// https://github.com/adafruit/DHT-sensor-library https://github.com/adafruit/Adafruit_Sensor

// NTC module = 1k ntc thermistor in series w/ 10k resistor.

#include "DHT.h"

#define USE_NTC_SENSOR

/*
 Trigger the relay if the temperature reaches either
  < TEMP_MIN or
  > TEMP_MAX
*/
#define TEMP_MIN 0
#define TEMP_MAX 60

/// Pin configuration
#define DHT_PIN  (2)
#define NTC_PIN  (0)
#define RELAY_PIN (4)
//

namespace App
{
  DHT* dhtSensor{nullptr};
  float lastTemp{0.0f};
  
  void Setup()
  {
    pinMode(RELAY_PIN, OUTPUT);  

    #ifndef USE_NTC_SENSOR
    dhtSensor = new DHT(DHT_PIN, DHT22);
    dhtSensor->begin();
    #endif
  }

  /**
    * Reads the current temeperature from a NTC or DHT sensor.
    *
    * @param float& current temperature
    * @return bool operation successful?
  */
  bool ReadTemperature(float* out)
  {  
    if(dhtSensor != nullptr)
    {
      *out = dhtSensor->readTemperature();
    }
    else
    {
      const float BETA = 3950; // should match the Beta Coefficient of the thermistor
      *out = (1 / (log(1 / (1023. / analogRead(NTC_PIN) - 1)) / BETA + 1.0 / 298.15) - 273.15);
    }

    return !isnan(*out);
  }

  /**
    * Toggles the relay.
    *
    * @param bool state true(open)/false(closed)
    * @return void
  */
  void ToggleRelay(bool state)
  {
    digitalWrite(RELAY_PIN, state?HIGH:LOW);
  }

  bool GetRelayState()
  {
    return (digitalRead(RELAY_PIN)==HIGH)?true:false;
  }

  void Loop()
  {
    delay(200);
    static float temp{0.0f};
    if(!ReadTemperature(&temp))
      Serial.println("Failed to read temperature!"); // handle multiplie failed reads?

    Serial.print(F("Temperature: "));
    Serial.println(temp);

    if(temp < TEMP_MIN || temp > TEMP_MAX)
      ToggleRelay(true);
    else if (GetRelayState())
      ToggleRelay(false);
  }
}

void setup() {
  Serial.begin(9600);
  App::Setup();
}

void loop() {
  App::Loop();
}