/*
 * Pin Config
 * MOSI -> 13
 * MISO -> 12
 * SCK  -> 14
 * CS  -> 16
 */

#include <ESP8266WiFi.h>
#include <PubSubClient.h>
#include <DHT.h>
#include <SPI.h>
#include <SD.h>

#define DHTPIN 4
#define DHTTYPE DHT11
DHT dht(DHTPIN, DHTTYPE);

// Update these with values suitable for your network.
const char* ssid = "****";
const char* password = "***********";

//Update your mqtt server details
const char* mqtt_server = "m12.cloudmqtt.com";
const char* mqtt_user = "vzvaucdl";
const char* mqtt_pass = "NqNXasG0Fit3";
//

//File to store details in SD card
File myFile;

WiFiClient espClient;
PubSubClient client(espClient);

long lastMsg = 0;
char msg[50];
int value = 0;

String file_temp;

void setup_wifi() {

  delay(10);
  // We start by connecting to a WiFi network
  Serial.println();
  Serial.print("Connecting to ");
  Serial.println(ssid);

  WiFi.begin(ssid, password);

  if (WiFi.status() != WL_CONNECTED) {
    Serial.print("..");
    delay(5000);
  }
  //Serial.println(WiFi.status());
  randomSeed(micros());
  if(WiFi.status() == WL_CONNECTED){
    Serial.println("");
    Serial.println("WiFi connected");
    Serial.println("IP address: ");
    Serial.println(WiFi.localIP());
  }
}

void callback(char* topic, byte* payload, unsigned int length) {
  Serial.print("Message arrived [");
  Serial.print(topic);
  Serial.print("] ");
  for (int i = 0; i < length; i++) {
    Serial.print((char)payload[i]);
  }
  Serial.println();

  // Switch on the LED if an 1 was received as first character
  if ((char)payload[0] == '1') {
    digitalWrite(BUILTIN_LED, LOW);   // Turn the LED on (Note that LOW is the voltage level
    // but actually the LED is on; this is because
    // it is acive low on the ESP-01)
  } else {
    digitalWrite(BUILTIN_LED, HIGH);  // Turn the LED off by making the voltage HIGH
  }

}

void reconnect() {
  // Loop until we're reconnected
  while (!client.connected()) {
    Serial.print("Attempting MQTT connection...");
    // Create a random client ID
    String clientId = "ESP8266Client";
    //clientId += String(random(0xffff), HEX);
    // Attempt to connect
    if (client.connect("ESP8266", mqtt_user, mqtt_pass)) {
      Serial.println("connected");
      // Once connected, publish an announcement...
      // ... and resubscribe
      client.subscribe("Temperature");
    } else {
      Serial.print("failed, rc=");
      Serial.print(client.state());
      Serial.println(" try again in 5 seconds");
      // Wait 5 seconds before retrying
      delay(5000);
    }
  }
}

void setup() {
  pinMode(BUILTIN_LED, OUTPUT);     // Initialize the BUILTIN_LED pin as an output
  Serial.begin(9600);
  setup_wifi();
  client.setServer(mqtt_server, 12119);
  client.setCallback(callback);
  if (!SD.begin(16)) {
    Serial.println("SD card initialization failed!");
    return;
  }
  Serial.println("SD card initialization done.");
  SD.remove("temp.txt");
}

void loop() {

 //Reading the sensor value for intervals of 2s
  long now = millis();
  if (now - lastMsg > 2000) {
    lastMsg = now;
    int c = dht.readTemperature();

    Serial.print("Temp: ");
    Serial.print(c);
    Serial.print("\t");
    sprintf (msg, "Temp: %d", c);

   //Checking for WiFi connection
   if(WiFi.status() == WL_CONNECTED){
      if (!client.connected()) {
          reconnect();
      }
      client.loop();
   //Checking for any previous data in the SD card and publishing them to server
      if(SD.exists("temp.txt")){
        int i=0;
        myFile = SD.open("temp.txt", FILE_WRITE);
        myFile.println("");
        myFile.close();
        delay(100);
        myFile = SD.open("temp.txt");

        if(myFile.available()){
          String line = myFile.readStringUntil('\n');
          for(i=0;i<line.length();i+=2){
            String t = line.substring(i,i+2);
            sprintf(msg, "Temp: %s", t.c_str());
            client.publish("Temperature", msg);
          }
        }
        client.publish("Temperature", msg);
        myFile.close();
        SD.remove("temp.txt");
      }
    //Publishing realtime data while WiFi is connected
      Serial.print("Publish message: ");
      Serial.println(msg);
      client.publish("Temperature", msg);

    }
   //Writing to SD card when no WiFi connection is present
    else{
      myFile = SD.open("temp.txt", FILE_WRITE);
      if (myFile) {
        Serial.print("Writing to temp.txt...");
        myFile.print(c);
        // close the file:
        myFile.close();
        Serial.println("done.");
        setup_wifi();
      }
    }
  }
}