS_DIFF 1

#define GMT_OFFSET_SECS (PST_TIME_ZONE * 3600)
#define GMT_OFFSET_SECS_DST ((PST_TIME_ZONE + PST_TIME_ZONE_DAYLIGHT_SAVINGS_DIFF) * 3600)

// Translate iot_configs.h defines into variables used by the sample
static const char* ssid = IOT_CONFIG_WIFI_SSID;
static const char* password = IOT_CONFIG_WIFI_PASSWORD;
static const char* host = IOT_CONFIG_IOTHUB_FQDN;
static const char* mqtt_broker_uri = "mqtts://" IOT_CONFIG_IOTHUB_FQDN;
static const char* device_id = IOT_CONFIG_DEVICE_ID;
static const int mqtt_port = AZ_IOT_DEFAULT_MQTT_CONNECT_PORT;

// Memory allocated for the sample's variables and structures.
static esp_mqtt_client_handle_t mqtt_client;
static az_iot_hub_client client;

static char mqtt_client_id[128];
static char mqtt_username[128];
static char mqtt_password[200];
static uint8_t sas_signature_buffer[256];
static unsigned long next_telemetry_send_time_ms = 0;
static char telemetry_topic[128];
static uint32_t telemetry_send_count = 0;
static String telemetry_payload = "{}";

#define INCOMING_DATA_BUFFER_SIZE 128
static char incoming_data[INCOMING_DATA_BUFFER_SIZE];

// DHT sensor configuration
#define DHTPIN 4        // Digital pin connected to the DHT sensor
#define DHTTYPE DHT22   // DHT 22 (AM2302)

// Create the DHT object
DHT dht(DHTPIN, DHTTYPE);

// Auxiliary functions
#ifndef IOT_CONFIG_USE_X509_CERT
static AzIoTSasToken sasToken(
    &client,
    AZ_SPAN_FROM_STR(IOT_CONFIG_DEVICE_KEY),
    AZ_SPAN_FROM_BUFFER(sas_signature_buffer),
    AZ_SPAN_FROM_BUFFER(mqtt_password));
#endif // IOT_CONFIG_USE_X509_CERT

static void connectToWiFi()
{
  Logger.Info("Connecting to WIFI SSID " + String(ssid));

  WiFi.mode(WIFI_STA);
  WiFi.disconnect();
  delay(100);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED)
  {
    delay(500);
    Serial.print(".");
  }

  Serial.println("");

  Logger.Info("WiFi connected, IP address: " + WiFi.localIP().toString());
}

static void initializeTime()
{
  Logger.Info("Setting time using SNTP");

  configTime(GMT_OFFSET_SECS, GMT_OFFSET_SECS_DST, NTP_SERVERS);
  time_t now = time(NULL);
  while (now < UNIX_TIME_NOV_13_2017)
  {
    delay(500);
    Serial.print(".");
    now = time(nullptr);
  }
  Serial.println("");
  Logger.Info("Time initialized!");
}

void receivedCallback(char* topic, byte* payload, unsigned int length)
{
  Logger.Info("Received [");
  Logger.Info(topic);
  Logger.Info("]: ");
  for (int i = 0; i < length; i++)
  {
    Serial.print((char)payload[i]);
  }
  Serial.println("");
}

#if defined(ESP_ARDUINO_VERSION_MAJOR) && ESP_ARDUINO_VERSION_MAJOR >= 3
static void mqtt_event_handler(void *handler_args, esp_event_base_t base, int32_t event_id, void *event_data)
{
  (void)handler_args;
  (void)base;
  (void)event_id;

  esp_mqtt_event_handle_t event = (esp_mqtt_event_handle_t)event_data;
#else // ESP_ARDUINO_VERSION_MAJOR
static esp_err_t mqtt_event_handler(esp_mqtt_event_handle_t event)
{
#endif // ESP_ARDUINO_VERSION_MAJOR
  switch (event->event_id)
  {
    int i, r;

    case MQTT_EVENT_ERROR:
      Logger.Info("MQTT event MQTT_EVENT_ERROR");
      break;
    case MQTT_EVENT_CONNECTED:
      Logger.Info("MQTT event MQTT_EVENT_CONNECTED");

      r = esp_mqtt_client_subscribe(mqtt_client, AZ_IOT_HUB_CLIENT_C2D_SUBSCRIBE_TOPIC, 1);
      if (r == -1)
      {
        Logger.Error("Could not subscribe for cloud-to-device messages.");
      }
      else
      {
        Logger.Info("Subscribed for cloud-to-device messages; message id:" + String(r));
      }

      break;
    case MQTT_EVENT_DISCONNECTED:
      Logger.Info("MQTT event MQTT_EVENT_DISCONNECTED");
      break;
    case MQTT_EVENT_SUBSCRIBED:
      Logger.Info("MQTT event MQTT_EVENT_SUBSCRIBED");
      break;
    case MQTT_EVENT_UNSUBSCRIBED:
      Logger.Info("MQTT event MQTT_EVENT_UNSUBSCRIBED");
      break;
    case MQTT_EVENT_PUBLISHED:
      Logger.Info("MQTT event MQTT_EVENT_PUBLISHED");
      break;
    case MQTT_EVENT_DATA:
      Logger.Info("MQTT event MQTT_EVENT_DATA");

      for (i = 0; i < (INCOMING_DATA_BUFFER_SIZE - 1) && i < event->topic_len; i++)
      {
        incoming_data[i] = event->topic[i];
      }
      incoming_data[i] = '\0';
      Logger.Info("Topic: " + String(incoming_data));

      for (i = 0; i < (INCOMING_DATA_BUFFER_SIZE - 1) && i < event->data_len; i++)
      {
        incoming_data[i] = event->data[i];
      }
      incoming_data[i] = '\0';
      Logger.Info("Data: " + String(incoming_data));

      break;
    case MQTT_EVENT_BEFORE_CONNECT:
      Logger.Info("MQTT event MQTT_EVENT_BEFORE_CONNECT");
      break;
    default:
      Logger.Error("MQTT event UNKNOWN");
      break;
  }

#if defined(ESP_ARDUINO_VERSION_MAJOR) && ESP_ARDUINO_VERSION_MAJOR >= 3
#else // ESP_ARDUINO_VERSION_MAJOR
  return ESP_OK;
#endif // ESP_ARDUINO_VERSION_MAJOR
}

static void initializeIoTHubClient()
{
  az_iot_hub_client_options options = az_iot_hub_client_options_default();
  options.user_agent = AZ_SPAN_FROM_STR(AZURE_SDK_CLIENT_USER_AGENT);

  if (az_result_failed(az_iot_hub_client_init(
          &client,
          az_span_create((uint8_t*)host, strlen(host)),
          az_span_create((uint8_t*)device_id, strlen(device_id)),
          &options)))
  {
    Logger.Error("Failed initializing Azure IoT Hub client");
    return;
  }

  size_t client_id_length;
  if (az_result_failed(az_iot_hub_client_get_client_id(
          &client, mqtt_client_id, sizeof(mqtt_client_id) - 1, &client_id_length)))
  {
    Logger.Error("Failed getting client id");
    return;
  }
  mqtt_client_id[client_id_length] = '\0';

  if (az_result_failed(az_iot_hub_client_get_user_name(
          &client, mqtt_username, sizeof(mqtt_username) - 1, NULL)))
  {
    Logger.Error("Failed to get MQTT clientId, return code");
    return;
  }
}

static void initializeMqttClient()
{
#ifndef IOT_CONFIG_USE_X509_CERT
  if (sasToken.Generate(SAS_TOKEN_DURATION_IN_MINUTES) != 0)
  {
    Logger.Error("Failed generating SAS token");
    return 1;
  }
#endif

  esp_mqtt_client_config_t mqtt_config;
  memset(&mqtt_config, 0, sizeof(mqtt_config));

#if defined(ESP_ARDUINO_VERSION_MAJOR) && ESP_ARDUINO_VERSION_MAJOR >= 3
    mqtt_config.broker.address.uri = mqtt_broker_uri;
    mqtt_config.broker.address.port = mqtt_port;
    mqtt_config.credentials.client_id = mqtt_client_id;
    mqtt_config.credentials.username = mqtt_username;

  #ifdef IOT_CONFIG_USE_X509_CERT
    LogInfo("MQTT client using X509 Certificate authentication");
    mqtt_config.credentials.authentication.certificate = IOT_CONFIG_DEVICE_CERT;
    mqtt_config.credentials.authentication.certificate_len = (size_t)sizeof(IOT_CONFIG_DEVICE_CERT);
    mqtt_config.credentials.authentication.key = IOT_CONFIG_DEVICE_CERT_PRIVATE_KEY;
    mqtt_config.credentials.authentication.key_len = (size_t)sizeof(IOT_CONFIG_DEVICE_CERT_PRIVATE_KEY);
  #else // Using SAS key
    mqtt_config.credentials.authentication.password = (const char*)az_span_ptr(sasToken.Get());
  #endif

    mqtt_config.session.keepalive = 30;
    mqtt_config.session.disable_clean_session = 0;
    mqtt_config.network.disable_auto_reconnect = false;
    mqtt_config.broker.verification.certificate = (const char*)ca_pem;
    mqtt_config.broker.verification.certificate_len = (size_t)ca_pem_len;
#else // ESP_ARDUINO_VERSION_MAJOR  
  mqtt_config.uri = mqtt_broker_uri;
  mqtt_config.port = mqtt_port;
  mqtt_config.client_id = mqtt_client_id;
  mqtt_config.username = mqtt_username;

#ifdef IOT_CONFIG_USE_X509_CERT
  Logger.Info("MQTT client using X509 Certificate authentication");
  mqtt_config.client_cert_pem = IOT_CONFIG_DEVICE_CERT;
  mqtt_config.client_key_pem = IOT_CONFIG_DEVICE_CERT_PRIVATE_KEY;
#else // Using SAS key
  mqtt_config.password = (const char*)az_span_ptr(sasToken.Get());
#endif

  mqtt_config.keepalive = 30;
  mqtt_config.disable_clean_session = 0;
  mqtt_config.disable_auto_reconnect = false;
  mqtt_config.event_handle = mqtt_event_handler;
  mqtt_config.user_context = NULL;
  mqtt_config.cert_pem = (const char*)ca_pem;
#endif // ESP_ARDUINO_VERSION_MAJOR

  mqtt_client = esp_mqtt_client_init(&mqtt_config);

  if (mqtt_client == NULL)
  {
    Logger.Error("Failed creating mqtt client");
    return 1;
  }

#if defined(ESP_ARDUINO_VERSION_MAJOR) && ESP_ARDUINO_VERSION_MAJOR >= 3
    esp_mqtt_client_register_event(mqtt_client, MQTT_EVENT_ANY, mqtt_event_handler, NULL);
#endif // ESP_ARDUINO_VERSION_MAJOR

  esp_err_t start_result = esp_mqtt_client_start(mqtt_client);

  if (start_result != ESP_OK)
  {
    Logger.Error("Could not start mqtt client; error code:" + start_result);
    return 1;
  }
  else
  {
    Logger.Info("MQTT client started");
    return 0;
  }
}

static void establishConnection()
{
  connectToWiFi();
  initializeTime();
  initializeIoTHubClient();
  initializeMqttClient();

  Logger.Info("MQTT client connecting to Azure IoT Hub...");
  if (esp_mqtt_client_start(mqtt_client) != ESP_OK)
  {
    Logger.Error("Could not start mqtt client; retrying...");
    delay(5000);
    abort();
  }
  else
  {
    Logger.Info("MQTT client started");
  }

#ifndef IOT_CONFIG_USE_X509_CERT
  if (sasToken.Generate(SAS_TOKEN_DURATION_IN_MINUTES) != 0)
  {
    Logger.Error("Failed generating SAS token");
    return;
  }
#endif // IOT_CONFIG_USE_X509_CERT
}

static void generateTelemetryPayload()
{
  // Read temperature and humidity from DHT22
  float humidity = dht.readHumidity();
  float temperature = dht.readTemperature();

  // Check if any reads failed and exit early (to try again).
  if (isnan(humidity) || isnan(temperature))
  {
    Logger.Error("Failed to read from DHT sensor!");
    return;
  }

  // Create telemetry payload
  telemetry_payload = "{\"temperature\":";
  telemetry_payload += String(temperature);
  telemetry_payload += ",\"humidity\":";
  telemetry_payload += String(humidity);
  telemetry_payload += "}";
}

static void sendTelemetry()
{
  if (millis() < next_telemetry_send_time_ms)
  {
    return;
  }
  next_telemetry_send_time_ms = millis() + IOT_CONFIG_TELEMETRY_FREQUENCY_MILLISECS;

  generateTelemetryPayload();

  if (az_result_failed(az_iot_hub_client_telemetry_get_publish_topic(
          &client, NULL, telemetry_topic, sizeof(telemetry_topic), NULL)))
  {
    Logger.Error("Failed az_iot_hub_client_telemetry_get_publish_topic");
    return;
  }

  Logger.Info("Sending telemetry ...");
  Logger.Info(telemetry_payload);

  if (esp_mqtt_client_publish(
          mqtt_client,
          telemetry_topic,
          telemetry_payload.c_str(),
          telemetry_payload.length(),
          MQTT_QOS1,
          DO_NOT_RETAIN_MSG) == 0)
  {
    Logger.Error("Failed publishing");
  }
  else
  {
    telemetry_send_count++;
    Logger.Info("Message sent, count: " + String(telemetry_send_count));
  }
}

void setup()
{
  Serial.begin(115200);
  delay(2000);
  Logger.Info("Setup starting...");

  // Initialize the DHT22 sensor
  dht.begin();

  establishConnection();
  Logger.Info("Setup done");
}

void loop()
{
  if (WiFi.status() != WL_CONNECTED)
  {
    Logger.Error("WiFi disconnected; reconnecting...");
    connectToWiFi();
  }

#ifndef IOT_CONFIG_USE_X509_CERT
  if (sasToken.IsExpired())
  {
    Logger.Info("SAS token expired; reconnecting MQTT client...");
    esp_mqtt_client_disconnect(mqtt_client);
    if (sasToken.Generate(SAS_TOKEN_DURATION_IN_MINUTES) != 0)
    {
      Logger.Error("Failed generating SAS token");
      return;
    }
    if (esp_mqtt_client_reconnect(mqtt_client) != ESP_OK)
    {
      Logger.Error("Reconnecting MQTT client failed");
      return;
    }
  }
#endif // IOT_CONFIG_USE_X509_CERT

  sendTelemetry();
}