#include <Arduino.h>
#include <TM1637Display.h>
#include "DHT.h"

// Pin Definitions
#define DHTPIN 2          // DHT22 Data Pin
#define DHTTYPE DHT22     // Using high-precision DHT22 sensor
#define CLK_PIN 3         // TM1637 Clock Pin
#define DIO_PIN 8         // TM1637 Data Pin
#define RELAY_PIN 4       // Relay/LED Control Pin (Active-LOW Configuration)

#define BTN_SET 5         // Menu Mode Toggle Button
#define BTN_UP 6          // Target Temperature Increment Button
#define BTN_DOWN 7        // Target Temperature Decrement Button

// Thermostat Control System Variables (Celsius)
float targetTemp = 5.0;   // Default baseline cooling target
const float HYSTERESIS = 1.5; // Preventing short-cycling buffer window
bool isCooling = false;
bool inSettingMode = false;

// Initialize Electronic Hardware Profiles
DHT dht(DHTPIN, DHTTYPE);
TM1637Display display(CLK_PIN, DIO_PIN);

// Custom 7-Segment structural bits mapping out the "°C" symbol layout
const uint8_t CELSIUS_SUFFIX[] = {
  SEG_A | SEG_B | SEG_G | SEG_F, // Degree circle symbol (°)
  SEG_A | SEG_D | SEG_E | SEG_F  // Alpha character capital 'C'
};

void setup() {
  Serial.begin(9600); // Initializing tracking data window
  dht.begin();
  display.setBrightness(0x0f); // Fire up segments to maximum brightness level
  
  // Define Output Controls
  pinMode(RELAY_PIN, OUTPUT);
  digitalWrite(RELAY_PIN, HIGH); // Safety Rule: Force relay loop OFF at system initialization
  
  // Set up button ports using the internal Pull-Up network loops
  pinMode(BTN_SET, INPUT_PULLUP);
  pinMode(BTN_UP, INPUT_PULLUP);
  pinMode(BTN_DOWN, INPUT_PULLUP);
  
  // Initialization flash display confirmation sequence "8888"
  display.showNumberDec(8888, false);
  delay(600);
  display.clear();
  Serial.println("System Initialized Successfully.");
}

void loop() {
  // Read User Input Profile: Detect if SET switch breaks ground
  if (digitalRead(BTN_SET) == LOW) {
    delay(200); // Debounce delay path to ignore physical switch bounce noise
    inSettingMode = !inSettingMode; // Swap working application state matrix
    display.clear();
    while(digitalRead(BTN_SET) == LOW); // Wait for user to completely let go of the button
  }

  if (inSettingMode) {
    adjustSettingsMode();
  } else {
    runThermostatMode();
  }
}

void adjustSettingsMode() {
  // Read Increment Input Channel
  if (digitalRead(BTN_UP) == LOW) {
    delay(150); // Fast debounce track
    targetTemp += 0.5; // Increment target value by halves
    if (targetTemp > 30.0) targetTemp = 30.0; // Enforce maximum safe hot threshold limit
  }
  
  // Read Decrement Input Channel
  if (digitalRead(BTN_DOWN) == LOW) {
    delay(150); // Fast debounce track
    targetTemp -= 0.5; // Decrement target value by halves
    if (targetTemp < -5.0) targetTemp = -5.0; // Enforce minimum safe sub-zero structural freezing floor
  }
  
  // Active UI Display Rendering during adjustment
  int displayTargetInt = (int)targetTemp;
  display.showNumberDec(displayTargetInt, false, 2, 0); // Plot numeric value on the first 2 digits
  display.setSegments(CELSIUS_SUFFIX, 2, 2);           // Anchor the "°C" graphics to the remaining 2 digits
}

void runThermostatMode() {
  static unsigned long lastReadingTimestamp = 0;
  static float monitoredTemp = 0.0;

  // Query sensor node non-blockingly every 2000 milliseconds to avoid blocking logic loops
  if (millis() - lastReadingTimestamp >= 2000) {
    monitoredTemp = dht.readTemperature();
    lastReadingTimestamp = millis();
    
    // Print data outputs continuously to the Serial Monitor stream log
    Serial.print("Internal Temp: ");
    Serial.print(monitoredTemp, 1);
    Serial.print(" C | Current Cooling Target Set Point: ");
    Serial.print(targetTemp, 1);
    Serial.println(" C");
  }

  // Handle Unexpected Sensor Outages Safely
  if (isnan(monitoredTemp)) {
    // Generate an immediate "Err" alphabetic readout sequence across 7-segment pins
    uint8_t errorMask[] = { SEG_A|SEG_D|SEG_E|SEG_F|SEG_G, SEG_E|SEG_G, SEG_E|SEG_G }; // E r r
    display.setSegments(errorMask, 3, 0);
    digitalWrite(RELAY_PIN, HIGH); // SYSTEM CRITICAL TRIP OVERRIDE: Kill heavy power to the Peltier element immediately
    return;
  }

  // Standard Operation Mode Display Output
  int roundTemp = (int)monitoredTemp;
  display.showNumberDec(roundTemp, false, 2, 0); // Output live value to display left side digits
  display.setSegments(CELSIUS_SUFFIX, 2, 2);      // Draw "°C" suffix to right side digits

  // --- Automated Thermostat Temperature Control Calculations ---
  if (!isCooling && monitoredTemp > (targetTemp + HYSTERESIS)) {
    isCooling = true;
    digitalWrite(RELAY_PIN, LOW); // Active-LOW Profile: Drive low to snap relay closed and activate cooling
    Serial.println("[!] Fridge Status Shift: TARGET BREACHED. COOLING MODE ACTIVATED.");
  } 
  else if (isCooling && monitoredTemp <= (targetTemp - HYSTERESIS)) {
    isCooling = false;
    digitalWrite(RELAY_PIN, HIGH); // Active-LOW Profile: Drive high to drop relay contact open and deactivate cooling
    Serial.println("[!] Fridge Status Shift: SATIATED COLD ENVIRONMENT. RELAY SHUTDOWN IDLE STAGE.");
  }
}