/* ============================================================
   Factory Floor Temperature Alert System
   -----------------------------------------------------------
   Author : Sumit
   Date   : 03 September 2026
   Board  : ESP32-S2 (Wokwi: board-esp32-s2-devkitm-1)

   Description:
   Reads ambient temperature from a DHT22 sensor and drives a
   common-cathode RGB LED to give an at-a-glance colour status
   of the factory floor temperature:

       COLD  ( < 20 C )        -> Deep Blue
       WARM  ( 20 C to 40 C )  -> Amber
       HOT   ( >= 40 C )       -> Red

   Temperature and the active colour state are printed to the
   Serial Monitor once every second.
   ============================================================ */

#include "DHTesp.h"

// ---------- Pin assignments ----------
// DHT22 data pin. GPIO15 is a free, non-strapping digital pin
// on the ESP32-S2 DevKitM-1, safe to use for a simple digital
// sensor bus.
const int DHT_PIN = 15;

// RGB LED pins (common cathode). GPIO4, GPIO5 and GPIO6 are
// all capable of PWM output via the LEDC peripheral, are not
// used for flashing/boot strapping, and sit next to each other
// on the header for tidy wiring.
const int LED_R_PIN = 4;
const int LED_G_PIN = 5;
const int LED_B_PIN = 6;

// ---------- Temperature thresholds (deg C) ----------
const float COLD_WARM_BOUNDARY = 20.0; // below this  -> COLD
const float WARM_HOT_BOUNDARY  = 40.0; // at/above this -> HOT

// ---------- Colour definitions (0-255 per channel) ----------
// Deep Blue : a dark, saturated blue (not a bright/light blue)
const int COLOR_COLD[3] = {0,   0,   139};
// Amber : warm orange-yellow, visually distinct from red
const int COLOR_WARM[3] = {255, 191, 0};
// Red : full red, no green/blue
const int COLOR_HOT[3]  = {255, 0,   0};

// ---------- Timing ----------
const unsigned long PRINT_INTERVAL_MS = 1000; // 1 reading/print per second
unsigned long lastPrintTime = 0;

DHTesp dhtSensor;

// Sets the RGB LED to a given colour using PWM (analogWrite).
void setLedColor(const int color[3]) {
  analogWrite(LED_R_PIN, color[0]);
  analogWrite(LED_G_PIN, color[1]);
  analogWrite(LED_B_PIN, color[2]);
}

// Classifies temperature into one of three states and drives
// the LED accordingly. Returns a human-readable label for
// Serial output.
const char* applyTemperatureState(float tempC) {
  if (tempC < COLD_WARM_BOUNDARY) {
    // Strictly below 20.0 C -> COLD
    setLedColor(COLOR_COLD);
    return "COLD (Deep Blue)";
  } else if (tempC < WARM_HOT_BOUNDARY) {
    // 20.0 C <= temp < 40.0 C -> WARM
    // Boundary rule: exactly 20.0 C is treated as WARM because
    // the spec defines the WARM band as "20C to 40C" (inclusive
    // lower bound), while COLD is defined as strictly "below 20C".
    setLedColor(COLOR_WARM);
    return "WARM (Amber)";
  } else {
    // temp >= 40.0 C -> HOT
    // Boundary rule: exactly 40.0 C is treated as HOT because the
    // spec explicitly states "40C and above" (inclusive lower
    // bound) for the HOT band.
    setLedColor(COLOR_HOT);
    return "HOT (Red)";
  }
}

void setup() {
  Serial.begin(115200);
  delay(500);

  pinMode(LED_R_PIN, OUTPUT);
  pinMode(LED_G_PIN, OUTPUT);
  pinMode(LED_B_PIN, OUTPUT);

  dhtSensor.setup(DHT_PIN, DHTesp::DHT22);

  Serial.println("=== Factory Floor Temperature Alert System ===");
  Serial.println("COLD < 20C | WARM 20-40C | HOT >= 40C");
  Serial.println("------------------------------------------------");
}

void loop() {
  unsigned long now = millis();

  if (now - lastPrintTime >= PRINT_INTERVAL_MS) {
    lastPrintTime = now;

    TempAndHumidity data = dhtSensor.getTempAndHumidity();
    float temperature = data.temperature;

    // Guard against a bad/NaN reading (e.g. sensor not ready yet)
    if (isnan(temperature)) {
      Serial.println("Sensor read failed, skipping this cycle.");
      return;
    }

    const char* state = applyTemperatureState(temperature);

    Serial.print("Temperature: ");
    Serial.print(temperature, 1);
    Serial.print(" C  |  State: ");
    Serial.println(state);
  }
}